Biologically Inspired Radio-Frequency (RF) Direction Finding

This document is the final technical report for the Biologically Inspired RF Direction Finding project funded by the Army Research Office ARO under research agreement No. W911NF-1-01-0285. We have been investigating novel RF direction finding techniques inspired by human auditory system with the goal of achieving high performance and portable RF direction finding systems. We have studied improved two-antenna microwave passive direction finding systems inspired by human auditory system. By incorporating a head-like scatterer in between two antennas, additional magnitude information can be utilized to estimate the direction of arrival DoA of a microwave signal, thus eliminating ambiguities associated with phase wrapping at high frequency, just like human ears. A new portable DF system design based on PIFA antennas that are well suited for wireless mobile applications has been completed and tested in laboratory environment. Furthermore, it has been demonstrated that this technique can be extended to 3-D direction finding DF. In addition, better DoA sensitivity is demonstrated with the incorporation of high-permittivity scatterer due to the enhanced phase difference. A novel DoA technique for broadband microwave signals is also investigated. A single Ultra-Wide-Band UWB antenna, inspired by the sound source localization ability of human auditory system using just one ear monaural localization, has been utilized. By exploiting the incident angle dependent frequency response of a wide-band antenna, the DoA of a broadband microwave signal can be estimated. DoA estimation accuracies are evaluated for various antennas and microwave signals under different signal-to-noise ratio SNR scenarios. Promising DoA performance of the proposed technique is demonstrated in both simulation and experiment. Another single antenna DF demonstration based on a leaky wave antenna has also been accomplished.