Handbook of Ultra-Wideband Short-Range Sensing E-Book

Jürgen Sachs

• Herausgeber: Wiley-VCH
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 1260

Veröffentlichungsjahr: 2013

Beschreibung

Ranging from the theoretical basis of UWB sensors via implementation issues to applications, this much-needed book bridges the gap between designers and appliers working in civil engineering, biotechnology, medical engineering, robotic, mechanical engineering, safety and homeland security. From the contents: * History * Signal and systems in time and frequency domain * Propagation of electromagnetic waves (in frequency and time domain) * UWB-Principles * UWB-antennas and applicators * Data processing * Applications

Leseprobe

Contents

Cover

Related Titles

Title Page

Copyright

Preface

List of Contributors

Chapter 1: Ultra-Wideband Sensing – An Overview

1.1 Introduction

1.2 Ultra-Wideband – Definition and Consequences of a Large Bandwidth

1.3 A Brief History of UWB Technique

1.4 Information Gathering by UWB Sensors

References

Chapter 2: Basic Concepts on Signal and System Theory

2.1 Introduction

2.2 UWB Signals, Their Descriptions and Parameters

2.3 Some Idealized UWB Signals

2.4 Formal Description of Dynamic Systems

2.5 Physical System

2.6 Measurement Perturbations

2.7 Summary

References

Chapter 3: Principle of Ultra-Wideband Sensor Electronics

3.1 Introduction

3.2 Determination of the System Behaviour by Pulse Excitation

3.3 Determination of the System Behaviour by Excitation with Pseudo-Noise Codes

3.4 Determination of the System Behaviour by Excitation with Sine Waves

3.5 The Multi-Sine Technique

3.6 Determination of the System Behaviour with Random Noise Excitation

3.7 Measuring Arrangements

3.8 Summary

References

Chapter 4: Ultra-Wideband Radar

4.1 Introduction

4.2 Distributed System – the Measurement Problem

4.3 Plane Wave and Isotropic Waves/Normalized Wave

4.4 Time Domain Characterization of Antennas and the Free Space Friis Transmission Formula

4.5 Indirect Transmission Between Two Antennas – The Scalar Time Domain Radar Equation

4.6 General Properties of Ultra-Wideband Antennas

4.7 Basic Performance Figures of UWB Radar

4.8 Target Detection

4.9 Evaluation of Stratified Media by Ultra Wideband Radar

4.10 Ultra-Wideband Short-Range Imaging

References

Chapter 5: Electromagnetic Fields and Waves in Time and Frequency

5.1 Introduction

5.2 The Fundamental Relations of the Electromagnetic Field

5.3 Interaction of Electromagnetic Fields with Matter

5.4 Plane Wave Propagation

5.5 The Hertzian Dipole

5.6 Polarimetric Friis Formula and Radar Equation

5.7 The Concept of Green's Functions and the Near-Field Radar Equation

References

Chapter 6: Examples and Applications

6.1 Ultra-Wideband Sensing – The Road to New Radar and Sensor Applications

6.2 Monolithically Integration of M-Sequence-Based Sensor Head

6.3 Dielectric UWB Microwave Spectroscopy

6.4 Non-Destructive Testing in Civil Engineering Using M-Sequence-Based UWB Sensors

6.5 UWB Cardiovascular Monitoring for Enhanced Magnetic Resonance Imaging

6.6 UWB for Medical Microwave Breast Imaging

6.7 M-Sequence Radar Sensor for Search and Rescue of Survivors Beneath Collapsed Buildings

6.8 Multiple Moving Target Tracking by UWB Radar Sensor Network

6.9 UWB Localization

References

Appendix

Symbols and Abbreviations

Index

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Preface

Ultra-wideband (UWB) sensors exploit the manifold interactions between electromagnetic fields and matter. They aim at gaining information about a target, the environment, a technical process, or a substance by remote, non-destructive, continuous and fast measurement procedures. The applied sounding waves are of low power (typically thousand times less than the radiation of a mobile phone) and their frequencies range within the lower gigahertz domain. This enables acceptable wave penetration into optically opaque objects. Furthermore, the electromagnetic waves are harmless due to their low power and they are non-ionizing. This makes ultra-wideband sensors attractive for many short-range sensing tasks covering industrial, medical, security and rescue issues of detection, recognition, tracking, surveillance, quality control and so on.

