Noise analysis for sampling mixers using stochastic differential equations

We analyze three different sources of noise in a sampling mixer working at radio frequency (RF) or intermediate frequency. External RF and intrinsic noise are analyzed using conventional frequency domain methods. External local oscillator (LO) noise is analyzed in the time domain by solving a stochastic differential equation. We are able to take into account the time varying aspect of the LO noise coupling, and show that LO noise becomes important at high frequencies. An analytical expression for LO noise is obtained, which can be used to guide mixer design. LO noise is in addition to LO jitter, which should be combined with noise analysis to give a complete picture.