Compact Antennas for Wireless Communications and Terminals: Theory and Design

Chapter 10Reconfigurable Antennas ¹

 

 

 

10.1. Introduction

The concept of reconfigurability suggests the ability of a system to dynamically modify its performance. We define a reconfigurable antenna (RA), as one which internally, or in the immediate neighborhood, uses active components that are able to change their base characteristics. The changeable parameters are:

– frequency (central frequency, bandwidth);

– polarization (type of polarization, orientation);

– radiation pattern (beamwidth and direction, shape of the pattern).

Reconfiguration circuits that are distant or isolated from the antenna are outside the scope of the subject of RAs. This is the case with active, phased array antennas, whose radiating elements are fed by phase shifters and programmable amplifiers.

A characteristic of reconfiguration does not signify that the antenna is intelligent, i.e. capable of automatically adapting to its environment. A decision-making and feedback process must be added, usually to the exterior of the antenna. This can take the form of a micro-controller or a field-programmable gate array (FPGA) that drives the negative feedback circuit containing the reconfigurable component. There are also examples of simple decision circuits, which are based on phase comparison systems used to self-adjust resonant frequencies [TUR 99].

The dynamic modification of the operating parameters of an antenna brings flexibility to communication systems. Antennas with pattern and/or polarization diversity ...