Stepped-Frequency Radar Sensors: Theory, Analysis and Design

133 Pages·2016·4.516 MB·English

by  Cam Nguyen, Joongsuk Park (auth.)

SPRINGER BRIEFS IN
ELECTRICAL AND COMPUTER ENGINEERING
Cam Nguyen
Joongsuk Park
Stepped-
Frequency Radar
Sensors
Theory, Analysis
and Design
123
SpringerBriefs in Electrical and Computer
Engineering
More information about this series at http://www.springer.com/series/10059
Cam Nguyen Joongsuk Park
(cid:129)
Stepped-Frequency Radar
Sensors
Theory, Analysis and Design
123
CamNguyen JoongsukPark
Texas A&MUniversity Digital Media R&D Center
CollegeStation, TX SamsungElectronics Co.,Ltd.
USA Suwon
Korea,Republic of (SouthKorea)
ISSN 2191-8112 ISSN 2191-8120 (electronic)
SpringerBriefs inElectrical andComputer Engineering
ISBN978-3-319-12270-0 ISBN978-3-319-12271-7 (eBook)
DOI 10.1007/978-3-319-12271-7
LibraryofCongressControlNumber:2016935214
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Preface
Stepped-frequency radar sensors are attractive for various surface and subsurface
sensing applications. Stepped-frequency systems transmit consecutive trains of
continuous-wave signals at different frequencies that are separated by a fixed
amount. The unique characteristic of stepped-frequency systems is, although they
workasfrequency-basedsystems,theirfinalresponseisdescribedinatime-domain
quantity, namely “synthetic pulse,” which contains the information about targets.
This unique “synthetic pulse” product enables stepped-frequency radar sensors to
have some of the advantages of impulse-based ultra-wideband (UWB) systems,
which operate completely in the time domain, such as ease in identification and
characterization of adjacent targets. Specifically, stepped-frequency radar sensors
have several major advantages. First, they have a very narrow instantaneous
bandwidth at each frequency, resulting in less receiver’s noise figure and hence
increased sensitivity and dynamic range. Second, their absolute RF operating
bandwidth, on the other hand, can be very wide, leading to fine range resolution.
Third, they can transmit high average power enabling long range or deep pene-
tration. Fourth, it is possible to properly shape the transmitted spectrum by trans-
mittingconstituentsignalswithcertainamplitudesandphases,helpingimprovethe
system’s performance and possibly compensate for inevitable effects due to sys-
tem’s imperfection and operating environment. Stepped-frequency radar sensors
findnumerousapplicationsformilitary,security,civilian,commerce,medicine,and
healthcare.
This book presents the theory, analysis, and design of stepped-frequency radar
sensors and their components. Specifically, it addresses the following main topics
of stepped-frequency radar sensors: system analysis, transmitter design, receiver
design, antenna design, and system integration and test. It also presents the
development of two practical stepped-frequency radar sensors and their transmit-
ters,receivers,antennas,signalprocessing,integrations,electricaltests,andsensing
measurements, which serve as an effective way to demonstrate not only the anal-
ysis, design, test, and sensing applications of stepped-frequency radar sensors, but
also the design of constituent components. Although the book is succinct,
v
vi Preface
the material is very much self-contained and contains practical, valuable, and
sufficient information presented in such a way that allows readers with an under-
graduatebackgroundinelectricalengineeringorphysics,withsomeexperiencesor
graduate courses in microwave circuits, to understand and design easily
stepped-frequency radar sensors and their transmitters, receivers, and antennas for
various sensing applications.
Thebookisusefulforengineers,physicists,andgraduatestudentswhoworkin
radar,sensor,andcommunicationsystemsaswellasthoseinvolvedinthedesignof
RF circuits and systems. It is our hope that the book can serve not only as a
reference for the development of stepped-frequency systems and components, but
also for possible generation of ideas that can benefit many existing sensing appli-
cations or be implemented for other new applications.
College Station, TX; Newport Beach, CA, USA Cam Nguyen
Seoul, South Korea Joongsuk Park
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Impulse Radar Sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 FMCW Radar Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 SFCW Radar Sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 General Analysis of Radar Sensors. . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2 Signal Propagation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.1 Maxwell’s Equations and Wave Equations . . . . . . . . . . . 10
2.2.2 Propagation Constant, Loss and Velocity . . . . . . . . . . . . 11
2.3 Scattering of Signals Incident on Targets . . . . . . . . . . . . . . . . . 16
2.3.1 Scattering of Signals on a Half-Space. . . . . . . . . . . . . . . 16
2.3.2 Radar Cross Section. . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.4 System Equations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.4.1 Friis Transmission Equation . . . . . . . . . . . . . . . . . . . . . 23
2.4.2 Radar Equation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.5 Signal-to-Noise Ratio of Systems. . . . . . . . . . . . . . . . . . . . . . . 28
2.6 Receiver Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.7 Performance Factor of Radar Systems. . . . . . . . . . . . . . . . . . . . 32
