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Experimental Demonstration of Antenna Isolation Improvement using Planar Resonant Absorbers
Sofian Hamid1, Dirk Heberling1,2
1RWTH Aachen, Germany; 2Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR)
Antenna isolation improvement using two different setups is experimentally demonstrated. Three resonant absorbers, which have been initially fabricated and characterized as free space absorbers, are inserted between pairs of horn and monopole antennas. The goal is to improve the isolation between those pairs and compare which absorber performs better in terms of bandwidth and isolation improvement. All absorbers have a similar surface dimension of 25.6 cm x 25.6 cm. The ultra-thin absorber, which is a narrow band free space absorber, improves the isolation in a narrow band, too. So, it is only effective to improve the isolation of a pair of narrow band antennas. The magnetic sheet and the dielectric resonator absorber cover the whole X-band as free space and also surface wave absorbers. The latter has the best isolation improvement within this band with an average of 23 dB for the horn setup and 19 dB for the monopole setup.
Lightning Direct Effect and Electromagnetic Shielding Analysis of Conductive Aircraft Composite
Richard Xian-Ke Gao1, Hui Min Lee1, Zaifeng Yang1, Warintorn Thitsartarn2, Si-Ping Gao3, En-Xiao Liu1
1Institute of High Performance Computing, Singapore; 2Institute of Materials Research and Engineering, Singapore; 3National University of Singapore, Singapore
In order to enhance the lightning protection and electromagnetic shielding capabilities of composite aircraft, the electromagnetic behavior of carbon fiber reinforced polymer (CFRP) composite is characterized in this paper. Through the study of lightning direct effect in terms of current density distribution in each composite ply under lightning strike, the scheme to increase electrical conductivity is proposed for different fiber configurations of composite. The high frequency electromagnetic shielding effectiveness of composite is also studied and analyzed by extracting the equivalent permittivity using Nicholson-Ross-Weir method based on the measured scattering parameters. Good agreement is obtained between the results of simulation and validation experiment for shielding effectiveness of the composite.
Transparent Graphene-Based Absorber for Next Generation Wireless 5G Technology
Alessandro Giuseppe D'Aloia1,2, Marcello D'Amore1,2, Maria Sabrina Sarto1,2
1DIAEE - Sapienza University of Rome; 2Research Center for Nanotechnology applied to Engineering of Sapienza University
The design of new transparent and metal-free absorbers for the upcoming wireless fifth-generation (5G) technology is investigated. To this purpose, innovative absorbers made of graphene-polyethylene terephthalate (PET) laminates separated by PET spacers are proposed. The graphene-PET laminates are modelled as homogeneous single layers characterized by effective conductivities whose values are obtained by means of a new analytical procedure with the aim of optimizing the absorption performances. Reflection, transmission and absorption coefficients of designed absorbers are computed considering optimum theoretical or feasible values of effective conductivities for graphene-PET laminates in order to achieve the best absorbing performance between 24.25 GHz and 42.5 GHz, i.e. in the 5G next generation bandwidth.
An Angularly Stable Frequency Selective Surface with Vent Holes for 5G Electromagnetic Shielding
Liping Yan1, Liuliu Xu1, Xiang Zhao1, Richard Xian-ke Gao2
1Sichuan University, China, People's Republic of; 2Institute of High Performance Computing, A* Star, Singapore
A frequency selective surface (FSS) based electromagnetic shielding structure with vent holes is proposed for 5G electromagnetic (EM) shielding. The proposed FSS structure is developed for the demanding requirements of EM shielding at 28 GHz without worsening the ventilation. Through a number of simulations using full-wave analysis, the optimized FSS achieves a bandwidth of more than 2 GHz with 30 dB shielding effectiveness. Moreover, the proposed FSS-based shielding structure has the advantage of angular response stability up to 60° for both TE and TM polarization. Results show that there is a good agreement between the measurement and the simulation.
Challenges of RF Absorber Characterization: Comparison Between RCS- and NRL-Arch-Methods
Willi Hofmann, Christian Bornkessel, Andreas Schwind, Matthias A. Hein
Technische Universität Ilmenau, Germany
Shielded anechoic chambers have become indispensable for radiated EMC and antenna measurements. The quality of such measurement facilities and thus of the measurements performed inside such environments depends sensitively on the reflectivity of the RF absorbers used. On the other side, the characterization of RF absorbers to ensure optimal measurement conditions is a challenging task. In this paper, the reflectivity of pyramidal absorbers is analyzed for frequencies between 1 GHz and 10 GHz using two different measurement methods: The NRL-Arch- and the RCS-method. The aim is to determine possible influences of the different approaches on the detectable reflectivity. Necessary post-processing steps and their applicability to the measured data are also discussed. It is shown that both methods can lead to nearly identical results, but even weak echoes of the surroundings may have major impact on the measurable reflectivity and thus lead to erroneous conclusions.