| In this paper ,we mainly study on the radar digital image transmission technology.In 1925,radar acted as a research tool to detect height of ionospheric. Since then,radar has 80 years history.In this 80 years,many breakthroughs of radar technology have been made in both theory and application. Their applications extended from enemy aircraft early-warning system during World War II to space measurement, weather detection, synthetic aperture imaging, and many other aspects. It is the most need of user what the radar can "see" (radar video images). But sometimes we were hedged in with environment conditions and any other reasons (such as aerial radar or unmanned radar, etc.).After the radar got images, we need some way to transmit them to the user of long-distance. The main purpose of this task is to design a radar image transmission control systems, which can transmit video images of radar real-time, highly efficient, without distortion. It range from getparms point of radar video images to user point, and play a role of "video transmission bridge".In the design of the radar image transmission system, digital video compression system and the choice of means of communication are two key elements. We have analyzed large number of active-duty equipments and accessed to relevant information and documents.After studying, comparison and screening, we have proposed a radar digital image transmission technology which combinate radar video images compression based on wavelet transform and spread spectrum communications. In data compression, we decomposited the radar digital video signal by two-dimensional orthogonal wavelet transform (orthogonal mirror filters), then we used run-length code and Huffman code to compress the date. Run-length code is the role of the various terms of the adjacent block, the number of units to enhance the efficiency of Huffman code. Huffman code is the variable length of the fixed Huffman table look-up table encoder. In communications, because of the spread spectrum system giving full play in the anti-interference, confidentiality and CDMA, we chose the spread spectrum communication system, which meet the requirements of the radar image transmission. In engineering, we use a dedicated wavelet transform DSP hardware in data compression and use a mature market shelf products in communications. After some tests, the system can transmit digital video images of radar without distortion. With full-duplex, high reliability, high universality, anti-interference capability and good extendibility, the system can transmit not only duplex image signals of radar, but also Multi-channel voice and data information. So it meet the design requirements.With the continuous development of radar technology, the demand of video images of radar will be more and more. The design has better prospects, for its universality. |
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