| dc.contributor.author | Feng, Xiaoyao | |
| dc.date.accessioned | 2022-08-22T15:45:47Z | |
| dc.date.available | 2022-08-22T15:45:47Z | |
| dc.identifier.uri | http://hdl.handle.net/10222/81869 | |
| dc.description | Time-reversal (TR) method has been attractive and effective in solving inverse problems due to its relative simplicity. It has been widely researched in acoustics, optics, communications, and electromagnetics. One of its applications is source reconstruction, where the electromagnetic TR method can replace expensive measurements and signal computations. However, much work has been confined to theoretical discussions and numerical simulations; there are still unresolved ambiguities and controversies about the TR method. They restrict further realistic applications of the TR method in the areas such as electromagnetic compatibility (EMC). Therefore, more extensive research on theories, algorithms, simulations and experimentations of the TR method is needed.
In this thesis, we start with the fundamental laws in wave physics and electromagnetics and present a new theoretical perspective of the TR method. We use the finite-difference time-domain (FDTD) method to conduct numerical studies and verifications. The results show that the TR method in a cavity can efficiently locate field concentrations and recover the sources. We discuss the limitations of the conventional TR method and subsequently propose a new adaptive method with the introduction and incorporation of entropy and kurtoses. We apply the newly proposed method to locate sources and compare it with the conventional methods. Numerical examples demonstrate the effectiveness and capabilities of the proposed method in source reconstruction.
Finally, we develop a hardware experiment and validate TR as a robust and straightforward method for source reconstruction. Since the testing equipment has a limited working bandwidth, we propose the processing algorithms to deal with the band-limited testing data. The algorithms can produce causal time-domain signals from the band-limited data that can be used for realistic TR source reconstruction. As a result, the TR method can be applied with practical measurements to recover source excitation time instants and locations. In other words, the methods and techniques proposed in this thesis pave the way for extensions and applications of the TR to complex and realistic problems. | en_US |
| dc.description.abstract | Time-reversal (TR) is an effective method of solving inverse problems. However, the theory about the TR is still not clear. This thesis starts by examining fundamental laws in wave physics and electromagnetics and presents a revisit of the electromagnetic TR method. Then a cavity is employed, and a new adaptive TR method with the introduction and incorporation of entropy and kurtoses is proposed. Finally, hardware experiments are performed to validate the TR as a robust and straightforward method for source reconstruction. Since the testing equipment has a limited working bandwidth, special algorithms are developed to transform the band-limited testing data into causal time-domain signals for the TR operations. The results verify the effectiveness of the TR method in real-world situations. The work presented in this thesis paves the way for extensions and applications of the TR method toward solving complex, realistic problems. | en_US |
| dc.language.iso | en | en_US |
| dc.subject | band-limited signal | en_US |
| dc.subject | cavities | en_US |
| dc.subject | finite-difference time-domain method | en_US |
| dc.subject | source reconstruction | en_US |
| dc.subject | time-reversal method | en_US |
| dc.title | On the Theory and Experiments of Time-Reversal for Source Reconstruction | en_US |
| dc.date.defence | 2022-08-12 | |
| dc.contributor.department | Department of Electrical & Computer Engineering | en_US |
| dc.contributor.degree | Doctor of Philosophy | en_US |
| dc.contributor.external-examiner | Eric William Gill | en_US |
| dc.contributor.graduate-coordinator | Vincent Sieben | en_US |
| dc.contributor.thesis-reader | Sergey Ponomarenko | en_US |
| dc.contributor.thesis-reader | Guy Kember | en_US |
| dc.contributor.thesis-supervisor | Zhizhang David Chen | en_US |
| dc.contributor.ethics-approval | Not Applicable | en_US |
| dc.contributor.manuscripts | Yes | en_US |
| dc.contributor.copyright-release | Not Applicable | en_US |
