Development of a Three-Element Beam Steering Antenna for Bearing Determination Onboard a UAV Capable of GNSS RFI Localization

Localization of radio frequency interference (RFI) sources requires some method of measuring the interference signal. A technique used for this problem in the past, coupled with an unmanned aerial vehicle (UAV), is using a collection of signal strength measurements to determine bearing to the source. This paper focuses on the improvements from a physical rotation based system to an electronic rotation system. Previously 30 seconds was required to collect a set of signal strengths to use for a bearing and now, with a beam steering antenna, that rotation time is reduced to just over 0.5 seconds. Here, the improvements to the measurement sensor onboard a UAV for RFI localization are detailed. Using the same philosophy to get bearing from a collection of signal strength measurements, these improvements move from a physical rotation to an electronic rotation through the development of a small and compact three-element beam steering antenna. Using this type of antenna allows for signal strength measurements at 500Hz and in motion and therefore enables a much higher observation rate, on the order of 2Hz, enabling the use of different navigation and path planning algorithms that could lead to much faster and more efficient localization. This paper describes the design, development and testing of the beam steering antenna itself, the algorithms for controlling the beam steering to be able to get the best observation performance, and finally demonstrates the performance of the antenna during live interference exercises at Edwards Airforce Base (AFB).