Extended boundary condition integral equations for perfectly conducting and dielectric bodies: Formulation and uniqueness

The equivalence theorem is used to derive novel generalized boundary condition (GBC) integral equations for the tangential components of the electric and magnetic fields on the interfaces of a finite number of dielectric or conducting scatterers. Closed surface, plane, and line extended boundary conditions (EBC) equivalent to the GBC are introduced. The GBC integral equations can now be replaced by any of these EBC integral equations whose solutions are unique and easy to obtain numerically using the moment method. A perfectly conducting sphere and a dielectric sphere in the electrostatic field of two equal and opposite point charges are presented as simple examples of the general procedure.     

Hemispherically capped thick cylindrical monopole with a conical feed section

The axis boundary condition scalar potential integral equation is used to study the hemispherically capped thick cylindrical monopole with a conical feed section. The monopole is perfectly conducting and is fed by a coaxial line whose outer radius is connected to an infinite perfectly conducting ground plane. One approximation in the equation is that the field across the coaxial aperture is approximated by the fundamental TEM coaxial line mode. The integral equation is numerically solved by the moments method using entire domain basis functions with delta weights. A simple way for checking the convergence of the solution that needs no new integrations is given. The theoretical current distributions, input admittances, and radiation patterns are given for a thin, moderately thick, and thick monopole with and without a conical feed section. This feeding section simplifies the matching of the antenna to conventional signal generators and improves the high frequency characteristics of the monopole.     

Steady-State Analysis of Static Power Converters

Steady-state analysis of static power converters using thyristors and linear circuit elements is formulated using state space method. The circuit goes into n modes and has different describing matrices for each mode. Steady-state condition is obtained in terms of these matrices and the firing and extinction angles. A Newton-Raphson algorithm is given as an interactive method for obtaining the steady-state solution. Closed form expressions are given for the derivative matrix D used in the algorithm. These expressions take into account the variation of the extinction angles during transient as is the case with naturally commutated thyristors. Three alternatives are discussed for the computation of the matrix D. The first method uses the exact expressions whereas the second method uses an approximate expression that neglects the variation of the extinction angles during transient. The third method uses numerical differentiation. Results are then given for an ac-ac and an ac-dc converters. A comparison is made with contraction mapping where it is shown that a remarkable reduction in computation time is achieved especially for lightly damped loads.     

Transient response of thick axially symmetric monopoles

The steady-state results for thick hemispherically capped monopoles with or without conical feed sections are used to construct the transient response of such monopoles. For a voltage pulse excitation, file transient waveforms for the transmitted-reflected feed currents, the radiated fields in different directions, and the instantaneous currents on the monopoles are calculated and presented. Steady-state results are obtained by solving the scalar potential integral equation with the axis extended boundary condition using the moment method.     

Transient response of the duoconical monopole

Large area radiators such as the duoconical monopole are less frequency sensitive than thin antennas. The dispersive nature of antennas is important especially when they are used to transmit video pulses. This paper presents the numerical results obtained for the duoconical monopole under pulsed excitation. Results include the current distribution on the monopole at different instants of time, the radiated waveforms in different directions, and the waveforms of transmitted and reflected signals on the feeding coaxial line. Numerical results were obtained by applying the inverse Fourier transform to the steady-state time harmonic current distributions and radiation patterns. The above results are then used to find a simple incident voltage waveform that will radiate a "pulse" of "good" shape. The radiated field in different directions are then presented for different parameters of the incident double exponential voltage waveform.