Interferometer angle-of-arrival determination using precalculated phases

Abstract

A method has been developed to determine the angle of arrival (AoA) of incident radiation using precomputed lookup tables. The phase difference between two receiving antennas can be used to infer AoA as measured from the pair baseline, but there will be more than one possible solution for antenna spacings greater than or equal to half a wavelength. Larger spacings are preferable to minimize mutual coupling of elements in the receive array and to decrease the relative uncertainty in measured phase difference. We present a solution that uses all unique antenna pairs to determine probabilities for all possible azimuth and zenith values. Prior to analysis, the expected phase differences for all AoAs are calculated for each antenna pair. For a received signal, histograms of possible AoAs for each antenna pair phase difference are extracted and added to produce a two‐dimensional probability density array that will maximize at the true value of the AoA. A benefit of this method is that all possible antenna pairs are utilized rather than the restriction to specific pairs along baselines used by some interferometer algorithms. Numerical simulations indicate that performance of the suggested algorithm exceeds that of existing methods, with the benefit of additional flexibility in antenna placement. Meteor radar data have been used to test this method against existing methods, with excellent agreement between the two approaches. This method of AoA determination will allow the construction of low‐cost interferometric direction finding arrays with different layouts, including construction of difficult terrain and three‐dimensional antenna arrangements. Plain Language Summary A method has been developed to determine the direction that radio waves are coming from when detected by an arrangement of antennas. The method looks at each of the unique pairs of antennas and compares the received signal with what would be expected for all possible directions. The results from all of the pairs of antennas are added to find the true direction that the radio waves are coming from. This improves the accuracy of simple radars and allows different types of antenna patterns to be used. Computer simulations show that the suggested method is very effective. Tests of data from a real radar also show excellent agreement between the new method and existing techniques.