neoflash
Community Fellow
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Mixed-Signal Designer
Posts: 397
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Hi guys,
I'm doing a simulation of a 3rd order SD based synthesizer in time domain and its analysis in frequency domain.
Also, I'm using Perrot's PLL assistant software for reference.
The result is not that close between time domain and frequency domain. I will attach them both in the post. I'm using hspice + verilogA for time domain simulation. (Perrot's software for some reason give the same result for 3rd order and 2nd order modulator so the result from his cppsim is not used here. )
I've tried a couple of ways to correlate them but still not close enough. Not sure which result is correct.
The parameter I used:
Kvco = 1e9 Hz/v Fref = 156.25e6 Rz = 5k CB = 1n Cs = 8pf N = 19.125337 Modulator order = 3
Thanks for advice.
(As shown in the figure, time domain shows much higher noise than frequeny domain)
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