1. A system comprising: an interface operable to obtain signals from antennas, where the signals correspond to components of vectors in space; one or more signal processors coupled to the interface and configured to: determine polarities of the signals based on phase measurements between the signals; reduce a possible number of vector interpretations based on the determined polarities of the signals; reduce a possible number of angles or angle differences between the vectors based on the reduced possible number of vector interpretations; and compare the reduced possible number of angles or angle differences to predetermined angle or angle differences.