Electromagnetic sounding is an inverse and indirect approach to gather information about the objects of interest. Inverse and indirect methods – independent of the underlying physical principles – are always prone to ambiguities with unwanted objects or events. The reduction of such cross-sensitivity needs diversity in data capturing in order to comprise preferably orthogonal interaction phenomena into data interpretation, data fusion and decision. Restricting to the determination of purely electrical properties, some ways to increase the diversity of data capturing consist of (a) measuring over a large frequency band, (b) measuring at many points in space, (c) observing the evolution of the scenario over a long time and (d) respecting the vector nature of the electromagnetic field by including polarimetric data. In addition, the measurement of non-electric properties may further reduce the ambiguities. However, we will exclude non-electric measurements from our discussions here. As is clear from the title of the book itself, it is point (a) that will be in the foreground of our interest, giving an outline of this book without losing however our other important viewpoints.

With a few exceptions, the classical electrical engineering is ‘narrowband’. This has not only historical but also theoretical roots. One, essentially by theory-motivated reason, to deal with narrowband (i.e. ‘gently’ modulated sine wave) signals is the property of a sine wave to keep its time evolution by interacting with a (linear) object. This reduces and simplifies theoretical evaluations to (not necessarily facile) magnitude and phase calculations and accelerates numerical computations. But corresponding considerations presume steady-state conditions which often obscure the intuitive understanding of the occurring processes.

Short pulses count to the class of wideband signals that are of major interest here. They are traditionally used in ultra-wideband technique. Pulse propagation is easy to comprehend. However, such signals are subjected to a modification of their time shape if interacting with an object or propagating in a lossy medium. These time shape variations are our major source of information about the objects of interest, but they are also more demanding with respect to modelling and mathematical treatment.

The propagation of time-extended wideband signals (e.g. random or pseudo-random signals) is intuitively less comprehensive, though the technical implementation of related sensor electronics provides some advantages in favour of pulse systems. In order to retrieve the illustrative understanding of wave propagation, we will trace back such signals to impulse-like time functions which can be handled like real pulses for our scope of application.

The purpose of this book is to give an overview of theoretical, implementation and application aspects of low-power – and hence short-range – ultra-wideband sensing. Intended readers are students, engineers and researches with a background in undergraduate level of mathematics, signal and system theory, electric circuit theory and electromagnetic wave propagation. The introductory part of the book introduces the definition of the UWB term and it gives a short overview of UWB history, the radiation regulations, possible fields of application and the basic approach of information gathering by UWB sensors.

Chapter 2 defines characteristic functions and parameters and summarizes basic concepts of signal and system theory which are important for the understanding of functioning of UWB sensors and their applications. It is mainly targeted at the less experienced reader in this field. Numerous figures are inserted to illustrate the basic relations and, in addition, an annex available at Wiley homepage (http://www.wiley-vch.de, search for ISBN 978-3-527-40853-5) provides a collection of useful mathematical rules, properties of signal transformations, and some basic considerations on signals and elementary signal operations. Furthermore, the reader can also find also some colored figures here and a couple of movies which complement several figures to better illustrate three-dimensional data sets.

Chapter 3 deals with the different concepts of UWB sensing electronics and their key properties. Developments within the last decade educe new and improved sensor principles allowing manufacturing inexpensive, monolithically integrated, lightweight and small microwave devices. They are prerequisites to pave the way for UWB sensing from laboratory to the field.

Chapter 4 discusses some peculiarities of UWB radar whose physical principle is indeed the same as for the ‘traditional’ radar, but the large fractional bandwidth requires some extensions and specifications of the classical radar theory. They are mainly required by the fact that achievable UWB resolutions may be far better than the geometric size of involved bodies as antennas and targets. The considerations are focused on wideband aspects of wave propagation but they are restricted to a simplified model of scalar waves.

In Chapter 5, the actual vector character of the electromagnetic wave and some of its implications are briefly treated, introducing some basic time domain models of wave propagation.

In the final chapter, some selected aspects of sensor implementation and application are discussed. These topics are contributed by several co-authors who were cooperating with me in numerous UWB projects during the last years.

