1-V ultra-low-power CMOS LC VCO for UHF quadrature signal generation

Design, implementation, and simulation of ultra-low-power LC-VCOs with quadrature signal generation are presented, as well as the analysis and the comparison of several different VCO topologies. The VCO topology having the best performance is then used further for quadrature signal generation. Based on a 0.18mum RF/mixed-signal CMOS process, the VCOs are simulated using 1V supply voltage. It is demonstrated that the N- & P- MOS cross-coupled pair VCO with balance resistors operating at 1.6GHz has a power consumption of 0.1mW with as low as -121 dBc/Hz of phase noise at 1-MHz offset. To generate the quadrature signals at 400MHz, N- & P- MOS pair VCOs at the frequency of 400MHz, 800MHz, 1.6GHz, divide-by-two, and divide-by-four circuits are implemented and compared. It turns out that the frequency dividers degrade the phase noise. Comparison of FOMs shows that VCO at 800MHz followed by a divide-by-two is the best choice for quadrature signal generation at 400 MHz, achieving 177muW for the VCO and 25muW for the divider. The phase noise is -127dBc/Hz at 1-MHz offset