Design Of Integrated Low Noise Oscillator

According to the development trend of crystal oscillator,in this thesis,studies and designs the method of integrated low noise oscillator as the subject,analyzes the phase noise of crystal oscillator in detail,finds out the feasible method to reduce the phase noise,simulates and verifies the method,and finally designs the integrated low noise oscillator required by the project.The main work of the thesis is as follows:1)Studying the characteristics of crystal oscillator.Analysising the physical characteristics of quartz crystal in detail.The equivalent circuit and impedance frequency characteristics of quartz crystal resonator are studied.And several common cut resonators are analyzed and compared.Therefore,SC cut quartz crysta resonator will be used in the oscillator circuit.The working principle of feedback oscillator is discussed in depth.The stability conditions of amplitude and phase of oscillator are obtained.Several kinds of common crystal oscillator circuits are studied.Focusing on the analysis and comparison of Butler oscillator circuit,Pierce oscillator circuit and Colpitts oscillator circuit.And determine the circuit type with pierce circuit as oscillator in this project design.Then,starting from the concept of phase noise,the Leeson model is introduced to analyze the phase noise,and the common expression of the phase noise is obtained.It is concluded that the phase noise can be reduced by increasing the load quality factor Q_L.2)Giving the circuit design and simulation of integrated low noise oscillator.According to the design principle of crystal oscillator,the integrated low noise oscillator is designed.And based on the definition of the quality factor of the resonator,the on load quality factor Q_L of the oscillator circuit is calculated and deduced.It is concluded that Q_L with the increase of capacitance C₁,the phase noise will also decrease with the increase of capacitance C₁.Used ADS?Advance Design System?simulation software to simulate,and the simulation results are analyzed to verify the feasibility of the method of increasing the capacitance C₁ value to reduce the phase noise.3)Making and measuring the sample of integrated low noise oscillator.Giving the PCB layout and sample of the integrated low noise oscillator.The package size of the oscillator is 20×12mm²,and then useing Keysight E5052b to measure the phase noise of the integrated low noise oscillator.By analyzing the measurement results,the performance parameters of 10MHz integrated low noise oscillator are obtained:the output power is 9.76dbm?when the load is 50??,and the phase noise is-138.6dbc/Hz@100Hz.The performance parameters of 100MHz integrated low noise oscillator are as follows:output power is 11.01dbm?when the load is 50??,and the phase noise is-130.4dbc/Hz@100Hz.The power supply voltage of the oscillator is+5V,and the package appearance is 20×12mm².All of the indexes meet the design requirements,and the design of this project is completed successfully.