A Compact 125–150-GHz Power Amplifier in 90-nm SiGe 9HP+ BiCMOS With 34-dB Gain for Phased-Array Transmitters

This paper presents a compact, high-gain D-band PA for phased-array transmitters in a 90-nm SiGe BiCMOS (9HP+) technology. Unlike prior D-band PAs that rely on multi-way power combining, this work demonstrates that a carefully optimized single-way architecture can achieve competitive output power while maximizing gain and area efficiency under the half-wavelength pitch constraint. The PA adopts a differential three-stage architecture with broadband input/output baluns for common-mode suppression, while low-loss inductor-based inter-stage networks are employed to enhance gain and bandwidth. To mitigate substrate-related loading at mm-wave frequencies, the sub-collector (subc) termination is optimized using a high-resistance tie, improving the load-pull optimum and peak performance. Measurements show peak gain of 34 dB with 3-dB bandwidth of 25 GHz (125–150 GHz). The PA achieves a measured 𝑃sat of 13.3–15.8 dBm and a peak PAE of 7.5–11% at 120–150 GHz, while maintaining a compact footprint suitable for half-wavelength antenna pitch at 140 GHz.