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Jul 11th, 2020, 6:15pm
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pac/pnosie simulation (Read 247 times)
NvR
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pac/pnosie simulation
Oct 21st, 2019, 4:04am
 
I have a question regarding the pnoise and pac simulations in sc-filters.pdf. The first null in the pnoise simulation is at 666.7kHz (figure 4) but where is the first null in the pac simulation (figure 6, continuous output)?

Thanks,
Nico
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Ken Kundert
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Re: pac/pnosie simulation
Reply #1 - Jan 16th, 2020, 11:37am
 
SpectreRF is often creating little puzzles like this. It always takes some deep thought to come up with possible explanations and then some experimentation to verify them.

My theory is that width of the sin(x)/x curve in the noise results is set by the pulse width (1.5μs -> 666kHz), whereas the in the PAC results of figure 6 the output is resampled with a 2.5μs period and so has width of the  sin(x)/x is 400kHz.  I am not sure why the unsampled PAC output also seems to have a 400kHz width.

Unfortunately, I do not have the time to explore this question to the depth it would require to completely explain the results.

-Ken
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