Specifying Calibration Standards and Kits for Agilent Vector Network
Contents
1. Figure 22 Rectangular waveguide dimensions and properties The physical properties of a rectangular waveguide are illustrated in Figure 22 Anf s entis A wave length in guide medium W 2C 10 13 4 1 r M h Ww effective guide width w 2C 11 Jif uo p pen 2 m resistivity of conductor TM G 5 t V V o i 2w A guide cut off wave length 20 12 C Aa 1 Then oa P gt v speed of light in free space W e 35 36 To structure the waveguide loss equation in calibration coeffcient format for the VNA offset loss must be in G ohm s The equation may be reformulated as follows 1 2h fe ke VP f kl We f 5 20 13 h E Ho a let offset loss EP offset delay The combine propagation constant is 2 3 2C 15 Appendix C2 Derivation of Circular Waveguide Calibration Coefficient Model Figure 23 Circular waveguide dimensions and properties Given the physical properties of a circular waveguide as illustrated by Figure 23 wave length in guide medium p LL bircuilar guide cut off frequency 2m S For H mode x 1 841 l aaa resistivity of conductor G 2 m K 0418514 EG A guide cut off wave length 0 C f f Ao f Then Y YT v speed of light in free space C C2 3 To structure the waveguide loss equation in calibration coefficient format for the VNA2. Figure 11 Example opens and shorts in the same class Four calibration classes are associated with the thru standard measurements namely FWD TRANS FWD MATCH REV TRANS and REV MATCH Except for rare occasions these classes will all contain the same standards the LINK FWD TRANS FWD MATCH REV TRANS and REV MATCH checkbox facilitates the common manipulation for these classes I Link FWD TRANS FWD MATCH REV TRANS and REV MATCH Unchecking the LINK option provides the ability to define different standards for each of these classes This option would be used in the rare case where an external testset may require manipulation between the various measurements of the thru standard In this case assigning different standards for each class will result in a separate prompt during calibration Normally one thru standard would be assigned to the FWD TRANS and FWD MATCH classes and a different thru standard with an identical model would be assigned to the REV TRANS and REV MATCH classes This would result in two separate prompts during the calibration sequence The unknown thru calibration is one of the thru choices of the PNA It does not require a thru standard definition Any two port passive reciprocal device can be used as the unknown thru device low loss device less than 20 dB loss is preferred but not a requirement Adapter class is set up in the 8510 for adapter removal calibration It defines the electri cal d
3. Unselected Standards Selected Standards BROADBAND 3 5 mm male broadbar 1 SHORT M 3 5 mm male short 14 BROADBAND 3 5 mm female broadb 7 SHORT F 3 5 mm female short 4 THRU Insertable thru standar Si lil 2 lt TT Move Up Move Down SS m M The order of the selected standards is used to determine which standard is used when multiple standards are valid at a given frequency Standards listed first have priority OPEN M 3 5 mm male open 15 OPEN F 3 5 mm female open lk l Figure 12 PNA s cal kit editor modify SOLT class screen for 85052D kit 17 Note Nominal accuracy does not correspond to the accuracy of the calibration standards for any particular calibration kit nominal accuracy should simply be considered as a default weighting 18 Traditionally reflection calibrations have been computed using the measured response of three calibration standards at each frequency For port i at each frequency three standards are selected one each from S11 S44B and 514G and used to compute the systematic error terms associated with port i Similarly S3A S55B and S55C are used for port j Each class may include more than one standard the specified minimum and maximum frequency of each standard in the class is used to determine which standard to use for a particular frequency Usually when multiple standards are
4. Data based standards also open the opportunity of enhancing the accuracy of a par ticular calibration kit For example calibration with a broadband load calibration kit is usually less accurate than calibration with either a TRL calibration kit or sliding load calibration kit The main source of degradation is the accuracy of the fixed load model The generic model for a fixed load is that its reflection coefficient is equal to zero at all frequencies As an alternative a fixed load can be characterized using a more accurate calibration The resulting characterization data with uncertainties is used as the data based standard definition of that particular load Figure 8 shows how the data files can be created Figure 9 shows the data entry screen for data based standards Calibrations using the fixed load and its associated data based model will have an accuracy approaching the accuracy of the system that characterized the fixed load The residual directivity error now depends on the uncertainty of the characterization rather than the specification of the load Nominal data based model valid for a particular part number Compute nominal response from nominal dimensions Characterize actual response Data based for a particular _ model valid for a particular standard for example standard a fixed load Figure 8 Nominal vs customized data based file Data Based Standard Ea Identification Standard ID 7 Label Std Descri
5. Select Standards Define the standards Select Assign Classes Enter the standard types and classes Select Name or Rename Kit CON OO FP WN PNA calibration kit entry modification procedure Ele View Channel Sweep Calluabon Trace Scale Marker Stimulus ration Wizard S27 Log Mag 0 0500 Bs 0 000dE 51 2Log Mag 0 050d By 0 00006 Conechon on OFF Interpolation ON off Cal Set Cal Type Cal Set Viewer Port Extensions ECal Confidence Check Charactenze ECal Module Advanced Modify Cal Kit Use the Advance Modify Cal Kit Wizard on the PNA s Calibration pull down menu to create or modify a calibration kit for the PNA Edit PNA Cal Kits Open Save s Restore Default Installed Kits Import Ki Save s Insert New Print to Fie ID KitName Description 1 85 mm Precision Database Cal Kit 85058E Dat 1 85 mm Economy Database Cal Kit 85058BP P 1 85 mm Reduced Accuracy 85058EP P 1 85 mm Economy Reduced Accuracy 850594 1 00 mm Calibration Kit 850564 2 4 mm with sliding load 85056D 2 4 mm Calibration Kit 85056K 2 4 mm with sliding load 850526 3 5 mm with sliding load 85052D 3 5 mm Calibration Kit 85033D E 3 5 mm Calibration Kit 85052C 3 5 mm SOLT TAL Calibration Kit Edtkit Delete v Cancel Help The PNA s built in cal kit editor will show a list of all cal kits files currently available and can be selected f
6. 35 Appendix D Data based Calibration Standard Definition File Format 39 Panne EE EE q Eu Ee RT NER E MURS 39 Preliminary PNA keywords srorvrvrnrrvenvrvervrvenervenrerervrvervsvenrererssnesveverseversenesvenessevesvesennen 40 Relerentes orna ne on nO 41 Web Resources ettet tnnt tentent 42 Introduction Measurement errors Measurement errors in network analysis can be separated into two categories random and systematic errors Both random and systematic errors are vector quantities Random errors are non repeatable measurement variations and are usually unpredictable Systematic errors are repeatable measurement variations in the test setup Systematic errors include impedance mismatch system frequency response and leakage signals in the test setup In most microwave measurements systematic errors are the most significant source of measurement uncertainty The source of these errors can be attributed to the signal separation scheme used Numerous publications are available on vector network analyzer VNA calibration techniques References 1 2 3 4 5 6 7 and 8 are just some of the pub lished work Agilent s application notes 1287 1 1287 2 and 1287 3 also provide insights on VNAs and VNA error correction It is recommended that a user be familiar with these calibration techniques and terminologies to get the maximum understanding from this application note Measurement calibratio
