In this letter, we propose an inverse synthetic aperture radar (ISAR) imaging method using time-domain (TD) scattering echo simulated by time-domain physical optics (TDPO) method. First, the TD pulse plane wave is taken as the incident wave and the transient scattering echo data matrix is obtained by using the TDPO method under different look angles of the target. Then, demodulation, pulse compression, and azimuth inverse fast Fourier transform (FFT) are performed on the echo data matrix to obtain the ISAR image under small bandwidth small angle. In this letter, considering the fact of TD pulse signals emitted by radar, electromagnetic scattering modeling method is adopted to obtain more accurate TD scattering echoes. This method combines the electromagnetic scattering algorithm and radar imaging algorithm effectively and is closer to practical application. Finally, ISAR images are given to verify the feasibility and fidelity of the presented method.

An efficient time domain shooting and bouncing ray (TDSBR) method is proposed to analyze the transient near-field scattering from an electrically large complex object illuminated by a far-field antenna source. The time-domain far-field incident sources can be derived by a convolution of pulsed excitation with the inverse Fourier transform of frequency domain (FD) far-fields radiated from an antenna. In order to obtain accurate near-field scattering results, time domain physical optics (TDPO) near-field integral representations are proposed and reduced to closed-form expressions to improve computing efficiency by applying locally expanded Green function approximation. Different from the plane wave incident situation, in the case of antenna radiation, the incident fields of each individual facet in the ray path are represented by the radiation fields from the equivalent mirror antenna derived in this paper. Since the radiation fields naturally contains the time delay term, the complicated processing of the time delay problem can be avoided by solving the equivalent mirror antenna radiation fields. It is simpler and more accurate than the traditional time domain geometrical optics (TDGO) method. Numerical examples are presented to demonstrate the efficiency and accuracy of the proposed method.

This letter focuses on scattering from rough sea surface covered by insoluble oil. Oil film damps the capillary wave of the rough sea surface, which leads to a smooth profile of the contaminated sea. We investigate this phenomenon using a highly efficient iterative model based on physical optics (PO) and Huygens' equivalence principle. PO is used to calculate the scattering from the oil film and underlying rough sea surface. The Huygens equivalence principle and iterative strategy are employed to evaluate the coupled scattering between the oil film and rough sea surface. The scattering of contaminated rough sea surface based on the iterative model is compared with those using the method of moments as well as computational time and memory requirements. Then, the influence of some important parameters, such as wind speed, oil thickness, incident wave frequency, and oil coverage, on scattering is investigated and discussed in detail.

In the past, most of the transient electromagnetic (EM) analysis focused on the scattering from target. The transient scattering from rough surface was rarely studied, especially for the layered rough surface. When the target is above the rough surface, it needs to solve the composite transient scattering from the rough surface and the target above it. In this paper, we mainly focus on the time-domain (TD) analysis for transient scattering from target and layered rough surface based on time-domain ray tracing (TDRT) modeling. Applying geometrical optics (GO), the multiple bounces of the transient EM waves between layered rough surfaces and target are traced to obtain the incident field of the irradiated surfaces. Then considering the particularity of the layered rough surface, we modify TD Gordon integral and reduce the TD physical optics (TDPO) integral to closed-form expressions to improve computing efficiency. To demonstrate the efficiency and accuracy of the proposed algorithm, the transient scattering simulations of composite model involving target and layered rough surface are compared to frequency-domain ray tracing (FDRT) with IFFT, as well as the results obtained by the multilevel fast multipole algorithm (MLFMA) of FEKO in conjunction with IFFT (IFFT-MLFMA). The characteristics of transient scattering from the composite model are further studied to show the physical phenomenon of scattering mechanisms. Specifically, the transient scattering from the composite model for different parameters are simulated for a sensitivity investigation of the transient scattering to variations in the related parameters.

This study proposes and validates a new physical optics–physical optics (PO–PO) method based on the reciprocity theorem to calculate the electromagnetic backscattering from a two‐dimensional (2D) dielectric‐coated conducting target located above a 1D dielectric randomly rough surface. To avoid the artificial reflection from two endpoints of rough surface, the tapered plane wave proposed by Thorsos in 1988 is introduced as the incident wave. The results obtained from the author's method, for horizontal polarisation, show a good agreement with the numerical results derived from the conventional method of moments in a special case of a perfectly electric conducting target located above a dielectric rough surface. Finally, the influence of some parameters related to the coating material on the composite scattering is investigated and discussed in detail.

We propose an inverse synthetic aperture radar (ISAR) imaging algorithm for a composite target-ocean scene based on time-domain shooting and bouncing rays (TDSBR) method. To do this, we develop the TDSBR method to simulate the electromagnetic scattering echoes from a composite target-ocean scene. Then, we derive the ISAR imaging formulas based on electromagnetic scattering field expressions. The demodulation, pulse compression, and azimuth inverse fast Fourier transform are performed on the scattering echo data to obtain ISAR images. Linear frequency modulation (LFM) pulses are usually used in traditional radar imaging. However, its long pulse width leads to more computation time for simulations. To increase efficiency, we replace LFM pulses with modulating Gaussian pulses. As a result, we modify the matched filter to achieve pulse compression under modulating Gaussian pulse excitations. Simulation results confirm that this proposed method improves efficiency while ensuring image quality. This proposed technique fully incorporates the electromagnetic scattering mechanism and is accurate. It effectively combines the electromagnetic scattering algorithm and the radar imaging algorithm. Finally, we present ISAR images simulated by this method. These results confirm the feasibility and efficiency of this technique.