The Project Realization Of Altimetry For A VHF Radar Based On Data Flow Mode

With its anti-stealth, over horizon detection, anti-radiation missiles and other characterristics, VHF radar had got increasing notice in much of the world’s major military country in modern war. Limited by its wavelength and wide beam, its altimetry accuracy is relatively low, and its detection of low elevation target is seriously affected by multipath signals.In this paper, combined with a VHF digital array radar, the implementation of altimetry for VHF radar in data flow model is studied, specific work is summarized as follows:Firstly, the echo signal model and the basic principle of several common VHF radar altimetry algorithm is introduced, Combined with the actual project needs, the performance of algorithms with different SNR and different target elevation is simulated to obtain its stability and estimation accuracy.Then, a altimetry program is designed based on one communication digital signal processing board. The hardware structure of the processing board is introduced at first, then one FPGA and eight DSPs of it is allocated based on actual functional requirements. FPGA is responsible for the communication interface between and within the board, the altimeter computing functions is mainly completed by DSP, data transmission in the board is completed by the chain junction, The communication is controlled by the IRQ interrupts and FLAG signal collaboration. To improve the data processing capability, the data stream mode is used for the data transmission and processing in the signal processor, eight DSPs is divided into two treatment groups, two elevation area is treated as a processing cycle, the pulse data is received in the fires area,and the receiving of the test results, the completing of altimetry and the sent of altimetry results is in the second area. with the analysis of the measured data, the altimeter algorithm program for this board is designed, combining rough estimation and refined estimate, progressing a variety of algorithms partly. based on DBF rough estimate, the appropriate method is selected according to coarse estimates to ensure that a high measurement precision is completed with less time, raising the radar altimetry processing capabilities effectively.Finally, the methods and procedures of DSP program in data flow pattern for a VHF radar is introduced. DSP program is broadly divided into initialization, interrupt handling, take-over and storage of received data, aggregation of point trace, altimeter and data transmission, its graft, maintenance and testing is benefited from program modular. By using mixed C and assembly language, the code efficiency and DSP resources utilization are improved. Data transfer associated with DSP is carried by DMA method to achieve a parallel processing of data transformation and a core operation, improving the ability of the DSP to process the target. It is focused on the protection and control of DSP programs under data flow model, for its high flexibility and non-timing characteristics, the stability of the whole program is increased by nesting of data, and different types of DMA channels working simultaneously greatly enhances data transmission efficiency in data flow mode. At last, the terminal of a VHF radar displays the altimeter treatment effect.