A zero-phase coupler for high output power millimeter-wave signal source in 65 nm CMOS

A metamaterial-based zero-phase coupler (ZPC) is proposed for coupled oscillator network (CON) to build high output power density and low phase noise 60GHz signal source in CMOS. The ZPC itself is both high-Q resonator and low-loss zero-phase shifter. The unit-cell oscillator of CON can be implemented by the ZPC, which has minimized loss for in-phase coupling when connecting with other ZPC-based unit-cells. The frequency tuning range is realized by inductive tuning at each ZPC unit-cell. A 4-unit-cell ZPC-based CON is demonstrated at 60GHz in 65nm CMOS process with measured maximum output power of 2mW, power efficiency of 2.2%, phase noise of -116.7dBc/Hz at 10MHz offset and frequency tuning range of 15.8% centered at 63.5GHz.