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Guided vs Unguided Calibration

Question asked by gurkanee on Feb 7, 2012
Latest reply on Feb 8, 2012 by Dr_joel

I am doing a 2 port solt calibration in order to measure a very basic device response (a filter) between 1 GHz - 2 GHz. The measurement results seem different when I do the calibration by using SmartCal (Guided) and Unguided calibration. For both cases, I use the same calibration kit (85052D - 3.5mm). The measurement results taken with "Unguided calibration" have ripples and also S21 is not overlapping with S12 as expected for a reciprocal device (both have ripples and difference is going up to ~1dB at some points). However, the measurement taken with "Guided Calibration" is perfectly smooth and this time S12 and S21 are on top of each other. The same smooth measurement results are also observed when the calibration is done with an e-cal kit.

Do you have any idea about the reason of the ripples and non-overlapping of S12 with S21?

PNA Model is 8361A.