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.

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Bow‐tie antennas are widely used in practical ground‐penetrating radars. In spite of simple structure and wideband characteristics, boresight gain of the antenna is small and the radiation pattern is omnidirectional. In this study, a cavity‐backed bow‐tie antenna with dielectric loading is presented. The bow‐tie antenna is resistively loaded to reduce ringing effects. The resistively loaded antenna is placed within a rectangle cavity, which acts as a reflector, for unidirectional radiation and high gain. A dielectric is loaded on the antenna aperture to enlarge the operational bandwidth and stabilise the radiation patterns. Parameter studies of the dielectric substrate are performed to optimise the antenna performance. The final design is fabricated and measured. It has been shown that the antenna exhibits wide impedance bandwidth of 120% for VSWR≤2. The boresight gain is more than 5 dBi. The radiation patterns are stable and unidirectional over the whole band, and the late‐time ringing is small.

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