Patent ID: 7538727

Claim:
A system for determining the bearing of a source location from a receiver location, the system comprising: a phase reference signal source operable to generate a phase reference signal; at the source location, a first beatable signal source operable to transmit a first beatable signal and a second beatable signal source spatially offset from the first beatable signal source in a reference direction, the second beatable signal source operable to transmit a second beatable signal differing in frequency from the first beatable signal by a frequency difference, the first beatable signal and the second beatable signal collectively having a phase relationship with the phase reference signal; and at the receiver location, a receiver structured to receive the first beatable signal and the second beatable signal and operable to determine a direction angle, relative to the reference direction, of the source location from the receiver location, the receiver performing operations comprising: measuring a phase difference between a beat signal and one of (a) the phase reference signal, and (b) an additional beat signal, the beat signal obtained by a process comprising summing the first beatable signal and the second beatable signal, the additional beat signal obtained by a process comprising summing the first beatable signal and the phase reference signal, and determining the direction angle from the measured phase difference.