60-GHz Power Amplifier in 45-nm SOI-CMOS Using Stacked Transformer-Based Parallel Power Combiner

This letter presents the design of a 60-GHz power amplifier (PA) using a new stacked transformer (STF)-based parallel combiner. It begins by highlighting the main limitation of the conventional millimeter-wave (mm-wave) transformer-based parallel combiners, namely, the output parasitic transmission lines. Then, a new STF parallel combiner based on three overlaying coils is proposed. Analyses revealed significant enhancements in terms of self-inductance, quality factors, and coupling factors, which lead to enhanced combining efficiency in the proposed combiner. Subsequently, a two-stage mm-wave PA is implemented in 45-nm silicon-on-insulator CMOS technology. The fabricated PA demonstrates a 3-dB bandwidth equal to 12.5 GHz (50-62.5 GHz). The output power at 1-dB compression/saturation (OP1dB/P-sat) and the corresponding power-added efficiencies are recorded as 16.2/18.5 dBm and 18.7/25.5%, respectively.