Undesired Radiation Suppression Technique with Adaptive Control for Distributed Array Antenna Systems in Mobile Environment

Abstract

<jats:p>We have proposed a distributed array antenna (DAA) system for high-speed satellite communications. The DAA system uses multiple small tracking antennas and combines the transmission signals in-phase to increase the antenna gain. DAA system has a problem that the undesired radiation at the sidelobe direction increases as the antenna gain at the main lobe direction increases. In the mobile environment, the conventional technique can suppress the undesired radiation in the limited condition because of changing the direction of the undesired radiation according to the movement of the mobile station. This paper proposes a DAA technique that suppresses the undesired radiation by setting a transmission plate at each antenna aperture and moving them via adaptive control. The transmission plate consisting of a metal patch or slot retransmits electromagnetic waves and changes the amplitude and phase of the waves. To change the radiation patters of each antenna, the transmission plate rotates according to movement of the mobile station. After combining these changed signals, the adaptive control selects the rotate angle of the transmission plate to decrease the undesired radiation at the sidelobe direction. The antenna gain on the main lobe direction after combining is achieved with lower loss because the insertion loss through the transmission plate is smaller. The proposed technique offers more than $2.4$ dB improvement with three antennas and more than $3.5$ dB improvement with four antennas assuming each consists of $8 ¥times 8$ patches.</jats:p>