Impulse radiating antennas for mine detection

Abstract

We consider here a selection of Impulse Radiating Antennas (IRAs) that may find use in mine detection. Such devices generally consist of a paraboloidal reflector and a broadband feed. This configuration generally allows the radiation of a clean impulse with approximately two decades of bandwidth, when driven by a step-function source. In certain systems, IRAs may prove to be preferable to other antennas that might be used in mine detection. IRAs radiate a focused plane-wave onto the target, in both the near and far fields. Because the radiation pattern is focused, clutter in the received signal may be reduced. In addition, a focused beam may allow a better look-ahead capability. Two designs in particular will be explored, with either a solid reflector and a collapsible reflector fabricated from a conducting mesh. We provide extensive data on both designs with respect to gain, impulse response, beamwidth, and crosspol performance. We also provide detailed comparisons of IRAs, with two different feed arm locations, +/- 45 degrees, and +/- 30 degrees to the dominant polarization. For IRAs with either collapsible reflectors or solid reflectors, we demonstrate improved performance when the feed arms are posited at +/- 30 degrees to the dominant polarization. In both cases, optimization of the feed arm geometry improved both the gain and the crosspol rejection of the antennas. A mild side effect was a slight increase in TDR reflections at the end of the feed arms.