A new RF CMOS Gilbert mixer with improved noise figure and linearity

The noise figure of an RF CMOS mixer is strongly affected by flicker noise. The noise figure can be improved using pMOS switch circuits, which insert current at the on/off crossing instants of the local oscillator switch stage because the circuits reduce the flicker noise injection. When it is applied to a conventional Gilbert mixer, the injection efficiency and linearity are degraded by the nonlinear parasitic capacitances of the pMOS switch circuits and the leakage through the parasitic path. We propose the pMOS switch circuits with an inductor, which tunes out the parasitic components at 2f(o) and closes out the leakage path. The mixer fabricated in 0.13-mu m CMOS at 2.4-GHz center frequency has provided improved characteristics for linearity and noise figure.