Experimental study of DOA estimation using a compact monopole array

Abstract

Space-time techniques like MIMO, diversity reception and direction finding all require multiport antenna arrays. In mobile applications, the size-limited platforms demand compact arrays with element spacing significantly smaller than λ/2. The small element spacing introduces strong mutual coupling between the elements of such compact arrays. For application of direction-of-arrival (DOA) estimation using typical DOA estimation algorithms, for example MUSIC [1], the mutual coupling effect between antenna elements significantly contributes to the estimation error. Many compensation methods have been proposed in previous studies [2]-[3]. The most commonly used one is the conventional mutual impedance method (CMIM) proposed in [4]. Recently, a modified concept of mutual impedance in receiving antenna arrays, the receiving mutual impedance, was proposed in [5]. This method is called the receiving mutual impedance method (RMIM). Theoretical studies have shown that much higher accuracies for DOA estimations can be achieved when the mutual coupling in receiving arrays are characterized using the RMIM than the CMIM. The current study is to provide experimental evidence on this. In this paper, a seven-element monopole array with element spacing of 0.2λ was used in the experiments. Both the receiving mutual impedances and the conventional mutual impedances of the array were measured. A series DOA experiments were then performed with one and two signal sources generated by transmitting antennas inside the anechoic chamber. © 2010 IEEE.