The Study On Airborne Bistatic Radar Clutter Simulation And Cancellation Techniques

Bistatic clutter cancellation and ground moving target detection are key technologies for the signal processing of airborne bistatic radar. Unlike clutter echoes for sidelooking airborne monostatic radar, bistatic clutter echoes are range dependent, which greatly degrades the STAP (space-time adaptive processing) performance for bistatic clutter suppression. Therefore, it is necessary to find some compensation methods for mitigating the bistatic clutter range dependency or design bistatic STAP algorithms less sensitive to range dependency.This thesis is focused on the researches of clutter modeling and clutter suppression technologies for airborne bistatic radar, and the main contributions are:At first, a new coordinate system conversion approach is initiated into formulating bistatic geometrical model. The method sets up a generalized geometrical model for any bistatic scenarios, and exactly discloses the temporal and spatial correlation properties of bistatic clutter tied up with specific airborne bistatic radar scenario.Secondly, the SIRP (Spherically Invariant Random Process) method is introduced to establish the accurate statistical and power spectral model for bistatic clutter. Unlike the ZNML (Zero Memory Nonlinearity) method, this technology can separately control amplitude distribution and power spectrum for bistatic clutter. Therefore, it is suitable for describing the complicated space-time correlation nature of bistatic clutter, and can be used to the non-Gaussian bistatic clutter simulation.Thirdly, for mitigating the adverse effects of the clutter range dependency on bistatic STAP, the Nonlinear Time-varying Weighting (NTW) method is proposed. The approach can adaptively trace the nonlinear variations of bistatic clutter characteristics over range, and unlike the traditional Doppler Warping (DW) method and the angle-Doppler compensation (ADC) method, it does not demand the prior angle and Doppler knowledge about clutter spectral center.Fourthly, the reduced-Dimension STAP based on Joint-Domain Localized (JDL) algorithm is studied for bistatic clutter cancellation, and a modified JDL algorithm is proposed, which transfers the space-time data to the angle-Doppler domain by using a transform matrix. The method does not require the uniformed linear array (ULA) with the isotropic, point sensors which are indispensable for the JDL algorithm based on two-dimensional discrete Fourier transform (2D-DFT).Finally, a space-time adaptive bistatic clutter cancellation system is designed, which confirms the bistatic clutter suppression performance of the previously proposed JDL-STAP algorithm. The experimental results meet the expected requirement and show the advantage of the JDL for bistatic clutter cancellation in the nonstationary clutter environment.