Nowadays, low-frequency electromagnetic interference (<2.0 GHz) remains a key core issue that plagues the effective attenuation performance of conventional absorption devices prepared via the component-morphology method (Strategy I). According to theoretical calculations, one fundamental solution is to develop a material that possesses a high e' but lower e″. Thus, it is attempted to control the dielectric values via applying an external electrical field, which inducts changes in the macrostructure toward a performance improvement (Strategy II). A sandwich-structured flexible electronic absorption device is designed using a carbon film electrode to conduct an external current. Simultaneously, an absorption layer that is highly responsive to an external voltage is selected via Strategy I. Relying on the synergistic effects from Strategies I and II, this device demonstrates an absorption value of more than 85% at 1.5-2.0 GHz with an applied voltage of 16 V while reducing the thickness to ≈5 mm. In addition, the device also shows a good absorption property at 25-150 °C. The method of utilizing an external voltage to break the intrinsic dielectric feature by modifying a traditional electronic absorption device is demonstrated for the first time and has great significance in solving the low-frequency electromagnetic interference issue.

A Voltage-Boosting Strategy Enabling a Low-Frequency, Flexible Electromagnetic Wave Absorption Device.

Reactive matching is extended to wide bandwidths using the impedance property of LC-ladder filters. In this paper, we present a systematic method to design wideband low-noise amplifiers. An SiGe amplifier with on-chip matching network spanning 3-10 GHz delivers 21-dB peak gain, 2.5-dB noise figure, and -1-dBm input IP3 at 5 GHz, with a 10-mA bias current.

A 3-10-Ghz low-noise amplifier with wideband LC-ladder matching network

This work was supported by National Basic Research Program of China
(Project No. 2013CB933301) and National Natural Science Foundation of
China (Project No. 51272038). L.V.B. was supported by China Postdoctoral
Science Foundation. A.O.G. was supported by the Volkswagen
Foundation (Germany) and via the Chang Jiang (Yangtze River)
Chair Professorship (China). G.P.W. acknowledges support from the
Center for Nanoscale Materials, a U.S. Department of Energy Office of
Science User Facility, and support by the U.S. Department of Energy,
Office of Science, under Contract No. DE-AC02-06CH11357. In addition,
the authors acknowledge financial support obtained from the Virtual
Institute for Theoretical Photonics and Energy. This review is part of the
Advanced Optical Materials Hall of Fame article series, which recognizes
the excellent contributions of leading researchers to the field of optical
materials science.

/pdf/broadband-metamaterial-absorbers-1ivwczjh1w.pdf

Broadband Metamaterial Absorbers

In this paper, we designed a novel core-shell composite for microwave absorption application in which the α-Fe2O3 and the porous CoFe2O4 nanospheres served as the core and shell, respectively. Interestingly, during the solvothermal process, the solvent ratio (V) of PEG-200 to distilled water played a key role in the morphology of α-Fe2O3 for which irregular flake, coin-like, and thinner coin-like forms of α-Fe2O3 can be produced with the ratios of 1:7, 1:3, and 1:1, respectively. The porous 70 nm diameter CoFe2O4 nanospheres were generated as the shell of α-Fe2O3. It should be noted that the CoFe2O4 coating layer did not damage the original shape of α-Fe2O3. As compared with the uncoated α-Fe2O3, the Fe2O3@CoFe2O4 composites exhibited improved microwave absorption performance over the tested frequency range (2-18 GHz). In particular, the optimal reflection loss value of the flake-like composite can reach -60 dB at 16.5 GHz with a thin coating thickness of 2 mm. Furthermore, the frequency bandwidth corresponding to the RLmin value below -10 dB was up to 5 GHz (13-18 GHz). The enhanced microwave absorption properties of these composites may originate from the strong electron polarization effect (i.e., the electron polarization between Fe and Co) and the electromagnetic wave scattering on this special porous core-shell structure. In addition, the synergy effect between α-Fe2O3 and CoFe2O4 also favored balancing the electromagnetic parameters. Our results provided a promising approach for preparing an absorbent with good absorption intensity and a broad frequency that was lightweight.

