Missile Guidance Using Missile-borne SAR

More and more importance is attached to the 2-D imaging guidance with missile-borne synthetic aperture radar (SAR), in order to enable modern weapons to obtain high precision and target selection capability in the complex environment. Missile-borne SAR, compared with air-borne and space-borne SAR, is faced with a few problems induced by its specific application and platform. The dissertation focuses on SAR imaging with non-linear aperture, imaging for swinging targets, missile geo-location, target location, SAR anti-jamming, and other key issues encountered in the application of SAR guidance.Current typical missile-borne SAR systems and the state of the art of missile-borne SAR guidance are first introduced. Then we present a few topics such as non-linear aperture SAR induced by its transversal or vertical motion components, missile geo-location based on a single prominent point and a single measurement, range-Doppler based target location, and the anti-jamming.For the non-linear aperture problem, the maneuver induced phase error the compensation condition for non-linear aperture are first analyzed, followed by the analysis of the characteristics of non-linear missile-borne SAR returns. A range-Doppler processing for missile-borne SAR maneuvering transversally and vertically, respectively, is presented with rational approximation performed, in which only a few phase factors are modified and no additional computation load is brought compared to the range-Doppler algorithm for the linear aperture.For the SAR imaging under atrocious sea conditions, the pendulum model is employed to model the echo of swinging targets. The characteristics of echo induced by the swinging are analyzed, with the conclusion that cubic phase error results mainly from the radial velocity, and is remarkable for large Doppler centroid. Thus an imaging algorithm is proposed based on fractal Fourier transform (FrFT) and cubic phase error compensation. Specifically, FrFT with sub-aperture data is performed for the detection and estimation of the Doppler rate and Doppler centroid for the scatters. In what follows, FrFT with full-aperture data is carried out and bandpass filters are designed to separate the echoes of different scatters. Cubic phase error is then compensated while the separated target is focused using its Doppler rate estimated by FrFT.For the problems of few applicable images, low dada rate, and insufficient information for location, a missile geo-location method is presented, which utilizes additional height data and a single measurement for range-Doppler of a single scatter. The close form of the missile position and the detailed location flowchart are given in the inertial launching-point coordinate frame. Simplified expressions for missile positions are derived, with the earth centered (second) equator frame as the navigation frame, when earth rotation induced effects are disregarded. Furthermore, effects of missile height measurements on the location are also quantificationally analyzed. In the end, an INS/dual-aperture-SAR combined geo-location method is presented, which requires an additional antenna. Missile geo-location precision is improved via the altitude estimation for the ground point under the missile.For the estimation of the missile-target relative position using range-Doppler information, we analyze the observability of the relative position for different trajectories, concluding that the missile must have the acceleration component not'aimming at target'to obtain the 3-D relative position of the target. Additionally, the relative position estimation methods, using two measurements and measurement series, respectively, are presented. The computation of Crammer-Rao bound gives the effects on the relative position estimation induced by the series length, the initial missile-target range, the cross-range and radial velocity of the missile, and the cross-range and radial acceleration of the missile, respectively. The estimation method is also presented with INS error into account. The observability of the aspect angles and their rates are analyzed when the missile flies a linear path with constant velocity. Finally, a new homing guidance technique is proposed which combines (Doppler Beam Sharpening) DBS guidance and monopulse tracking in the terminal course. The technique would utilize DBS's detection and recognition capabilities, and reduce the requirement for the guidance system.For the anti-jamming of SAR seekers, the techniques to anti deceptive-jamming and anti scattering-wave-jamming are presented, which employ the measurability of passive seekers for emitter parameters and the'locking on'ability of (Inertial Navigation System) INS for imaged scenes. For the handover encountered by the INS/passive radar/SAR seeker, additionally, the model for successful handover is established by quantificationally representing the required constraints for successful handover, and the method for finding handover parameters is also discussed.Finally, related work and its developing trend as well as potential applications are summarized, while problems to be resolved in further are also given in the end.