Time-Frequency Analysis for Landmine Detection Using Impulse Ground Penetration Radar

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Date

2012-01

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Addis Ababa University

Abstract

Land mine detection is an important and yet challenging problem and one that remains to be solved. Ground Penetrating Radar (GPR) is an effective sensor to detect land mines that are made of plastic or have low metal content. GPR operates by first transmitting an impulse signal down to the mine field, second receives the signals reflected from the different layers of the ground and processes the received image to give a revealing picture of the size and shape of a landmine (metal or plastic) and where exactly it is located. In electromagnetic wave propagation modeling, a multilayer transmission line technique is applied. It considers different soil types and targets of different diameters which are buried at different depths. Signal processing algorithms are implemented for clutter reduction. Preprocessing techniques such as DC Offset removal, Antenna cross talk, Noise Reduction (using weighted moving average and exponential moving average) and Background clutter reduction. GPR signal processing algorithms apply processing in time domain; therefore an advanced signal processing technique which is a 2D (time and frequency) view of a signal is required to see a more revealing picture. After preprocessing steps have been accomplished then further process with advanced signal processing techniques to get a more revealing picture of the energy concentration of the buried target at different time instants. Joint time-frequency transforms were developed for the purpose of characterizing the time-varying frequency content of a signal. The best-known time-frequency representation of a time signal dates back to Gabor and is known as the short-time Fourier transforms (STFT). It is basically a moving window Fourier transforms. By examining the frequency content of the signal as the time window is moved, a 2D time-frequency distribution called the spectrogram is generated. The spectrogram contains information on the frequency content of the signal at different time instances. Considering a real GPR data [1] where target objects and non target objects or clutters which are buried at different positions and after passing through Matlab algorithms, a more revealing picture is created. Keywords; land mine detection, GPR system, demining.

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Keywords

land mine detection, GPR system, Demining

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