High-Efficiency, Coupler-Based D-Band InP PA Stages With Output Power Above 16.4 dBm
D. Yan, A. Cooman, M. Ingels, Y. Zhang, and P. Wambacq.
IEEE Transactions on Terahertz Science and Technology, Jan. 2026
This work presents a systematic design and comparison of D-band differential power amplifier (PA) stages in a 250-nm InP HBT technology, focusing on enhancing efficiency and stability. We introduce a horizontal-finger (HF) common-base layout that achieves robust stability without the performance trade-offs of conventional stabilization techniques. Two coupler-based output matching networks—a transformer-like coupler (TLC) and a straight-line coupler (SLC)—are implemented to evaluate the trade-offs between single-unit performance and power combining scalability. The TLC-based PA achieves a 33.6% collector efficiency (CE) with 17.5 dBm saturated output power (Psat) at 140 GHz, maintaining >25% CE across 120-150 GHz. The SLC-based PA demonstrates an alternative path optimized for series power combining. This work provides design insights into stable power cores and efficient combining topologies for future THz systems.