LC voltage controlled oscillator in 0.18-mu m RF CMOS

An integrated low-phase-noise voltage-controlled oscillator (VCO) has been designed and fabricated in SMIC 0.18 mu m RF CMOS technology. The circuit employs an optimally designed LC resonator and a differential cross-coupling amplifier acts as a negative resistor to compensate the energy loss of the resonator. To extend the frequency tuning range, a three-bit binary-weighted switched capacitor array is used in the circuit. The testing result indicates that the VCO achieves a tuning range of 60% from 1.92 to 3.35 GHz. The phase noise of the VCO is -117.8 dBc/Hz at 1 MHz offset from the carrier frequency of 2.4 GHz. It draws 5.6 mA current from a 1.8 V supply. The VCO integrated circuit occupies a die area of 600 x 900 mu m(2). It can be used in the IEEE802.11b based wireless local network receiver.