Table Of ContentPrinciples and
Applications of
RF/Microwave in
Healthcare and
Biosensing
Principles and
Applications of
RF/Microwave in
Healthcare and
Biosensing
Edited by
Changzhi Li
Mohammad-Reza Tofighi
Dominique Schreurs
Tzyy-Sheng Jason Horng
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List of Contributors
M. Baboli
ColumbiaUniversity,NY, United States
O. Boric´-Lubecke
University ofHawaii, Manoa, HI, United States
J.-C. Chiao
University ofTexas atArlington,Arlington,TX, United States
R. Go´mez-Garcı´a
University ofAlcala´,Madrid, Spain
T.-S.J. Horng
NationalSun Yat-Sen University,Kaohsiung, Taiwan
C. Li
Texas Tech University, Lubbock, TX,UnitedStates
V. Lubecke
University ofHawaii, Manoa, HI, United States
M. Mercuri
Holst Centre,IMEC,Eindhoven, Netherlands
J.-M.Mun˜oz-Ferreras
University ofAlcala´,Madrid, Spain
J. Oberhammer
KTH Royal InstituteofTechnology,Stockholm, Sweden
A. Rahman
University ofHawaii, Manoa, HI, United States
D.M.M.-P. Schreurs
KU Leuven, Leuven,Belgium
M.-R. Tofighi
PennsylvaniaStateUniversity,Harrisburg, PA,UnitedStates
F. To¨pfer
KTH Royal InstituteofTechnology,Stockholm, Sweden
F.-K. Wang
NationalSun Yat-Sen University,Kaohsiung, Taiwan
xi
Introduction
BACKGROUND
Healthcare is a top global challenge due to the ever-increasing demand for higher
quality of life, the aging population, and the various social, cultural, political, and
economic impacts. While the productivity and stability of society are dependent
on the outcomes of healthcare, the rising costs of medical care are impacting
almost everyone in the world. Due to the aging of populations and the prevalence
of chronic diseases, there is a strong demand to use advanced technologies to
shoulder the burdens of individuals and healthcare systems in both developing
and developed countries.
In recent years, a significant growth of research that uses engineering innova-
tions to improve the efficacy while reducing the cost of health provision has been
taking place. Among these efforts, radio frequency (RF) and microwave technolo-
gies play a critical role in disease diagnosis, care delivery, and telemedicine.
Researchers have devoted a lot of efforts to the monitoring and imaging applica-
tions of RF/microwave technologies, some of which have entered or are being
tested for clinical use. They also apply wireless sensing and communication over
or through body tissues to transmit physiological or biochemical information. In
addition, based on the biological effects caused by electromagnetic waves inter-
acting with tissues, microwave diagnosis and treatment of diseases in living sys-
tems are under rapid development, generating significant impacts in fields such as
biosensing andhyperthermia.
Although RF/microwave engineering is a well-established discipline with
many applications such as wireless communication and wireless power transfer,
using RF/microwave technology for healthcare and biosensing involves special
grand challenges. Most conventional RF/microwave systems rely on electro-
magnetic waves that propagate in homogeneous and isotropic media. However,
when applying the same discipline to biomedical applications, tremendous puz-
zles are presented due to the anatomical, physiological, and biochemical varia-
tions in human bodies. Moreover, the problems are compounded by realistic
issues such as the lack of simulation models and experimental data, difficulty in
conducting tests because studies strongly depend on human subjects, unmeasur-
able effects in biological systems, difficulty unifying protocols and conducting
experiments, safety issues in human studies, as well as practical constraints in
clinical implementation. In addition, another barrier that is difficult to break is
the large gap between the languages and mindsets of engineers and healthcare
practitioners.
xiii
xiv Introduction
Therefore, there is a strong demand for both engineering and clinical research-
ers to understand the achievements and future directions in the development
of microwave technologies for the fast-growing biomedical fields. It is believed
that more clinical, pharmaceutical, and biochemical aspects can be addressed if
researchersandpractitionersfromdifferentfieldsaremadeawareofthemultitude
of possibilities, potential new applications, and challenges in future innovative
healthcare solutions.
RECENT PROGRESS ON RF/MICROWAVE
BIOMEDICAL RESEARCH
Important recent progress on RF/microwave biomedical research can be roughly
dividedintotwocategories. Oneis thebiological interaction andeffects;the other
is RF systemsand instrumentation for healthcare applications.
Researchers have been intensively studying the mechanisms, effects, and
applications of the interaction of electromagnetic waves with biological materials
at molecular, cellular, and tissue levels. On one hand, a large number of devices
and components on circuit-board and integrated-chip levels have been developed
for microwave characterization of biological materials and living systems. Based
on these devices, therapeutic and diagnostic applications have been proposed and
some of them are being clinically tested. Examples of typical applications include
the diagnosis of malignant tumors and lab on chip for real-time complex body
fluid analysis. On the other hand, RF/microwave energy is used to treat diseases
intherapeuticandsurgicalapplications. Examplesinclude hyperthermia andmini-
mally invasive natural orifice transluminal endoscopic surgery, which in general
can improve treatment efficiency, reduce pain, and shorten the recovery time for
patients.
