Antenna Array for Reconfigurations

1. Introduction

Due to the rapid growth of wireless communications as well as the high demand for the integration of multiple wireless standards into a single platform, it is the most important that the operating frequency, radiation pattern, and polarizations of antennas can be reconfigurable. Reconfigurable antennas modify their operating frequency, impedance bandwidth, polarization, and radiation pattern as per the operating requirements of the usage and applications. They can easily radiate multiple patterns at different frequencies and polarizations. Now a days, obtaining the desired functionality for a reconfigurable antenna and integrating it into a complete system to achieve an cost-effective and efficient solution is a challenging task for antenna designers. As we are heading towards from 5G to 6G, these analysis is very helpful to design the such smart sixth generation antennas. Converting an antenna into a reconfigurable device by applying different techniques to change the antenna’s internal structure by applying different techniques has been challenging. Multiple factors need to be considered such as achieving a good gain, good efficiency, stable radiation pattern, and a good impedance match throughout all the antenna’s operation in given environment. To achieve a good gain, stable radiation pattern, and good impedance matching throughout the operation, the reconfigurable antenna designers must focus on the following questions such as which property (e.g. frequency, radiation pattern, or polarization) must be modified for the antenna and how the radiating elements of the antenna structure are reconfigured to achieve the required property? As well as which reconfiguration technique can minimize the negative effects on the antenna performances? A reconfigurable antenna provides the same functionality as that given by multiple single-purpose antennas. This is useful for saving in costs, weight, volume, and maintenance/repair resources. According to the attractive features, reconfigurable antennas have received considerable attention, and a number of works have been demonstrated in past years (Brown. 1998). Furthermore, several review and survey papers have been under work and published recently (Erdil et al. 2007). However, these reviews have only centered on electrical reconfiguration with active elements such as PIN diodes and varacter diodes. Various kinds of reconfigurable antennas including radiation pattern reconfigurable antenna, polarization reconfigurable antenna and a combination of radiation and frequency reconfigurable antenna are discussed in many papers. In addition to this, more details of different types of reconfigurable antennas are described in (Grau, 2010). Not only based on the reported reviews, but also, here many investigations of different types of effective implementation techniques like electronic switching and other possible switching techniques of reconfigurable antennas have been discussed. In order to demonstrate the reconfigurable antennas, various effective implementation techniques have been given to be used in different wireless systems such as satellite, multiple-input multiple-output (MIMO) and cognitive ratio communications, which are classified as below: (i) Electrical reconfiguration; (ii) Optical reconfiguration; (iii) Physical reconfiguration; (iii) Reconfigurable antennas with smart materials. The most common and widely used technique is electrical reconfiguration, which uses active elements such as PIN diodes, varactors and radiofrequency micro-electromechanical system (RFMEMS) switches (Nikolaou et al. 2009). PIN diodes have acceptable performance and a low price compared to RFMEMS switches. Other technique is called optical reconfiguration, which relies on photoconductive switching elements .