Abstract
When the device technology improves, the power supply vdd become lower,the voltage used to bias the varactor reduced consequently. As a result, the tuning range of vco reduces.This thesis use CMOS technology to simulate specification of GSM900 and DCS1800 which dual-band voltage-controlled oscillator,and can be used in RF transceiver.So,it introduce mulity channel and wide channel form the design of circuit.Beside, using switch resonator to meet the requirement of dual-band range and using the varactor to tune frequency slightly.