In this article, a broadband radar cross section (RCS) reduction metasurface with a reconfigurable high-selectivity passband is proposed. Based on the equivalent circuit analysis, the feasibility of achieving the high-selective passband with multimode working state and RCS reduction near the passband through the combination of the checkerboard metasurface and the switchable bandpass frequency selective structure (FSS) is verified. The switchable FSS in the bottom layer can realize the function of wave transmittance/reflection by controlling the on/off states of the p-i-n-diodes, and a novel staggered patch structure is introduced to realize the fast conversion between different working modes without using complex feeding networks. The checkerboard metasurface in the upper layer not only realizes the RCS reduction function through scattering cancellation but also improves the passband selectivity of the switchable FSS under different working modes. Finally, a prototype of the proposed structure is fabricated and measured. The measured results show that the proposed structure can be flexibly switched between the three working modes. In different working modes, the structure has a wide RCS reduction bandwidth and a high-selective passband.

A novel design for radiation pattern-reconfigurable antenna is described in this letter. The design is based on a wideband Vivaldi antenna structure. Two different radiation patterns are achieved by switching the feeding paths to obtain two antennas operation modes, monopole mode and Vivaldi mode. The reconfigurable antenna can adjust the radiation patterns by controlling the bias voltage of pin-diodes. Therefore, by combining the two radiation patterns, a broad coverage of reconfigurable pattern is generated. In addition, the pattern reconfigurable antenna can operate at a wide frequency band from 2.7 to 12GHz. Details of the simulated and experimented results for the pattern-reconfigurable antenna are shown.

Inshore ship detection is an important research direction of synthetic aperture radar (SAR) images. Due to the effects of speckle noise, land clutters and low signal-to-noise ratio, it is still challenging to achieve effective detection of inshore ships. To solve these issues, an inshore ship detection method based on the level set method and visual saliency is proposed in this paper. First, the image is fast initialized through down-sampling. Second, saliency map is calculated by improved local contrast measure (ILCM). Third, an improved level set method based on saliency map is proposed. The saliency map has a higher signal-to-noise ratio and the local level set method can effectively segment images with intensity inhomogeneity. In this way, the improved level set method has a better segmentation result. Then, candidate targets are obtained after the adaptive threshold. Finally, discrimination is employed to get the final result of ship targets. The experiments on a number of SAR images demonstrate that the proposed method can detect ship targets with reasonable accuracy and integrity.

Phase modulation technique is of great potential for generating jamming signal in electronic countermeasures. It is still a difficulty to devise a kind of jamming signal capable of generating both false targets deception jamming and barrage jamming. Attentions must be paid to phase modulation patterns and phase values. Inspired by scatter-wave jamming and phase modulation, an active jamming technique against inverse synthetic aperture radar (ISAR) is proposed based on periodic binary phase modulation in this paper. By imposing the periodic binary phase value (0 or π) onto the intercepted radar signal, the frequency properties of radar signal are changed, which result in the corresponding changes on the target echo. Accordingly, the imaging results are reformatted comparing with the target image. Radar pulses are sampled and phase-modulated in the fast time domain as well as the slow time domain, and then the jamming pulses are retransmitted to the target. After ISAR imaging, the false target images are induced. The principle and process of phase modulation are studied in detail. Then, the imaging model of jamming signal is established and the analysis of jamming effects are carried out. The simulation results with single scattering point and real data experiments with a ship show that both deception jamming and barrage jamming can be obtained. The theoretical analysis and simulation results prove the validity of the active jamming technique.