Array Signal Processing for Advanced Surveillance: An Experiment with a 12-Element Linear Array and SDR

Aeronautical surveillance systems for air traffic control use Mode S signals. Precise estimation of the Angle of Arrival (AOA) of a Mode S signal by array signal processing can enable various applications. For example, AOA can be used to verify ADS-B positions. For Wide Area Multilateration (WAM), performance enhancement or reduction of the number of ground stations may be achieved by combining AOA with Time Difference of Arrival (TDOA). Ultimately, secondary surveillance radar (SSR) may employ electronic scanning. Therefore, the authors have been conducting an experimental study on AOA measurement for Mode S signals. In this paper, an experiment with 12 -element linear array and software-defined-radio (SDR) is presented. ADS-B signals were recorded during the experiment, and then array calibration using ADS-B signals and AOA estimation using beamformer, Capon, and MUSIC methods were applied.