A CMOS 5 GHz phase-compensated quadrature coupler

A quadrature hybrid coupler implemented in a 0.18 /spl mu/m 6-metal RF CMOS process is presented. The 3 dB coupler uses on-chip lumped passive elements and provides a 90/spl deg/ phase shift at 5.4 GHz. It exhibits less than 0.7/spl deg/ phase and 0.3 dB amplitude I/Q mismatches over a bandwidth of 220 MHz. The measured figure-of-merit is 45 dB at 5.4 GHz.