SGER: A New Method for Landmine Detection and Minefield Mapping

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

0225424 Brown This proposal is being submitted under the Small Grants for Exploratory Research (SGER) program and it focuses on answering critical feasibility questions pertaining to a new technique for the detection and location of buried landmines and unexploded ordnance. The subject technique comprises a standoff, ground based, pulsed radar that launches electromagnetic energy into the Norton surface wave mode of propagation. The Norton surface wave travels along the air-ground surface at the speed of light in a vacuum and exponentially decays into the ground due to the losses in the ground. By selecting the frequency properly, sufficient energy will be scattered by the landmine back along the same propagation path and then received by the radar. This energy is usually insufficient to be above the system noise level so return pulse averaging is carried out using coherent techniques. If N return pulses are averaged coherently the signal-to-noise power ratio will increase by a factor of N rendering the signal scattered from the landmine detectable. Location of the mine is achieved by using the pulse width to accomplish resolution in the range coordinate and the radar antenna to achieve resolution in the azimuth angle. In order to achieve area coverage and the best possible angular resolution close to the antenna, it is proposed to simultaneously employ both beam steering and near field focusing techniques. The critical study, to establish feasibility, is the determination of the highest operating frequency for which the Norton surface wave can propagate on the surface and penetrate sufficiently deep to detect antipersonnel and antitank mines. It is also proposed to develop the appropriate radar range equation for the Norton surface wave, investigate techniques for maximizing the coupling of the radar antenna to the Norton surface wave, determine the variation of soil conductivity and the radar cross section values for typical nonferrous landmines, and investigate the maximum range and angle resolution or the acceptable frequencies of operation. Having answered these questions, it should be possible to establish the viability of such a radar subject only to the need to compute the effects of surface roughness and buried debris on the mine scattered signal strength, i.e., the low signal-to-clutter ratio problem.