Metasurfaces, which are two-dimensional arrays of subwavelength elements, enable versatile control of electromagnetic waves, thereby paving the way for advancements in electromagnetic stealth. Electromagnetic stealth aims to diminish object visibility to radar or other sensors by minimizing their reflection, scattering, or emission of electromagnetic waves. This paper reviews the latest works in microwave electromagnetic stealth devices utilizing metasurfaces, including absorbing, scattering, cloaking and multifunctional stealth techniques. A comprehensive analysis and characterization of these stealth metasurface based devices are presented, focusing on their working principles, performance characteristics, and the associated challenges. Additionally, we explore prospects and opportunities for further research. This paper offers a thorough and up-to-date survey of the current status and future directions of this emerging field.

This paper presents a design method to implement an antenna array characterized by ultra-wide beam coverage, low profile, and low Sidelobe Level (SLL) for the application of Unmanned Aerial Vehicle (UAV) air-to-ground communication. The array consists of ten broadside-radiating, ultrawide-beamwidth elements that are cascaded by a central-symmetry series-fed network with tapered currents following Dolph-Chebyshev distribution to provide low SLL. First, an innovative design of end-fire Huygens source antenna that is compatible with metal ground is presented. A low-profile, half-mode Microstrip Patch Antenna (MPA) is utilized to serve as the magnetic dipole and a monopole is utilized to serves as the electric dipole, constructing the compact, end-fire, grounded Huygens source antenna. Then, two opposite-oriented end-fire Huygens source antennas are seamlessly integrated into a single antenna element in the form of monopole-loaded MPA to accomplish the ultrawide, broadside-radiating beam. Particular consideration has been applied into the design of series-fed network as well as antenna element to compensate the adverse coupling effects between elements on the radiation performance. Experiment indicates an ultrawide Half-Power Beamwidth (HPBW) of 161° and a low SLL of −25 dB with a high gain of 12 dBi under a single-layer configuration. The concurrent ultrawide beamwidth and low SLL make it particularly attractive for applications of UAV air-to-ground communication.

An active, compact, wideband, receiving filtenna with power adaptation for space-limited wireless platforms is presented. By organically combining a filtering antenna and a Variable Gain Amplifier (VGA), the proposed co-designed active filtenna is achieved. Its power adaptation is empowered by controlling gain of the VGA unit. A demonstrated prototype with a compact overall size is fabricated, assembled and measured. Good performances are achieved. Furthermore, in any condition, the proposed active filtenna displays outstanding impedance matching (|S₁₁| < −10 dB) and high passband skirt selectivity at upper and lower stopbands (Selectivity ≥ 170 dB/GHz).