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In this article, we propose a method of designing programmable coding metasurface with a reconfigurable number of reflected beams. Each unit cell of the metasurface is loaded with one varactor to enable adjustable phase responses. The bias, beneath the ground drilled with small holes, is connected to unit cells by a thin via through the holes, to avoid adverse influences on unit cells. To simplify the bias network, a super unit composed of $5 \times 5$ unit cells is taken as the coding element of realizing 2-D coding sequences. With different bias voltages, the unit cell will produce different reflection phases. By programming the bias voltages, the number and directions of reflected beams can be tailored due to different coding sequences. Under normal incident, reflected waves will be split into multiple beams whose directions can be flexibly controlled. We designed a prototype, implemented our design, and carried out experiments. Both the simulation and experiment results show that the number of reflected beams can be reconfigured between 1 and 5. Reflect beam number reconfigurability of such metasurfaces can be readily used as planar reflector of antennas and may find applications in wireless communications. [ABSTRACT FROM AUTHOR]

Inspired by the checkerboard metasurfaces, we propose the design of low-RCS multi-beam linearly polarized (LP) array antenna based on Pancharatnam–Berry (P-B) phase. The antenna array is composed of a number of split-ring resonators (SRRs) with a rotation angle $\alpha $ difference. For circularly polarized (CP) waves, each two adjacent SRRs exhibit $\alpha $ and $2\alpha $ P-B phase differences under feeding and normally illuminating, respectively. Because of this, the SRR array exhibits different phase gradients for radiated and reflected waves. To obtain multiple LP beams, reversed phase gradients for CP waves are alternatively arranged in 1-D or 2-D on the array, leading to two or four beams, respectively. Under normally illuminating, the reflection phases along the array form the checkerboard configuration, which can reduce both the in-band RCS and out-of-band RCS of the antenna array. As an example, we demonstrate a low-RCS four-beam antenna operating in ${X}$ -band. Both the simulated and measured results show that the maximal realized gain of each beam reaches up to about 13.6 dB at 10.2 GHz. To evaluate the RCS reduction performance, we measured specular reflection of the prototype under normal incidence. The reflection is reduced by more than 10 dB in 9.7–10.3 GHz and by more than 5 dB out-of-band in 10.3–14.0 GHz. The design method provides an alternative to the design of low-RCS and low-profile antenna arrays. [ABSTRACT FROM AUTHOR]

High-gain planar antennas always contribute large radar cross section (RCS) to low-observed platforms. To solve this contradiction, we propose a novel design of circularly polarized metasurface antenna characterized by low RCS but high gain. Split ring resonators (SRRs) play a twofold role as the array elements for linear polarization and as the unit cells of metasurface for RCS reduction (RCSR). Four $2 \times 2$ arrayed SRRs are positioned with orthogonal orientations as a super-array element (SAE) and fed with a phase shift of 90° in between for left-handed circular polarization. On the other hand, based on its original arrangement, the open-circuited SAE is also designed to be the super-cell of a (0°, 180°) reflective checkerboard metasurface. Owing to anti-phase energy cancellation and scattering, both the in-band and out-of-band RCS can be dramatically reduced. As indicated by the measurements in antenna, the fabricated prototype operating in $X$ -band exhibits a combined bandwidth (3 dB axial ratio (AR), 3 dB gain drop, and −10 dB impedance matching) of 16% with a maximum realized gain of 17.9 dB. Besides, under normal illumination, the measured specular reflection has been reduced by 10 dB within 9.2–10.8 GHz and by 7.5 dB from 10.8 to 14 GHz. This design method simultaneously ensures high-gain antenna performance as well as meets the requirement for low RCS. [ABSTRACT FROM AUTHOR]

On the basis of generalized Snell’s law of reflection, we propose to achieve frequency scanning radiation by decoupling spoof surface plasmon polaritons (SSPPs) from a corrugated metallic strip (CMS). Phase gradient metasurface (PGM) is utilized to modulate the dispersion behavior of the CMS. Since the phase gradient of the PGM is contrary to the wave vector of SSPPs, the dispersion curve of SSPPs can be translated into the fast wave zone, leading to frequency scanning radiation. As an example, we demonstrate a frequency scanning antenna operating at 8.8–10.7 GHz. A prototype was designed, fabricated, and measured. The measured results show that the prototype can realize continuous beam scanning from 4.8° to 37.2°, with realized gain varying from 8 to 13.1 dB. Owing to surface confinement of SSPPs, the proposed method can be readily extended to the design of conformal frequency scanning antennas on curved faces. [ABSTRACT FROM AUTHOR]

Wireless link has need of an omnidirectional antenna like dipole, but with higher gains. Of course, there is no way of achieving both of them simultaneously. To solve this contradiction, we propose to design multibeam antennas, which divide the radiation pattern of omnidirectional antennas into several beams. The antenna, based on spoof surface plasmon polaritons (SSPPs) mode coupling, consists of a feed monopole and N double-side corrugated metallic strips circling around the feed. The fields of the feed are coupled into SSPP waves that propagate along the strips and radiate at the end, dividing the omnidirectional radiation pattern into several beams. Three X-band prototypes of multibeam antennas with different radiation characteristics were designed, fabricated, and measured. Both numerical simulations and experimental results verify that the antennas are efficient in generating multiple beams with high gain at the predesigned directions. [ABSTRACT FROM AUTHOR]