7. 4 both known on port i and port j and j 44 S99 0 Defined attenuator Phase approximately as lossy line known The generalized TRL algorithm assumes the characteristic impedance of the line stan dard equals the desired system characteristic impedance The calibration reference Z9 option allows for adjustments to the calibration to account for small perturbations between the system Zg and the line characteristic impedance Z This is derived from the defined Offset Z and Offset Loss terms See equation 2B 5 in Appendix B on page 32 If line Zg is selected no adjustments are made Caution Do not select System Zp If offset Zo of the line or match standard is very different from system Zp TRL calibration is computed initially at a reference plane that corresponds to the middle of the thru In this case the line standard can be assumed to be the portion of the line standard left over after subtracting a length equal to the length of the thru standard After the error coefficients are computed they are adjusted to establish a testport refer ence plane based on either the model of the thru standard or the model of the reflect standard When selecting the reflect standard to set the testport reference plane the assumption is that the reflect standard is precisely known as both magnitude and phase of the reflect standard will be used to compute the testport reference plane Selecting the thru standard to set the reference plane obvious
8. 8510 requires that all standards that will be used within a given class are measured before proceeding to the next class Multiport calibrations use a series of one port and two port calibration standards and are comprised of a series of two port SOLT and or TRL calibrations 15 16 SOLT class assignment In the simplest case an SOLT calibration consists of two one port calibrations followed by forward and reverse transmission and reflection measurements on a thru standard The thru standard can be a defined thru or an unknown thru The simplest thru standard is a zero length thru which is simply the connection of port i to port j Selecting the radio button corresponding to a particular class enables modification of both the standards included in the class and a user defined label associated with the class The user defined class label is visible during unguided calibration on the PNA Each one port calibration requires reflection measurements on at least three known and distinct standards S11A S B and S C represent the three reflection standard classes for port i while SA S55B and S55C represent the three reflection standard classes for port j Most of the time A and S A have the same standards B and S5 B have the same standards and S C and S C have the same standards The standards assigned to each class may have different connector definitions different frequency coverage and different standard types Some calibration k
9. LAL line auto characterization LINE standard is Reference plane a match standard set by THRU standard definition LINE standard is a Reference plane set from Reference plane Reference plane delay line with defined estimated LINE propagation set by THRU set by REFLECT offset Zg EQUAL to constant and specified standard definition standard definition defined offset Zp delays of THRU and of THRU standard LINE standards LINE standard is a Reference plane delay line with defined set by THRU offset Zo NOT EQUAL standard definition to defined offset Zo of THRU standard 21 Modification Procedure Note Calibration kit entry and modification procedures for the Agilent ENA series of net work analyzers are well documented in the Calibration Chapter of the ENA User s Guide therefore they are not covered in this document 22 Calibration kit modification provides the capability to adapt to measurement calibra tions to other connector types Provided the appropriate standards are available cal kit modification can be used to establish a reference plane in the same transmission media as the test devices Additionally the modification function allows the user to input more precise physical definitions for the standards in a given cal kit The process to modify or create a cal kit consists of the following steps Select Modify Cal Kit Select Kit Import Kit or Create New Define the connector s coax waveguide etc
10. Standard ID D Label MESEN Load Description aPC 7 offset load Frequency Range Min 1990 MHz Max 20010 MHz Load Type eonninles Impedance Heal 50 mag lo Delay Eharatteneshcs Delay fo piet Loss lo Epor zi Sas hints Offset Load Definition First Offset Standard THRU Second Offset Standard LINE aad Standard BROADBAND Arbitrary C Fixed Load C Impedance Sliding Load Offset Load Clear ox Cancel Apply Help Figure 6 PNA offset load entry screen An offset load can be considered a compound standard consisting of 2 known offsets transmission lines of different length and a load element Figure 6 The definition of the offsets is the same as all offset transmission lines The shorter of the two off sets can be a zero length offset The load element is defined as a one port reflection standard An offset load standard is used when the response of the offset standards is known more precisely than the response of the load element Measurement of an offset load standard consists of two measurements one with each offset terminated by the load element The frequency range of the offset load standard should be set so that there will be at least a 20 degree separation between the expected response of each measurement In cases where more than two offsets are used the frequency range may be extended as the internal algorithm at each frequency will search through all of the p
11. a least squares approach is applied to calibrations using other calibration kits due to the physical property differences of the standards Expanded math is a weighted least squares solution approach that provides a simple solution to handle the case where the observations are not all trusted to the same degree 12 If the observations are all independent but not equally trusted an optimal solution is best obtained by multiplying each equation by a weighting factor that includes both the accuracy of the standard s model and the proximity of the standard s response to the response of the other measured calibration standards The accuracy of the standard model is explicitly defined for data based standards for the other stan dards a nominal accuracy is assigned to provide a relative weighting for the weighted least squares solution Table 2 Default relative accuracy of cal standards types The measurement of a standard is included in the weighted least squares solution over the frequency range where the accuracy of the standard is defined this frequency range is greater than or equal to the frequency range where the standard is selected specified by the min max frequencies To avoid confusion in the following table FMin and FMax cor respond to the minimum and maximum frequency specified for the standard while UMin and UMax correspond to the minimum and maximum connector frequency Also in the following table endpoints are given nominal accuracy at
12. calibration plane Calibration plane Female type N Figure 19 Type N connector calibration plane Calibration plane Male 3 5 mm Calibration plane Male type N 31 32 Appendix B Derivation of Coaxial Calibration Coefficient Model Figure 20 Coaxial transmission line characteristics All transmission lines may be defined by their characteristic impedance Zc propaga tion loss constant a propagation phase constant 5 and length They are related to the calibration coefficients Offset Zp Offset Loss and Offset Delay as follows Recall that Transmission loss and phase a j B z J R joL G 4 joC 2 1 Z J R joL G joC distributed resistance offset line distributed inductance offset line distributed conductance offset line distributed capacitance offset line S QQ Rew I 27f f frequency in Hz I length Assume that R is small and G 0 including the self inductance of imperfect conductors the second order approximation of the transmission line characteristics are 2B 2 Epp cg 00 a j B JjJ yL C 1 1 3 ea 20L Z E h a 3 SA o For coaxial transmission lines let 2B 3 Kv Je f 10 Offsetloss Lye Offset delay ve SE V R PM o ind xD Given L 5 in Gu poc 2B 4 27 d In D d Uy Offset Z LM HoV n VC ane d Substituting the offset definitions back to the transmission l
13. ckt OML WR 05 ckt CK 35MME 1 ji EA CK 292MM A1 CK NTYPA O My Computer E CK_NTYPB 2 CK NTYPD 2 CK 35MMB M My Network Places File name Al Files vi Cancel PNACalkit Files ckt PNACalkit Version 1 Files ck1 8510 Files ck AF Aw Pe Files ck Files of type Cal Kits can be imported from other directories the disc drive or the USB drive Almost all previous versions of network analyzer data files can be imported Some user created 8510 cal kit files and 87xx cal kit files may not import properly Check the kit s content after download to make sure all data entries are correct Note that PNA versions of all the Agilent 8510 calibration kits were pre installed in the factory cal kit directory 23 dentification Kit Number 18 Kit Mame Kit Description Connectors Class Assignments Description amp d sor Edi Family Famil BRenge tanny man mn Add Edit Delete Delete Al DE Cancel Help To set up a new kit the connector family must be defined before adding calibration standards Any changes to the connector definition must also be performed before editing the calibration standards Add or Edit Connector Identification Connector Family Corrector Undetned Gender Male Female Description Frequency Range Min jo MHz No Gender ned ee 0 50 ohm Cutof
