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 Jitter in Limiting Amplifier (Read 15366 times)
 Hans New Member Offline Posts: 2 Los Angeles, CA Jitter in Limiting Amplifier Jul 24th, 2003, 4:29pm   I have a question regarding the way PNoise simulates sampled noise (tdnoise). Let's say we have a limiting amplifier that is stimulated with a sinusoid at frequency fo. The amplifier clips the signal into somewhat of a square wave and the output will be accompanied by the noise generated within the amplifier. This signal is then presented to some logic block with logic threshold VTH,LOGIC. The general idea is to run a tdnoise simulation and look at the noise voltage at the output when the output signal crosses VTH,LOGIC. When plotting the integrated output noise voltage the SpectreRF User Guide suggest using the range from zero to the PSS fundamental frequency. Does this mean that the PSD for a sampled time point is only integrated over that interval? Or is the computation done in the time domain from zero to 1/fo? How are frequencies above the fundamental taken into account? (i.e. what exactly is being integrated?) The following quote from the Affirma RF Simulator (SpectreRF) User Guide (Product Version 4.4.6 - April 2001) is the source of my confusion:"Type 0 as the start frequency and the PSS fundamental frequency as the stop period. For example, type 1G if the PSS period is 1ns." (p. 909).I would really appreciate it, if someone could clarify this for me. So far the Cadence documentation has been rather vague yet I believe someone out here must have stumbled across the same problem. Thanks in advance, Hans Back to top IP Logged
 pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless Re: Jitter in Limiting Amplifier Reply #1 - Jul 28th, 2003, 8:08am   Description about TDnoise in SpectreRF manual is wrong. TDnoise setting has to be like following.(1) Sweep Range for Pnoise.This should be from 0 to PSSfund/2.Sweep Range is the one we fill in the PNoise analysis form. For regular pnoise(noisetype=source), the range could be from 0 to any frequency we want.For time-domain pnoise (noisetype=timedomain), the range should be from 0 to PSSfund/2.Time-domain noise PSD is periodic with PSSfund so PSD is symmetric around PSSfund/2. (2) Frequency Integration Range of PSD. This should be from 0 to PSSfund/2.For time-domain noise (noisetype=timedomain), SpectreRF calculates the PSD of the discrete (or sampled) noise at t0+n*T (T=1/PSSfund, 0<=t0<=T, -infinity