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How to understand and use the "negative inductance value" in calibration?

Question asked by linan0827 on Apr 14, 2013
Latest reply on Apr 19, 2013 by linan0827
Hi,

In some calibration standards the cal kits have negative inductance coefficients. It is not hard to understand if it is only some parts of coefficient set, like L1, L2 etc, in the short stand. However, for some on-wafer calibration standard, there is only one negative inductance is placed in front of, let's say, LOAD standard. At this point, things become strange, for these reason in my point of view:

1. Normally a series inductor or a shunt capacitor can be seen as a piece of transmission line, with infinite/0 characteristic impedance respectively. However, an inductor with negative value, should we consider it as a series negative inductor, or a shunt positive capacitor?

2. This inductor/capacitor translation only works at some specific frequency. At which frequency should we perform such a translation?

In real application, if a negative inductance is considered as the coefficient of a LOAD standard, is it correct to translate it to a negative delay time? Otherwise, I could only consider translate it to a positive value, but different at different frequency, which is implying a dispersive effect.

I am not sure what is the best practice here and it seems there is some problem with our calibration. So I would like to make the fundamental theory here clearer. Thanks in advance for any reply!

Regards,

NL  

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