Radio Frequency Interference Suppression for Landmine Detection by Quadrupole Resonance
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Radio Frequency Interference Suppression for Landmine Detection by Quadrupole Resonance Guoqing Liu, Yi Jiang, Hong Xiong, Jian Li, and Geoffrey A. Barrall Department of Electrical and Computer Engineering, University of Florida, P.O. Box 116130, Gainesville, FL 32611-6130, USA Received 24 August 2004; Revised 26 June 2005; Accepted 30 June 2005 The quadrupole resonance (QR) technology can be used as a confirming sensor for buried plastic landmine detection by detecting the explosives within the mine. We focus herein on the detection of TNT mines via the QR sensor. Since the frequency of the QR signal is located within the AM radio frequency band, the QR signal can be corrupted by strong radio frequency interferences (RFIs). Hence to detect the very weak QR signal, RFI mitigation is essential. Reference antennas, which receive RFIs only, can be used together with the main antenna, which receives both the QR signal and the RFIs, for RFI mitigation. The RFIs are usually colored both spatially and temporally, and hence exploiting only the spatial diversity of the antenna array may not give the best performance. We exploit herein both the spatial and temporal correlations of the RFIs to improve the TNT detection performance. Copyright © 2006 Hindawi Publishing Corporation. All rights reserved.
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INTRODUCTION
The quadrupole resonance (QR) technology has been receiving increasing attention for explosive detection in applications including landmine detection [1–4]. It can be used as a confirming sensor for buried plastic landmine detection by detecting the explosives (e.g., trinitrotoluene (TNT) and Royal Demolition eXplosive (RDX)) within the mine. In this paper, we focus on the detection of TNT via the QR sensor. When the 14 N in the TNT is excited by a sequence of pulses, it will emit a signal consisting of a sequence of echoes [1, 5]. This signal has a unique frequency signature specific to the TNT and is referred to as the TNT QR signal. The waveform of the QR signal is known a priori to within a multiplicative constant [5]. Since the TNT QR signal frequency (around 842 KHz [1]) is located within the amplitude modulation (AM) radio frequency band and cannot be changed by other means, the AM radio signals can appear as strong radio frequency interferences (RFIs) that can seriously degrade the QR signal detection performance in a mine field. Hence to detect the very weak QR signal, the RFI mitigation is essential. Reference antennas, which receive RFIs only, can be used together with the main antenna, which receives both the QR signal and the RFIs, for RFI mitigation. By taking advantage of the spatial correlation of the RFIs received by the antenna array, the RFIs can be reduced significantly. However, the RFIs are usually colored both spatially and temporally, and hence exploiting only the spatial diversity of the antenna array may not give the best performance.
We exploit herein both the spatial and temporal correlations of the RFIs to improve the TNT detection performance. First, we consider exploiting the spati
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