I. Introduction
In many advanced communication systems, antenna arrays are highly desirable due to their high directivity and beam steering capability. However, the development of antenna arrays is relatively time consuming and expensive. In addition, antenna arrays are often designed for certain applications which means that the technology developed for one project cannot be adopted for another one. Therefore, reconfigurable antenna arrays which have the capability of electrically changing their RE communication parameters such as center frequency, polarization and radiation pattern have attracted significant attentions in recent years. Most of previous reconfigurable antenna works demonstrated the tuning of one or two RF parameters for a single antenna [1]. There is little work on reconfigurable antenna arrays which can dynamically change the aforementioned RF parameters.