Impact of Noise Figure on Phase Noise - RF Cafe Forums
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Post subject: Impact of Noise Figure on Phase
Posted: Fri Jul 22, 2005 3:03 pm
Lets say you have a signal at a known frequency with a
known amount of phase noise, and you pass the signal
through a fixed attenuator, is there a way to
calculate/estimate what impact the attenuation has on the
phase noise of the output signal?
Posted: Sun Jul 24, 2005 11:30 am
Joined: Sun Aug 03, 2003
2:02 pm Posts: 653 Location: Erie, PA
My guess is that the effect of the
attenuator on phase noise would be similar to the intended
signal and noise. You would need to perform a cascade
analysis for the path where the phase noise is first
injected and treat that component of the total signal as a
separate signal that is summed with the intended signal.
The discrete phase noise component would be attenuated
by an amount equal to the total Gain in the path from the
phase noise injection point and the continuous phase noise
component would be subject to the total Gain and Noise
If the phase noise is present on the signal
at the system input, then it is treated to the same
effects as the rest of the intended signal and noise.
If it is injected in an LO at a mixer, then the phase
noise component is determined by a separate cascade
comprised by the path the LO signal takes.
last case, for a real system the summation of the two
components [(intended signal + noise] + [LO + phase
noise)] would be a point-by-point vector addition, so a
simple scalar summing could produce erroneous results.