An Ultra-low-voltage CMOS VCO Using Parallel Capacitor for Phase Noise Reduction

Abstract

In this work, a 7.92 GHz ultra-low-voltage LC-tank voltage controlled oscillator (VCO) is introduced. The proposed LC-tank VCO adopts a NMOS cross-coupled topology and additional parallel capacitors for low voltage operation and phase noise reduction. The measured phase noise at 600 KHz frequency offset is -98 dBc/Hz and at 1 MHz offset is -108 dBc/Hz, respectively. The proposed VCO achieves a figure-of-merit (FOM) value of -187 dBc/Hz, drawing 0.87 mW from a 0.62V supply. The proposed circuit topology is designed for ultra wide-band (UWB) applications and implemented in TSMC 0.18 mu M CMOS technology.