This paper presents a model of active mixers for a fast and accurate estimation of noise and nonlinearity. Based on closed-form expressions, this model estimates the noise figure, IIP3, and IIP2 of the time-varying mixer by a limited number of time-invariant circuit calculations. The model shows that the decreasing transistor output resistance, together with the low supply voltage in deep-submicrometer technologies, significantly contributes to the flicker-noise leakage. Design insights for low flicker noise are then presented. The model also shows that the slope of the LO signal has a significant effect on IIP2, while it has a little effect on IIP3. A new IP2 calibration technique using slope tuning is presented.