Theoretical Analysis And Optimization Technology Research On Phase Noise In Feedback Oscillator

Oscillators including bulk acoustic wave (BAW) and surface acoustic wave (SAW)oscillators are the most basic components widely used in astronomy, physics, aerospace,radar, test and measurement, communication system and other research areas because ofits high quality factor characteristics in the HF/VHF/UHF bands. Oscillators arereference sources of various frequency sources and key devices produced the time andfrequency standards. With the development of modern electronic informationtechnology, phase noise of oscillators becomes a key factor in limiting the performanceof electronic system and frequency stability of oscillators plays a decisive role in theequipment performance. Therefore, research and analysis of the way to reduce phasenoise has the very vital significance to oscillators design and application.In the oscillators’ phase noise models, Leeson’s phase noise model is the mostintuitive and convenient to use. At present, the classic Leeson model lacks quantitativeresearch and analysis between loaded quality factor which is the biggest impact of phasenoise with the equivalent circuit parameters of resonator and the oscillation circuitparameters. This paper will reveal that the equivalent circuit parameters of resonatorand the oscillation circuit parameters have conclusive concern with the loaded qualityfactor in oscillators based on Leeson model, and this paper also proposes loaded qualityfactor formulation according to different oscillation circuits. It is applied to quantitativeanalysis and evaluation on phase noise of bulk acoustic wave and surface acoustic waveoscillators used different materials, techniques and oscillation circuits based onimproving loaded quality factor. The innovation works mainly include:1. At present, the situation of oscillator design lakes the physical insight andmethods for simple yet accurate analyzing how to optimize an oscillation circuit. Toremedy this situation, this work develops a simple but effective method for the Pierceand Butler oscillators.2. Oscillators’ phase noise models are analyzed, and the conclusive concernbetween the equivalent circuit parameters of resonator and the oscillation circuitparameters and the loaded quality factor is presented on the basis of Leeson model. On the basis of the analysis of two-port network theory, rigorous loaded quality factorformulation of different oscillator circuits is obtained. It makes up for the shortcomingthat Leeson model lacks quantitative research and analysis between loaded qualityfactor and oscillation circuit parameters.3. From an oscillator noise spectrum viewpoint, combined with actual Pierce andButler oscillation circuits, a detailed study of the impact on loaded quality factorimposed by equivalent circuit parameters of resonator and the oscillation circuitparameters is presented according to the formulation of loaded quality factor obtainedbased on physical model. Based on the analysis, the phase noise optimizationtechnology and design method of the120MHz AT-cut and SC-cut Pierce crystaloscillators,315MHz Butler common-base surface acoustic wave voltage controlledoscillator and lithium tantalite voltage controlled oscillator respectively, which are usingdifferent materials, techniques and oscillation circuits, are researched. A large numberof experimental facts prove that the method to reduce phase noise based on improvingloaded quality factor can ameliorate oscillator phase noise characteristics and has aguiding significance to oscillator design. This dissertation provides quantitative analysismethods and scientific basis for in-depth study of low phase noise oscillators andresonators.4. Temperature compensation and vibration isolation technology are in-depthstudied. A new AT-cut temperature compensated crystal oscillator (TCXO) isresearched and a two-stage passive vibration isolation system for crystal oscillator ispresented to achieve better frequency stability effectively. The formula for the crystalresonator equivalent circuit parameters with series capacitor is re-derived. The result issame as the result used much assumption including high frequency, high quality factor,and high capacitance ratio and so on. Hence, this formula can be in common use forvarious devices of low quality factor or low capacitance ratio, even for the actualinductor-capacitor network, as long as these devices have the same equivalent circuits.The application scope of this formula is expanded. In addition, theory of energytrapping is concerned in the design of bulk acoustic wave resonators, and therelationship between energy trapping and phase noise of the quartz crystal oscillator aregiven by the method combined the theory with experiment. The research of energytrapping has a guiding significance to the design of resonators in low phase noise bulk acoustic wave oscillators.