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linear analysis of oscillator with s-parameters

Question asked by PEPPERL on Apr 10, 2007
Latest reply on Apr 12, 2007 by wrivas
Hello, I want to design a transistor oscillator with a microstrip feedback/resonator at 24GHz and I have only s-parameters available from the transistor. To evaluate whether the oscillator will oscillate I am using the "osctest"-Tool from ADS to analyze the closed-loop-gain and analyzing the Nyquist diagramm. No matter what I do the loop gain becomes "only" 1.006 (at best) at phase=0 at 24GHz.From your experience - does it make sense to build up this oscillator even if the loop gain is only 1.006? All examples I have seen have a loop gain much greater than 1, but they are all using transistor models - not s-parameters - because they want to do HB analysis after linear simulation. What are your experience when you have only s-parameters available? Which loop gain should be reached ?