A G-Band 5-Bit Vector-Modulator Phase Shifter With 52-GHz Bandwidth for Phased-Array Systems in 0.13-μm SiGe BiCMOS

This article reports a 5-bit wideband vector-modulator phase shifter (VMPS) for submillimeter-wave (sub-mmW) and terahertz (THz) phased-array systems. To achieve a high-resolution broadband phase-shifting feature, a comb-shaped differential quadrature coupler is proposed to reduce the phase/amplitude imbalances of in-phase and quadrature signals across the broadband frequencies. In addition, to mitigate the impact of the input impedance variations of the variable gain amplifier-based vector modulator (VM) on phase characteristics, fourth-order input matching networks are adopted for the VM modules. Fabricated on a 0.13- $\mu $ m SiGe BiCMOS process, the chip occupies a core area of 0.15 mm² and consumes 25.6 mW. Measured results show that the VMPS achieves 360° coverage with 64 states and provides 5-bit phase accuracy from 184 to 236 GHz, exhibiting near calibration-free characteristics. It features $a \lt 7.5^{\circ }$ rms phase error in 190–230 GHz and $a \lt 1.5$ -dB rms amplitude error in 180–230 GHz.