A CMOS LC-VCO with enhanced PSR based on common-mode replica compensation

A novel 1.575 GHz CMOS common-mode replica compensated LC voltage-controlled oscillator with enhanced power supply rejection (PSR) is introduced for global position system (GPS) system-on chip application. In order to improve the PSR and reduce the power consumption, additional regulating circuit with feed forward and feedback amplifiers are implemented using transconductance stages with common-mode replica compensation which has little impact to oscillator phase noise performance. The simulation results under mixed-signal 0.18 μm 1P6M process show that this novel oscillator achieves -68.5 dB PSR at low frequency. The proposed system exhibits phase noise of -123.3dBc/Hz at a 600 KHz offset from a 1.575 GHz carrier, 21% tuning range while only consuming 3.63 mA in 1.8 V power supply.