A 2-GHz wide band low phase noise voltage-controlled oscillator with on-chip LC tank

A 2 GHz wide band low phase noise voltage-controlled oscillator (VCO) is presented. To achieve excellent phase noise performance while maintaining wide band frequency tuning characteristic, a 6-bit digitally controlled switched-capacitor bank and tail current control scheme are used. The effect of the gate length of the MOS switches on the Q-factor of the LC tank is also analysed qualitatively. The measured phase noise is -115 dBc/Hz at an offset frequency of 100 kHz from a 2 GHz operating frequency. The total tuning range is as wide as 550 MHz (30%) and the measured RF output power is about -10 dBm at the single ended output buffer. The VCO gain varies from 21 MHz/V to 45 MHz/V for the entire operating frequency. The VCO is implemented using a 0.5 μm SiGe BiCMOS process.