Numerical analysis of electromagnetic field for a class of composite cylinders.

摘要

In this dissertation, an attempt is made to solve two sets of electromagnetic problems. These problems are related in that they all involve composite cylinders.;The first set of problems involves the scattering of an electromagnetic field from a class of circular composite cylinders which are excited by line source or plane wave for TE and TM polarizations. In each problem, the composite circular cylinder consists partially of perfect conductor and partially of dielectric material. The solution technique involves the field equivalence principle, which divides the problem into interior and exterior problems. Galerkin's method is applied to determine the unknown equivalent magnetic current on the dielectric interface. The far-scattered field and the radar cross-section of the composite cylinders are computed in terms of the unknown equivalent magnetic current for both polarizations.;It has been demonstrated that the radar cross section of the scattering problems is reduced by increasing the dielectric constant of the dielectric cylinders. The accuracy of solution is verified for narrow slot and infinite conducting plane. The good agreement between the results shows the accuracy of the solution technique.;The second set of problems involves computation of the quasi-TEM characteristics of cylindrically coupled microstrip lines. Each problem consists of a dielectric substrate cylinder loaded by a conducting wedge. The problem is analyzed by a exact series representation of the potential distribution in each region involved. Applying boundary condition and accounting for the jump discontinuity on the normal derivative of the potential across the dielectric interface provide a set of equations. By applying Galerkin's method, a system of equations is obtained to determine the unknown expansion coefficients. Expressions for the charge distribution on the strips, the capacitance matrix of microstrip line, and effective dielectric constant are obtained in terms of the coefficients.;It has been shown that the effective dielectric constant for the microstrip lines is a linear function of the substrate's dielectric constant. The accuracy of solution is proved by applying the analytical technique for microstrip line with one strip.