Fundamental Principles of Radar

"""This book is intended to serve as a text for courses that provide a student’s first exposure to radar principles. It covers the broad concepts that underlie basic principles of operation for most existing radar systems and maintains a good level of mathematical rigor—suitable to convince readers without being so dense as to cause them to lose interest. The book provides an extensive exposition of techniques currently used for radar system design, analysis, and evaluation. To this end, it presents a comprehensive set of radar principles, including all features of modern radar applications with their underlying derivation, using the simplest mathematics possible."" - James Chu, IEEE Microwave Magazine, USA ""Habibur Rahman, the author of Fundamental Principles of Radar, is a professor of electrical and computer engineering at St. Louis University, Missouri, and has an extensive background in education. In addition, Prof. Rahman has been professionally active as a researcher in the general areas of electromagnetics, radar, satellite communications, and engineering education. This book is intended to serve as a text for courses that provide a student’s first exposure to radar principles. It covers the broad concepts that underlie basic principles of operation for most existing radar systems and maintains a good level of mathematical rigor—suitable to convince readers without being so dense as to cause them to lose interest. The book provides an extensive exposition of techniques currently used for radar system design, analysis, and evaluation. To this end, it presents a comprehensive set of radar principles, including all features of modern radar applications with their underlying derivation, using the simplest mathematics possible. Chapter 1 presents material covering historical background, elementary electromagnetics, and preliminary descriptions of different radar types, including basic radar block diagrams and operation; primary and secondary radars; monostatic, bistatic, and multiple input/multiple output radars; and more. Chapter 2 provides an overview of radar background information, such as range, range resolution, Doppler frequency, and extraction of target information. It demonstrates a few simple equations to calculate range ambiguity and resolution and explains the calculation of Doppler frequency with detailed examples. This chapter also provides the first set of homework problems for students. Chapter 3 introduces the concept of the radar equation; it first discusses the general form of the equation and then expands and generalizes it. The chapter concludes with a set of radar equations that apply to different radars, such as low pulse repetition frequency (PRF) and high PRF radars; radar beacons; bistatic, search, tracking, and pulse compression radar; and radar jamming Each subject in the chapter is followed by an example that further clarifies the equation and shows how to solve real-world problems. The RF Cafe Calculator Workbook, a free program published on the RF Cafe website (http://www.rfcafe.com/references/electrical.htm), complements this chapter with a program that calculates one- and two-way path loss, propagation time, radar blind speed, radar horizon, line of sight, and more. Chapter 4 explores target scattering, including various statistical models to describe radar cross-section (RCS) fluctuation, and looks at the RCS characteristics of some simple and complex shapes. Noise effects, noise figure, and noise temperature are also discussed. Radar clutter types, including surface, land, sea, and volume clutter (e.g., rain, dust, chaff, birds, and insects), are all discussed. The clutter statistical distributions Rayleigh, log-normal, K, and Weibull are briefly introduced, and equations for each distribution are listed, but no examples are given. Because students in their first radar class probably do not have strong statistics backgrounds in these types of distributions, examples for each distribution would have been very helpful. Chapter 5 explains atmospheric effects on the propagation of radar signals. It describes phenomena such as diffraction due to the Earth’s curvature, atmospheric refraction, multipath reflection, anomalous propagation, and ionospheric attenuation. Chapter 6 discusses the fundamentals of continuous-wave (CW) radar and reviews the basis for CW radar detection, especially the Doppler effect. The calculation of the Doppler shift from two aircraft approaching each other at a given angle is an excellent example provided in this chapter. A system diagram of CW radar shows how Doppler frequency is derived. Techniques for predicting CW radar range performance are included, as are several modulation techniques, such as linear, sinusoidal, frequency modulation, phase modulation, and multiple frequency. Chapter 7 covers moving target indication (MTI) and pulse Doppler radars. It reviews the limitations of radar in moving target detection and then presents an overview of various