In order to detect anti-tank mines at standoff distances, we have developed a forward-looking synthetic aperture ground penetrating radar (FLGPR). The system operates over the frequency band 766~MHz to 3.8~GHz. Our FLGPR system uses a Mill's cross transmit-receive array configuration. The receive array contains 46 Archimedean spiral antennas spaced across a 3.43 meter horizontakl aperture. The transmit
aperture can be configured to contain up to 15 transmitters in one
of two vertical configuations. Data is acquired as the system continuously moves forward at a speed of 2 to 8 kph. Synthetic aperture nearfield beamforming, a form of multi-look processing, is used to reduce clutter and produce significantly improved images of buried targets. Testa against actual buried mines on U.S. Army mine lanes indicate that the system can detect buried metallic and plastic anti tank mines. Images and analysis of data including blind test results are presented.
In order to detect buried land mines in clutter, Planning Systems Incorporated has adapted its Ground Penetrating Synthetic Aperture Radar (GPSAR) technology for forward-looking applications. The Forward Looking GPSAR (FLGPSAR), is a wide-band stepped-frequency radar operating over frequencies from 400 MHz to 4 GHz. The FLGPSAR system is based on a modified John Deere E-Gator turf vehicle that is capable of remote control. Custom Archimedean spiral antennas are used to populate the GPSAR array. These antennas are designed and built by PSI and have exceptional broad-band radiation characteristics. The FLGSPAR system has been used to detect plastic and metallic landmines at U.S. Army test facilities and at PSI's engineering center in Long Beach Mississippi. Multi-look SAR processing has been shown to significantly improve the quality of FLGPSAR imagery.
The use of a laser Doppler vibrometer (LDV) to sense the acoustic-to-seismic coupling ratio for buried landmine detection has previously been demonstrated. During these experiments, the LDV is mounted on a fixed platform and the beam moves continuously across the ground. Experiments show that fixed mounted LDV can achieve scanning speeds up to 3.6 km/h for successful detection of buried landmines in outdoor ground. The problems associated with taking a fixed-mount, scanning LDV and transitioning to a mobile system involve such issues as vehicle vibration, additional Doppler bandwidth due to vehicle speed, speckle noise, and sample time vs. spatial averaging. This paper presents the results of field tests with the moving platform on U.S. Army mine lanes showing that many of these issues can be overcome with an appropriately designed moving platform. The testing involved scanning different types of mines at varying depths and different speeds. Different aspects of the experiment are also discussed.
In order to detect buried land mines in clutter, Planning Systems Incorporated has developed a Ground Penetrating Synthetic Aperture Radar (GPSAR) system for the U.S. Army CECOM Night Vision and Electronic Sensors Directorate. The GPSAR system is a wide-band stepped-frequency radar operating over frequencies from 500 MHz to 4 GHz. Our GPSAR uses multiple transmit and receive antennas to acquire data at 58 across-track locations separated by 1.47 inches. Along-track data sampling is provided by the forward motion of the system. Multiple radar channels and high-speed radio frequency switching are used to accelerate the data acquisition process and increase the system's maximum speed of advance. Synthetic aperture, near-field beamforming techniques are used to reduce clutter and enhance the signature of buried objects. While the system is designed for mine detection it is capable of locating deeper objects such as buried utility pipes. Tests conducted in December 2001 at U.S. Army facilities indicate that the system can detect both metallic and plastic landmines at depths up to 6 inches. A description of the PSI GPSAR system and test results are presented.
Data fusion from two separate and orthogonal mine detection sensors developed independently by the University of Mississippi and Planning Systems Inc. has been performed. The University of Mississippi's acoustic/seismic coupling detection is based on the measurement of ground surface vibration velocity by means of acoustic excitation and a laser Doppler vibrometer. Differences in absolute surface vibration velocity, caused by the present of buried mines, are used to infer the presence of buried land mines. Planning Systems Inc. uses ground-penetrating, synthetic- aperture radar to detect subsurface electromagnetic anomalies. Detection with the GPSAR sensor is based on differences in the dielectric constant of the ground medium and that of a buried land mine. The spatial resolutions of the two measurements are similar and the two sensors measure completely different physical properties. Dat form each system are described in detail and independent examples of performance are presented. A common geo-spatial grid is defined for both sensor systems given their respective resolving capability. Methods of simultaneous display are presented and situations in which the two systems are complementary are identified.
In order to detect anti-tank mines in noisy backgrounds, we have developed a ground penetrating SAR. The system operates over the frequency band 500 MHz to 1.8 GHZ. Our GPSAR system uses multiple transmit and receive antennas to acquire stepped-frequency data at 26 cross-track focal locations each separated by 1.38 inches. System motion is used to achieve along track data sampling. Multiple radar channels and high-speed radio frequency switching techniques are used to accelerate the data acquisition process, thereby increasing the system scan rate. Synthetic aperture, nearfield beamforming techniques are used to reduce clutter. The system is optimized for mine detection but is also capable of detecting deeper objects. Test against actual miens on US Army mine lanes indicate that the system can detect both plastic and metallic anti tank mines as well as anti-personnel mines. Images and analysis of data from these test are presented.
In order to separate buried land mines from clutter a multi- channel stepped-frequency ground penetrating radar has been developed. The system operates over the frequency band 800 MHz to 2.0 GHz. The radar incorporates advanced digital signal processing and radio frequency integrated circuit components. It uses an all-digital modulator coupled with a coherent digital quadrature receiver for making precise magnitude and phase measurements. The control interface to the radar consists of an Ethernet TCP/IP link. A parallel bank of transmit-receive antennas is used to achieve cross track sampling. System motion is used to achieve along track data sampling. Synthetic aperture near field beamforming techniques are used to image buried objects. The system is designed to detect shallowly buried metallic and non- metallic mines. A system overview is presented and result from data collection exercises are included. Images and analysis of data from a mine lane is presented.