Abstract
Most Ground Penetrating Radars (GPR) cover a wide frequency range by emitting very short time wavelets. In this work, we study in detail the wavelet emitted by two bowtie GPR antennas with nominal frequencies of 800 MHz and 1 GHz. Knowledge of this emitted wavelet allows us to extract as much information as possible from recorded signals, using advanced processing techniques and computer simulations. Following previously published methodology used by Rial et al. [1], which ensures system stability and reliability in data acquisition, a thorough analysis of the wavelet in both time and frequency domain is performed. Most of tests were carried out with air as propagation medium, allowing a proper analysis of the geometrical attenuation factor. Furthermore, we attempt to determine, for each antenna, a time zero in the records to allow us to correctly assign a position to the reflectors detected by the radar. Obtained results indicate that the time zero is not a constant value for the evaluated antennas, but instead depends on the characteristics of the material in contact with the antenna.
Highlights
The term radar is short for radio detection and ranging
A priori, this signal might be considered a possible approximation of the emitted pulse, but one must take into account both the proximity between the two dipoles and their arrangement inside the antenna [Figure 2(c)]; on the other hand, due to the antenna shielding, it is possible that some internal reflection can reach the receiver almost simultaneously in spite of the absorbent material, substantially varying the characteristics of the signal recorded in comparison with the emitted wavelet
We were able to obtain an approximation of the wavelet emitted by two Ground Penetrating Radars (GPR) groundcoupled shielded antennas of the bowtie type
Summary
The term radar is short for radio detection and ranging. The name reflects the importance placed by the early workers in this field on the need for a device to detect the presence of a target and to measure. The detection of range is still one of the most important functions of modern radars, these devices can extract much more information from a target’s echo signal than its position. In order to make a good interpretation of the GPR data and extract as much information as possible from the signal recorded during processing, a deep knowledge of the type of emission used is important because the characteristics of the detected reflections (length and shape of the reflected pulse, overlapping of constructive or destructive reflections, etc.) and system’s vertical resolution, directly depend on the characteristics of the wavelet emitted by the antennas [6,7]. Yelf [10], a time zero is determined for each antenna in order to improve accuracy in range estimations of the reflectors detected by the radar
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