Radiation characteristics of small antennas on small UAV platforms

There is an increasing interest in direction finding (DF) systems operating at VHF low-frequency ranges (30-90 MHz) and at high depression angles for small unmanned airborne vehicle (UAV) platforms. Conventional half-wave dipoles and loops are too large to be aerodynamically compliant on a small UAV. Since the platform dimension is of the order of a wavelength of the electromagnetic waves, the radiation characteristics of the antenna systems (small antenna/small platform) exhibit greater complexity than those of the freespace counterparts. The paper describes a robust and practical procedure to evaluate the scattering of electrically small antennas on small UAV platforms. The agreement between measurements and theory for the return loss and radiation patterns of a blade monopole antenna on an AAI Shadow UAV substantiates that its graphite epoxy wing is conductive and can be modeled as a perfect electrical conductor (PEC).