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User manual v1.8

1. active marker Place Active Marker Min seach TF 3dB band 1321 6800 e MHz O ne Display Markers TF 6 dB band 2 em ro Use search facility to find max or min value and 3 6 dB bandwidth Figure 5 4 The Markers Set Up form is used to display measurement markers Reference Normal Active Fixed Left clickand drag to move a marker l l l Note Channel on which marker is beco mes _ _ acta Seat active channel Right Click on any marker on the active channel Note Any marker except a o _ iol x fixed marker can be moved to a new position by left clicking on it and draggin g T Trace Markers Adjust Markers Freg MHz Mode Trace Marker 1 1681 32000 uN Date Marker 2 1276 72500 ie Date Marker 3 1426 57500 a Data Marker 4 Fin Memory Apply Freq Figure 5 5 The marker type can be changed by right clicking on any marker on the active channel Note that only the reference marker can be fixed The peak minimum search facility provides a means of placing additional markers to indicate the 3 or 6 dB bandwidth If either the 3 dB or 6 dB band box are selected then clicking the Find button will place markers 2 and 3 on the frequency points either LA19 13 02 DW96659 iss 1 8 33 of 74 side of marker which are 3 dB or 6 dB relative to it Note that for best accuracy a sufficient number of sweep points should be used This will ensure a fine enough resolut
2. networks being available This data must be in the form of 2 port s parameter files in Touchstone format 5 5 Saving Data Measured data can be saved to a file by selecting Save Measurements from the drop down menu under File on the main window Various formats are available as shown In all cases frequency is saved in megahertz Note that only the Touchstone format can later be read back into the instrument s memory trace Et Save Measurements 5 x select Format C LogMag FPhaze Go Gal C Mag Phase Comment will be added to ost F522 C Real Imag the first line of saved file when Touchstone Touchstone format is used E ae Memory Touchstone comment SELP 1870 Check here to save data after Gave El applying the memory math function See 5 1 4 Figure 5 30 The Save Measurements window is used to save data Note For true compatibility with the Touchstone format only 1 port or full 2 port S parameters should be saved For example selecting S11 and S21 but not S12 and S22 is not Touchstone compliant If required the data can be saved with the memory math function applied as described earlier in section 5 1 4 In order to do this check the box Apply Memory Math Note that the memory math display function on the main window see Fig 3 1 must be set otherwise the Apply Memory Math check box will be disabled When saving data in Touchstone format ensure that you p
3. partition Windows 2000 or XP 316 x 140 x 319 mm 6 0 kg 5C to 35 C 10 C to 60 C 80 max non condensing AC 90 250 V 30 VA max 2 x 20 mm F1 6A quick blow IEC127 Windows is a Trade Mark of Microsoft Corporation LA19 13 02 DW96659 iss 1 8 71 of 74 8 TROUBLESHOOTING GUIDE WARNING No user serviceable parts in this instrument Refer servicing and repairs to a trained person Symptom Possible Cause Instrument does not power up e Power not applied e Check mains connection e Blown fuse e Check fuses UI software unable to communicate e Wrong serial cable e See Section 4 3 with the instrument e Link interrupted e Reset instrument back panel e PC does not support button and re start UI software RS232 or data rate Fig 8 1 e Use USB link See Section 4 4 for details Instrument sweeping but display not e Data link interrupted e Reset instrument back panel refreshing button and re start UI software Display freezes e PC crash e Ensure PC s video driver is the latest version consult your PC supplier e Problem with the PC s operating system consult your PC supplier Last Calibration not found message e C LA19 13 02 e Ensure that the instrument s on power up directory deleted or directory is not deleted after using corrupted the instrument High instrument temperature gt 50 C showing on the status panel e Clear grilles Ensure that a gap is always left under the instrum
4. 1 of the VNA as indicated in Fig 5 14 If the DUT can only be connected to the VNA using a cable then the VNA should be calibrated at the end of the cable for best results DUT Figure 5 14 Connect device under test to Port to carry out S11 measurements Displaying the results The measurement result can be displayed by selecting the S11 parameter and an appropriate display graph as described in Section 5 1 1 Note that the measured phase is relative to the calibration reference plane as discussed in Section 5 4 The reference plane can be shifted at any time from the Enhancement window Note that changes to the reference plane only take place when the instrument is sweeping 5 3 2 Insertion loss gain To carry out insertion loss measurements S21 the VNA must be calibrated either S21 calibration only both S11 and S21 or full 12 term The device to be tested DUT is then connected between Ports 1 and 2 of the VNA as indicated in Fig 5 15 For best results the arrangement shown on the left hand side of Fig 5 15 should be used whenever possible When using an S11 821 calibration this will minimise errors introduced by the load return loss On the other hand when using a 12 term calibration this will minimise repeatability cable flexing errors associated with the connecting cables LA19 13 02 DW96659 iss 1 8 45 of 74 f Port 1 N RF cable DUT Figure 5 15 Connect DUT between Ports 1 and 2 to carry o
5. 36 Insertable devices 24 41 Insertion loss 44 Interpolation 44 Labeling graphics 56 Level 33 Limit lines 36 Load match 67 Marker 31 3 dB bandwidth 32 33 6 dB bandwidth 32 33 active 32 fixed 32 74 of 74 Index normal 32 reference 32 Set up 32 Search 32 Maximum hold 35 Measurement uncertainty 63 Memory 36 Minimum hold 35 Normalization 53 Non insertable devices 24 41 Operation 29 PC 21 Peak hold 35 Performance verification 62 Phase 13 Reference plane extension 33 52 Reflection parameters 12 Resolution bandwidth 67 Return loss 44 Reverse measurements 51 Routine maintenance 65 RS232 21 RTS CTS 22 Safety 7 65 Serial interface 22 Signal generator 57 Single conversion 5 Smith chart 11 Smoothing 33 SOLT 12 Source match 67 S parameters 9 Specification 66 Start Stop 38 Status panel 38 Switching on 23 Time domain 15 46 options 47 transmission 50 Trace hold 36 Trace smoothing 34 Transmission parameters 13 Troubleshooting 71 USB 21 23 Ventilation grilles 65 Warranty 73 Windowing 20
6. CD ROM supplied Follow the instructions included with it After successful installation of the driver the adaptor can be used Typically when plugged in the adaptor will appear as COM4 port on your PC If necessary you can confirm this by following the following steps LA19 13 02 DW96659 iss 1 8 22 of 74 Open the Control Panel from Start gt Settings Open the System window by double clicking on the System icon Select the Hardware tab Select the Device Manager Expand the Ports LPT amp COM section by clicking on the sign A Communications port should appear typically COM4 Note Install the USB to RS232 adaptor use mini CD supplied before attempting to use the device with the instrument Follow the instructions provided After installation ensure that a valid COM port has been assigned 1 to 16 If a port higher than 16 has been assigned e g COM17 then change it manually to a value lower than 17 Proceed as above and then select properties by right clicking on the USB Serial port entry From the Port Settings tab select advanced and change port number 4 3 Serial Interface The serial interface is intended for use in conjunction with an RS232 compatible serial port fitted on a PC The link relies on RTS CTS Request to Send Clear to Send hardware handshaking Therefore 1t 1s essential that the controlling computer supports this feature The supported data rate is 115 200 baud 8 bits no parit
7. Standards the effect 1s small amounting to no more than a few degrees of phase shift at 3 GHz C C C Freq C Freq C Freq LA19 13 02 DW96659 iss 1 8 25 of 74 Matched load calibration data indicator Through connection adaptor calibration data indicator Calibration Kit Parameters Port Kit name Ki_SN3865 Load data avaiable i Thru data available fw Port 1 kit also Port 2 with Kit parameters Capacitance coefficients xE xx format non insertable G Female C Male co 1 Co GSTES DUT calibration 71 18 15 33 1 33 Offset mm 0 40 Cl 54 36 24 C3 56 2 43 Port 2 Kit name Kt_SN3824 Load data available y Port 2 kit with Kut parameters Capacitance coefficients xE xx format eae C Female Male CO fazis C2 hewan calibration Offset mm 0 00 Cl 32 75 24 C3 2438 43 Load P1 Kat Load P2 Kit E xit Cal Kit Editor Click to load existing kits Ateriat are loaded Use editor to create or click to apply edit calibration kits Figure 4 4 Calibration Kit window Offset is the short open offset mm in air As already mentioned the calibration kit editor can be used to create or edit an existing calibration kit Fig 4 5 shows the editor window A typical example is to create a new kit using an existing kit as a template to speed the process So the process would be to first load the existing calibration kit Type the new kit name in the name box and modify the parameters as required Finally cli
8. dBm Setting resolution 1 dB nominal Output power accuracy 1 5 dB max Dynamic Accuracy oo U 1 GHz a 3 GH 3 0 1 GHz oO lt Pin dBm Figure 7 1a Dynamic accuracy amplitude LA19 13 02 DW96659 iss 1 8 69 of 74 Dynamic Accuracy E iJ 1 GHz F Sst GHE 3 ss 0 1 GH S lt Pin dBm Figure 7 1b Dynamic accuracy phase Specifications Range 180 maximum phase shift per r os f t i A where Af is the aperture frequency Aperture frequency Frequency sweep step size Accurac _ PhaseError Specifications Store Recall on hard disk floppy disk Recall to memory trace from hard disk Hoppy Touchstone is a Trade Mark of Agilent Corporation LA19 13 02 DW96659 iss 1 8 70 of 74 Specifications Calibration kit 2 9mm male Matched load short open N male to Model DW96634 2 9mm female 2 pcs Calibration kit 2 9mm female Matched load short open N male to Model DW96635 2 9mm male 2 pcs Adaptor kit 2 9mm to 2 9mm Male to male 1 pc female to female 1 pc Model DW96636 and female to male 1 pc all with the same electrical length USB to RS232 adaptor EasySync model US232B LC SMA compatible connector Specifications Controlling PC data interface RS232 CTS RTS handshake 115 2 kb s Controlling PC minimum requirements Pentium 4 1 GHz or equivalent 256 MB RAM 20 MHB Hard disk storage on C
9. expose live parts The instrument must be disconnected from all voltage sources before it 1s opened for any adjustment replacement maintenance or repair Note that capacitors inside the instrument may remain charged for some time after the power supply has been disconnected Any adjustment maintenance and repair shall be carried out as far as possible with all supply sources removed and if inevitable shall be carried out only by a skilled person who is aware of the hazard involved Ensure that fuses with the required rated current and of the specified type are used for replacement Under no circumstances use makeshift fuses or short circuit fuse holders Refer to the note on the back panel for the correct fuse rating Do not block the ventilation ports on the instrument Do not wet the instrument LA19 13 02 DW96659 iss 1 8 8 of 74 3 VECTOR NETWORK ANALYSER BASICS 3 1 Introduction A vector network analyser is used to measure the performance of circuits or networks such as amplifiers filters attenuators cables and antennas It does this by applying a test signal to the network to be tested measuring the reflected and transmitted signals and comparing them to the reference signal The vector network analyser measures both the magnitude and phase of these signals 3 2 Structure of the VNA The VNA Fig 3 1 consists of a tuneable RF source the output of which is split into two paths One signal is used as the reference and i
10. frequency domain time domain and utilities to de embed measurements measure output power at the 1dB gain compression point and AM to PM conversion Figures 1 2 and 1 3 overleaf show the front and back panels of the instrument Patent applied for LA19 13 02 DW96659 iss 1 8 6 of 74 Power On Off Test Ports Measurement channel activity indicators Figure 1 2 Front panel of the LA19 13 02 10 MHz reference RS232 in out connections connector Mains input Fuses dc bias inputs Reset button for ports 1 and 2 Figure 1 3 Back panel of the LA19 13 02 LA19 13 02 DW96659 iss 1 8 7 of 74 2 SAFETY This instrument has been designed and is intended only for indoor use in a Pollution Degree 1 environment no pollution or only dry non conductive pollution in the temperature range 15 C to 30 C 20 80 RH non condensing Use of the instrument in a manner not specified by these instructions may impair the safety protection provided Do not operate the instrument outside its rated supply voltages or environmental range WARNING THIS INSTRUMENT MUST BE EARTHED Any interruption of the mains earth conductor inside or outside the instrument may make the instrument dangerous Intentional interruption is prohibited An extension cord without a protective conductor must not be used When the instrument is connected to the mains supply terminals may be live and opening the covers or removal of parts 1s likely to
