The Design Of The Digital Data Acquisition System For HF Hybrid Sky-surface Wave Radar

High frequency surface wave radar(HFSWR)transmits electromagnetic wave(3-30MHz)across the ocean surface,and the electromagnetic wave can interact with the rough sea surface.This interaction will produce the first-order scattering and second-order scattering.By the analysis of the spectrum,we can obtain the current,wind and wave dynamic parameters of the sea surface.With the development of the HFSWR in the past 40 years,it has become one of the most important remote sensing equipments for marine monitoring.To enlarge the dection range of the sea area,the HF Hybrid Sky-Surface Wave Radar is the support of the 863 HighTechnology Project of China.The detection mode of Hybrid Sky-Surface Wave Radar is different from the HFSWR detection mode.By the combination of the surface wave radar and the sky wave radar,more ocean backscattering echoes can be detected.In addition with the advantage of the ground wave,HF-Hybrid Sky-Surface Wave Radar has a great significance for ocean exploration.We designed radar data acquisition system to transmit radar based on USB(universal serial bus),because the USB interface is smaller,more convenient,and easier to develop.In addition,it has a lower cost,supports hot plug and multi-mode transmission.The transmission speed of the transmission of the USB2.0 can reach 40MB/s,it can meet the transmission need of the system.To meet the requirement of ocean monitoring,the system is designed to be eight channels.The sea echo signals received by the antennas,then through the band-pass filter into analog front-end sampled by AD.After that,DDC(digital down conversion)processing is proposed in the FPGA to obtain the baseband signal.We adopt the method of TDM(time division multiplexing)to design the DDC,and the method saves a lot of resources of the chips.At last,the data is sent to the main radar control computer through USB interface circuit.After the framework design of the whole system,we combined the practial research and analysis,we chose the EP2AGX125 chip as the FPGA main control chip,the CY7C68013A chip as the data transmission chip and so on.Based on the system structure and the chips selected for the whole system,I completed the program of the DDC and USB,then I made several simulations to test it.Then I modified the radar host for the USB equipment.At last field experimental results verified the validity and effectiveness of the system.