Agilent Technologies 8510 manual

Agilent Specifying Calibration Standards for the Agilent 8510 Network Analyzer 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 tes[...]

2 3 3 3 4 5 5 7 7 8 9 9 9 11 12 12 12 14 14 15 16 16 17 17 17 18 18 18 18 19 19 19 19 19 20 20 20 21 21 22 22 22 23 23 26 29 Introduction Measurement errors Measurement calibration Calibration kit Standard definition Class assignment Modification procedure Select standards Define standards Standard number Standard type Open circuit capacitance: C 0[...]

3 Introduction This product note co vers measurement calibration requirements for the Agilent 8510B/C network analyzer . All of t he capabilities described in this note also apply to the A gilent 8510A with t he follo wing ex ceptions: response & isolation calibra- tion; short circuit induct ance; class assignments for f or ward/rev erse isolat[...]

4 The array coeff icients are computed by measuring a set of “kno wn” devices connected at a f ixed point and solving as the vector difference betw een t he modeled and measured response. The full 2-port er ror model sho wn in F igure 1 is an example of onl y one of t he measurement calibra- tions available with the 8510. The measurement calibr[...]

5 Standard definition Standard def inition 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 fr om t he physical dimen- sions and material of each calibration st andards or from its actual measure[...]

6 T able 1. Standard definitions table T able 2. Standard class assignments[...]

7 Modification procedure Calibration kit modification provides the capability to adapt to measurement calibrations in ot her con- nector types or to generat e more precise error models from existing kits. Pr ovided the appropri- ate st andards are a vailable, cal kit modif ication can be used to est ablish a reference plane in the same transmission[...]

8 Define standards A glossar y of standard definition paramet ers used with t he Agilent 8510 is included in t his section. Each parameter is described and appropriate con- versions are listed f or implementation wit h the 8510. T o illustrat e, a calibration kit f or WR -62 rec- tangular waveguide (operating frequency range 12.4 to 18 GHz) will be[...]

9 Each standard is described using the St andard Definition Table in accordance with t he 1- or 2- port model. The St andard Definition t able for a wav eguide calibration kit is shown in Table 1. Each standard type (shor t, open, load, thr u, and arbi- trar y impedance) ma y be def ined by the parame- ters as specif ied belo w . • Standard numbe[...]

10 It is not possible to remov e fringing capacit ance, but the result ant phase shift can be modeled as a function of frequency using C 0 through C 3 (C 0 +C l x f + C 2 x f 2 + C 3 x f 3 ,with units of F(Hz), C 0 (fF), C 1 (10 -27 F/Hz), C 2 (10 -36 F/Hz 2 ) and C 3 (10 -45 F/Hz 3 ), which are the coef ficients for a cubic polynomial that best f [...]

11 Note In some cases (when the phase response is linear with respect t o frequency) the response of an open can be modeled as an equivalent “incremental” length. This method will serve as a first order appro xima- tion only , but can be useful when dat a or stan- dards f or t he abo ve modeling techniques are not available. F or t he wav eguid[...]

The inductance as a function of frequency can be modeled by specifying the coeff icients of a third- order polynomial (L 0 + L 1 x f + L 2 x f 2 + L 3 x f 3 ), with units of L 0 (nH), L 1 (10 -24 H/Hz), L 2 (10 -33 H/Hz 2 ) and L 3 (10 -42 H/Hz 3 ). F or t he wav eguide example, the induct ance of the offset shor t circuits is negligible. L 0 t hro[...]

13 The convention f or def inition of offset delay in wav eguide requires entr y of t he dela y assuming no dispersion. F or waveguide transmission line, the Agilent 8510 calculat es the ef f ects of dispersion as a function of frequency as follo ws: f co = lo wer cutoff frequency f = measurement frequency Note T o assure accurat e definition of of[...]

14 µ r = relative permeability constant of t he medium (equal to 1.0 in air) ε r = relative permittivity constant of t he medium (equal to 1.000649 in air) D = inside diameter of outer conduct or d = outside diameter of inner conductor The 8510 requires that t he characteristic imped- ance of wav eguide transmission line is assigned to be equal t[...]

15 Therefore, f or the WR -62 wav eguide st andard defi- nition table, of fset loss of zero ohm/sec is entered for all f our standards. Lower/minimum frequency Lo wer frequency defines t he minimum frequency at which the st andard is to be used for the purposes of calibration. Note When defining coaxial of fset st andards, it ma y be necessar y to [...]

