A fast analytical method for calculating the radiation pattern of solar antennas (SOLANTs) consisting of metasurface-based solar cells is proposed. The proposed method is able to analyse both uniform and non-uniform metasurfaces. In the developed method, the reciprocity theorem along with the transmission line model is used to model the layered structure used in the design of SOLANTs. To model the printed antenna, the cavity model is modified to include the loading effect of solar cells on the antenna. The proposed method is used to analyse three different SOLANTs operating at different frequency regimes, and the results are verified through comparison with full wave numerical results. The proposed model can be used for optimization purposes with the goal of achieving the best possible configurations for SOLANT structures.
Due to the wave nature of light, resolution of optical imaging systems is limited to approximately half of the wavelength. The reason behind this limitation, known as diffraction limit, is the loss of information contained in evanescent waves at the far-field region. Here, we propose a new method to retrieve the information contained in evanescent waves in far field region resulting in a novel sub-wavelength imaging technique which can go beyond the diffraction limit. We theoretically prove that using interference of waves, between the target field and reference and reconstruction waves, one can apply a shift to the angular spectrum of the target field and convert a range of evanescent waves into propagating modes. Moreover, we demonstrate how these converted waves can be distinguished in far-field from other existing modes. Unlike previously developed sub-wavelength imaging techniques, the proposed method does not require neither fluorescent materials nor complex nano-structures to realize evanescent-to-propagating wave conversion. The performance of the method is numerically investigated illustrating a resolution of one-seventh of the working wavelength, which is much beyond the diffraction limit. The proposed technique can significantly simplify sub-wavelength imaging paving the road to develop practical low cost superresolution imaging systems.
In this paper, a novel method is proposed to control and reduce the side-lobe level (SLL) of the pyramidal horn antennas. In this method, graphene sheets are deposited on the antenna walls to taper the aperture field leading to pattern engineering with the goal of the side-lobe level reduction. In essence, graphene sheet acts as a high impedance surface (HIS) and hinders electromagnetic power from reaching to the horn antenna aperture edges, in such a way that the diffraction phenomenon could be drastically diminished. The proposed design is numerically analyzed and optimized using full wave 3D simulation methods. Numerical full-wave results illustrate more than 17.6 dB reduction in the side lobe level of the proposed antenna.
Imaging subwavelength features of an object is in close relationship with extracting information included in evanescent waves scattered from the object. These evanescent waves decay exponentially with distance, therefore, they can not be captured at far-field, resulting in a resolution limited image of the object. Here, we propose a far field imaging technique based on gradiant metasurfaces, with ability to provide an image of subwavelength features. In this technique, gradient metasurfaces are used to convert evanescent waves scattered by subwavelength features into propagating waves resulting in a resolution beyond the diffraction limit. The performance of the proposed imaging technique is evaluated using full wave numerical analysis and the results validate its capability for imaging beyond the diffraction limit.