Agilent Technologies 8510 User's Manual
Contents
1. User modified cal kits and Agilent 8510 specifications As noted previously the resultant accuracy of the 8510 when used with any calibration kit is depend ent on how well its standards are defined and is verified through measurement of a device with traceable frequency response The published Measurement Specifications for the 8510 Network Analyzer system include calibration with Agilent calibration kits such as the 85050B Measurement calibrations made with user defined or modified calibration kits are not subject to the 8510 performance specifications although a proce dure similar to the standard verification procedure may be used Modification examples Modeling a thru adapter The MODIFY CAL KIT function allows more precise definition of existing standards such as the thru For example when measuring devices with the same sex coaxial connectors a set of thru stan dards to adapt non insertable devices on each end is needed Various techniques are used to cancel the effects of the thru adapters However using the modify cal kit function to make a precise defi nition of the thru enables the 8510 to mathemati cally remove the attenuation and phase shift due to the thru adapter To model correctly a thru of fixed length accurate gauging see OFFSET DELAY and a precise measurement of skin loss attenuation see OFFSET LOSS are required The characteristic impedance of the thru can be found from th2. Agilent e Specifying Calibration 045 Standards for the Agilent 8510 0 eo Network Analyzer o e o Application Note 8510 5B Discontinued Product Information For Support Reference Only Information herein may refer to products services no longer supported We regret any inconvenience caused by obsolete information For the latest information on Agilent s test and measurement products go to www agilent com find products In the US call Agilent Technologies at 1 800 829 4444 any weekday between 8am 5pm in any U S time zone World wide Agilent sales office contact information is available at www agilent com find contactus START 12 490000000 GHz sTUP 18 000000000 GHz as TEES GE Agilent Technologies Known devices called calibration standards provide the measurement reference for net work analyzer error correction This note covers methods for specifying these stan dards and describes the procedures for their use with the Agilent Technologies 8510 net work analyzer The 8510 network analyzer system has the capability to make real time error corrected measurements of components and devices in a variety of transmission media Fundamentally all that is required is a set of known devices standards that can be defined physically or electrically and used to provide a reference for the physical inter face of the test devices Agilent Tec
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4. The phase of the Match does not need to be precisely defined Adapter This class is used to specify the adapters used for the adapter removal process The standard num ber of the adapter or adapters to be characterized is entered into the class assignment Only an esti mate of the adapter s Offset Delay is required within 90 degrees A simple way to estimate the Offset Delay of any adapter would be as fol lows Perform a 1 port calibration Response or S 1 PORT and then connect the adapter to the test port Terminate the adapter with a short cir cuit and then measure the Group Delay If the short circuit is not an offset short the adapter s Offset Delay is simply 2 of the measured delay If the short circuit is offset its delay must be sub tracted from the measured delay Modifying a cal set with connector compensation Connector compensation is a feature that provides for compensation of the discontinuity found at the interface between the test port and a connector The connector here although mechanically com patible is not the same as the connector used for the calibration There are several connector fami lies that have the same characteristic impedance but use a different geometry Examples of such pairs include 3 5 mm 2 92 mm 3 5 mm SMA SMA 2 92 mm 2 4 mm 1 85 mm The interface discontinuity is modeled as a lumped shunt susceptance at the test port refer ence plane The susceptance is generated
5. 0 0108309 ns 9 Enter the loss from Table 1 OFFSET LOSS 0 10 Enter Z from Table 1 OFFSET 2 50 11 Enter the lower cutoff frequency MINIMUM FREQUENCY 9 487 GHz 12 Enter the upper frequency MAXIMUM FRE QUENCY 18 97 GHz 24 13 Select WAVEGUIDE 14 Prepare to label the new standard PRIOR MENU LABEL STANDARD ERASE TITLE 15 Enter PSHORT 1 by using the knob SELECT LETTER soft key and SPACE soft key 16 Complete the title entry by pressing TITLE DONE 17 Complete the standard modification by press ing STANDARD DONE DEFINED Standard 1 has now been defined for a s A P band waveguide offset short To define the remaining standards refer to Table 1 and repeat steps 4 17 To define standard 3 a matched load specify fixed The front panel procedure to implement the class assignments of Table 2 for the P band waveguide cal kit are as follows 1 Prepare to specify a class SPECIFY CLASS 2 Select standard class S A 3 Inform the 8510 to use standard no 1 for the SA class of calibration 1 X1 CLASS DONE SPECIFIED 4 Change the class label for 51 LABEL CLASS 8114 ERASE TITLE 5 Enter the label of PSHORT 1 by using the knob the SELECT soft key and the SPACE soft key 6 Complete the label entry procedure TITLE DONE LABEL DONE Follow a similar procedure to enter the remaining standard classes and labels as shown in the table below Fina
6. 2 997925 10 m s 24925 PS Delay Offset 2 Offset Zo is the characteristic impedance within the offset length For coaxial type offset standards specify the real resistive part of the characteris tic impedance in the transmission media The char acteristic impedance in lossless coaxial transmission media can be calculated from its physical geometry as follows has v u gt 59 9585 4 2 in 2n d Er d relative permeability constant of the medium equal to 1 0 in air relative permittivity constant of the medium equal to 1 000649 in air D inside diameter of outer conductor d outside diameter of inner conductor The 8510 requires that the characteristic imped ance of waveguide transmission line is assigned to be equal to the SET Zo The characteristic impedance of other transmis sion media is not as easily determined through mechanical dimensions Waveguide impedance for example varies as a function of frequency In such cases normalized impedance measurements are typically made When calibrating in waveguide the impedance of a matched load is used as the impedance reference The impedance of this load is matched that of the waveguide across frequency Normalized impedance is achieved by entering SET Zo and OFFSET Zo to 1 ohm for each standard Offset Zo equal to system Zo SET Zo is the assigned convention in the 8510 for matched wave guide impedance Offset loss Of
