# Simulate the jitter of a ring oscillator in Cadence

1. ## Simulate the jitter of a ring oscillator in Cadence

Hi,

i want to simulate the jitter/phase noise of my ring oscillator.
The oscillator frequency is about 2 GHz.

Actual i just simulated the transient behaviour.
I took a look at tutorials, but I'm not sure with all that settings for correct noise simulation.

My idea was, to simulate 'transient noise' in transient simulation and measure the jitter with an eye-diagram.
I did read some stuff about PSS and PNOISE and that this would be the better way.

Which is the best way. Can you give me a short to do list, what I must simulate?

Greetings,
DaHomer

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2. ## Re: Simulate the jitter of a ring oscillator in Cadence

Okay, my PSS and PNOISE works now.
I calculated the Phase Noise spectrum:

But now my problem is, that I have no idea, how to calculate the RMS-Jitter.
RMS_Jitter = 2*sqrt(10^(N/2)) with N = Integral{lower_bound}{upper_bound}(PhaseNoise df)

How i choose the lower and upper bound for the integration for a oscillation frequency of 2 GHz?
I wonder about the high phase noise (over 50 dBc) at ~10 Hz, is that possible?

Greetings!

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3. ## Re: Simulate the jitter of a ring oscillator in Cadence

Use PSS/TDnoise with FullSpectrum-Pnoise.
Upper bound is Fundamental_frequency/2.

However it is very difficult and unreliable to determine lower bound.

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4. ## Re: Simulate the jitter of a ring oscillator in Cadence

Originally Posted by pancho_hideboo
Use PSS/TDnoise with FullSpectrum-Pnoise.