X-band Miniaturization Frequency-sweeped Synthesizer Research

As the key unit of electronic systems such as radar,communication and instrument,frequency synthesizer’s quality can direct affect the final performances of the electronicdevices.Frequency synthesizer with low phase noise,frequency agile and linearfrequency modulation (LFM) is presently the research hotspot in the area of radarsystems.In response to these problems,a X-band miniaturization frequency-sweepedsynthesizer is researched and designed in the thesis,which is based on the combinedtechnique of PLL and DDS. By LFM signal generated from DDS acting as the referenceto stimulate the PLL with mixer inside the loop,the frequency spectrum has beentransformed and the bandwidth has been expanded.By reducing the frequency divisionsof PLL,the characters of phase noise and spurs has been improved,the performance ofthe system has been achieved.At first,the basic theory of frequency synthesizer has been introduced,the principleand characters of PLL,DDS and LFM have been described.Then the design proposal isplaned according to the main characters of the project with the structure of referencefrom DDS stimulating the PLL of mixer in loop. Analysis,calculation and simulation ofeach characters such as phase noise,spur and returning time have been presented,theschematics and printed circuit board(PCB) of each part in thesynthesizer have beengiven,and the adjusting methodsand directions have been introduced.The physicalpictures and test results are demonstrated,the phase noise is-105dBc/Hz@100kHz,thereturning time is3.9μS and spur is below70dBc.Finally,the results weresummarizedand improving suggestions for further research are proposed...