A 220 to 260GHz Ultra-Compact, Calibration-Free 5-Bit Phase Shifter with 1.8° RMS Phase Error in 9HP SiGe Process

This paper presents a precise, calibration-free 220-to-260-GHz 5-bit phase shifter based on a passive trombone-like topology, implemented with reverse-saturation NPN bipolar junction transistors (BJTs). The reverse-saturation NPN BJT exhibits a significantly smaller rONCOFF and a higher off-state quality factor compared to the conventional forward-saturation NPN BJT, enabling the design of a low-loss, high-resolution phase shifter above 200 GHz. The prototype IC is fabricated in GlobalFoundries 9HP SiGe process and occupies only 0.033 mm². The phase control operates in 11.25° steps across 360° at 240 GHz, with an average insertion loss of 14 dB and a DC power consumption of 12 mW. Measurement results for 14 samples without calibration demonstrate a mean RMS phase and gain error of 1.8° and 0.74 dB at 240 GHz, respectively.