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Measurements >> Phase Noise and Jitter Measurements >> clarification requested
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Message started by saurabh on Apr 14^th, 2003, 1:36pm

Title: clarification requested
Post by saurabh on Apr 14^th, 2003, 1:36pm

Hi Ken!

I was going through your paper on phase-noise and jitter measurements (the one you update a few days back). Tell me if the equations S_{v} of equation 22 is the same as S_{n} of equation 35.

thanks,
saurabh

Title: Re: clarification requested
Post by saurabh on Apr 14^th, 2003, 2:56pm

Sorry for messing up my query. What I wanted to ask was that whether the variables S_{v} and S_{n} represent the same thing in equations 22 and 35 of your paper.

thanks,
saurabh

Title: Re: clarification requested
Post by saurabh on Apr 14^th, 2003, 5:17pm

I think I have an answer for my query.
S_{v} is the PSD of the total output voltage noise.
S_{n} is the PSD for the output voltage noise that has been computed at sampled time points using strobed noise analysis of spectreRF.

Is my understanding correct?

Also, how does spectreRF do the strobed noise analysis. Isn't it computationally expensive to do a complete transient noise simulation (even for period T in this case)?

thanks,
saurabh

Title: Re: clarification requested
Post by Jitter Man on Apr 22^nd, 2003, 9:08pm

Saurabh,
S_v of (22) is the power spectral density of the noisy output signal of a free running oscillator.
S_n of (35) is the power spectral density of the n_i sequence.
n_i is the sequence that results from samping the output noise of the frequency divider at every threshold crossing.

So your statements are correct, but you failed to indicate that (22) applies to oscillators and (35) to frequency dividers.

[glb]The Jitter Man[/glb]

Title: Re: clarification requested
Post by Ken Kundert on Apr 22^nd, 2003, 10:11pm

The strobed noise analysis is not a full transient noise simulation. You can think of Spectre performing a conventionaly PNoise analysis, with a sampler inserted between the output of your circuit and the input to the noise analysis. If you only ask for one strobe point, the cost of a strobed noise analysis (referred to as a time-domain noise analysis in Artist) is about the same as a conventional pnoise analysis.

-Ken