1. 4 August 2008 1 An Interlaboratory Comparison of 3.5 mm Coaxial 2-Port Vector Network Analyzer Measurements 4 August 2008 Li Pi Su, Dexter Shelton, George Walden, and Garrett Barksdale Electromagnetic Standards Laboratory US Army Primary Standards Laboratory

2. 4 August 2008 2 Outline ILC Participants ILC Measurement Parameters and Artifacts Artifact Specifications and Measurement Assurance The ILC Objectives ILC Procedures Analysis & Results Conclusion and Recommendation

3. 4 August 2008 3 ILC Participants Electronics and Electrical Engineering Laboratory, National Institute of Standards and Technology (NIST) Air Force Primary Standards Laboratory (AFPSL) Navy Primary Standards Laboratory (NPSL) Army Primary Standards Laboratory (APSL) Agilent Technologies Santa Rosa Metrology Services Anritsu Company Standards Laboratory

4. 4 August 2008 4 ILC Measurement Parameters and Artifacts Artifacts: Four Agilent model 8493C 3.5 mm coaxial attenuators with attenuations of 6, 10, 20 and 40 dB. Frequencies: 1.0 to 26 GHz in 1 GHz increments, and 26.5 GHz, totally 27 frequencies.

5. 4 August 2008 5 Manufacturer’s Specifications Agilent 3.5 mm 8493C Attenuators Specifications Frequency (GHz) Max SWR Max Reflection Coefficient Attenuation Specification 6 dB10 dB20 dB40 dB 1 to 81.10.047620.6 dB0.3 dB0.5 dB1.0 dB 9 to 12.41.150.069770.6 dB0.3 dB0.5 dB1.0 dB 12.5 to 181.250.111110.6 dB0.3 dB0.5 dB1.0 dB 18 to 26.51.250.111110.6 dB0.5 dB0.6 dB1.3 dB

6. 4 August 2008 6 The ILC Objectives Primary Objective: coaxial An appraisal of the capabilities and degree of equivalence of the participant laboratories in performing 3.5 mm coaxial 2-port VNA measurements accurately and consistently. Secondary Objective: To demonstrate proficiency of VNA operators in the context that the participants can produce measurement results consistent with other comparable laboratories.

7. 4 August 2008 7 ILC Procedures I The pivot laboratory performed the initial measurements of the artifacts. The devices then were sent to the remaining laboratories in a circular (serial) fashion. Measurement details: Measure both magnitude and phase of devices on 3 separate occasions. Each occasion consisted of 3 measurements of each device with the devices disconnected and reconnected at approximate 120 o axial rotations.

8. 4 August 2008 8 ILC Procedures II Data Submission: Measurement data were submitted in polar form: magnitudes expressed to at least 4 decimal places and phases in degrees to at least 3 decimal places. Measurement data were submitted in either Microsoft Excel spreadsheet or text file format (comma- or tab-delimited).

9. 4 August 2008 9 Stability and Drift Data: To determine stability and drift of the artifacts, the closing measurement of the artifacts were collected. Final measurements of the artifacts: Measurements were taken before and after the devices were cleaned. The measurements were compared with the initial dataset to check for stability and drift. Data was analyzed. Concurrence was obtained from the participants for releasing the results. ILC Procedures III

10. 4 August 2008 10 Analysis I Measurement Systems and Methods HP 8510 VNA systems consisting of an HP 85101C VNA, an 85102B IF receiver, 8517A modified 50 GHz test set, an 83651B 50 GHz synthesized sweeper, an 85133E 2.4 mm cable, an 85052C modified (with added beadless 7.5 cm line and optimized shorts) TRL calibration kit using the MultiCal TRL calibration technique. An Agilent E8364B PNA (10 MHz to 50 GHz) VNA with an 85052C calibration kit. An Agilent 85052C and 85050C TRL calibration kits using the TRL option. A model 37369C VNA with a 3650-1 sliding load calibration kit. An HP 8510C VNA using sliding load calibration with the 85052B calibration kit and an 85053A verification kit.

11. 4 August 2008 11 Analysis II Data Adjustment Where the data scatter crossed the ± 180° boundary, the following algorithm was applied to the measurements from all participants. Here, N is the phase measured by NIST, and M is the phase measured by the non-NIST participant. N + IF(ABS(M – N)>180, IF((M – N)>0, 360 – (M – N), ABS(M – N) – 360)), (M – N)) For example, the (mag,178°) and (mag,-182°) points are the same point.

12. 4 August 2008 12 Analysis III The mean and standard deviation of all measurements, the respective group means and standard deviations, and the (measurement – NIST) values were computed and presented in graphs. Artifacts’ Baselines: The manufacturer’s specifications for the magnitude of these four artifacts were used as the respective artifacts’ baselines. The NIST-measured data were used as another baseline.

13. 4 August 2008 13 Results I-1 All the magnitude measurements are within the manufacturer’s specifications. Most of the (Magnitude measurement – NIST magnitude) values are within the NIST uncertainty.

