Multifunctional Ultrawideband Antennas

Trends, Techniques and Applications

Chinmoy Saha, Jawad Y Siddiqui, Y M M Antar

• Publisher: CRC Press
• Year: 2019
• ISBN:
  9781351026529
• Edition: 1
• Topic: Naturwissenschaften
• Subtopic: Physik

Multifunctional Antennas (MFA) are comparatively a new area for antenna research and finds applications in various modern wireless radios, like Cognitive Radio (CR) in Software Defined Radio (SDR) technology and MIMO technology. This book is first attempt and an invaluable resource which deals with the design and realization of various kinds of multifunctional antennas. After clearly explaining the exclusive features of MFAs, the book presents various designs of such antennas considering versatile modern and upcoming applications.

Written by three internationally known researchers, Multi-Functional Ultra Wideband Antennas: Trends, Techniques and Applications:

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• Provides a lucid introduction on UWB systems, historical perspective and discusses various applications of such systems

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• Discusses fundamentals of antennas and its characterization in time and frequency domains, primarily aimed for the beginners in the area

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• Revisits the design and realization of various classical UWB antennas

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• Discusses various techniques of designing frequency-notched UWB antennas and provide detailed comparison of the techniques

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• Deals with the techniques of deriving multiple antenna functionalities from a single antenna

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• Incorporates exclusive discussions on modern reconfigurable antennas and printed and dielectric resonator based MIMO antennas with clear focus on recent and upcoming technological requirements

With Multi-Functional Ultra Wideband Antennas: Trends, Techniques and Applications, antenna engineers, communication system engineers, graduate students, academic/industry researchers will gain a thorough knowledge on design of such antennas with clear physical insight and understanding.

Chinmoy Saha, PHD, is an associate Professor in the Department of Avionics at Indian Institute of Space Science and Technology, Thiruvananthapuram, Kerala, India. His current research interest includes Microwave Circuits, Engineered Materials, Metamaterial Inspired Antennas and Circuits, reconfigurable and multi-functional antennas for modern wireless applications, Dielectric Resonator antennas, THz antennas and wireless power transfer. He is the author or coauthor of several books, scientific journals and recipient of several prestigious awards.

Jawad Yaseen Siddiqui, PHD, is an associate Professor in the Department of Radio Physics and Electronics at University of Calcutta, Kolkata, India. His current research interest includes ultra-wideband antennas, frequency reconfigurable antennas, tapered slot antennas and multi-functional antennas for cognitive radio application. He is the author or coauthor of several books, scientific journals and recipient of prestigious awards. He is a Co-Principal Investigator on Stratosphere Troposphere (ST) Radar Project at the University of Calcutta, Kolkata, India.

Yahia M.M. Antar, PHD, is a Professor in the Department of Department of Electrical and Computer Engineering at the Royal Military College of Canada, Kingston, ON, Canada. He is the author or coauthor of several books, scientific journals and recipient of prestigious awards which includes IEEE-Antennas and Propagation Society prestigious Chen-To-Tai Distinguished Educator Award for 2017, 2015 IEEE Canada J. M. Ham outstanding Engineering Education Award, 2014 IEEE Canada RA Fessenden Silver Medal, 2012 Queen's Diamond Jubilee Medal from the Governor General of Canada and many more.

1

Introduction to UWB Systems and Applications

1.1 Introduction

As the name suggests, the term ultrawideband (UWB) system corresponds to a commercial (military/civilian) communication system which utilizes a very wide frequency spectrum. While the basic definition of bandwidth¹ in a general electrical engineering context is applicable to an UWB system, it can be quantified in terms of absolute (f _h -f _l ), percentage (f _h -f _l )/f × 100 or ratio bandwidth (f _h /f _l ), where f _h and f _l are upper and lower frequencies of the UWB spectrum. Using the complementary relation of time and frequency domain, governed by Fourier transform, the UWB system can also be treated as a communication system employing very narrow pulses of duration in the range of nanosecond and sub-nano second. Thus, communicating (transmit/receive) over a very wide frequency range employing extremely narrow pulses (time duration) is the key feature of a UWB system in general. This feature enables the UWB technology to support transmission of high data rates of the order of 100 MBPS or even higher. Apart from providing faster communication with high data rates, UWB technology has various interesting features which have made it a unique tool for various applications, ranging from UWB radar to ground-penetrating radar (GPR) and biomedical imaging. Very large bandwidth of the UWB signal offers various advantages such as high data rate, lower power consumption, high time resolution, obstacle penetration capability, and most importantly, low-cost implementation. Since the UWB system occupies a very wide bandwidth, its spectrum naturally overlaps with various traditional narrowband services. To support these narrowband services simultaneously, the UWB system is operated at a very low power level. Simultaneous operation of UWB and various narrowband inside this UWB band is, recently, being used for dynamic spectrum sharing in cognitive radio (CR) of software-defined radio (SDR). This CR-based SDR and multiple input and multiple output (MIMO) systems are very recent applications of UWB technology.