7. Equation 3 jB I 201 za E R Since Equation 4 Offset loss PH 10 Offset delay E Offset Zo 2 e Jas MM g T a 271 Eg Er 2 1 n For coaxial devices 075a d n 5 2 99792458 x 101 cm s speed of light in vacuum Lj 4nx 10 Henry cm permeability of air D Inner diameter of outer conductor d Outer diameter of center conductor 30 then Equation 5 R Offset loss 1 f 2oL j 2eXOffset Zo N 10 R NEG E t aab A Offset loss f 28 Offset Zo V 10 0 5 Offset delay o 2 Offset Zo 10 Offset delay Offset loss Zo Offset Z 1 j a ee 20 10 Equation 6 for theshort L 2Lo Lif Laf Laf l De j2arctan 022 1 for the open n Cr Co Ci f t Co f C3 P 1 1 j2arctan OC Z If the Offset delay 0 then the coefficient of reflection Ii 31 EI Agilent Email Updates www agilent com find emailupdates Get the latest information on the products and applications you select 9 Agilent Direct www agilent com find agilentdirect Quickly choose and use your test equipment solutions with confidence Agilent Open e www agilent com find open Agilent Open simplifies the process of connecting and programming test systems to help engineers design validate and manufacture electronic prod ucts
8. P SHORT 2 S4C 3 P LOAD ai T S22A P SHORT B S5 2 P SHORT 2 SoC 3 P LOAD T WE T 4 Forward Transmission n THRU Reverse Transmission 4 THRU Forward Match 4 THRU Reverse Match 4 THRU Em Forward Isolation L Reverse Isolation Frequency Response e 4 RESPONSE T TRL Thru TRL Reflect L TRL Line Adapter 1 Forward Isolation Standard is also used for Isolation part of Response and Isolation calibration Table 2 Standard class assignments Modification procedure Calibration kit modification provides the capability to adapt to measurement calibrations in other con nector types or to generate more precise error models from existing kits Provided the appropri ate standards are available cal kit modification can be used to establish a reference plane in the same transmission media as the test devices and at a specified point generally the point of device con nection insertion After calibration the resultant measurement system including any adapters which would reduce system directivity is fully cor rected and the systematic measurement errors are mathematically removed Additionally the modifi cation function allows the user to input more pre cise physical definitions for the standards in a given cal kit The process to modify or create a cal kit consists of the following steps 1 Select standards 2 Define standards 3 Assign classes 4 Enter standards classes 5 V
9. from a capacitance model of the form C209 C4Xf Co X C4x f where f is the frequency The coefficients are pro vided in the default Cal Kits for a number of typi cally used connector pair combinations To add models for other connector types or to change the coefficients for the pairs already defined in a Cal Kit use the Modifying a Calibration Kit proce dure in the Calibrating for System Measurements chapter of the 8510 network analyzer systems Operating and Programming Manual part number 08510 90281 Note that the definitions in the default Cal Kits are additions to the Standard Class Adapter and are Standards of type OPEN Each adapter is specified as a single delay thru standard and up to seven standards numbers can be specified into the adapter class Standard Class labels Standard Class labels are entered to facilitate menu driven calibration A label can be any user selected term which best describes the device or class of devices that the operator should connect Predefined labels exist for each class These labels are Si1A Si B S1C S22A SB S350 FWD TRANS FWD MATCH REV TRANS REV MATCH RESPONSE FWD ISOLATION REV ISOLATION THRU REFLECT LINE and ADAPTER The class labels for the WR 62 waveguide calibra tion kit are as follows 51 and S22A PSHORTI 511 and S 53B PSHORTZ 8 and 822C PLOAD FWD TRANS FWD MATCH REV TRANS and REV MATCH PTHRU and RESPONSE RESPONSE TRL opt
10. function 2 TRL 2 PORT When transmission lines standards are available this method can be used for a com plete 2 port calibration With error correction applied the capacitance of the open can be meas ured directly 3 Gating Use time domain gating to correct the measured response of the open by isolating the reflection due to the open from the source match reflection and signal path leakage directivity Figure 3 shows the time domain response of the open at the end of an airline Measure the gated phase response of the open at the end of an airline and again solve for the capacitance function Sii log MAG REF 0 1 dB 2 10 0 dB V 32 217 ro 1 Figure 3 Time domain response of open at the end of an airline Note In some cases when the phase response is linear with respect to frequency the response of an open can be modeled as an equivalent incremental length A radians 2nf Alength C This method will serve as a first order approxima tion only but can be useful when data or stan dards for the above modeling techniques are not available For the waveguide example this parameter is not addressed since opens cannot be made valid stan dards in waveguide due to the excessive radiation loss and indeterminant phase Short circuit inductance Ly Lz and L If the standard type selected is a short the Lo through Ls coeffici
11. shown in Figure 1 is an example of only one of the measurement calibra tions available with the 8510 The measurement calibration process for the 8510 must be one of seven types RESPONSE RESPONSE amp ISOLATION S 1 PORT S22 1 PORT ONE PATH 2 PORT FULL 2 PORT and TRL 2 PORT Each of these calibration types solves for a different set of the systematic measurement errors A RESPONSE calibration solves for the systematic error term for reflec tion or transmission tracking depending on the S parameter which is activated on the 8510 at the time RESPONSE amp ISOLATION adds correction for crosstalk to a simple RESPONSE calibration An I PORT calibration solves for the forward error terms directivity source match and reflec tion tracking Likewise the S22 1 PORT calibration solves for the same error terms in the reverse direction A ONE PATH 2 PORT calibration solves for all the forward error terms FULL 2 PORT and TRL 2 PORT calibrations include both forward and reverse error terms The type of measurement calibration selected by the user depends on the device to be measured i e 1 port or 2 port device and the extent of accuracy enhancement desired Further a combi nation of calibrations can be used in the measure ment of a particular device The accuracy of subsequent test device measure ments is dependent on the accuracy of the test equipment how well the known devices are mod eled and the exactness of t
12. Figure 2 Standard definition models The mathematical models are developed for each standard in accordance with the standard defini tion parameters provided by the 8510 These stan dard definition parameters are shown in Figure 2 co Each standard is described using the Standard Definition Table in accordance with the 1 or 2 port model The Standard Definition table for a waveguide calibration kit is shown in Table 1 Each standard type short open load thru and arbi trary impedance may be defined by the parame ters as specified below Standard number and standard type Fringing capacitance of an open or inductance of a short specified by a third order polynomial Load arbitrary impedance which is specified as fixed or sliding Terminal resistance of an arbitrary impedance e Offsets which are specified by delay Zo Rioss Frequency range Connector type coaxial or waveguide Label up to 10 alphanumeric characters Standard number calibration kit may contain up to 21 standards See Table 1 The required number of standards will depend on frequency coverage and whether thru adapters are needed for sexed connectors For the WR 62 waveguide example four standards will be sufficient to perform the FULL 2 PORT cali bration Three reflection standards are required and one transmission standard a thru will be suf ficient to complete this calibration kit Standard type A standard type must be c