I take this opportunity to thank all these co-authors and ancient project collaborators, institutions and companies for their fruitful work and pleasant collaboration. These projects and consequently this book could not have been possible without the chance to work on interesting tasks of the ultra-wideband technique at Ilmenau University of Technology and without the encouragement and support of many of the colleagues from research and technical staff as well as the administration. In particular, I would like to thank my colleagues at Electronic Measurement Research Lab for their support, engagement and productive interaction. I also owe a great deal to Stephen Crabbe who promoted and managed our first projects which bred the ultra-wideband M-sequence approach. The support of our research from the German Science Foundation (DFG) through the UKoLoS Program and also from various national and European projects is gratefully acknowledged. I am indebted to Valerie Molière of Wiley-VCH Verlag GmbH for inviting me to write this book and to Nina Stadthaus for her help and patience with any delays and project modifications. Thanks are due to Vibhu Dubey from Thomson Digital for manuscript corrections and typesetting. Last but not least, I am deeply grateful to my wife and my family, who displayed such appreciation, patience, support and love while I was occupied with this book.

Even if the extent of the book largely exceeds the initial intention, the text is by no means complete and all-embracing. In order to limit the number of pages and to complete the work in a reasonable amount of time, some decisions had to make what topics could be appropriate and what subjects could be omitted or reduced in the depth of their consideration. I may only hope that the reader can identify with my decision and that the work of the many researchers in the field of ultra-wideband technique is adequately appreciated. Clearly, the blame for any errors and omissions lies with the author. Let me know if you encounter any.

Jürgen Sachs

Schmiedefeld, Germany

August 2012

List of Contributors

Frank Bonitz

Materialforschungs- und -prüfanstalt

Weimar an der Bauhaus-Universität Weimar (MFPA)

Coudraystraße 9

D-99423 Weimar

Germany

Frank Daschner

University of Kiel

Technical Faculty

Institute of Electrical Engineering and Information

Engineering

Microwave Group

Kaiserstrasse 2

24143 Kiel

Matthias A. Hein

Ilmenau University of Technology

RF and Microwave Research Laboratory

P.O. Box 100565

98684 Ilmenau

Germany

Marko Helbig

Ilmenau University of Technology

Electronic Measurement Research Lab

P.O.Box 100565

98684 Ilmenau

Germany

Ralf Herrmann

Ilmenau University of Technology

Electronic Measurement Research Lab

P.O.Box 100565

98684 Ilmenau

Germany

Michael Kent

University of Kiel

Technical Faculty

Institute of Electrical Engineering and Information Engineering

Microwave Group

Kaiserstrasse 2

24143 Kiel

Martin Kmec

Ilmenau University of Technology

Electronic Measurement Research Lab

P.O.Box 100565

98684 Ilmenau

Germany

Reinhard Knöchel

University of Kiel

Technical Faculty

Institute of Electrical Engineering and Information Engineering

Microwave Group

Kaiserstrasse 2

24143 Kiel

Dušan Kocur

Technická univerzita v Košiciach

Fakulta elektrotechniky a informatiky

Katedra elektroniky a multimediálnych telekomunikácií

Letná 9

041 20 Košice

Slovenská republika

Olaf Kosch

Physikalisch-Technische Bundesanstalt (PTB)

Abbestraße 2-12

10587 Berlin

Germany

Jana Rováková

Technická univerzita v Košiciach

Fakulta elektrotechniky a informatiky

Katedra elektroniky a multimediálnych telekomunikácií

Letná 9

041 20 Košice

Slovenská republika

Jürgen Sachs

Ilmenau University of Technology

Electronic Measurement Research Lab

P.O. Box 100565

98684 Ilmenau

Germany

Ulrich Schwarz

BMW Group

Entertainment and Mobile Devices

Max-Diamand-Straße 15–17

80937 Munich, Germany

Francesco Scotto di Clemente

Ilmenau University of Technology

RF and Microwave Research Laboratory

P.O. Box 100565

98684 Ilmenau

Germany

Frank Seifert

Physikalisch-Technische Bundesanstalt (PTB)

Abbestraße 2-12

10587 Berlin

Germany

Florian Thiel

Physikalisch-Technische Bundesanstalt (PTB)

Abbestraße 2-12

10587 Berlin

Germany

Daniel Urdzík

Technická univerzita v Košiciach

Fakulta elektrotechniky a informatiky

Katedra elektroniky a multimediálnych

telekomunikácií

Letná 9

041 20 Košice

Slovenská republika

Egor Zaikov

Institute for Bioprocessing and Analytical Measurement

Techniques e.V.

