Dielectric Resonator Antennas: Applications and developments in multiple-input, multiple-output technology

This article presents a comprehensive review of multiple-input, multiple-output (MIMO) dielectric resonator antennas (DRAs) that have evolved in the past decade. In addition to the major challenges faced during designing an MIMO DRA, this article also discusses research gaps that must be filled in the future. Exploring the advantages of DRAs, numerous novel designs have been proposed in the last few years

Multiple input multiple output dielectric resonator antenna with circular polarized adaptability for 5G applications

In this paper, the concept of the circularly polarized agile, multiple-input multiple-output (MIMO) dielectric resonator antenna (DRA) structure for fifth generation (5G) new radio application in mobile terminal is presented. Two prototypes have been fabricated, namely one with cylindrical DRA (CDRA) referred as A1 and a second one with ring DRA (RDRA) named as A2. These practical realizations of dual-port MIMO antennas have been mounted on a Rogers 5870 substrate of octagonal shape with proper ground architecture. The proposed dual-port MIMO antennas have been excited with conformal probes and L-type feed network aiming to achieve circular polarization (CP). Measured impedance bandwidth of A1 and A2 are 21.2% (3.15-3.9 GHz) and 22.2% (3.12-3.9 GHz), respectively. Moreover, for both antennas low mutual coupling between ports with minimum isolation of dB over entire impedance bandwidth has been obtained by using triangular head slots in the ground plane. Measured axial ratio bandwidths in broadside direction are 5.66% (3.26-3.45 GHz) and 4.25% (3.45-3.6 GHz), respectively. Maximum gains are 7.3 and 7.2 dBi, in that order. MIMO antenna parameters such as envelope correction coefficient, diversity gain (DG), mean effective gain and total active reflection coefficient are also calculated to verify MIMO performance parameters. The proposed antennas also demonstrate CP agility with insertion of concentric cylindrical shells of different radii

A dual band hybrid mimo dielectric resonator antenna for long term evolution applications

Dielectric resonator antennas (DRAs) are widely used in the last two decades. Comparison with microstrip patch antenna, DRA can provide high bandwidth, low metallic losses and high radiation efficiency. Smaller size of meander line is suggested to replace conventional microstrip line. Multiple-input multiple-output (MIMO) can increase more channel capacity and throughput compared to single port. In this project, a dual band MIMO hybrid DRA for LTE applications is proposed. This hybrid technique will be consisted of DRA and meander-typed antenna as radiators which can operate at LTE band 8 (880-960 MHz) at ???? = 900 MHz, LTE band 2 (1.85-1.99 GHz), 3 (1.71-1.88 GHz), and 9 (1.7499-1.7849 GHz) at ???? = 1.8 GHz respectively. A triple band is obtained in the simulations of HFSS software with additional 2.3 GHz for LTE Band 30 (2.305-2.360 GHz). The MIMO prototype has bandwidth up to 6.53 % at Port 1 and 12.68 % at Port 2, with isolation ranging - 6.10 dB to - 22.76 dB at 0.9, 1.5, 1.8 and 2.5 GHz

A Study on Frequency Reconfigurable Antennas for Applications in Frequency Agile Radio and mm-Wave.

As the current technologies in mobile communications are constantly growing it is becoming a necessity for researchers to investigate and deliver novel, versatile and agile devices providing adaptive performance in order to fulfil the ever changing requirements for communication engineering standards in the next and currently developing generation of mobile communications known as 5G. The current technologies in adaptive antennas have provided optimal numbers using comprehensive technologies that are compatible with the past generations of mobile communications. However, the increasing amounts of data exchanged by mobile devices nowadays require multiple services to be covered by reduced number of devices. In order to overcome this inconvenience, the use of reconfigurable antennas, specifically frequency reconfigurable antennas introduce an adaptive and innovative concept for versatile devices with applications in radio agility that overcomes the limitations of the current devices that are unable to cover multiple services by a single antenna. Two different kinds of frequency reconfigurable antennas are discussed in this work. The design, simulations, manufacture, and measurements for the discussed antennas are developed in this thesis. The first discussed designs are three prototypes of 1×2 triple-slotted antennas with different positions in the board. These boards offered independent frequency tuning using varactor-loaded slots that are electrically tunable by voltages from 0 – 25 V offering a fully tunable frequency range from 0.57 GHz and up to 2.73 GHz. The commented antennas offered independent metrics for frequency response and radiation patterns as well as good agreement between simulations and measurements. Moreover, the three slot antenna prototypes were object of a study in diversity metrics as they present spatial diversity schemes. The simulated and measured diversity parameters observed agreed on optimal numbers for frequencies above 750 MHz for the three prototypes with correlations well below 0.3 and diversity gains near the ideal value of 10 dB which allows reduction of required power in multi-antenna systems and determines its capacity to operate in MIMO systems for 5G. The second kind of antennas discussed in this is a dielectric resonant antenna (DRA) designed to operate at 28 GHz using bioplastics with relatively low dielectric constants and filled by different materials in order to achieve frequency reconfiguration including electrically tunable substances such as graphene oxide covering a frequency range from 26.3 GHZ to 28.3 GHz presenting good agreement between measured and simulated reflection coefficients and radiation patterns

