A Single-Stage Feedback-Feedforward D-band LNA in SiGe BiCMOS

This paper presents a compact, low-power D-band LNA for broadband sub-THz communication and sensing, implemented in 55nm BiCMOS. Based on a cascode, the design addresses the gain limitations due to the operation near fmax and over large fractional bandwidths by applying gain boosting to both the common-emitter and common-base via a combination of reactive feedback and feedforward. The trade-off between gain boosting and bandwidth is analyzed, and the maximum boosting is set to preserve broadband operation. Interstage and output matching exploit dual-resonance to maintain bandwidth. Measurements show 14.5 dB gain over 50 GHz and a minimum NF of 4.8 dB. The feedback network enables dynamic DC power expansion, yielding a peak OP1 dB of 2.8dBm at 12.2mW and a record 15.5% power efficiency. Compared to similar sub-THz LNAs, the design achieves a 3× improvement in FoM, validating its effectiveness.