A 1.8-GHz injection-locked quadrature CMOS VCO with low phase noise and high phase accuracy

Abstract

Injection-locked quadrature voltage-controlled oscillators are introduced in this paper as high accuracy, low phase noise, and low-power I and Q generators. A master voltage-controlled oscillator (VCO), running at twice the output frequency, locks two coupled VCOs. The former determines phase noise while the latter sets phase accuracy, thus, breaking the tradeoff between the two parameters, the main limit of free running coupled VCOs, recently proposed in the framework of highly integrated solutions. The proposed design has been tailored to DCS 1800 and prototypes have been fabricated in a 0.18-mum CMOS technology. Experiments show a phase noise of -127 dBc/Hz and -139 dBc/Hz at 600 kHz and 3 MHz, respectively, while consuming 10 mA from 1.8 V supply. A 185-dB state-of-the-art phase noise figure of merit results. Accuracy between output signals is determined by means of image band rejection (IBR) measurements on a purposely developed single-side-band upconversion mixer. Minimum IBR among 20 samples is as large as 46 dB