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A novel integration strategy of microstrip antenna and metasurface is proposed to achieve low-radar cross section (RCS) and improved radiation performance simultaneously. Aimed at the applications in stealth cylindrical carrier, the antenna has a circular configuration, and the metasurface cells are closely arranged around the radiation patch in a concentric ring-type manner. Moreover, the mode analysis method is fully used to analyze the antenna’s working mechanism and guide the optimization process. Owing to the addition of metallic vias, the original quasi-TM30 mode is altered to three series-TM10 modes and thus enhanced gain is achieved. Interestingly, the addition of vias also generates a new resonance which widen the antenna’s impedance bandwidth. In another aspect, both in-band and out-of-band RCS reductions are obtained simultaneously. Finally, two prototypes are fabricated to validate the proposed design strategy. Good agreements between measurements and simulations are obtained. Measured results show that the gain of the proposed antenna is at least 3 dB higher than the conventional antenna in the entire operating band, and obvious RCS reduction is achieved from 4.0 to 8.5 GHz concurrently. [ABSTRACT FROM AUTHOR]

Radar cross section (RCS) reduction in the working band of antennas, likely leading to radiation performance change or deterioration, is quite difficult for both antenna elements and arrays. Aimed at this problem, this article presents a novel design strategy of microstrip patch antennas with low in-band RCS. This strategy combines metasurface with antenna from the perspectives of both structure and electrical performance. To be specific, anisotropic metasurface is proposed to replace the conventional patch and behave as the radiating structure of the antenna directly, which does not increase the original antenna size. Through proper connection of the metasurface units, the novel antenna has the same radiation performance with conventional microstrip antenna but low in-band RCS for any polarized incidence. The radiation and scattering mechanism of the novel antenna is carefully elaborated, from which a frequency reconfigurable antenna is also derived by loading varactors. Furthermore, different design strategies of low in-band-RCS antenna element and array are clarified. On the basis of which, a $4 \times 4$ array is developed to achieve in-band-RCS reduction with radiation performance kept. Both numerical and experimental results are demonstrated, and the reasonably good agreements verify the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

An electronically reconfigurable reflectarray antenna (RRA) with 10\times10 elements is presented with a detailed design procedure for an improved beam-scanning performance. The element, designed at Ku band using a simple patch structure with one PIN diode and two substrate layers, can be electronically controlled to generate two states with 180° phase difference and low reflection loss. A reflectarray prototype is fabricated and experimentally studied for proof of principle. The limitations of the small aperture size are analyzed in detail, and synthetic optimizations of both feed location and aperture phase distribution are used to improve the beam-scanning performance of the prototype. Experimental results agree well with the full-wave simulations, and scan beams within {\pm}{50}^\circ range are obtained with a maximum aperture efficiency of 17.9% at 12.5 GHz. Consistent scan beams are obtained from 11.75 to 13.25 GHz. Furthermore, the versatile beam-forming capability of the RRA is also demonstrated by a wide-beam pattern synthesis. A fast beam-switching time (12\;\upmu \text{s}$) is theoretically analyzed and verified by the measurement. [ABSTRACT FROM PUBLISHER]

An ultrawide-angle frequency beam scanning leaky-wave antenna (LWA) with a high scanning rate based on spoof surface plasmon polaritons (SSPPs) waveguide is proposed in this communication. A row of elliptical patches is placed periodically near the SSPPs waveguide, which can shift the fundamental mode of SSPPs waveguide to the fast-wave region and radiate electromagnetic (EM) waves. The simulated results show that the proposed LWA achieves an ultrawide scanning angle range of 172° over a narrow operation bandwidth of 9.8–12.28 GHz, which implies a high scanning rate. The simulated average gain of the proposed LWA is 10.13 dBi and its average total efficiency is 75.35%. The proposed LWA is fabricated and measured. The measured scanning angle range is 167° in the frequency band of 9.9–12.25 GHz, and the measured average gain is 9.73 dBi. Good agreements between the simulated and measured results are obtained, validating the proposed design. [ABSTRACT FROM AUTHOR]

Metasurfaces trigger great interests due to their potential ability to manipulate the propagation of electromagnetic (EM) waves. Plenty of fascinating EM phenomena have been generated using metasurface. However, two defects are hindering their development. The first one is that most metasurfaces only perform a specific functionality once designed, which means they do not possess tunable properties. The second defect is that most of them work in either reflection mode or transmission mode, leaving half of the EM space completely unexplored. Therefore, it is challenging to design metasurface with tunability and entire-space working modes simultaneously. Here, a tunable metasuface is presented to solve these problems. The proposed metasurface element is a multilayer structure which can manipulate EM waves in the entire space. Concurrently, p-i-n switches are loaded on each element which can dynamically control transmission and reflection phases. Thus, some intriguing EM modulation functions in the entire space are realized, such as beam forming, anomalous reflection, and diffusion. The simulated and experimental results prove the tunable metasurface. The proposed metasurface offers a feasible strategy to design tunable metadevices and for other related practical applications. [ABSTRACT FROM AUTHOR]

The simultaneous improvement in radiation and scattering performance of an antenna is normally considered as contradictory. In this paper, wideband gain enhancement and radar cross section (RCS) reduction of Fabry–Perot (FP) resonator antenna are both achieved by using chessboard arranged metamaterial superstrate (CAMS). The CAMS is formed by two kinds of frequency-selective surfaces. The upper surface of CAMS is designed to reduce RCS based on the phase cancellation principle, and the bottom surface is used to enhance antenna gain on the basis of FP resonator cavity theory. Both simulation and measured results indicate that compared with primary antenna, the gain of the proposed FP resonator antenna is enhanced by 4.9 dB at 10.8 GHz and the 3 dB gain bandwidth is from 9.4 to 11.1 GHz (16.58%). Meanwhile, the RCS of the proposed FP resonator antenna is reduced from 8 to 18 GHz, with peak reduction of 39.4 dB. The 10 dB RCS reduction is obtained almost from 9.6 to 16.9 GHz (55.09%) for arbitrary polarizations. Moreover, the in-band RCS is greatly reduced, owing to the combined effect of CAMS and FP resonator cavity. [ABSTRACT FROM PUBLISHER]

This communication investigates the application of metamaterial absorber (MA) to waveguide slot antenna to reduce its radar cross section (RCS). A novel ultra-thin MA is presented, and its absorbing characteristics and mechanism are analyzed. The PEC ground plane of waveguide slot antenna is covered by this MA. As compared with the slot antenna with a PEC ground plane, the simulation and experiment results demonstrate that the monostatic and bistatic RCS of waveguide slot antenna are reduced significantly, and the performance of antenna is preserved simultaneously. [ABSTRACT FROM PUBLISHER]