This thesis contributes to the methods for evaluating the hardware performance of microwave imaging systems. Different aspects of this performance study are systematically described and evaluated through existing and novel performance metrics. The dynamic range of two vector network analyzers and their noise floor are explored. The effects of low noise amplifiers on the dynamic range of the microwave system are also studied. To increase the dynamic range and sensitivity of the system, a new high efficiency ultra wide band TEM horn antenna is introduced. The new antenna significantly blocks the electromagnetic interference from the surrounding medium. The parasitic coupling between the transmitting and receiving antennas has been reduced to a minimum. To estimate the efficiency of the antenna used in tissue imaging more realistically, a measurement based method is also proposed. The method models the two-port network formed by the antennas and the medium between them by signal flow graph. The medium’s electrical properties mimic those of tissue and can vary according to the application. Also, a new performance metric for microwave systems namely, the physical contrast sensitivity is proposed. Methodologies are proposed for its evaluation through measurements and through simulations. This enables the estimation of the smallest detectable target permittivity contrast or size for the system under evaluation. / Thesis / Doctor of Philosophy (PhD)

Small satellites are satellites that weight less than 500 kg. Compared to larger satellites, a small satellite, especially a cube satellite, has limited surface area. The limited surface area casts challenges for allocating essential parts, such as antennas, for the satellite. Therefore, antennas that are conformal to the satellite surface have distinct advantages over other types of antennas that need significant mounting area. One of the very effective conformal antennas is cavity-backed slot antennas that can be integrated around solar cells and do not compete for extra surface area. The previous study performed on cavity-backed slot antennas was mainly a feasibility study and did not address realistic concerns such as effective feeding methods for the antennas. This thesis work is aimed at providing more detailed study on achieving high quality circular polarization (CP) and simplified feed design to initiate effective integration of the antenna with solar panel. In order to accurately characterize an antenna, an effective antenna range in an anechoic chamber is important. Utah State University had an effective near-field range; however, there was not an fully shielded anechoic chamber. As another objective of this thesis work, a state-of-the-art anechoic chamber has been constructed, calibrated, and utilized to measure different antenna parameters. This thesis also shows correct methods to measure important antenna properties such as CP and antenna efficiency.