11. grilles may lead to overheating and eventual failure of the instrument Front panel connectors The Port 1 and Port 2 N type connectors should be inspected routinely for signs of damage or dirt It 1s recommended that adaptors are used whenever possible to prevent damage or wear to the fixed connectors LA19 13 02 DW96659 iss 1 8 66 of 74 7 PERFORMANCE SPECIFICATION The instrument s performance specification 1s given below Unless otherwise stated the figures apply with 128 averages at an ambient temperature of 23 1 C and 90 minutes after power up Specifications Measuring parameters 11 821 822 S12 P1dB Power at 1dB gain compression AM PM conversion factor Error correction 12 term S11 1 port correction S21 normalise normalise isolation S21 source match correction normalise isolation averaging smoothing Hanning and Kaiser Bessel filtering on time domain measurements electrical length compensation manual electrical length compensation auto de embed 2 embedding networks may be specified impedance conversion 2 traces channel Display formats Amplitude logarithmic and linear Phase Group Delay VSWR Real Imaginary Smith Chart Time Domain one per channel 6 Segments per chine overlap lowed per channel overlap allowed Markers ol four four markers o Marker functions Normal A marker fixed marker peak min 3 dB and 6 dB bandwidth Phase noise 10 kHz 65 dBc Hz 3 MH
12. out using only 4 Standards Insertable DUT e Open circuit 2 pieces one male and one female e Short circuit 2 pieces one male and one female e Matched termination 2 pieces one male and one female e Through connection cable Non Insertable DUT Open circuit 1 piece Short circuit 1 piece Matched termination 1 piece Characterised through connection adaptor 1 piece Through connection cable So for insertable DUTs the requirement is for two calibration kits one of each sex The open and short circuits of each kit must have equal electrical lengths Generally it 1s required that the matched termination should be of good quality and as a guide should have a return loss of better than 40 dB However the LA19 13 02 allows terminations with relatively poor return loss values to be used and still maintain good accuracy This is discussed in section 4 7 1 For non insertable DUTs only a single calibration kit is required but with the additional requirement of a fully characterised through connection These are supplied with all issue 2 of LA Techniques kits The calibration kits parameters can be inspected using the window see Fig 4 4 found under the Tools menu From this the kit editor can be launched to modify and create new kits as discussed later in the section The open circuit capacitance model used 1s described by the equation below where Freq is the operating frequency Generally with typical Open Circuit
13. removing the effect of interconnecting cables or microstrip lines from measurements The LA19 13 02 allows independent reference plane extensions on each of the measurement parameters S11 S22 S12 or S21 An example of an application requiring the use of reference plane extension 1s shown in Fig 5 28a In this it is desired to measure the S11 of a device mounted on a microstrip test jig with SMA connectors In order to remove the effect of the interconnecting line to the input of the device the following procedure may be followed Perform an S11 calibration at the end of the N to SMA adaptor on Port 1 Connect the test jig without the DUT mounted on it Display the phase of the S11 on active display channel Click on the Auto Ref button on the Enhancement window Fig 5 6 Click on the Apply button on the Enhancement window The above steps will move the reference plane to the end of the microstrip line This can be verified by noting that the displayed phase is close to 0 over the entire measurement band Imperfections associated with the microstrip line and coaxial connector loss dispersion etc will mean that some residual phase will remain However with careful design and employing good RF practice for the construction of the jig this error should remain small After the above steps are completed the DUT can be mounted on the jig and its S11 parameter measured After calibration For the measurement we want Use the jig
14. test line between Ports 1 and 2 of the VNA e Display the phase of S21 on a non active channel keep active channel for S11 e Start the measurement and store data on the S21 channel only to memory use the memory window e Select Data Memory for the math function on the Memory window e Select the display Memory Math radio button on the main window Use the jig without the DUT to help move the ref plane here Use a section of line on the jig to compensate electrical lengths for S21 measurements 2xL After calibration For the S11 measurement we want ref plane is here the ref plane to be here Figure 5 28b Correcting S21 and S11 phase measurements Reference plane extension corrects S11 measurements and normalisation to a test line corrects S21 DUT on microstrip test jig LA19 13 02 DW96659 iss 1 8 54 of 74 The above steps will allow the DUT s S11 and S21 or S22 and S12 parameters to be measured with the right phase correction In addition the loss of the microstrip line will be accounted for The same approach can be used to measure S12 and S22 Note however that there will be an error on both measurements due to the imperfections of the microtrip line and connector interface With careful design of the jig these can be kept acceptably small but further accuracy can be achieved by making use of the de embedding facility described below De Embedding Facility A typical measurement jig as s
15. 1 8 40 of 74 Calibration Calibration Kits to use see Set Sweep Frequency Cal Kit Loaded tools menu Port 1 Port2 Port 2 MHz kHz Kit SN3866 ki smasz4 Start 30000 Measurement Calibration type to use sd C S3 s11 521 Stop 3000 0000 Test signal m Bl characteristics Step 7 4925 C insertable DUT 2 cal kits Norrinsertable DUT 1 cal kit Sweep y Points 401 Level dE rn lo E Reflection Transmission Progress bar Figure 5 11 Instrument calibration is carried out through the Calibration window Note The frequency sweep is set by entering the start stop and selecting the numbe of sweep points The step size is automatically calculated Table 5 1 summarises the calibration types available together with the Standards required to complete the calibration For best overall accuracy particularly when measuring low isolation devices with poor Return loss values a 12 term calibration should be performed Table 5 1 Calibration types supported S11 S21 12 Terms insertable DUT 12 Terms non insertable DUT Minimum e Matched load e Through connection e Matched load e Matched load x 2 e Matched load x 1 calibration e Open e Termination see text e Open e Open x 2 e Open x 1 Standards required e Short e Short e Short x 2 e Short x 1 e Through connection e Through cable e Through adaptor x 1 e Through cable Measurement e S11 using 3 e Frequency response e
16. 1 S22r S221 3 1 1450E 04 1 0852E 04 9 9965E 01 1 0394E 03 9 9947E 01 7 4717E 04 1 0723E 04 4 9711E 05 32 97 2 9307E 04 1 9923E 04 9 9973E 01 1 0241E 02 9 9934E 01 1 0505E 02 2 0715E 04 2 0814E 04 62 94 4 1774E 04 4 3168E 04 9 9922E 01 1 9672E 02 9 9927E 01 1 9668E 02 2 8195E 04 2 8897 E 04 92 91 5 3415E 04 5 7609E 04 9 9898E 01 2 9165E 02 9 9855E 01 2 8852E 02 4 0525E 04 2 8043 E 04 122 88 7 1924E 04 6 4942E 04 9 9883E 01 3 8214E 02 9 9846E 01 3 8128E 02 4 0646E 04 2 8133 E 04 152 85 7 8941E 04 7 5903E 04 9 9834E 01 4 7690E 02 9 9807E 01 4 7805E 02 5 4323E 04 2 2344E 04 182 82 9 9069E 04 7 8126E 04 9 9792E 01 5 7033E 02 9 9758E 01 5 7198E 02 5 7273E 04 2 9411 E 04 2129 1 0791E 03 8 0397E 04 9 9715E 01 6 6419E 02 9 9699E 01 6 5967E 02 5 7191E 04 2 6551E 04 242 76 1 2779E 03 8 5429E 04 9 9648E 01 7 5557E 02 9 9625E 01 7 5449E 02 6 3081E 04 2 9580E 04 Figure 4 6b Characteristics of the through connector must be a full set of S parameters real and imaginary in this format In order to add matched load or through adaptor data to a calibration kit follow the steps below Load kit using the Kit Editor see Fig 4 5 Check the Load Data Available box on the Kit Editor parameters window If existing kit already has load or through data then un check and re check the appropriate box If this is not done the existing data will be kept and copied to the new kit If needed manually enter the rest of the kit parameters Ensur
17. 1 of 74 Part of a typical 2 Port S parameter file is shown below The header shows that the frequency units are MHz the data format is Magnitude and Angle and the system impedance is 50 2 Column 1 shows frequency 2 and 3 S 4 and 5 S21 6 and 7 Sy and 8 and 9 S20 06 09 2005 15 47 34 Ref Plane 0 000 mm MHZ SMA R 50 3 0 00776 16 96 0 99337 3 56 0 99324 3 53 0 00768 12 97 17 985 0 01447 19 99 0 9892 20 80 0 98985 20 72 0 01519 15 23 32 97 0 01595 20 45 0 98614 37 96 0 98657 37 95 0 01704 6 40 47 955 0 01955 28 95 0 98309 55 15 0 98337 55 10 0 018 1 13 62 94 0 02775 24 98 0 98058 72 29 0 98096 72 29 0 0199 6 07 T1925 0 03666 11 76 0 97874 89 46 0 9803 89 45 0 02169 23 06 92 91 0 04159 6 32 0 97748 106 62 0 9786 106 62 0 01981 48 43 107 895 0 0426 24 79 0 97492 123 77 0 97579 123 89 0 01424 87 79 122 88 0 0396 41 35 0 97265 141 25 0 97269 141 30 0 00997 166 81 137 865 0 03451 52 96 0 96988 158 65 0 96994 158 76 0 01877 113 15 152 85 0 03134 56 07 0 96825 176 27 0 96858 176 28 0 03353 69 81 167 835 0 03451 57 72 0 96686 166 10 0 96612 165 99 0 04901 34 83 182 82 0 04435 67 59 0 9639 148 18 0 96361 148 21 0 06131 1 42 197 805 0 05636 86 28 0 96186 130 15 0 96153 130 06 0 07102 33 33 212 79 0 06878 110 45 0 95978 111 82 0 95996 111 90 0 07736 69 57 221 115 0 08035 136 14 0 9557 93 50 0 9568 93 41 0 08303 107 21 242 76 0 09099 161 24 0 95229 74 84 0 95274 74 89 0 08943 144 34 257 745 0 1018
18. 2 mm male 1 x Through adaptor 1 x Through adaptor 1 x Matched load data 1 x Matched load data 1 x Through adaptor data 1 x Through adaptor data 2 x N male to 2 92 mm male 2 x N male to 2 92 mm female 4 7 1 Using a matched termination with poor return loss A successful calibration can be carried out without the need for a good quality matched load In order to retain accuracy it is necessary to provide the instrument with accurate performance data of the matched load to be used The data needs to be in a fixed format as shown in Fig 4 6a LA19 13 02 DW96659 iss 1 8 27 of 74 Frequency MHz S11 real imaginary 3 1 7265E 03 7 7777E 05 32 97 1 6588E 03 3 3093E 04 62 94 1 4761E 03 5 9003E 04 92 91 1 4653E 03 1 0253E 03 There must be 101 data lines Typically these should cover the band 3 MHz 3 GHz No 182 82 1 0884E 03 1 9085E 03 empty or comment lines 212 79 8 7216E 04 2 1355E 03 are allowed at any point 242 76 7 0326E 04 2 4109E 03 272 73 5 7006E 04 2 6790E 03 122 88 1 3841E 03 1 2608E 03 152 85 1 1924E 03 1 5800E 03 Figure 4 6a Characteristics of matched load must be in this format When supplied the data for the through connection adaptor must be in the format shown below in Fig 4 6b The data must be a full set of S parameters with no empty or comment lines It is recommended that the data spans the full frequency range from 3 MHz to 3GHz Freq MHz S111 Slir S211 S211 S12r 12
19. 3 175 34 0 94707 56 03 0 94755 55 95 0 09906 179 63 3 5 Displaying Measurements Input and output parameters S and S22 are often displayed on a polar plot or a Smith chart The polar plot shows the result in terms of the complex reflection coefficient however impedance cannot be directly read off the chart The Smith chart maps the complex impedance plane onto a polar plot All values of reactance and all positive values of resistance from 0 to oo fall within the outer circle This has the advantage that impedance values can be read directly from the chart Arcs of constant reactance 511 Reflection Z Centre of R i chart Z J Real axis oN R jX Circles of constant resistance 3 0000 MHz 3000 0000 MHz Fig 3 4 The Smith Chart LA19 13 02 DW96659 iss 1 8 12 of 74 3 6 Calibration and Error Correction Before accurate measurements can be made the network analyser needs to be calibrated In the calibration process well defined standards are measured and the results of these measurements are used to correct for imperfections in the hardware The most common calibration method SOLT Short Open Load Through uses four known standards a short circuit an open circuit a load of the same value as the system impedance and a through line These standards are usually contained in a calibration kit and their characteristics are stored in the analyser in a Cal Kit definition file For analysers that have a full S paramet
20. 5 1 6 SaS DAE AA E A E E E TRA 38 5 1 7 Measurement stat Olarte 38 5 1 8 PC data ink iter Up dd dde 39 I 21111510721 10 e ean CPAU N 39 5 2 1 Changing the Frequency Sweep Settings without Re CalibratiM8 oooooonnonnnonononnnnnnnos 43 5 3 Measure meni lidia 44 5 3 1 A O a a a A IN 44 5 3 2 ASEO LOSA AAA eee 44 5 3 3 Complete 2port imc aureolas 45 5 3 4 TOUD A a 45 5 3 5 Time domain O de e OR OO 46 5 3 6 Reverse measurements on two port devices ccc ccccceeceseeseeseeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees 51 537 Powering active devices using the built in bias TS 0 ccccccceccceeeeeeeeeeeeeeeeeeeeeeeeeeees 51 5 4 Reference Plane Extension and De Embed ding ou ccc cccccceseeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees 52 5 5 Sii DP ee Ware eg ered settee cota 55 307 ACTA PAA ac casciessss Pac earns asus es oan li 56 3E A eS o a en nee eae meen S6 5 8 Saa ene nee a ete ene ee ene rete ne ene ee RO ee ene 57 5 9 Ssion al Generator Il eni i EEE E E 57 5 10 Output Power at the 1 dB Gain Compression Point Utility ooonnnnnnnnnininininnnnnnnnnnnnnnnnnnnnnnnnn os 57 SI AM TO PM Conversion UUV esie ged oidsaa eitendnddad cee eed ask 60 5 12 Closing Down the User Interface WiNdOW oococnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn nn rra 61 Performance verification and maintenance cccoccccnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnoss 62 6 1 Measurement Uncen Tin arenen a E a a o A o E 63 02 Routine Mant
