Covert and broadband direction finding using low-profile slot spiral antennas

A broadband direction finding (DF) array is presented in this work using low-profile slot spiral antennas. Often, DF systems use omnidirectional dipole or monopole antenna elements which can result in a limited bandwidth and an obvious visual signature. In contrast, the slot spirals employed in this work are low-profile and can be flush-mounted on metallic objects which can enable a covert DF implementation. Simulation results are shown using four slot spiral antenna elements placed on a vehicle model from 400 MHz to 1.2 GHz (100% fractional bandwidth). The near-constant characteristics of the slot spiral over a wide frequency range provides broadband DOA estimation accuracy performance. Results are shown for both vertically and horizontally polarized terrestrial incoming signals with various signal-to-noise ratios.