Design of low phase noise LC VCO for UHF RFID reader

A low phase noise CMOS LC VCO (Voltage controlled oscillator) for UHF RFID (Radio Frequency Identification) reader is designed. The quadrature output differential signal is achieved through Source-Coupled-Logic frequency divider-by-two circuit. The circuit is implemented with the SMIC 0.18 um MOS technology and the simulator of Cadence SpectreRF. The simulation results show that the frequency range of VCO is from 1620 MHz to 2020 MHz before frequency divider and phase noise of -127.5 dBc/Hz at 1 MHz offset at oscillation frequency of 1.8 GHz. The frequency rang of VCO is from 810 MHz to 1010 MHz after frequency divider by two and the phase noise of -133.5 dBc/Hz @1 MHz offset at the frequency of 900 MHz.