A 76–81 GHz active phase shifter for phased array automotive radar in 65nm CMOS

This paper demonstrates an active phase shifter in 65nm CMOS for phased array radar systems, covering dual radar bands of 76 GHz and 79 GHz. The phase shifter achieves 360-degree phase variation using a vector combining method. 4-phase quadrature signals are produced using a coupled-line type 90-degree hybrid circuit and two single-to-differential amplifiers designed with a neutralization technique for stability and gain enhancement in wider frequency range. The active phase shifter has a significantly higher phase resolution to achieve fine control of four variable gain amplifier bias voltages using high bit DACs. The phase shifter has an average gain of 2.3 to 4.3 dB at 76-81GHz, with a gain variation of less than 1.3dB for each frequency across all phase states. In addition, a novel electronic beam scanning radar system configuration is proposed. Using the proposed radar system configuration with the active phase shifter, it is possible to distinguish more targets compared to conventional DBF systems.