13. To store calibration kits from the Agilent 8510 onto a disk 1 Insert an initialized calibration data disk into the 8510 network analyzer or connect compatible disk drive to the system bus 2 Press the DISC key select STORAGE IS INTERNAL or EXTERNAL then press the following CRT displayed softkeys STORE CAL KIT 1 2 CAL KIT 1 or CAL KIT 2 This selection determines which of the 8510 non volatile calibration kit regis ters is to be stored FILE _ or FILE NAME Enter the calibration kit data file name STORE FILE 3 Examine directory to verify that file has been stored This completes the sequence to store a cali bration kit onto the disk To generate a new cal kit or modify an existing one either front panel or program controlled entry can be used In this guide procedures have been given to define standards and assign classes This section will list the steps required for front panel entry of the stan dards and appropriate labels 23 Front panel procedure P band waveguide example 1 Prior to modifying or generating a cal kit store one or both of the cal kits in the 8510 s non volatile memory to a disk 2 Select CAL menu MORE 3 Prepare to modify cal kit 2 press MODIFY 2 4 To define a standard press DEFINE STANDARD 5 Enable standard no 1 to be modified press 1 6 Select standard type SHORT 7 Specify an offset SPECIFY OFFSETS 8 Enter the delay from Table 1 OFFSET DELAY
14. also used for Isolation part of Response and Isolation calibration Appendix C Cal coefficients model Offset devices like offset shorts and offset opens can be modeled by the following signal flow graph 1 e op E 1 p p Ap e Gm T e 4 e e Figure 1 Signal flow graph model of offset devices The offset portion of the open or short is modeled as a perfectly uniform lossy air dielectric transmis sion line The expected coefficient of reflection of the open or short then can be solved by signal flow graph technique Equation 1 Uc Pc PP pega pro sTuI p 7 1 209 2 5 1 12 p Prr where p 29 7 Z 50 ZotZ T 1208 Z impedance of short or open LLLP Zo characteristic impedance of the offset transmission line the propagation loss constant of the offset line B the propagation phase constant of the offset line the offset length of the short or open The terms Z and a 36 are related to the cal coefficients Offset Z Offset Loss and Offset Delay as follows Recall that Equation 2 a jB jC distributed resistance of offset line JoL L distributed inductance of offset line Zo G distributed conductance of offset line C distributed capacitance of offset line Q 2nf f frequency R L Lo E 29 Their first order approximations R is small and G 0 are
15. ards or from its actual measured response A standard definition table see Table 1 lists the parameters that are used by the 8510 to specify the mathemati cal model Class assignment Class assignment is the process of organizing cali bration standards into a format which is compati ble with the error models used in measurement calibration A class or group of classes correspond to the seven calibration types used in the 8510 The 17 available classes are identified later in this note see Assign classes CALIBRATION KIT 4 62 TAPE FILE NUMBER co e c2 t3 STANDARD XQ SF 10 27 x10 3 ENS xM SFHD yen op TERMINAL DECRE STD A0 2 T SLIDING nn DELAY 2 LOSS yyy wax WAVEGUIDE LABEL WIPE 10 2 1 1 1 1 SHORT 0 8509 9 987 18 974 wie PHORT T Bl 2 SHORT 32 4925 9967 18 970 WE 3 LOAD FIXED 9 787 8 97 w e P THRU o 9587 694 We n I p SS 1 T L N H L Table 1 Standard definitions table STANDARD CLASS ASSIGMENTS CALIBRATION KIT WAR 62 TAPE FILE NUMBER STANDARD B D F A c E G CLASS LABEL m zl 4 S A P SHORT f B 2
16. asurement calibration requirements for the Agilent 8510B C network analyzer of the capabilities described in this note also apply to the Agilent 8510A with the following exceptions response amp isolation calibra tion short circuit inductance class assignments for forward reverse isolation TRL thru reflect line and options and adapter removal Measurement errors Measurement errors in network analysis can be separated into two categories random and system atic errors Both random and systematic errors are vector quantities Random errors are non repeat able measurement variations and are usually unpredictable Systematic errors are repeatable measurement variations in the test setup Systematic errors include mismatch and leakage signals in the test setup isolation characteristics between the reference and test signal paths and system frequency response In most microwave measurements systematic errors are the most sig nificant source of measurement uncertainty The source of these errors can be attributed to the sig nal separation scheme used PORT 1 PORT2 l REVERSE Szia I Ena Sou Sam Enr 1 Siza 1 1 PORT 2 Figure 1 Agilent 8510 full 2 port error model The systematic errors present in an S parameter measurement can be modeled with a signal flow graph The flowgraph model which is used for error correction in the 8510 for the errors associated with measuring the S parameters of a tw
17. coverage In broadband applications it is often difficult to find stan dards that exhibit a known suitable response over the entire band A set of frequency banded standards of the same type can be selected in order to characterize the full measurement band The TRL 2 PORT calibration requires only a sin gle precision impedance standard a transmis sion line An unknown high reflection device and a thru connection are sufficient to complete this technique Define standards glossary of standard definition parameters used with the Agilent 8510 is included in this section Each parameter is described and appropriate con versions are listed for implementation with the 8510 To illustrate a calibration kit for WR 62 rec tangular waveguide operating frequency range 12 4 to 18 GHz will be defined as shown in Table 1 Subsequent sections will continue to develop this waveguide example i Calibration i plane r a 1 i Ross AA a 1 Cos 1 T 1 boo 1 Zo l OO E RL tdelay t J 1 Model for reflection standard Coax or Waveguide Fixed or Sliding short open load or arbitrary impedance Calibration Calibration Rioss N l i i 2 t delay t l 1 1 Frequency range Model for transmission Coax or Waveguide 3 standard Thru
