An integrated RF PLL frequency synthesizer for use in RFID systems is presented.It integrates a voltage-controlled oscillator,phase frequency detector,charge pump,high-frequency dual-modulus divider,and digital programmable divider.The frequency synthesizer was implemented in a 0.18μm CMOS process.It uses a 13MHz crystal oscillator as input.The output range is from 860 to 960MHz,the phase margin is-123dBc/1MHz,the frequency step is 200kHz,and the change frequency is within 150μs.