An assessment of a VNA electronic calibrator

Transcription

1 An assessment of a VNA electronic calibrator Presentation by Christopher Eiø Præsentation: ANAMET, NPL, torsdag 3. marts

2 Background The concept of electronic calibrators has been around for a number of years DTI project is investigating the use of electronic calibrators as transfer standards A number of papers around comparing electronic to mechanical calibrations, including J P Ide, Test driving the Wiltron 36581NNF AutoCal ANA calibrator, ANAMET Report 011, Oct 1997

3 How do they work? Essentially use a pseudo SOLT approach Modules contain several impedance standards Standards are selected through switching; no need to disconnect and reconnect standards

4 How do they work? A through standard is required for two-port calibrations Most modules offer two options for the through standard: True through Calibrator through

5 Advantages Speed: can be more than 6 times faster than a mechanical calibration Fewer connections required: maximum of 3 vs. minimum of 5 (TRL) Size: much smaller than a mechanical kit Ease of use

6 Disadvantages Limited to the individual manufacturer No direct traceability to primary length standards No proven track record of performance

7 So are they any good? How do they compare with mechanical calibrations? Calibration time Audit device measurements Non-insertable calibrations Residual directivity Residual test port match

8 Module under investigation Anritsu 36581NNF AutoCal module (yes, the very same one described in ANAMET Report 011)

9 Module under investigation Type N connectors Specified for use between 40 MHz 18 GHz Controlled by computer software (RS 232) Performs one- or two-port calibrations Offers both true and calibrator through 2-port cals Adaptor removal technique for non-insertable calibrations Anritsu 37169A 40 GHz VNA used throughout the investigation

10 Performance: speed Speed comparison carried out using different averaging values Default Fixed load 3:00 3:45 4:40 6:30 AUTOCAL 0:30 1:25 2:30 4:30 Time displayed in min:sec

11 Performance: audit devices Audit devices: NPL reflection check standards (male and female) 20 db attenuator from Type N verification kit

12 Performance: audit devices NPL reflection check standards (Port 1 female check standard) Deviation from cert (Real) - Port 1 Deviation from cert (Imag) - Port 1 Deviation Deviation Frequency (GHz) Frequency (GHz)

13 Performance: audit devices NPL reflection check standards (Port 2 male check standard) Deviation Deviation from cert (Real) - Port Frequency (GHz) Deviation Deviation from cert (Imag) - Port Frequency (GHz)

14 Performance: audit devices Two-port calibration scheme: a through connection is required But which type of through is better to use? True through Calibrator through

15 Performance: audit devices S 21 of 20 db attenuator S Calibrator through True through Cert values Phase of S Frequency (GHz) 0 Phase ( ) Cert values Calibrator thru True thru Frequency (GHz)

16 Performance: noninsertable devices Control software is able to perform an adaptor removal technique Estimates the electrical length of adaptor But how does this calibration compare to a PIMMS calibration...? Take a look at measurement of a Weinschel model 1870A power splitter...

17 Performance: noninsertable devices S 21 of power splitter S PIMMS Auto cal Phase of S Frequency (GHz) Phase ( ) PIMMS Auto cal Frequency (GHz)

18 Performance: noninsertable devices S 32 of power splitter S PIMMS Auto cal 0.24 Phase of S Frequency (GHz) Phase ( ) PIMMS Auto cal Frequency (GHz)

19 Performance: residual errors Comparison of the residual directivity and test port match: Port 1 (Left) Sliding load AUTOCAL Directivity (44 db) (42 db) Test port match 0.01 (40 db) (37 db)

20 Performance: residual errors Comparison of the residual directivity and test port match: Port 2 (Right) Sliding load AUTOCAL Directivity (43 db) (34 db) Test port match 0.01 (40 db) (35 db) Note that this does not appear to be a precision connector

21 What s left to do? Module re-characterisation Do everything again......but this time using a 36581KKF module

22 Conclusions? Seems to work well as a transfer standard Much quicker and easier to use than mechanical kit Non-precision connector lessens what could be very good performance Not necessarily indicative of all modules further work is required

23 Questions? Spørgsmåler? Vragen? Fragen? Otázky? Questions? Упрашания? Preguntas? Pitanja? سي له