1,298 research outputs found
An Expansion Function Suited for Fast Full-Wave Spectral Domain Analysis of Microstrip Discontinuities
No full textTransient emission from microstrip interconnects: Theoretical formulation and CAD modeling
No full textA hybrid technique suitable for the space-time analysis of the transient spurious emission from microstrip interconnects is presented. The proposed technique requires the preliminary evaluation of the surface current excited on the microstrip interconnecting lines by means of a transmission line model accounting for dispersive effects, The radiated field is then computed in the frequency domain by applying the saddle-point asymptotic technique to the integral expression of the electric field involving the dyadic Green's function. The transient signals excited along the interconnects, and the corresponding radiated field, are finally determined by using the IFFT. Radiation mechanisms are investigated, and the influence of the structure's electrical and geometrical parameters is discussed
Analysis of open-ended circular waveguides using physical optics and incomplete Hankel functions formulation
No full textThe spatial distribution of the electromagnetic field excited in semi-infinite open-ended circular waveguides is analyzed using a physical optics (PO) and incomplete Hankel functions formulation. Using the incomplete Hankel functions, the PO surface integral employed to compute the field quantities is reduced to a simple line integral along the waveguide contour. Such a superposition integral, which describes the elementary field contributions having spherical and cylindrical character, is then evaluated in closed analytical form along the waveguide axis. It is shown that cylindrical waves are generated by the surface currents flowing on the waveguide walls, while the spherical waves are produced by the currents and charges excited at the waveguide truncation. Cylindrical and spherical waves are responsible for the field synthesis in terms of waveguided modes and scattered fields at the waveguide mouth. Numerical examples, demonstrating the accuracy of said field representation in the near- and far-field region of truncated circular waveguides, are finally provided
Incomplete Hankel and Modified Bessel Functions: A Class of Special Functions for Electromagnetics
No full textA novel class of special functions for electromagnetics is presented. Formed by the incomplete Hankel and modified Bessel functions, this class allows solving electromagnetics problems concerning truncated cylindrical structures. The differential and recurrence equations of these functions feature additional terms with respect to the classical theory of the Hankel and Bessel functions. The general properties, the most important analytical characteristics, and the large argument asymptotic approximations of the incomplete functions are derived using the steepest descent path (SDP) technique, showing that each special function splits into two terms. The first one has a discontinuous character and is linked to the saddle-point(s) contribution(s), while the second one, arising from the integral end-point contribution(s), compensates exactly the said discontinuity. In the solution of electromagnetic problems, the first term describes the geometrical optics (GO) field, the diffracted field being described by the second one. The general theory is employed to find the closed form analytical solution of the field radiated from a uniform line current source. Using the properties of the incomplete Hankel functions, it is demonstrated that this source excites cylindrical fields having optical character. Finally, the shape of the spatial regions where the GO solution cannot be applied is determined and discussed in details
On the optical behavior of the electromagnetic field excited by a semi-infinite electric traveling-wave current
No full textA closed-form solution for the spatial distribution of the electromagnetic field excited by an electric traveling-wave current source is presented. Incomplete Hankel and modified Bessel functions are employed to represent progressive and evanescent wave fields, respectively. It is shown that these fields are expressed in. terms of spherical and cylindrical waves exhibiting optical character. Using the properties of the incomplete Hankel and modified Bessel functions, the spatial regions where the fields exist in optical sense are determined. It is shown that different shadow boundaries (SBs), featuring complex shapes, identify discontinuity surfaces for the geometrical optics (GO) field. Three surfaces, one being the well-know Keller's cone, are found to describe in the general case the SBs for both the progressive and the evanescent wave fields. It is demonstrated that these surfaces collapse to the Keller's cone surface in the limit of beta -> infinity
Exact closed-form expression of the electromagnetic field excited by pulse-shaped and triangular line currents
No full textThe exact closed-form expression for the electromagnetic field excited by pulse-shaped and triangular line currents is presented. The analytical formulation, based on the incomplete Hankel functions, shows that the field is composed of cylindrical waves excited near the current axis and spherical waves arising from the source critical points. Spherical waves related with pulse-shaped current basis functions are shown to have stronger field singularities than for triangular basis functions because of the impulsive charges present at the current truncations. For triangular line currents, it is further shown that an additional spherical wave arises from the critical point featuring a charge jump discontinuity. Near and high-frequency asymptotic field expressions show explicitly the nature of the field singularities. Using the analytical properties of the incomplete Hankel functions, the Galerkin's impedance matrix coefficients, useful to solve radiation and scattering problems in truncated cylindrical structures using the method of moments, are finally derived in a closed-form. Numerical examples show the accuracy of the proposed field representation
Dyadic Green’s Function for Planar Anisotropic Uniaxial Substrates: Theory and Applications
No full textEstimation of the peak power density in the vicinity of cellular and radio base station antennas
No full textA full-wave radiation model for a class of gridded ground interconnecting structures
No full textA-full-wave model based on the spectral domain approach (SDA) has been developed to predict, under realistic exciting/loading condition, the radiation characteristics of planar interconnecting lines printed on a dielectric slab backed by a gridded ground plane. The radiated held level is computed through an asymptotic evaluation of the corresponding radiation integral. A class of gridded ground interconnecting structures is analyzed and spurious radiation effects due to the finite size of the full/gridded ground are pointed out
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