A monolithic 5.9-GHz CMOS I/Q direct-down converter utilizing a quadrature coupler and transformer-coupled subharmonic mixers

We report the first monolithic 5.9-GHz CMOS I/Q direct-down converter by using a quadrature coupler and transformer-coupled subharmonic mixers (SHMs). Consuming 3.5mW, each SHM achieves a voltage gain of 10.8dB, 7.9-dBm IIP3, and 54-dBm IIP2. The input-referred dc-offset due to local oscillator self-mixing is -80.9dBm.