In this paper, based on transformation electromagnetics, the design procedure of a lens antenna, which steers the radiated beam of a patch array, is presented. Laplace's equation is adopted to construct the mapping between the virtual space and the physical space. The two dimensional (2D) design method can be extended to a potential three-dimensional (3D) realization, and with a proper parameter simplification, the lens can be further realized by common metamaterials or isotropic graded refractive index (GRIN) materials. Full wave simulations are performed to validate the proposed concept. It is observed that by placing the lens on a feeding source, we are able to steer the radiation emitted by the latter source.

The emergence of metasurfaces provides a novel strategy to tailor the electromagnetic response of electromagnetic waves in a controlled manner by judicious design of the constitutive meta-atom. However, passive metasurfaces tend to perform a specific or limited number of functionalities and suffer from narrow-frequency-band operation. Reported reconfigurable metasurfaces can generally be controlled only in a 1D configuration or use p-i-n diodes to show binary phase states. Here, a 2D reconfigurable reflective metasurface with individually addressable meta-atoms enabling a continuous phase control is proposed in the microwave regime. The response of the meta-atom is flexibly controlled by changing the bias voltage applied to the embedded varactor diode through an elaborated power supply system. By assigning appropriate phase profiles to the metasurface through voltage modulation, complex beam generation, including Bessel beams, vortex beams, and Airy beams, is fulfilled to demonstrate the accurate phase-control capability of the reconfigurable metasurface. Both simulations and measurements are performed as a proof of concept and show good agreement. The proposed design paves the way toward the achievement of real-time and programmable multifunctional meta-devices, with enormous potential for microwave applications such as wireless communication, electromagnetic imaging, and smart antennas.

Bessel beams have attracted considerable interest due to their intriguing nondiffraction and self‐healing properties. Such beam can be generated by conventional devices that are more or less subjected to issues of low efficiency, complex manufacturing, and bulky size. Here, an electronically engineered reflective metasurface is designed to generate and flexibly manipulate Bessel‐like beams over a broad frequency range in the microwave regime. Due to the dynamic resonance feature of the metasurface, the phase profile can be easily adjusted for different applications. The nondiffraction feature is illustrated by analyzing several configurations with different nondiffraction area of the Bessel‐like beam, while the self‐healing property is verified by placing a metallic obstacle in the propagation path. The dynamic control of functional frequency and propagation direction of Bessel‐like beams is realized by controlling the external DC bias voltage applied to the metasurface. Experimental validation of the aforementioned features is perfectly consistent with numerical simulations. Owing to the flexible control, broad bandwidth, and high‐efficiency properties, the proposed Bessel‐like beam generator suggests potential applications in microwave domain such as focusing, wireless power transmission, and other complex demands such as beam steering.

Vortex electromagnetic (EM) waves hold promise for their ability to significantly increase the transmission capacity of wireless communication systems via the torsion resistance defined by different topological charges associated with the orbital angular momentum (OAM). However, the application of vortex waves in remote distance transmission is limited by its characteristic of divergence. In this paper, a lens based on a phase-modulation metasurface (MS) is proposed that enables vortex EM waves to converge, thereby improving their propagation performance at microwave frequencies. A phase-shift distribution on the plane of the MS is obtained based on the concept of the optical converging axicon, which can convert a Laguerre-Gaussian (LG) beam to a Bessel beam based on changing the propagation direction. Simulation results verify the ability of the MS lens to achieve OAM beam focusing, which is advantageous for enhancing the propagation directivity and increasing the gain in the main lobes of vortex waves. This is of particular importance in microwave wireless communication applications.

This paper presents a radar cross-section (RCS) reduction technique by using the coding diffusion metasurface, which is optimised through a random optimization algorithm. The design consists of two unit cells, which are elements ‘1’ and ‘0’. The reflection phase between the two-unit cells has a 180° ± 37° phase difference. It has a working frequency band from 8.6 GHz to 22.5 GHz, with more than 9 dB RCS reduction. The monostatic RCS reduction has a wider bandwidth of coding diffusion metasurface as compared to the traditional chessboard metasurface. In addition, the bistatic performance of the designed metasurfaces is observed at 15.4 GHz, which shows obvious RCS reduction when compared to a metallic plate of the same size. The simulated and measured result shows the proficiency of the designed metasurface.