21. LA19 13 02 DW96659 iss 1 8 l of 74 LA19 13 02 3 GHz Vector Network Analyser User s Manual LA Techniques Ltd Tel 01372 466040 Fax 01372 466688 E mail info latechniques com Web site www latechniques com The Works Station Road Claygate Surrey KT10 9DH VAT no GB 689 4720 79 Registered in England No 3356289 Registered Office as above LA19 13 02 DW96659 iss 1 8 2 of 74 Blank Page LA19 13 02 DW96659 iss 1 8 3 of 74 l 2 3 4 T 8 9 l Contents DE e 5 SO A A AA ESA fi Vector Network Analyser Basil 8 3l MAEVE UCN OMe 52s same cn E E A E E ge E 8 3 2 Struc mire of the Y NAS 8 3 3 Measure MEOE eien do 8 3 4 O ease A 9 a gt Displaying Measurements ai aisla i 11 J0 Calibration and Error C orreclioMess od 12 Ooh Oer A A eee 12 O a e N Em E 21 4 1 Miniman REGUE MENS do 21 4 2 Installation of Optional USB to RS232 Adaptor cccccccccncnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnss 21 4 3 A A T A A E E E E ET 22 AR OSB OA SAS 22 A gt User Interface Sottware Installanon Gs asec een 23 4 6 Swennen he YNA A aaa e a a a a a 23 A albanon Kierra aa a e N a s 24 4 7 1 Using a matched termination with poor return loSS ooocnnnnnnnnnninnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnno 26 OPIO A cta 29 5 1 The User Intertace o A E EE E elas Gla 29 5 1 1 Dipy Se 0 Derea al ne 30 5 1 2 Dita Mari 31 2 Measurement enhancement tii 33 5 1 4 Memory taei AP E O E O E 36 5 15 Limit Deities Paci A a a aA 36
22. S11 using 3 term error e S11 S21 S12 S22 using e S11 S21 S12 S22 using capability term error with isolation correction 12 term error correction 12 term error correction correction e Frequency response correction with isolation and source match correction The basic calibration sequence 1s shown as a flowchart in Fig 5 12 LA19 13 02 DW96659 iss 1 8 41 of 74 Set test signal characteristics calibration window Select calibration required Start tools menu File drop down Apply menu if Calibration required Save calibration End Figure 5 12 Instrument calibration sequence Non Insertable DUTs Insertable DUT bur JE ica R 0 Female connector put E j Calibrate p Se Calibrate A DUT amp Measure gt ST put a Measure Use adaptor Figure 5 13 Insertable and non insertable DUTs It is important to be aware of the difference between insertable and non insertable devices and the impact on measurement and calibration technique Figure 5 13 illustrates the difference between an insertable device and non insertable devices The key issue 1s that with non insertable devices an adaptor may be required during the measurement as shown In order to obtain accurate measurement data the effect of the adaptor needs to be removed from the measurements The possible ways of doing this with the LA19 13 02 VNA are as foll
23. are inter related so when using the Zo conversion facility and no external impedance matching networks without a full set of S parameters available e g only an S11 calibration the program will assume values for the unavailable parameters as shown in Table 5 1 A warning will be displayed in such Table 5 1 Values assumed for parameters not available during Zo conversion 10 j0 0 10 j0 0 10 j0 0 LA19 13 02 DW96659 iss 1 8 36 of 74 5 1 4 Memory facility The current displayed data on each channel can be stored in memory Also each channel can be stored independently of all others The Memory Set Up window is used to store the data and this window can be displayed by clicking on the Memory button on the main window olx i Math T Hold pt display channel A ee Select trace hold ata to store in memory HEN Data Memory function memory 7 CH3 CH4 C Data Memory will hold peak or minimum values al C Data Memory Click on Erase All to clear the memory Select math _Erssel_ _ Close Window function used if Display Memory Math is used Figure 5 7 The Memory Set Up window 1s used to store data into memory Once the data is stored it can be displayed by clicking on the Display Data and Memory radio button on the main User Interface window There are three vector math functions available sum substraction and division The selected function is used whe
24. ase MHz the second indicates the parameters measured in this case S parameters the third indicates the format of the measurement in this case Magnitude and Angle If this had been RI instead of MA it would have indicated the format was Real and Imaginary The number of columns of data depends on the parameters that have been measured A 1 Port measurement measures the reflected signal from the device under test and will usually produce three columns If the format is MA magnitude and angle then the first column is the measurement frequency the second is the Magnitude of S and the third is the Angle of S41 If the format is RI then the second column is the Real part of Si and the third column is the Imaginary part of S When a reflection and transmission measurement 1s made there will be five columns of data Column 1 will be the measurement frequency Column 2 and 3 will contain S magnitude and angle or real and imaginary data and Columns 4 and 5 will contain S2 magnitude and angle or real and imaginary data If a full 2 Port measurement is made there will be nine columns of data Column contains frequency information Columns 2 and 3 Sj data 4 and 5 Sp data 6 and 7 S 2 data and 8 and 9 Sz data The LA19 13 02 VNA can generate full set of 2 port parameters but the user can chose to export either 1 port or full 2 port S parameter files to suit most RF microwave circuit simulators LA19 13 02 DW96659 iss 1 8 1
25. ation Test signal status power Serial port and rate G Level OdBm Temp 24 1 degC Sweep Off 0 6500 A A Instrument temperature Status Panel Frequency step in use Sweep status Figure 5 1 User interface window LA19 13 02 DW96659 iss 1 8 30 of 74 5 1 1 Display set up Setting up the display is carried out through the Display Set Up window which is called up from the main UI window by clicking on the Display button The window is shown in Fig 5 2 The typical sequence to set up the display is as follows e Set the number of channels to be displayed by clicking on the appropriate radio button under Display Channels e Select the desired active channel from the drop down list can also be selected by left clicking on a marker on the desired display channel e Select the channel to set up by clicking on the appropriate radio button under Select e Choose the desired parameter to display on this channel from the drop down list under Parameter Graph Type e Choose the desired graph type from the drop down list under Parameter Graph Type e Select the vertical axis values from the Vertical Axis section If desired the Autoscale button can be clicked to automatically set the sensitivity and reference values Note that reference position 1 is at the top Fig 5 3 e Click the Apply button to apply the selected values e Repeat the above steps for each display needed Note The A
26. ation kits optionally supplied with the instrument The plots for S21 S12 assume the DUT has a value of S11 and S22 of less than 0 05 Similarly the plots for S11 522 assume the DUT has a value of S21 S12 of less than 0 01 Other external factors such as connector and cables effects are excluded 11 S22 Amplitude Uncertainty Uncertainty dB S11 22 dB Fig 6 2 Reflection Measurement Uncertainty amplitude 11 S22 Phase Uncertainty Uncertainty deg S11 S22 dB Fig 6 3 Reflection Measurement Uncertainty phase LA19 13 02 DW96659 iss 1 8 64 of 74 S21 S12 Amplitude Uncertainty m S o gt S21 S12 dB Fig 6 4 Transmission Measurement Uncertainty amplitude S21 S12 Phase Uncertainty o ESO 2 10 00 gt c 21 S12 dB Fig 6 5 Transmission Measurement Uncertainty phase LA19 13 02 DW96659 iss 1 8 65 of 74 6 2 Routine Maintenance Electrical safety The safety ground should be checked regularly in accordance with best practice This should include a resistance test and a visual inspection of the mains connector and lead Ventilation grilles Check that all ventilation grilles are clear of any debris dust or any other material that may impede the flow of air Particularly check the vents in the bottom panel of the instrument It is advisable to brush these to remove any gradual build up of dust Failure to clean the ventilation
27. aw crosstalk remains below limit Receiver dc offset test that this is at normal level Ti Hardware Diagnostics Ioj x Tests Synthesizer Range Test Signal Levels Receiver Levels Receiver Crosstalk Recerver OC Offset Figure 8 2 The Diagnostics Tests perform internal checks on key components If any of the tests returns an error check connectors and linking cable If this does not resolve it re start the UI program see Fig 8 1 and reset the VNA when prompted to do so Wait until the front panel channel activity indicators have stopped flashing after pressing reset to continue with the tests Back Restore Up EEPROM This facility allows the internal ROM memory of the instrument to be backed up or restored This facility should only be required by service or repair personnel LA19 13 02 DW96659 iss 1 8 73 of 74 9 WARRANTY This instrument 1s warranted against any defects of material or workmanship within a period of three years following the date of delivery Any instrument claimed to be defective during the warranty period should be returned to LA Techniques Ltd at the owner s risk and expense Prior to return LA Techniques or its representative must be contacted to obtain a Returns Material Authorisation For your local representative contact LA Techniques or visit its web site at http www latechniques com LA Techniques Ltd does not guarantee that the operation of the instrument software or firmware will b
28. bration process Note that the ventilation inlets should be checked as described later Table 6 1 Instrument verification calibration schedule magnitude 128 averages 0 dBm test level phase 128 averages 0 dBm test level S11 S21 S12 and Stepped impedance line 201 points sweep 10 3010 MHz 12 term S22 magnitude Beatty line or other 128 averages 0 dBm test level known mismatch 201 points sweep 10 3010 MHz 12 term S22 phase Beatty line or other 128 averages 0 dBm test level known mismatch As a guide a 75mm long line provides a good impedance range It is recommended that the measured results should be compared with the values provided with the standards at no less than seven points say 40 505 1000 1495 2005 2500 and 3010 MHz Frequency values may be varied to agree with those available for the standard used The recommended test arrangement is shown in Fig 6 1 The results should be within the instrument s quoted uncertainty as detailed in the following section VNA ae Port 2 Port 1 Port 1 20 dB Standard Beatty line Matched load Fig 6 1 Performance verification arrangement Use a Beatty standard to verify S11 522 LA19 13 02 DW96659 iss 1 8 63 of 74 6 1 Measurement Uncertainty The worst case 3 GHz measurement uncertainty is shown in the following graphs The figures are based on calibration 12 term with 0 dBm Port 1 power and using 128 averages using economy calibr
29. ck Save Kit to save the new kit under a new name In the above example if the existing kit loaded had load data and or through data and it is required to replace this with new data then uncheck the appropriate box and then re check it LA19 13 02 DW96659 iss 1 8 26 of 74 Click if load data is available Click if through adaptor data is available EX Cal Kit Editor fe lx o o Kit Values A Newk Load data availabhs Thu data available 7 Kit parameters Capacitance coefficients WE xx formal C Female Male CO 171 1E 15 C2 133 1E 33 Offset mm 040 C1 54 3E 24 C3 56 2E 43 Load Existing Kit Save Kit Exit Click here to resetall Click here to load and After entering all values click Values and start afresh Edit an Existing kit or to to save kit You will be prompted for Use it as a template load and though data files as required Figure 4 5 Calibration Kit Editor The Economy calibration kits optionally supplied with the LA19 13 02 provide an economical solution whilst retaining good measurement accuracy They are fitted with SMA compatible connectors and the available kits are as follows Table 4 1 Optional economy calibration and adaptor kits DW96635 Iss 2 DW96634 Iss 2 DW96636 1 x 2 92 mm Matched load 1 x 2 92 mm Matched load 1 x 2 92 mm female to 2 92 mm female 1 x Short circuit 1 x Short circuit 1 x 2 92 mm male to 2 92 mm male 1 x Open circuit 1 x Open circuit 1 x 2 92 mm female to 2 9
