2,969 research outputs found
Electromagnetic Metamaterials and Metasurfaces: A historical journey
No full textIn this article, we embark on a historical journey through the development of radio-frequency (RF) metamaterials (MTMs) and metasurfaces (MTSs), tracing their evolution from theoretical concepts well before the name was coined. Along the way, we explore key milestones, breakthroughs, and the profound impact of these engineered materials on antennas, microwaves, and beyond
Prof. Leo Felsen Legacy in Electromagnetics
No full textProfessor Leopold B. Felsen had been certainly one of the brightest minds among those who set the foundations of modern Electromagnetism. The breadth and depth of his scientific work on wave phenomena spanning over 50 years from the middle fifties until his death, in 2005 provided impactful contributions in acoustics, electrodynamics, seismology, and mathematical physics. His work elevated concepts in Electromagnetism, introducing ray- wave hybrids, complex source-point descriptions for intricate media, and leaky-wave and hybridized ray-mode descriptions for guided-wave phenomena. A catalyst for systematic knowledge development, Professor Felsen collaborated widely and mentored students globally, playing a pivotal role in shaping wave physics and engineering evolution
Arthur Yaghjian Scientific Contributions in Antennas, High-Frequency Diffraction, and Metamaterials
No full textDr. A. Yaghjian stands out as one of the most innovative, creative, and influential scientists in Electromagnetics (EM). His remarkable qualities stem from his impressive fundamental background in Maxwell's equations and on his unparalleled ability to formulate complex EM problems in a rigorous and impactful manner. Undoubtedly, he is among the few remaining repositories of knowledge in EM theory. This paper undertakes a review of his primary contributions, with special emphasis on Antennas, High-Frequency diffraction, and metamaterial, that have had a profound impact on the EM community
A compact formula for the array factor of planar phased arrays with polygonal shape and skewed grid
No full textIn this paper, we present a compact formula for the computation of the array factor (AF) of uniformly excited planar periodic arrays with an arbitrary polygonal contour and a skewed grid. The formulation is based on a simple decomposition of the array as a superposition of infinite angular-sector arrays, whose far field is evaluated in exact closed form. The final result is an exact representation of the AF in terms of contributions from the vertices of the polygonal rim of the array
Aperture beam expansion by using A spectral 2D-GPOF method
No full textA method is presented for computing aperture-radiated fields in terms of complex-source type beams. These beams are generated in a natural way by expanding the aperture field spectrum in a sum of complex exponentials. The latter are obtained by using the 2D-GPOF method. Inverse transformation in spatial domain leads to an analytical form in terms of complex source points. Fields radiated by apertures obtained via this approach are validated by direct near field integration and compared with those calculated with spectral-based beam expansion which starts from the Hankel spectrum and uses a 1D-GPOF approach
Generation of complex source point expansions from radiation integrals
No full textThis paper discusses methods for expanding fields radiated by arbitrary sources enclosed by a certain minimum sphere in terms of Complex Source Point (CSP) beams. Two different approaches are reviewed; the first one is based on a spectral radiation integral, where the Fourier-spectrum is obtained by far field matching. The second approach consists of two steps: first, the equivalence principle is applied to a sphere enclosing the real sources, and a continuous equivalent electric current distribution is obtained in terms of spherical waves; then, the continuous current is extended to complex space and its SW components are properly filtered and sampled to generate the discrete set of CSPs. In both cases, the final result is a compact finite series representation with a number of terms that matches the degrees of freedom of arbitrary radiated fields; it is particularly efficient when the fields are highly directional and the observation domain is limited to a given angular sector. The fact that the CSPs rigorously respect Maxwell's equations ensures the validity of the expansion from near to far zone and allows one to incorporate the CSP representation in a generalized admittance matrix formalism for the analysis of complex problems
Composition, structural characteristics and temporal patterns of fish assemblages in non-tidal Mediterranean lagoons: a case study.
No full textModulated Metasurfaces for Microwave Field Manipulation: Models, Applications, and Design Procedures
No full textMetasurfaces (MTSs) have emerged in the last years as a promising platform for next generation planar devices in a broad range of frequencies, thanks to their unique field manipulation capability. In particular, in the microwave range this solution is characterized by low-cost, lightweight, and simple integration with electronic circuits, since MTSs can be realized in PCB technology by printing electrically small patches over a dielectric slab. The MTS behavior can then be conveniently described in terms of homogenized boundary conditions of impedance type. Spatial modulation of these boundary conditions allows one to implement a broad class of functionalities, involving space wave or surface wave control, as well as conversion from surface waves to leaky waves. This paper reviews numerical and analytical models, design procedures and microwave applications of modulated MTSs, with particular emphasis on surface wave manipulation, and it discusses expected future developments of this technology
High-frequency analysis of integrated dielectric lens antennas
No full textA high-frequency method for the three-dimensional analysis of integrated dielectric lens antennas is presented. This method consists on improving the physical optics (PO) currents on the lens surface by modifying, via suitable transition functions, the spreading factor of those rays from the source point which arrive at the lens-air interface close to the critical angle of incidence. In- voking the locality principle of the high-frequency phenomena, the method uses the rigorous canonical solution of the semi-infinite di- electric space locally tangent at the lens surface. A uniform asymp- totic evaluation of this canonical solution is provided with the intro- duction of a new transition function for the TM case. The present formulation provides significant correction from the PO currents of an elliptical lens, with a consequent improvement of the radia- tion pattern prediction, testified by comparisons with results from a full-wave analysis
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