Design of low power CMOS LC VCO for direct conversion transceiver

Abstract

A low power 1.2 GHz LC differential voltage-controlled oscillator (VCO) is designed for a direct conversion transceiver in 130 nm CMOS processes. It consists of a complementary current reuse structure and LC tank circuit. To produce a good tuning range and reduce losses in the tank circuit, modified inversion mode PMOS varactors and an on-chip inductor are designed with a better quality factor. The flicker noise is reduced by the PMOS tail current source connected in parallel with the capacitance. The 1.2 GHz LC VCO achieves a phase noise value of 132 dBc/Hz at 1 MHz offset and the tuning range of the oscillator is from 1.128 to 1.27 GHz for the control voltage, tuning from 0 to 1.5 V. It dissipates 245 µ W power at 0.8 V supply voltage and the figure of merit is calculated as 199.7 dBc/Hz.