30. constant value typically though not always representing the average time for a signal to transit the device Differences from the constant value represent deviations from linear phase Variations in group delay will cause phase distortion as a signal passes through the circuit When measuring group delay the aperture must be specified Aperture is the frequency step size used in the differentiation A small aperture will give more resolution but the displayed trace will be noisy A larger aperture effectively averages the noise but reduces the resolution Gain compression The 1 dB gain compression point of amplifiers and other active devices can be measured using the power sweep The small signal gain of the amplifier is determined at low input power then the power is increased and the point at which the gain has fallen by 1 dB is noted Fig 3 8 LA19 13 02 DW96659 iss 1 8 15 of 74 cin O IO ee ae ee O E O C ee Input Power Fig 3 8 The 1 dB gain compression is often used to quote output power capability AM to PM conversion Another parameter that can be measured with the VNA is AM to PM conversion This is a form of signal distortion where fluctuations in the amplitude of a signal produce corresponding fluctuations in the phase of the signal This type of distortion can have serious effects in digital modulation schemes where both amplitude and phase accuracy are important Errors in either phase or amplitude ca
31. ctive Channel selection must be of a channel to be displayed Channel to be set up O x T Display Set Up Parameter Graph Type Parameter 611 Graph LogMag Display Channels CH2 Single CH1 Two CH1 CH2 Two CH3 CH4 Four ALL C CH3 C CH4 Vertical Axis Units dE CHI S CH1 CH2 Reference q C CH3 CH4 ALL Active Channel fi Display Options Ref Position F Wi Sensitivty 10 Aubozcale Channel on which marker value is read out Apply settings before selecting next channel Figure 5 2 The Display Set Up window is used to set up the measurements display LA19 13 02 DW96659 iss 1 8 31 of 74 Reference value Vertical scale DI gt 00 d 100 dB OIV Reference line position 2 a Position 5 3 0000 MH 3000 0000 Mi B Start frequency Stop frequency pame Figure 5 3 Display graph parameters The colours of the main graphics display can be changed to suit individual preferences This can be done by selecting the Colour Scheme item from the Tools drop down menu To set a colour click on the preview box next to the item name 5 1 2 Data markers It is possible to display up to 4 markers on each display They are set up by clicking on the Markers button Fig 5 4 There are four possible marker modes as follows Active marker The active marker is the marker us
32. d nature of the data and the truncation in the frequency domain is to produce a sin x x response when transformed to the time domain This appears as ringing on both the displayed impulse response and the step response To overcome this problem a technique known as windowing can be applied to the frequency domain data before implementing the Inverse Fourier Transform The windowing function progressively reduces the data values to zero as the edge of the frequency band is approached thus minimising the effect of the discontinuities When the modified data is transformed the ringing is reduced or removed depending on the selected windowing function However the windowing function reduces the bandwidth and so increases the width of the pulse in impulse response mode and slows the edge in step response mode A balance must be made between the width of the pulse or speed of the edge and the amount of ringing to be able to determine closely spaced discontinuities The LA19 13 02 VNA allows one to choose a rectangular window no bandwidth reduction a Hanning window raised cosine or a Kaiser Bessel window The order of the Kaiser Bessel window can be set by the user Aliasing The sampled nature of the data means it is subject to the effects of aliasing The result 1s repetition of time domain response at the effective sampling rate in the frequency domain This limits the maximum time delay and hence maximum cable length that can be observed In
33. domain An alternative to traditional TDR is where the time domain response is determined from the frequency domain using an Inverse Fast Fourier Transform IFFT Several methods are available for extracting time domain information from the frequency domain The main methods are Low Pass and Band Pass The Low Pass method can produce results that are similar to the traditional TDR measurements made with a Time Domain Reflectometer using a step signal and can also compute the response to an impulse It provides both magnitude and phase information and gives the best time resolution However it requires that the circuit 1s dc coupled This is the method supported by the LA19 13 02 VNA The Band Pass method provides only magnitude information so it is not possible to distinguish between inductive and capacitive reactances Also the time resolution 1s only half as good as in the Low Pass mode However the method can be used for circuits where there is no DC path and hence is suitable for AC coupled circuits such as band pass filters This method is not currently supported in the LA19 13 02 VNA Low Pass method The Low Pass method uses an Inverse Fourier Transform to determine the impulse response in the time domain from the reflection coefficient measured in the frequency domain The DC component is extrapolated from the low frequency data to provide a phase reference Alternatively if the DC termination is known it can be entered manually Once
34. e error free or uninterrupted The warranty above shall not apply to defects caused by improper or inadequate maintenance by the user user supplied software user modifications or misuse operation outside the stated environmental specification 10 EC DECLARATION OF CONFORMITY We LA Techniques Ltd The Works Station Road Claygate Surrey KT10 9DH UK declare that the instrument model number LA19 13 02 meets the intent of the EMC Directive 89 336 EEC and the Low Voltage Directive 73 23 EEC EMC Emissions Generic 50081 1 1992 referencing EN55022 Class B Immunity Generic 50082 1 1998 Class B Safety EN61010 1 Safety requirements for electrical equipment for measurement or 2001 control in laboratory use Nils Nazoa LA Techniques Ltd 11 November 2005 LA19 13 02 DW96659 iss 1 8 Activity indicators 6 23 Aliasing 20 AM to PM conversion 15 utility 60 Averages 34 Back panel 6 Bias T 51 67 Calibration 39 Calibration kit 24 capacitance coefficients 24 Closing down 61 Colours 32 Crosstalk 67 Data loading 56 saving 55 Data link interruption 39 De embedding 52 Diagnostics tests 71 Directivity 67 Display set Up 31 Display colours 32 Dwell time 34 Dynamic accuracy 67 68 Earth conductor 7 Electrical safety 7 65 Enhancement 34 Front panel 6 Front panel connectors 6 65 Gain compression 14 utility 57 Graphics plotting 56 saving 57 Group delay 14 45 Impedance conversion 33
35. e mounted on a 50Q test Jig is somewhat simpler to measure LA19 13 02 DW96659 iss 1 8 35 of 74 The steps necessary for each of the two techniques illustrated in Fig 5 6a are as follows 750 Device with Connectors 1 Connect 50Q to 750 impedance matching networks e g matching pads at the ends of the cables connected to ports 1 and 2 1 In the Enhancement window check the box Convert System Zo 1 Check External Zo match to indicate external matching networks in use iv Enter 75 in the Convert System Zo value box and click Apply v Proceed to calibrate using a 75Q calibration kit vi Connect the DUT and start the measurement 750 Device mounted on 50Q Test Jig 1 In the Enhancement window uncheck the box Convert System Zo 11 Calibrate at the ends of the test cables using a 500 calibration kit 11 Apply de embedding to remove test jig effects See section 5 4 for some suggestions iv In the Enhancement window check the box Convert System Zo v Uncheck External Zo match box in this case mathematical impedance conversion 1s done by the software vi Enter 75 in the Convert System Zo value box and click Apply vii Connect the DUT and start the measurement Po 75 2 0 8 4DIV MARKERS NI Graph 1511 System impedance Ref Plane conversion value 0 00 ram Marker 1601 5000 MHz 12 829 dB Figure 5 6b System impendance chosen is displayed on the top right corner Note S parameters
36. e plotted In addition the AM to PM factor at the LA19 13 02 DW96659 iss 1 8 61 of 74 specified input power entered will be displayed in the text box in the Measure section of the window Port 1 W Output attenuator attenuator Figure 5 37 Calibration left and test connections for AM to PM test Note For best AM PM results apply some averaging e g 16 and carry out an AM PM calibration left hand side of Fig 5 37 A 2 will displayed if the requested Pin for readout is outside the available range 5 12 Closing Down the User Interface Window It is recommended that a formal shut down of the user interface window is carried out before the VNA is to be switched off This allows the calibration and status to be saved and the instrument s log file to be updated The sequence is shown below in Fig 5 38 21 L419 13 01 YNA Control Stop Tools Utilities Help aa Load Cal Save Cal Print Graphics Select Exit from File drop down menu Switch off VNA Save Measurements Load Measurements Exit End Figure 5 38 Formally closing down the software LA19 13 02 DW96659 iss 1 8 62 of 74 6 PERFORMANCE VERIFICATION AND MAINTENANCE It is recommended that the instrument is checked annually for safety and compliance with the stated electrical specification Table 6 1 shows the parameters that should be checked as part of the cali
37. e the correct offset 1s entered 101 frequency points LA19 13 02 DW96659 iss 1 8 28 of 74 e Click the Save Kit button e When prompted select the data file containing the matched load and or the through adaptor data in the format shown in Fig 4 6 e Save the kit for future use by clicking the Save Kit button Fig 4 5 Note When a kit is loaded any available matched load or through adaptor data that 1s associated with the kit will be automatically loaded Issue 2 of the economy calibration kits optionally supplied with the LA19 13 02 come complete with matched load and through adaptor data in a CD ROM The files should be copied to the PC s hard disk for easy access It is critically important that the correct kit data check serial number is loaded LA19 13 02 DW96659 iss 1 8 5 OPERATION 29 of 74 Operation of the instrument is carried out through the User Interface UI window This allows programming of the measurement parameters and plots the measurement results in real time The UI window includes a status panel This displays information that includes calibration status frequency sweep step size and sweep status Note that a copy of this manual is provided in the Help drop down menu 5 1 The User Interface Window The main User Interface window 1s shown in Figure 5 1 This 1s dominated by a large graphics area where the measurement results are plotted together with the readout of the mark
38. e the unit allows after setting each frequency point before making the measurement The default value is 0 5 ms and the optional value of 2 5 ms need only be used for very high Q devices which may require more than 0 5 ms to settle The Port 1 Level sets the test signal level The default value is 0 dBm as this gives best overall measurement accuracy However it may be necessary particularly when measuring active devices e g amplifiers to reduce the test level For best measurement accuracy it is recommended that the calibration is carried out at the same test level as it is intended to use for the measurement Whenever the test level is different to that used for the calibration a will be added to the calibration status indicator on the Status Panel Fig 5 1 The Reference Plane facility allows the reference plane of each parameter measurement to be arbitrarily moved away from the calibration plane The value LA19 13 02 DW96659 iss 1 8 34 of 74 entered applies to the measurement parameter S11 S21 S12 or S22 displayed on the active channel Note that the same plane value will be used for all other measurements on that same parameter regardless if they are on the active channel or not The Auto Reference automatically moves the reference plane It uses the measurement on the active channel This feature is particularly useful for example when measuring microstrip devices and it is necessary to remove the effect of the connec
39. ed for comparison when the delta marker mode switched on by selecting a reference marker is on One of the displayed markers must be chosen as the active marker Reference marker The reference marker causes the delta marker mode to be switched on The value difference between the active marker and the reference markers is shown on the right hand marker display panel Fixed marker A fixed marker cannot be moved and its position is not updated with subsequent measurement values It provide a fixed reference point Only a reference marker can be made a fixed marker Once a marker is fixed it cannot be moved until it is unfixed Normal marker The value of a normal marker is displayed on the right hand marker readout panel Any marker except a fixed marker can be moved to a new position by left clicking on it on any displayed channel and dragging it to a new postion The markers set up form provides a Peak Minimum Search facility This places marker 1 at either the peak or minimum value on the displayed trace on the active channel when the corresponding Find button is pressed LA19 13 02 DW96659 iss 1 8 32 of 74 Select markers For delta marker mode to display Select reference marker 1 Markers Set Up E Ioj x Saec wht Active Marker Markers a marker is active Marker Marker 2 ate ma 3 de band C Marker3 f Marker 4 dB band e Marker2 Ref e Marker3 Ref Find e Marker4 Ref Position of
