An X-Band LC VCO Using a New Boosted Active Capacitor with 53% Tuning Range and -202.4dBc/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.