A Bi-directional 5-bit 131.5-150.5 GHz Digital-Programmable Phase Shifter With 2.1°/0.3 dB RMS Phase/Gain Errors in 40 nm CMOS

This paper presents a bi-directional 5-bit digital-programmable passive vector-modulated phase shifter in the 40 nm CMOS technology for millimeter-wave and terahertz phased-array systems. The circuit consists of a quadrature coupler, an enhanced edge-coupling balun, a phase-compensated vector modulation array (PC-VMA), and a Wilkinson power combiner. Proposed PC-VMA utilizes the stair-like metal layers to form large parasitic capacitance to the ground, which enables the signal paths to emulate zero-impedance transmission lines, thus ensuring the phase consistency of the input and output signals of each transistor in the array and reducing the phase and gain errors of the phase shifter. Under 12-bit digital control, the fabricated prototype features a phase shifting range of 360°, 11.25° resolution, and RMS phase/gain errors of only 2.09-7° and 0.25-1 dB, respectively, covering the 131.5-150.5 GHz operation frequency. The circuit core occupies 0.19 mm2.