match amplifier to oscillator

[yasbigiii]

Hello everyone,

I need to connect an amplifier to an oscillator (sine wave loop oscillator). as most oscillators input resistance of the oscillator is negative (Zin = -23-j9).
the amplifier input impedance also is Zamp = 20-30j.

My question is how can we model an oscillator (with negative resistance) in softwares like ADS to be able to use simulators like S-Param or LSSP.
the point is oscillators interact with loads, and their characteristics change with it. simulation techniques like HB or TRAN in ADS doesn't provide the tools.

I would appreciate your help
Bests

 

[FvM]

Why should a component level model of the oscillator not give correct impedances in HB and TRAN simulation?

 

[yasbigiii]

thanks for your answer
In fact, there is no problem with input impedance. if you want to use the oscillator with in other components (amplifier), to be able to do simulations like (S-Param) or LSSP you need to define ports. a source model for oscillator to see how the matching network should be.

Specifically, my issue comes from connecting amplifier to oscillator (with negative resistance) and analyze the system.

 

[vfone]

Place a buffer (emitter or source follower) and a few dB pad attenuator between oscillator and amplifier, and will solve the problem.

 

[yasbigiii]

indeed it is a straight forward solution. In fact I wanted to make it as low profile as possible. I'll do that.
If you purchase FET transistors from CEL like CE3521M4 you see that it has very low input and output impedances despite of integrated MOSFETs. I think CS config resolve the loading issue.
Thanks

 

[BigBoss]

Oscillators are not matched to next amplifiers. In order to prevent unwanted effects of the amplifier, a buffer amplifier is used and then PA can be-if necessary-matched to buffer amplifier.
Because oscillator output impedance cannot be neither simulated nor measured. Oscillators are chaotic devices
and they do not tend like other ordinary linear or nonlinear systems.