A novel high-efficiency polarization-selective bifunctional metasurface (MS) is proposed, which can realize cross-polarized focusing transmission for left-handed circular polarization (LHCP) incidence and co-polarized specular reflection for right-handed circular polarization (RHCP) incidence. As an example of its practical application, the designed MS is applied to form an RHCP folded transmitarray antenna (FTA) whose feed source (FS) is integrated with the bottom metallic surface. To prove the concept, a prototype of millimeter-wave (MMW) FTA based on the proposed MS is numerically simulated, physically implemented, and experimentally measured. The measured results coincide well with the simulated ones, showing a peak gain of 23.6 dBi at 27.7 GHz with the peak aperture efficiency of 43.1%, a 3 dB gain bandwidth of 15.8% (25–29.3 GHz), and a 3 dB axial-ratio (AR) bandwidth over 29.6%. The proposed high-performance antenna has the advantages of low profile, high efficiency, integration design, and broad bandwidth, which may have promising applications in the fifth-generation MMW communication system. The proposed MS and its application to high-gain antenna may promote the uses of MS to real-world applications in satellite communication, radar detection, and wireless communication.

Achieving independent control of amplitude and phase of electromagnetic (EM) wave by a thin flat device is very important in wireless and photonic communications. However, most of the reported metasurfaces, so far, have only realized simultaneous control of amplitude and phase for linearly polarized EM wave. This article presents a strategy to realize independent and arbitrary control of amplitude and phase responses for circularly polarized EM wave by using a dual-phase hybrid metasurface that integrates both geometric and propagation phases. A beam deflector with tailorable amplitude is then designed to verify the proposed strategy. As a proof of concept of its practical application, a circularly polarized reflector antenna with high gain and extremely low side-lobe is implemented by the proposed metasurface. Experimental results are in good accordance with the simulation ones, demonstrating that the side-lobe of the designed antenna can be reduced by 8 dB compared with a reflector antenna actualized by phase-only metasurface. The proposed methodology and the metasurface can provide a new degree of freedom in controlling circularly polarized waves by simultaneous phase and amplitude modulations, which may trigger many interests in electromagnetic/optical integration and complex EM wave manipulations, as well as advanced meta-devices for real-world applications.

This paper presents an active cylindrical metasurface with spatial reconfigurability to achieve dynamic control of the RCS reduction. The proposed metasurface is designed based on the combination of microwave transmission network and Mie scattering. In particular, by modulating the spatial coding sequence of PIN diodes in meta-atoms, the surface impedance of the metasurface can be dynamically changed, which enables an active metasurface to operate in an expanded frequency band via time-division multiplexing technique. Both simulated and measured results demonstrate that the proposed cylindrical metasurface with ultrathin thickness of 0.018λ can be continuously tuned across a wide fractional bandwidth over 32% for reducing backward scattering by 10 dB. The proposed metasurface with ultra-thin thickness, tunability, conformal profile, and high performance, may be applied to wideband RCS reduction, as well as advanced non-invasive detection, communication, etc.

The Pancharatnam-Berry (PB) phase or geometric phase metasurfaces have been extensively investigated in order to achieve flexible manipulation of circularly polarized (CP) electromagnetic waves. Typically, the thickness or structural complexity of the transmission-type PB metasurfaces may limit their efficiency. Here, we propose a single-substrate, ultrathin, transmission-type PB phase metasurface with a transmission coefficient of approximately unity for CP waves. To achieve this, the Huygens’ principle is applied in the design. The proposed metasurface is capable of achieving high-efficiency transmission amplitude of two orthogonal linear polarizations in the working frequency band, as well as the 180-degree phase difference. Thus, high-efficiency CP transmission with nearly unity can be obtained, and 360 degrees of phase modulation can be covered by rotating the element. Meanwhile, the proposed metasurface is a single-substrate structure and its thickness is only 0.06λ ₀ , offering a simple yet efficient method for antenna design. As a proof of concept, a metalens antenna and an orbital angular momentum (OAM) wave generator based on the proposed metasurface are experimentally demonstrated. The measured results show good agreements with the full-wave simulations, successfully verifying the design theory. The proposed metasurface offers an alternative platform for designing high-performance devices with the advantages of light weight, low cost, and simple fabrication.

Achieving multiple electromagnetic (EM) functionalities on a shared aperture in dual frequency bands is crucial for many applications; however, existing dual-band metasurfaces are affected by limited channels or narrow bandwidths. Herein, we propose a reflective coding metasurface that empowers four independent EM functionalities in quad-polarization channels in two wide frequency bands. By integrating quasi-I-shaped and cross-shaped metastructures, the meta-atom can feature independent phase modulation for two orthogonally linear and two decoupled circular polarizations at low and high frequencies, respectively. To validate the proposed metasurface, a multifunctional metadevice is designed that integrates beam deflection, diffuse scattering, and vortex beam generation. Both experimental and simulation results indicate distinct wavefront tailoring in each channel. The proposed multi-functional metasurface with low cross-talk and independent phase modulation depending on frequencies and polarizations may unlock the metasurfaces’ potentials for complete wavefront control in EM function integration, multiple channel communication, polarization optics, etc.

A compact directional MIMO antenna operating in 2.4 and 5 GHz wireless local area network (WLAN) bands is presented. The compactness of the proposed multiple-input multipleoutput (MIMO) antenna can be attained through using miniaturized antenna elements and meanwhile employing an extremely narrow edge-to-edge inter-element space (3 mm). Two novel miniaturized planar inverted-F antenna (PIFA) elements which share a common ground are designed, and each element has a dimension of 31 mm × 17 mm and a profile of 4.2 mm. By etching three slots on the ground, the port isolation can be significantly enhanced, which can even reach a maximum of 54 dB at 2.45 GHz. A desirable directional radiation pattern is obtained, and the calculated envelope correlation coefficient is better than 0.01.