14. for a 1 8 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 44A 3 Direct the network analyzer to use standard no 1 for the 11A class of calibration I X1 CLASS DONE SPECIFIED Change the class label for S11A LABEL CLASS A ERASE TITLE 1 Enter the label of PSHORT 1 by using the knob the SELEGT softkey and the SPACE softkey 2 Complete the label entry procedure TITLE DONE gt LABEL DONE Follow a similar procedure to enter the remaining standard classes and labels as shown in the table below Finally change the cal kit label as follows 1 Press LABEL KIT gt ERASE TITLE 2 Enter the title P BAND 3 Press TITLE DONE gt KIT DONE MODIFIED The message CAL 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 external controller is shown in the Introduction To Programming section of the 8570 Network Analyzer Operating and Service Manual Section III Table 6 8510 class assignment table Standard class Standard numbers Class label S4B 2 PSHORT 2 SC 3 PLOAD S55A 1 PSHORTI S B 2 PSH
15. line auto characterization 19 20 65050C Modify TRE Calibration Class Assignments Calibration Kit Class 4 Calibration Reference 20 ie TAL THRU C ISOLATION SYSTEM ZO LINE 20 Testport Reference Flane Cancel C TAL LIME MATCH f THAU STANDARD C REFLECT STANDARD Help Calibration Class Label TRL THRU THRU C TRL REFLECT LRL line auta characterization Selected Standards Description Description OFFSET LOAD APC 7 offset load Inzertable thru standar LOWBAND LO APC 7 lewband load gt BROADBAND APC 7 broadband loac OPEN APC 7 open SHORT APC F short LIME 2 18 line standard Unselected Standards Move Up Move Down The order of the selected standards is used to determine which standard is used when multiple standards are valid at given frequency Standards listed first have priority Figure 13 TRL edit class screen TRL is a generic name that represents a class of calibrations that allow partially known calibration standards to be used In general the thru standard is assumed to be fully known with perfect match the reflect standard is assumed to have a high reflection with unknown amplitude and partially known phase The line standard is assumed to have the same propagation characteristics as the thru standard with partially known phase Table 4 provides a mapping of specific calibration types to the TRL class Table 4 Mapp
16. load activates the Offset Load Definition field The Thru Line Adapter edit entry screen is activated by choos ing the thru standard type Note that connectors need to be defined for both ports They can be used to define an adapter Data Based Standard 85050B Modify SOLT Calibration Class Assignments e SREY TRANS PAD MATICA REV MATCH 2 LOWBAND LO APC 7 lowband load SLIDING LOAD APC 7 sliding load BROADBAND APC7 broadband loac After all the standards are defined They need to be assigned to classes Class assignment details were discussed earlier in this application note Use Browse to locate the data based file and upload it If successful the file information screen will summarize the file s The final step is to complete the kit description and save the kit content File information is only available at initial installation Subsequent viewing of an existing standard is not yet supported Figure 17 Complete standard definitions and assign to classes 26 8510 Calibration kit modification entry procedure Calibration kit specifications can be entered into the Agilent 8510 vector network ana lyzer using the 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 only store two calibration kits internally at one time while multiple calibration kits can be s
17. of Calibration Standards by Physical Measurements 39th ARFTG Conference Digest N Marcuvitz 1986 Waveguide Handbook McGraw Hill NY 1955 Reprint Peter Peregrinus Lt G Strang 1980 Linear Algebra and Its Applications 2nd ed New York New York Academic Press Inc D J Bannister E J Griffin T E Hodgetts Sep 1989 On the Dimensional Tolerances of Rectangular Waveguide for Reflectometry at Millimetric Wavelengths NPL Report DES 95 N Marcuvitz 1986 Waveguide Handbook Sec 2 3 IEE Electromagnetic Waves Series 21 Peter Peregrinus Ltd 41 Web Resources For additional literature and the latest product information visit our Web sites PNA series network analyzers www agilent com find pna 8510 network analyzers www agilent com find 8510 Electronic Calibration Modules ECal www agilent com find ecal at Agilent Email Updates www agilent com find emailupdates Get the latest information on the products and applications you select LXI 0 9001 2008 C www Ixistandard org www agilent com quality LXI is the LAN based successor to GPIB providing faster more efficient connectivity Agilent is a founding member of the LXI consortium Agilent Channel Partners wwwagilent com find channelpartners Get the best of both worlds Agilent s measurement expertise and product breadth combined with channel partner convenience www agilent com For more information on Agi
18. 60101 COMMENT SERIAL NUMBER NOMINAL HPNA STDREV Rev A 01 00 HPNA STDLABEL SHORT 1 M HPNA STDDESC 1 85 mm male SHORT 1 HPNA STDFROMIN 0 HPNA STDFROMAX 70000000000 HPNA STDNUMPORTS 1 COMMENT 1 85 mm known so PNA DEFINECONNECTOR statement non needed COMMENT PNA DEFINECONNECTOR 1 85 mm 0 70000000000 COAX HPNA CONNECTOR 1 1 85 mm MALE COMMENT PINDEPTH is optional only applies to coax devices HPNA PINDEPTH 1 0 007 0 007 NAME DATA COMMENT This section describes the s parameter data and weighting COMMENT factor for the calibration standard COMMENT COVERAGEFACTOR is used to scale the weighting factor COMMENT S ij is sij for the standard Supported formats RI COMMENT U i j is the weighting factor for sij COMMENT Supported U i j formats RI MAG HPNA COVERAGEFACTOR 2 COMMENT note number of points is 509 below VAR Freq MAG 509 DATA S 1 1 RI DATA U 1 1 MAG VAR LIST BEGIN 0 10000000 15000000 70000000000 VAR_LIST_END BEGIN 1 0 0 99976354927 0 00249289367 0 99970950119 0 00367766097 0 9772034982 0 14575300423 END BEGIN 0 00028 0 00028 0 00028 0 005 END 39 40 Preliminary PNA keywords The PNA currently does not recognize the following keywords they are ignored Future revisions will include the following keywords to allow the data based standard to be completely defined by the CITIFILE Table 7 PNA keyword table preliminary Statement HPNA REV s HPNA S
19. ORT2 Sool 3 PLOAD FWD TRANS 4 THRU FWD MATCH 4 THRU REV TRANS 4 THRU REV MATCH 4 THRU RESPONSE 1 2 4 RESPONSE 29 Appendix A Dimensional Considerations in Coaxial Connectors 30 This appendix describes dimensional considerations and required conventions used to determine 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 connector type The calibration plane is defined as a plane which is perpendicular to the axis of the conductor coincident with the outer conductor mating surface This mating surface is located at the contact points of the outer conductors of the test port and the calibration standard To illustrate this consider the following connector type interfaces 7 mm coaxial connector interface The calibration plane is located coincident to both the inner and outer conductor mating surfaces as shown in Figure 18 Unique to this connector type is the fact that the inner and outer conductor matin
20. Specifying Calibration Standards and Kits for Agilent Vector Network Analyzers Application Note 1287 11 Nan EE DOCE DOCE OCEM occe L ge e8 OG 886 SES seo se ec ee Ja H E B B D BeBe eoe C i f e OG mE amp T A t mp Tik fei Bi Re Oe 30018 C ECC 8 e ninm 9 0000 AES Agilent Technologies Table of Contents Moen RC RR Tc 3 Meles pPRRd v rri vsa ROTE PERI daiiran asarini iiien 3 Measurement calibration ammes rt dri a unt E m vv Gv 3 EET Ug DUET CR A A 4 Eee D Calibration standards definition srosnsnenvnrenvrrenrrvenverenrrvervnvervevervevervenervevervenervenesvenssvesenne 6 Class ASS IVC EE eit electi vt EDUC eR iE vede 14 Modification Procedure esses 22 PNA calibration kit entry modification procedure sene 23 8510 Calibration kit modification entry procedure enne 2 Appendix A Dimensional Considerations in Coaxial Connectors 30 7 MM coaxial connector interface essetis 30 3 5 mm 2 4 mm 1 85 mm 1 0 mm coaxial connector interface 30 Type N coaxial connector interface sese 31 Appendix B Derivation of Coaxial Calibration Coefficient Model 32 Appendix C1 Derivation of Waveguide Calibration Coefficient Model
