In 2003, a digitally controlled oscillator (DCO) for cellular mobile phones was first proposed and demonstrated, and after that DCOs are widely used along with the rapid development of wireless communications. DCOs based on LC structure gain an advantage over ring oscillators in phase noise and thereby become research hotspot during the last decade. This paper presents a review of inductance capacitance (LC)-DCOs classified by circuit topologies and performance. For each DCO structure, the principle exposition and performance analysis are given in detail. Moreover, a comparison among all kinds of DCOs mentioned in this paper is presented in tabular form. Finally, we discuss the obstacle to the development of DCOs and the possible tendency for future work in summary.
