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.