Measurement Characterization for Localizing Multiple RFI Sources Simultaneously from a UAS

To combat the threat posed by jammers, a UAS based system has been developed to be able to rapidly localize the source of GPS interferers. Previously, the focus of the project, an unmanned aerial system (UAS) known as JAGER, has been on the development of a system capable of localizing a single static radio frequency interference (RFI) source [1]. JAGER is a UAS comprised of three main systems: the sensor to measure the bearing to the interference source, the localization system responsible for estimating the source location, and a path planning system to fly the vehicle in a way to minimize the cost of localization (typically thought of as the time to localize a source within a threshold) [2]. This works presents an analysis of the capabilities of the sensor, a phased array antenna, in an environment with multiple RFI sources. Understanding the sensor capabilities is key to being able to choose the right approach for localization and path planning. The introduction of additional interference sources poses a key challenge on the sensor’s ability to detect and measure the bearing to multiple sources simultaneously from a single receive signal strength (RSS) pattern. This paper presents a characterization and theoretical analysis of the performance of a 3-, 7-, and 19-element array in an environment with multiple interference sources. The difference in beamwidths of the different array sizes and side lobe suppression result in biases in the bearing measurements for the smaller arrays, while the larger arrays come at additional size, weight, and monetary costs, creating a set of tradeoffs to be considered for a system to localize multiple RFI sources from a UAS. To detect multiple sources, JAGER uses an onboard beam steering antenna to generate an RSS pattern (by measuring signal strength). For each RSS pattern, the bearing to each of the lobes detected is determined using the 3dB method used for bearing determination to a single source [3]. The theoretical performance of this method is evaluated in two different simulated multi-source environments. Finally, some design constraints are presented for the bearing sensor for detecting multiple sources based on the desired angular separation capabilities.