Phase Noise Cancellation in a Mixer Circuit: Analysis Using a Random Phase Function.

Abstract : A stochastic signal model is used to study the phase noise suppression in an ideal mixer circuit. The phase noise in a harmonic oscillator is modeled by a sinewave containing a random phase term. The random phase term is a random walk stochastic process. The problem is to calculate the phase noise reduction (i.e., the decrease in sideband power) which occurs when the oscillator signal is coherently mixed with a time delay replica of itself. The results confirm the validity of the well know engineering formula for the phase noise reduction as a function of the time delay. An improved formula is also obtained. Although the results are derived for a pure sinusoidal oscillator, the same analysis can also be applied to modulated signals such as FMCW, etc.