18. e inner and outer conductor diame ters and the permittivity of the dielectric see OFF SET Zo 22 Modeling an arbitrary impedance standard The arbitrary impedance standard allows the user to model the actual response of any one port pas sive device for use as a calibration standard As previously stated the calibration is mathematically derived by comparing the measured response to the known response which is modeled through the standard definition table However when the known response of a one port standard is not purely reflective short open or perfectly matched load but the response has a fixed real impedance then it can be modeled as an arbitrary impedance A load type standard has an assigned terminal impedance equal to the system Z If a given load has an impedance which is other than the system Zo the load itself will produce a systematic error in solving for the directivity of the measurement sys tem during calibration A portion of the incident signal will be reflected from the mismatched load and sum together with the actual leakage between the reference and test channels within the meas urement system However since this reflection is systematic and predictable provided the terminat ing impedance is known it may be mathematically removed The calibration can be improved if the standard s terminal impedance is entered into the definition table as an arbitrary impedance rather than as a load A procedu
19. e is only specified for arbitrary impedance standards This allows definition of only the real part of the terminating impedance in ohms Selection as the standard type short open or load automatically assigns the termi nal impedance to be 0 or 50 ohms respectively 12 The WR 62 waveguide calibration kit example does not contain an arbitrary impedance standard Offset delay If the standard has electrical length relative to the calibration plane a standard is specified to have an offset delay Offset delay is entered as the one way travel time through an offset that can be obtained from the physical length using propaga tion velocity of light in free space and the appro priate permittivity constant The effective propagation velocity equals TE See Appendix B for a further description of physical offset lengths for sexed connector types ENE Delay seconds precise measurement of offset length in meters 7 relative permittivity 7 1 000649 for coaxial airline or air filled waveguide in standard lab conditions 2 997925 x 108 m s In coaxial transmission line group delay is con stant over frequency In waveguide however group velocity does vary with frequency due to disper sion as a function of the cut off frequency The convention for definition of offset delay in waveguide requires entry of the delay assuming no dispersion For waveguide transmission line the Agile
20. ector type The cali bration plane is defined as a plane which is per pendicular to the axis of the conductor coincident with the outer conductor mating surface This mat ing surface is located at the contact points of the outer conductors of the test port and the calibra tion standard To illustrate this consider the following connector type interfaces 26 7 mm coaxial connector interface The calibration plane is located coincident to both the inner and outer conductor mating sur faces as shown Unique to this connector type is the fact that the inner and outer conductor mating surfaces are located coincident as well as having hermaphroditic sexless connectors In all other coaxial connector families this is not the case 3 5 mm coaxial connector interface The location of the calibration plane in 3 5 mm standards both sexes is located at the outer con ductor mating surface as shown Type N coaxial connector interface The location of the calibration plane in Type N standards is the outer conductor mating surfaces as shown below Note During measurement calibration using the Agilent 85054 Type N Calibration Kit standard labels for the opens and shorts indicate both the stan dard type and the sex of the calibration test port The sex M or F indicates the sex of the test port NOT the sex of the standard The calibration plane in other coaxial types should be defined at one of the conductor interfac
21. ents are specified to model the phase shift caused by the standard s residual inductance as a function of frequency The reflec tion coefficient of an ideal zero length short is 1 at 180 at all frequencies At microwave frequencies however the residual inductance can produce additional phase shift When the inductance is known and repeatable this phase shift can be accounted for during the calibration The inductance as a function of frequency can be modeled by specifying the coefficients of a third order polynomial Lo Li X f L X f La X with units of Lo mH Li 10 H HZz L 10 H HZ and L3 10 H Hz For the waveguide example the inductance of the offset short circuits is negligible Lo through Ls are set equal to zero Fixed or sliding If the standard type is specified to be a load or an arbitrary impedance then it must be specified as fixed or sliding Selection of sliding provides a sub menu in the calibration sequence for multiple slide positions and measurement This enables cal culation of the directivity vector by mathematically eliminating the response due to a non ideal termi nal impedance A further explanation of this tech nique is found in the Measurement Calibration section in the Agilent 8510 Operating and Programming manual The load standard 4 in the WR 62 waveguide cali bration kit is defined as a fixed load Enter FIXED in the table Terminal impedance Terminal impedanc
22. er calibration are not corrected for dispersion Enter WAVEGUIDE into the standard definition table for all four standards Standard labels Labels are entered through the title menu and may contain up to 10 characters Standard Labels are entered to facilitate menu driven calibration Labels that describe and differentiate each stan dard should be used This is especially true for multiple standards of the same type When sexed connector standards are labeled male M or female F the designation refers to the test port connector sex not the connector sex of the standard Further it is recommended that the label include information carried on the standard such as the serial number of the particular standard to avoid confusing multiple standards which are simi lar in appearance The labels for the four standards in the waveguide example are 1 PSHORT1 2 PSHORT2 3 PLOAD and 4 THRU Assign classes In the previous section define standards the characteristics of calibration standards were derived Class assignment organizes these stan dards for computation of the various error models used in calibration The Agilent 8510 requires a fixed number of standard classes to solve for the n terms used in the error models n 1 3 or 12 That is the number of calibration error terms required by the 8510 to characterize the measure ment system 1 Port 2 Port etc equals the num ber of classes utilized Standard Cla
23. erify performance To further illustrate an example waveguide cali bration kit is developed as the general descriptions in MODIFY CAL KIT process are presented Select standards Determine what standards are necessary for cali bration and are available in the transmission media of the test devices Calibration standards are chosen based on the fol lowing criteria A well defined response which is mechanically repeatable and stable over typical ambient tem peratures and conditions The most common coaxial standards are zero electrical length short shielded open and matched load termina tions which ideally have fixed magnitude and broadband phase response Since waveguide open circuits are generally not modelable the types of standards typically used for waveguide calibration are a pair of offset shorts and a fixed or sliding load A unique and distinct frequency response To fully calibrate each test port that is to provide the standards necessary for S or S 1 PORT calibration three standards are required that exhibit distinct phase and or magnitude at each particular frequency within the calibration band For example in coax a zero length short and a perfect shielded open exhibit 180 degree phase separation while a matched load will pro vide 40 to 50 dB magnitude separation from both the short and the open In waveguide a pair of offset shorts of correct length provide phase separation Broadband frequency
