Overview

This text covers the basics of radar operations and theory, provides a background into the many radar-related areas and covers the electronic warfare issues from a radar perspective. Introduction of important radar principles is combined with an explanation of the major types of radar wherever possible so that the reader becomes familiar with the principles and radar types simultaneously. We do not attempt to study specific radar systems in any depth although some example systems are illustrated to reinforce theory and concepts. We also avoid some of the more complex radar topics. The text is designed for non-technical people who require an understanding of the most important radar principles, or people with a technical background looking for a broad introduction to radar systems. Accordingly, we avoid much of the mathematical complexity inherent in the subject. Some mathematics is unavoidable and is used to explain important principles. Those with a more technical bent can delve further into the subject by referring to the endnotes listed at the end of each chapter.

Specifically, this text has been developed to provide basic radar system knowledge to radar operators or those employed within radar environments. The text also supports other persons in radar-related endeavours such as the acquisition or maintenance of radar systems.

In Chapter 1, a basic radar block diagram is introduced to familiarise readers with the major components of a radar system. In Chapter 2, the reader is introduced to basic pulse radar as a means of explaining some fundamental radar concepts. The concepts behind radar antennas are then discussed in Chapter 3. Chapter 4 describes a subset of the many radar displays in existence with operation radar systems. The ubiquitous radar range equation is discussed in Chapter 5 as fundamental guide to radar performance and the many tradeoffs that exist in radar design. Chapter 6 describes the Doppler effect, which is a well-known acoustic effect widely used in continuous wave radar. Pulse Doppler radar and, in particular, moving target indication radar, is described in Chapter 7 as the final example of radars that make use of the Doppler effect. Chapter 8 investigates tracking and high-resolution radar. Chapter 9 investigates techniques that provide superior range and angular resolution. Chapter 10) covers secondary surveillance radar. The radar’s operating environment is described in the fourth part of the text in Chapter 11. Chapter 12 covers the electronic warfare aspects of radar operation and breaks electronic warfare into the traditional three components; electronic support, electronic attack and electronic protection.

At the end of each chapter is a list of reference material that explores each topic in more detail. A set of review questions is also provided at the end of each chapter with the answers to quantitative questions provided in brackets. Three appendices are provided to support the text. Appendix A lists and expands relevant acronyms. Appendix B provides a list of common prefixes and the Greek alphabet and Appendix C explains the decibel.

This Radar Fundamentals book is used as a text for a number of professional education and university courses. In particular, it is complimentary to attendees on the edVirtus Radar Fundamentals training course delivered by the author Dr Ian Faulconbridge, as well as a number of in-house courses.

Preface

Radar is a critical element of many surveillance systems that exist in modern military and civilian environments. The roles of radar include target detection and identification, navigation and mapping, target tracking and weapons guidance. Modern radar is capable of extracting surprisingly accurate parametric information about targets including range, bearing, relative velocity, configuration and even identity. Although radar is an applied electrical engineering discipline involving complex mathematical concepts and theories, it is also a physical technology bounded by well-established laws of physics and nature. Consequently, a majority of radar concepts can be explained without great complexity. That is the primary aim of this text. Specifically, it text has been developed to provide basic radar system knowledge to radar operators or those employed within radar environments. The text also supports other persons in radar-related endeavours such as the acquisition or maintenance of radar systems.

This text covers the basics of radar operations and theory, provides a background into the many radar-related areas and covers the electronic warfare issues from a radar perspective. Introduction of important radar principles is combined with an explanation of the major types of radar wherever possible so that the reader becomes familiar with the principles and radar types simultaneously. We do not attempt to study specific radar systems in any depth although some example systems are illustrated and discussed to reinforce theory and concepts. We also avoid some of the more complex radar topics such as detailed antenna design, transmission systems and receiver and transmitter electronics. The text is designed for non-technical people who require an understanding of the most important radar principles, or people with a technical background looking for a broad introduction to radar systems. Accordingly, we avoid much of the mathematical complexity inherent in the subject. Some mathematics is unavoidable, however, and is used to explain important principles. Those with a more technical bent can delve further into the subject by referring to the resources listed at the end of each chapter.

The text is divided broadly into five parts: radar basics, Doppler radars, tracking and high-resolution radars, the radar operating environment, and radar electronic warfare.

