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Simulators >> RF Simulators >> maxacfreq parameter in PSS analysis in SpectreRF
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Message started by ULPAnalog on Mar 16^th, 2016, 8:14pm

Title: maxacfreq parameter in PSS analysis in SpectreRF
Post by ULPAnalog on Mar 16^th, 2016, 8:14pm

Dear experts

This is regarding the maxacfreq parameter in PSS options in spectreRF. I am running a simulation with the following settings/parameters to understand how some of the parameters are being chosen by simulator. In a test circuit with clock frequency 2kHz, PSS analysis is performed with 25 output harmonics requested followed by PAC analysis with maxsidebands = 25 and fstop = 1G. With such a large fstop, I expected simulator to give a warning about sweep being truncated, which it does. However, it says that sweep has been truncated to 208.93kHz, with a suggestion to set maxacfreq = 1.00005 GHz.
Based on the spectreRF documentation, my understanding is that the the simulator sets maxacfreq to max(4*largest harmonic request, 40*fundamental). Since 25th harmonic is the largest requested, I would expect the sweep to be truncated in such a way that no input frequency produces an output greater than 200kHz. Is my understanding correct? If so, how can 208.93kHz be a valid input frequency?

The suggestion of setting maxacfreq to 1.00005GHz makes sense given that this number is 1G+2k*25.

Thanks and regards