24. es to provide an easily veri fied reference for physical length measurements Calibration 7 mm Coaxial connector Calibration plane Male 3 5 mm Calibration plane Female 3 5mm Note 1 0mm 1 85mm and 2 4mm connectors not shown but similar to 3 5mm calibration planes Type N coaxial connector interface The location of the calibration plane in Type N standards is the outer conductor mating surfaces as shown below Calibration Calibration plane plane Female type N Male type N 27 28 CALIBRATION KIT TAPE FILE NUMBER STANDARD co xt 5F ci x10 275 Hz 2 10 35 10 45 23 NO TYPE Lo 10 19 x10 24HjHz Iz 0 33H Hz2 3 X10 H Hz FIXED OR SLIDING TERMINAL IMPEDANCE DFFSET FREQUENCY GHz DELAY ps Loss n Q ey max COAX or WAVEGUIDE STHD LABEL STANDARD CLASS ASSIGMENTS CALIBRATION KIT TAPE FILE NUMBER STANDARD CLASS LABEL 4A S B S4C 5 SB S4C Forward Transmission Reverse Transmission Forward Match Reverse Match Forward Isolation Reverse Isolation Frequency Response TRL Thru TRL Reflect TRL Line Adapter 1 Forward Isolation Standard is
25. fset loss is used to model the magnitude loss due to skin effect of offset coaxial type standards only The value of loss is entered into the standard defi nition table as gigohms second or ohms nanosec ond at 1 GHz The offset loss in gigohms second can be calculat ed from the measured loss at 1 GHz and the physi cal length of the particular standard by the following equation Offset loss 3 Bus 1 GHz C Zo 5 1 GHz 10 log 10 EVE where dBijoss 1 GHz measured insertion loss at 1 GHz Zo offset Zo 7 physical length of the offset The 8510 calculates the skin loss as a function of frequency as follows Offset loss ei Offset loss a X vf GHz S S 1GHz Note For additional information refer to Appendix C For all offset standards including shorts or opens enter the one way skin loss The offset loss in waveguide should always be assigned zero ohms by the 8510 Therefore for the WR 62 waveguide standard defi nition table offset loss of zero ohm sec is entered for all four standards Lower minimum frequency Lower frequency defines the minimum frequency at which the standard is to be used for the purposes of calibration Note When defining coaxial offset standards it may be necessary to use banded offset shorts to specify a single standard class The lower and upper fre quency parameters should be used to indicate the frequency range of desired response It should be noted that lower a
26. gies
27. he error correction model Calibration kit A calibration kit is a set of physical devices called standards Each standard has a precisely known or predictable magnitude and phase response as a function of frequency In order for the 8510 to use the standards of a calibration kit the response of each standard must be mathematically defined and then organized into standard classes which corre spond to the error models used by the 8510 Agilent currently supplies calibration kits with 1 0 mm 85059A 1 85 mm 85058D 2 4 mm 85056A D K 3 5 mm 85052A B C D E 7 mm 85050B C D and Type N 85054B coaxial con nectors To be able to use a particular calibration kit the known characteristics from each standard in the kit must be entered into the 8510 non volatile memory The operating and service manu als for each of the Agilent calibration kits contain the physical characteristics for each standard in the kit and mathematical definitions in the format required by the 8510 Waveguide calibration using the 8510 is possible Calibration in microstrip and other non coaxial media is described in Agilent Product Note 8510 8 Standard definition Standard definition is the process of mathematical ly modeling the electrical characteristics delay attenuation and impedance of each calibration standard These electrical characteristics can be mathematically derived from the physical dimen sions and material of each calibration stand
28. hnologies supplies full calibration kits in 1 0 mm 1 85 mm 2 4 mm 3 5 mm 7 mm and Type N coaxial interfaces The 8510 system can be calibrated in other inter faces such as other coaxial types waveguide and microstrip given good quality stan dards that can be defined The 8510 s built in flexibility for calibration kit definition allows the user to derive a precise set of definitions for a particular set of calibration standards from precise physi cal measurements For example the charac teristic impedance of a matched impedance airline can be defined from its actual physi cal dimensions diameter of outer and inner conductors and electrical characteristics skin depth Although the airline is designed to provide perfect signal transmis sion at the connection interface the dimen sions of individual airlines will vary somewhat resulting in some reflection due to the change in impedance between the test port and the airline By defining the actual impedance of the airline the resultant reflection is characterized and can be removed through measurement calibration The scope of this product note includes a general description of the capabilities of the 8510 to accept new cal kit descriptions via the MODIFY CAL KIT function found in the 8510 CAL menu It does not however describe how to design a set of physical standards The selection and fabrication of appropriate calibration standards is as var ied as the transmission
29. ions When performing a TRL 2 PORT calibration cer tain options may be selected CAL Z is used to specify whether skin effect related impedance vari ation is to be used or not Skin effect in lossy transmission line standards will cause a frequency dependent variation in impedance This variation can be compensated when the skin loss offset loss and the mechanically derived impedance Offset Zo are specified and CAL Zo SYSTEM Zo selected CAL Zo LINE Zo specifies that the imped ance of the line is equal to the Offset Zo at all frequencies 20 The phase reference can be specified by the Thru or Reflect during the TRL 2 PORT calibration SET REF THRU corresponds to a reference plane set by Thru standard or the ratio of the physical lengths of the Thru and Line and SET REF REFLECT cor responds to the Reflect standard LOWBAND FREQUENCY is used to select the mini mum frequency for coaxial TRL calibrations Below this frequency typically 2 to 3 GHz full 2 port calibrations are used Note The resultant calibration is a single cal set combining the TRL and conventional full 2 port calibrations For best results use TRM calibration to cover frequencies below TRL cut off frequency Calibration kit label A calibration kit label is selected to describe the connector type of the devices to be measured If a new label is not generated the calibration kit label for the kit previously contained in that calibration kit registe
