yingyang,
you got me very interested in this Block-Box method.
Could you go more in detail of the procedure?
So, you simulate the (one-port) microstrip portion of the fixture and then derive the S-Parameters from the total fixture using a one-port measurement? These are all one-port measurements, or?
It sounds as if it needs significant effort to derive the loss and phase of the fixture-half by only measuring an open (no short).
Why do you put the simulation (one microstrip line) and the measurement in parallel with Y-parameters, why not in series with Z-Parameters? What does that help?
How good was your MMIC-device when you got "perfect" agreement with TRL? Were you concerned about the phase? A digital driver (fiber optic modulator driver) might be fine, but how about a linear amp with good return loss? Even a TRL/LRM-fixture seems hard to realize up to 50GHz.
See, I have lots of questions.
Regards