A CMOS low-noise low-power quadrature LC oscillator

A new quadrature LC voltage-controlled oscillator circuit configuration for CMOS technology is presented. In the proposed circuit two identical cross-connected LC-VCOs are coupled together via the bulk of the cross-connected MOS transistors and the bulk of the MOS varactors. No additional components are needed for coupling the core oscillators. Therefore, no extra noise sources and power consumption are added to the circuit, which results in good phase noise and low power consumption. The circuit can operate with V_dd as low as 0.5 V. A linear analysis of the quadrature operation of the circuit is also provided. The same coupling scheme can be used for multiphase signal generation.