Low phase noise load independent switched LC VCO

This paper presents a novel low-voltage low phase noise CMOS complementary LC Voltage Controlled Oscillator(VCO) implemented in the TSMC 0.18um CMOS process. By using capacitive feedback, dynamic switching is achieved for the current source. Detailed theoretical analysis is conducted to show, besides load independence, how tail current switching helps reduce supply voltage and improve phase noise performance by reducing drain current duty cycle for less noise up-conversion and reducing 1/f noise without adding switching bias circuits. For the proposed VCO, with 1.2V supply voltage and 2.5mA DC current consumption, phase noise of −121.3dBc/Hz at 1MHz offset from 5.4GHz oscillation frequency is achieved, and the measured FOM is −191.1dBc/Hz.