The first part commences with an introduction to the principles behind radar operation and explains the main types of radar systems. In Chapter 1, a basic radar block diagram is introduced to familiarise readers with the major components of a radar system. The important relationship between frequency and wavelength is also reinforced prior to any detailed coverage.

In Chapter 2, the reader is introduced to basic pulse radar as a means of explaining some fundamental radar concepts. The first concept is the ability of a radar system to determine the distance to a target. This leads to the concepts of pulse repetition interval, pulse repetition frequency, and pulse width, and the associated problems of range ambiguity, range resolution and blind range. The difference between power and energy is also explained.

The concepts behind radar antennas are then discussed in Chapter 3. The coverage concentrates on basic parabolic reflectors and an introduction to electronically-steered phased array antennas. The antenna concepts of beamwidth, gain, polarisation and sidelobes are explained.

Chapter 4 describes a subset of the many radar displays in existence with operation radar systems. The chapter also describes radar’s role in the broader context as a sensor within a larger system. The interfaces between radar systems and operational environments including aircraft, ships and air traffic control environments are described.

The ubiquitous radar range equation is discussed in Chapter 5 as fundamental guide to radar performance and the many tradeoffs that exist in radar design. The equation is derived from first principles and shown in some of its many different forms. The concepts of transmitted power, minimum detectable signal strength, and radar cross section are introduced and related to radar range performance in the chapter. Pulse integration is also explained as a means of improving radar performance, and power versus energy is re-introduced.

The second part of the text deals with radars that make use of the Doppler effect. Chapter 6 describes the Doppler effect, which is used in continuous wave radar. A variant of continuous wave radar called frequency-modulated continuous wave radar is also introduced. Pulse Doppler radar and, in particular, moving target indication radar, is described in Chapter 7 as the final example of radars that make use of the Doppler effect. The techniques of pulse Doppler and moving target indication combine the power of pulse radar and continuous wave radar to enhance the performance of a radar system. The concept known as Doppler blind speed is explained and calculated.

Part three of the text investigates tracking and high-resolution radar and starts with an investigation of tracking radar in Chapter 8. Lobing and scanning are explained as are the concepts of monopulse tracking, and range and velocity tracking. Chapter 9 investigates techniques that provide superior range and angular resolution. Pulse compression techniques are becoming widely used in modern radar systems due to the recent explosion in available signal processing power. Synthetic aperture radar makes use of signal processing to synthesise extremely large antenna apertures and produces extremely high angular resolutions. A closely related topic called inverse synthetic aperture radar is also discussed.

A short chapter (Chapter 10) covers secondary surveillance radar which is more of a communications system than it is a radar and investigates how secondary surveillance radar provide detailed information to civilian and military operators about a cooperating target’s identity and location.

The radar’s operating environment is described in the fourth part of the text in Chapter 11. The chapter begins with a broad coverage of the many electromagnetic propagation issues relating to radar systems. Issues such as scattering, refraction, attenuation and external noise are covered, concentrating on how these issues may constrain the selection of a suitable operating frequency. Radar clutter is described as a major issue affecting the operation of radar in a real environment. The concept of radar cross section density is introduced as a way of calculating the signal-to-clutter ratio for a given radar and determining its likely performance impacts. Sea clutter and land clutter are discussed, as are techniques for detecting targets in a cluttered environment. Some of the most common radar receiver design concepts employed to counter the operating environment are described. The principles of fast time constant, sensitivity time control and instantaneous automatic gain control are included.

Chapter 12 covers the electronic warfare aspects of radar operation and breaks electronic warfare into the traditional three components; electronic support, electronic attack and electronic protection. Electronic support and the techniques used to intercept and analyse radar energy are described. The electronic support section covers the aims of electronic support and then discusses electronic support systems in terms of antennas, receivers and displays. The concept of probability of intercepting radar energy is discussed to illustrate the challenges associated with successful electronic support. Electronic attack techniques aim to deny enemy use of the radar spectrum. The major electronic attack tools and techniques are described, and include chaff, active and passive decoys, jamming, radar cross-section reduction, and anti-radiation missiles. Jammer-to-signal strength is discussed and the concept of “burnthrough” is explained. Electronic protection involves using radar systems successfully in the presence of enemy electronic attack and is detailed in the final section of Chapter 12. The concept of “burnthrough” is revisited to illustrate radar design that can be used as an effective electronic protection. Electronic protection is then covered in terms of antenna, transmitter, and receiver design.

