The Research And Design Of Low Phase Noise LC Voltage-Controlled Oscillator Based On Cross-coupling

Voltage controlled oscillators(VCO)are widely used in circuit systems such as phase-locked loops and high-speed clocks.Compared with other voltage controlled oscillator topologies,LC voltage controlled oscillator has the advantage of lower phase noise,so it has been more widely used.In order to achieve a low phase noise VCO,this thesis conducts research on the issue that the nonlinearity of VCO deteriorated the phase noise,and proposes an improved structure.This thesis uses the Grozkowski effect to associate the oscillator nonlinear with the phase noise,and quantifies the up-conversion of flicker noise caused by the variation of the voltage harmonic content in the oscillator.By calculating the Total Harmonic Distortion(THD)of the oscillator output voltage,the nonlinearity of the oscillator was quantified,and the effet of the nonlinearity on the phase noise in the1/?~3 region of the oscillator is analyzed.Based on the analysis results,a method to reduce the nonlinearity of the cross-coupled tube is proposed:By reducing the width W of the cross-coupled differential pair,the non-linearity of the cross-coupled differential pair can be reduced,thereby reducing the phase noise in the 1/?~3 region of the oscillator caused by the Grozkowski effect.Based on the research on the nonlinearity of the LC oscillator,this thesis proposes a transistor linearization technology based on negative feedback,and designs a low phase noise LC-VCO based on the cross-coupled differential pair linearization technology.Based on classic differential LC-VCO,A self-starting switch system was introduced into the LC-VCO,and a cross-coupled differential pair linearization technology based on negative feedback was also introduced into the LC-VCO.The self-starting switch system ensured that the starting speed of the LC-VCO is the same as the classic differential LC-VCO.The cross-coupled differential pair linearization technology based on negative feedback improved the phase noise performance in the 1/?~3 region caused by the Grozkowski effect,increased the output amplitude of the oscillator,improved phase noise performance in the 1/?~2 region.Under the TSMC 0.18-?m process conditions,simulation results in Cadence Virtuoso show that:the frequency of the proposed LC-VCO is 1.98?2.14GHz.At the center oscillation frequency of 2GHz,the phase noise are-75.9dBc/Hz and-121.5dBc/Hz at the 10k Hz and 1MHz offset frequency,which improve the phase noise by 6.0 dB and 1.6 dB.