AbstractThis research involves a compact wideband circularly-polarized antenna array, which consists of a sequential rotating phase feed network, 2 × 2 mushroom-type metamaterial (MTM) unit, and so on. Each antenna array unit contains a microstrip feedline, an L-shaped slot antenna, and so on. The MTM-based antennas were incorporated with a sequential-phase network of sequentially rotated series-parallel feed to achieve wideband operation. The operational bandwidth and the radiation model in the high-frequency area were improved through the adjustment of spacing between the L-shaped slots while maintaining the size and structure of the MTM. The proposed design had dimensions of 80 mm × 80 mm × 3.5 mm (~1.64 λ0 × 1.64 λ0 × 0.072 λ0 at 6.15 GHz), and it was simulated, fabricated, and tested.
In this article, an orbital angular momentum (OAM) patch array antenna with converged beam is proposed. The electromagnetic band gap (EBG) structure is applied to a patch array antenna with 2 Â 2 elements. The array antenna is excited by a carefully designed feeding phase shift network with equal output energy for four output ports. Thus, the OAM vortex wave with topological charge l = 1 is generated. By using EBG structure around the radiating patches, the surface wave of the array antenna is suppressed. As a result, the radiation pattern is improved significantly, including the enhanced gain and reduced divergence angle. A prototype was fabricated and measured. The measurement results agree well with the simulations. Compared with the other approaches, the proposed antenna is much more compact in structure and ease of fabrication.
In recent years, metasurfaces have been widely employed in stealth technology, which brings great challenges for radar target detection. In order to address this issue, a novel detection approach for metasurface-stealth-target (MST) based on orbital angular momentum (OAM) vortex wave is proposed in this paper. Compared to a conventional plane wave detection system, the transmitting wave of the proposed approach is OAM-modulated, of which the wavefront is helical along the beam axis. Thus, the differentiated exciting source is introduced to different parts of MST. According to the established scattering model and full-wave simulation, the echo of MST has a strong correlation with OAM order l, which exhibits quite different scattering characteristics from the plane wave illumination. A chessboard metasurface (CM) is taken as an example to be irradiated by an OAM vortex wave of l=±2. The backscattering is significantly boosted compared to plane-wave detection, which is against the stealth ability of CM. This phenomenon is also verified by experiments. The results reveal that OAM detection is a promising approach for MST detection..
In this paper, an orbital angular momentum (OAM) metasurface antenna is proposed. Based on the idea of controlling the radiation and scattering simultaneously, the metasurface unit cells play two roles of radiating and scattering energy. For radiation, the metasurface unit cells are excited by two carefully designed phase shift networks (PSNs) at two orthogonal directions. Thus, OAM vortex waves with topological charge l = ±1 are generated at 7.48 GHz band. For scattering, the incident wave is deflected through the phase canceling scheme due to the anisotropy property of the metasurface unit cells. As a result, the in‐band radar cross section is reduced. A prototype of the antenna was fabricated and measured. The measurement results agreed well with the simulations.
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