At the end of each chapter is a list of reference material that readers may use to explore each topic in more detail. A set of review questions is also provided at the end of each chapter with the answers to quantitative questions provided in brackets.

Three appendices are provided to support the text. Appendix A lists and expands the acronyms that are used throughout the text and dominate the radar discipline. Appendix B provides a list of common prefixes and the Greek alphabet and Appendix C explains the decibel as applied to radar systems.

Table of contents

1	INTRODUCTION	1
1.1	Examples of Radar Applications	1
1.2	Basic Radar Operation	3
1.3	Basic Radar Types	4
1.3	Electromagnetic Propagation Fundamentals	7
1.4	Radar Band Designation	9
1.5	Electronic Warfare Taxonomy	9
2	PULSE RADAR CONCEPTS	11
2.1	Pulse Radar Block Diagram	11
2.2	Range-Related Calculations	16
2.3	Normal Pulse Radar Operation	17
2.4	Pulse Width and PRF Considerations	19
2.5	Summary	32
3	BASIC RADAR ANTENNAS	35
3.1	Major Antenna Types	35
3.2	Antenna Characteristics	38
3.3	Electronically-Steered Planar Arrays	52
3.4	Summary	69
4	RADAR DISPLAYS AND INTERFACES	73
4.1	Radar Displays	73
4.2	Radar Interfaces	76
4.3	Summary	82
5	RADAR RANGE EQUATION	85
5.1	Derivation of the RRE	85
5.2	Minimum Detectable Signal Strength	87
5.3	Pulse Integration	89
5.4	System Losses	93
5.5	Radar Cross-Section	94
5.6	Cosec2 Revisited	100
5.7	Examples and Calculations	102
5.8	One-Way Radar Range Equation	105
5.9	Power, Energy, Time and the RRE	105
5.1	Summary	107
6	CONTINUOUS WAVE RADAR	109
6.1	Doppler Effect	109
6.2	CW Radar Block Diagram	110
6.3	CW Radar Characteristics	113
6.4	Frequency Modulated CW Radar	116
6.5	FM CW Characteristics	120
6.6	Summary	125
7	PULSE DOPPLER RADAR	127
7.1	Pulse Doppler Radar Concepts	127
7.2	Moving Target indication	129
7.3	Doppler Measurement and Ambiguity	135
7.4	Summary	139
8	TRACKING RADAR TECHNIQUES	141
8.1	Target Acquisition	141
8.2	Tracking Radar	141
8.3	Other Tracking Radar Concepts	151
8.4	Summary	153
9	HIGH-RESOLUTION RADAR TECHNIQUES	155
9.1	Introduction	155
9.2	Pulse Compression and Range Resolution	156
9.3	Revised Radar Range Equation	161
9.4	Range Resolution	162
9.5	Minimum Range	162
9.6	Design Considerations	162
9.7	Worked Example	165
9.8	Synthetic Aperture Radar and Angular Resolution	166
9.9	Unfocussed SAR	168
9.1	Focussed SAR	172
9.11	Design Issues	175
9.12	Inverse SAR	177
9.13	Summary	180
10	SECONDARY SURVEILLANCE RADAR	183
10.1	Civilian Air Traffic Control Applications	183
10.2	Military Applications	185
10.3	SSR Equipment	186
11	THE NATURAL ENVIRONMENT	189
11.1	Reflection from the Earth’s Surface	189
11.2	Refraction	192
11.3	Attenuation	195
11.4	External Noise	197
11.5	Clutter	198
11.6	Summary	212
12	ELECTRONIC WARFARE	215
12.1	Introduction	215
12.2	Electronic Support	215
12.3	Electronic Attack	231
12.4	Electronic Protection	245
12.5	Summary	261
APPENDICES
A	GLOSSARY	265
B	COMMON PREFIXES AND THE GREEK ALPHABET	269
C	DECIBELS	271
	INDEX	273

Sample Chapter

Download a sample chapter of Radar Fundamentals (PDF)