Research On Ku-band Wide-band Frequency Synthesizer Based On DDS

Frequency synthesizer is one of key components in electronic systems,such as communication system,radar system and navigation system.It not only determines the performance of radio frequency system,but also affects the performance of signal source,such as local oscillators,reference signals and global clocks.In addition,modern electronic technology that is rapidly advancing and developing demands on many indicators of frequency synthesizer,such as operating frequency and operating bandwidth.Therefore,it is significant and valuable to research and design high-performance broadband frequency synthesizer.Based on these trends,this paper designs a Ku-band wide-band frequency synthesizer based on a direct digital synthesizer.This thesis starts with the research background and significance of frequency synthesizers,and studies and analyzes the development of frequency synthesizers in domestic and overseas.Then,it elaborates on several widely used frequency synthesis techniques,including its theories and characteristics.Based on the above research value and theories,a design scheme for realizing Ku-band wide-band frequency synthesizer based on DDS is proposed according to requirements.The scheme is implemented by dividing the system into two small systems,one is a DDS system,and the other is a 11?19GHz wide-band frequency synthesizer system.For the DDS system,the output of linear frequency modulation signals such as point frequency and sweep frequency,and the selection of different bandwidth and time width signals,are realized.For the wide-band frequency synthesizer system,wide band of operating frequency from 11 GHz to 19GHz,low phase noise and low spurious is realized with a 100 MHz external crystal oscillator.After completing the above two small-frequency synthesizer systems,the DDS system,is adopted to drive the wide-band frequency synthesizer system in two modes of point frequency and sweep frequency respectively to realize the Ku-band wide-band frequency synthesizer.As a result,the cascading systems achieve a point frequency output and a continuous frequency output of the entire Ku band.The output frequency ranges from 12GHz to 18GHz,and the output power is more than-15.8dBm.The spur suppression is less than-32dBc.The phase noise is less than-90dBc/Hz@1kHz,-90dBc/Hz@10kHz,-85dBc/Hz@100kHz and-108dBc/Hz@1MHz.