Low Phase Noise Quadrature Voltage Controlled Oscillator For WiMax Application

A quadrature voltage controlled oscillator (QVCO) with nested cross-coupled topology is presented. With this topology, the circuit operates at very low voltage, and achieves low phase noise with low power consumption. The nested cross-coupled topology employs two nMOS cross-couple pairs. The one with pMOS active loads and coupling transistors plays the major role. The other one, by enhancing the negative resistance, improves performances of QVCO. The prototype is implemented using TSMC 0.18-mu m 1P6M Mixed Signal/RF process technology. With 0.8V power supply, the phase noise of the QVCO is -118.3 dBc/Hz at 1MHz offset frequency from the carrier frequency of 5.73GHz. The figure of merit (FoM) is -185.3, total power consumption is 6.44mW, tuning range is 280M.Hz and I/Q are balanced.