madengr replied the topic: Performance of Limiter with poor match on o/p

It's a parametric oscillation. Your RF signal modulates the diode capacitance, generating a negative resistance, which allows oscillation determined by some other resonance in your circuitry, probably your sliding load. I have also seen them in limiters, sometimes generating a wide-band noise burst as the limiter turns on, then it settles down. Anyway, used to be a common method of amplification prior to GaAs FET.

Steve Cripps has a Microwave Bytes on it here:

ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7010391

Walshrj99 replied the topic: Performance of Limiter with poor match on o/p

Thanks very much

MAH replied the topic: Performance of Limiter with poor match on o/p

Following on from Walshrj99's question. I am attempting to model the phenomina using a generic ADS PIN diode model with little success. Would the generic non-linear ADS pin diode model be expected to produce this effect?
I have simulated over a wide input power range with a load pull circuit on the output.
Many thanks

madengr replied the topic: Performance of Limiter with poor match on o/p

Probably depends on the diode model, but all the models I'm looking at in MWO do not have a non-linear capacitance. That capacitance is not supposed to vary anyway in a PIN diode since the charges move too slow.

Maybe instead try a non-linear capacitor. Then using a DC+ 2-tone HB simulation, use the first tone as a drive signal, then the second as a probe signal, using it look at input impedance. It would have a negative resistance to cause the oscillation. The DC is needed since the phenomenon may not work if the swing goes below 0V and the capacitance curve has odd symmetry.

This is all just a guess on my part; may try it today if I find time.

MAH replied the topic: Performance of Limiter with poor match on o/p

Ok, I will give the NL Capacitor a try.

Many thanks