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Simulators >> RF Simulators >> Simulation of Subharmonically Injection Locked Oscillator
https://designers-guide.org/forum/YaBB.pl?num=1511260500

Message started by sarthak on Nov 21^st, 2017, 2:35am

Title: Simulation of Subharmonically Injection Locked Oscillator
Post by sarthak on Nov 21^st, 2017, 2:35am

Hello,
I am trying to simulate an injection locked oscillator where the injection frequency (25MHz) an integer fraction of the oscillator frequency (5GHz). If I try to use PSS I have to set beat frequency very low and it does not converge. So I wanted to use QPSS but it asks to specify two periodic input tones when I have just the injection frequency as the input. Could anyone please suggest how do we do the phase noise simulation of Subharmonically locked oscillator.

Title: Re: Simulation of Subharmonically Injection Locked Oscillator
Post by Ken Kundert on Nov 24^th, 2017, 6:55pm

An injection-locked oscillator should be simulated as a driven circuit, not as an autonomous circuit.

Choose the 'beat' frequency to be the fundamental frequency (the common submultiple of the stimulus and the locked oscillation frequency), and choose tstab to be large enough so that the oscillator reaches lock before tstab expires.

To confirm that you have the 'beat' frequency and the tstab correctly, you can run a transient analysis with strobing. You should set the strobe frequency equal to your chosen beat frequency and simulate for at least tstab. With strobing, any signal you choose should appear to either settle or at least be close to settling by the time you reach tstab.

-Ken

Title: Re: Simulation of Subharmonically Injection Locked Oscillator
Post by sarthak on Dec 14^th, 2017, 1:35pm

I tried to do transient simulation with strobing and have attached the results. I do not understand how will I get to know that the steady state has been reached. As you suggested, I kept the strobe frequency equal to the injection frequency (which is same as beat frequency). The plot in the attached file shows the outputs (positive and negative) of a differential ring oscillator.

Title: Re: Simulation of Subharmonically Injection Locked Oscillator
Post by Ken Kundert on Dec 15^th, 2017, 7:48pm

Steady state is reached when the signals stop changing.

-Ken