Research On The Key Techniques Of Digital Monopulse Under Limited Constraints

Monopulse radars are often used as precise tracing radars for their free of errors, the pulse-to-pulse fluctuations in target echo strength could be ignored, as the fluctuations have no effect on the ratios of signals received simultaneously from different lobes on each pulse. Traditional monopulse radars transmite and receive beams by horn feeds, such as four-horn feed. Precise tracing could be achived by adjusting mechanical shaft based on the error voltage got by comparing the sum and difference beams, that is the monopulse radio curve. Digital monopulse radar based on array antenna and digital beamforming could effectively solve the problem that exists in the traditional analog monopulse radar, such as the complex and expensive design of monopulse feeds and heavy electrical and mechanical servo system, and also could achieve precise tracing.Based on array antenna beamforming technology, this paper aims at research on some key techniques on precise tracing of digital monopulse radar under certain constraints, mainly in three aspects:①Research on monopulse radar under sidelobe level constraint. Studies on the changes of monopulse beams and monopulse radio of liner array with Chebychev, Taylor, Bayliss and uniform distributions are showed that it’s reasonable for the sum beam with distributions of Chebychev and Taylor, and difference beams of Bayliss distribution, and the monopulse radio curves of that four distributions normalized by 3d B bandwidth of each sum beam are almost same.②A algorithm of constant beamwidth beam pattern with steering-invariance was proposed ensuring exact pointing. The bandwidth of sum and difference beams would be wider as steering away from normal direction,which would cause certain errors between the goal direction and the real test direction when comparing the beams from different direction. Two methods base on Genetic Algorithm are composed to constraint constant beamwidth when steering different directions, one is constraining sum and difference beams generated by digital beamforming respectively, another is achieving sum and difference beams by constraining two original beams. The simulation shows that these two methods could keep constant beamwidth with steering-invariance as well as exactly pointing.③Research on digital monopulse radar tracing system with directional antennas as array elements. The half-wave dipole antenna and the pattern of cosine shape are choosed as directional array element. Sum and difference beams and monopulse radio curve are studied under conditions of directional array with and without white Gaussian noise. The research gives certain evaluation of monopulse radio curve error rate related to signal-to-noise ratio and scan angle.