A low phase noise and low power series coupled quadrature VCO using reconfigurable LC tank

To design a multi standard and a multi band transceiver, a quadrature voltage controlled oscillator (VCO), which has a wide tuning range, is essential, while providing low phase noise with low current consumption. In this paper, a dual band quadrature VCO in 0.18 mum CMOS process is presented. To accomplish dual band operation, reconfigurable LC tank is adopted. Series coupling transistors are attached to generate quadrature phase signal with low phase noise and low power consumption. To improve phase noise performance, a current source is eliminated, and a filter inductor at the common source node is added. The measured phase noises of low frequency mode and high frequency mode are -123.8 dBc/Hz and -115.06 dBc/Hz at 1 MHz offset frequency and FoM of -181.8 dB and -180.5 dB with 6.8 mW power consumption.