A Study on High-Efficiency 24-GHz CMOS Voltage Control Oscillator

In this paper, a high-efficiency CMOS voltage control oscillator (VCO) at 24 GHz is presented. It is found in this study that to enhance output power and power added efficiency of the transformer based inductive coupled VCO, high coupling coefficient and high quality factor of inductors are essential. To confirm them, we designed three transformers which have different coupling coefficient and different quality factor of inductors and fabricated to implement each of them to VCO. The measurement results showed the VCO using an inductor of "M6+M4+M3 vs. M5" which has a high quality factor of inductors exhibited the maximum output power. The measured output power of that VCO exhibited 16.2 dBm and PAE of 19.2% from 22.2 GHz oscillation frequency at =1.8 V and =1.8 V. The process technology used in this study is TSMC-180 nm CMOS.