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.

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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

In this paper, a dual band full duplex monopole antenna is proposed for WLAN application. For dual band operation an L-shaped arm is added to both transmitter and receiver antenna. Receiver ports of the proposed bi-static transmitter-receiver antenna is fed through the differential ports of a dual band ring hybrid coupler to achieve isolation between transmitting and receiving ports. The transmitting and receiving antennas both resonate at 2.42 GHz and 5.25 GHz. The proposed structure gives an isolation of 41 dB and 56 dB at 2.42 GHz and 5.25 GHz respectively. At 2.42 GHz and at 5.25 GHz the proposed structure gives broadside peak gain of 4.17 dBi and 6.8 dBi and 3.6 dBi and 5.25 dBi for transmitting and receiving antennas respectively. The proposed antenna system is fabricated and simulated results are experimentally verified. Measured results are nearly similar to the simulated results.

A Dual Band Full-Duplex Monopole Antenna for WLAN Application

An eight-element wideband multiple-input multiple-output (MIMO) antenna for the fifth-generation (5G) mobile terminal is proposed. The antenna elements are placed along both long side edges of the mobile terminal with a profile of 6 mm. The proposed monopole-inspired antenna element shows a good impedance match, isolation, and diversity parameter across a very wide bandwidth of 78 % (3.2-7.3 GHz), and it can cover the 5G NR n77/n78/n79/n96, LTE 46, and WLAN 5 GHz bands. The result shows that the MIMO antenna can offer inter-element isolation better than 12 dB, envelope correlation coefficient (ECC) below 0.069, and a peak channel capacity of 42.7 bps/Hz across the desired 5G bands. The specific absorption rate (SAR) analysis of the proposed MIMO antenna with a human head has exhibited SAR levels (0.41 W/Kg and 0.33 W/Kg at two resonating frequencies 3.9 GHz and 5.8 GHz, respectively) much lower than the Federal Communications Commission (FCC) permissible limit (1.6 W/Kg over 1 gram tissue).

Wideband Monopole Eight-Element MIMO Antenna for 5G Mobile Terminal

In this paper, a triple band dual mode patch antenna is proposed Modified mushroom resonators are embedded in the substrate of the conventional patch antenna to induce zeroth and negative order resonances in addition to the existing positive order resonances The proposed antenna exhibit two patch like modes (n = ±1) and one monopolar mode (n = 0)

Dual mode triple band patch antenna based on two-dimensional composite right/left-handed transmission lines

In this article, an accurate numerical dispersion relationship is developed for 3-D alternating direction implicit finite difference time domain (ADI FDTD) with artificial anisotropy. The numerical dispersion relation with accurate mathematical model helps to calculate the anisotropic parameters, which are used to control the error of the numerical phase velocity. Numerical example shows that the proposed method helps to reduce the numerical dispersion significantly. The effects of anisotropic parameters on the numerical dispersion with different mesh resolution, courant number, and cell dimension ratio, are shown for three-dimensional anisotropic ADI-FDTD. A comparison has been made for anisotropic ADI FTDD and conventional ADI FDTD in terms of accuracy and CPU time for the calculation of resonant frequencies of rectangular cavity. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3109–3112, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22961

An accurate analysis of numerical dispersion for 3‐D ADI‐FDTD with artificial anisotropy

This paper proposes a compact fourth-order six-step locally one-dimensional finite-difference time-domain (CFO-LOD6-FDTD) method. Stability analysis shows that the proposed method is unconditionally stable. The proposed method uses compact fourth-order finite-difference approximation for the space derivatives. For every time-step and mesh-size, it gives less numerical dispersion than the six-step LOD-FDTD (LOD6-FDTD) method.

Kumar Vaibhav Srivastava

Papers

A Dual Band Full-Duplex Monopole Antenna for WLAN Application

Wideband Monopole Eight-Element MIMO Antenna for 5G Mobile Terminal

Dual mode triple band patch antenna based on two-dimensional composite right/left-handed transmission lines

An accurate analysis of numerical dispersion for 3‐D ADI‐FDTD with artificial anisotropy

A compact fourth-order six-step LOD-FDTD method