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Accurate Permittivity Measurements for Microwave Imaging via Ultra-Wideband Removal of Spurious Reflectors
United States Department of Agriculture, Agricultural Research Services, Lubbock TX, 79403 USA
Sensors Group Microsemi Corp. Lowell MA, 01851 USA
* Author to whom correspondence should be addressed.
Received: 5 August 2010; in revised form: 31 August 2010 / Accepted: 1 September 2010 / Published: 10 September 2010
Abstract: The use of microwave imaging is becoming more prevalent for detection of interior hidden defects in manufactured and packaged materials. In applications for detection of hidden moisture, microwave tomography can be used to image the material and then perform an inverse calculation to derive an estimate of the variability of the hidden material, such internal moisture, thereby alerting personnel to damaging levels of the hidden moisture before material degradation occurs. One impediment to this type of imaging occurs with nearby objects create strong reflections that create destructive and constructive interference, at the receiver, as the material is conveyed past the imaging antenna array. In an effort to remove the influence of the reflectors, such as metal bale ties, research was conducted to develop an algorithm for removal of the influence of the local proximity reflectors from the microwave images. This research effort produced a technique, based upon the use of ultra-wideband signals, for the removal of spurious reflections created by local proximity reflectors. This improvement enables accurate microwave measurements of moisture in such products as cotton bales, as well as other physical properties such as density or material composition. The proposed algorithm was shown to reduce errors by a 4:1 ratio and is an enabling technology for imaging applications in the presence of metal bale ties.
Keywords: ultra-wideband; uwb; microwave imaging; permittivity; moisture sensing; hidden object detection
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Pelletier, M.G.; Viera, J.A.; Wanjura, J.; Holt, G. Accurate Permittivity Measurements for Microwave Imaging via Ultra-Wideband Removal of Spurious Reflectors. Sensors 2010, 10, 8491-8503.
Pelletier MG, Viera JA, Wanjura J, Holt G. Accurate Permittivity Measurements for Microwave Imaging via Ultra-Wideband Removal of Spurious Reflectors. Sensors. 2010; 10(9):8491-8503.
Pelletier, Mathew G.; Viera, Joseph A.; Wanjura, John; Holt, Greg. 2010. "Accurate Permittivity Measurements for Microwave Imaging via Ultra-Wideband Removal of Spurious Reflectors." Sensors 10, no. 9: 8491-8503.