| The advancement of electromagnetic engineering has been driving the need to develop efficient techniques for the transient analysis of transmission, propagation and reception of electromagnetic waves in different media. This thesis addresses a new method based on the numerical inversion of Laplace transform (NILT), which overcomes the restrictions in previous approaches, leads to good accuracy in both late and early time, and has simple algorithms, short calculation time and small required memory sizes. To our knowledge, this would be the first time that systematically treats the theory of NILT and its application in the transient analysis of electromagnetic waves. In this thesis, firstly a literature survey is carried out and the weaknesses and limitations of some current time domain techniques are identified. Then Hosono's algorithm for the NILT is treated and developed under a strict theoretical framework. Next, this new technique based on NILT is employed to model the transient reflection of horizontally and vertically polarized waves from a conductive interface with exponentially decaying incident signals. After that, this technique is combined with Prony's method and applied to modeling the transient reflection from a conductive interface and propagation through a lossy dielectric slab with an arbitrary incident signal for both polarizations. Furthermore, this technique is used for the transient analysis of exponentially decaying pulses propagating in plasma with a zero and nonzero electron collision frequency for both polarizations. The technique is extended and applied to the transient anlysis of horizontally and vertically polarized waves reflected from Lorentz, Debye and Cole--Cole half spaces with an arbitrary incident pulse, using the convolution of a time domain reflection coefficients and an incident signal. Finally, based on the transient anlysis of pulses reflected from a dispersive medium half space, the relationships between the waveform parameters of reflected pulses and the properties of dispersive materials as well as the incident angles are discussed, and the application of these results to material characterization and diagnosis is explored. This thesis highlights how to overcome the restriction that numerical inversion of Laplace transform has high demands on image functions, and places the emphasis on how to extend and apply this method to a variety of cases. The correctness and effectiveness of this thesis work are validated through the comparisons between our results and those published in the literature. Meanwhile, the results that cannot be achieved with the previous approaches are also provided. Moreover, this thesis presents some applications of the new technique in diverse engineering fields, including ultra wideband technology and material science. |
