High Performance Of Microwave Frequency Source Technology Research

Frequency synthesizers are key parts in many modern electronic and communication systems, which determine performances of these systems. Much attention is put on design of frequency synthesizers with high performances in the world, so many countries have done many researches in the field of theories and new technologies of frequency synthesizers with high performances. After continuous efforts, researchers get a lot. Now, kinds of frequency synthesizers with different patterns, structures, theories and high performances have been available, which meet applications in many fields.Starting from the basis of design, this paper mainly talks about theories of frequency synthesizers. Researches about development of frequency synthesizers are discussed, meanwhile, common skills of design of general frequency synthesizers and common structures of frequency synthesizers with high performances are introduced in this paper, however, kinds of structures, designs, advantages and disadvantages attracts much attention in this paper. Then, this paper discusses demands for frequency synthesizers with high performances in this field and difficulties of the design. Inspired by design structures aboard, a high performance frequency synthesizer with broad band, low phase noise, low spurs and quick switch between frequencies has been completed. When designing, figure of N which is the factor of divider in the feedback loop of the PLL is very small, only4, and it means that the final signals will have better phase noise. Meanwhile, in the feedback loop, there are two branches, and one uses dividers and the other use mixers, by this design the PLL will not be locked at wrong frequencies. When designing frequency synthesizers with high performances, structures with mixers will be used, however, structures with mixers have to be completed by offered with LOes, which means that LOes with high performances are needed. In addition, quick switch between different frequencies is another key point to make better frequency synthesizers which has been completed by highly qualified programs.Results from tests show that the synthesizer owns performances in the following: the frequency source with range of4.8-5.6GHz has the phase noise better than -107dBc/Hz@10kHz during the whole band and the lowest phase noise is-113dBc/Hz@10kHz offset@5.2GHz RF output; the frequency source with range of5.0-10.0GHz has the phase noise better than-94dBc/Hz@10kHz during the whole band spurs:<-50dBc. These meet the demand and are expected, so it shows that the design and structure are feasible.