The design and analysis of antenna array for MIMO communication

Abstract

Information theory has shown that an upper limit exists for the average spectral efficiency using a single transmitter and single receiver [1]. Thus, Multiple Input Multiple Output (MIMO) antennas have received a great attention for their ability to overcome the limits of SISO channel capacity [2]. However, in order to realize MIMO system in mobile terminal, we have to allocate multiple antennas in the small size ground without reducing MIMO performance. Also, we need to consider array antenna design and MIMO channel state simultaneously in order to reach the maximum achievable capacity. Many research institutes try to realize MIMO system mobile terminal recently, however, there is no commercial MIMO handset by this time because of these difficulties. Thus, the author tries to solve this problem by analyzing antenna parameters which is related to MIMO performance, and attempts to optimally allocate the multiple array antennas in the small size ground. In addition, the spatial correlation always exists which causes the loss of capacity. Thus, we need to find the way to reduce spatial correlation in order to improve channel capacity. To reduce the spatial correlation, the space, polarization, and pattern diversity antennas are most widely used. Recent studies shows that the distance between antennas needs to be multiple of the wavelength in order to achieve spatial multiplexing in MIMO communication, so the size of ground must be much larger than typical compact mobile terminal. Thus, we conclude that space diversity technique is not suitable for 4G wireless handsets. Instead, pattern/polarization diversity might be practical solutions to reduce the array size. To solve the spatial correlation problem, this thesis proposes the pattern/polarization diversity array by applying vertical and horizontal feeding. The details of this thesis are explained as following. First, this thesis presents the evaluation of MIMO (multi-input multi-output) array by analyzing mutu...