In this paper, a novel polarization-reconfigurable converter (PRC) is proposed based on a multilayer frequency-selective surface (MFSS). First, the MFSS is designed using the square patches and the grid lines array to determine the operational frequency and bandwidth, and then the corners of the square patches are truncated to produce the phase difference of 90° between the two orthogonal linear components for circular polarization performance. To analyze and synthesize the PRC array, the operational mechanism is described in detail. The relation of the polarization states as a function of the rotating angle of the PRC array is summarized from the principle of operation. Therefore, the results show that the linear polarization (LP) from an incident wave can be reconfigured to LP, right- and left-hand circular polarizations by rotating the free-standing converter screen. The cell periods along x- and y-directions are the same, and their total height is 6 mm. The fractional bandwidth of axial ratio (AR) less than 3 dB is more than 15% with respect to the center operating frequency of 10 GHz at normal incidence. Simultaneously, the AR characteristics of different incidence angles for oblique incidence with TE and TM polarizations show that the proposed PRC has good polarization and angle stabilities. Moreover, the general design procedure and method is presented. Finally, a circularly shaped PRC array using the proposed PRC element based on the MFSS design is fabricated and measured. The agreement between the simulated and measured results is excellent.

A novel robust watermarking scheme based on wavelet transform is presented in this paper. The watermark is embedded into significant triplet of wavelet coefficients in the three lowest detail subband images. The embedding algorithm only needs to modify a small amount of the wavelet coefficients, which leads to very small distortion and guarantees the visual quality of the watermarked image. The performance of the proposed algorithm is tested on a series of normal attacks in image processing, such as JPEG compression, Gaussian noise addition, median filter, etc. The corresponding experimental results show that the proposed watermarking scheme has better performance.