Unambiguous 2-D Angle-of-Arrival Estimation Receiver based on a 16-port Interferometer

 An unambiguous 2-D angle-of-arrival (AoA) estimation receiver (Rx) based on a 16-port interferometer is proposed and demonstrated in this paper. It has three main components: eight antennas, a 16-port interferometer, and a signal processor. The antennas are in the same plane in a concentric-square shaped configuration. The eight input signals are superposed on eight output port signals in the interferometer. First, an AoA estimation algorithm for the proposed 16-port interferometer is described. The algorithm transposes the phase differences between the antenna elements into the power relationship of the output signals. Then, a method for reducing angle ambiguity is introduced. The method allows for the distance between the antenna elements to be larger than λ/2, and the angle detection range is theoretically -90° to 90°. Then, the Rx error models are established to obtain the systematic errors. An Rx operating at 31 GHz was fabricated. The measurements demonstrate that the system operates as expected, with AoAs ranging from 30° to 30° and a mean squared error of approximately 0.4°.