A 0.3 THz VCO using gm-enhanced technology in 55 nm CMOS

A power combined terahertz (THz) voltage-controlled oscillator (VCO) is proposed to increase the output power. Based on the traditional transformer-feedback structure, a new negative conductance enhanced (gm-enhanced) technology is presented to enhance the start-up of the proposed THz VCO by adding additional transistors to offset the loss of the source inductance. In addition, a short transmission line is used as a zero-phase shifter to lock the three single-core VCOs for consistent frequency, phase, and amplitude. The fully integrated 300 GHz VCO design is fabricated in 55-nm complementary metal oxide semiconductor (CMOS) process. The measurement results show that by modulating the bias voltage of the transistors, the VCO can achieve a tuning range of 301.2-304.2 GHz with a maximum output power of -7.5 dBm. The chip area is only 554 mu m x 530 mu m.