Direction of Arrival Estimation System Based on a Vertically-Polarized Circular Array With 360° Continuous Null Steering

A design for direction of arrival estimation (DOA) is proposed. The design is using a compact circular array with four vertically-polarized coplanar patch antennas. With a feed network mainly composed of several couplers and one tunable phase shifter, the radiation of the circular array at 2.45 GHz can generate one null, and the null can also be continuously scanned over the whole horizontal plane. Based on the null-steering radiation patterns, two methods of estimating the arrival angle are studied and compared. A microcontroller and a RF power detector are also integrated into the feed network to implement a complete system. The experiments of DOA estimation are conducted, and the results demonstrate that the proposed DOA system can provide an average estimation error of about 1.5° within the range from −180° to 180°.