40. een established and the DUT is in place and powered up as appropriate enter the values into the Pigg control window Fig 5 34 LA19 13 02 DW96659 iss 1 8 59 of 74 Note that the output attenuation value impacts directly on the Pj g value it is important to enter an accurate value that takes into account all losses in the output path including any connecting cable that may have been used Pressing the Start button will perform the test plot the gain and output power curves and compute the Pigg This together with the linear gain will be displayed in the text boxes to the right of the Start button The results can then be printed the window as displayed will be printed or saved as a text file by clicking on the Print or Save button 10 x Enter Values Port Sweeps 20 to O dBm T P1d6 Utility ZFL 1000LN Measurement Title 1006 9950 Test Freg MHz hoo Input Attenuation dE ET Output Attenuation dE azo Input Cable Loss dE d Bd Brrv Measure Calibrate P1dB dBm Gain dE 6 88 22 40 23 2 Pin dBm Figure 5 35 The P g measurement utility control window LA19 13 02 DW96659 iss 1 8 60 of 74 5 11 AM to PM Conversion Utility This utility allows the measurement of the AM to PM conversion factor of a DUT Generally it is used for evaluating the linearity of active devices such as amplifiers The utility 1s started up by going to the drop down menu u
41. ena onis A ies 65 PETLORMANCE PEC ICAU OI acco crores a E E AE 66 TrOUBIESNOO UMNO Oiid AAA AAA a ee A a A A 71 NO 73 LA19 13 02 DW96659 iss 1 8 4 of 74 Blank Page LA19 13 02 DW96659 iss 1 8 5 of 74 1 DESCRIPTION The LA19 13 02 1s a personal computer driven Vector Network Analyser capable of operation over the range of 3 MHz to 3 GHz It incorporates an s parameter test set allowing direct measurements of forward and reverse parameters over an 80 dB dynamic range The test frequency can be set with a resolution of 100 Hz A simplified block diagram of the instrument 1s shown below in Fig 1 1 Serial Interface dc bias for ports 1 and 2 Device Under Test Figure 1 1 Simplified block diagram of the LA 19 13 02 The architecture 1s based on a single conversion receiver arrangement using a receiver bandwidth of 6 kHz Two identical channels are used reference and measurement The measurements are ratio measurements on these channels thereby minimising drift with temperature and time Synchronous detectors are used for signal detection followed by analogue to digital converters These digitise the measured signals before passing on to the controller The instrument s User Interface UI software runs on a personal computer and communication with the instrument is through the RS232 interface The UI carries out the mathematical processing and allows the display of measured parameters in several forms These include
42. ent When the instrument is sweeping and an alignment becomes due the alignment is performed at the end of the current sweep 5 1 8 PC data link interruption It may be possible that the data flow between the VNA and its controlling PC is interrupted by external factors In this case if the UI software cannot restore the link a message similar to that shown in Fig 5 10 will be displayed In such a case the UI software should be re started using the selection in the drop down menu under Tools and the the VNA should be reset use button on the back panel when prompted to do so Wait until the front panel lights have stopped flashing before clicking OK to complete the software re start The instrument should be re calibrated Measure s11 al AN No Response If the data link is interrupted reset the VNA red button on rear panel and re start the UI software Tools menu Figure 5 10 Warning message when the link with the PC 1s interrupted A No Response message should rarely be encountered If it happens often check that the PC being used is capable of supporting 115 2 kb s serial data rate Also avoid running the VNA software as a background task when the sweep is on 5 2 Calibration The instrument must be calibrated before any measurements can be carried out This is done by clicking on the Calibration button on the main window which brings up the Calibration window shown in Fig 5 11 LA19 13 02 DW96659 iss
43. ent during operation e Refer to qualified servicing e Login with Administrator rights and set access rights C LA19 13 02 e Delete the defcal cal file in the e Data format problem CALA19 13 02 directory menu fail button and re start UI software Error reading data files e Invalid format e Check for correct format ff line e Too many lines e Number of lines must be lt 1000 e Leading space s e Remove leading spaces from data lines e Ventilation grilles under the instrument blocked e Fan not operating e User has no access rights to directory I O Path Error or Type Mismatch error message immediately UI software is run 1 1419 13 01 YNA Control File Tools Utilities Help Calibration Kit Hardware ID Diagnostic Tests Back Up EEPROM Restore EEPROM Figure 8 1 Re Starting the program after resetting the VNA LA19 13 02 DW96659 iss 1 8 72 of 74 Diagnostics tests It 1s possible to run self check tests on the instrument This facility Diagnostic Tests is available from the Tools menu as shown in Fig 8 1 In order to complete the tests a low loss cable 1s required to link Port 1 to Port 2 The tests carry out the following checks Synthesisers test that they remain in lock over the frequency range Test signal test the level range and step size Receiver levels test that the receiver is operating at normal signal levels Receiver crosstalk test that r
44. er Bessel window The type of window the order of the Kaiser Bessel window and the time span over which the signal is displayed can be selected in the TDR options window shown below Ti Time Domain Options 0 x axl Range dec Termination f Full f Auto C Enter T1 T2 C Open circuit Entering values for T1 Short circuit T1 me and T2 allow zooming ins 5 000 m Restive in on a portion of the T2 ne 161 667 waveform 50 00 C Kaiser Bessel C Hanning Close Window 5 Order Figure 5 20 Time Domain Options window allows measurement set up Note To set a time range either starting or ending beyond 161 66 ns use the Enter T1 T2 facility However the displayed total time span must be less than 166 66 ns LA19 13 02 DW96659 iss 1 8 49 of 74 The plot below shows the same cable terminated with a short circuit The window is fifth order Kaiser Bessel This time the trace goes to 1 relative to the reference indicating a reflection coefficient of 1 for the short circuit 311 TOR gt 0011 0 5 UDI 0000 ns 0 0 8 0000 ns Figure 5 21 Measured response of 50 cm shorted cable using Kaiser Bessel fifth order window The trace below shows the effect of increasing the order of the Kaiser Bessel window to 10 The ripple has been completely removed but the slope of the edge has been further reduced 511 T R gt 00l 0 5 UOI 1 0000 ns 9 0000 ns Figure 5 22 Measured
45. er test set such as the LA19 13 02 12 systematic error terms are measured and can be corrected Leakage Reflection tracking A R Transmission tracking B R Source Mismatch Load Mismatch Fig 3 5 Key sources of errors forward measurement 3 7 Other Measurements Whilst the fundamental measurement performed by the Network analyser is S parameters many other parameters may be derived from the S parameters H Y and Z parameters can all be calculated from the S parameters Reflection parameters The input reflection coefficient I can be obtained directly from S41 The complex reflection coefficient I is given by V P S plo incident p is the magnitude of the reflection coefficient 1 e the magnitude of Sj p F LA19 13 02 DW96659 iss 1 8 13 of 74 Sometimes p is expressed in logarithmic term as Return Loss return loss 20 log p VSWR can also be derived Emax AA W eee E in l p Fig 3 6 VSWR definition Transmission parameters Transmission coefficient T is defined as the transmitted voltage divided by the incident voltage This is the same as S21 Vee T Z transmitted S TZ incident If T is less than 1 there is loss in the DUT which is usually referred to as Insertion Loss and is usually expressed in decibels A negative sign is included in the equation so that the insertion loss 1s quoted as a positive value trans Insertion _loss dB 20 log 20l
46. erages If more averages are to be used in the measurements set the value in the Enhancement window and activate averaging in the main UI window Fig 5 1 before calibration 5 2 1 Changing the Frequency Sweep Settings without Re Calibrating If the start or stop frequency or number of sweep points is changed when the instrument has a valid calibration the user is given the choice to either keep or delete the existing calibration If the user chooses to keep the calibration a new set of calibration error terms will be automatically generated by interpolation to fit in with the new sweep parameters In this case a is added to the calibration status bar to indicate that operating parameters have changed from that used in calibration If it is required to change the frequency sweep parameters without re calibrating then simply enter the new values see Set Sweep Frequency values in Fig 5 11 and click Apply Once the new values are sent to the instrument just close the window Close Window in Fig 5 11 to exit Note that this process will delete all memory traces and the display data may be invalid until a fresh measurement sweep is performed LA19 13 02 DW96659 iss 1 8 44 of 74 5 3 Measurements 5 3 1 Return loss In order to carry out return loss measurements S11 the VNA must be calibrated as described before either S11 calibration only both S11 and S21 or 12 term The device to be tested DUT is then connected to Port
47. ers A maximum of four plots can be displayed simultaneously Each plot can be programmed to display the desired measurement Display channel 1 T LA19 13 02 YNA Control File Tools Utilities Help 521 LogMag gt 0 0 dB 12 0 dB DIW meee si eee A o ee a ln io si e il ds Et Ali ti ee Pon A ASA AAA A AAA Tre SA A AAA AAA A AA E A PARA E A A AAA AA AA INIA 1800 0000 MHz 511 Reflection Z Lrr o Y 1800 0000 MHz 1 2060 0000 MHz Measurement C Off Off START STOP On C On Averaging Smoothing Display channel 3 Display channel 4 Display channel 2 10 x 512 LogMag gt 0 0 dB MARKERS Graph 1 521 Ref Plane 0 00 mm 4 0 dB DIV Ss M M ne wf a te is lt e id M nt ee A AAN PA PARAR AA AAA RARA AAA delta 3 2 72 8000 MHz 0 260 dB AAA AA RA REA AAA SAA AAA AAA SSA O A AA A AA AAA A A PARA AAA MASA Marker 1 1930 6500 MHz 1 231 dB Marker 2 1893 6000 MHz 2060 0000 MHz 3 772 dB T800 0000 MHz 522 LogMag gt 0 0 dB Marker 3 1966 4000 MHz 4 032 dB 10 0 dB DIV Marker 4 1995 0000 MHz 83 082 dB A one a AAA AAA A RARA AAA AA A A AAA PRA de ARA A PA A AA AA A AA PAPA AAA O APP A A A RR 2060 0000 MHz Calibration Markers 1800 0000 MHz Set Parameters Display Data Data and Memory C Memory Math SN 3854 1 115 2 Kb s 12 Term Cal Instrument S N Calibr
48. hown in Fig 5 29 includes input and output networks which introduce errors to the measured values of the device under test DUT For best measurement accuracy these networks can be specified in the form of 2 port s parameters files and then used to extrapolate the DUT s characteristics Input network Output DUT network Connector Connector Device to be tested Figure 5 29 De embedding allows the effects of the test jig s input and output networks to be removed The LA19 13 02 allows the user to specify s parameter files must be full 2 port data for the input and output networks as shown in Fig 5 29 so that the de embedding takes place automatically as the instrument measures the test jig After first calibrating as usual follow the steps below to enable de embedding 1 Select the s parameter file s that represent the embedding network s by clicking on the embedding network check boxe s as shown in Fig 5 6 p33 Check box Port 1 Network represents the input network as shown in Fig 5 28 and Port 2 Network represents the output network The files selected must be full 2 port s parameters files in Touchstone format 2 Click on the radio button to enable de embedding Fig 5 6 p33 Once the above steps are completed starting the measurement will display de embedded results LA19 13 02 DW96659 iss 1 8 55 of 74 The de embedding facility relies on s parameter data for the input and or output
49. ibration type is displayed In addition a symbol is drawn on the trace indicating the last error point detected as shown in Fig 5 8b The alarm 1s available for all graph types except Smith plots Click to turn on alarm Click to show limit lines 2 Limit Lines Set Up NC PRA Channel 1 W Show Limits Segment 1 Start Freq MHz Stop Freq MHz Upper Lim Lower Lirnit Segment 4 Start Freg MHz Stop Freg MHz Upper Limit Lower Limit 3 0000 1951 0500 LS Segment 2 Start Freg MHz Stop Freq MHz Upper Linit Lower Limit Segment 5 Start Freg MHz Stop Freq MHz Upper Limit Lower Limit Segment 3 Start Freg MHz Stop Freq MHz Lipper Linnit Lower Linit Segment 6 Start Freg MHz Stop Freg MHz Upper Lirit Lower Limit Figure 5 8 The Limit Lines Set Up allows at least six segments per graph 521 LogMag E 00d 10 0 dD MARKERS Graph S21 Fiat Plane 0 00 mm Marker 1006 4960 MHZ 0331 dB 2 0000 MHZ 3000 0000 MHz Figure 5 8a Complex Limit Lines templates are possible by overlapping segments LA19 13 02 DW96659 iss 1 8 38 of 74 Limit line test fail indicator 5 1 6 Figure 5 8b Limit Lines failure graphical visual indicator Status panel The status panel on the main window Fig 5 1 provides useful information to the user The information is as follows 5 1 7 Instrument serial number Serial port number in use and data rate Calibratio
