Design of Multi-carrier Digital Frequency Synthesizer for Coast-ship Multi-static GroundWave OTH Radar

To design a digital frequency synthesizer of multi-carrier frequencies for the coast-ship multi-static ground wave over-the-horizon (OTH) radar, an analysis of the approach has been made by using multiple DDS chips AD9854. The constitution of the radar is introduced briefly. The synthesizer generates multiple signals of linear frequency modulated interrupted continuous wave (LFMICW) which should have different carrier frequencies as well as controllable initial phases and will be transmitted simultaneously. An effective method for generating LFMICW by advanced DDS technology is proposed in the paper. The designs of the FPGA control logic and the peripheral circuits are presented as well. The synthesizer has been implemented in the experimental radar system. The experimental results indicate that the phase noise of the frequency synthesizer is -92.6dBc@1Hz, which has met the stability demands for long term coherent integration in high frequency ground wave radar