ABSTRACT
Wireless communication services have experienced a tremendous growth during the last years, where speech has been the main application. With the introduction of a new generation of mobile or wireless communication systems, for example, third-generation systems, the focus is shifted toward data applications. The underlying physical principle of all antenna array algorithms is the fact that a transmitted signal propagates along some path and then arrives at the receiving antenna. Typically, several versions of the transmitted signal impinge on the receiving antenna from different directions because of multipath. To be able to estimate the direction of arrival of an electromagnetic wave incident on an array of antenna elements, it is necessary to understand the physical properties that govern the wireless channel and the antenna. The principal function of an antenna is to convert an electromagnetic wave into an induced voltage or current that is measured. If the antenna consists of several elements, a number of voltages or currents are measured.