21. TDTYPE s HPNA STDREV s HPNA STDLABEL s HPNA STDDESC s HPNA STDFROMIN f HPNA STDFROMAX f HPNA STDNUMPORTS d HPNA PINDEPTH d f1 f2 HPNA DEFINECONNECTOR s1 f1 f2 52 f PNA CONNECTOR d s1 s2 PNA COVERAGEFACTOR f Explanation PNA revision Calibration standard type s can be DATABASED Standard revision Standard label Standard description Min frequency for standard selection may be different from range of use Hz Max frequency for standard selection may be different from range of use Hz Number of ports default 1 Indicates pin depth for coaxial connectors to allow for pin depth compensation to the model d port number f1 value included in the model data mm f2 actual value mm Defines connector NOT NEEDED IF PREDEFINED s1 connector ID f1 minimum frequency Hz f2 maximum frequency Hz s2 connector type can be COAX WAVEGUIDE lt f gt is an optional list of parameters to specify values needed for connector type f is ignored for COAX f the first element is cutoff frequency for WAVEGUIDE f to be determined for other types Connector assignment d port number s1 connector ID corresponding to predefined ID or one defined by DEFINECONNECTOR s2 connector sex can be MALE FEMALE NONE Coverage factor for weighting default f 1 References 14 D Rytting Mar 1987 An Analysis of Vector Measurement Accuracy Enhancement Techniques Hewlett Packard RF amp Micr
22. THRU Inzertable thru standard b LIME 2 18 line standard B DSHORT Dummy SHart I Delete Delete Al OF Cancel Help This shows the effect of a connector family name change from APC 7 to 7mm Next press the Add button to add the standards Add Standard Add any one of the supported standard types If open is select ed the open edit screen will appear as shown on the right The short standard edit screen is very similar to the open s The load standard edit screen is shown below LOWBAND LOAD APC lowband load Soni ER io weal as imag Bee eat Enter Pelee Are rainin zifn second Tee STETIT Er sadis tanaan There are 4 load types Each activates a different set of data entry fields Fixed and sliding loads are similar Figure 16 Add standards ooe Ee open 999000 MH co 90 4733 Fie E1 763 303 C2 63 8176 Ele GHz C3 6 4337 Fle 45J Hz 3 Enter all the fields Make sure the units of measurements such as the exponents are correct bel ARES Mise inad DEnHEN ae anse stannas second B Enea cire spe cad Standard Note Arbitrary impedance activates the complex impedance entry field 25 Thru Line Adapter bel ET standard ID E bel LINE oo Bm offset load Thru Descripti 2 18 line standard EGIT dene f Fixed Loa Impedance Heal 9liding Ede s mag ht aS Sooo RISE Disi zu el Arne Offset
23. a given frequency is computed as a linear interpolation between the appropriate endpoints Table 2 Default relative accuracy of cal standards types Standard Frequency range Open 0 01 UMax 1012 Minimum connector Maximum connector frequency frequency Short 0 005 UMax 1013 Minimum connector Maximum connector frequency frequency Fixed load 0 003 3 UMax 1012 Minimum connector Maximum connector frequency frequency Sliding load 0 01 0 003 0 003 FMin 2 Maximum connector frequency When use expanded math when possible is checked the solution at each frequency all of the measured one port standards will be included in the solution if frequency falls between UMin and UMax For example consider a sliding load calibration that includes frequencies in both the low band load and sliding load frequency ranges The open short low band load and sliding load will be measured At each frequency between UMin and UMax of the sliding load the computation will use expanded math Using expanded math in this case will blend the transition between the low band load frequency range and the sliding load frequency range As another example the 85058B 1 85 mm calibration kit has a low band load an open and a series of short standards with varying offsets There is a minimal set of standards defined that would insure calibration with three standards is possible at each frequency The minimum and maximum frequency ranges for each standard combined with the class ass
24. age 10 A DATA BASED STANDARD is defined by a data file See Appendix D on page 37 for the requirements and format of data files Calibrations and class assignments Assigning standards to class Calibration kits can be created to support SOLT calibrations TRL calibrations or both Class assignments are a way for the calibration kit file to guide the selection of stan dards during the calibration process When assigning standards to a class for the PNA SmartCal guided cal the order in which the standards appear indicates the default preference for the calibration kit As the internal PNA firmware searches for the appropriate calibration standard to use at a given frequency it starts at the top of the list and searches until it finds a standard that can be used at that frequency For this reason it is important to list the preferred standards first For example a calibration kit that includes a sliding load usually also includes a broadband load if the broadband load is listed before the sliding load the sliding load will not come up as a default selection For the 8510 and its derivatives 87xy and unguided cal of the PNA the order of standard assignment within a given class is not important The order of the standard measurements is important When two standards have overlapping frequency bands the last standard to be measured will be used The order of standard measurement between different classes is not restricted although the
25. ay be represented by a signal flow graph as illustrated in Figure 4 Figure 4 Signal flow graph of terminated transmission line model Figure 5 shows the same terminated transmission line model in cascade parameter format define XI and Xo Figure 5 Cascade parameter representation of terminated transmission line model Where Z 4 AZ 4 1 1 y D 2 Zet 4 AT t4 y a jB 1 length of line Ty Z characteristic impedance of line Z r Q propagation loss constant of line reference impedance connector impedance or system impedance D propagation phase constant of line al Ur ers Tolir 1 2 mal Le Yi pg M 13 1 1 tT 1 0 e 1 1 i mol p r 1 e e Ty 1 4 T 1 it r e r r 1 e Transmission line characteristic impedance and propagation constants can be derived from the line s physical properties 9 10 Agilent s VNA uses offset delay offset loss and offset Zg instead of Z and yl to model the transmission line With these offset definitions the VNA can compute the trans mission line s characteristic impedance and propagation phase and loss constants of the calibration standard without defining the dielectric constant of the calibration stan dard s transmission medium which may be different from that of the device under test This assumes that the offset loss and offset delay values were derived using the same dielectric constan
26. be necessary to optimize the accu racy of the standard model for a given frequency band and or calibration requirement For the 8510 VNA a calibration kit may contain up to 21 standards There is no limit on the PNA SmartCal guided cal The required number of standards will depend on frequency coverage and calibration methods supported A single standard class is a standard or group of up to 7 for most VNA standards that comprise a single calibration step The standards within a single class are assigned to locations A through G as listed in the Class Assignments table It is important to note that each and every class must be defined over the entire frequency range for which the calibration is made even though several separate standards may be required to cover the full measurement frequency range Not all VNAs support the same set of calibration methods and calibration kits Check the instrument s documentation for its capabilities The following sections provide detailed descriptions of the various VNA class assignment structures VNA calibrations are test port specific and therefore class assignments are structured around port numbers Since only 1 port and 2 port calibration standards are available calibration kit class assignments are 2 port based only one port pair can be calibrated at a time Standard types Calibration standards are assigned to the following standard types Figure 10 OPEN SHORT LOAD THRU ADAPTER 8510 an
