Abstract. In smart antenna system, it is extremely crucial to estimate the direction of incoming signals in order to achieve better reception. Reliability of DOA estimation depends on several factors such as the choice of DOA algorithm, size of antenna array as well as array geometry. Therefore, it is particularly desirable to have a configuration of antenna array that could produce an accurate azimuth estimation. In this work, a new planar array is proposed to address the problem of azimuth estimation. This is achieved by having a flexible element position on the xy plane that improves the steering vector, hence significantly enhances the accuracy of DOA estimation. Besides, a fair distribution of the antenna elements on the x-y plane also helps to eliminates estimation failure in the azimuth range between 240° and 360°. A comparison study between the proposed array and V-shape array is performed in order to gauge the performance of the proposed array in DOA estimation. Simulation results show that the proposed array has acquired better estimation resolution than V-shape array. On top of that, the proposed array has reduced estimation error in V-shape array. It is concluded that the proposed array has shown potential as an excellent choice of antenna array geometry for smart antenna system.
IntroductionDirection of arrival (DOA) estimation for smart antenna system has been investigated extensively in the last six decades and has been applied in various fields including wireless communication, radar, sonar and audio processing [1][2][3][4]. The role of DOA estimation in smart antenna system is essential since it helps to estimate the direction of the incoming signal. The estimated signal direction will be used to point the array beam towards the estimated direction. There are several factors that contribute to the performance of DOA estimation such as the number of element in the array, spacing between elements, size of the array and shape of array [5]. Linear array provides a simple form of antenna array, and it also straightforward to be analysed. However, its capability is limited to one-dimensional DOA estimation, which is only for elevation angle estimation. In order to have both azimuth and elevation angles estimation, a two-dimensional array is needed. Thus, there are several initial configuration of planar arrays have been proposed in the literature such rectangular, triangular and circular arrays [6][7][8][9][10]. Among these initial proposals, circular array provides a unique property of ability to cover azimuth angle in a uniform manner. In general, the computational complexity of DOA estimation is significantly affected by the array geometry due to the increase in the dimensionality of two-dimensional DOA estimation problem [11]. Therefore, vast efforts have been emerged to reduce the computational complexity as well as to simplify the estimation algorithm.