30. lassified as a short open load thru or arbitrary impedance The associated models for reflection standards short open load and arbitrary impedance and transmission standards thru are shown in Figure 1 For the WR 62 waveguide calibration kit the four standards are a 1 A and s X offset short a fixed matched load and a thru Standard types are entered into the Standard Definition table under STANDARD NUMBERS 1 through 4 as short short load and thru respectively Open circuit capacitance Co C4 C and C If the standard type selected is an open the Co through coefficients are specified and then used to mathematically model the phase shift caused by fringing capacitance as a function of frequency As a reflection standard an open offers the advantage of broadband frequency coverage while offset shorts cannot be used over more than an octave The reflection coefficient pe je of a perfect zero length open is 1 at 0 for all frequen cies At microwave frequencies however the magni tude and phase of an open are affected by the radiation loss and capacitive fringing fields respectively In coaxial transmission media shield ing techniques are effective in reducing the radia tion loss The magnitude of a zero length open is assigned to be 1 zero radiation loss for all frequencies when using the Agilent 8510 Standard Type open It is not possible to rem
31. lly change the cal kit label as follows 1 Press LABEL KIT ERASE TITLE 2 Enter the title BAND 3 Press TITLE DONE KIT DONE MODIFIED The message KIT SAVED should appear This completes the entire cal kit modification for front panel entry An example of programmed modification over the GPIB bus through an exter nal controller is shown in the Introduction To Programming section of the Operating and Service manual Section III Standard Standard class numbers SaB SC 52 S22B S22C FWD TRANS FWD MATCH REV TRANS REV MATCH RESPONSE PSHORT 2 PLOAD PSHORT 1 PSHORT 2 PLOAD THRU THRU THRU THRU RESPONSE 2 3 1 2 3 4 4 4 4 2 25 Appendix B Dimensional considerations in coaxial connectors This appendix describes dimensional considera tions and required conventions used in determin ing the physical offset length of calibration standards in sexed coaxial connector families Precise measurement of the physical offset length is required to determine the OFFSET DELAY of a given calibration standard The physical offset length of one and two port standards is as follows One port standard Distance between calibration plane and terminating impedance Two port standard Distance between the Port 1 and Port 2 calibration planes The definition location of the calibration plane in a calibration standard is dependent on the geometry and sex of the conn
32. media of the partic ular application and is beyond the scope of this note cO oo gt CO CO amp M3 RO PO BR PO PO PO PO HH HAH AH KH i CO CO CO CO cO 1 HP N e N Table of contents Introduction Measurement errors Measurement calibration Calibration kit Standard definition Class assignment Modification procedure Select standards Define standards Standard number Standard type Open circuit capacitance Co C4 C and Short circuit inductance Lo Li Lz and L3 Fixed or sliding Terminal impedance Offset delay Offset Zo Offset loss Lower minimum frequency Upper maximum frequency Coax or waveguide Standard labels Assign classes Standard classes 5 AB C and S A B C Forward transmission match thru Reverse transmission match thru Isolation Frequency response TRL Thru TRL Reflect TRL Line Adapter Standard class labels TRL options Calibration kit label Enter standards classes Verify performance User modified cal kits and Agilent 8510 specifications Modification examples Modeling a thru adapter Modeling an arbitrary impedance Appendix A Calibration kit entry procedure Appendix B Dimensional considerations in coaxial connectors Appendix C Cal coefficients model Introduction This product note covers me
33. nd upper frequency serve a dual purpose of separating banded standards which comprise a single class as well as defining the over all applicable frequency range over which a cali bration kit may be used In waveguide this must be its lower cut off fre quency of the principal mode of propagation Waveguide cutoff frequencies can be found in most waveguide textbooks The cutoff frequency of the fundamental mode of propagation TE 0 in rectan gular waveguide is defined as follows Ele c 2 997925 x 10 cm sec a inside width of waveguide larger dimension in cm As referenced in offset delay the minimum fre quency is used to compute the dispersion effects in waveguide For the WR 62 waveguide example the lower cutoff frequency is calculated as follows C 2 997925 x 10 cm s 9 487 GHz 2a 2x 1 58 cm c 2 997925 x 10 cm s 1 58 cm The lower cut off frequency of 9 487 GHz is entered into the table for all four WR 62 waveguide standards Upper maximum frequency This specifies the maximum frequency at which the standard is valid In broadband applications a set of banded standards may be necessary to pro vide constant response For example coaxial offset standards i e 1 offset short are generally spec ified over bandwidths of an octave or less Bandwidth specification of standards using mini mum frequency and maximum frequency enables the 8510 to characterize only the specified band d
34. nt 8510 calculates the effects of dispersion as a function of frequency as follows Linear delay V1 feo f Actual delay feo lower cutoff frequency f measurement frequency Note To assure accurate definition of offset delay a physical measurement of offset length is recom mended The actual length of offset shorts will vary by man ufacturer For example the physical length of a 1 offset depends on the center frequency chosen In waveguide this may correspond to the arith metic or geometric mean frequency The arithmetic mean frequency is simply F 2 where and F are minimum and maximum operating frequen cies of the waveguide type The geometric mean frequency is calculated as the square root of F x The corresponding Ag is then calculated from the mean frequency and the cutoff frequency of the waveguide type Fractional wavelength offsets are then specified with respect to this wavelength For the WR 62 calibration kit offset delay is zero for the thru std 4 and the load std 3 To find the offset delay of the s and s offset shorts precise offset length measurements are nec essary For the 1 A offset short 1 3 24605 mm 1 000649 c 2 997925 x 10 m s _ 3 24605 x 10 NT 000649 _ Delay 775997925 x 10 m s pe For the 3 s offset short 9 7377 mm e 1 000649 c 2 997925 x 10 m s 9 7377 x 10 m V1 000649
35. o port device is shown in the figure below The six systematic errors in the forward direction are directivity source match reflection tracking load match transmission tracking and isolation The reverse error model is a mirror image giving a total of 12 errors for two port measurements The process of removing these systematic errors from the network analyzer S parameter measurement is called measurement calibration Epr Epg Directivity Esr Egg Source Match Err Egg Refl Tracking Err Eig Load Match Err Tracking Exp Exg Isolation Measurement calibration more complete definition of measurement cali bration using the 8510 and a description of the error models is included in the 8510 operating and programming manual The basic ideas are summa rized here measurement calibration is a process which mathematically derives the error model for the 8510 This error model is an array of vector coeffi cients used to establish a fixed reference plane of zero phase shift zero magnitude and known impedance The array coefficients are computed by measuring a set of known devices connected at fixed point and solving as the vector difference between the modeled and measured response The array coefficients are computed by measuring a set of known devices connected at a fixed point and solving as the vector difference between the modeled and measured response The full 2 port error model
