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Sensors 2018, 18(6), 1912; https://doi.org/10.3390/s18061912

Microwave Metamaterial Absorber for Non-Destructive Sensing Applications of Grain

1
Collaborative Innovation Center for Modern Grain Circulation and Safety, School of Information Engineering, Nanjing University of Finance and Economics, Nanjing 210046, China
2
Department of Electronic Engineering, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
*
Author to whom correspondence should be addressed.
Received: 3 May 2018 / Revised: 1 June 2018 / Accepted: 10 June 2018 / Published: 12 June 2018
(This article belongs to the Special Issue Antenna Technologies for Microwave Sensors)
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Abstract

In this work, we propose a metamaterial absorber at microwave frequencies with significant sensitivity and non-destructive sensing capability for grain samples. This absorber is composed of cross-resonators periodically arranged on an ultrathin substrate, a sensing layer filled with grain samples, and a metal ground. The cross-resonator array is fabricated using the printed circuit board process on an FR-4 board. The performance of the proposed metamaterial is demonstrated with both full-wave simulation and measurement results, and the working mechanism is revealed through multi-reflection interference theory. It can serve as a non-contact sensor for food quality control such as adulteration, variety, etc. by detecting shifts in the resonant frequencies. As a direct application, it is shown that the resonant frequency displays a significant blue shift from 7.11 GHz to 7.52 GHz when the mass fraction of stale rice in the mixture of fresh and stale rice is changed from 0% to 100%. In addition, the absorber shows a distinct difference in the resonant absorption frequency for different varieties of grain, which also makes it a candidate for a grain classification sensor. The presented scheme could open up opportunities for microwave metamaterial absorbers to be applied as efficient sensors in the non-destructive evaluation of agricultural and food product quality. View Full-Text
Keywords: metamaterial absorber; resonant frequency; sensing; effective permittivity; grain; non-destructive evaluation metamaterial absorber; resonant frequency; sensing; effective permittivity; grain; non-destructive evaluation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Zhang, Y.; Zhao, J.; Cao, J.; Mao, B. Microwave Metamaterial Absorber for Non-Destructive Sensing Applications of Grain. Sensors 2018, 18, 1912.

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