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 implemented in 28-nm CMOS for sub-terahertz wireless transmitters is presented. Achieving high output power near 300 GHz in CMOS is challenging because mixers often serve directly as the transmitter output stage without a dedicated power amplifier. In the proposed architecture, the LO signal is applied to the gate while the IF signal is injected at the source, enabling improved isolation and independent optimization of LO switching and IF drive conditions. Simulation results show that this injection scheme provides higher RF output power than conventional mixers. The mixer is biased at VG = 0.8 V and driven with PLO = 10 dBm to maximize output power before compression. With an on-chip LO balun and optimized matching network, the prototype achieves -14.8 dB peak conversion gain and -9.3 dBm output power at 290 GHz. Compared with prior CMOS mixers near 300 GHz, the proposed design achieves competitive output power.