Widely Tunable CMOS Voltage-Controlled Oscillator in K-Band

A CMOS LC voltage-controlled oscillator (VCO) using a 3 -bit switched-capacitor bank is proposed for improving frequency bandwidth in K-band. The capacitor bank is composed of metal-oxide-metal capacitors (MoM), which have low parasitic resistances, instead of the metal-insulator-metal capacitors to increase a quality factor of an LC tank. The proposed K-band VCO improves the phase noise characteristics in a wide frequency range by optimizing the unit size of both MoM and MOS varactor capacitors and the LC tank design based on full-EM simulation considering the interconnection characteristics in the cross-coupled oscillation core. The size of the proposed VCO was 400 gm x 610 gm, implemented on the TSMC 65-nm RFCMOS process. The overall tuning range of the proposed VCO was measured from 18.82 to 23.28 GHz at the output of a common-source buffer. The measured output power was 1.35 dBm at a 1-V supply voltage with a power consumption of 46.4 mW at 21.45 GHz. The phase noise was measured to -105.8 dBc/Hz at a 1 -MHz frequency offset. A figure-of-merit (FOM) and a FOM incorporating the tuning range (FOMT) were calculated to 179 dBc/Hz and 185.2 dBc/Hz at the frequency offset, respectively.