Study On Characteristics Of Chaff Jamming And Anti-Chaff Technology For Radar

Chaff is one of the most historical passive jammings, which is widely used in the fields of air-denfense, anti-ship and anti-missile. The battle performance of radar has been serously decreased by the development of chaff jamming technology and tactics. In order to adapt to complicated battle-field electromagnetic environment, radar urgently need to explore chaff jamming and radar targets'characteristics and propose new anti-chaff methods and technology. According to this, the motion and diffusion characteristics and radar scattering characteristics of chaff cloud are studied in this thesis. Based on the characteristics difference between chaff and target, new anti-chaff methods are proposed respectively for ground-based missile defense radar and radar seeker carried on anti-ship missile.The work of this thesis includes two levels:The first level is the study on characteristics of chaff jamming. Characteristics of chaff jamming include two aspects, which are the motion and diffusion characteristics and the radar scattering characteristics of chaff cloud. On the motion and diffusion characteristics of chaff cloud, the force and motion manner of single chaff and the diffusion of the whole chaff cloud are studied for dense atmosphere and rare atmosphere. The kinetic characteristics of single chaff in rare gas are derived with emphasis. The DSMC (direct simulation Monter-Carlo) method to simulate the flying of chaff cloud is proposed. Using this method a series of simulation results are gained and presented. The motion formulas of the chaff cloud's mass center and the formulas of chaffs'position distribution in rare gas are derived. On the radar scattering characteristics of chaff cloud, the chaff cloud's radar scattering models are built respectively for signals of simple pulse, narrow-band LFM signal form, wide-band LFM signal form. Then the first-order and second-order statistic characteristics of chaff cloud's radar scattering are studied. In aspect of the first-order statistic characteristics, the accurate formula of chaff cloud's average RCS is derived for uniform oriented chaff cloud, and the curves are presented for norm oriented chaff cloud, which describe chaff cloud's average RCS varying with the elevation in different polarimetric channels. It is concluded for the first time that the chaff cloud's polarimetric characteristics are independed on chaff's length, and the formula of polarimetric coviance matrix is presented. At last the second-order statistic characteristics are investigated. The chaff cloud's correlation matrix and power spectra matrix are derived based on the newest spiral descending model of chaff. The research results in this level provide the following level with theory basis, in which new anti-chaff methods are studied.In the second level, new anti-chaff methods for MD (missile defense) radar and radar seeker carried on anti-ship missile are studied. For the MD radar, the shortage of current signal process algorithm is pointed out. A new signal processing algorithm is proposed which is suitable for chaff cloud group targets. According to structure characteristcs, the detected radar targets are classified into isolated strong scattering point and continuous clutter area. Different following signal process is choosed according to target type. A measure and track algorithm is proposed for continuous clutter area. A recognization method based on the minimized polar ratio in linear polarization transform is proposed. The method can improve the recognization performance of rotation sysmetrial targets and chaff cloud. Then a new anti-chaff method using range-doppler analysis with coherent LFM pulse series is proposed. A moving compensation algorithm is proposed which can overcome the range ambulate. The range-doppler characteristics of two type chaff clouds formed in different ways are investigated. At last, it is proved through simulation that this method can improve SCR and enhance the resolve ability of radar. The detection performance of strong scattering point target in chaff cloud is improved through this method. For Radar seeker, the using manners of chaff in ship self-defense battle are introduced. The interference effect of chaff on anti-ship missile is analyzed. The polarimetric characteristics difference between chaff jamming and ship target is studied, and the statistics characteristics of chaff cloud's polar angle is derived at first time. Based on the above, an anti-chaff algorithm based on polarization reorganization is proposed for situation that chaff cloud and ship can be solved, and an anti-chaff algorithm based on polarization contrast enhancement is proposed for situation that chaff cloud and ship can't be solved. The anti-chaff performance of those algorithms is proved to be good by simulation and real data.