A 90-GHz High DC-to-RF Efficiency VCO with Multi-Way Transformers in 65-nm CMOS

This paper presents a high efficiency gate inductive feedback Colpitts Voltage Controlled Oscillator (VCO) operating near 90 GHz. It includes multi-way transformers at the load, which helps to enhance the DC-to-RF efficiency with boosted impedance and extended voltage swing through drain-buffer and drain-source magnetic couplings. The proposed VCO is fabricated in a 65-nm CMOS process, and showed an oscillation frequency tuning range of 87.5-92.0 GHz (4.5 GHz). Over the frequency range, the output power and the dc power consumption exhibited values of −2.8 −1.7 dBm and 6-22.5 mW, respectively. The peak DC-to-RF efficiency was 9.4 %, and the corresponding phase noise was −107.4 dBc/Hz at 10-MHz offset. The lowest phase noise at the optimum bias condition was −116.7 dB/Hz at 10-MHz offset. The chip size is 400 ⨯ 300 μm2 excluding DC and RF pads.