EVOLUTION OF DIGITALLY CONTROLLED OSCILLATORS

Abstract

Current trend of using digital or all-digital phase-locked loops (PLLs) in various communication devices introduces the usage of digitally controlled oscillator (DCO). This review paper discusses the evolution of DCOs in modern electronic devices as well as their performances in local oscillators. Even though the DCO implementation is preferable to its analog counterpart, improvements are still going on to get high performances in terms of power consumption, speed, chip area, frequency range, supply voltage, portability and resolution. This paper mainly describes the evolution of DCO, how it turns from a conventional VCO to DCO for deep-submicrometer CMOS process. The focus is to analyse and track the advances in DCO base on its performance level.