Rosenhof

37308 Heilbad Heiligenstadt

Germany

Rudolf Zetik

Ilmenau University of Technology

Electronic Measurement Research Lab

P.O. Box 100565

98684 Ilmenau

Germany

1

Ultra-Wideband Sensing – An Overview

1.1 Introduction

For the human beings (and most of the animals), the scattering of electromagnetic waves, for example the scattering of sunlight at trees, buildings or the face of a friend or an enemy, is the most important source to gain information on the surroundings. As known from everybody's experience, the images gained from light scattering (i.e. photos) provide a detailed geometrical structure of the surroundings since the wavelengths are very small compared to the size of the objects of interest. Furthermore, the time history of that ‘scattering behaviour’ gives us a deep view inside the nature of an object or process. However, there are many cases where light scattering fails and we are not able to receive the wanted information by our native sense. Therefore, technical apparatuses were created which use different parts of the electromagnetic spectrum as X-rays, infrared and Terahertz radiation or microwaves exploiting each with specific properties of wave propagation.

Ultra-wideband (UWB) sensors are dealing with microwaves occupying a very large spectral band typically located within the lower GHz range. On the one hand, such waves can penetrate most (non-metallic) materials so that hidden objects may be detected, and on the other hand, they provide object resolution in the decimetre, centimetre or even millimetre range due to their large bandwidth. Moreover, polar molecules, for example water, are showing relaxation effects within these frequency bands which give the opportunity of substance characterization and validation. In general, it can be stated that a large bandwidth of a sounding signal provides more information on the object of interest.

With the availability of network analysers and the time domain reflectometry (TDR) since the 60th of the last century, very wideband measurements have been established but they were banned to laboratory environments. New and cheaper solutions for the RF-electronics, improved numerical capabilities to extract the wanted information from the gathered data and the effected ongoing adaptation of radio regulation rules by national and international regulation authorities allow this sensor approach to move stepwise in practice now. Ultra-wideband sensing is an upcoming technique to gather data from complex scenarios such as nature, industrial facilities, public or private environments, for medical applications, non-destructive testing, security and surveillance, for rescue operations and many more. Currently, it is hard to estimate the full spread of future applications.

The objective of this book is to introduce the reader to some aspects of ultra-wideband sensing. Such sensors use very weak and harmless electromagnetic sounding waves to ‘explore’ their surroundings. Sensor principles using electromagnetic waves are not new and are in use for many years. But they are typically based on narrowband signals. In contrast, the specific of UWB sensors is to be seen in the fact that they apply sounding signals of a very large bandwidth whereas bandwidth and centre frequency1 are of the same order.

Concerning their application there are four major consequences:

As a generic rule of thumb one can state that increasing frequency diversity leads to more information about the scenario under test. This observation is well respected by UWB sensors due to their large bandwidth. Hence they will have better resolution, lower cross-ambiguities or better recognition capabilities than their narrowband ‘brothers’.The spectral band occupied by UWB sensors is placed at comparatively low frequencies. Typical values are 100 MHz–10 GHz. This involves a good (reasonable) penetration of the sounding wave in many materials (except metal) which makes such sensors useful to investigate opaque objects and detect hidden targets.In the past, UWB techniques were largely banned to the laboratory due to the need of bulky and expensive electronic devices. But recent developments in RF-system and antenna design, RF-circuit integration and digital signal processing promote the step from the laboratory into the real world. Costs, robustness and power consumption of the sensor devices as well as reliability of the sensing method will be important aspects for the future application of UWB sensing.The large bandwidth of UWB devices causes inevitably interferences with other electronic devices, that is mainly with classical narrowband radio services and with other UWB devices. Simply spoken, UWB sensors increase the background noise. In order to limit this noise, the maximum power emission of UWB devices is typically restricted to an interference level which is generally accepted for unintentional radiations of all electric devices. Exceptions are high-power devices for research or military purposes [1].

In this book, we will discuss various UWB sensing approaches exclusively based on low-power emission. The most applied and considered one is probably the radar principle which is meanwhile more than 100 years old. But so far most radar devices are working with a sounding signal of comparatively narrow bandwidth. Here, we will address specific features of very wideband systems because ‘Future Radar development must increase the quantity and quality of information for the user. The long-term objective is to provide radar sensing to aid human activities with new and unique capabilities. Use of UWB radar signals appears to be the most promising future approach to building radar systems with new and better capabilities and direct applications to civil uses and environmental monitoring [2]’.