Design of digital frequency synthesizer for ground-wave synthetic pulse and aperture radar

An approach to design a digital frequency synthesizer of multiple carrier frequencies for the ground wave synthetic pulse and aperture radar,with multiple DDS chips AD9854 is presented.The synthesizer generates multiple signals of linear frequency modulated interrupted continuous wave (LFMICW) for simultaneously transnuission.The signals should have different carrier frequencies and controllable initial phases.An effective method of generating LFMICW by DDS is analyzed.The design of the FPGA control logic and the realization of the computer serial communication protocol are presented as well.The experimental results indicate that the phase noise of the frequency synthesizer is-92.6 dB cat 1 Hz,which meets the stability demands of high frequency ground wave radar for long-term coherent integration.