With a rapidly decaying infrastructure, the need for improved and more efficientstructural health monitoring and nondestructive evaluation (NDE) only grows with each passing day. Without comprehensive evaluation of structural issues, repairs tend to be temporary and haphazard. The quality of repairs utilizing composite materials cannot be adequately inspected, as there exists a gap within the material coverage in NDE methods caused by the unique anisotropic dielectric characteristics of composite materials. Due to the inherent relationship of dielectric permittivity to electromagnetic theory, and the lack of compact and accurate imaging systems that are not prohibitively expensive for the frequency range (10 KHz to 9 GHz), low frequency capacitive imaging and high frequency microwave imaging have been chosen as the modalities for the system presented in this thesis. First, the governing theory behind low frequency imaging is detailed, with an emphasis on the capacitive imaging for dielectric characterization of composites. A miniaturized low frequency capacitive imaging system is designed to operate at a frequency range from 10 kHz to 200 MHz with a dynamic range of 113 dB. Additionally, high-Q capacitive resonance probes are designed to be used with the miniaturized imaging system and the results are compared with the preexisting table-top system. Second, general electromagnetic theory is explained and a miniaturized near-field microwave imaging system is designed for dielectric evaluation. The microwave system operates from 1 GHz to 9 GHz and has the ability to work with various probes. Third, both low and high frequency systems are integrated together to provide a wideband multi-modality imaging system. The system demonstrates comparatively accurate results for a fraction of the price of existing systems. The compact and practical nature of this system makes it an optimal tool that can be utilized not only in the lab, but implemented in field conditions as well
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