Hi!

I am trying to simulate a frequency multiplier. The oscillators are simple ring oscillators oscillating at 2GHz made form inverters.What the multiplier circuit is that it cancels the fundamental tone and retains/preservs the 3rd harmonic(3,6,9...) and cancels the other harmoics like 1,2,4,5.......

The problem;

I am interested in looking at the Phase noise at the combiner output oscillating at 6GHz. The output signal has a voltage swing of around 900mV. The setup does not have any ideal blocks in it. In the PSS options form I donot check the oscillator option (I read a post suggesting this in case of a driven circuit, which I assume this multiplier to be)

When I run pss using shooting method it does not converge. I have tried changing the tstab (increasing it), changing the method from trap to gear2 etc. But I can't get the pss to converge.

When I run PSS using the HB method the pss does converge but the Phase noise at the comes out to +150dbc/Hz which is a unrealistically large value (opposed to the theroratical results).

Running a pss+pnoise for a single ring oscillator works fine. I would be grateful if someone could guide me what could be the problem or if this is the right way of simulating this kind of circuit,

Regards,

MTP

I cannot post the image so here is a link to the circuit diagram

https://www.dropbox.com/s/zb4e5175lyut8sv/FrequencyMultiplier.jpg