The Study Of Beam-forming Technology In A Digital Monopulse Tracking System

With the development of missile, Satellites, spacecraft, moderate precise tracking radar can not meet the tracking measurement requirements of weapons systems gradually. Thus precise tracking radar appears in the 1950s. The typical precise tracking radars are monopulse technology. Monopulse radars are able to provide all the lobes sensitive to angle error simultaneously, and compare each lobe's output in a single radar pulse. Therefore, are free of errors due to pulse-to-pulse fluctuations in target echo strength, which are a principal source of error in lobe switching and conical scan. Traditional monopulse radars usually is mechanical scanning radar, the complex and expensive design of monopulse feeds and heavy electrical and mechanical servo system greatly limits the application scope of monopulse radar and cost reduction.Digital monopulse tracking system appearing in recent years can effectively solve the problem that exists in the traditional analog monopulse radar, digital beam forming technique based on array antenna allows monopulse no longer is design by antenna feed justly, which is in the appropriate antenna array design,down conversion and array signal acquisition, forms digital monopulse sum-difference beam 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. Through the use of adaptive antenna, complex and expensive monopulse feed design could be avoided, and all the advantages of array antenna and array signal processing could be utilized.The paper aims at digital beam form in digital monopulse tracking system funded by Chongqing Academy Foundation, mainly in three aspects: (1) the traditional digital beam-forming algorithm is assumed in the absence of interference in the case of the target tracking, when there is the main-lobe or side-lobe interference, will affect the tracking accuracy, the paper presents a suppression technology of side-lobe interference. (2) In generally, the array antenna channel is assumed consistent when forming the sum-difference beam. But when the channel is inconsistent, and greatly reduce the performance of antenna systems, so this paper studies the influence about sum-difference beam forming when channel is inconsistent and gives the calibration algorithms. (3) for the average beam-forming algorithm, when the beam points in different directions, the beam-width will change, thereby forming the poor beam aiming. The paper gives a Steering-invariant constant beam-width beam-forming algorithm, when the beam points in different directions, the beam width is essentially same.Firstly, the paper introduces the conception, theory and mathematical model of monopulse and the array antenna; then, the structure and principle of digital monopulse tracking system is analyzed, and discussed the traditional monopulse sum-difference beam forming algorithm. Finally, three aspects of beam-forming are researched on the above mentioned, and the corresponding MATLAB simulation show the effectiveness of the algorithms.