Title

Simulation of the scattered EM field of a moving dynamic object using static data

Date of Award

2017

Degree Name

Ph.D. in Electrical and Computer Engineering

Department

Department of Electrical and Computer Engineering

Advisor/Chair

Advisor: Robert Prewitt Penno

Abstract

The effect of the translational motion and rotation of a very good conducting cylinder on the scattered field of a plane wave will be investigated where the incident wave has either polarization (E-wave and H-wave). However, when the object moves towards or away from the source with constant velocity, the frequency of the scattered field is shifted, an effect referred to as the Doppler Effect. When the object has rotation or vibration in addition to translation, it may induce phase modulations of the scattered signal. Such modulation during rotation or vibration has been referred to as micro-Doppler effect (m-D). The scattering of electromagnetic plane waves by a conducting cylinder in uniform rotation was investigated by many researchers in the past using the Galilean transformation. These discussions indicate that the effect of rotation is negligible in the case of a perfectly conducting cylinder of either polarization. Herein, the effect of rotation is not negligible in the case of a very good conducting cylinder as shown when the Franklin transformation is employed. In this dissertation a novel model is developed to simulate rotation and translation using the Franklin and the Lorentz transformation. The Franklin transformation is used instead of the Galilean transformation to analyse the scattering of both polarizations of electromagnetic waves (H-wave and E-wave) by rotating a very good circular conducting cylinder. This analysis shows that the rotation of a very good conducting cylinder is more evident in the case of an incident, time-harmonic plane H-wave (TE-mode). The results indicate that the magnitude and phase of the backscattered field of an H-wave incident upon a rotating, very good conducting cylinder is different from that of a stationary one. The micro-Doppler component of the backscattered fields (due to rotation of very good conducting cylinders) is examined using a high resolution, time-frequency analysis. The spectrogram of the phase of the backscattered field shows that the rotation of a cylinder produces a phase shift of the backscattered field. Also, the Lorentz transformation is used to investigate the effect of translational motion of the conducting cylinder on the scattered field. As expected, these results also demonstrate that the frequency of the backscattered field is shifted when the object moves away or towards the source. First order approximations of the Lorentz transformation and Franklin transformations are applied together; it is seen that both phase and magnitude of the backscattered field are significantly affected, producing additional information about the complex, dynamic scattering body. Finally, the model that is developed is used to simulate translation and rotation using static backscattered field data of an arbitrary object. The simulation using static data compared favorably with the dynamic simulation.

Keywords

Translational motion, Frequencies of oscillating systems, Phase modulation, Electromagnetic waves Scattering, Electromagnetic waves Polarization, Backscattering, Electrical Engineering, scattered fields, rotating, conducting cylinder

Rights Statement

Copyright 2017, author

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