An X-band LC VCO Using a New Boosted Active Capacitor With 53 % Tuning Range and −202.4 dBc/Hz FoMT

This paper presents a new boosted active-capacitor topology for wide tuning range voltage-controlled oscillators (VCO). A tuned inductor-based active-impedance-conversion circuit (LAIC) is used to multiply the capacitance of a capacitor bank and the negative-transconductance of LAIC in the proposed region of operation but without increasing losses. A boosted active-capacitor prototype in 65 nm CMOS process achieves a capacitance tuning ratio of 7.8 and a quality factor of higher than 20 across VCO’s tuning range. An X-band VCO prototype with the proposed boosted active-capacitor achieves a 53 % measured fractional frequency tuning range and phase noise of −115 dBc/Hz at 1 MHz offset, resulting in an excellent figure-of-merit-with-tuning-range (FoMT) of −202.4 dBc/Hz.