New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators. Jens Leinhos, Thomas Reichel and Jochen Simon

Transcription

1 New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators Jens Leinhos, Thomas Reichel and Jochen Simon

2 Contents l l l l l l l l l Introduction Measurement Procedures Direct Calibration Method Time Domain Method Load-Pull Method Result of Measurements Conclusion Outlook References New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 2

3 Introduction What is the best method for determining the effective source reflection coefficient of a microwave generator? New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 3

4 Measurement Procedures Scalar Methods With additional generator Calibration with short and open standards Disadvantage: Interference causes errors! Without additional generator Direct signal interferes with signal reflected at short and GUT, direct VSWR measurement Calibration procedure is not necessary! Disadvantage: Ideal hardware required! New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 4

5 Measurement Procedures Vectorial Methods With additional generator VNA OSM calibration Disadvantage: Interference causes errors! Without additional generator Direct calibration method according to Juroshek Time domain method according to Reichel Load-Pull method according to Hecht/ Simon New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 5

6 Direct Calibration Method δb 2 δa 1 Δb 2 G a b 2 The wave emanating from the output is changed by: b 1 Δb Δb 3 1 RF signal pick-off control voltage δb 3 3 b 3 output circuitry (e.g. step attenuator) level detection (well-matched) test port a 2 load matched load mismatched load b 3 kept constant by ALC New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 6

7 Direct Calibration Method Remarks: 1. The leveling loop must be of an integrating type, so that b 2 is really kept constant. 2. The reflection coefficient of the oscillator has no effect at all! G 1 3 x can be written as function of a 2 and b 3 : New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 7

8 Direct Calibration Method This is the equivalent circuit of a one-port VNA with e 11 source match, e 00 directivity and e 10 e 01 reflection tracking! New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 8

9 Direct Calibration Method receiver test port 1 G cal standards receiver reference plane of extended VNA VNA This method has first been published by John R. Juroshek from NIST in 1997 [1]. New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 9

10 Time Domain Based Method Steps of calibration Full Two-Port calibration of the VNA Steps of measurement and evaluation Measurement of all four S-parameters of the mismatched line Match of the power sensor must be determined Measurement of b s 2 with the power sensor Measurement of S 21 2 b 2 with the power sensor Evaluation of the measured data New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 10

11 Time Domain Based Method test port G New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 11

12 Time Domain Based Method frequency domain time domain New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 12

13 Time Domain Based Method practical realisation of Z 0 (50 Ω) T junction decoupling pad New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 13

14 Time Domain Based Method Refinements in the Fourier Transformation Process Application of linear prediction to the samples of r(nδf) delivers accurate results even at the beginning and the end of the frequency range Application of mirroring (low pass transformation) to the r(nδf) series reduces spectral leakage into E(t) and enhances resolution Refinements in the Evaluation Process Separation of into the wanted part and the reflection of the connector convolution product of the connector reflection and the DUT reflection impulse response can be removed Application of gamma correction to the b s 2 measurment improve accuracy New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 14

15 Load-Pull Method Steps of calibration according to Hecht [2] Reflection calibration of VNA at port 1 Absolute power calibration of port 1 Load reflection and power calibration of port 2 Steps of measurement and evaluation according to Simon [3] Measurement of GUT Evaluation of the measured data New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 15

16 Load-Pull Method Calibration: New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 16

17 Load-Pull Method Measurement and evaluation: New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 17

18 Result of Measurements New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 18

19 Result of Measurements New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 19

20 Result of Measurements New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 20

21 Result of Measurements * Direct calibration method is used as reference. New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 21

22 Conclusion Direct Calibration Method: ++ Easy implementation and evaluation + Broadband - Access to the internal coupler of the GUT is necessary - Functionality of ALC is assumed but not tested Time Domain Method: + Broadband - Expert knowledge for implementation and evaluation Load-Pull Method: -- Band-limited + Easy implementation and evaluation New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 22

23 Outlook Future Topics for Investigation Enhancement of direct calibration method based on time domain correction [5] A more general solution based on redundant load reflections could be implemented for the Load-Pull method Development of uncertainty budgets according to GUM is planned for each method New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 23

24 References [1] J. R. Juroshek, A direct calibration method for measuring equivalent source mismatch, Microwave Journal, Okt. 1997, pp [2] I. Hecht, Improved Error-Correction Technique for Large-Signal Load-Pull Measurements, IEEE T-MTT, Vol. 35, No. 11, Nov.1987, pp [3] J. Simon: German Patent DE [4] T. Reichel, Meßverfahren für den äquivalenten Reflexionsfaktor von Power Splittern, Vortragsmanuskript für das 139. PTB Seminar, Mai 1998, PTB-Bericht E-58, ISBN [5] G. Wübbeler, C. Elster, T. Reichel and R. Judaschke, Determination of Complex Residual Error Parameters of a Calibrated VNA, 69th ARFTG Conference Digest, June 8, 2007, in: 2007 IEEE MTT-S International Microwave Symposium Digest CD, ISBN: New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 24

25 New Methods for Measuring the Effective Source Reflection Coefficient of Microwave Generators 25