Make up a signal and some noise. Take the Fourier transform of both the noisy and clean signals on SPICE. Right click on the transform box to multiply the noisy signal by the clean signal.
It lowers the noise peak and raises the signal peak.
Is the multiplication in the frequency domain or the time domain?
Bret Cahill
Are you asking about SPICE or about what you do? The chain of operations don't make much sense to me, so it's hard to guess.
Rune
The d operator in the time domain takes the time derivative.
In the FFT the d operator seems to be taking the derivative w/ respect to frequency. The d turns one peak into two peaks on both sides of the original but this isn't surprising considering everything is always positive on this FFT.
What's interesting is a filter using a reference containing a derivative w/ respect to frequency works at all.
Bret Cahill
Multiplication in the frequency domain, cross-correlation in the time domain. (And you want to multiply by the complex conjugate of the signal--otherwise the phase isn't well behaved.)
Cheers
Phil Hobbs
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