Low Noise And Low Spurious Microwave Agile Frequency Source

From the early 70s, when direct digital frequency synthesizer (DDS) technology was put forward, it became the focus. Its high frequency switching speed and the excellent frequency resolving attract large number of scientists to do further research on DDS. As a result,DDS has gotten considerable progress. But with its digital system, it has the shortage of too narrow bandwith and bad spurs level. Meanwhile, PLL techonlogy also has the contradiction between the frequency switching speed and frequency resolution. Just under the thinking of above, we do some researches on microwave frequency synthesizer that by using the method of DDS+PLL to improve the performance of the system.The author's main work in this subject is divided into three parts. Firstly, the distribution and the restrain menthods of the DDS super. Secondly, the structure of PLL and the designing are discussed at length in this section. Thirdly, the performance of DDS, PLL and ADF4113 is introduced sketchily. At last, the testing results of this subject are proposed in detail.The testing result has been abtained that the phase noise level is –110dBc/Hz@10kHz, the output SFDR is –72dBc, the frequency turning range is 620MHz～684MHz, frequency switching time is fewer 5(s, and the step length is 0.5MHz.