Systems and techniques are described that provide for enhanced gain and radiation characteristics of antennas. The systems and techniques employ layers or cards of fractal plasmonic surfaces to provide gain to the antennas. The fractal plasmonic surfaces each include a close-packed arrangements of resonators having self-similar or fractal shapes, which may be referred to as “fractal cells.” The cards can be held by a frame adapted to fit an antenna. The FPS cards can provide benefits for gain, field emission, directivity, increased bandwidth, power delivery, and/or heat management. One or more dielectric layers or cards may be used to enhance gain and/or directivity characteristics.

Disclosed is an absorbent structure which is a honeycomb structure extending between two end faces and which includes tubular cells, each cell having walls delimiting the cell, the walls extending between the two end faces, the walls being formed from a dielectric material, at least one cell having at least one strip of electrically conductive coating arranged in at least one wall or over a surface of at least one wall, the honeycomb structure being characterized by parameters chosen so that the absorbent structure provides an attenuation of at least 10 dB for each incident wave in a frequency range having a frequency spread greater than or equal to 15 GHz.

An electromagnetic energy absorber comprising a thin electrically-conductive ground plane as a base. Dielectric layers are positioned over the ground plane and high impedance surface (HIS) as a top layer. The impedance layer can be formed by loading the lumped resistor to a metallic grating like an FSS (Frequency Selective Surface). An air-spacer between the substrates has replaced the problem of the large electrical thickness of the substrate with effective permittivity. Metamaterial structures enable control over the resonant frequencies, and performance is enhanced over a broad frequency band. In addition, two broadband reflective-type linear to orthogonal polarization converters are disclosed that provide improved bandwidth and angular stability performance.

A low profile array (LPA) includes an antenna element array layer having at least one Faraday wall, and a beamformer circuit layer coupled to the antenna element array layer. The beamformer circuit layer has at least one Faraday wall. The Faraday walls extends between ground planes associated with at least one of the antenna element array layer and the beamformer circuit layer.

Embodiments of the present disclosure provide example antennas, example microwave devices, and example communications systems. One example antenna includes an antenna body and a filter component. The antenna body includes an antenna aperture and an optical axis. The antenna body is configured to send and receive a radio frequency signal that passes through the antenna aperture. The filter component is located at the antenna aperture and is disposed perpendicular to the optical axis, where the filter component is configured to filter an interference signal in the radio frequency signal. The filter component includes a filter layer and a support component, where the filter layer is formed by a lossy dielectric, where the support component is configured to support the filter layer, and where the filter layer forms a spatial structure similar to a shutter.

Systems according to the present disclosure provide one or more surfaces that function as power radiating surfaces for which at least a portion of the radiating surface includes or is composed of “fractal cells” placed sufficiently closed close together to one another so that a surface wave causes near replication of current present in one fractal cell in an adjacent fractal cell. The fractal cells may lie on a flat or curved sheet or layer and be composed in layers for wide bandwidth or multibandwidth transmission. The area of a surface and its number of fractals determines the gain relative to a single fractal cell. The boundary edges of the surface may be terminated resistively so as to not degrade the cell performance at the edges. The fractal plasmonic surfaces can be utilized to facilitate electrical conduction with lower ohmic resistance than would otherwise be possible in the absence of the fractal plasmonic surface(s) at the same temperature.

A measurement device for measuring performance of at least one antenna system in a first frequency band and in a second frequency band. The measurement device including an outer chamber having inwardly radio frequency reflective walls configured to enclose the antenna system, an inner chamber deployable inside the outer chamber, the inner chamber having radio frequency absorptive walls configured to enclose the antenna system, a first test antenna arrangement arranged inside the outer chamber and configured for a measurement operation in the first frequency band, and a second test antenna arrangement arranged inside the inner chamber and configured for a measurement operation in the second frequency band, thereby enabling measuring performance of the antenna system in a reflective radio frequency environment by the first test antenna arrangement and measuring performance in an essentially anechoic radio frequency environment by the second test antenna arrangement.

The disclosure discloses a controllable wave-absorbing metamaterial including a substrate and a metamaterial unit array layer. Each conductive geometric unit includes a first hollow structure, second hollow structures, and conductive geometric structures. The second hollow structures are respectively extended from four vertices of the first hollow structure, and the conductive geometric structure is disposed between each two adjacent second hollow structures. The first end of the second hollow structure is provided with a varactor diode connected to the conductive geometric structures at both sides, the second end of the second hollow structure is provided with a fixed capacitor and a fixed resistor; the fixed capacitor is connected to the conductive geometric structure at one side, and the fixed resistor is connected to the conductive geometric structure at the other side. Therefore, active adjustment on a wave-absorption frequency band can be implemented, and power consumption is very low.

An air duct formed from an electromagnetic wave absorber in the form of a sheet is disclosed. The sheet can be bent into a duct or scored, and folded at the score lines to bring the ends of the sheet into proximity. The ends can then be joined by adhesive, welding, or mechanical fasters. The air ducts disclosed herein provide dual functions of providing ventilation for electronic components in an electronic module, while at the same time, reducing electromagnetic interference (EMI). One or more air ducts, of the same or different dimensions, shapes, volumes can be combined with electronic modules, such as a server, to provide both ventilation and EMI suppression to various components within the electronic module.

An air duct formed from an electromagnetic wave absorber in the form of a sheet is disclosed. The sheet can be bent into a duct or scored, and folded at the score lines to bring the ends of the sheet into proximity. The ends can then be joined by adhesive, welding, or mechanical fasters. The air ducts disclosed herein provide dual functions of providing ventilation for electronic components in an electronic module, while at the same time, reducing electromagnetic interference (EMI). One or more air ducts, of the same or different dimensions, shapes, volumes can be combined with electronic modules, such as a server, to provide both ventilation and EMI suppression to various components within the electronic module.