27. ctor Figure 2 Frequency Range Gender male female no gender Impedance Media coax waveguide etc Cutoff Frequency waveguide Height Width Ratio waveguide Add or Edit Connector E3 Identification Connector Family Pene EERIE Description band waveguide Frequency Hange Min 5555 MHz Max 13111 MHz WAVEGUIDE Cutott Frequency E555 MHz Height width Ratio 0 5 Cancel Apply Help Figure 2 PNA connector entry screen A calibration kit may be defined with multiple connectors Each 1 port calibration standard must be associated with a defined connector Two port standards such as thrus and adapters may be associated with two different defined connectors Calibration standards definition The S parameters of VNA calibration standards must be defined sufficiently and accu rately to satisfy the requirements of the calibration methods for which they will be used Calibration standards may be defined in various ways Agilent s VNAs support two types of calibration standard definitions calibration coefficient model and data based model Calibration coefficient model The majority of VNAs define calibration standards by using a transmission line model for 2 port standards and a terminated transmission line model for 1 port standards See Figure 3 Transmission line Zc delay loss Figure 3 Terminated transmission line model The transmission line and termination m
28. d DATA BASED STANDARD PNA Add Standard Select the type of standard to be added OPEN C SHORT C LOAD Cancel Help Figure 10 Calibration standard selections An OPEN calibration standard assumes that the polynomial coefficients represent a capacitance model and computes its reflection coefficients according to equation 1 13 The VNA assumes that each capacitance coefficient is scaled to a default exponent CO sxx xxxl0 F C2 sxx xxx1 0 9F Hz s sign or C1 sxx xxx10 F Hz C3 sxx xxxxl0 PF Hz 1 15 All Agilent VNA models use the same scaling factor A SHORT calibration standard assumes that the polynomial coefficients represent an inductance model and computes its reflection coefficients according to equation 1 12 The default exponents for inductance terms are LO sxxxxx10 H L2 sxx xxx10 gt H Hz s sign or Ll sxxxxx10 H Hz L3 sxx xxxxl0 H Hz 1 16 Four types of LOAD standards are available a fixed load sliding load arbitrary imped ance and offset load The default setting for fixed load is delay 0 loss 0 and Z0 50 ohms a perfect termination A sliding load triggers prompts for multiple slide position ing and measurements minimum of 6 slide positions is recommended Arbitrary impedance requires a terminating impedance entry a real value only for most VNA and complex value for the PNA Offset load requirements are explained in the Terminating Device section on p
29. e 35 for details 2 f 111 B1 2nf offset dday 1 5 1 11 f waveguide cut off frequency 0 1 offset loss offset Nd E JI PT Waveguide impedance 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 to that of the waveguide characteristic impedance across the guide s frequency bandwidth Normalized impedance is achieved by setting OFFSET Zg to 1 ohm for each standard and setting system Zg SET Zp to 1 ohm 10 Terminating devices Short Many vector network analyzers assume that the short is an ideal short and has a reflection coefficient of 1 This may be adequate at low frequencies and for large connector sizes such as 7 mm and larger However at higher frequencies and for small er connectors 3 5 mm and smaller at least a third order polynomial inductance model Ls is required Loss of the short circuit is assumed to be insignificant Ls L L f Lyf Lsf Zs j2nfLg 1 12 Zs 4 a Zgs t4 In some cases when the phase response is linear with respect to frequency the response of a short can be modeled as an equivalent incremental length Open Open circuits radiate at high frequencies This effectively increases the electrical length of the device and can be modeled as a frequency dependent capacit
30. elay of the adapter in order to determine the correct 511 and S response of the adapter The delay value need not to be very accurate However the correct phase within 90 for all the measurement frequency points must be provided A class assignment table is a very useful tool to help organize calibration standard assign ments for data entry All calibration kit operating and service manuals provide examples and blank forms of assignment tables Compare the SOLT class assignment table Table 1 with the PNA s cal kit editor SOLT class assignment edit screen Figure 12 to see the mapping relationships The SOLT class assignment table maps directly into the 8510 s modify cal kit class entry format Table 1 SOLT class assignment table for the 85052D kit CLASS A B C D E F G Class Label S441 2 15 Open S41B 1 Short S416 3 14 Load SA 2 15 Open 22B 1 Short S996 3 14 Load Forward transmission 4 4 4 Thru Reverse transmission 4 4 4 Thru Forward match 4 4 4 Thru Reverse match 4 4 4 Thru Adapter 15 Adapter 85052D Modify SOLT Calibration Class Assignments Calibration Kit Class G S114 S224 FWDTRANS C REV TRANS C S11B C S22B C FwDMATCH C REV MATCH Cancel C 11C C S22C C ISOLATION V Link FWD TRANS FWD MATCH REV TRANS and REV MATCH Help Expanded Calibration applies to reflection classes m Calibration Class Label Measure all mateable standards in class STIA OPEN Use expanded math when possible
31. ery small and are usually used way above cut off the offset loss term is assumed to be 0 The waveguide loss model is not supported by all VNAs until recently Agilent s PNA series of network analyzers now include a waveguide loss model See Appendix C on page 35 E In S iH 3 offset lec fa f LIUM 1 8 0 1 2h f offset delay wf Offset Zo Offset Zg is the lossless characteristic impedance of the transmission line For coaxial trans mission lines the lossless characteristic impedance is zo ela 62 2 u relative permeability constant of the transmission medium 1 9 D outer conducter inner diameter d center conductor outer diameter Zc the transmission line characteristic impedance that includes skin loss effects can be derived from the offset Z and offset loss terms Waveguide offset Z and characteristic impedance is normalized to 1 Offset terms and transmission line parameters For coaxial transmission lines the following expressions relate the offset terms to the transmission line s electrical parameters See Appendix B on page 32 for their derivation offset Ios oH sedo f 1 10 al f frequency in Hz 2 offset Zo 10 B1 2nf offsetdday ol Ze offset Zo 1 Mu m TU For rectangular waveguide transmission lines 11 the following expressions relate the offset terms to the transmission line s electrical parameters See Appendix C on pag
32. f Frequency ja MHz Height width Ratio 0 5 Cancel Apply Help If the connectors Add or Edit feature is selected the Add or Edit connector screen appears The media section defines the transmission line type COAX WAVEGUIDE or others when available If WAVEGUIDE is selected the Cutoff Frequency and Height Width Ratio entries are required Male and female connectors must be specified separately More than one connector family can be defined for a kit AS VE G O E E Figure 15 Define a new connector family 24 Change Connector Family APE 7 APC A Cancel Help The cal kit s connector family can be renamed The APC 7 connector family is being changed to 7mm Change Connector Family ES m Specify Mew Connector Family 7mm Freviaus Connector Family Specify New Connector Family Previous Connector Family Cancel Help With the family name changes all the kit s cal standard connec tor designations in the description field and the kit description field are updated as shown below Identification Kit Number 17 Kit Name 850500 Kit Description Fmm TAL Calibration Ft Connectors Description Fim Add or Edit Class Assignments sor m edit Family mm 00 Change Family LID Standard 3 OPEN mm open 4 SHORT fmm short Fi OFFSET LOAD from offset load 2 LU BAND LOAD from lowband load 1 BROADBAND mm broadband load 5
