A 76-81GHz Millimeter-Wave Quadrature Transmitter for Automotive Radar System

This paper presents a 76-81GHz quadrature transmitter designed in a 55nm CMOS technology for automotive radar applications. The transmitter includes a quadrature up-conversion mixer and a quadrature voltage-controlled oscillator (VCO). A transformer-based I and Q signal combiner is developed to achieve a high image rejection ratio (IRR). The RF amplifier employs inter-stage inductor and neutralization capacitor to improve the RF output amplitude and isolation. A novel high Q-factor switched coupled transmission line (SCTL) and in-phase injection-coupled VCO technique are developed to improve the tuning range of the quadrature VCO and maintain low phase noise at the same time. Post-layout simulation results show that the transmitter achieves an OP1dB of 2.6dBm, a conversion gain of 2.94dB and an IRR of 30.7dB.