Emeritus Professor of Electrical and Computer Engineering, Virginia Tech, Virginia, USA
Emeritus Professor of Electrical and Computer Engineering, George Mason University Virginia, USA
This edition first published 2020
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Library of Congress Cataloging-in-Publication Data:
Names: Pratt, Timothy, author. | Allnutt, J. (Jeremy), author.
Title: Satellite communications / Timothy Pratt, Jeremy Allnutt.
Description: 3rd edition. | Hoboken, NJ : Wiley, 2020. | Includes bibliographical references and index. |
Identifiers: LCCN 2019015618 (print) | LCCN 2019018672 (ebook) | ISBN 9781119482147 (Adobe PDF) | ISBN 9781119482055 (ePub) | ISBN 9781119482178 (hardback)
Subjects: LCSH: Artificial satellites in telecommunication. | Artificial satellites in telecommunication–Problems, exercises, etc. | Telecommunication–Problems, exercises, etc.
Classification: LCC TK5104 (ebook) | LCC TK5104 .P725 2020 (print) | DDC 621.382/5–dc23
LC record available at https://lccn.loc.gov/2019015618
Cover Design: Wiley
Cover Image: © 2018 Intelsat, S.A. and its affiliates. All rights reserved.
This book is dedicated to our wives,Maggie and Norma, in gratitude for their love and support for over 50 years.
The first edition of Satellite Communications was published in 1986, with the second edition following in 2003. There have been many changes in the 33 years since the first edition appeared, with a complete transition from analog to digital communication systems. The launch of satellites, once the province of government agencies, is now a thriving commercial business. By the time this third edition reaches the market, a number of private citizens will have entered the lower reaches of space as tourists. Analog transmission techniques have been replaced by digital modulation and digital signal processing. Spinner satellites have virtually disappeared, replaced by a much wider range of satellites from cubesats with mass less than 1 kg to large GEO satellites with mass exceeding 6000 kg. While distribution of television programming remains the largest sector of commercial satellite communications, earning approximately half of the worldwide revenue from satellite communication systems, low earth orbit constellations of satellites for internet access are set to challenge that dominance.
Satellite communication systems have made a very significant contribution to world economics and society. An international telephone call that cost US$1 per minute in 1960 could be dialed for less than US$0.02 per minute in 2000. Taking account of inflation, the cost of communications has been reduced by a factor of more than 1000, a claim that very few other services can make. Access to the internet will become available to 3 billion people in countries that lack a terrestrial communication system as new constellations of LEO satellites are launched. Global satellite navigation systems help motorists to find their way to their destination and make travel by ships and aircraft safer. Two way television links via satellite enable news from anywhere in the world to be available 24 hours a day. Fiber optic systems have contributed significantly to these achievements, but satellite systems provide service wherever there is a need to broadcast to many locations. These contributions to quality of life have been made possible by the efforts of thousands of telecommunications engineers who design, produce, and maintain the systems that allow us to communicate with almost anyone, anywhere. Rarely do these engineers receive credit from the general public for these achievements.
In writing the third edition of Satellite Communications we have followed the intent of the first two editions; to provide a text that can be used in undergraduate and beginning graduate courses to introduce students to the subject, and also by engineers in industry and government to gain a sound understanding of how a satellite communication system works. The subject of satellite communications is extensive and we make no claims to have provided comprehensive coverage of the subject. An internet search for satellite communications yielded more than 250 000 entries in 2018, and there are textbooks available that expand on the topics of each of our individual chapters. In the third edition, chapters 1–3 cover topics that are specific to satellites, including orbits, launchers, and spacecraft. Chapters 4–7 cover the principles of digital communication systems, radio frequency communications, digital modulation and multiple access techniques, and propagation in the earth's atmosphere, topics that are common to all radio communication systems. The chapter in the second edition on VSATs has been significantly expanded with the addition of low throughput satellite systems, otherwise known as SmallSats or cubeSats. These satellites range from experimental payloads assembled by undergraduate students to SmallSats that accompany advanced missions, such as the two that accompanied the Insight lander, which landed on Mars in late 2018. Also significantly expanded is the chapter dealing with rockets and launchers. Chapters 8–12 cover applications that include non-geostationary satellite systems, low throughput systems, direct broadcast satellite television, internet access by satellite, and global navigation satellite systems. The chapter on internet access by satellite is new to the third edition, and each of the chapters has been extensively revised to include the many changes in the field since 2003. Two new appendices have been added that cover digital transmission of analog signals, and antennas. These are topics that, in our experience, many students do not understand well yet are vital to most communication systems.
