The Design Of Digital Frequency Upconvert In HF Ground Wave Radar

Presently, most HF Ground Wave Radars ( GWR ) adopt FMCW mode or FMICW mode and detect special distance . Its function is single and invariable. When it is used to extract ocean parameters, we hope the working parameters of radar are flexible, such as working frequency, the most detecting distance, range resolution and Doppler frequency resolution, etc. And, when detecting low speed moving objects on the sea or high speed moving objects in the air, the HF GWR's working parameters are also different. So, it is required that HF GWR can not only change radar waveform parameters, but also radar modulation mode, such as FMCW, FMICW, or pseudo-random noise ( PN ) phase modulation .The traditional analog radar receiver and transmitter are neither programmable in real time nor high performance. To develop the next generation HF GWR of our lab, we need to build a hardware-platform on the frame of Software Defined Radio (SDR), and make it be opening, digital, standard and programmable in maximum extend. The DSP, Digital Up Converter ( DUC ) and Digital Down Converter (DDC ) are key technology of a hardware-platform.A scheme to realize DUC in HF GWR is designed based on the programmable digital upconverter of AD9857. This scheme uses DSP to process digital baseband signal and control AD9857 in real-time. The modulation mode of baseband signal and working parameters of radar can be changed agilely. Experiments have proved this design can satisfy the requirements of next generation HF GWR made by Wuhan University.