Improved Gilbert mixer with high-precision automatic sweet-spot biasing and activeinductor- based harmonic suppression

A 930 MHz Gilbert mixer with improved linearity and noise figure is proposed and implemented in 0.13 μm CMOS. To achieve high linearity, the transconductance stage is biased at the sweet spot by a high-precision automatic optimum biasing circuit; and an active-inductor-based series LC network resonating around 2f_LO is implemented at the common source nodes of the switch quad. The adoption of the tunable active inductor makes this work compact and robust. Noise performance also benefits from the harmonic suppression network. Measurement results show that the proposed mixer achieves an IIP3 of 12.4 dBm and a DSB noise figure of 11.5 dB, with a current consumption of 6.7 mA from a 1.2 V supply.