33. finitions calibration kit content and its structure requirements for Agilent s vector network analyzers It also provides some examples of how to set up a new calibration kit and how to modify an existing calibra tion kit definition file Calibration Kits A mechanical calibration kit consists of a set of physical devices called standards as shown in Figure 1 Each standard has a precisely known magnitude and phase response as a function of frequency In order for the VNA to use the standards of a calibration kit each standard must be assigned or organized into standard classes which correspond to the calibration method used by the VNA Agilent currently supplies mechanical calibration kits with 1 0 mm 1 85 mm 2 4 mm 3 5 mm 7 mm and Type N 50 ohm Type N 75 ohm Type FD 75 ohm and 7 16 coaxial connectors Rectangular waveguide calibration kits include X P K R Q U V and W bands Calibration for microstrip and other non coaxial media is described in Product Note 8510 8A Agilent Network Analysis Applying the 8510 TRL Calibration for Non Coaxial Measurements literature number 5091 3645E A calibration kit may support many calibration methods Figure 1 Mechanical cal standards and cal kit Connector definitions In addition to calibration standard definitions and standard class assignments calibra tion kits also provide definitions of connectors Agilent s PNA network analyzer family uses the connector definition to define conne
34. g 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 2 4 mm 1 85 mm 1 0 mm coaxial connector interface The location of the calibration plane in these connector standards both sexes is at the outer conductor mating surface as shown in Figure 18 Note During measurement calibration using the 8510 and its derivatives standard labels for the calibration standard indicate both the standard type and the sex of the calibration test port M or F The sex M or F indicates the sex of the test port NOT the sex of the standard This port sex labeling convention must be observed and followed so that the correct calibration standard is connected to the calibration port This is especially important for calibration kits that have different calibration coefficients for the male and female standards such as the Type N 1 85 mm and 1 0 mm calibration kits Type N coaxial connector interface The location of the calibration plane in Type N standards is the outer conductor mat ing surfaces as shown in Figure 19 For the PNA family the device label uses M or F to indicate the sex of the calibration standard instead of the test port M or F sex of the test port M or F gt sex of the calibration standard Calibration Calibration plane Female 3 5mm Figure 18 Location of coaxial connector
35. ignments will determine a set of three standards for each frequency resulting in a series of frequency ranges where only three standards would be required If the VNA spans more that one of these frequency ranges there will be more than three reflection standards connected In the case of the 85058B in addi tion to blending the transitions between the frequency ranges the overall accuracy of the calibration improves when using expanded math There is an option to measure all mateable standards in class measuring all of the standards results in the best accuracy for kits like the 85058B and the 85059B It is advantageous to measure all of the stan dards for some calibration kits but not for others For example in the case of the sliding load kit discussed earlier selecting measure all standards in class would result in mea suring the low band load the sliding load and the broadband load There is no advantage to measuring two fixed loads when doing a sliding load calibration TRL class assignment The TRL TRM family of calibration is defined by the TRL thru reflect and line classes plus TRL options Table 3 shows the TRL portion of a typical VNA class assignment table Table 3 TRL class assignment table Class A B C D E F G Class label TRL thru 11 12 thru TRL reflect 2 4 short TRL line match 14 15 9 10 line load TRL options Calibration reference impedance System Zg Line Zo Test port reference plane Thru Reflect PNA only LRL
36. ine equations 2B 2 R J offset Joss hs 20L 20 Offset Z V 10 2B 5 Offset loss Offset f i 2 Offset Z 10 p1 w Offset delay al Note B v a Offset loss f Z Offset Z 1 7 oreet toss e OSEA E 10 The short s inductance may be determined from physical properties of the shorting plane as presented in reference 10 The computed results are then curve fitted to a third order polynomial function Z JjOL L L Lf LSJ LS 2B 6 2 jarc iil mA 33 34 At low frequencies where the inductance is reasonably linear it may be modeled as an extra delay term 2nfL Ab 2aretan anf A delay 28 7 r The open s fringing capacitance may be determined using three dimension microwave structure simulators However the mechanical structure of the open assembly can be quite complex and can cause simulation problems It may be more realistic to measure the open s response using TRL or offset short calibration techniques where opens are not employed as calibration standards The measured results are then curve fitted to a third order polynomial capacitance model 1 E 2 3 Zr joC C C Cif CLS Of 2B 8 2 jarctan oC TA R I 1 e At low frequencies where the capacitance is reasonably linear it may be modeled as an extra delay term AQ 2arctan 2nf C2 2nf delay 2B 9 Appendix C1 Derivation of Waveguide Calibration Coefficient Model
37. ing TRL standards to TRL class Thru class Reflect class Line class TRL Zero length thru with Unknown equal reflect Line with S41 S22 0 thru reflect 9417 S 0 S24 4971 on port i and port j phase approximately known line Phase approximately Bandwidth limited to avoid known phase of 20 LRL Line with S41 55 0 Unknown equal reflect Line2 with S41 555 0 line reflect line 1 921 and 4 both known with same propagation characteristics as Line2 on port i and port j Phase approximately known phase approximately known Bandwidth limited so phase is at least 20 different from phase of Line TRM Zero length thru with Unknown equal reflect Can be defined as fixed thru reflect 9417 S99 0 21 2 1 on port i and port j loads on ports i and J match Phase approximately 1 7S2 0 Can also be known defined as very long lossy line LRM Line with 44 S22 0 Unknown equal reflect Can be defined as fixed line reflect S91 and 45 both known on port i and port j loads on ports i and match Phase approximately S44 S55 0 Can also be known defined as very long lossy line TRA Zero length thru with Unknown equal reflect Attenuator between ports line reflect 941792570 8442845771 on port i and port j and j S14 S29 0 Defined attenuator Phase approximately as lossy line known LRA Line with 41 555 0 S24 Unknown equal reflect Attenuator between ports line reflect and
38. its such as the Agilent 85059A 1 0 mm preci sion calibration kit use a combination of open short load and offset short standards to calibrate over a very wide frequency range Both shorts and opens are assigned to the 911A class as illustrated by Figure 11 Label is just a name assigned to that class This label is used for on screen prompts or softkey labels during the calibration measurement process 850594 Modify SOLT Calibration Class Assignments Calibration Kit Class 511A C 5204 P DTRANS 46 REY TRANS OK 118 5B C PAD MATCH BEY MATCH Cancel C STE C S522C C ISOLATION Help Iv Link PD TRANS PwD MATCH REY TRANS and REV MATCH Expanded Calibration applies to reflection classes Measure all mateable standards in class Use expanded math when possible Selected Standards ID Label Description 4 OPEN LB F 1 00 mm female OP 18 SHORT 3 F 1 00 mm female 5H OPEN LB M 1 00 mm male DREI SHORT 3 M 1 00 mm male SHO Unselected Standards ID Label Description 4 LL E SO GHz LOAD 1 00 mm female gt 3 SHORT 3LB 1 00 mm female 16 SHORT THE 1 00 mm female 17 SHORT 2 F 1 00 mm female 193 SHORT 4 F 1 00 mm female f SHORT 3BB 1 00 mm prd k The order of the selected standards iz used to determine which standard is selected when multiple standards are valid at given frequency Standards listed first have priority i Move Up Move Down
39. lent Technologies products applications or services please contact your local Agilent office The complete list is available at www agilent com find contactus Americas Canada 877 894 4414 Brazil 11 4197 3500 Mexico 01800 5064 800 United States 800 829 4444 Asia Pacific Australia 1 800 629 485 China 800 810 0189 Hong Kong 800 938 693 India 1 800 112 929 Japan 0120 421 345 Korea 080 769 0800 Malaysia 1 800 888 848 Singapore 1 800 375 8100 Taiwan 0800 047 866 Other AP Countries 65 375 8100 Europe amp Middle East Belgium 32 0 2 404 93 40 Denmark 45 70 13 15 15 Finland 358 0 10 855 2100 France 0825 010 700 0 125 minute Germany 49 0 7031 464 6333 Ireland 1890 924 204 Israel 972 3 9288 504 544 Italy 39 02 92 60 8484 Netherlands 31 0 20 547 2111 Spain 34 91 631 3300 Sweden 0200 88 22 55 United Kingdom 44 0 118 9276201 For other unlisted Countries www agilent com find contactus Revised October 14 2010 Product specifications and descriptions in this document subject to change without notice Agilent Technologies Inc 2001 2007 2009 2011 Printed in USA March 28 2011 5989 4840EN ok Agilent Technologies
