Low phase noise load independent switched LC VCO

This paper presents a novel low-voltage low phase noise CMOS LC Voltage Controlled Oscillator (VCO) implemented in the TSMC 0.18-µm CMOS process. By using capacitive feedback, dynamic switching is achieved for the current source. Detailed theoretical analysis is conducted to show how tail current switching helps reduce supply voltage and improve phase noise performance. For the proposed VCO, with 1.2 V supply voltage and 2.5 mA DC current consumption, phase noise of −121.3 dBc/Hz at 1MHz offset from 5.4GHz oscillation frequency is achieved, and the measured FOM is −191.1dBc/Hz.