Multiport Interferometer-Enabled 2-D Angle of Arrival (AOA) Estimation System

A systematic scheme for finding the direction of arrival (DOA) or 2-D angle of arrival (AOA) of an electromagnetic beam is proposed and demonstrated in this paper. This system estimates the respective angle of propagation vector of an incoming plane wave in either horizontal or vertical plane. It consists of three main parts, namely, an antenna, a multiport wave interferometric receiver or phase discriminator, and a signal processor. The antenna is composed of four receiving elements located in the same plane, which is arranged in a diamond-shaped configuration. The received signals manifest relative phase differences that contain information about the beam's DOA. With the proposed eight-port junction topology, the interferometer extracts these informative phase differences and leaves them for a simple signal processing algorithm to estimate the two angles. The theoretical analysis of the proposed scheme is presented along with system-level simulation results for the proof of concept. In addition, an appropriate calibration technique is formulated to deal with nonidealities and consecutive errors in practice. One of the main applications of such a system is related to the angular detection of an antenna-to-antenna misalignment in pencil beam millimeter-wave systems. Therefore, implementation of the presented system scheme for millimeter wave applications is briefly discussed for its prototyping over 60-GHz range (V-band). Finally, the performance of the prototype system is assessed through a set of system-level measurements. Excellent results are obtained, thus validating the outstanding functionality of the proposed system. Simplicity, low cost, compact size, and operational accuracy make this system a superior candidate for 2-D angle detection applications.