A 90-100 GHz SiGe BiCMOS 6-Bit Digital Phase Shifter with a Coupler-Based 180° Unit for Phased Arrays

This paper presents a 90-100 GHz wideband digital phase shifter with a fine resolution of 5.625°, implemented in a 0.13 μm SiGe BiCMOS process. A switch-type architecture with six cascaded units, including a novel 180° cell based on a broadband coupler, enables full 0-360° phase coverage while improving phase accuracy, bandwidth, and process robustness. Post-layout simulations demonstrate an insertion loss below 15.5 dB, an RMS phase error under 2.3°, and an RMS amplitude error better than 0.9 dB across the 90-100 GHz band. The total chip area, including test pads, is 0.39 mm², making the design compact and well suited for high-density phased-array applications.