50. ion to allow accurate determination of the band points 5 1 3 Measurement enhancement The measurement enhancement options are displayed Fig 5 6 by clicking on the Enhancement button on the main Ul window The options available are as follows e Averages 1 to 255 on a point by point basis e Trace Smoothing 0 to 10 e Dwell Time 0 5 ms or 2 5 ms e Port 1 Level 0 dBm to 20 dBm in 1 dB steps e Reference Plane Extension manual entry or automatic e De embedding specify embedding networks at ports 1 and or 2 e Impedance conversion for devices which are not 50Q Measurements can be converted to a different system impedance by checking Destellos this box and entering the desired i DUT parameters to be Reference plane applies impedance value must be real between a aE to active channel measurement 10Q and 20002 The use of external ON mate hinepad is ako supported which include test jig effects 2 Enhancement Set Up EIB Set Values Ref Plane apples to active Shannel De embedding Averages p Select Units mm Port 1 network 1 255 Port 2 network Smoothing 3 Enter Value 10 000 Time allowed at each point 0 10 oats p before measurement is made Smoothing A ac use 2 5ms for high Q devices pts Eunent active channe Convert to slow to settle Dwell Time los me E Ch 3 measuring 522 System Zo Port 1 Level dBm 0 gt Exit Figure 5 6 The measurement enhancement window The Dwell Time is the tim
51. lthough the user interface software can be installed in a directory chosen by the user a support directory C LA19 13 02 is also created during installation This directory will contain the following files e xxx log txt gt This is the status log file xxxx is the serial number e DefCal cal gt Default calibration data last used calibration e kit gt Calibration kit files if supplied e dat gt Load calibration data for the cal kit if supplied e EEPROM bak gt Back up data of instrument s memory e UsersManual pdf 4 6 Switching on the VNA When power is applied to the VNA the front panel channel activity indicators will flash to indicate that the controller has started up correctly The number of flashes indicate the hardware status as follows e Status normal each indicator flashes four times for a total of 2 s e Fault condition each indicator flashes twelve times for a total of 6 s If a fault condition is reported the diagnostics tests should be run as described in Section 8 LA19 13 02 DW96659 iss 1 8 24 of 74 4 7 Calibration Kit The minimum requirements to calibrate 12 term calibration the instrument depend on the device to be tested For example the most accurate calibration is for insertable devices which requires a total of 6 Standards An insertable device is one which has connectors of different sex On the other hand a calibration for a non insertable device can be carried
52. me when the reflections arrive it is possible to determine the distance to impedance discontinuities LA19 13 02 DW96659 iss 1 8 16 of 74 Sampling Scope Step source Figure 3 9 Traditional TDR set up TDR examples 1 Shorted 50 transmission line gt gt 0 time Figure 3 10 Simplified representation of the response of a shorted line For a transmission line with a short circuit Fig 3 10 the incident signal sees the characteristic impedance of the line so the scope measures Ei The incident signal travels along the line to the short circuit where it is reflected back 180 out of phase This reflected wave travels back along the line cancelling out the incident wave until it is terminated by the impedance of the source When the reflected signal reaches the Scope the signal measured by the Scope goes to zero as the incident wave has been cancelled by the reflection The result measured by the Scope is a pulse of magnitude Fi and duration that corresponds to the time it takes the signal to pass down the line to the short and back again If the velocity of the signal is known the length of the line can be calculated LA19 13 02 DW96659 iss 1 8 17 of 74 _ tv d Where v is the velocity of the signal in the transmission line t is the measured pulse width and d is the length of the transmission line 2 Open circuit 50 transmission line 0 time Figure 3 11 Simplified representation of the response
53. mission lines group delay is the transit time through the line However some components such as filters can exhibit negative group delays so care is needed when attaching an interpretation to group delay GroupDelay GA 00 LA19 13 02 DW96659 iss 1 8 46 of 74 The LA19 13 02 calculates the group delay by dividing the phase change between adjacent sweep points and dividing by the size of the sweep step It is usual to apply some degree of trace smoothing to remove very rapidly changing perturbations from the trace Care should be exercised to ensure that genuine sharp group delay variations are not masked by the smoothing Displaying the results Group Delay of any S parameter can be measured The result can be displayed by selecting the required parameter and group delay graph from the Display window as described in Section 5 1 1 5 3 5 Time domain measurements The time domain facility allows the display of the time domain response of a network under test For example time domain reflectometry TDR measurements can be made by first carrying out an S11 calibration using 1024 sweep points Similarly Time domain transmission TDT measurements can be made by first completing an S21 calibration using 1024 sweep points The steps necessary are shown in the flowcharts in Figs 5 16 and 5 17 Select S11 Set sweep to 1024 Start points Calibration Perform S11 Parameter and TD calibration Graph T
54. models for design and simulation Knowledge of the phase of the reflection coefficient 1s particularly important for matching systems for LA19 13 02 DW96659 iss 1 8 9 of 74 maximum power transfer For complex impedances the maximum power is transferred when the load impedance is the complex conjugate of the source impedance Fig 3 2 Source drives an Matching network jX unmatched load some ensures all power is signal is reflected transmitted to the load Th OCR Fig 3 2 Matching a load for maximum power transfer Measurement of phase in resonators and other components is important in designing oscillators In feedback oscillators oscillation occurs when the phase shift round the loop is a multiple of 360 and the gain is unity It is important that these loop conditions are met as close as possible to the centre frequency of the resonant element to ensure stable oscillation and good phase noise performance The ability to measure phase is also important for determining phase distortion in a network Phase distortion can be important in both analogue and digital systems In digital transmission systems where the constellation depends on both amplitude and phase any distortion of phase can have serious effects on the errors detected 3 4 S parameters The basic measurements made by the Vector Network Analyser are S Scattering parameters Other parameters such as H Y and Z parameters may all be deduced from the S parame
55. n status S11 S21 S11 S21 or 12 terms A question mark indicates that the test power has been changed from that used for calibration Test signal power This is the Port 1 signal level Instrument temperature Useful indication that the internal temperature of the instrument has stabilised The value should normally remain below 45 C Sweep status Indicates whether instrument is sweeping Frequency step Step size of sweep Overload alarm if power at port 1 of port 2 causes overload of the receiver temporarily replaces Calibration Status Limit Lines alarm if any measurement exceed the set limits temporarily replaces Calibration Status Measurement Start Stop The measurement Start Stop buttons are used to start or stop the instrument s sweep mode measurement mode This is necessary as functions which require re programming the instrument can only take place when the instrument is idling The instrument status is shown in the Status Panel as described in the previous section LA19 13 02 DW96659 iss 1 8 39 of 74 Measurement START STOF Figure 5 9 The Start Stop Measurement buttons control the sweep status Note that when the sweep is stopped the test signal will be held at the stop frequency of the sweep until an automatic receiver alignment is due At this time the frequency will change to 20 MHz Automatic receiver alignment is transparent to the user and does not interfere with the normal operation of the instrum
56. n the user selects the Display Memory Math function on the main window The trace hold is used to store the maximum or minimum values on the memory trace Trace hold is not available when group delay is displayed 5 1 5 Limit Lines facility The Limit Lines facility allows six segments to be defined for each displayed graph By taking advantage of the overlapping capability see below a maximum of 11 segments can be created The set up window shown in Fig 5 8 is displayed by clicking on the Limit Lines button on the main window Overlapping Segments All valid segments entered are loaded in sequence i e segement 1 first with the each segment loaded having priority over the previous segment This feature allows overlapping segments to be loaded For example if segment 1 is specified to cover say 400 to 800 MHz then a second segment can be specified to a section of this band for example 500 to 600 MHz This would result in a total of three segments even though only two were specified That is 400 to 500 500 to 600 and 600 to 800 MHz An example of a complex 11 segments template is shown in Fig 5 8a Alarm An alarm facility is provided with the limit lines This provides audible warning during a sweep if any measurement exceeds the limits set A visible indication of the last measurement and measurement channel in error is provided on the status panel LA19 13 02 DW96659 iss 1 8 37 of 74 where normally the cal
57. nder Utilities near the top left corner of the main window It is shown in Fig 5 36 T AM to PM Utility l joj x Enter Yalues Fort Sweeps 20 to O dBm ZFLN 1000LN Measurement Title aoz1000 Test Freq MHz hoo 8 Input Attenuation dB joo 80 Output Attenuation dE 12 00 PinfdBmiforReadout os a E i D T Measure AM to PM q AM PM deg dB at Pin requested Calibrate 219 Save Print Exit Pin dBm Figure 5 36 The AM to PM measurement utility control window In order to use this facility an S21 calibration or S11 S21 or 12 term must have been carried out For best results some averaging e g 16 should be used Further a second through calibration 1s suggested to remove residual phase variations The steps are summarised as follows AM to PM utility calibration e Perform a normal S21 calibration or S11 821 or 12 term see left hand side of Fig 5 37 e Callup AM to PM Utility window shown in Fig 5 36 e Enter frequency required Test Freq in megahertz e Click on Calibrate button connection as on left hand side of Fig 5 37 AM to PM utility test e Connect DUT with attenuators as shown on right hand side of Fig 5 37 e Enter attenuator values input power at which result is required and measurement title e Power up DUT if necessary e Click the Start button On completion of the AM to PM test a graph of AM to PM as a function of input power at the DUT input will b
58. of a open line In the case of the open circuit transmission line Fig 3 11 the reflected signal is in phase with the incident signal so the reflected signal combines with the incident signal to produce an output at the scope that is twice the incident signal Again the distance d can be calculated 1f the velocity of the signal is known LA19 13 02 DW96659 iss 1 8 18 of 74 3 Resistive termination of 50 transmission line Er is REDO P Ei R 50 R gt 50 R lt 50 AEr Er El El gt gt gt time time Figure 3 11 Simplified representation of the response of a resistively terminated line 4 Reactive terminations and discontinuities Reactive elements can also be determined by their response Inductive terminations produce a positive pulse Capacitive terminations produce a negative pulse time time Figure 3 12 Simplified representation of the response of a reactively terminated line Similarly the position and type of discontinuity in a cable due to connectors or damage can be determined A positive pulse indicates a connector that is inductive or damage to a cable such as a removal of part of the outer screen A negative going pulse indicates a connector with too much capacitance or damage to the cable such as being crushed LA19 13 02 DW96659 iss 1 8 19 of 74 gt gt _ gt time time Figure 3 13 Simplified representation of the response of a line discontinuity Time domain from the frequency
59. ogz incident If T is greater than 1 the DUT has gain which is also normally expressed in decibels trans Insertion _ gain dB 20 log 20 log 7 incident Phase The phase behaviour of networks can be very important especially in digital transmission systems The raw phase measurement 1s not always easy to interpret as it has a linear phase increment superimposed on it due to the electrical length of the DUT Using the reference plane function the electrical length of the DUT can be removed leaving the residual phase characteristics of the device Fig 3 7 LA19 13 02 DW96659 iss 1 8 Raw Phase data aso aE ss E NE PAT TN TT IS AE Nt a ee a a 18 LET IA TT NI east SNE IE geal ashy al MESS ie a 14 of 74 Electrical Length function Aaa EXP Entran HUARTE NUERA ARRSH Ree eee E 0 010 PARAMS AE eos Hrequeney Residual Phase a a a 1011015 a i a i a OA AAA AGERE Pe sl ale ea I ra Freque es Fig 3 7 Operation on phase data to yield underlying characteristics Group delay Another useful measurement of phase is group delay Group delay is a measure of the time it takes a signal to pass through a network versus frequency It is calculated by differentiating the phase response of the device with respect to frequency 1 e the rate of change of phase with frequency Group delay a af The linear portion of phase is converted to a
