  We introduce RFEye, a generalized technique to locate signals independent of
the waveform, using a single Unmanned Aerial Vehicle (UAV) equipped with only
one omnidirectional antenna. This is achieved by acquiring signals from
uncoordinated positions within a sphere of 1-meter radius at two nearby
locations and formulating an asynchronous, distributed receiver beamforming at
the UAV to compute the Direction of Arrival (DoA) from the unknown transmitter.
The proposed method includes four steps: 1) Blind detection and extraction of
unique signature in the signal to be localized, 2) Asynchronous signal
acquisition and conditioning, 3) DoA calculation by creating a virtual
distributed antenna array at UAV and 4) Obtaining position fix of emitter using
DoA from two locations. These steps are analyzed for various sources of error,
computational complexity and compared with widely used signal subspace-based
DoA estimation algorithms. RFEye is implemented using an Intel-Aero UAV,
equipped with a USRP B205 software-defined radio to acquire signals from a
ground emitter. Practical outdoor experiments show that RFEye achieves a median
accuracy of 1.03m in 2D and 2.5m in 3D for Wi-Fi, and 1.15m in 2D and 2.7m in
3D for LoRa (Long Range) waveforms, and is robust to external factors like wind
and UAV position errors.
