Research On Phase Noise Of Voltage-Controlled Oscillator In Frequency Synthesizer

Research on phase noise of voltage-controlled oscillator (VCO) in wireless communication is presented.First of all, two popular theories of phase noise in oscillator is viewed, which were named linear time-invariation (LTI) theory and linear time-variation (LTV) theory. The merits and drawbacks against the two theories are compared and their applications are investigated as follows: the LTI theory contains more mathematical derivation to be more accurate, but in dealing with flicker noise it perform slightly poor; LTV theory introduced several key approximations to simplify the analysis process, but it could provide intuitive and reasonable design guidelines for engineering applications.Phase noise of the ring oscillator and LC oscillator is analyzed with LTI theory and LTV theory respectively. And the expressions describing phase noise spectrum of both oscillators are also deduced in view of these two theories, which are foundation of low phase noise oscillator design.On the basis of analyzes in the fourth chapter, a complementary cross-coupled VCO with low phase noise is designed based on Chartered Semiconductor 0.35μm RF CMOS process, conforming to TD-SCDMA standard. Layout of this VCO is completed and withstands the post simulation. Simulation results show that the VCO output frequency ranges from 1.75GHz to 1.99GHz, current consumption is 4mA and the phase noise is below 120dBc/Hz at the offset frequency of 900kHz.