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Owing to the capability of providing a certain phase gradient on the interface between two media, metasurfaces have shown great promise for altering the directions of outgoing electromagnetic (EM) waves arbitrarily. With the suitable arrangement of particles on metasurfaces, anomalous reflection and refraction have been observed in wide frequency ranges. To completely control the propagation of EM waves, both phase and amplitude profiles are required in some applications. Herein, we propose a new type of metasurface with both phase and amplitude modulations, which is composed of C-shaped particles and can generate and control multiple beams using amplitude and phase responses simultaneously. An addition theorem of complex reflection coefficients is presented to acquire various states of multiple beams reflected from designed metasurfaces. Meanwhile, the intensities of multiple beams can be separately modulated as desired benefitting from the independent controls of phase and amplitude profiles. All the experimental results have good agreements with the numerical simulations. The presented method opens a new way to form and manipulate multiple beams using metasurfaces, which can find potential applications in beam shaping, radar detection systems, and high-quality holography. [ABSTRACT FROM AUTHOR]

Antennas and metasurfaces have enabled a number of far-field manipulation functions. According to the addition theorem of multipoles, near fields have richer spatial spectra than far fields; hence, in the near-field region, it is easier to achieve complex manipulations on field distributions. In this paper, an algorithm is presented to synthesize the near fields of source arrays. Given target distributions of near-field intensities and also predefined source magnitudes, the algorithm will find the needed source phases, which can then be applied on active antenna arrays and passive metasurfaces to induce the target distribution of fields. The algorithm adopts the dyadic Green’s function as the propagator, and hence, it naturally takes account of the near-field and vector properties of electromagnetic fields. As a typical application of the algorithm, an example is given to obtain the excitation phases of a dipole array, which is then physically imitated by a coding metasurface. Experimental measurement is performed and the result proves the validity of the algorithm. From the perspective of information metasurface, the algorithm finds the phase-coding pattern of metasurface to achieve specific functions. [ABSTRACT FROM AUTHOR]

We propose a novel linearly polarized, dual-band, and high-gain transmitarray based on multilayer frequency-selective surface structures. This is the first time for actualizing a dual-band transmitarray with more than 50% aperture efficiency. The unit cell is composed of four metallic layers without dielectric substrates between every two layers, which results in good match, low insertion loss, and high radiation efficiency. We introduce two kinds of rectangular slots in the design to control the magnitude and phase range of transmission coefficients in the two designed frequency bands through changing the slot length. The isolation between two bands is excellent and the interference can be ignored. The induced electric fields of the cell are also investigated in order to elucidate the working principle intuitionally. The proposed dual-band transmitarray with a square aperture ( $240 \times 240$ mm ^{2} ) is designed, fabricated, and measured. A linearly polarized corrugated horn antenna is adopted to improve the aperture efficiency and ensure the similarity of the radiation patterns on E-plane and H-plane. Full-wave simulation and experimental results have very good agreements. It is demonstrated that the dual-band transmitarray works in two frequency bands 11.8–12.2 and 17.5–18.1 GHz simultaneously, and the peak gains in the designed central frequencies 12 and 18 GHz are 27.8 and 31.4 dB, respectively, which correspond to the aperture efficiencies (global efficiencies) of 52% and 53%. The proposed design has advantages of simple structure, small weight, low cost, and high performance, making it possible for real applications. [ABSTRACT FROM AUTHOR]