A wideband LC-VCO with small VCO-gain fluctuation for mobile DTV application

A novel wideband LC-tuned Voltage-Controlled Oscillator (VCO) with small VCO-gain (Kvco) fluctuation was developed. A combination of parallel switched varactor array and switched capacitor array was introduced into conventional LC-tank, and both arrays are controlled by the same code and switched simultaneously. In this way small VCO-gain fluctuation was achieved and no additional calibration process of Kvco was needed. The proposed resonator was applied to two wideband LC-VCOs implemented in a 0.25 μm CMOS technology for mobile DTV application. Each VCO achieves a Kvco fluctuation of less than 16%, which is one-fourth of that in a conventional wideband LC-VCO, with a tuning range of more than 46%. The whole output frequency range is from 0.82 to 1.85 GHz, and the power consumption varies accordingly from 6.4 to 3 mA from a 2.5 V supply. The measured phase noise is −127 dBc/Hz at 1 MHz offset from a 1.17 GHz carrier.