One of the most far reaching changes in communication systems technology has been the introduction of digital signal processing. High density integrated circuits are available that implement almost all of the functions required in transmitters and receivers in one or two devices. This is also true of spacecraft components such as three-axis control, which can now consist of a miniaturized digital controller rather than a group of two or three heavy momentum wheels. Liquid bi-propellant thrusters have been supplemented, and in some cases completely replaced by electric thrusters using xenon-ion propulsion systems.
Our text makes extensive use of block diagrams to explain how successive operations are performed on signals to obtain a specific result, for example, modulation of a digital signal onto an RF carrier or selection of a specific signal from a wide band multiplex of many signals. The blocks correspond to identifiable parts of a traditional analog system working in the frequency domain that could previously have been found in a transmitter or receiver, but are now part of a digital processor working in the time domain. Block diagrams are essential in understanding how communication systems are built up from successive operations on signals, but we recognize that in many cases the blocks are now implemented as digital operations.
The internet, and powerful search engines, have made it possible to find information about almost any subject in a few minutes. The reference section of the chapters of the third edition contain fewer references to papers and text books than previous editions and more references to internet sites. Although the specific sites may disappear with time, a search for the relevant topic will usually provide many alternative references. The internet has forced another change in the third edition. Our experience in teaching university courses has shown that the solutions to any problems issued to students for homework and exams appear very quickly at internet sites, and this is often the first place that students go to find answers, regardless of any rules that prohibit such action. As a result, we will not provide a solutions manual for the third edition. We have included exercises at the end of each chapter that instructors can use as the basis for homework problems, but our advice is to change the parameters of the questions each time one of the exercises is used. This forces students to work through the problem even if a similar internet solution is found, rather than just copying the solution. Changing the first sentence of the question also makes it harder for students to find an internet solution.
The authors would like to thank their colleagues and students who, over the years, have made many valuable suggestions to improve this text. Their advice has been heeded and the third edition is the better for it. In particular, we want to acknowledge the contributions of Dr. Charles Bostian, Alumni Distinguished Professor Emeritus of Electrical and Computer Engineering, co-author of the first and second editions, who first suggested that we should write a book on satellite communications. Dr. Bostian's writing can be found in parts of several chapters of the third edition that cover the basic theory of satellite communications. Dr. Bostian founded the Satellite Communications Group at Virginia Tech and led research that has contributed significantly to the success of many satellite communications systems.
Timothy Pratt is an Emeritus Professor of the Bradley Department of Electrical and Computer Engineering at Virginia Tech, having retired in 2013. He received his B.Sc. and Ph.D. degrees in electrical engineering from the University of Birmingham, UK, and taught courses on satellite communications in the UK and the United States for 40 years. Dr. Pratt is a lifetime senior member of the IEEE. He lives on a farm outside Blacksburg with his wife and several dogs and cats, and many white tail deer.
Jeremy Allnutt is an Emeritus Professor of the Electrical and Computer Engineering Department of George Mason University, having retired in 2014. His primary interest is radiowave propagation effects on satellite links, which he pursued at research establishments in England and Canada, before working at INTELSAT in the US from 1979 to 1994. Prior to joining George Mason University in 2000, he was a professor at the University of York, UK, and at Virginia Tech. Dr. Allnutt obtained his B.Sc. and Ph.D. in Electrical Engineering from Salford University, UK, and is a Fellow of IET and a Fellow of the IEEE. He lives in Blacksburg with his wife, two dogs, two cats, and several birds, rabbits, and deer that consider his backyard to be their home as well.