Transient Scattering from Bodies of Revolution with Applications in Short-Pulse Reflector Antennas
This dissertation studies the transient scattering from bodies of revolution (BOR). The work presents two distinct integral formulations for analyzing a wide variety of BOR configurations, numerous scattering examples to better understand the transient scattering phenomena, and two reflector antennas geometries suitable for ultra-wideband radar applications. The March-on-Time (MOT) method and an Inverse Discrete Fourier Transform (IDFT) method are both examined and fully developed to determine their capabilities in analyzing a wide variety of BOR configurations. The IDFT approach is ultimately selected over the MOT for our particular applications. This method transforms the transient scattering problem into the frequency domain where a Moment Method formulation with entire-domain basis functions then determines the equivalent surface currents induced on the scatterer. Once the electromagnetic field radiated by these currents are computed in the frequency domain, they are returned back to the time domain using Fast-Fourier Transform (FFT) techniques. The IDFT analysis technique is used to examine the transient scattering behavior of representative scatterers. Many scatterer geometries are considered, among them perfect conductors, dielectric bodies, dielectric-coated conductors, and multi-body scatterers. The edge diffraction behavior of perfectly conducting scatterers, as well as the scattering characteristics of dielectric spheres made of different dielectric constants and lossy materials, are also studied. Other examples considered are metal scatterers coated with a layer of lossy dispersive material. The last part of this work pertains to the design of reflector antennas for short-pulse radiation. Its main objective is to present representative single- and dual -reflector antennas capable of radiating a collimated user -specified short pulse in the far-zone region. The double -Gaussian time pulse serves as the desired radiated waveform in this section of the dissertation. Two distinct antenna geometries are proposed, one based on the usual time-differentiating behavior of focus-fed paraboloids, and the other on the quasi-non-differentiating behavior of dual-reflectors with ring caustics.
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- Engineering: Electronics and Electrical; Physics: Radiation