2.8 Radar Equation and System Performance Factor for Targets
Involving Half-Spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.9 Radar Equation and System Performance Factor for Buried
Objects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.10 Targets Consisting of Multiple Layers and Buried Objects . . . . . 37
2.11 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3 Stepped-Frequency Radar Sensor Analysis . . . . . . . . . . . . . . . . . . . 39
3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.2 Principle of Stepped-Frequency Radar Sensors. . . . . . . . . . . . . . 39
3.3 Design Parameters of Stepped-Frequency Radar Sensors. . . . . . . 46
3.3.1 Angle and Range Resolution. . . . . . . . . . . . . . . . . . . . . 47
3.3.2 Range Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
vii
viii Contents
3.3.3 Ambiguous Range. . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.3.4 Pulse Repetition Interval. . . . . . . . . . . . . . . . . . . . . . . . 55
3.3.5 Number of Frequency Steps . . . . . . . . . . . . . . . . . . . . . 56
3.4 System Performance Factor. . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.5 Estimation of Range or Penetration Depth. . . . . . . . . . . . . . . . . 59
3.5.1 Estimation of Penetration Depth in Multi-layer
Targets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.5.2 Estimation of Penetration Depth for Buried Targets . . . . . 62
3.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4 Development of Stepped-Frequency Continuous-Wave Radar
Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.2 SFCW Radar Sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
4.2.1 Quadrature Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.2.2 Millimeter-Wave SFCW Radar Sensor Transceiver . . . . . 74
4.2.3 Microwave SFCW Radar Sensor Transceiver . . . . . . . . . 78
4.2.4 Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.2.5 Signal Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
4.2.6 Compensation for the I/Q Errors . . . . . . . . . . . . . . . . . . 91
4.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5 Characterizations and Tests of Stepped-Frequency
Continuous-Wave Radar Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.2 Electrical Characterizations of Developed Stepped-Frequency
Radar Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
5.2.1 Microwave SFCW Radar Sensor. . . . . . . . . . . . . . . . . . 100
5.2.2 Millimeter-Wave SFCW Radar Sensor. . . . . . . . . . . . . . 103
5.3 Tests of the Millimeter-Wave SFCW Radar Sensor . . . . . . . . . . 105
5.3.1 Measurement of Surface Profiles . . . . . . . . . . . . . . . . . . 106
5.3.2 Measurement of Liquid Levels . . . . . . . . . . . . . . . . . . . 107
5.3.3 Measurement of Buried Objects. . . . . . . . . . . . . . . . . . . 108
5.4 Tests of the Microwave SFCW Radar Sensor . . . . . . . . . . . . . . 110
5.4.1 Measurement of Pavement Sample. . . . . . . . . . . . . . . . . 111
5.4.2 Measurements of Actual Roads. . . . . . . . . . . . . . . . . . . 113
5.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
6 Summary and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Chapter 1
Introduction
Radar sensors, in general, are a very mature topic with many developments since
beforeWorldWarII.ThewordRADARstandsforRAdioDetectionAndRanging
and was first used by the United States Navy in 1940. The concept of radar,
however, could be considered as taking place around 1886 when Heinrich Hertz
demonstrated the transmission, reception, and reflection of electromagnetic waves.
Radar sensors have advanced significantly from their beginning as detection
devicesformilitaryapplicationsinWorldWarIIandhaveextendedtheirusagefor
manynon-militaryapplicationsacrossradio-frequency(RF)spectrumsfromlowto
microwave,millimeter-wave, andsubmillimeter-wavefrequencies,suchassensing
abnormal human body condition, diagnosing it and imaging the effect; early
detection of cancer; detection and inspection of buried underground objects; and
detection, tracking and monitoring of hidden activities, etc.
Some of the most significant usages of radar sensors for non-military applica-
tionsareforsurfaceandsubsurfacesensing.Intheseareasofsensing,radarsensors
have been used as a fast, reliable, accurate and cost-effective technique for non-
destructive,non-contactsensingofsurfacesandsubsurfacesinvariousapplications
such as detecting and locating buried objects, tunnels, archeological sites; mea-
suring distances, displacements, material’s thickness and moisture content; evalu-
ation of wood composites; detection and inspection of underground pipe
infrastructures;andinspectionofbridges,pavementsandothercivilinfrastructures,
e.g., [1–12]. The radar sensors for surface and subsurface sensing typically
implement impulse technique and continuous-wave (CW) methods with different
frequency modulations for transmitting signals like frequency-modulated continu-
ous wave (FMCW) or stepped-frequency continuous wave (SFCW).
The most distinguished difference between an impulse system and a FMCW or
SFCW system (and in general other non-impulse or CW based systems) is in the
transmittingwaveform.AnFMCWsystemtransmitsandreceivesCW(sinusoidal)
signals,onesignalateachfrequency,subsequentlyacrossabandwidth.AnFMCW
systemdoesnottransmitandreceivesignalsofdifferentfrequenciessimultaneously.
©TheAuthor(s)2016 1
C.NguyenandJ.Park,Stepped-FrequencyRadarSensors,
SpringerBriefsinElectricalandComputerEngineering,
DOI10.1007/978-3-319-12271-7_1