A high output power 152 GHz ON-OFF keying transmitter in 65-nm CMOS is presented. The transmitter consists of a high dc-RF efficiency push-push voltage-controlled oscillator followed by a high-speed and high-gain switched-mode power amplifier. The transmitter achieves the highest output power (3 dBm) beyond 140 GHz in silicon process, with high on-off ratio (>39 dB) and high dc-RF efficiency (3.7%). The transmitter could support 10-Gb/s data rate communication with a bit-error rate of less than 10-12.