A −9.3-dBm Output Power 290-GHz Push–Push Mixer in 28-nm CMOS for Sub-THz Transmitter Applications

A 290-GHz push–push square mixer in 28-nm CMOS is developed for sub-THz wireless transmitters, where achieving high output power is challenging and the mixer often serves directly as the output stage. The proposed topology applies the LO to the gate and injects the IF from the source, improving isolation and enabling independent optimization of the LO switching waveform and IF drive conditions. Simulations show consistently higher RF output power than conventional co-injection mixers. To maximize output power before compression, the mixer is biased at V_G = 0.8 V and driven with P_LO = 10 dBm. An on-chip LO balun and high-power output matching network further enhance the available RF power. The prototype achieves −14.8-dB peak conversion gain, −9.3-dBm output power at 290 GHz, 6.4-mW DC power consumption, and a 27-GHz 3-dB bandwidth (270–297 GHz), outperforming prior CMOS mixers near 300 GHz in output power and power efficiency.