36. on transmission test sets the device is reversed and is measured in the same manner using the forward transmission calibration 18 The class assignments for the WR 62 waveguide cal kit are as follows The thru Standard 4 is assigned to both REVERSE TRANSMISSION and REVERSE MATCH Isolation Isolation is simply the leakage from port 1 to port 2 internal to the test set To determine the leakage signals crosstalk each port should be terminated with matched loads while measuring S and S The class assignments for forward and reverse iso lation are both loads standard 3 Frequency response Frequency Response is a single class which corre sponds to a one term error correction that charac terizes only the vector frequency response of the test configuration Transmission calibration typi cally uses a thru and reflection calibration typi cally uses either an open or a short Note The Frequency Response calibration is not a sim ple frequency normalization A normalized response is a mathematical comparison between measured data and stored data The important dif ference is that when a standard with non zero phase such as an offset short is remeasured after calibration using Frequency Response the actual phase offset will be displayed but its normalized response would display zero phase offset meas ured response minus stored response Therefore the WR 62 waveguide calibration kit class a
37. ove fringing capacitance but the resultant phase shift can be modeled as a function of frequency using Co through C3 Co Xf Co X f Ca x fwith units of F Hz Co fF C41 10 F HZ Cx 10 F HZ and C3 10 F Hz which are the coefficients for a cubic polynomial that best fits the actual capacitance of the open number of methods can be used to determine the fringing capacitance of an open Three tech niques described here involve a calibrated reflec tion coefficient measurement of an open standard and subsequent calculation of the effective capaci tance The value of fringing capacitance can be cal culated from the measured phase or reactance as a function of frequency as follows AQ tan _ 1 2 2nfX Corr C r effective capacitance A measured phase shift f measurement frequency F farad Z characteristic impedance X measured reactance This equation assumes a zero length open When using an offset open the offset delay must be backed out of the measured phase shift to obtain good through coefficients 10 This capacitance can then be modeled by choosing coefficients to best fit the measured response when measured by either method 3 or 4 below 1 Fully calibrated 1 Port Establish a calibrated reference plane using three independent standards that is 2 sets of banded offset shorts and load Measure the phase response of the open and solve for the capacitance
38. r CAL 1 or CAL 2 will remain The pre defined labels for the two calibration kit registers are Calibration kit 1 Cal 1 Agilent 85050B 7 mm B 1 Calibration kit 2 Cal 2 Agilent 85052B 3 5 mm B 1 Again cal kit labels should be chosen to best describe the calibration devices The B 1 default suffix corresponds to the kit s mechanical revision B and mathematical revision 1 Note To prevent confusion if any standard definitions in a calibration kit are modified but a new kit label is not entered the default label will appear with the last character replaced by a This is not the case if only a class is redefined without changing a standard definition The WR 62 waveguide calibration kit can be labeled simply P BAND Enter standards classes The specifications for the Standard Definition table and Standard Class Assignments table can be entered into the 8510 through front panel menu driven entry or under program control by an exter nal controller The procedure for entry of standard definitions standard labels class assignments class labels and calibration kit label is described in Appendix A Note DO NOT exit the calibration kit modification process without saving the calibration kit defini tions in the appropriate register in the 8510 Failure to save the redefined calibration kit will result in not saving the new definitions and the original definitions for that register will remain Once this process i
39. re similar to that used for measurement of open circuit capacitance see method 8 could be used to make a calibrated measurement of the terminal impedance Appendix A Calibration kit entry procedure Calibration kit specifications can be entered into the Agilent 8510 using the 8510 disk drive a disk drive connected to the system bus by front panel entry or through program control by an external controller Disk procedure This is an important feature since the 8510 can internally store only two calibration kits at one time while multiple calibration kits can be stored on a single disk Below is the generic procedure to load or store cal ibration kits from and to the disk drive or disk interface To load calibration kits from disk into the Agilent 8510 1 Insert the calibration data disk into the 8510 network analyzer or connect compatible disk drive to system bus 2 Press the DISC key select STORAGE IS INTERNAL or EXTERNAL then press the following display softkeys LOAD CAL KIT 1 2 CAL KIT 1 or CAL KIT 2 This selection determines which of the 8510 non volatile registers that the calibration kit will be loaded into FILE or FILE NAME Select the calibration kit data to load LOAD FILE 3 To verify that the correct calibration kit was loaded into the instrument press the CAL key If properly loaded the calibration kit label will be shown under 1 or 2 on the CRT dis play
40. s completed it is recommended that the new calibration kit should be saved on tape Verify performance Once a measurement calibration using a particular calibration kit has been generated its performance should be checked before making device measure ments To check the accuracy that can be obtained using the new calibration kit a device with a well defined frequency response preferably unlike any of the standards used should be measured It is important to note that the verification device must not be one of the calibration standards Calibrated measurement of one of the calibration standards is merely a measure of repeatability A performance check of waveguide calibration kits is often accomplished by measuring a zero length short or a short at the end of a straight section of waveguide The measured response of this device on a polar display should be a dot at 1 Z 180 The deviation from the known is an indication of the accuracy To achieve a more complete verification of a particular measurement calibration including dynamic accuracy accurately known verification standards with a diverse magnitude and phase response should be used NBS traceable or Agilent standards are recommended to achieve verifiable measurement accuracy Further it is recommend ed that verification standards with known but dif ferent phase and magnitude response than any of the calibration standards be used to verify per formance of the 8510 21
