1,721,000 research outputs found
Multi-facet focused microwave antennas
No full textThis paper presents a multi-facet design of an array antenna for near-field focused applications. The cylindrical arrangement of a set of antenna panels (namely, focused linear arrays) will radiate fields focused at the center of the circle formed by the panels. Such an array configuration exhibits superior performance with respect to the conventional planar arrangement, if a symmetric focus region is demanded. Numerical simulations have been performed for arrays thought for RFID (Radio Frequency Identification System) reader antennas at 2.4GHz, as a function of the number of array panels and the focus distance from the antenna surface
An Efficient DFT-UTD Based Evaluation of the Field radiated by Electrically Large Phased Arrays
No full textA Fast Hybrid DFT-MoM for the Analysis of Large Finite Periodic Antenna Arrays on Grounded Substrates
No full textAn efficient DFT-UTD based array synthesis via the successive projection method for contoured beam applications
No full textOn Two Alternative Uniformly Asymptotic Procedures for Analyzing the High-Frequency Diffraction of a Complex Source Beam by a Straight Wedge
Full text linkWhen spectral wave integrals, representing the radiation and diffraction of electromagnetic waves, are characterized by a first-order saddle point and poles in the integrand, they can usually be evaluated, in essentially closed form, at high frequencies by the leading terms of any of the two well-known alternative uniformly asymptotic procedures, namely, the Pauli-Clemmow method (PCM) and the Van der Waerden method (VWM), respectively. The PCM has the advantage that its leading terms directly yield a solution in the simple ray format of the uniform geometrical theory of diffraction (UTD). On the other hand, it is commonly noted that it is not the leading term of the PCM but that of the VWM which remains valid for the case of complex waves. Nevertheless, it is shown here that the PCM can surprisingly work even for some special complex wave cases, only if certain conditions are met. Indeed, it is demonstrated here that the PCM meets these conditions for the special case of the diffraction of a complex source beam (CSB) by a wedge. Also, the PCM directly yields a UTD like solution for this case. The latter result is significant as it provides a strong justification for obtaining a simple UTD type solution for the more general problem of the diffraction of a CSB incident from an arbitrary direction on a wedge with arbitrary curvature, directly via analytic continuation of the corresponding UTD result available for a curved wedge illuminated by a point source in real space. It is also shown that the VWM solution can be trivially cast in the UTD format, by expressing it as a sum of the PCM solution plus a UTD slopelike correction term; a similar result was obtained previously using a higher order term from a generalization of the PCM procedure given elsewhere
Near-field focused antennas: from optics to microwaves
No full textIn this paper, a review on near-field focused (NFF) antennas for short-range wireless links at the microwave frequency band is presented. The basic working principles, the design guidelines, as well as the synthesis procedures suggested for the near-field shaping around the focal point, will be addressed. The review will also span on the different technologies used to implement NFF antennas at the microwave frequency band
Near-Field Focused Subarrays in a Multi-Panel Configuration
Full text linkThis paper investigates the focusing features of a multi-panel near-field focused (NFF) antenna. Differently from conventional NFF planar arrays, the proposed configuration is made of a set of NFF subarrays that are concentrically arranged over a cylindrical boundary. A systematic numerical analysis is performed to show how to control the shape of the -3dB focal spot through the main geometrical and electrical parameters of the proposed antenna layout, such as the number of subarrays, the focal spot location of each subarray and the radius of the cylindrical boundary the subarrays are arranged on. When compared with conventional planar NFF arrays, the additional mechanical complexity is partially balanced by a simpler feeding network design and a more symmetric focal spot. Experimental results are shown for a prototype operating at the 2.4 GHz ISM band
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A hybrid uniform geometrical theory of diffraction – moment method for efficient analysis of electromagnetic radiation/scattering from large finite planar arrays
No full textA hybrid uniform geometricatlh eory of diffraction( UTD)-moment method
(MOM) approach is introduced to provide an efficient analysis of the electromagnetic
radiation/scatteringfr om electricallyl arge, finite, planar periodica rrays. This study is
motivated by the fact that conventional numerical methods become rapidly inefficient and
even intractable for the analysis of electrically large arrays containing many antenna or
frequency-selectivseu rface( FSS) elements.I n the presenth ybrid UTD-MOM approach,
the number of unknowns to be solved is drastically reduced as compared to that which
is required in the conventional MOM approach. This substantial reduction in the MOM
unknownsis essentiallym ade possibleb y introducingr elativelyf ew, specialr ay-type (or
UTD) basisf unctionst o efficientlyd escribeth e unknowna rray currents.T he utility of the
present hybrid approach is demonstrated here for the simple case of a large rectangular
phased array of short and thin metallic dipoles in air, which are excited with a uniform
amplitude and linear phase distribution. Some numerical results are presented to illustrate
the efficiency and accuracy of this hybrid metho
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