Hybrid Cross Coupled Differential Pair and Colpitts Quadrature Digitally Controlled Oscillator Architecture

Abstract

Growing importance of wireless communication systems forces reduction of power consumption of the designed integrated circuits. The paper focuses on minimization of power consumption in a digitally controlled oscillator (DCO) that can be employed as oscillator in GPS/Galileo receiver. The new hybrid architecture of DCO combines good phase noise performance of a Colpitts oscillator and relaxed startup conditions of a cross-coupled differential pair oscillator. The proposed new DCO generates a quadrature signal in a current reused frequency divider. Such solution allows of the dissipated power to be reduced. The DCO has been implemented in 110 nm CMOS technology. It generates output signal in frequency range from 1.52 GHz to 1.6 GHz and consumes 1.1 mW from 1.5 V supply voltage. The measured phase noise equals −116 dBc/Hz at 1 MHz offset from 1.575 GHz output signal.

Layout of MOS Varactor with Improved Quality Factor for Cross-Coupled Differential Voltage-Controlled Oscillator Applications

“…In general, the cross-coupled VCO is popular for GHz-order RF systems because of its low-phase noise characteristics [1]. Accordingly, studies on various modified VCOs based on the cross-coupled type have been actively conducted [2][3][4][5][6][7][8][9]. However, as RF systems become more sophisticated to cover a higher data rate, further improvements in the phase noise of the VCO are required.…”