A 4.8GHz CMOS fully-integrated LC balanced oscillator with symmetry noise filtering technique

This work presents a fully integrated 4.8 GHz VCO with symmetry noise filtering technique. The VCO, with relatively low phase noise and large tuning range of 716 MHz, is fabricated with 0.25-μm SMIC RF CMOS process. It consumes 6 mA from 2.5-V supply. Another conventional VCO is also designed and simulated without symmetry noise filtering on the same process. It consumes the same current and with the same tuning range. Simulation result shows that the first VCO´s phase noise is 6dB better than the second´s at the same frequency offset from the carrier frequency. Measured phase noise at 1 MHz offset with symmetry noise filtering is -123.66 dBc/Hz. The design is suitable for various wireless communications.