Coin-like α-Fe2O3@CoFe2O4 Core–Shell Composites with Excellent Electromagnetic Absorption Performance

Ieee transactions on antennas and propagation

A polarization-insensitive frequency selective rasorber (FSR) geometry with dual-transmission and dual-absorption band has been presented in this paper. Two passbands appear inside a wide absorption band, thereby resulting in multiple absorption regions surrounding the transmission peaks. The proposed FSR comprises of one absorptive layer and one transmissive layer, separated by an air spacer, and each of them is realized by patterning geometries in a periodic arrangement. The transmission bands are obtained at 5.30 GHz and 8.10 GHz with insertion losses of 0.79 dB and 0.46 dB, respectively. A wide absorption band, originally realized between 2.26 GHz and 8.79 GHz, gets divided into multiple absorption regions due to the presence of in-band transmission peaks and shows two discrete absorption bands from 2.01 GHz to 4.95 GHz and 5.81 GHz to 7.45 GHz. The structure achieves an overall fractional bandwidth of 118.20% with respect to its centre frequency. Polarization-insensitivity as well as angular stability for different polarizations (till 30 angle of incidence) are also observed in the structure. As compared to the existing dual-transmission band rasorber geometries, the proposed FSR offers a simpler design topology, lower footprint, and larger operating bandwidth. Proposed structure has been fabricated and measured to verify proposed design.

A Polarization-Insensitive Dual-Transmission Band Frequency Selective Rasorber

A linearly polarized two-dimensional beam-forming antenna using electrically reconfigurable frequency selective surface (FSS) has been proposed in this manuscript. The antenna structure incorporates a coaxial fed patch antenna and a recon-figurable FSS layer, kept above the patch radiator at a height of 0.41λ0 (λ0 represents the free space wavelength at the resonant frequency). The reconfigurable superstrate FSS layer consists of 6× 6 unit cells. The dimension of each unit cell is 0.24λ0 ×0.24λ0. To make the FSS layer electrically reconfigurable, each unit cell consists of two PIN diodes. The FSS superstate is further divided in four sections and each section contains 3 × 3 unit cells. Each sections are connected to the individual biasing pads for the purpose of biasing. The overall dimension of the proposed structure is 1.6λ0 ×1.6λ0 × 0.44λ0. When the reconfigurable FSS is illuminated by the coaxial fed patch, the composite system can generate thirteen individual radiating modes, which interms radiating in thirteen individual direction in 3D space. The antenna operates at a resonant frequency of 4 GHz and a maximum gain of 8.06 dBi is achieved with a maximum of 34° tilting of the beam.

Beam-Forming Antenna Based on Electrically Reconfigurable Frequency Selective Surface

Radar cross section (RCS) reduction is thoroughly studied among electrical engineers so as to attain stealth capabilities of any object of interest. One particular kind of absorber which is in high demand is of the transparent and flexible kind. Transparent absorbers find their applications in various defence related applications such as in wind shield of aircraft and vehicles. Manufacturing of transparent metamaterial absorbers is a challenge as it is always a trade off between electrical performance and maintaining optical transparency. In this paper the authors present a technique of optimizing the electrical and optical performance of transparent absorber manufactured with commercially available Polyethylene Terephthalate (PET) coated Indium Tin Oxide (ITO) sheets.

Energy Optimization in Laser Micro-machining of Transparent Metamaterial Absorber

In this article two miniaturized artificial magnetic conductor(AMC) unit cells have been designed to reduce the RCS of microstrip patch antenna at X-band. The scattering performance of the patch antenna has been determined by using one checkerboard metasurface and one aperiodic metasurface to improve the scattering performance of the antenna. The antenna provides the wide impedance bandwidth of 26%. Because of the AMC metasurface's effectiveness in reducing surface waves, the antenna's radiating performance has been significantly enhanced as a result. While the results of the simulation show a remarkable RCS reduction of 14 dB throughout the X-band for both the polarizations, the results of the measurement show that they are in good agreement with simulated response. In order to facilitate a deeper comprehension of the scattering performance, 3D RCS plots have also been presented. The radiation performance of the antenna has been measured, and the results show a pattern that is almost identical to the one that was simulated.

In-band RCS Reduction of Microstrip Patch Antenna using Artificial Magnetic Conductors at X-Band for Stealth Technology

This paper presents non singular and thin cylindrical electromagnetic cloaks which are designed by coordinate transformation based on linear function. The derived material parameters are free of any infinities and singularities at the inner boundary of cloak which is good for its realization. The effects of parameters ‘s’ and ‘b=a’ ratio have been discussed on the performance of cloak. All the designs have been validated by simulation results.

Kumar Vaibhav Srivastava

Papers

A Polarization-Insensitive Dual-Transmission Band Frequency Selective Rasorber

Beam-Forming Antenna Based on Electrically Reconfigurable Frequency Selective Surface

Energy Optimization in Laser Micro-machining of Transparent Metamaterial Absorber

In-band RCS Reduction of Microstrip Patch Antenna using Artificial Magnetic Conductors at X-Band for Stealth Technology

Nonsingular and thin cloak using linear transformation function