| Summary: | This thesis studies the role of antennas in the achievable resolution and accuracy from nearfield
microwave tomography (MWT). Near-field MWT is an emerging imaging modality in
which the object being imaged is successively irradiated by several antennas, located close
to the object, in the microwave frequency range. The scattered fields emanating from the
object are then processed to form quantitative images from the dielectric properties of the
object.
This thesis starts with proposing a mathematical framework to study the achievable resolution
from MWT. Within this framework, the effect of the near-field distribution of the
utilized antennas on the achievable image resolution will be studied. Specifically, it will be
shown that the use a focused near-field distribution to irradiate the object can enhance the
achievable resolution. Within the same framework, the effects of the frequency of operation,
multiple frequencies of operation, signal-to-noise ratio of the measured data, and the number
of antenna elements on the achievable resolution and accuracy will be studied.
After establishing the importance of the antenna’s incident field distribution, this thesis continues
with investigating two different methods to achieve a focused near-field distribution.
The first method, which attempts to synthesize focused beams from existing omnidirectional
antenna elements, will be shown to be not successful using the method employed in this thesis.
The second method is based on modifying an existing antenna element so as to make its
near-field distribution more focused. Through different experiments and simulations, it will
be shown that the second method can make the near-field distribution of the antenna more
focused while maintaining multiple frequencies of operation for the antenna, and keeping its
physical size reasonably small.
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