16 Upper/maximum frequency This specifies t he maximum frequency at which the st andard is valid. In broadband applications, a set of banded standards may be necessary t o pro- vide constant response. For exam ple, coaxial of fset standards (i.e., 1 / 4 λ offset shor t) are generally spec- ified over bandwidths of an octav e or less. Bandwidth spe[...]

17 Note Mathematical operations on measurements (and display ed dat a) aft er calibration are not corrected for dispersion. Enter W A VEGUIDE int o the st andard definition table for all f our st andards. Standard labels Labels are entered through t he title menu and ma y contain up t o 10 characters. St andard Labels are entered to facilit ate men[...]

18 S 11 A,B,C and S 22 A,B,C S 11 A, B,C and S 22 A,B,C correspond t o the S 11 and S 22 ref lection calibrations for port 1 and por t 2 respectivel y. These t hree classes are used by the Agilent 8510 t o solv e for the systematic er rors; directivity , source match, and ref lection tracking. The three classes used by the 7-mm cal kit are labeled [...]

19 TRL Thru TRL Thru cor responds to t he measurement of the S-parameters of a zero-length or shor t thr u connec- tion between port 1 and por t 2. The Thru, Ref lect and Line classes are used ex clusively f or t he three steps of the TRL 2-PORT calibration. T ypically , a “delay/thru” wit h zero (or the smallest) Offset Delay is specified as t[...]

20 Each adapter is specif ied as a single delay/thr u standard and up to seven standards numbers can be specified int o the adapter class. Standard Class labels Standard Class labels are entered t o facilitat e menu-driven calibration. A label can be an y user- selected ter m which best describes the device or class of devices that the operat or sh[...]

21 Again, cal kit labels should be chosen t o best describe the calibration devices. The “B.1” default suff ix corresponds t o the kit’s mechanical revision (B) and mathematical revision (1). Note T o prevent confusion, if an y st andard definitions in a calibration kit are modified but a new kit label is not entered, the default label will a[...]

22 User modified cal kits and Agilent 8510 specifications As noted previously , the result ant accuracy of t he 8510 when used with any calibration kit is depend- ent on ho w well its standards are defined and is verified through measurement of a device with traceable frequency response. The published Measurement Specifications for the 8510 Netw or[...]

23 Appendix A Calibration kit entry procedure Calibration kit specifications can be ent ered into the A gilent 8510 using the 8510 disk drive, a disk drive connected to the syst em bus, by fr ont panel entr y , or through program control b y an ext ernal controller . Disk procedure This is an import ant f eature since t he 8510 can internally store[...]

24 Front panel procedure: (P -band waveguide example) 1. Prior to modifying or generating a cal kit, store one or both of t he 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. T o def ine a standard: press DEFINE STAND ARD. 5. Enable standard no. 1 to be modif ied:[...]

25 4. Change the class label for S 11 A: LABEL CL ASS, S 11 A, ERASE TITLE. 5. Enter the label of PSHORT 1 by using the knob, the SELECT sof t ke y and t he SP ACE soft k ey. 6. Complete the label entr y procedure: TITLE DONE, L ABEL DONE. F ollow a similar pr ocedure t o enter t he remaining standard classes and labels as shown in the table belo w[...]

26 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 deter mine the OFFSET DEL AY of a[...]

27 Female type-N Male type-N 7 mm Coaxial connector T ype-N coaxial connector interface The location of the “calibration plane” in T ype-N standards is the outer conductor mating surfaces as shown below . Note: 1.0mm, 1.85mm and 2.4mm connectors not shown, but similar to 3.5mm calibration planes.[...]

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29 Appendix C Cal coefficients model Offset devices like offset shorts and of fset opens c an be modeled by the follo wing signal f low graph : Figure 1 Signal flow graph model of offset devices The offset por tion of the open or shor t, is modeled as a perfectly unif or m lossy air dielectric transmis- sion line. The expected coef ficient of ref l[...]

30 Their first order appro ximations, R is small and G=0, are: Equation 3 Since Equation 4 F or coaxial devices[...]

31 then: Equation 5 Equation 6 If the Of fset delay=0, then the coeff icient of ref lection, Γ = Γ L .[...]

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