Incremental Theory Of Diffraction Formulation Research Articles

ITD Double-Edge Diffraction for Complex Source Beam Illumination

A new high-frequency incremental theory of diffraction (ITD) formulation for the double diffraction by metallic wedges when illuminated by complex source points (CSP) is provided. The main motivation is the extension of the class of problems that can be studied using asymptotic (i.e., ray-based and incremental) methods by providing a double diffraction description for CSP, which are considered because they are efficient to analyze electrically large structures. The new formulation provides an accurate asymptotic description of the interaction between two edges in an arbitrary configuration, including slope diffraction contributions. Advantages of the ITD formulation for CSP illumination include avoiding the typical ray-caustic impairments of the GTD/UTD ray techniques and not requiring ray tracing in complex space. Numerical results are presented and compared to a Method-of-Moments analysis to demonstrate the accuracy of the solution.

Experimental and Theoretical Validation for the Incremental Theory of Diffraction

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Experimental and theoretical approaches to verify the validity of the incremental theory of diffraction (ITD) are considered. After providing a simple recipe for the application of the ITD, three geometries are examined for its validation. First, the ITD formulation of the diffraction from a perfect electric conductor (PEC) straight wedge is compared with the uniform theory of diffraction (UTD) and with measurement results. Second, the ITD formulation of the diffraction from a PEC disc is compared with measurement results and with the exact solution of a boundary value problem involving oblate spheroidal functions. Third, the ITD formulation of the diffraction from a hole in a PEC plane is compared with the exact solution of a boundary value problem involving oblate spheroidal functions. In particular, this is the first time that ITD results for diffraction from the disc and hole in a plane geometries are validated using exact solutions computed at a caustic. In all cases examined, very good agreement is found. </para>

ITD formulation for the currents on a plane angular sector

Approximate high-frequency expressions for the currents induced on a perfectly conducting plane angular sector are derived on the basis of the incremental theory of diffraction (ITD). These currents are represented in terms of those predicted by physical optics (PO) plus fringe contributions excited by singly and doubly diffracted (DD) rays at the two edges of the angular sector. For each of these two contributions, additional currents associated to vertex diffracted rays are introduced that provide continuity at the relevant shadow boundary lines. The transition region of DD rays is described by a transition function involving cylinder parabolic functions. The asymptotic solution presented is constructed in such a way to satisfy far from the vertex the expected edge singularities, which tend to be the same as those predicted by the exact solution of the half plane. Numerical results are compared with the exact solution of the same problem and with moments method results for scattering from polygonal plates.