1,721,112 research outputs found
On Radlow's quarter-plane diffraction solution
No full textIn this paper, we demonstrate that Radlow’s solution to diffraction by the soft quarter
plane is incorrect. We derive an explicit expression for the Wiener-Hopf factorizing
function and verify that a nonvanishing term, which was not accounted for by Radlow,
arises from a correct evaluation of the field on the quarter plane. Consequently, the field
function proposed by Radlow does not satisfy the boundary conditions, and therefore it is
not the correct solution to diffraction by a quarter plane
Adaptive numerical integration algorithms for the evaluation of surface radiation integrals
No full textIn this paper we propose an adaptive integration algorithm, based on asymptotic high-frequency concepts, for the numerical evaluation of surface radiation integrals. It is shown that the numerical evaluation of radiation integrals becomes computationally more efficient by introducing an adaptive sampling. By this approach the number of sampling points is found to be drastically smaller than that resulting from a standard Nyquist sampling rate
An Efficient Ray Tracing Algorithm for Multiple Straight Wedge Diffraction
No full textWe present an efficient algorithm for the tracing of multiply edge diffracted rays. The algorithm assumes a given sequence of infinite edges and complete visibility among them. The ray tracing problem is formulated as the minimization of the ray total path length. Since such a cost function is strictly convex, except for coplanar edges in the plane-wave far-field regime, then the problem admits a unique global minimum and allows the use of a modified Newton search algorithm, which exhibits a very high converging rate.We also propose a convenient starting point to effectively initialize the minimization algorithm. The proposed algorithm is tested by some numerical examples that show its efficiency and effectiveness
RADAR OBSTACLE DETECTOR FOR A RAILWAY CROSSING
No full textA radar obstacle detector for a railway crossing having a radar beam with a reduced horizontal and vertical angles is disclosed. The radar obstacle may comprise a waveguide; a transmitting element for emitting microwaves, the transmitting element being positioned in the waveguide; a horn coupled to the waveguide, the horn having a first aperture; a dielectric insert positioned in the horn; and a plurality of PCB stacks positioned at the first aperture, the PCB stacks being aligned to the plane of the first aperture, each PCB stack comprising a plurality of PCB substrates wherein each PCB substrate has a conductive strip positioned on a planar surface aligned to the plane of the first aperture
Uniform Asymptotic Evaluation of Surface Integrals With Polygonal Integration Domains in Terms of UTD Transition Functions
No full textThe field scattered by a scattering body or by an aperture in the free space (or in an unbounded homogenous medium) can be described in terms of a double integral. In this paper we show how a canonical integral on a polygonal domain, with a constant amplitude function and a quadratic phase variation, can be exactly expressed in terms of special functions, namely Fresnel integrals and generalized Fresnel integrals. This exact reduction represents a paradigm for deriving a new asymptotic evaluation for a more general integral. This new asymptotic uniform integral evaluation is expressed in the format of the uniform geometrical theory of diffraction which is convenient for numerical computations
Truncated Floquet wave full-wave analysis of large phased arrays of open-ended waveguides with a nonuniform amplitude excitation
No full textRecently, an efficient hybrid asymptotic-method of
moments (MoM) approach has been proposed for the analysis of
large periodic planar arrays of elements excited with equal amplitude
and linear phase. The aforementioned method, which is based
on a Floquet wave diffraction representation of the array Green’s
function (AGF), is here extended to treat arrays with tapered amplitude
excitation. To this end, the asymptotic AGF is refined by
introducing additional “slope” diffraction contributions. An appropriate
“fringe” integral equation, solved via a MoM scheme,
provides the effects of array truncation in addition to the infinite
array solution. The dimension of the corresponding linear algebraic
system is independent of the number of elements of the array.
Numerical results are provided to prove the accuracy and the efficiency
of this method with respect to an ordinary element-by-element
MoM
Artificial magnetism and transmission peaks in metamaterials made by pairs of planar conductors
No full text
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