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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.
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 Sta.
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 8510.
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.
5 Standard definition Standard def inition is the process of mathematical- ly modeling the electrical characteristics (delay , attenuation and impedance) of each calibration standard.
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.
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.
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 .
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.
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.
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.
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 .
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 .
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.
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.
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.
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.
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.
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.
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).
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.
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 .
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.
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.
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.
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.
28.
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.
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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