Design and Analysis of an Array of Square Microstrip Patches for Nondestructive Measurement of Inner Material Properties of Various Structures Using Swept Microwave Frequencies
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Begun in 1973, the Review of Progress in Quantitative Nondestructive Evaluation (QNDE) is the premier international NDE meeting designed to provide an interface between research and early engineering through the presentation of current ideas and results focused on facilitating a rapid transfer to engineering development.
This site provides free, public access to papers presented at the annual QNDE conference between 1983 and 1999, and abstracts for papers presented at the conference since 2001.
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Abstract
There are several microwave techniques and probes available for characterizing inner properties of materials [1]. Microstrip patches operating in cavity modes are well suited for determining the dielectric properties of materials. A microstrip patch can be characterized by its resonant frequency and quality factor (Q-factor) when operating in free-space. When the patch is covered by another material whose dielectric properties (real and imaginary parts) are different than that of free-space, resonant frequency and Q-factor of the patch will change. The changes in these two parameters are then related to the real and imaginary parts of the material permittivity. Subsequently, the permittivity of the material is related to its moisture content, density, temperature, grain size, etc. via available dielectric mixing models [2]. Such a device can be placed inside a material temporarily (snow pack for avalanche prediction) or permanently (concrete structures for water content and crack detection).