Inaug.-diss.--Kiel. / Vita.

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 82-84.

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Field restrictions on E- and H-waves are examined for an inhomogeneous isotropic medium. Restrictions on E-and H-waves are, also, discussed for wave-guides of varying cross section, such as for example a circular-section waveguide having an axially dependent radius For an axially symmetric periodic structure with a slowly varying radius, an approximate wave equation is derived which is separable. The field problem is then reduced to finding the solution to Hill's equation. A treatment of electromagnetic waves in media with characteristics possessing finite discontinuities in the direction of propagation is developed. The development avoids the use of explicit boundary conditions. To illustrate the method, three examples are given. This method is extended to include media with characteristics possessing finite discontinuities in, and transverse to, the direction of propagation. Two examples are given. In the first an E-wave solution is found for a cylindrical waveguide loaded periodically with dielectric disc, the disc radius being smaller than the cavity radius. Two methods of solution are offered: one is a first mode approximation and the other is an approximate series solution. A short comparison is made between experimental measurements made on dielectric loaded periodic structures of the forementioned type and theoretical predictions based on the first mode approximation. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The problem of normal-incidence scattering by isotropic cylinders with arbitrary radial permittivity variation and by perfectly conducting cylinders surrounded by radially inhomogeneous isotropic shells is studied. Two types of approximation are considered, namely (i) an approximation of the permittivity variation which allows the use of a power series solution of the wave equation and (ii) approximation of the cylinder by a layered structure. For the latter type, computations are carried out for homogeneous shells and for shells with linearly-varying permittivities. The results are compared with those obtained by numerical integration of the Riccati-type differential equation for impedance or admittance. In general, the homogeneous-shell approximation appears to be easiest to apply and requires a relatively short computation time. It is shown that the scattered-field coefficients can be calculated from measurements of the scattered, field at a single radius by applying a Fourier least-squares fit to the data. The scattered field for plane-wave incidence can therefore be calculated from that for cylindrical-wave incidence, which suggests a more compact system for experimental investigation. Cylinders with a "smoothly" varying permittivity were constructed using a certain type of artificial dielectric. Measurements were carried out in a parallel-plate region for both plane and cylindrical wave incidence; the results obtained agree with computed results and disagree with some previously published theoretical results. As an application, an investigation is made of the range of validity of a planar model when interpreting phase angle measurements on dielectric-enclosed and -unenclosed cylindrical plasmas. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Accurate measurements of the propagation coefficient of the HE₁₁ mode on polythene-tube waveguides in air and surrounded by a polyfoam shield are reported. These were carried out at X-band frequencies using a cavity-resonance method. The results obtained confirm previous theoretical predictions although there is an element of uncertainty concerning the exact dielectric properties of the commercial grade polythene tubes used. The measurements also yielded the phase coefficient of the HE₁₁ mode which was confirmed by measurement of the radial decay of the electric field outside the tube. Enclosing the dielectric-tube in a low-density, low-loss polyfoam shield resulted in only a slight degradation of the attenuation characteristics of the waveguides. Measurements of the phase characteristics of the higher order TE₀₁ and TM₀₁ modes on the tube at frequencies close to cutoff are also reported. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The propagation of the switching surge wave front on multiphase power lines was investigated by modal analysis and conventional Fourier Transformation. A 500 kV untransposed, three-phase transmission line, for which field test results were available, was chosen as a test case. Phase A of this test line was excited from a double exponential voltage source and the voltage response at the receiving end was calculated and measured in all three phases. The calculated voltage arrival time matched closely the measured value, and was very close to the time taken by electromagnetic waves in air at a speed of 0.3 km/μs. The calculated voltage response curves also came close to the measured results (errors within 8%). / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

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