A Wideband Voltage-Controlled Oscillator With Gain Linearized Varactor Bank

A new gain linearized varactor bank suitable for wideband voltage-controlled oscillators (VCOs) is presented in this paper. The VCO tuning gain linearized techniques, namely the gain variation compensation and linear tuning range extension techniques, are used in the proposed varactor bank to achieve a further reduced VCO tuning gain with low variation. The phase noise from Amplitude Modulation to Phase Modulation up conversion is considerably improved thanks to the reduced VCO tuning gain. Fabricated in a 0.18-μm CMOS technology, a 3-bits VCO prototype employing the proposed varactor bank achieves <;5% gain variation at the output frequency from 4.1 to 5 GHz, and exhibits maximum power consumption of 7.2 mW at its peak frequency, 5 GHz.