Study On The Theories And Methods Of Low Altitude Target Detection For Radar Seeker

Detection of low altitude targets for the radar seeker is a popular issue for the air defense missile and anti-ship missile. The clutter, multipath scattering and deliberate interference affect the radar seeker detection of low altitude targets simultaneously. Therefore, studying the radar seeker detection methods for the low altitude targets provides significant reference for the precision striking of air defense missile and anti-ship missile. Aiming at enhancing the radar seeker detection performance for the low altitude target, this thesis investigates correlated issues on radar seeker detection of low altitude targets which comprise study on characteristics of the environments faced by the radar seeker when it detecting the low altitude targets, analysis of the radar seeker detection performance for low altitude targets, study on radar seeker detection methods for low altitude targets, and study on the anti chaff centroid jamming methods for the radar seeker.In Chapter 1, the background and significance of this thesis is introduced, and the present situations of four aspects at home and abroad are summarized, where the four aspects comprise environmental characteristics analysis of the radar seeker detecting low altitude targets, performance analysis of the radar seeker detecting low altitude targets, techniques of radar detection in clutter, and anti chaff centroid jamming techqiues for the radar seeker respectively. Based on these, the main work of this thesis is illustrated.Characteristics of the environment faced by the radar seeker when detecting low altitude targets are investigated in Chapter 2. By utilizing the experimental data, amplitude distribution, temporal and spatial correlations of the sea clutter for the radar operating at low grazing angles are analyzed at first. Then merits and drawbacks of three types of clutter modeling methods are summarized, where the clutter modeling methods comprise zero memory nonlinear transformation method, spherically invariant random process method and range cell division method. Based on this, a spatial-temporal correlated K distributed clutter modeling method for coherent radar seeker is proposed by taking the radar seeker operating circumstance into account. In addition, multipath scattering characteristics of the radar seeker detecting low altitude targets are analyzed, and the specular and diffuse reflections are modeled in this Chapter.In Chapter 3, radar seeker detection performance for low altitude targets are analyzed. With the classical detection theory of the radar seeker, detection performances of radar seeker in the backgrounds of K distributed clutter, specular reflection and dense multiple false targets jamming are first analyzed respectively. Furthermore, detection performance of the radar seeker in clutter and multipath environment is further analyzed theoretically. The theorectical analsis results are verified by simulation. Analysis results show that multipath is beneficial to radar seeker detection of low altitude small targets, and clutter is the key influence factor for the radar seeker detection of low altitude small targets.Considering the clutter faced by the radar seeker when detecting low altitude targets, detection methods of radar seeker in clutter are studied in Chapter 4. Based on the idea of clutter suppression, radar seeker target detection based on orthogonal projection is proposed. And experimental results utilizing the measured clutter data demonstrate the validity of the proposed method. At the same time, based on the idea of optimal detector design, a radar seeker detector which is suitable to use in K distributed clutter is designed. In addition, with respect to polarimetric detection, the detection performances and engineering implementation difficulties of optimal polarimetric detector, polarimetric whitening filter, optimal span detector, polarimetric matched filter, power maximization synthesis detector and single channel detector are analyzed and compared respectively. Analysis and comparison results illustrate polarimetric whitening filter is the most suitable detector to use in engineering.In Chapter 5, anti chaff centroid jamming method for radar seeker is studied. The tactical use method of chaff centroid jamming is introduced at first. Then effect of chaff centroid jamming on radar seeker angle measurement performance is analyzed. Considering the jamming should be detected at first when countering chaff centroid jamming, detection of chaff centroid jamming aided by GPS/INS is proposed in this Chapter. Then, anti chaff centroid jamming method based on oblique projection is proposed. And the validity of the methods is verified by simulations.At last, Chapter 6 concludes the main work and innovations of this thesis, and points out the issues needs to be further investigated in future.