1,721,233 research outputs found
Fundamental properties of surface waves in lossless stratified structures
No full textThis paper is focused on dispersive properties of lossless planar layered structures with media having positive constitutive parameters (permittivity and permeability), possibly uniaxially anisotropic. Some of these properties have been derived in the past with reference to specific simple layered structures, and are here established with more general proofs, valid for arbitrary layered structures with positive parameters. As a first step, a simple application of the Smith chart to the relevant dispersion equation is used to prove that evanescent (or plasmonic-type) waves cannot be supported by layers with positive parameters. The main part of the paper is then focused on a generalization of a common graphical solution of the dispersion equation, in order to derive some general properties about the behaviour of the wavenumbers of surface waves as a function of frequency. The wavenumbers normalized with respect to frequency are shown to be always increasing with frequency, and at high frequency they tend to the highest refractive index in the layers. Moreover, two surface waves with the same polarization cannot have the same wavenumber at a given frequency. The low-frequency behaviours are also briefly addressed. The results are derived by means of a suitable application of Foster's theorem
Improved acceleration of mixed-potential periodic Green’s functions through the effective-medium concept
No full textNonperiodic excitation of a shielded periodic array of patches
No full textThe nonperiodic excitation of a shielded periodic array of patches is analyzed through the Method of Moments in the Spectral Domain by means of an efficient numerical implementation of the Array Scanning Method
Regolarizzazione e interpolazione delle funzioni di Green ai potenziali misti per l’analisi efficiente di strutture periodiche stampate su substrati dielettrici
No full text
Excitation of a periodic microstrip line through a nonperiodic vertical current
No full textFinalista nella competizione "EuMC Young Engineer Prize
Il metodo dell’array scanning per l’analisi efficiente di microstrisce periodiche eccitate da sorgenti aperiodiche
No full textTecniche di accelerazione per funzioni di Green 3-D in strutture periodiche lungo una o due direzioni
No full textThe problem of accelerating the calculation of the periodic Green's function in free space is addressed here. Periodicity is considered both along one axis and along two, generally skew, axes. A systematic review of the existing methods is first presented, with the aim of characterizing their capability to treat the case of a complex phase shift between unit cells, necessary for the study of complex modes in periodic structures. The case of a 1-D periodic array of dipoles is treated in detail. Comparisons among the various acceleration methods are performed, thus providing fundamental information on their actual numerical efficiency
Efficient near-field interpolation of mixed-potential Green’s functions in layered media
No full textA higher order regularization of the multilayered
mixed-potential Green’s functions, based on enhanced effective-
media extractions, is presented. Singularities in the source
point, both of the Green’s function and of its derivatives up to
the second order, are fully removed. The regular kernel obtained
permits the effective implementation of near-field interpolation
schemes with application to the solution of electromagnetics
problems by the method of moments (MoM)
1-D Periodic Lattice Sums for Complex and Leaky Waves in 2-D Structures Using Higher Order Ewald Formulation
Full text linkA very efficient and accurate method is proposed to evaluate the lattice sums (LSs) for the analysis of leaky waves in 2-D periodic waveguides. The LSs are the series involving Hankel functions of arbitrary order, which are not convergent for complex wavenumbers. It is shown that by extending Ewald representations to higher order Hankel functions, the LSs can be expressed in terms of spatial and spectral series, granting Gaussian convergence even in the case of complex and leaky waves. The method allows for the appropriate choice of the spectral determination for each space harmonic of a given LS coefficient, thus permitting one to obtain modal solutions that may correspond to physical and nonphysical leaky-wave phenomena. First, the proposed LS calculation is exploited in the evaluation of the free-space 1-D periodic Green's function for 2-D structures. Then, the same procedure for the LSs is implemented in a cylindrical harmonic expansion method, based on the transition-matrix and the generalized reflection-matrix approach, for the full-wave analysis of leaky modes in 2-D electromagnetic band-gap waveguides formed by layered arrays of cylindrical inclusions. The presented LS formalism is numerically slim, very fast, and thus well suited for the analysis of a significant class of lossy periodic waveguides and leaky-wave antennas
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