Radio Interferometer with UAV and SDR Payload for Direction-Finding of Non-Coherent Emitter

Direction-finding of non-coherent target emitters with unknown waveform using small receive-only UAVs is a challenging task. The traditional passive SAR techniques cannot be directly applied without prior information about the target waveform. Here, a new scheme of radio interferometer based on UAVs and SDR payloads is introduced. Large synthetic aperture is obtained through coherent processing of data collected by both stationary and moving SDR receivers. Then the DOA of emitter can be estimated accurately. In this work, synchronization and positioning methods for UAV-based receivers are proposed considering the vibrations of UAV platforms as well as drifts of distributed frequency sources. Extensive simulations and experiments are implemented to validate the proposed radio interferometer scheme and synchronization methods. The performances of DOA estimation are also evaluated.