ABSTRACT
This chapter focuses on voltage- controlled oscillator (VCO) basics and LC-VCO and discusses the properties of the LC-tank and tank components. It introduces some typical topologies of LC-VCO and their advantages and disadvantages to be applied in millimeter-wave frequency. For millimeter-wave frequency there are two types of oscillators: the resonator-based oscillator and the resonator-less oscillator RC ring oscillators are a well-known type of resonator-less oscillators. An resistance and capacitance (RC) ring oscillator is popular for low frequency low cost application due to its wide tuning range, multi-phase outputs, and low power consumption. The cross-coupled NMOS transistors provide a negative resistance and add energy into the circuit to sustain the oscillation. The oscillation frequency of VCO is determined by the tank inductor and capacitor thus changing either of them could change the oscillation frequency. However in practical, inductor is difficult to be varied continuously. The normal method for frequency tuning is using varactor.
