Research And Application Of Varactors In Radio Frequency CMOS Integrated Circuits

Electronics with Radio Frequency (RF) integrated circuits have become an indispensable part in modern life. One of the most important parts in transceivers is the frequency synthesizer, in which Voltage Control Oscillator (VCO) is a critical part. As RF transceivers always work in very high frequencies, the LC VCOs are very popular in radio applications. Since it is impossible to make the oscillator to resonate exactly on a specified frequency, the resonant frequency of LC VCO can be tuned by varactors. In this thesis, some kinds of varactors are studied: first, the structures of varactors are introduced, their advantages and disadvantages are analyzed; second, the spectre model of the best varactor-accumulation mode Metal-Oxide-Semiconductor (MOS) varactor, is modeled with ICCAP (a type of software); finally, the varactors are implemented and then demonstrated in VCO design. In addition, some basic measurement techniques about varactor, standard Compensation-MOS (CMOS) process and the detailed process for varactor are described in details. All the devices and circuits are implemented with 0.18μm Mixed Signal (MS) and RF process in Semiconductor Manufactaring International Corporation (SMIC).