14. 4 August 2008 14 Results I-2 Results I-2 Table 1A. 6 dB Attenuation Magnitude S Parameter Is Magnitude within manufacturer’s specifications? Is Participant's (Meas  NIST) within ± NIST Uncertainty? Is Participant's (Mean  NIST) within ± NIST Uncertainty? Participant's Own StDev < NIST Uncertainty? S 11 Yes allNot E Yes all S 22 Yes allNot D Yes all S 21 Yes allNot D, E Not E S 12 Yes allNot ENot D, ENot E

15. 4 August 2008 15 Results I-3 Table 2A. 10 dB Attenuation Magnitude S Parameter Is Magnitude within manufacturer’s specifications? Is Participant's (Meas  NIST) within ± NIST Uncertainty? Is Participant's (Mean  NIST) within ± NIST Uncertainty? Participant's Own StDev < NIST Uncertainty? S 11 Yes all S 22 Yes all S 21 Yes allNot DNot D, EYes all S 12 Yes allNot A, D, E Yes all

16. 4 August 2008 16 Results I-4 Results I-4 Table 3A. 20 dB Attenuation Magnitude S Parameter Is Magnitude within manufacturer’s specifications? Is Participant's (Meas  NIST) within ± NIST Uncertainty? Is Participant's (Mean  NIST) within ± NIST Uncertainty? Participant's Own StDev < NIST Uncertainty? S 11 Yes all S 22 Yes all S 21 Yes allNot D, E Yes all S 12 Yes allNot D, E Yes all

17. 4 August 2008 17 Results I-5 Table 4A. 40 dB Attenuation Magnitude S Parameter Is Magnitude within manufacturer’s specifications? Is Participant's (Meas  NIST) within ± NIST Uncertainty? Is Participant's (Mean  NIST) within ± NIST Uncertainty? Participant's Own StDev < NIST Uncertainty? S 11 Yes all S 22 Yes all S 21 Yes allNot E Not E, StdDev of all S 12 Yes allNot A, C, ENot E Not StdDev of all

18. 4 August 2008 18 Results II-1 Most of the (Phase measurement – NIST phase) values are within the NIST uncertainty. Table 1B. 6 dB Attenuation_ Phase S Parameter Is Participant's (Meas  NIST) within ± NIST Uncertainty? Is Participant's (Mean  NIST) within ± NIST Uncertainty? Participant's Own StDev < NIST Uncertainty? S 11 Not EYes all S 22 Not D Yes all S 21 Yes all S 12 Yes all

19. 4 August 2008 19 Results II-2 Table 2B. 10 dB Attenuation Phase S Parameter Is Participant's (Meas  NIST) within ± NIST Uncertainty? Is Participant's (Mean  NIST) within ± NIST Uncertainty? Participant's Own StDev < NIST Uncertainty? S 11 Not D Yes all S 22 Not B, C, ENot BYes all S 21 Yes all S 12 Yes all

20. 4 August 2008 20 Results II-3 Table 3B. 20 dB Attenuation Phase S Parameter Is Participant's (Meas  NIST) within ± NIST Uncertainty? Is Participant's (Mean  NIST) within ± NIST Uncertainty? Participant's Own StDev < NIST Uncertainty? S 11 Yes all S 22 Not DNot D, EYes all S 21 Yes allNot EYes all S 12 Yes all

21. 4 August 2008 21 Results II-4 Table 4B. 40 dB Attenuation Phase S Parameter Is Participant's (Meas  NIST) within ± NIST Uncertainty? Is Participant's (Mean  NIST) within ± NIST Uncertainty? Participant's Own StDev < NIST Uncertainty? S 11 Yes all S 22 Yes all S 21 Yes allNot EYes all S 12 Yes allNot EYes all

22. 4 August 2008 22 Results III Most of the participants’ own standard deviations are within the NIST uncertainty. Closing Analysis: Most of the differences between the pivot laboratory’s initial and closing measurements are well within the NIST uncertainty. Some of the differences are very insignificant. The S 21 and S 12 magnitudes, and the S 12 phases’ drifts for all four of the attenuators are negative. (This is probably due to a drift in the offset error corrections used in the system calibrations. Because the drift was well within the systematic uncertainty, the bias was uncorrected.) (See charts 12 to 16.)

23. 4 August 2008 23 Results IV—Chart 1

24. 4 August 2008 24 Results IV—Chart 2 Results IV—Chart 2

25. 4 August 2008 25 Results IV—Chart 3 Results IV—Chart 3

26. 4 August 2008 26 Results IV—Chart 4 Results IV—Chart 4

27. 4 August 2008 27 Results IV—Chart 5 Results IV—Chart 5

28. 4 August 2008 28 Results IV—Chart 6 Results IV—Chart 6

29. 4 August 2008 29 Results IV—Chart 7 Results IV—Chart 7

30. 4 August 2008 30 Results IV—Chart 8

31. 4 August 2008 31 Results IV—Chart 9

32. 4 August 2008 32 Results IV—Chart 10

33. 4 August 2008 33 Results IV—Chart 11

34. 4 August 2008 34 Results IV—Chart 12

35. 4 August 2008 35 Results IV—Chart 13

36. 4 August 2008 36 Results IV—Chart 14

37. 4 August 2008 37 Results IV—Chart 15

38. 4 August 2008 38 Results IV—Chart 16

39. 4 August 2008 39 Conclusions and Recommendation Conclusions and Recommendation In general, both magnitude and phase measurements among all participants were consistent and the magnitudes were well within the manufacturer’s specifications. We also noted that the deltas between the pivot lab's initial and ending measurements were negligible. The evidence shows that the four artifacts were very well maintained and that very good laboratory practice was followed by all participants. The evidence also shows that the artifacts held up well with the rigors of transportation to and from the participating laboratories. Additional analysis and study would be needed to determine the reasons and significance of the drifts described in the Results III.

40. 4 August 2008 40 QUESTIONS??