A Complementary-Coupled CMOS LC Quadrature Oscillator

Abstract

SUMMARY A novel CMOS LC quadrature oscillator (QO) whichadopts complementary-coupling circuitry has been proposed. The perfor-mance improvement in I/Q phase error and phase noise of the proposedQO, is explained in comparison with conventional QOs. The proposedQO is implemented in 0.18μm CMOS technology along with conventionalQOs. The measurement result of the proposed QO shows −133.5dBc/Hzof phase noise at 1MHz offset and 0.6 ◦ I/Q phase difference, while oscil-lating at 1.77GHz. The proposed QO shows more than 6.5dB phase noiseimprovement compared to that of the conventional QOs over the offset fre-quency range of 10K–1MHz, while dissipating 4mA from 1.4V supply. key words: complementary metal oxide semiconductor (CMOS), quadra-ture oscillator, phase noise, I / Q phase error 1. Introduction The need for quadrature signal increases continuously in to-day’s radio transceiver design for various applications suchas image rejection mixers, I/Q (de)modulators. At present,the flip-flop (frequency divider) based quadrature genera-tion is a popular method [1]. However, the drawback ishigher frequency VCO operation and poor phase error ac-curacy. The poly-phase filter is another quadrature signalgeneration circuit [2], where the drawback is the signal at-tenuation, and this leads to the addition of a power-hungrybuffer and a large chip size. The quadrature oscillator (QO)has been considered as another attractive solution which in-volves the coupling of two differential