In this paper, a hybrid method of physical optics (PO) shooting and bouncing ray (SBR) physical theory of diffraction (PTD), is adopted to investigate the composite scattering of a vehicle target on the ground. Where the scattering of ground is calculated by the PO method, the scattering of the vehicle target is computed by the SBR-PTD method, and the mutual couplings between them are solved by the ray tracing technique. In addition, an octree data structure is used to accelerate the ray tracing progress. A forward-backward ray tracing technique is employed to ensure the accuracy of the illuminated facet identification. In numerical simulation, the monostatic and bistatic scattering of a reduced-scale vehicle target are calculated by the SBR-PTD method and compared with the simulation results with the multilevel fast multipole method (MLFMM) in commercial software FEKO. And the composite scattering from a reduced-scale vehicle target on the planar ground by our PO-SBR-PTD method is also compared with the MLFMM. The results show that our methods can greatly reduce the computational time and memory requirement while keeping a satisfactory accuracy. Finally, the composite scattering from the vehicle target on the rough ground is demonstrated and analyzed for different incident parameters.

A bi-iterative physical optics (PO) method is presented in this letter to investigate the composite scattering from a perfectly electric conducting object partially buried in the dielectric rough sea surface. In the present method, both the scatterings of a partially buried object and the underlying sea surface are calculated by the PO method. And a bi-iterative strategy is considered, including the mutual interaction among points on the object in direct scattering and the mutual interaction between the object and the sea surface in coupling scattering. In addition, the coupling interaction between the partially buried object and the sea surface contains two parts: 1) the upper surface of the sea surface and the upper part of the object and 2) the lower surface of sea surface and the lower part of the object. In numerical simulations, the bistatic normalized radar cross sections of the composite model are computed by the bi-iterative PO method and are compared with those by the conventional method of moments for different object types and polarizations. The results show that the proposed method has a good accuracy and can greatly reduce the computational time and memory requirement.

The compressive sensing (CS) is a new sampling paradigm that promises to accurately reconstruct compressible signals from much fewer measurements than nominal number of data points. To applying the attractive properties illustrated above, a new method named CS-FEKO is proposed in this paper, which introduces the ideas from CS into commercial software field computations involving bodies of arbitrary shape (FEKO) to improve the efficiency of FEKO in solving multi-static scattering problems. In performing a multi-static scattering analysis with CS-FEKO, the far zone scattered fields in one scattering angle over all excitations are viewed as the signal of interest. The CS is firstly utilized as a pre-processing of FEKO, which modifies the conventional plane incident waves to the excitations that the CS needed. Then FEKO is applied to solve the scattering problems under the new set of excitations to get the measurements of the scattered fields. Finally, the CS is secondly introduced as a post-processing of FEKO, where CS inversion is employed to recover the desired far zone multi-static scattered fields. To make a full use of the high efficiency and the deeply optimization benefits of FEKO in solving wide-angle scattering problems, two forms of measurement matrix are introduced, which has a more concise expression, and can reduce the simulating runtimes dramatically. The multi-static scattering radar cross section (RCS) for different objects obtained from CS-FEKO are presented and compared with those derived from FEKO to illustrate the accuracy and efficiency of the proposed method.

The hybrid method of Shooting and Bouncing Ray (SBR) and Two Scale Model (TSM) based on the facets model (i.e., SBR-TSM) is proposed in the published literature to efficiently calculate the composite electromagnetic (EM) scattering from the electrically large sea surface with a target. However, the mesh size of sea surface is about 20 times the Bragg wavelength when the TSM method are employed to compute sea surface scattering, while the size of target facets is relatively smaller, especially for those with curved surfaces or fine structures. Thus, the excessive difference in facet size between the target and sea surface can easily lead to a decrease in the accuracy of determining the illuminated area during ray tracing (i.e., an increase in ray tracing error) in SBR-TSM method. To solve this problem, the hybrid method of the Two-scale Subdivision SBR (TSBR) and the TSM, named TSBR-TSM, is proposed in this paper. Comparative simulations are performed between the TSBR-TSM, the SBR-TSM algorithm, and the Multilevel Fast Multipole Method (MLFMM). The results show that TSBR-TSM method performed better in computational accuracy while ensuring computational efficiency, making it a promising advance in composite scattering modeling.

In this paper, a weighted arctangent function is used in conjunction with the spectral method to generate a land–sea junction composite rough surface under the spatially homogeneous and time-stationary hypotheses. The exponential correlation function and the Joint North Sea Wave Project (JONSWAP) spectrum, combined with an experiment-verified shoaling coefficient, are applied to model the land surfaces and the time-varying sea surfaces separately. The second-order small slope approximation (SSA-II) with tapered wave incidence is utilized for evaluating the electromagnetic scattering characteristics and Doppler characteristics of the generated composite rough surface. The influence of land–sea interface factors on radar cross-section (RCS) and Doppler shift of radar echoes is investigated in detail by comparing the RCS and Doppler spectra of the land–sea junction composite rough surfaces with those of finite-depth sea surfaces. It can be found that the Doppler spectra of the land–sea junction composite rough surface is narrower than that of the finite-depth sea surface under upwind directions and wider than that of the finite-depth sea surface under crosswind directions.