Broadband counter-wound helix antenna for land mine detection

Abstract

Ground penetrating radars (GPRs), also known as subsurface radars, are used in many applications including detection of land mines and unexploded ordnance (UXO). Despite significant long-term investment in GPRs for mine and UXO detection, it remains true that no GPR system that meets operational requirements has yet been fielded; however, recent advances in several mine detection radars under development have produced significant improvements in detection performance and false-alarm mitigation over what was achievable only a few years ago. This research examines the suitability of modeling helical antennas to achieve a broadband characteristic for GPR implementation. Although the two-arm counter-wound helix provides the required spot illumination, it is expected that more arms may have to be added to reduce the radiation in the back direction and to match the input impedance to the feed line. Microwave Design Studio (MDS) has been used extensively to simulate the broadband characteristics of the helical antenna. An overall design strategy is outlined, together with a more detailed treatment of the ground penetrating radar subsystems and topics that are relevant to effective subsurface radar operation. These include soil characterization, the choice of the frequency of operation, as well as the design and construction of suitable helical antennas. Finally, a new antenna structure called the counter-wound quadrifilar helical antenna (CQHA), which is suitable for subsurface radar applications, is examined. The counter-wound quadrifilar helical antenna has a broad bandwidth and a linear polarization with a controllable plane of polarization from a planar geometry.