In the meantime, there are abundant systems and instrumentations for health-
care applications developed based on RF/microwave technologies. Prime
examples are magnetic resonance imaging (MRI) and microwave imaging. MRI,
whose invention has been honored by several Nobel Prizes, has been widely
adopted in clinical practice to benefit the well-being of human society.
Microwave and millimeter-wave imaging have shown their advantages and daily
uses not only in health applications, but also in security systems. Another area
that has caught the attention of many researchers and practitioners is that of wire-
less sensors and systems for health monitoring and telemedicine. For example,
wireless signals are utilized to noninvasively measure physiological signals and
biological signals at doctors’ offices, in health-care facilities, or even at home;
they can also transmit signals between sensors and stimulators implanted in the
human body and external wearable controllers for further transmission, proces-
sing, and control, forming a closed-loop system for continuous and autonomous
management of disease symptoms.
Introduction xv
ABOUT THIS BOOK
This book aims to help authors learn the multiple directions in which RF/micro-
wave technologies are heading toward healthcare and biosensing applications, the
achievements that have been made so far, and the challenges for researchers to
solve in the near future. Chapter 1 by Li and Schreurs reviews the fundamentals
of microwave engineering, which will be used in the other chapters of this book.
Since microwave engineering is a discipline that has gone through many years of
development, Chapter 1 only illustrates basic knowledge and is aimed at helping
readers from other disciplines to understand the basic principles relevant to this
book. Therefore, readers with good microwave engineering background can skip
that chapter. In Chapter 2, Interaction between electromagnetic waves and biolog-
ical materials, by Tofighi, the modeling and measurement procedure for electro-
magnetic properties of biological materials, namely complex permittivity, is
described, which serves as the foundation for the interaction between RF/micro-
wave and biological materials. The chapter also covers issues related to interfac-
ing with tissue through sensing probes, such as coaxial, microstrip, and coplanar
waveguide transmission lines, providing a useful perspective that is beneficial to
some other medical and biological applications discussed in this book. Chapter 3,
Microwave cancer diagnosis, by To¨pfer and Oberhammer, focuses on microwave
diagnosis of malignant tumors, based on the fact that a special microwave signa-
ture has been observed for many malignant tumors. A multitude of techniques,
including free-space quasi-optical techniques, near-field probes, microwave
tomography, ultra-wideband radar, and passive microwave imaging, some of
which have already entered clinical trials, are presentedfor the diagnosisofbreast
cancer,skincancer,andbraintumors.Chapter 4,Wireless closed-loopstimulation
systems for symptom management, by Chiao, presents closed-loop systems for
autonomous management ofdisease symptoms, using examplesofneural andgas-
tric electrical stimulation applications that target the management of neurological
and gastric disorders. Wireless signal transduction and wireless power transfer
mechanisms across tissues make it possible to eliminate batteries in the implants
for long-term use and to reduce the implant size for endoscopic implementation.
As a result, these systems can provide better care for patients who have chronic
illness and improve the healthcare system with personalized medicine and lower
costs. Starting from Chapter 5, Human-aware localization using linear-frequency-
modulated continuous-wave radars, the rest of the book discusses biomedical
radars for various healthcare applications. In Chapter 5, Human-aware localiza-
tion using linear-frequency-modulated continuous-wave radars, Mun˜oz Ferreras,
Go´mez Garc´ıa and Li present coherent linear-frequency-modulated continuous-
wave radars. With a relatively simple hardware front-end, the solution is capable
of both relative displacement and absolute range measurements, thus enabling
versatile health care applications based on physiological motion sensing and
human-aware localization. Chapter 6, Biomedical radars for monitoring health, by
xvi Introduction
Wang, Mercuri, Horng, and Schreurs. discusses in more depth specific applica-
tions, such as vital signs monitoring, exercise assistance, and fall detection, show-
ing the wide applicability of injection-locked radar and step-frequency
continuous-wave radar. Finally, Chapter 7, RF/wireless indoor activity classifica-
tion, by Rahman, Boric´-Lubecke, Lubecke and Baboli, applies biomedical radar
to indoor activityclassification.
We hope that this book will inspire the readers to develop their own ideas to
leverage advanced RF/microwave technologies and devise innovative solutions in
the highlyimportant field to benefit the well-beingof allhuman beings.
