Multifunctional MIMO Antennas: Fundamentals and Application

Fundamentals and Applications

Yadwinder Kumar, Shrivishal Tripathi, Balwinder Raj, Yadwinder Kumar, Shrivishal Tripathi, Balwinder Raj

• Publisher: CRC Press
• Year: 2022
• Print ISBN:
  9781032190341
• eBook ISBN:
  9781000589627
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

This book presents a comprehensive approach to antenna designs for various applications, including 5G communication, the internet of things (IoT), and wearable devices. It discusses models, designs, and developments of MIMO antennas, antenna performance measurement, 5G communication challenges and opportunities, and MIMO antennas for LTE/ISM applications. It covers important topics including mmWave antennas, antenna arrays for MIMO applications, reconfigurable/band-notched MIMO antennas, multiband MIMO antennas, wideband MIMO antennas, and fractal-based compact multiband hybrid antennas.

FEATURES

• Discusses antenna design optimization techniques in detail
• Covers MIMO antenna performance measurement, multiband MIMO antennas, and wideband MIMO antennas
• Discusses modeling, simulation, and specific absorption rate (SAR) analysis of antennas
• Provides applications including radio-frequency identification (RFID), wearable antennas, and antennas for IoT

Multifunctional MIMO Antennas: Fundamentals and Application is useful for undergraduate and graduate students and academic researchers in areas including electrical engineering, electronics, and communication engineering.

Chapter 1Introduction to fractal antennas and their role in MIMO applications

Biswajit Dwivedy and Tanmaya Kumar Das

DOI: 10.1201/​9781003290230-1

CONTENTS

• 1.1Introduction
• 1.2Fractal for antennas: The techniques and purpose
  • 1.2.1Advantages and disadvantages of fractal-based antennas
  • 1.2.2Popular fractal geometries used for antennas
    • 1.2.2.1Koch curve
    • 1.2.2.2Koch snowflake
    • 1.2.2.3Cantor set
    • 1.2.2.4Sierpinski gasket
    • 1.2.2.5Sierpinski carpet
• 1.3Design of fractal antennas
  • 1.3.1Recent advances in the design of fractal antennas
    • 1.3.1.1Wideband antennas
    • 1.3.1.2Ultra-wideband antennas
    • 1.3.1.3Multiband antennas
    • 1.3.1.4Wearable antennas
    • 1.3.1.5Antennas for RFID applications
• 1.4MIMO antennas using fractal geometry
  • 1.4.1Realization techniques
• 1.5Special fractal antennas
• 1.6Summary and conclusions
• References

1.1INTRODUCTION

Fractal geometry is based on the process of iteratively generating contours with interminable complicated fine structures. The word fractal was taken from the Latin term fractus, which is associated with the verb fangere, meaning “to split or break.” In 1970, B. B. Mandelbrot, a French mathematician, introduced the term fractal after his intense research on various irregular and fragmented geometrical shapes inspired by nature such as trees, snowflakes, ferns, and leaves. Later, the fractal geometries were used for a wide range of applications in different sectors of science and engineering. At the same time, fractals were implemented in antenna engineering as a means of imposing inherent self-similarity and self-affinity in order to model the complex geometrical structures of the antennas and achieve a massive improvement in their characteristics such as size miniaturization, multiband response, broadband, impedance matching, and stable radiation properties. Therefore, fractal-shaped antennas are classified as a special type of electromagnetic radiating structure where the overall dimension is composed of a set of replications of a specific geometry and each geometrical iteration occurs on a different scale [1, 2]. Although many mathematical formulations have been developed to represent various fractal shapes, there are no strict guidelines that can be considered suitable for all fractal geometries. Fractals can be characterized based on geometrical properties. Self-similarity is one of these characteristics; its presence indicates the whole geometry is formed by replicating the small structure on a diminished scale. Another important characteristic is self-affinity; its presence indicates the total geometry is generated by scaling the pieces differently in the X and Y directions. Here, the small portions of the geometry are not identical to the complete structure; rather, they are slanted or twisted in different scales, resulting in anisotropic transformations. Recently, the design and performance of planar antennas based on various fractal geometries like Koch, Sierpinski gasket, and Minkowski were comprehensively investigated in the literature [3–7]. In many communications [8–13], specialized fractal geometry–based microstrip antennas were also proposed to meet various contemporary wireless standards.

This chapter aims to provide a sound understanding of various fractal shapes, including the techniques of introducing fractal geometry of different orders over Euclidean geometry for fascinatingly perturbing the current distribution to make the antenna invariably different from the conventional ones. It also describes the use of fractals in multiple-input multiple-output (MIMO) terminal-based antennas and their effect on various parameters like impedance bandwidth (IBW), the envelope correlation coefficient (ECC), capacity loss, mutual coupling, and the spacing between the radiators implemented for various wireless applications.

1.2FRACTAL FOR ANTENNAS: THE TECHNIQUES AND PURPOSE

Fractal engineering comprises a class of topology-based miniaturization techniques by which characteristics like the geometry/configuration, surface current density distribution (electric or magnetic), and electrical dimensions of an antenna can be altered to improve its performance. In other words, fractals are space-filling geometries with a Hausdorff dimension that can accommodate relatively greater lengths within a much smaller area. This elemental concept, along with the self-similarity feature of fractal geometry, is effectively used by antenna engineers to create fractal antennas, which are superior to conventional antennas based on Euclidean geometry.

The fractal antenna can perform like a large antenna by reducing the area to a great extent. This can be understood from a simple example of a Koch dipole antenna. A Koch dipole antenna is formed by amending the straight-wire dipole antenna in an iterative process using a special mathematical formulation [14–16]. The detailed mathematical formulation of the Koch, along with those of other popular fractal shapes, is given in the next section of this chapter. As shown in Figure 1.1, the initial step of the Koch curve starts with a straight line (zeroth iteration), and the total length of the curve corresponding to the nth iteration is ${\left(4/3\right)}^n$ of the initial length. This implies that even if the Koch curve–based dipole has the same starting and ending points as the normal dipole, it has a physical length much greater than that of the ordinary one with a nether resonant frequency. The decrement of the resonant frequency of the Koch dipole with the increase in the iteration was investigated in [16]. It was highlighted that even after each iteration, where the overall length of the Koch fractal increases by 1/3 of the previous one, the resonant frequency does not decrease proportionately. This phenomenon can be explained by considering that the breaking of each fractal into smaller segments during each iteration lowers the resonant frequency while making the wa...

Table of contents

• Cover Page
• Half-Title Page
• Title Page
• Copyright Page
• Contents
• Preface
• Editors
• Contributors
• 1 Introduction to fractal antennas and their role in MIMO applications
• 2 Multiband hybrid fractal antennas for smart networks
• 3 Duplex antenna system for MIMO application
• 4 Comb-shaped microstrip patch antenna with defected ground structure for MIMO applications
• 5 Multiband MIMO antennas
• 6 MIMO antenna in UWB applications
• 7 Four-element wave patch multiband MIMO antenna for 5G application
• 8 5G communication challenges and opportunities: Shaping the future
• 9 Design challenges in planar printed MIMO antennas
• 10 Four-element dual-band MIMO antenna for Wi-Fi and WLAN applications
• 11 MIMO antenna applications: RFID, WLAN, wearable antennas, and IoT
• Index