Abstract: An analytical approach based on linear periodic time-varying theory,is developed to analyze the noise characteristics of current-commutating CMOS mixers.Based on the derived transfer functions with memory effect of tail capacitance,a unified noise expression considering both the thermal noise and the flicker noise is rigorously derived.It enables the noise analysis of the mixers particularly for higher frequency with different IF characteristics,and is verified by simulations in Chartered 0.35μm process.