Angle of Arrival/ Direction Finding Techniques

Angle of Arrival (AoA) or direction finding (DF) techniques are perhaps the most conceptually straightforward geolocation techniques available. We simply measure the direction from which a signal arrives, and then project a line of bearing (LOB) back out along the same direction. Doing this with receivers at two spatially separated locations allows two LOBs to be drawn, which will intersect at the signal source position. This conceptual simplicity at the surface level, though, obscures a more complicated picture. The devil is in the detail, and in this case, the detail is in the seemingly simple task of working out the direction of the incoming signal.
In this white paper, we will examine a series of techniques that can be used to determine this. These techniques fall roughly into two categories - amplitude comparison, which measures differences in the amplitude of the incoming signal with direction, and phase comparison, which relies on measuring differences in the phase of the signal.