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Simulation of Subharmonically Injection Locked Oscillator (Read 836 times)
sarthak
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Simulation of Subharmonically Injection Locked Oscillator
Nov 21st, 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.
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Ken Kundert
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Re: Simulation of Subharmonically Injection Locked Oscillator
Reply #1 - Nov 24th, 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
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sarthak
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Re: Simulation of Subharmonically Injection Locked Oscillator
Reply #2 - Dec 14th, 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.
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strobing.PNG
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Ken Kundert
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Re: Simulation of Subharmonically Injection Locked Oscillator
Reply #3 - Dec 15th, 2017, 7:48pm
 
Steady state is reached when the signals stop changing.

-Ken
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