40. listed in a class their frequency ranges have a finite overlap For the 8510 and unguided calibration on the PNA the last standard measured is used in the overlap region Usually the load classes for a sliding load kit are defined with three load standards a low band load a sliding load and a broadband load Often the low band load and the broadband load are the same physical device The low band load has a reduced frequency range and is intended to be paired with the sliding load to cover the full frequency range of the kit For users who desire a quicker less accurate calibration the broadband load is defined to cover the full frequency range In the 8510 and PNA unguided calibration if a user measured a sliding load then measured a broadband load the calibration would be computed using only the broadband load ignoring the sliding load altogether SmartCal guided cal in the PNA avoids this problem altogether by selecting the standards based on the order they are listed in the class thus a sliding load will always have priority over a broadband load when it is listed before the broadband load Expanded calibration is a weighted least squares solution that uses the measurement of three or more standards The least squares solution works well when all observations are trusted to the same degree That is to say the actual response of each standard is known with the same accuracy This is a reasonable assumption for ECal but may not be valid when
41. ly works for a zero length thru In the case when the thru standard is a line with non zero length the model of the thru standard is used to compute the testport reference plane In the case of coax or wave guide using the model of the thru standard alone will provide excellent results In the case of other dispersive media such as microstrip the thru standard alone may give less than optimal results One option would be to design the test fixture and calibration stan dards so that the testport would be located in the middle of the thru Another alternative would be to select LRL line auto characterization One of the by products of the TRL algorithm is a computed value for the line standard propagation constant This would include any dispersive effects of the transmission medium When LRL line auto charac terization is set the propagation characteristics of the thru standard are computed from the computed propagation characteristics of the line standard and the defined delays for both the thru and line standards Note LRL line auto characterization will only be used at frequencies where both the THRU and LINE standards are delay lines and where the offset impedance of the THRU and LINE standards are equal Table 5 TRL options and meaning Calibration reference plane set Testport Reference Plane fa THRU STANDARD C REFLECT STANDARD Testport Reference Plane C THRUSTANDARD REFLECT STANDARD LRL line auto characterization
42. n A measurement calibration is a process which mathematically derives the systematic error model for the VNA This error model is an array of vector error coefficients used to establish a fixed reference plane of zero phase shift zero reflection magnitude lossless transmission magnitude and known impedance The array of coefficients is computed by measuring a set of known devices or calibration standards connected at a fixed measurement plane Different calibration techniques are used to solve different error models The definition of calibration standards and types are set up differently for the applicable calibration techniques Solving the full 2 port twelve term error model using the short open load thru SOLT calibration method is an example of only one of the many measurement calibrations available The type of measurement calibration selected by the user depends on the device to be measured i e 1 port or 2 port device the calibration standards available and the extent of accuracy enhancement desired A combination of calibrations can be used in the measurement of a particular device such as adapter removal calibration for non insertable devices The accuracy of subsequent device measurements depends on the accuracy and stability of the test equipment the accuracy of the calibration standard model and the calibration method used in conjunction with the error correction model This application note covers calibration standard de
43. offset loss must be in G ohm s The equation may be reformulated as follows to be consistent with coaxial and rectangular waveguide structures 1 VEN Kla nf Upp If ees Estes EN sa pg SNE C2 4 r fo JUV Ho f Y 1 1 amp Jg 1 h Note that the xc term is equivalent to 2 height width ratio of rectangular waveguides Use this as the height width ration value in calibration coefficients 37 38 let offset loss Seeker offset delay _f ve r v 2 C2 5 feo f GJE then al offset loss offset delay 20 E LEA Mo f f fa The combine propagation constant is 2 TRY PONG QA ny y 2 o jp x offset loss i MEN SE eas ei IN j 2nf amp offset delay Ho f f 2 f 5 C2 6 Appendix D Data based Calibration Standard Definition File Format beta release of the calibration kit editor is available at http na tm agilent com pna dbcal html This editor will allow the creation of kits that include data based stan dards Data based standards are described by a data list A data based standard should include a list of frequencies the actual response for each s parameter at each frequency and an estimate of the accuracy of the actual response to be used in determining the weighting factor Currently only one port devices are supported Support for two port devices will be added later Example file CITIFILE A 01 01 HPNA Rev A 01 00 HPNA STDTYPE DATABASED COMMENT MODEL 85058
44. or Co also known as fringing capacitance At low frequencies a fixed capacitance value may be suffi cient Most network analyzers use a third order polynomial capacitance model Radiation loss is assumed to be insignificant B 2 3 1 1 13 Co C Cf Cf C Zo y 1 13 Zo 4 Io Zo Z 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 Fixed load The fixed load is assumed to be a perfect termination I 0 However if an offset transmission line with a finite delay and loss is specified and an offset Z is not equal to the reference impedance the total reflection is NOT zero This is as defined in equa tion 1 4 Arbitrary impedance An arbitrary impedance device is similar to a fixed load except that the load imped ance is NOT perfect The previous generations of VNA such as the Agilent 8510 87xy series and the early firmware releases of the PNA series use a fixed resistance value A complex terminating impedance has been added to the PNA series to allow for more accurate modeling of circuit board and on wafer devices Z Z 1 14 Lat Z Note The 8510 assumes that the first offset has zero delay and the second offset has the required delay Therefore the offset delay value of the offset load must be the difference in delay between the two offsets Offset loads Loads x Identification
45. or modification All current Agilent mechanical calibration kits are preinstalled in the factory cal kit file directory If the kit of interest is not on the list import the kit instructions follow Once on the list select the kit then click on Edit Kit re Untitled PN File l view Help D Delete Kit List oO x at A1 mtor ID Kit Name 1 OML WR 05 Description OMS WR 05 Cal Kit Edit Modify the active kit With the PC version select a kit and then select Edit gt Modify Figure 14 Select and modify cal kit II Untitled PNA Cal Kit Editor M Edit View Help New Kit Ctrl N Import Kit Ctrl I Save Kit Ctrl 5 Kit List Open Workspace Description Save Workspace 1 85 mm Offset Short kit Restore Default Kits Print To File Exit Or download a PC executable PNA Cal Kit Editor program The PC version may not be as updated as the PNA s built in version Newer versions can process kit data created by an older version The reverse may not be true Import Kit Look in user e et fr CK 7MMA1 CK 7MMB2 CK 7MMC2 l ck 7MMD2 CK SC ej ck TNC CK WR10A 3 Ej CK WR15A 3 My Recent Documents Y Desktop CK 24MMA 4 CK 24MMD 3 Ck 35MMA 1 j Ck 35MMB 3 Ck 35MMC 4 Ej Ck 35MMD 3 CK WR19A 3 Ej CK WR224 3 CK WR28A 3 Ej CK WR42A 1 CK WR62A 1 Ej Ck WR90A 1 My D t y Documents Maury 87705 ckt E OML WR 03
