Electromagnetic backscattering from one-dimensional drifting fractal sea surface Ⅱ：Electromagnetic backscattering model

Sea surface current has a significant influence on electromagnetic（EM） backscattering signals and may constitute a dominant synthetic aperture radar（SAR） imaging mechanism. An effective EM backscattering model for a one-dimensional drifting fractal sea surface is presented in this paper. This model is used to simulate EM backscattering signals from the drifting sea surface. Numerical results show that ocean currents have a significant influence on EM backscattering signals from the sea surface. The normalized radar cross section（NRCS） discrepancies between the model for a coupled wavecurrent fractal sea surface and the model for an uncoupled fractal sea surface increase with the increase of incidence angle,as well as with increasing ocean currents. Ocean currents that are parallel to the direction of the wave can weaken the EM backscattering signal intensity, while the EM backscattering signal is intensified by ocean currents propagating oppositely to the wave direction. The model presented in this paper can be used to study the SAR imaging mechanism for a drifting sea surface.

Effective path planning method for low detectable aircraft

To utilizing the characteristic of radar cross section （RCS） of the low detectable aircraft, a special path planning algorithm to eluding radars by the variable RCS is presented. The algorithm first gives the RCS changing model of low detectable aircraft, then establishes a threat model of a ground-based air defense system according to the relations between RCS and the radar range coverage. By the new cost functions of the flight path, which consider both factors of the survival probability and the distance of total route, this path planning method is simulated based on the Dijkstra algorithm, and the planned route meets the flight capacity constraints. Simulation results show that using the effective path planning algorithm, the low detectable aircraft can give full play to its own advantage of stealth to achieve the purpose of silent penetration.

Composite wave-absorbing structure combining thin plasma and metasurface

In order to solve the thickness dependence of plasma absorption of electromagnetic waves and further reduce the backward radar scattering cross section(RCS)of the target,we designed a novel composite structure of a metasurface and plasma.A metasurface with three absorption peaks is designed by means of an equivalent circuit based on an electromagnetic resonance type metamaterial absorber.The reflection and absorption of the composite structure are numerically and experimentally verified.The finite integration method was used to simulate a composite structure of finite size to obtain the RCS.The experimental measurements of electromagnetic wave reflection were conducted by a vector network analyzer(Keysight N5234A)and horn antennas,etc.The research showed that the absorption capacity of this composite structure was substantially improved compared to either the plasma or the metasurface,and it is more convenient for application due to its low plasma thickness requirement and easy fabrication.