A study of MMSE adaptive array antennas for handsets in consideration of antenna configuration

Channel capacities and data rates of mobile communications have been increasing to meet demands of modern communications. In order to achieve a low bit error rate (BER), we need high signal to interference plus noise ratio (SINR). To realize the high SINR, it is effective to use an adaptive array antenna [1]. The adaptive array antenna can reduce the influence of multipath rays. On the other hand, the performance of an adaptive array antenna is strongly affected by the electromagnetic characteristics of the antenna array. An important electromagnetic characteristic of an antenna array is the mutual coupling between its elements. In the above work, mutual coupling between the antenna elements was, however, ignored. That is because the antenna elements were assumed to be isolated from each other. In practice, elements of an antenna array have mutual coupling which in turn affect the gain, beam width, etc., of the array [2]. But only little effort has been considered for developing adaptive antenna array receivers suitable for handsets. In fact, there are several difficulties with the implementation of such a solution at the handset level. First, the space on the handset device is limited, which does not allow us to implement an antenna array with enough elements for efficient spatial signal processing. The second problem is related to the movement of the mobile that provides an omnidirectional scenario. Third, the cost and the complexity of the implementation at every mobile is much greater than the implementation at each base station [3]. In this paper, MMSE adaptive array antennas for handsets in consideration of antenna configuration are studied when they are consisted of conventional antennas, such as a monopole and planar inverted-F antenna (PIFA) or newly proposed built-in folded monopole antenna (BFMA)[4] on a finite ground plane under simple propagation models.