41. siness needs Solve problems efficiently and gain a competitive edge by contracting with us for calibration extra cost upgrades out of warranty repairs and onsite education and training as well as design system integration project manage ment and other professional engineering services Experienced Agilent engineers and technicians world wide can help you maximize your productivity optimize the return on investment of your Agilent instruments and systems and obtain dependable measurement accuracy for the life of those products For more information on Agilent Technologies products applications or services please contact your local Agilent office Phone or Fax Korea tel 080 769 0800 fax 080 769 0900 Latin America tel 305 269 7500 Taiwan tel 0800 047 866 fax 0800 286 331 United States tel 800 829 4444 fax 800 829 4433 Canada tel 877 894 4414 fax 800 746 4866 China tel 800 810 0189 fax 800 820 2816 Other Asia Pacific Europe Countries tel 31 20 547 2111 tel 65 6375 8100 Japan fax 65 6755 0042 tel 81 426 56 7832 fax 81 426 56 7840 Email tm_ap agilent com Contacts revised 09 26 05 The complete list is available at www agilent com find contactus Product specifications and descriptions in this document subject to change without notice Agilent Technologies Inc 2001 2004 2006 Printed in USA July 13 2006 5956 4352 Agilent Technolo
42. sses A single Standard Class is a standard or group of up to 7 standards that comprise a single calibra tion step The standards within a single class are assigned to locations A through G as listed on the Class Assignments table It is important to note that a class must be defined over the entire fre quency range that a calibration is made even though several separate standards may be required to cover the full measurement frequency range In the measurement calibration process the order of standard measurement within a given class is not important unless significant frequency overlap exists among the standards used When two stan dards have overlapping frequency bands the last standard to be measured will be used by the 8510 The order of standard measurement between dif ferent classes is not restricted although the 8510 requires that all standards that will be used within a given class are measured before proceeding to the next class Standards are organized into speci fied classes which are defined by a Standards Class Assignment table See Table 2 for the class assignments table for the waveguide calibration kit Siu A B C and Sx A B C S A B C and S A B C correspond to the S and See reflection calibrations for port 1 and port 2 respectively These three classes are used by the Agilent 8510 to solve for the systematic errors directivity source match and reflection tracking The three classes used by the 7 mm cal ki
43. ssignment includes standard 1 standard 2 and standard 4 TRL Thru TRL Thru corresponds to the measurement of the S parameters of a zero length or short thru connec tion between port 1 and port 2 The Thru Reflect and Line classes are used exclusively for the three steps of the TRL 2 PORT calibration Typically a delay thru with zero or the smallest Offset Delay is specified as the TRL Thru standard TRL Reflect TRL Reflect corresponds to the S and S2 meas urement of a highly reflective 1 port device The Reflect typically an open or short circuit must be the same for port 1 and 2 The reflection coeffi cient magnitude of the Reflect should be close to 1 but is not specified The phase of the reflection coefficient need only be approximately specified within 90 degrees TRL Line TRL Line corresponds to the measurement of the S parameters of a short transmission line The impedance of this Line determines the reference impedance for the subsequent error corrected measurements The insertion phase of the Line need not be precisely defined but may not be the same as nor a multiple of pi the phase of the Thru TRM Thru Refer to TRL Thru section TRM Reflec Refer to TRL Reflec section TRM Match TRM Match corresponds to the measurement of the S parameters of a matched load The input reflec tion of this Match determines the reference imped ance for the subsequent error corrected measurements
44. t are labeled short open and loads Loads refers to a group of standards which is required to com plete this standard class A class may include a set of standards of which there is more than one acceptable selection or more than one standard required to calibrate the desired frequency range Table 2 contains the class assignment for the WR 62 waveguide cal kit The A offset short stan dard 1 is assigned to S A The s A offset short standard 2 is assigned to S B The matched load standard 3 is assigned to C Forward transmission match and thru Forward Transmission Match and Thru classes correspond to the forward port 1 to port 2 trans mission and reflection measurement of the delay thru standard in a FULL 2 PORT or ONE PATH 2 PORT calibration During measurement calibration the response of the match standard is used to find the systematic Load Match error term Similarly the response of the thru standard is used to characterize transmission tracking The class assignments for the WR 62 waveguide cal kit are as follows The thru standard 4 is assigned to both FORWARD TRANSMISSION and FORWARD MATCH Reverse transmission match and thru Reverse Transmission Match and Thru classes correspond to the reverse transmission and reflec tion measurement of the delay thru standard For S parameter test sets this is the port 2 to port 1 transmission path For the reflecti
45. uring calibration Further a submenu for banded standards is enabled which requires the user to completely characterize the current measurement frequency range In waveguide this is the upper cutoff frequency for the waveguide class and mode of propagation For the fundamental mode of prop agation in rectangular waveguide the maximum upper cutoff frequency is twice the lower cutoff frequency and can be calculated as follows F upper 2 x F lower The upper frequency of a waveguide standard may also be specified as the maximum operating fre quency as listed in a textbook The MAXIMUM FREQUENCY of the WR 62 wave guide cal kit is 18 974 GHz and is entered into the standard definition table for all four standards Coax or waveguide It is necessary to specify whether the standard selected is coaxial or waveguide Coaxial transmis sion line has a linear phase response as radians m 2nf delay Waveguide transmission line exhibits dispersive phase response as follows radians 2n Ag where Ag A V 1 A Aco Selection of WAVEGUIDE computes offset delay using the dispersive response of rectangular wave guide only as a function of frequency as Linear delay V1 foo f Delay seconds This emphasizes the importance of entering f as the LOWER FREQUENCY Selection of COAXIAL assumes linear response of offset delay Note Mathematical operations on measurements and displayed data aft
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