A Low Noise VCO with Quadrature Prescaler for UHF RFID Reader

A low phase noise CMOS LC VCO working at 1.8 GHz with quadrature prescaler for single-chip UHF 860 - 960 MHz RFID reader is proposed in this paper. The symmetrical filtration technology is adopted to suppress noise for complementary cross coupled LC VCO. FOM method is applied in low-noise VCO design. Injection locked prescaler with ring oscillator core can provide wide locking range. The proposed LC VCO and prescaler are implemented in IBM 0.18 mum RF CMOS technology. The measurement results show that the VCO achieves a phase noise of -132 dBc/Hz at 1 MHz offset from 1.8 GHz while drawing 10.5 mA from a 3.3 V power supply. The tuning range of the proposed LC VCO covers from 1.71 GHz to 2.19 GHz. The locking range of the proposed prescaler is 66.35% with in-phase and quadrature outputs.