A CMOS Backgate-Coupled QVCO Based on Back-to-Back Series Varactor Configuration for Minimal AM-to-PM Noise Conversion

A 3.3 GHz CMOS quadrature voltage-controlled oscillator (QVCO) with very low phase noise is presented. The back-to-back series varactor configuration is employed in the LC tank for minimizing the AM-to-PM noise conversion. The backgate coupling for quadrature phase inter-locking further eliminates the noise contribution from coupling transistors and also reduces power consumption. The implemented QVCO in 0.18 mum CMOS technology achieved very low phase noise of -133 dBc/Hz at 1 MHz offset, where the total power consumption is 4.4 mW from a 1.0 V supply. The chip has a very high FOM of -196.6 dBc/Hz.