The Design Of High Performance Integrated LC VCO

The explosive growth in wireless communications has driven people to research and produce wireless transceivers at low-cost,low-power and smaller size. Voltage-controlled-oscillator is a crucial component of wireless transceivers, it provides local signal and clock for the whole circuit, its performance parameter, such as phase noise,tuning range, power consumption, have great effect on wireless transceivers.So how to design a high performance voltage-controlled-oscillator is a real challenge.In this thesis,the fundmental principles and realization methods of VCO are discussed in depth.The key technology improving the oscillator function are researched especially.Firstly, the background , history and current situation of oscillator are introduced simply.Two kinds of fundamental theory of the oscillator are presented. Also for ring VCO and LC VCO, several common oscillator topologies are listed, their circuit structure have been given out and the analysis and comparison to their characteristics have been done out.Secondly,the models of varactor and inductor in CMOS technolog are introduced. Parasitism parameters of surface spiral inductor are calculated. Several methods improving inductor quality factor are brought forward.Several common varactors are introduced, whose tuning character are compared in simulation.Then we introduce an important function parameter-phase noise. Its creation mechanism is discussed in depth.Two theory models-linear time invariant model and linear time variant model are analyzed and studied.We also summarized several techniques to reduce phase noise.At last, as a application ,a LC VCO which could been used in 2.4GHz ISM frequency channels is designed. This VCO adopt a symmetry structure of complementary cross-coupled. The varactor is I-MOS. The inductor is square spiral inductor whose Q is optimized.The results indicate that,under 1.8V power supply,the device has a center frequency in 2.4GHz and 13.7% as a tuning frequency range.It has a phase noise of -104.8dBc/Hz@100kHz offset.Finally,we use FOM(to compare the oscillator phase noise and power dissipation) to compare with similar designs on the references.This VCO has an excellent synthetical function and is able to be used in RF transceiver in wireless local area network.