Microwave Frequency Technology And Its Applications

As a heart of radar and communication system, high-performance microwave frequency source plays more and more important role. Frequency synthesizing technology is the conventional method to realize frequency source. Due to the rapid development of radar, electronic countermeasure, communication, the demand on high-performance frequency synthesizer is urgent. In this dissertation, the research on Direct Digital Synthesis (DDS) technology and Phase-Locked Loop (PLL) technology is done. Then, those frequency synthesis technologies are successfully applied in three projects, microwave low phase noise and low spur fast-hopping frequency module, simulator for microwave fast-hopping frequency synthesizer, and L-band PLL signal source. Finally, the experimental results show that many performance indexes such as spur suppression, phase noise, hopping frequency time and frequency shift time of those frequency synthesizers designed in this dissertation, are superior to those of other frequency synthesizers reported in open literature.Firstly, in microwave low phase noise and low spur fast hopping frequency project, the demand on some performance indexes such as spur suppression, phase noise, fast hopping frequency time and frequency shift time is very high. In addition, the output of fast hopping frequency should be precisely synchronized with exterior synchronized signal. In order to meet those requirements, some conventional frequency synthesis schemes are carefully studied in this dissertation. It can be found out that those conventional schemes cannot meet requirement of the project. For example, the experiment shows that the scheme of"downconverting the output inside PLL and locking the intermediate frequency"always has much intermodulation spur at some frequency points. Finally, the scheme of"Double DDS+PLL, outputs are switched with ping-pong regulation"is chosen for this project. The experiment results indicate that some important performance indexes such as spur suppression, phase noise, hopping frequency time and frequency shift time of this scheme designed in this dissertation, are superior to those of other frequency synthesizers reported in open literature. At the same time, the synchronization of fast hopping frequency output and exterior synchronizing signal can be realized after time-delay program and circuit is added.Secondly, in the project of a simulator for fast-hopping microwave synthesizer, some technologies such as DDS, PLL and DS are used to synthesize fast-hopping frequency signal with controllable period. Final experimental results show that the scheme in this dissertation can meet the requirement of the project.Finally, in the project of L-band PLL signal source, how to effectively design microwave frequency synthesis circuit and how to effectively design PLL frequency synthesis circuit are studied.In short, those three projects in this dissertation include some important technologies such as fast-hopping frequency and spur suppression technology about DDS, low phase noise technology about PLL, DS frequency synthesis technology, microwave switch with high speed and high isolation, filter design and debugging, MCU control program, time order synchronization, and the system design. In this dissertation, these technologies are studied in detail and successfully applied, which might be helpful to further application of frequency synthesis technology.