Active Reconfigurable MIMO Antenna Systems

Summary

Reconfigurable antennas are well known in the literature and practical implementations where the antenna characteristics are controlled and reconfigured based on the application at hand. For example, the frequency band covered can be changed and swept within a larger band to allow a certain device to operate in various geographic areas or within different operators that use different dedicated bands. The control can be also of the antenna radiation characteristics via the beam pattern change to direct the energy toward specific directions. The topic of reconfigurable antennas has been well documented in literature and some of the fundamental references on the topic are . In this chapter, we will discuss several reconfigurable MIMO antenna systems using active elements. We will focus on active electrical elements rather than mechanical or optical‐based ones due to their ease of integration, low cost, wide usage and stability of operation. In addition, reconfigurability can be made via the change of the material properties of the substrate but this mechanism will not be the focus in this chapter. The most practical reconfiguration elements are electrical‐based ones, which usually are various kinds of electrical switches or variable capacitors (i.e. PIN diodes, varactor diodes, RF switches, etc.). This chapter will start by discussing frequency‐reconfigurable MIMO antenna systems and some of the basic controlling circuits for switching‐based and variable capacitor‐based ones, then will move forward toward pattern and polarization reconfigurabilities. In each section, several examples from literature are shown to aid the reader in his/her future designs and understanding of the operating principles of such antenna systems. The chapter ends with a detailed design example that can help the reader start developing a frequency‐reconfigurable (agile) MIMO antenna system in sub‐6 GHz bands using a simple varactor diode model.