60. onses from simple RC networks LA19 13 02 DW96659 iss 1 8 51 of 74 sel TOR gt 0 00 0 5 Uso Taare aye Figure 5 26 Measured TDT for 100 pF series capacitor sel TOR gt 000 0 5 UR OI 1 0000 ns 59 0000 ns Figure 5 27 Measured TDT for 100 pF shunt capacitor 5 3 6 Reverse measurements on two port devices In order to measure the reverse parameters S12 and S22 it 1s necessary to complete a 12 term calibration first select insertable or non insertable DUT on calibration window as shown in Fig 5 11 The other calibration options measure only forward parameters After the 12 term calibration is completed simply select the reverse parameter s to be required on any displayed channel and start the measurement 5 3 7 Powering active devices using the built in bias Ts The LA19 13 02 VNA includes two bias Ts which can be used to provide dc bias to the measurement ports and 2 The bias Ts are rated at 250 mA and can support dc voltages up to 25V The dc injection terminals are type BNC female They are located on the back panel This facility can be used for example to provide dc bias to an active device being measured LA19 13 02 DW96659 iss 1 8 52 of 74 5 4 Reference Plane Extension and De Embedding The Reference Plane extension facility on the LA19 13 02 allows the user to shift the measurement reference plane away from the value set during calibration This can be useful in
61. ows Measuring Non Insertable Devices There are three possible ways of removing the effect of the extra adaptor needed when measuring non insertable devices These are as follows LA19 13 02 DW96659 iss 1 8 42 of 74 Table 5 2 Techniques for dealing with non insertable DUTs Calibration Used Adaptor Removal Method A 12 Term insertable DUT De embedding Accurate but requires prior knowledge of adaptor characteristics B 12 Term insertable DUT Reference plane extension Quick and easy but errors due to loss of adaptor remain C 12 Term non insertable DUT Calibration removes adaptor Accurate but requires kit with through effect adaptor Standard Only one calibration kit is required of adaptor characteristics of adaptor remain The preferred method is method C shown in Table 5 2 This requires a calibration kit that includes a characterised through adaptor but has the advantage of only needing a single kit Note that with this method the isolation step is done automatically by the software during the load measuring step Note that only the 12 term non insertable DUT calibration supports a non zero length through connection All other calibrations S21 or S11 S21 or full 12 term insertable DUT require a through connection of zero length In effect this means that the calibration port terminals should be of opposite sexes In other words it should be possible to connect the terminals together without the use of an adap
62. response of 50 cm shorted cable using tenth order Kaiser Bessel window A more complicated example The trace below shows the response of a 30 cm 50 Q line followed by 30 cm of 25 Q line terminated in a short circuit The window is third order Kaiser Bessel The trace shows the multiple reflections from the discontinuity of impedance at the connection between the lines and the short circuit termination LA19 13 02 DW96659 iss 1 8 50 of 74 511 TOR 0 0 U 0 5 UD 0000ns 0 0 130000 ns Figure 5 23 Measured response of multiple reflections See text for details The last example is the same 50 Q 25 Q cable combination but this time the termination is an open circuit The response is also displayed over a longer period 511 TOR gt 000 0 5 LD 0 0000 ns 40 000 ns Figure 5 24 Measured response of multiple reflections see text for details Time domain transmission Time domain transmission TDT is similar to the TDR technique except that the transmitted signal is observed Traditionally this is accomplished using a step source and a sampling scope as with the TDR but the transmitted signal at the output of the network 1s observed rather than the reflected signal at the input to the network This technique is useful for measuring the step response or rise time of amplifiers filters and other networks Examples Port 1 Port 2 Port 1 Port 2 El El r time time Figure 5 25 Expected resp
63. rovide the file name extension when entering the file name Typically for 1 port networks the extension slp is used and s2p for 2 port networks This will help when reading back the data files since by default only files with these extensions will be displayed Note Data will be saved with any System Zo conversion applied Note Touchstone is a Trade Mark of Agilent Corporation LA19 13 02 DW96659 iss 1 8 56 of 74 5 6 Loading Data Measured data or data from a circuit simulator can be read into the instrument s memory trace s This can be done by selecting the Load Measurement from the drop down menu under File on the main window The file containing the data in Touchstone format is selected by clicking on the Select Data File button The data will be read from the file and copied to the appropriate display channel s So for example assume the user reads a data file holding full 2 port data Further the user has only two channels on display showing say S11 and S21 so only the S11 and S21 data from the data file read will be copied to the memory traces of the displayed channels Note system impedance conversion will apply if turned on see Fig 5 6 47 Load Touchstone Data Load Data to Memory Select Data File Figure 5 31 Loading data is done from the Load Measurement under the File menu 5 7 Plotting Graphics Plotting the graphics displayed on
64. s measured by the R Reference receiver the other is used for the test stimulus for the DUT Device Under Test In the forward mode the test signal 1s passed through a directional coupler or directional bridge before being applied to the DUT The directional output of the coupler which selects only signals reflected from the input of the DUT is connected to receiver A where the signal s magnitude and phase are measured The rest of the signal the portion that is not reflected from the input passes through the DUT to receiver B where its magnitude and phase are measured The measurements at receivers A and B are referenced to the measurement made by receiver R so that any variations due to the source are removed The reference receiver R also provides a reference for the measurement of phase R A B Receiver Receiver Receiver Reference Test ana signal eens owt Lo fe Pe E ee SS Directional Directional Reverse coupler coupler Fig 3 1 Simplified Vector Network Analyser block diagram In the reverse mode the test signal 1s applied to the output of the DUT and receiver B is used to measure the reflection from the output port of the DUT whilst receiver A is measures the reverse transmission through the DUT 3 3 Measurement Vector network analysers have the capability to measure phase as well as magnitude This is important for fully characterising a device or network either for verifying the performance or for generating
65. s not available on the Pigg and AM to PM utilities Instead the graphics on these can be captured by pressing the ALT and Print Screen buttons The image can then be pasted to the chosen document from the Edit menu 5 9 Signal Generator Utility This utility allows the instrument to act as a CW source The sweep must be stopped first and the control window shown in Fig 5 33 is called from the Utilities menu El Signal Generator Mode e m 4 Frequency and Level Freg MHz Level dB m Hoog 0000 o Apply E sit Figure 5 33 The Signal Generator utility control wndow 5 10 Output Power at the 1 dB Gain Compression Point Utility This utility allows the measurement of the power output at the 1 dB gain compression point of active devices such as amplifiers The utility is started up by going to the drop down menu under Utilities near the top left corner of the main window Piap calibration Calibration minimises errors by removing small variations associated with the instrument s hardware The procedure is simple as shown below e Ensure that an S21 or S11 S21 or 12 term calibration has been carried out e Connect Port 1 to Port 2 as shown on the left hand side of Fig 5 34 e Enter the test frequency and press the Calibrate button LA19 13 02 DW96659 iss 1 8 58 of 74 Piar test The basic connection arrangement is shown on the right hand side of Fig 5 34 Note that the inp
66. ters if required The reason for measuring S parameters 1s that they are made under conditions that are easy to produce at RF Other parameters require the measurement of currents and voltages which is difficult at high frequencies They may also require open circuits or short circuits that can be difficult to achieve at high frequencies and may also be damaging to the device under test or may cause oscillation Forward S parameters are determined by measuring the magnitude and phase of the incident reflected and transmitted signals with the output terminated with a load that is equal to the characteristic impedance of the test system Fig 3 3 LA19 13 02 DW96659 iss 1 8 10 of 74 Forward ay Incident Transmitted b2 Zo Load b Reflected 1 a 0 Reflected Le b Eoad Transmitted ay Incident Reverse reflected Db reflected b 17 2 S Sy oe a 0 incident a incident a transmitted b transmitted b _ aA SS a a 0 Ze incident a incident a Fig 3 3 S Parameters definition The measured parameters are presented in a file similar to the one overleaf It will usually start with a header section that may give some general information such as time and date The header lines start with an exclamation mark There will also be a line that starts with a symbol This line gives information about the format of the data The first field gives the frequency units in this c
67. the LA 19 13 02 VNA this is 333 ns approximately 35 m cable LA19 13 02 DW96659 iss 1 8 21 of 74 4 GETTING STARTED The following flow chart Fig 4 1 illustrates the steps necessary to set up operation of the instrument Start Does your PC have an gt das i Connect VNA Switch ar RS232 connection ntertace to PC VNA on Software Install USB to MN No gt RS232 adaptor driver Run Ul software Fig 4 1 Initial setting up of the VNA 4 1 Minimum Requirements The recommended minimum requirements to operate the VNA are as follows PC or portable PC Pentium 4 1 GHz or equivalent 256 MB of RAM 20 MB of hard disk storage available on the C partition Windows 2000 or XP RS232 port able to operate at 115 2 Kb s or USB port The performance of the User Interface software will be influenced by the performance of the video adaptor installed in the PC It is important that an adaptor with good graphics performance is used As a general guide it is recommended that an adaptor with at least 64 MB of memory is used 4 2 Installation of Optional USB to RS232 Adaptor This step is only necessary if your PC or portable PC does not have an RS232 interface The USB to RS232 adaptor optionally supplied with the instrument is the model US232B LC manufactured by EasySync Ltd http www easysync co uk Installation of the adaptor requires the use of the mini
68. the impulse response is computed the step response may be determined from the time integral of the impulse response In the step response mode the trace is similar to that of a TDR except that there is no step at t 0 When the time domain response is derived from the frequency information the value at t 0 is the impedance of the transmission line or load immediately following the calibration plane The value is referenced to 50 Q the characteristic impedance of the system For example an open circuit would appear as a value of 1 unit relative to the reference value and a short circuit would appear as a value of 1 unit relative to the reference value see example plots in section 5 3 4 In order to facilitate the use of the Inverse Fourier Transform to compute the time domain response the samples in the frequency domain must be harmonically related and consist of 2 points For this reason in order to use the TDR facility in the LA19 13 02 VNA a special 1024 frequency point calibration must be carried out LA19 13 02 DW96659 iss 1 8 20 of 74 covering frequencies from 3 MHz to 3072 MHz The transform returns 2048 points in the time domain giving a time resolution of approximately 162 ps Windowing The bandwidth of the network analyser is limited by the frequency range therefore the frequency domain data will be truncated at the bandwidth of the analyser Also the analyser gathers data at discrete frequencies The result of the sample
