The direct digital synthesis techniques（DDS） could often be used to generate multi-frequency HF ground wave radar signal waveform.Using the field programmable gate array（FPGA） to design the DDS signal generator is more flexible than the use of dedicated DDS chip.The FPGA chip is used in designing the multi-channel multi-frequency HF ground wave radar DDS digital signal generator.This system could include the PC software

LXI interface circuit

control module

multi-channel DDS system

and the Adder Module.The output of the DDS signal generator will be four-channel single-frequency signal and multi-frequency signal which is synthesized by the four-channel.The output frequency band is 3-30 MHz.What is more

the output signal spurious-free dynamic range（SFDR） is better than 62 dB.Besides

the output signal phase noise is better than 132 dB/Hz.After the designing and the experimental testing

the DDS Signal Generator meets the requirements of transmitting and receiving system of Multi-Frequency HF Ground Wave Radar.