A Wide-Band CMOS LC VCO With Linearized Coarse Tuning Characteristics

摘要

A pseudo-exponential capacitor bank structure is proposed to implement a wide-band CMOS LC voltage-controlled oscillator (VCO) with linearized coarse tuning characteristics. An octave bandwidth VCO employing the proposed 6-bit pseudo-exponential capacitor bank structure has been realized in 0.18-$mu{hbox {m}}$ CMOS. Compared to a conventional VCO employing a binary weighted capacitor bank, the proposed VCO has considerably reduced the variations of the VCO gain $(K _{rm VCO})$ and the frequency step per a capacitor bank code ( $f _{rm step}$/code) by 2.7 and 2.1 times, respectively, across the tuning range of 924–1850 MHz. Measurement results have also shown that the VCO provides the phase noise of ${- 127.1}~{hbox{dBc/Hz}}$ at 1-MHz offset for 1.752-GHz output frequency while dissipating 6 mA from a 1.8-V supply.