Drift specification of switch and error terms

[nosherwan shoaib abbasi]

Dear Michael,

Kindly provide the mathematical expressions for the following drift specifications in terms of S-parameters for PNA drift evalaution:

1- Switch Term Drift (dB)
2- Directivity Drift( dB)
3- Match Drift (dB)
4- Isolation Drift (dB)
5- Tracking Drift Magnitude (dB)
6- Tracking Drift Phase (degree)

Thanks in anticipation

--
Best Regards,
 
Nosherwan Shoaib

[Michael Wollensack METAS]

Hi Nosherwan,

1. You can directly measure the switch term drift using a thru connection and VNA Tools (Measurement Journal / Add Measurement Series / Mode: Drift, VNA SetUp: Swicth Terms Port: 1, 2). Then you take a look at the variation of the switch terms (Data Explorer / Norm: Mean). E.g.: If the variation is smaller than 0.001 in the real and imaginary part then you set the Switch Term Drift to -60 dB.

2. - 6. using an ECal. You calibrate your VNA every 15 minutes for one day using an ECal. VNA Tools (Measurement Journal / Add Measurement Series / Mode: ECal Drift. Then you compute the calibration error terms for those 96 calibrations. Then you take a look a the variation of the different error terms and so on.

2. - 6. without an ECal. You calibrate your VNA using a mechanical calibration kit. Then you measure a thru connection ervery 15 minutes for one day using VNA Tools (Measurement Journal / Add Measurement Series / Mode: Drift, VNA SetUp: Sx,x Ports 1, 2). Then you error corrected those thru measurements. The variation which you can see in the transmission comes mainly from the tracking drift. And the variation of the reflection comes mainly from the directivity and match drift. E.g.: If the variation in the reflection is smaller than 0.001 in the real and imaginary part then you set the Directivity Drift to -60 dB and the Match Drift as well to -60 dB.

Hope this helps.

Regards

Michael

[Michael Wollensack METAS]

Hi, 

I forgot 4. Isolation Drift. We ignore isolation drift, so we set it to a small value like -120 dB.

Regards

Michael

[nosherwan shoaib abbasi]

Dear Michael,

Thanks a lot for providing the useful information.

Best Regards,

Nosherwan Shoaib