1,721,388 research outputs found
Fast analysis of large finite arrays with a combined multiresolution-SM/AIM approach
Full text linkWe present a synthesis of the sparse matrix/adaptive integral method (SM/AIM) and the multiresolution (MR) approach for the analysis of electrically large finite arrays, with planar or 3-D radiating elements; the two methods were separately introduced previously. The use of the MR has the effect of a preconditioner and speeds up the convergence rate of the SM/AIM of almost two orders of magnitude, with a total reduction of the numerical complexity with respect to the standard MoM of almost three orders of magnitude
Neural Network Characterization of Reflectarray Antennas
Full text linkAn efficient artificial neural network (ANN) approach for the modeling of reflectarray elementary components is introduced to improve the numerical efficiency of the different phases of the antenna design and optimization procedure, without loss in accuracy. The comparison between the results of the analysis of the entire reflectarray designed using the simplified ANN model or adopting a full-wave characterization
of the unit cell finally proves the effectiveness of the proposed model
MmCn-BBO schemes for electromagnetic problem optimization
No full textIn this communication some variations of the Biogeography Based Optimization, named MmCn-BBO are introduced. They present new features with respect to the standard BBO, aimed to improve the performances of this last algorithm. The comparison among the different schemes, when applied to both benchmark functions and real-world electromagnetic problems, shows the improvement of the here introduced BBO variations and serves to define the most performing among the different proposed variatio
Preliminary results on cylindrical antennas for underwater communication
No full textIn this paper, we investigate the possibility of using cylindrical antennas for short-range underwater communication in freshwater. The performances of three types of cylindrical antennas are compared: dipole, monopole and folded dipole. In freshwater the wavelength is 9-10 times lower than in free space at a specific frequency. This allows a reduction of the antenna actual length and therefore the possibility to work at lower frequencies, where the attenuation introduced by the water is lower, too. The dimensions of the three cylindrical antennas are derived using a well-known analytical model. The antennas have been designed and simulated to work in ISM 433MHz frequency band
New Unit-cell Elements for Perforated Dielectric Transmitarray
Full text linkIn the recent years the interest for Transmitarrays (TA) antennas increases, since they represents a good solution for obtaining high gain and beam steering, with a configuration that coupled the advantages of lenses and planar arrays. Among the different possible technological solution adopted for the realization of a Transmitarray, a particularly convenient seems to be the one adopting a perforated dielectric layer: the resulting antenna is characterized by ease of manufacturing, that could be done also adopting a 3D additive manufacturing technique, low cost, low profile and low losses. The idea behind the realization of a perforated dielectric TA is that of locally changing the phase of the transmission coefficient properly acting on the size of the hole in the dielectric, through which it is possible to control the effective dielectric constant of the substrate, maintaining the S21 amplitude as much as it is possible close to 1 . Different solutions have been presented in literature, aimed to improve the performances of the transmitting layer, playing with the shape and the number of hole in each unit-cell and/or the number of dielectric layers. In fact it was notice that increasing the number of layers, and especially adding one layer on each side of the transmitting one acting as a sort of matching element between the unit cell of the TA and the air, the antenna performances increase (M.Wang, S. Xu, F. Yang and M. Li, 2016 IEEE Int. Symposium on Antennas and Propag. and URSI/USNC National Radio Science Meeting). Starting from these considerations, here a new type of unit-cell has been introduced: it consist in a three layer structure, where a square hole is drilled in the center of the unit-cell of the middle layer and its size d is used to control the phase of the transmission coefficient, while in the upper and lower layers the hole has a linearly tapered shape. The structure has been designed to work in E-band and the adopted dielectric material has a dielectric constant εr = 6.15. The unit cell has been simulated with CST using the infinite array method. The variation of the amplitude and phase of S21 with d is plotted in Fig.1. These results show that, while the phase variation covers a range even larger than 360°, the amplitude of S21 has minimum variations, confined between -0.7 and -0.2 dB. Results on the design and analysis of an entire TA adopting this type of unit-cell will be provided at the Conference
Analysis of underwater EM propagation for scuba diving communication systems
Full text linkIn this summary, the feasibility of a wireless communication system to be use by scuba divers in case of danger, adopting radio frequency electromagnetic wave technology, is investigated. Some results on the characterizing feature of the propagation inside the water are reported, together with the principal constrains that the environment introduced on the design of the entire system and of its antenna more specificall
Analysis of antennas for underwater applications
No full textUnderwater Communication has a wide range of applications. In the case of a short-range communication system, the use of electromagnetic waves has been recently proposed as an alternative to the mostly used acoustic waves. The design of the antennas to be used for underwater communication is strongly influenced by the electromagnetic properties of the water and therefore, after its design but before its experimental characterization, it is necessary to perform an accurate numerical analysis of its behavior. As a proof-of concept, here the results obtained with the full-wave numerical analysis of antennas designed for an underwater communication system between scuba divers are illustrated, considering two types of realistic water enviroment: seawater and freshwater
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