Direction of arrival estimating array antenna # Hirotoshi Sakai 1 , Eisuke Nishiyama 2 and Ichihiko Toyoda 3 1, 2, 3 Graduate School of Science and Engineering, Saga University 1, Honjo-machi, Saga-shi, Saga, 840-8502, Japan E-mail: 1, 2 {sakai, nisiyama}@ceng.ec.saga-u.ac.jp, 3 {toyoda}@cc.saga-u.ac.jp 1. Introduction Recently, many kinds of radio communication and sensing systems using microwave and millimeter wave are actively developed. In the systems, highly integrated wireless devices having a function of RF signal processing are required for miniaturization and simplification [1]. In this paper, a novel array antenna for DOA estimation systems using a phase mono pulse mechanism is proposed. The proposed array antenna consists of patch elements and a both-sided feed line circuit including Magic-T circuits [2]. In the DOA estimation, the arrival angle is obtained by sum and difference of received signals on two pairs of patch elements. The proposed array antenna estimates arrival angle by taking the power ratio of the sum and difference which are easily obtained using the simple Magic-T circuit. The principle of the DOA estimation system using the propose array antenna is described in section 2 and 3. The characteristics of the proposed antenna are also discussed in section 4. 2. Principle of the proposed DOA estimation Figure 1 shows the proposed antenna for DOA estimation systems. This antenna is composed of a 4-element antenna array and two magic-T circuits. When RF signal is received by the antenna elements, summed and differential signals are obtained at Port 1 and Port 2, respectively. Figure 1: Structure of DOA estimating array antenna In this paper, a phase mono pulse system shown in Fig. 2 is used for DOA estimation. When the phase difference of the signals received by the antenna elements #1 and #2 is ∆φ [deg.], the arrival angle θ[deg.] can be obtained by the following equation. θൌ sin ‐1 ∆ߣ 2ߨ ሺ1ሻ where d and λ are the distance between antenna elements and carrier wavelength, respectively. Fig. 3 shows a vector chart to explain the principle of the DOA estimation. When the RF signal is POS2-24 Proceedings of ISAP2012, Nagoya, Japan 1124