Methods for Performance Evaluation of the Acquisition Hardware for Microwave Imaging

Abstract

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.