Research On X-band Carrier Sources With Spaceborne Configurable Output Frequency

Due to the shortening of the development cycle of some satellites,the development cycle of the digital transmission system for satellite-to-ground communication has also been greatly shortened.However,the carrier frequency of the digital transmission system may not be determined before the launch of the satellite.Therefore,in order not to affect the development schedule of the satellite data transmission system,the carrier source output frequency in the data transmission system needs to consider a frequency-configurable scheme.The paper mainly studies an X-band carrier source circuit scheme with configurable output frequency.The paper has completed the development of a modular,highly integrated X-band frequency synthesizer.The thesis firstly reviews the typical technical solutions of configurable carrier frequencies at home and abroad.For space application,a hybrid frequency synthesis circuit scheme using the output of the direct digital frequency synthesizer(DDS)to stimulate the phase-locked loop(PLL)is designed.The main work of the thesis completes the design,debugging and testing of the DDS circuit by combining the field programmable gate array(FPGA)with the digital-to-analog converter(DAC).The DDS circuit provides a high resolution,frequency configurable reference signal for the X-band carrier source.The negative feedback mechanism of the PLL circuit can widen the system bandwidth,suppress spurious and stabilize the output signal.The DDS module adopts a four-layer high-speed digital circuit board design scheme.The PLL module adopts a two-layer microwave circuit board design scheme,and the two modules are isolated by a shielding cavity.A laboratory test platform for the spaceborne X-band carrier source was built.The performance test of the DDS module,the PLL module and the entire X-band carrier source circuit were completed.The test results show that the output range of the spaceborne X-band carrier source covers 8025MHz~8400MHz,the minimumfrequency step can reach 1MHz,the spurious suppression is better than-75 dBc,the second harmonic suppression is better than-27 dBc,and the phase noise quality is better than-120dBc/Hz@1MHz.The paper has also completed the application research of the X-band carrier source in the zero-IF receiving front-end system,and obtained the good results.Finally,according to the problems found in the existing circuit debugging and testing process,the paper proposes a further optimization scheme.The subsequent work needs to improve the power consumption and key performance of the X-band carrier source.