moving target indications and pulse Doppler radar techniques. This chapter also includes single and double delay-line cancelers, MTI recursive and nonrecursive filters, and staggered pulse repetition frequencies. Finally, the chapter introduces pulse Doppler radar as well as range and Doppler ambiguities. Many examples are included, one of the most helpful being the use of blind speed to determine maximum unambiguous range. Chapter 8 presents the general time–frequency ambiguity function, which provides a composite measure of both the resolution and ambiguity capability and imitations of given transmitter waveforms. It also describes the techniques of frequency-modulation pulse compression, frequency stepping, and phase modulation. A detailed discussion of Barker coding for pulse compression is presented, and an example of how to generate Frank coding for pulse compression is clearly explained. Chapter 9 describes the concepts behind synthetic aperture radar (SAR) that allow high-angular and cross-range resolution in long-range airborne search radar to be achieved. The basic mathematical relationships that support the design of SAR and the prediction of performance are developed. A good X-band SAR example that calculates the antenna length and far-field distance is included. Signal-to-noise ratio (SNR) applied to SAR is explained, and an SNR equation is derived. The chapter provides a helpful example of average power calculation with SNR. Chapter 10 presents range and range-tracking configuration, including sequential lobbing, conical scan, amplitude and phase-comparison monopulse radars, and track-while-scan. Several applications, advantages, and disadvantages of each technique are discussed. A few block diagrams show each type of radar system. The chapter also covers a-b and a-b-c trackers and how they relate to the Kalman filter and estimated values. Many examples of tracker/filter calculations and their estimation are given. Chapter 11, which covers aperture and array antennas, discusses in detail the important concepts underlying phase array antennas, including linear, planar, circular, and conformal arrays. Two tables list all equations to calculate null, main lobe maxima, half-power points, and minor lobe maxima for endfire and broadside array, and many good examples of design array antennas are provided. Chapter 12 presents various types of height-finding radars and 3D radar to measure elevation angle and azimuth angle. The discussion covers the effect of Earth geometrics and the radar horizon with and without refraction. The chapter also covers many types of radar altimeters, including beam limited, pulse limited, and SAR. Chapter 13 introduces the complete spectrum of electronic warfare (EW), including electronic countermeasures, electronic support measures, and electronic counter-countermeasures (ECCM). Only a generalized overview of EW is presented, with nomenclature, definitions, and semantics rather than specific technical descriptions. A good example of using X-band radar parameters to calculate the range of an interceptor within the radar’s illumination is provided. On the topic of ECCM, a detailed explanation of a sidelobe blanker and sidelobe canceler with a system block diagram of both systems is particularly informative. The chapter also considers the pros and cons of each type of ECCM receiver. Chapter 14 addresses the concept of over-the-horizon radar (OTHR) and describes sky- and surface-wave OTHR systems, with some discussion of ionospheric effects and ray path trajectories, including thin- and thick-layer models. It also includes calculation of the extended range of an OTHR radar. In the final pages of the chapter, the author gives a very interesting history of OTHR development in several countries, focusing especially on how unknown noise disrupted OTHR operation and forced the move to a quieter location. The use of OTHR for purposes such as ship tracking is also discussed. Chapter 15 presents the basic principle of secondary surveillance radar and its operation via interrogation and transponder reply and includes monopulse techniques and sidelobe suppression. It also shows the calculation of up- and downlink ranges. With the inclusion of six appendices covering basic applied mathematics and probability, this book covers all of the most important aspects of radar technologies. The first book on radar written for college students, it focuses on the fundamental principles in understandable language. In addition, the text provides great examples to clarify the associated equations and concepts, with all examples based on real radar parameters, giving students some experience of the real radar world. The book is accompanied by an instructor’s manual to save the instructor time and effort. This is the radar textbook all engineering programs should adopt for their radar classes. It is also an excellent reference for radar professionals in designing and analyzing radar performance."" - James Chu, IEEE Microwave Magazine, USA"