• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.2
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• pp.204-212
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• 2015

Harmonic effects in a wideband stepped frequency radar(650 MHz~4.5 GHz) have been analyzed. As a result of numerical analysis and simulation, when the second harmonic exists in each frequency, a time-domain result represents an additional object which does not exist but looks to be located at a distance of twice the original object distance. The second harmonics can be removed effectively by low pass filters because there are no other signals between DC and a fundamental signal. In this paper, the harmonic problem can be solved by removing the second harmonics of 650 MHz to 4.5 GHz wideband fundamental signal with two switches and four low pass filters.

• Geophysics and Geophysical Exploration
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• v.8 no.4
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• pp.270-279
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• 2005

Under the research project supported by Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), we have conducted the development of GPR systems for landmine detection. Until 2005, we have finished development of two prototype GPR systems, namely ALIS (Advanced Landmine Imaging System) and SAR-GPR (Synthetic Aperture Radar-Ground Penetrating Radar). ALIS is a novel landmine detection sensor system combined with a metal detector and GPR. This is a hand-held equipment, which has a sensor position tracking system, and can visualize the sensor output in real time. In order to achieve the sensor tracking system, ALIS needs only one CCD camera attached on the sensor handle. The CCD image is superimposed with the GPR and metal detector signal, and the detection and identification of buried targets is quite easy and reliable. Field evaluation test of ALIS was conducted in December 2004 in Afghanistan, and we demonstrated that it can detect buried antipersonnel landmines, and can also discriminate metal fragments from landmines. SAR-GPR (Synthetic Aperture Radar-Ground Penetrating Radar) is a machine mounted sensor system composed of B GPR and a metal detector. The GPR employs an array antenna for advanced signal processing for better subsurface imaging. SAR-GPR combined with synthetic aperture radar algorithm, can suppress clutter and can image buried objects in strongly inhomogeneous material. SAR-GPR is a stepped frequency radar system, whose RF component is a newly developed compact vector network analyzers. The size of the system is 30cm x 30cm x 30 cm, composed from six Vivaldi antennas and three vector network analyzers. The weight of the system is 17 kg, and it can be mounted on a robotic arm on a small unmanned vehicle. The field test of this system was carried out in March 2005 in Japan.

• Ocean Systems Engineering
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• v.13 no.2
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• pp.195-224
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• 2023

This paper proposes a method for the acoustic imaging wherein the traditional requirement of the relative movement between the transmitter and target is overcome. This is facilitated through the beamforming acoustic array in the transmitter, in which the target is illuminated by the array at various azimuth and elevation angles without the physical movement of the acoustic array. The concept of beam steering of the acoustic array facilitates the formation of the beam at desired angular positions of azimuth and elevation angles. This paper substantiates that the combination of illumination of the target from different azimuth and elevation angles with respect to the transmitter (through the beam steering of beam forming acoustic array) and the beam steering at multiple frequencies (through SF) results in enhanced reconstruction of images of the target in the underwater scenario. This paper also demonstrates the possibility of reconstruction of the image of a target in underwater without invoking the traditional algorithms of Digital Image Processing (DIP). This paper comprehensively and succinctly presents all the empirical formulae required for modelling the acoustic medium and the target to facilitate the reader with a comprehensive summary document incorporating the various parameters of multi-disciplinary nature.

• Geophysics and Geophysical Exploration
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• v.5 no.4
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• pp.272-279
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• 2002

During field survey of ground penetrating radar or borehole radar, we often encounter some problems which could be solved easily by modifying structure of the system such as antenna length, shape or array. In addition, it is necessary that the user could easily modify configuration of the radar system na test various array of antennas in order to verify and confirm numerical modeling results concerning radar antennas. We have developed network-analyzer-based, stepped-frequency georadar system. This system had been comprised with coaxial cable to confirm possibility of the system, then we have upgraded the system to use optical cable that is composed of optical/electric transducers, electric/optical transducers, amp, pre-amp and antennas. The software for the aquisition of data has been developed to control the system automatically using PC with GPIB communication and to display the obtained data graphically. We have tested the system in field survey na the results have been compared with those of RAMAC/GPR system.