A high performance 0.18 μm CMOS downconversion active mixer

The demanding noise figure (NF) and linearity by direct conversion and low intermediate frequency (IF) architectures make the design of active mixer extremely challenging. According to second order intermodulation and flicker noise mechanisms reviewed in this paper, we find some factors affect both the IIP2 and NF of the Gilbert cell simultaneously. AC coupling is adopted to filter out the low frequency distortion and noise from transconductor stage. A inductor is also used to tune out the parasitic capacitors at switching pair common sources to improve the NF and IIP2. The proposed mixer achieves maximal IIP2 is 72 dBm, SSB noise figure at 100 KHz is 14 dB, IIP3 is 6 dBm and conversion gain is 6 dB with 1 dBm LO, 14.4 mW power dissipation.