Measurement of angle of arrival by small circular array antenna for aircraft
Masayuki Shirakawa, Yutaka Fukuda, Shigeru Ozeki · Electronics and Communications in Japan (Part I Communications) · 1993
Abstract For an airborne collision avoidance system, it is necessary to measure the directions of other aircraft in the vicinity with high accuracy. As one of the methods for such a purpose, a method was studied in which a small circular array and Butler matrix are combined. In such a case, the mutual coupling between the elements increases. However, by adjusting the phases appropriately, it is found possible to maintain a phase relationship in the same way as in the case without mutual coupling. Also, an angular measurement method was proposed in which the outputs of the Butler matrix are combined at the output stage. It was found that the accuracy is close to the one obtained in the maximum likelihood estimator while the circuit is simple.