FPGA Implementation Of Digital Monopulse Tracking Technology

With the development of missile, rocket, statellite and astronavigation technology, the more excellent performance is demand on speed, accuracy, range and anti-interference ability of tracking radar. The conical scanning antenna system using sequential comparison lobing can not to be able to satisfy the request of tracking hyper-velocity vehicle. But the monopulse tracking uses simultaneously comparison lobbing, Namely the monopulse antenna simultaneously produces several beam, with several independent receiving branches which accept these beam from the single echo signal of goal reflection, then comparing these echo signal gains the angle error signal of goal. Because of using simultaneously comparison lobbing, gaining error signal is rapid, the tracking speed is quick; the error signal only relates with the relative value of several beam echo pulse scope which has been received, it does not have fluctuation disturbance of the target, so, the precision of angle tracking is high, and the anti-interference ability is also strong; moreover, the sum beam which gained the distance information of object radiates strongest in the antenna axial at the same time, the range of radar is also far. Therefore, at present the monopulse tracking already gradually substitutes for the conical scanning tracking, obtaining widespread application.Monopulse technology is a technology developed on the basis of scanning and beam-switching technology, for sophisticated radar tracking, the accuracy of monopulse tracking system may reach 0.1 mil, at present there is not one kind of tracking technology whose tracking accuracy can surpass monopulse. But the traditional monopulse technology has many shortcomings, for example: multi-targets can not be tracked, it has expensive complex electrical and mechanical servo system, the development of hardware and production are difficult, the volume and weight power loss are big, maintaining is complicated and so on. Address these shortcomings, it puts forward a multi-targets tracking method and system for monopulse based on the antenna array and data processing in the article. That is the digital monopulse tracking system. It forms"digital monopulse sum-difference beam"(digital monopulse is called for short in the following) using digital processing method in baseband, producing the error information of angle. It moves the beam according to the error information of angle by changing the scaling coefficient of monopulse, tracking multi-targets. Firstly, the elementary theory of array antenna and the commonly used mathematical model of antenna array are introduced in this paper; next, the basic principle of digital beamforming is elaborated; then, the principle of monopulse tracking is analyzed; and the commonly used sum-difference monopulse for amplitude is discussed, the structure of a digital monopulse system is designed; finally, this paper analyzes the basic principle of the digital beamforming technology and monopulse tracking based on uniform circular array. As a result of complex arithmetic contained in the algorithm, it is not suitable for implementation in FPGA, so the author analyzes the principle of the CORDIC algorithm, then puts forward a new FPGA implementation of digital monopulse tracking technology basing on CORDIC and designs some algorithm program used in the paper by VHDL, giving the circuit diagram designed and the simulation result by using Modelsim software is also carried out. The simulation proves that this method is correct.