We dedicate our respects to pioneers who started to apply RF/microwave
technologies to healthcare and biosensing. We would also like to sincerely
acknowledge the important supports provided by funding agencies, including
the Belgian National Fund for Scientific Research (FWO), the European Institute
of Innovation & Technology (EIT)—Health, the Ministry of Science and
Technology (MOST) ofTaiwan, and the USNational Science Foundation(NSF).
CHAPTER
1
Fundamentals of microwave
engineering
C.Li1and D.M.M.-P. Schreurs2
1TexasTechUniversity,Lubbock,TX,UnitedStates2KULeuven,Leuven,Belgium
CHAPTER OUTLINE
1.1 Introduction.........................................................................................................2
1.2 TransmissionLinesTheory...................................................................................3
1.2.1 ASimpleModelofTransmissionLines.................................................3
1.2.2 ImpedanceandReflectionCoefficient..................................................5
1.2.3 SpecialCasesofTransmissionLines....................................................6
1.2.4 VoltageStandingWaveRatio...............................................................8
1.3 RFMatrices.........................................................................................................9
1.3.1 MatricesforCircuitAnalysis................................................................9
1.3.2 S-Parameters...................................................................................10
1.3.3 ConversionAmongtheMatrices.........................................................13
1.4 SmithChart........................................................................................................13
1.4.1 ReflectionCoefficientontheSmithChart...........................................14
1.4.2 RelationshipBetweenReflectionCoefficientandImpedance................15
1.4.3 AdmittanceontheSmithChart..........................................................16
1.4.4 UsefulRulesofSmithChartandImpedance/AdmittanceCalculation....16
1.5 ImpedanceMatching..........................................................................................18
1.5.1 MatchingWithLumpedElements......................................................19
1.5.2 MatchingbyTransmissionLines........................................................20
1.5.3 MatchingbyaQuarter-WaveTransformer............................................21
1.6 MicrowavePassiveComponents.........................................................................22
1.6.1 Three-PortPowerCouplers................................................................22
1.6.2 Four-PortPowerCouplers..................................................................27
1.7 MicrowaveActiveCircuits..................................................................................28
1.7.1 Amplifiers:Gain,NoiseFigure,Linearity,Stability,andEfficiency........28
1.7.2 Mixers:ActiveVersusPassive,NoiseFigure,Linearity..........................40
1.7.3 Oscillators:OscillatorStructures,PhaseNoise....................................43
C.Li,M.Tofighi,D.SchreursandT-Z.J.Horng(Eds):PrinciplesandApplicationsofRF/Microwave 1
inHealthcareandBiosensing.
©2017ElsevierInc.Allrightsreserved.
2 CHAPTER 1 Fundamentals of microwave engineering
1.8 SystemArchitectures.........................................................................................47
1.8.1 HeterodyneArchitecture....................................................................47
1.8.2 HomodyneArchitecture.....................................................................48
1.8.3 DoubleSidebandArchitecture...........................................................48
1.8.4 DirectIFSamplingArchitectures.......................................................49
1.8.5 OtherArchitectures...........................................................................50
Acknowledgments.....................................................................................................50
References...............................................................................................................50
1.1 INTRODUCTION
The principles and applications of radio frequency (RF)/microwave in health-
care and biosensing are strongly based on the analysis, design, and use of
microwave components, circuits, and systems. “Microwave” refers to electro-
magnetic waves from 1 to 300GHz, while RF is normally defined as the elec-
tromagnetic wave frequencies from about 3kHz to 300GHz [1,2]. Therefore,
RF and microwave combined cover a very large range of the electromagnetic
spectrum and have many potential applications that interact with our daily life
from the cell level to the human body level. To help readers better understand
the analysis and the engineering techniques used in other chapters of this
book, fundamentals of microwave engineering are presented in this chapter.
The discussion starts from transmission lines, which are used in almost any
RF/microwave circuit to carry high-frequency signals. It will then review
S-parameters, which are the basic “language” for microwave measurements.
Based on that, the Smith Chart and impedance matching will be introduced as
important microwave circuits and systems design tools. With the help of these
tools, microwave passive components (e.g., power dividers, combiners, and
hybrids) and active building blocks (e.g., amplifiers, mixers, and oscillators)
will be discussed. Finally, some fundamental RF/microwave system architec-
tures will be presented.
If a reader has been trained with microwave knowledge, she/he can skip
this chapter. On the other hand, if the reader is from another discipline such as
a healthcare profession, reading this chapter would help her/him to understand
the technologies involved in various applications covered by the other chap-
ters. However, it should be noted that microwave engineering and systems is
based on a large engineering discipline that has gone through many years of
development. Therefore, the contents of this chapter only illustrate the basic
knowledge sets and principles. As readers go further into specific healthcare
and biosensing topics in other chapters, they are encouraged to use the refer-
ences or contact the chapter authors to get relevant information and sugges-
tions on self-learning methods for the corresponding microwave theory and
techniques topics.