MIMO antennas for mobile phone applications

Recent evolutions in wireless mobile communications have shown that by employing multiple inputs and multiple outputs (MIMO) technology at both the transmitter and receiver, both the wireless system capacity and reliability can be enhanced without the need for increasing the power transmitted or using more spectrum. Despite a considerable amount of research have been done on the design of MIMO and diversity handset antennas, the design of low profile, small footprint and multi-standard (wideband or multiband) diversity antennas on handset devices remains a challenging issue. Therefore, the purpose of this thesis is to present new antenna structures for handset MIMO and diversity applications. As the MIMO antenna design can be conducted either using multiple element antennas (MEA) or isolated mode antenna technology (IMAT), the work in this thesis is fallen in these two general design themes (areas). The first area under investigation concerns multiport antennas (IMAT antennas). It has the following two contributions: • A novel dual-feed water-based antenna is designed from a low cost liquid material with a very high dielectric constant (pure water ). The isolation between feeds is achieved by two back to back L-shaped ground plane strips. A prototype is made and the optimised diversity parameters are obtained, the results show that this design has a good diversity performance over the frequency range of 2.4 – 2.7 GHz. • A new and low profile (h = 3 mm) planar inverted-F antenna (PIFA) with a coplanar-feed is presented. It has a wideband response over the frequency range of 2.35 – 3.25 GHz. The design is based on a comparative study on the mutual coupling between different feed arrangements. As a result, the coplanar feed is employed in the proposed antenna; the polarization diversity is achieved by exciting two orthogonal radiation modes. The isolation between the feeds is achieved by an L-shaped ground plane slot. Both simulated and measured results demonstrate that the design is a very good candidate for mobile diversity and MIMO applications. The second investigation area concerns multiple element antenna (MEA) systems for wideband and multiband handset applications. It includes the following contributions: • Three antenna systems of the planar inverted-L (PILA) antenna (h = 5 mm) are employed for wideband handset diversity applications over the frequency range of 1.7 – 2.85 GHz: 1) The first design has a dual-element PILA in which both the pattern and spatial diversities are employed; one antenna element is located on the upper edge of the ground plane while the other is located on the lower edge. 2) The second design represents a more compact dual-element PILA antenna in which the two elements are placed on the same ground plane edge (collocated on the same edge). The antenna isolation is achieved using a parasitic decoupling element inserted between the two elements. A novel approach for the design of the parasitic decoupling element is proposed. It is based on stepped impedance resonator circuit theory. As a result, more space is saved with this design (footprint = 385 mm2) over the first design (footprint = 702 mm2). 3) The third design is a four-element PILA system in which two antenna pairs (one pair at the upper edge which the other pair is located on the lower edge on the system PCB). All the prototypes are made and evaluated; the results show excellent diversity performance over the applications in the frequency range of 1.7-2.7 GHz. • A dual-element hexa-band antenna is proposed for smartphone MIMO applications. It consists of two elements: a hexa-band metallic frame antenna and a hepta-band PILA antenna coupled with a meandered shorted strip as an internal antenna. The isolation is achieved due to the resulted orthogonal radiation patterns, especially, at 0.85 GHz. The optimized antenna is made and tested and the results show that this design covers a hexa-band and is particularly suitable for GSM850/ DCS1800/ PCS1900/ UMTS2100/ LTE2500/ LTE3600 smartphone applications

Positioning of a wireless relay node for useful cooperative communication

Given the exorbitant amount of data transmitted and the increasing demand for data connectivity in the 21st century, it has become imperative to search for pro-active and sustainable solutions to the effectively alleviate the overwhelming burden imposed on wireless networks. In this study a Decode and Forward cooperative relay channel is analyzed, with the employment of Maximal Ratio Combining at the destination node as the method of offering diversity combining. The system framework used is based on a three-node relay channel with a source node, relay node and a destination node. A model for the wireless communications channel is formulated in order for simulation to be carried out to investigate the impact on performance of relaying on a node placed at the edge of cell. Firstly, an AWGN channel is used before the effect of Rayleigh fading is taken into consideration. Result shows that performance of cooperative relaying performance is always superior or similar to conventional relaying. Additionally, relaying is beneficial when the relay is placed closer to the receiver

Reconfigurable Microwave Semiconductor Plasma Antenna

Reconfigurable antennas have been a subject of rapidly increased interest during the past decades. This has been prompted by the increased demand on new wireless communications technology in both civilian and military directions. Moreover, different types of reconfigurations have been identified and investigated to keep up with the demand for new technologies. In this research, the possibility of designing reconfigurable Dielectric Resonator Antennas (DRAs) have been explored with different types of reconfigurability directions, especially with the increased interest in the area of DRAs during the past three decades. These results have been satisfactory in general. The main aim of this research is to experiment with different reconfigurability designs, each purpose is to achieve one type of reconfigurability or more. This includes, polarisation reconfigurability in Chapter Three, frequency agility in Chapters Four and Five, beam steering and gain agility in Chapter Five. Furthermore, this research main aim has been to investigate new ways to exploit the advantages of the semiconductor plasma in reconfigurable antennas. However, research’s limited resources led to reduce the efforts in this area to only one experiment, which is presented in Chapter Six, based on a similar design presented in Chapter Four. Although the results have been conflicted for the last experiment, the results shown that the used reconfigurability medium (AlGaN/GaN HFETs) can be benefitted better from it in other application. Two models have been introduced for polarisation reconfigurability, a hemispherical DRA couple with reconfigurable annular slot excitation, and a notched rectangular DRA with reconfigurable parasitic strip(s). Both designs shown the possibility of achieving LP/CP radiations. In addition, rectangular DRAs that are excited with single, as well as multiple, slot have been studied. Prototypes have been built and measured with reasonable agreement between practical and simulated results. Furthermore, the work has been extended to study a reconfigurable DRA linear array where several designs have been investigated including single and dual-slot for two and four-element linear arrays. The single-slot model reconfiguration resulted in the expected beam steering alongside the array direction. On the other hand, both frequency tuning and beam steering have been achieved with the dual-slots models. Finally, the semiconductor plasma reconfigurable antennas have been considered with the investigation of AlGaN/GaN HFETs as a replacement for the well investigated and presented silicon SPIN diodes. The prototype has been measure and discrepancies between measurements and simulations have been discussed