I have a question about noise upconversion. I multiplied a 50MHz sinusoidal signal of DC=0 and amplitude=1V by a noise source created by two noise/freq pairs of a DC=0 source:
Freq1=0
Noise1=100nv^2/hz
Freq2=1G
Noise2=100nv^2/hz
The multiplier is from the ahdlLib which is based on verilogA and just multiplies the two input together. Here is the circuit diagram:
I looked at the absolute noise PSD at vsnsout and the USB noise of the same output node at relative harmonic=1. Here is what I get:
PSD of absolute noise @ 1Hz=50nV^2/Hz
PSD of relative harmonic=1 noise @ 1Hz=50nV^2/Hz
I understand the PSD of the relative harmonic=1 case but not the absolute noise case. I feel since Cadence reports single-sided noise so PSD of absolute noise @ 1Hz should be 100nV^2/Hz.
Could someone explain to me why? Or point me to a question that was already asked related to this?
Thanks