Woojin Lee

Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Electrical Engineering and Computer Science


Sarkar, Tapan K.


Singularity expansion method, SEM, natural poles, time domain

Subject Categories

Electrical and Computer Engineering


A new methodology for detection and identification of unknown objects in free space or on ground, or under the ground is presented in this dissertation. The Singularity Expansion Method (SEM) is introduced because it is possible to find the natural resonant frequencies of a scatterer from the scattered fields and use the resonant frequencies for identification. Many techniques to extract singularities of the EM response of an object are studied and then the Cauchy and the Matrix Pencil (MP) methods are chosen to carry out the processing. In the first part of the dissertation, a methodology for the computation of the natural poles of an object in the frequency domain is presented. The main advantage of this methodology is that there is no need to differentiate between the early time and the late time response of the object as required in the SEM and the Cauchy method can be applied directly to the frequency domain data to extract the SEM poles. Thus, one can generate a library of poles of various objects using the Cauchy method. In the second part of the dissertation, the methodology for detecting and identifying an unknown object in the time domain is also presented. For the simulation model, one transmitter and two receivers (dipole antennas) are utilized to obtain the object response. The received currents of the unknown object are computed by using the deconvolving procedure. The MP method is applied for extracting natural poles of the late time response of the unknown object and the Time-Difference-of-Arrival (TDOA) technique is utilized to obtain the location of the objects. Therefore, by generating the pole library using the frequency domain data and simultaneous use of the actual poles computed using the time domain data, the correlation between the two pole sets obtained using totally different methodologies can provide a robust identification procedure.