69. the main window can be done from the drop down menu under File near the top left corner of the main window A printer set up window will appear from which the desired printer can be chosen and its properties set If required a label can be added to the plotted graphics This can be done by clicking on the Print Save Graphics Label item from the File drop down T Add Label l ioj xj Enter measurement label below Label options SBLP 1 of Filter W Date e Status e Show Preview SBLP 1 of Filter 511 321 Cal F1 Level Odbm Temp 6 0 degC 13 02 2006 Figure 5 32 A label can be added when plotting or saving graphics LA19 13 02 DW96659 iss 1 8 57 of 74 A similar plotting facility exists on the P g and AM to PM utilities control windows as shown in Figs 5 34 and 5 35 5 8 Saving Graphics The graphics shown on the main window Fig 5 1 can be saved in bmp png gif if or Jpg formats This allows measurement results to be directly pasted into most electronic documents The facility to save the graphics can be found on the drop down menu under File near the top left corner of the main window After clicking a dialogue box will appear allowing the user to select the name of the file 1ts location and format from a drop down box As described in the previous section a label can be added by clicking on Print Save Graphics Label item from the File drop down The save graphics facility i
70. ting input and output lines Refer to Section 5 4 for more details Note The reference plane must be at 0 mm for the Auto Ref function to work correctly Also Enhancement window changes only take place when the instrument is sweeping The de embedding facility is explained in detail in section 5 4 The System Zo Conversion facility allows measurements which are always taken in 50Q to be converted to another impedance selected by the user This feature can be useful for example for measuring 75Q devices The value of Zo entered must be real purely resistive and must be within the range of 10Q to 200Q Whenever this facility 1s selected an indicator is displayed on the top right corner of the graphics display as shown in Fig 5 6b Note that when requested impedance conversion will performed on the live measurement and any stored memory trace There are two possible ways of using the System Zo Conversion facility For example 75Q devices can be measured using the techniques illustrated in Fig 5 6a 50Q to 750 matching pads RF cable Connectorised DUT 509 Testjig 75Q DUT Use external matching pads and Calibrate with a 50Q calibration kit use de calibrate with a 75Q calibration kit embedding to remove the test jig and allow mathematical conversion to 75Q impedance Figure 5 6a Possible techniques for measuring 75 Q devices Impedance matching pads can be used to measure a connectorised device A discrete devic
71. tor Consequently the DUT must be an insertable device If this is not the case an adaptor will be needed during the measurement and its effect will need to be removed by either moving the reference plane or by using the de embedding facility as indicated in Table 5 2 When performing just an S21 calibration it is possible to complete the calibration without doing the Isolation calibration Simply click on the Apply Cal button after performing the Through calibration The isolation calibration corrects errors due to crosstalk see section 3 6 and should be carried out when measuring insertion loss values less than 20 dB The terminations to use during the isolation calibration can as a guide be 50 Q loads In some circumstances such as when testing a highly reactive device e g filter beyond cut off a short or an open circuit may be more appropriate or for best results two actual DUTs with 50 Q loads at their unused ports The following notes may be helpful in carrying out a calibration e Connect each standard in turn and click An asterisk will appear once it has been measured e Do not click Apply Cal twice or the procedure may need to be repeated LA19 13 02 DW96659 iss 1 8 43 of 74 Note For best results ensure that the instrument is fully warmed up and that the user interface program on the PC has been running for at least 10 minutes before carrying out a calibration Note Calibration uses a minimum of 16 av
72. use errors in the constellation diagram Time domain reflectometry Time domain reflectometry is a useful technique for measuring the impedance of transmission lines and for determining the position of any discontinuities due to connectors or damage The network analyser can determine the time domain response to a step input from a broad band frequency sweep at harmonically related frequencies An inverse Fourier Transform is performed on the reflected frequency data S to give the impulse response in the time domain The impulse response is then integrated to give the step response Reflected components of the step excitation show the type of discontinuity and the distance from the calibration plane A similar technique is used to derive a TDT Time Domain Transmission signal from the transmitted signal data S21 This can be used to measure the rise time of amplifiers filters and other networks The following provides a more detailed treatment of TDR and TDT Traditional time domain reflectometry TDR The traditional TDR consists of a step source and sampling oscilloscope Fig 3 9 A step signal is generated and applied to a load Depending on the value of the load some of the signal may be reflected back to the source The signals are measured in the time domain by the sampling scope By measuring the ratio of the input voltage to the reflected voltage the impedance of the load can be determined Also by observing the position in ti
73. ut S21 measurments For best results use the arrangement shown on the right Displaying the results The measurement result can be displayed by selecting the S21 parameter and an appropriate display graph and described in Section 5 1 1 Note that the measured phase is relative to the calibration reference plane as discussed in Section 5 4 The reference plane can be shifted at any time from the Enhancement window Note that changes to the reference plane only take place when the instrument is sweeping 5 3 3 Complete 2 port measurement In order to measure all four s parameters a 12 term calibration needs to be completed The arrangement shown on the right hand side of Fig 5 15 is likely to yield best results in terms of repeatability since by virtue of using only one test cable reduces the effects of cable flexing Displaying the results The measurement result can be displayed by selecting a different parameter for each of the possible four display graphs as described in Section 5 1 1 Note that the measured phase is relative to the calibration reference plane as discussed in Section 5 4 The reference plane can be shifted independently for each parameter at any time from the Enhancement window Note that changes to the reference plane only take place when the instrument is sweeping 5 3 4 Group delay Group delay is defined as the rate of change of phase with frequency In relatively non dispersive components such as trans
74. ut and output attenuators should be carefully selected to ensure that the DUT compresses whilst preventing the power at Port 2 of the instrument exceeding the nominal limit of 6 dBm It is recommended that the following guidelines are used to estimate the value of the input and output attenuators needed PiaB pUT GUT Au 5 2 dBm Piasoun Aw 5 lt 6 dBm where P1aBtur Ouput power of DUT at the 1 dB gain compression point Gour Linear Gain of DUT Atti Atm Input and output attenuators Port 1 w Output attenuator attenuator Figure 5 34 Basic connection guide for Pigg measurements Calibration connection 1s shown on the left The instrument makes the measurement by setting the signal source Port 1 frequency to the chosen value and then stepping its power from 20 to 0 dBm in 1 dB steps The gain at each power setting is recorded On completion of the power sweep a second order curve is fitted over a narrow section centred on the point closest to the 1 dB gain compression point The coefficients of this curve allow the actual P g point to be calculated Note Choose the input attenuator with care Ensure that there is no gain compression at the start of the power sweep 20 dBm at Port 1 and that at least 0 7 dB of gain compression is reached at the end of the sweep 0 dBm at Port 1 A will be displayed if insufficient compression has been achieved After the attenuator values have b
75. without the DUT ref plane is here the ref plane to be here to help move the ref plane here Actual device to be tested DUT on microstrip test jig Figure 5 28a Example of S11 measurement requiring reference plane extension Note The Reference Plane extension moves the reference plane for each parameter measurement independently So 1f required for example different values can be used for S11 and S21 A reference plane extension value entered applies to the active channel measurement parameter either reflection or transmission LA19 13 02 DW96659 iss 1 8 53 of 74 In the example above correction was applied to the S11 phase but not S21 An often used way to correct the S21 phase is by using a calibration jig with length of microstrip line equal to the sum of the two sections of line used either side of the DUT jig Fig 5 28b Proceed as follows to make S11 and S21 measurements of the DUT Reference plane extension for S11 correction e Perform a 12 term calibration exclude test jig Ensure that the test cable has connectors of different sex at each end Adaptors may be needed to connect the DUT Connect the input port of the test jig without the DUT mounted on it to Port 1 Display the phase of the S11 on the active display channel Click on the Auto Ref button on the Enhancement window Click on the Apply button on the Enhancement window Normalization for S21 correction e Connect the through microstrip
76. y and the connection to a personal computer for example must be made using a fully shielded null modem cable The cable must have female DB9 connectors at both ends Figure 4 2 below shows the connector and the wiring A suitable cable can be obtained from L Com Connectivity Products http www L com com model number CSNULL9FF 10A for a 3 m long cable and CSNULL9FF 5A for a 1 5 m long cable It 1s recommended that a cable lengths exceeding 3 m 1s not used Figure 4 2 RS232 null modem cable and connector wiring 4 4 USB Operation USB operation can be achieved by using an USB to RS232 converter A suitable converter is optionally supplied with the instrument This is model US232B LC LA19 13 02 DW96659 iss 1 8 23 of 74 manufactured by EasySync Ltd http www easysync co uk In order to use the adaptor the driver software must be installed Use the mini CD ROM supplied with the unit Follow the instructions supplied with the adaptor After successful installation of the adaptor it can be connected to the instrument using the null modem cable supplied After this the UI program can be installed and run Figure 4 3 Optional USB to RS232 adaptor supplied with the instrument 4 5 User Interface Software Installation Follow the instructions written on the CD provided to install the user interface software The procedure will copy the necessary files from the CD ROM to the PC s hard disk and install the executable file A
77. ype on a window display channel End Connect DUT and Sao Tb options start measurement Figure 5 16 Performing a TDR measurement LA19 13 02 DW96659 iss 1 8 47 of 74 Set sweep to 1024 ada ae se Perform S21 Parameter and TD Start points Calibration Hipan gt calibration Graph Type on a window display channel Connect DUT and End start measurement Set up TD options Figure 5 17 Performing a TDT measurement Note that carrying out time domain measurements requires a lot of mathematical processing and therefore each sweep will be noticeably slower when displaying time domain Examples of TDR measurements using the LA19 13 02 VNA The trace below shows the time domain response of a 50 cm 50 Q coaxial cable with an open circuit termination The trace goes to 1 relative to the reference indicating a reflection coefficient of 1 for an open circuit The window used is rectangular o11 TOR gt 000 0 5 WOI 7 0000ns i 7 9 0000 ns Figure 5 18 Measured 50cm line terminated in an open circuit The trace below is the same as above except that the ringing either side of the transition has been reduced by the use of a fifth order Kaiser Bessel window This reduces the ringing but also slows the rise time LA19 13 02 DW96659 iss 1 8 48 of 74 311 TDR gt 0 0 U 0 5 LD 1 0000 ns 4 0000 ns Figure 5 19 Same as shown in Fig 5 15 but using the Kais
78. z to 800 MHz 72 dBc Hz 800 MHz to 1600 MHz 68 dBc Hz gt 1600 MHz Output power accuracy 1 5 dB Reference output level 0 3dBm LA19 13 02 DW96659 iss 1 8 67 of 74 Specifications Sweep type Linear sweep Power sweep Pias utility Sweep speed full 12 term measurement 6 ms point Number of points 51 101 201 401 801 1024 Specifications Resolution bandwidth 6 kHz Averaged displayed noise floor full band 80 dBm max 90 dBm typical 83 dB min Temperature stability 0 02 dB C typical after S21 calibration See Figs 7 1a and 7 16 Trace noise 0 002 dBrms S21 calibration 3 MHz 3 GHz 401 points 128 averages Specifications Load match uncorrected Source match uncorrected Directivity corrected Crosstalk corrected Maximum input level Maximum input level no damage Connectors Specifications Frequency range 3 to 3072 MHz Input power sweep step 1 dB nominal P1dB calculation method 2 order curve fit Display format Graphical gain and output power 0 5 dB typical LA19 13 02 DW96659 iss 1 8 68 of 74 Specifications Frequency Range 3 to 3072 MHz Input power sweep range 20 to 0 dBm Input power sweep step 1 dB nominal AM to PM point calculation method Display format Graphical phase conversion deg dB Accuracy Port 2 power 5 to 20 dBm 1 typical Specifications Frequency range 3 to 3080 MHz 20 to 0

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