Experiments on Interferometric Angle of Arrival Estimation Using a Simple Weight Network

An experimental verification of angle of arrival (AOA) estimation that employs an RF-based interferometric monopulse technique is given for car applications. The AOA antenna is comprised of nine elements, eight of which are arranged in a circle and equal angular intervals of 45°; an additional element is located at the center of the circle. We used a weight network for processing the received signals, in which the phase of the received signals for each element is delayed in accordance with the coordinate of the elements using the different length of transmission lines. The use of a rat-race hybrid coupler allows a 180-degree phase reversal to be involved in the two combined signals, enabling a simple small-sized AOA network to be realized. The experimental results reveal that the AOA antenna has an error in the estimated angle of 6.1° on average in the whole azimuth angle.