In this chapter, we focus on an overall introduction to the UWB system, including an historical perspective through to the most recent applications of UWB technology. Chronological growth of the UWB technology, starting from the spark-gap realization of electromagnetic waves by Heinrich Hertz [1], is systematically presented with a special emphasis on landmark inventions/achievements in the area. An introductory definition of UWB systems and various schemes to realize UWB technology, followed by a discussion on spectrum regulation and applications, provide readers, in particular those new to this area, with solid background information.

1.2 An Overview of the UWB Systems

One of the motivations behind and benefits of the UWB systems can be excellently corroborated by Shannon’s channel capacity formula [2] for a band-limited channel with Gaussian noise,

$$\text{Channel}\text{capacity},C=B{\log }_{10}\left(1+\frac{S}{BN{}_0}\right)$$

(1.1)

where:

Bis the bandwidth of the channel (Hz)

Sis the signal power (Watt)

N ₀is the channel spectral density of Noise (Watt/Hz)

Shannon’s formula of Equation 1.1 indicates that for a given N ₀ , channel capacity C can be maintained to a fixed value by decreasing signal power level and increasing the bandwidth. On the other hand, for a given (S/N ₀ ), channel capacity C increases with the bandwidth. Though Shannon’s capacity theorem is more widely used in information theory [3], its implications are extremely encouraging for wideband systems, such as spread spectrum techniques and UWB.

Formal Definition of UWB Systems

• UWB system was first formally defined in 1990 by the Defense Advanced Research Project Agency (DARPA) [4]. According to this definition, any system occupying a fractional bandwidth greater than or equal to 0.25 is categorized as a UWB system. Thus, according to DARPA, a system operating over a bandwidth (BW),

$$BW=\frac{f_h-f_l}{f_c}=\frac{2(f_h-f_l)}{f_h+f_l}\ge 0.25$$

(1.2)

is called a UWB system. Here, f _h and f _l are the higher and lower end of UWB band respectively and f _c = (f _h + f _l )/2 is the center frequency.

• In 2003, the Federal Communications Commission (FCC) [5] modified the fractional bandwidth limit to 0.2 instead of 0.25 defined by DARPA. Thus, according to the FCC, a UWB system should have a fractional bandwidth given by,

$$BW=\frac{f_h-f_l}{f_c}=\frac{2(f_h-f_l)}{f_h+f_l}\ge 0.2$$

(1.3)

Alternatively, as per FCC regulation, any system having an absolute bandwidth greater than or equal to 500 MHz is referred to as a UWB system. This definition of a UWB system,

$$BW=f_h-f_l\ge 500\text{MHz}$$

(1.4)

is applicable when the center frequency is above 6 GHz.

In the definition of a UWB system, f _h and f _l are the upper and lower end of the UWB band respectively, where the radiated power is 10 dB down on the peak level.

In 2002, the FCC designated a 7.5 GHz band ranging from 3.1 to 10.6 GHz in the USA for UWB communications. Even though various other agencies/bodies adopted different bands for UWB communication, 3.1 to 10.6 GHz is very popular and almost universally accepted as the modern UWB band. Spectrum allocation for UWB and associated regulation will be discussed in more detail in Section 1.2.3.

1.2.1 History of UWB

Research on UWB systems including UWB radar, antennas and communication have drawn a great deal of attention over the last two decades, more specifically since 2002 after the FCC’s regulation on exclusive spectrum allocation for UWB. However, the origin of UWB signal and UWB technology dates to 1888 when Heinrich Hertz (1857–1894) generated a short pulse using his famous spark-gap transmitter [1]. Though the short pulse generated by Hertz was the first laboratory-generated UWB signal, at that time it was not very useful because the focus of radio engineers was more on the narrowband systems to exploit maximum benefit of frequency division multiplexing. Before we start our journey on modern UWB systems, it would be interesting to briefly look back on some of the pioneers of radio wave. Table 1.1 summarizes the landmark contributions by Heinrich Hertz, Oliver Lodge, Jagadish Chandra Bose and Guglielmo Marconi, who are considered the four pioneers of electromagnetic engineering. Though Hertz’s spark-gap excited short pulses are inherently UWB signals in nature and some of the antennas proposed by Lodge and Bose are popular modern wideband antennas, UWB technology was left almost dormant for several decades. The obstacles o...

Table of contents

• Cover
• Half-Title
• Title
• Copyright
• Contents
• About the Authors
• Preface
• 1 Introduction to UWB Systems and Applications
• 2 Design and Developments of UWB Antennas
• 3 Frequency-Notched UWB Antenna Design
• 4 UWB Antennas for Multi-Functional Operations
• 5 Reconfigurable UWB Antennas Design
• 6 UWB MIMO Antennas
• Index