46. ossible combinations of offsets to find the pair with the widest expected separation to use in determining the actual response of the load element When specifying more than two offsets the user should define multiple offset load standards When assigning multiple offset load standards to SOLT classes for the PNA it is usually beneficial to specify use expanded math when possible See the section on SOLT class assignment on page 16 Sliding load A sliding load is defined by making multiple measurements of the device with the slid ing load element positioned at various marked positions of a long transmission line The transmission line is assumed to have zero reflections and the load element has a finite reflection that can be mathematically removed using a least squares circle fitting meth od For best results try to move the load element in the same direction do not move it back and forth Also try to slide in non uniform not equally spaced increments 11 12 Data based standard model The data based standard model is a new feature in Agilent s network analyzers It allows a calibration standard to be defined by a data file that contains frequency data S parameter data and uncertainty data The data file may be created using actual measured data from a reference metrology laboratory model data from device modeling software or combina tions of both See Appendix D on page 37 for details on data file formats Figu
47. owave Measurement Symposium and Exhibition D Rytting Mar 1987 Appendix to an Analysis of Vector Measurement Accuracy Enhancement Techniques Hewlett Packard RF amp Microwave Measurement Symposium and Exhibition D Rytting 1996 Network Analyzer Error Models and Calibration Methods RF amp Microwave Measurements for Wireless Applications ARFTG NIST Short Course Notes G F Engen C A Hoer Dec 1979 Thru Reflect Line An Improved Technique for Calibrating the Dual 6 Port Automatic Network Analyzer IEEE Trans Microwave Theory Tech vol MTT 27 pp 983 987 R A Speciale Dec 1977 A Generalization of the TSD Network Analyzer Calibration Procedure Covering N port Scattering Parameter Measurements Affected by Leakage Errors IEEE Trans Microwave Theory Tech vol MTT 24 pp 1100 1115 E J Eul B Schiek Apr 1991 A Generalized Theory and New Calibration Procedure for Network Analyzer Self Calibration leEE Trans Microwave Theory Tech vol 39 pp 724 731 R B Marks Fall 1997 Formulations of the Basic Vector Network Analyzer Error Model Including Switch Terms 50th ARFTG Conference Digest pp 115 126 D Blackham K Wong July 2005 Latest Advances in VNA Accuracy Enhancements Microwave Journal pp 78 94 K H Wong Dec 1988 Using Precision Coaxial Air Dielectric Transmission Line as Calibration and Verification Standards Microwave Journal pp 88 92 KH Wong June 1992 Characterization
48. ption Upload Data From File Browse Frequency Range Min o MHz Max 393000 MHz Connectors One Port Standard File Information Clear o Cancel Apply Help Figure 9 Data based standard setup screen Maximum minimum frequency The maximum and minimum frequency entries define the applicable frequency range of the calibration standard The applicable range may be limited by the model data accu racy of the model or the physical dimensions of the calibration standard A fixed load for example may be used at low frequencies while a sliding load may be used at high frequencies For waveguide the minimum frequency is the waveguide cut off frequency Although the PNA s SmartCal guided cal no longer uses the minimum frequency of a calibration standard as the cut off frequency for dispersion correction it is still recommended that the minimum frequency equals the cut off frequency for backward compatibility 13 14 Class assignment Calibration kit class assignment organizes calibration standards into a format which is compatible with the error models used in measurement calibration Each calibration standard is assigned with a standard number That number is then assigned to a class or calibration measurement that is required for the calibration method selected Some standards may have multiple standard numbers assigned for different calibration methods or different standard definitions This may
49. re 7 shows how the data based standard bypasses the fitting process and eliminates any errors that may have been associated with the fitting Fitting errors are usually neg ligible for frequencies below 30 GHz However at higher frequencies multiple frequency banded models for the same standard have been used to avoid errors due to fitting The data based standard avoids this problem altogether by interpolating on the data directly The data based calibration standard also eliminates shortcomings of fitting non coaxial or waveguide standards to the models based on a coaxial or waveguide structure This increased flexibility also enables the user to more easily define custom calibration standards that do not accurately fit existing calibration coefficient models This can be especially useful for dispersive transmission line structures The data may be obtained by device modeling based on physical dimensions or from accurate measurements Fit nominal response to polynomial model Nominal polynomial model Compute nominal includes response from nominal fitting errors dimensions Nominal data based model eliminates fitting errors Figure 7 Data based vs polynomial model The factory data based models are similar to polynomial models in that they are a generic nominal model for a particular part number Thus a replacement calibration standard can be ordered for a calibration kit and used without having to modify the data based model
50. store a Calibration kit onto a disk 21 28 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 standards and appropriate labels Front panel procedure P band waveguide example Prior to modifying or generating a cal kit store one or both of the cal kits in the s non volatile memory to a disk Select CAL menu gt MORE Prepare to modify cal kit 2 press MODIFY 2 To define a standard press DEFINE STANDARD Enable standard no 1 to be modified press 1 X1 Select standard type SHORT Specify an offset SPECIFY OFFSETS Enter the delay from Table 1 OFFSET DELAY 0 0108309 ns 9 Enter the loss from Table 1 OFFSET LOSS 0 X1 10 Enter the Z0 from Table 1 OFFSET Z0 50 X1 11 Enter the lower cutoff frequency MINIMUM FREQUENCY 9 487 GHz 12 Enter the upper frequency MAXIMUM FREQUENCY 18 97 GHz 13 Select WAVEGUIDE 14 Prepare to label the new standard press PRIOR MENU gt LABEL STANDARD gt ERASE TITLE 15 Enter PSHORT 1 by using the knob SELECT gt LETTER softkey and SPACE softkey 16 Complete the title entry by pressing TITLE DONE 17 Complete the standard modification by pressing STANDARD DONE DEFINED oO N oc C A W N Standard 1 has now been defined
51. t Offset delay Offset delay is the dispersion free TEM mode electrical delay in seconds l 1 5 Offset delay Ve 1 5 c l physical offset length from reference plane relative permittivity dielectric constant of transmission medium 1 000649 in air 9 sea level and 50 6 humididty c speed of light in vacuum 2 99792458 x 10 m s Note that the reference plane of coaxial connectors is defined as the mating plane of the outer conductors Appendix A on page 30 illustrates the physical offset length definition of certain coaxial connector types Offset loss Offset loss is in G7 sec It is the propagation loss per unit length of the transmission line at a normalization frequency such as 1 GHz multiplied by the speed of light in the transmission medium For coaxial devices it can be calculated from the loss magnitude data at 1 GHz 951 data OffsetZ 1 6 Linear mag Offset loss xd In IS cs loe delay Log mag dB Offset loss m0 Bien oe y 10 Offset dela 911 data Offset Z Linear mag Offset loss In S i EH oer 1 7 1 Offset Z Log mag dB Offset loss Po esas For best results curve fit the measured data to the V f function See Appendix B on page 32 for details 109 For rectangular waveguide transmission lines loss is not a simple function of frequency In most cases the 1 GHz data point is not available Since the loss of most waveguide standards are v
52. tored on a single disk Below is the generic procedure to load or store calibration kits from and to the disk drive or disk interface To load calibration kits from disk into the Agilent h Insert the calibration data disk into the network analyzer or connect compatible disk drive to the system bus 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 non volatile registers that the calibration kit will be loaded into FILE _ or FILE NAME Select the calibration kit data to load LOAD FILE N oO 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 CAL 1 or CAL 2 on the CRT display To store calibration kits from the Agilent onto a disk 1 Insert an initialized calibration data disk into the 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 non volatile calibration kit registers 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
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