Patent ID: 8334808

Claim:
An antenna system for estimating the direction-of-arrival (DOA) of an arriving signal, wherein said arriving signal arrives substantially from the horizon within a predefined range of elevations below and above the horizon, said antenna system comprising: a first omnidirectional antenna; and a second omnidirectional antenna, which is located coaxially about a predefined vertical axis in relation to said first omnidirectional antenna and separated therefrom at a predefined vertical distance D, wherein said first omnidirectional antenna is configured to receive said arriving signal and transform the received signal into at least two output signals: a first output signal and a second output signal, wherein the phases of said output signals are proportional to the azimuth angle of said arriving signal, wherein said second omnidirectional antenna is configured to receive said arriving signal and transform the received signal into a reference signal of a reference phase, said reference phase has a zero phase-slope and is independent of the azimuth angle of said arriving signal, wherein said phases of first and second output signals are shifted from the reference phase by a phase shift that depends upon the elevation direction of said arriving signal, corresponding to said distance D between said first and second omnidirectional antennas; wherein said antenna system is configured to allow extracting at least two phase differences: a first phase difference Δ 1 between the phase of the first output signal and the reference phase and a second phase difference Δ 2 between the phase of the second output signal and the reference phase, wherein each said phase difference includes a first phase component proportional to the azimuth angle of said arriving signal and a second phase component corresponding to the elevation angle of said arriving signal; and wherein said antenna system is further configured to enable extracting the azimuth and the elevation angles of said arriving signal from said phase differences.