Research On Low Phase Noise Microwave Frequency Synthesizer Based On YIG

The frequency synthesizer is a key module in a modern communication system.The frequency synthesizer obtains a series of discrete signals with similar precision and stability by processing the reference signal,and provides a precise local signal for the communication device.Its application is very extensive,and it is an important part of modern communications,radar systems,electronic countermeasures and other systems.The performance of the frequency synthesizer affects the working quality of the entire system to some extent.With the rapid development of electronic communication technologies,the demand for frequency synthesizers in communication systems has continuously increased.Ultra-wideband,low-phase noise frequency synthesizer is the main research direction.Frequency synthesis technology was born in the 1930 s,and it has been more than 80 years old.According to the sequence of occurrence time,it can be mainly divided into three generations: direct analog frequency synthesis technology,phase-locked loop frequency synthesis technology and direct digital frequency synthesis technology.This dissertation first introduces the research significance of frequency synthesizers,and studies the basic working principles,advantages and disadvantages of the three basic frequency synthesis techniques.Based on the advantages and disadvantages of the three synthetic methods,several common hybrid frequency synthesis techniques are discussed.Introduced the research status and development trend of frequency synthesizers at home and abroad.Then introduced the common performance indicators of the PLL frequency synthesizer,described the basic module of the PLL frequency synthesizer,analyzed the linear model of the phase-locked loop.The transfer function analysis method is used to study the high and low pass characteristics of the noise source in the phase-locked loop structure.The high-pass noise source is mainly generated by the voltage-controlled oscillator.Secondly,compared with voltage-controlled oscillators,YIG oscillators have the advantages of wider output bandwidth,lower phase noise,and higher linearity.The YIG oscillator is used in the structure of the microwave low-phase noise frequency synthesizer instead of the traditional voltage-controlled oscillators in this dissertation.Mainly introduced the working principle of YIG oscillator,studied its coarse and fine adjustment of the drive circuit,a large capacitor with a control module in parallel at both ends of the coarse interface,to reduce the phase noise while ensuring the FM frequency,using the third-order active loop filter as the fine-tuning drive,and the structure scheme of an ultra-wideband PLL frequency synthesizer based on a YIG oscillator is given.Then,we focus on the injection-locked frequency divider in the prescaler and illustrate two injection methods for the injection-locked frequency divider: tail current injection and direct injection,and analyze the injection mechanism of both.Focused on how to expand the lock range of this type of divider.An injection-locked frequency divider structure is designed.The simulation results show that the frequency divider can achieve a divide-by-two frequency in the frequency range from 13.3 GHz to 18.1 GHz.Finally,the directional coupler is studied,the basic concepts and technical specifications of the coupler are introduced,and the working principle of the Lange coupler is clarified.A Lange coupler is optimized and the coupling degree is good in the working frequency range of 2-18 GHz.