Design and Implementation of Reconfigurable and MIMO Antennas for Future Heterogeneous Wireless Systems

Abstract

The recent progress in electronics and communication technologies has driven the unprecedented demand for multi-functional wireless communication in most single wireless devices. However, employing the limited spectrum effectively on communication equipment poses a key design challenge, as most antennas often suffer from bandwidth limitations and restricted frequency rarge. Onekey approach to overcome this problem without significantly affecting the antenna size is to apply antenna tuneability and reconfigurability. This is achieved by electronically changing some properties of the antenna usually by loading the reactive loading of the resonator by means of active electronic elements including varactor diode or PIN diode with extra circuitry. The main objective of this research is to design and investigate low-profile antennas for heterogeneous wireless systems using the antenna reconfigurability concept through tuning and/or using the MIMO antenna techniques. The research focuses on antenna design and implementation to cover various wireless standards and applications within the electromagnetic spectrum including UMTS (1.92-2.17 GHz), Cognitive Radio such as WLAN and WiMAX (2.4GHz), Wi-Fi (5.2GHz), 5G (600MHz - 6GHz) and MBAN applications. A family of compact microstrip printed reconfigurable antennas for various cognitive radio applications is presented. Effects of various slots on the antenna performance are also investigated, and the final version was reconfigured across a broad frequency range (1.5 - 2.4 GHz) Furthermore, four new variants of the miniaturised hexagonal-shaped monopole printed antennas for different UWB applications are proposed. Prototypes of the four versions are fabricated and compared to establish their results. Two reconfigurable rejection bands are introduced to avoid anticipated interference with other systems working within the UWB range. Finally, a novel low-profile four-element MIMO antenna was designed and fabricated to operate at the 2.4 GHz ISM band. both measurements and simulation results revealed strong agreement. Furthermore, the designed antenna was also tested on human tissues, with acceptable results when compared to its performance in free space. it is proved to be a good fit for wireless, mobile communications, medical systems and WBAN applications.