A wideband LC VCO with small gain variation for 24GHz FMCW frequency synthesizer

摘要

This paper proposed a wideband LC voltage-controlled oscillator (VCO) for FMCW frequency synthesizer with a large KVCO but small gain variation. An unequally biased varactor bank is used to ease gain variation problem, and a novel compensation circuit using a tunable negative-inductance cell is applied to further reduce gain variation over the whole tuning range without adjusting dead zones. Implemented in TSMC 65nm CMOS technology, the proposed VCO employs a single tuning curve to cover the required 23.65GHz~26.10GHz and achieves less than 4.3% gain variation with KVCO varies from 1.980GHz/V to 2.066GHz/V. Drawing 5.36mA-7.42mA from 1.2V, the phase noise is -95.9dBc/Hz to -98.5dBc/Hz at 1MHz offset across the tuning range by operating the transistors in Class-C mode.