A wideband LC-VCO with small VCO gain variation and adaptive power control

A wideband LC tank voltage-controlled-oscillator (VCO) is proposed. To solve the impacts of wideband operation on VCO gain (KVCO) variation and start-up constraint, a binary-weighted varactor array and a binary-weighted negative resistance array all with optimal unit values are designed. Implemented in a 0.18 μm CMOS process, the proposed VCO shows a frequency tuning range from 1.9 to 3.1 GHz, with a current consumption varying accordingly from 14.2 to 4 mA from a 1.8 V supply. With the proposed KVCO suppression technique, the KVCO varies from 50 to 60 MHz/V in the entire frequency range. The measured phase noise is −117 dBc/Hz at a 1 MHz offset from a 3 GHz carrier.