Improvement of Probe Response Extraction using Time Domain Gating for Embedded Modulated Scatterer Technique


Health monitoring of cement based and composite infrastructure is an important ongoing global issue. The development of a cost-effective and practical technique by which the rehabilitation needs of such structures could be assessed is of great interest. The embedded modulated scatterer technique (MST) is one such technique that has shown promise for health monitoring purposes. MST is based on illuminating a small dipole antenna (probe), loaded with a PIN diode, with an electromagnetic wave. Modulating the PIN diode (turning it off and on in a controlled manner) results in two separate states of the MST probe. As the diode is modulated, so will the signal that is scattered (reflected) by the probe. Properties of this reflected signal provide information about the material in which the probe is embedded. Other targets in the vicinity of the probe will also contribute to the overall reflected signal. As a result, it is important to be able to discriminate between the probe response and other unwanted, yet present, reflections. Using a swept-frequency measurement process in conjunction with a Fourier transform analysis, the probe response can be individually detected. The challenge then becomes the ability to properly and accurately extract the probe response. This paper presents a technique by which the probe response can be extracted for both states when the MST is applied in an embedded fashion.


Electrical and Computer Engineering

Keywords and Phrases

Embedded Modulated Scatterer Technique (MST); Loaded Dipole; Materials Characterization; Time Domain Gating; Electromagnetic Formulation-Probe Development And Antennas

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Document Type

Article - Journal

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© 2008 American Society for Nondestructive Testing, Inc., All rights reserved.

Publication Date

01 Oct 2008

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