Compact multifunctional antennas for wireless systems

Chapter 3

Reconfigurable Antennas

Xue-Song Yang, Shao-Qiu Xiao, and Bing-Zhong Wang

3.1 Introduction

To support a variety of applications, such as communication, navigation, and surveillance, most wireless systems require more than one antenna. These antennas, which may work at different frequencies and polarizations, are usually installed at a number of positions on a wireless platform, such as a radar station, a satellite base station, or a mobile phone, for better reception quality. The use of multiple antennas is definitely very undesirable, as it can increase system size and material costs. Worse still, the antennas may introduce electromagnetic interference, which can jeopardize normal operation of the electronic circuits. It is obvious that a possible way to cut down the number of antennas is to have one that can be reconfigured to provide several functions and can also operate at different frequencies, switch field polarizations, and sweep the radiation beams. Such a new multifunction antenna configuration is called a reconfigurable antenna. The concept of a reconfigurable antenna first appeared in a U.S. patent in 1983 (1). Since then it has been well received by academics, industry, and the military. In general, an antenna can easily be made reconfigurable by either incorporating active devices or by having multiple input ports. For the first type, switches such as microelectromechanical system (MEMS) switches, PIN diode switches, and optical switches are usually employed ...