A uniform geometrical theory of diffraction for an edge in a perfectly conducting surface

Abstract

the integration end-points are determined by the condition z s = 0 and described by the unit step function in (5). It is worth noting that for large apertures in terms of a wavelength, F po (` 0) is a rapidly oscillating function of`0of`of`0. Consequently, the integration in (3) can be asymptotically evaluated by its stationary phase point contributions, thus, leading to a UTD-type ray-field representation. However, this latter fails in describing the field close to and at the axial caustic and it has also been found less accurate with respect to the present numerical line integration for moderate sized apertures. II. NUMERICAL RESULTS Numerical results from AI (continuous line) have been compared with those from LI (dashed line) for the case of a circular OEW with radius a. In particular, Fig. 2(a) shows results for a waveguide with radius a = 0:5, excited by the TE 11 mode. The component of the electric field in the H plane is plotted at a distance r = 1:5 and r = 0:7, respectively. Both curves are normalized with respect to the maximum value obtained in the case r = 0:7; furthermore, the field is calculated in the region external to the waveguide; i.e., < 130 for r = 0:7 and < 160 for r = 1:5. Normalized near field patterns for TM 11-mode excitation are presented in Fig. 2(b). The component of the electric field in the H plane is plotted for the two cases a = 0:65, r = 1:5, and a = , r = 2, respectively. The curves corresponding to this latter case are shifted 10 dB down to render the figure more readable. In spite of the moderate size of the apertures, the agreement between the AI and its corresponding LI has been found quite satisfactory over the total 40-dB dynamic range. The small glitches arise from the fact that the IGCO integration has been turned off when L does not intersect the edge [see Fig. 1(c)]. The result presented here also suggests an effective method to speed-up practical calculations of the interaction between modes [6]. REFERENCES [1] P. Ya. Ufimtsev, "Elementary edge waves and the physical theory of diffraction,"] S. Maci, P. Ufimtsev, and R. Tiberio "Equivalence between physical optics and aperture integration for an open-ended waveguide" IEEE Abstract-A double line integral representation of the mutual coupling between open-ended waveguides of arbitrary cross section is presented, which is useful to speed up calculations inside the framework of a Galerkin method of moments.

An Approximate Utd Ray Solution for the Radiation and Scattering by Antennas Near a Junction Between Two Different Thin Planar Material Slab on Ground Plane

“…is the well-known UTD edge transition functions defined in [1]. The Γ n e,h = ∓1 because the nface is PEC.…”

“…A new, approximate, UTD [1,2] based ray solutions are developed for describing the high frequency EM wave radiation/coupling mechanisms for antennas on or near a junction between two different thin planar slabs on ground plane.…”

An Efficient Method for Computing Highly Oscillatory Physical Optics Integral

“…Traditional asymptotic expansion approximations [3,18,[38][39][40][41][42][43] are widely used in computational electromagnetics, optics, acoustics and geophysics areas. The asymptotic expansion approximation for the highly oscillatory PO integral [10,[17][18][19]] is a frequencyindependent approach.…”

Hybridization of Simulation Codes Based on Numerical High and Low Frequency Techniques for the Efficient Antenna Design in the Presence of Electrically Large and Complex Structures

“…Specifically, low frequency (LF) techniques such as finite element method (FEM) [4], finite difference time domain (FDTD) [5] and method of moment (MoM) [6] have been shown suitable to analyze the small scale interactions within the antenna structure, but are not effective to analyze the large scale propagation problems due to the limitation of computational power. On the other hand, however, high frequency (HF) techniques [7][8][9] such as uniform geometrical theory of diffraction (UTD) [7], physical-optics method [10,11], other diffraction or scattering methods [12][13][14][15][16] are capable of analyzing large scale propagation problems in the presence of electrically large and complex structures by using ray tracing techniques, but are not capable of analyzing the small scale interactions within the antenna because of the difficult ray tracing to achieve accurate results. Thus an effective approach to hybridize the high and low frequency techniques and create an useful tool may significantly assist the engineers to resolve this design problem.…”