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Simulators >> Circuit Simulators >> Raised noise floor in FFT (hspice)
https://designers-guide.org/forum/YaBB.pl?num=1380908045

Message started by neoflash on Oct 4^th, 2013, 10:34am

Title: Raised noise floor in FFT (hspice)
Post by neoflash on Oct 4^th, 2013, 10:34am

Hi guys,

after passing signal through an ideal LPF, FFT noise floor raised by 20dB and harmonics also increased.

problem solved after I set delmax to be very small (1ps). however, i can't afford setting it so small for performance verification.

The strangest thing is that this ideal LPF runs very clean in standalone simulation if setting delmax to 10ps.

I'm curious if any other option can help this without setting delmax to small to slow down sim too much.

Any clue why this ideal LPF simulates well standalone, but create problem in larger sim?