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Digital Basics for Cable TV Systems

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Digital Basics for Cable TV Systems


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  • Copyright 1999
  • Dimensions: 6-3/4" x 9-1/4"
  • Pages: 304
  • Edition: 1st
  • Book
  • ISBN-10: 0-13-743915-6
  • ISBN-13: 978-0-13-743915-7


Make the transition to digital CATV: the complete, easy-to-read guide!

Cable TV is rapidly moving from the familiar world of analog signals to a new digital world where yesterday's rules for optimizing performance no longer apply. If you install, upgrade, or maintain digital or mixed digital/analog systems, Digital Basics for Cable Television Systems is your complete guide to this new world. Friendly and authoritative, it's all you need to know to deliver digital services with maximum quality and reliability.

  • Simple fundamentals of digital signals and transport.
  • How digital signals differ from analog signals.
  • Complete coverage of digital testing and proof-of-performance.
  • Key digital measurement techniques, including the use of a spectrum analyzer.
  • Digital signal composition features, such as adaptive equalization, error correction, and compression.

With this book's simple illustrations, definitions and examples, you'll find it easy to master key digital CATV concepts such as layering, modulation and multiplexing. You'll learn how to measure digital signal power and burst power, and the impact of distortion, noise and interference on digital signals.

Digital Basics for Cable Television Systems is also a great reference, with a convenient glossary of digital terminology, a performance measurement map, a test equipment survey, exercises with answers, and much more. Whether you're a technician or an engineer, this book will help you maximize your digital system's performance - and your own.

Sample Content

Downloadable Sample Chapter

Click here for a sample chapter for this book: 0137439156.pdf

Table of Contents

(NOTE: Chapter begin with What You Will Learn and end with Summary, Questions for Review, and Selected Bibliography sections).

1. Digital Signal Measurement Guidelines.

Defining analog and digital for communications. Digital and analog, similarities and differences. Performance and measurements preview.

2. Modulation and Frequency Management.

Preparing information for distribution. The carrier concept. Modulation. Amplitude modulation. Frequency and phase modulation. Viewing the signal in the frequency domain. What is in a signal? AM, FM and PM in the frequency domain.

3. How an Analog Wave Becomes Digital Data.

Digital data. Sending digital data. Analog to digital signal processing. Signal sampling and quantizing. Transmission bandwidth. Bits to bandwidth. Bit rate. Restoring the analog signal from the digital signal.

4. Distributing, Layering, and Multiplexing.

Future distribution challenges. What is layering? Digital signal layering. The digital-analog allegory. Combining digital signals. Multiplexing in broadband cable and HFC systems.

5. Introduction to Digital Modulation Formats.

Modulation and multiplex formats. Digital modulation formats. QPSK and QAM. VSB and DVSB.

6. Viewing Digital Modulation.

Comparing analog and digital video signals. Viewing modulation with vector diagrams. I/Q modulation. Decision points. Jitter. Constellation and eye diagrams. Symbols, symbol rate, and bit rate. Filtering a digitally modulated signal.

7. Error Correction, Equalization, and Compression.

The keys to signal quality and efficiency. The causes of errors. Error correction. Bit, packet and frame error rates. Reed-Solomon error correction coding. What FEC statistics can tell. Adaptive equalization removes linear distortion. Limitations to adaptive equalization. How adaptive equalization works. View system response from the equalizer. Digital video depends on compression. Types of compression. Compression forms and formats. MPEG-2 compression uses. Trouble from compression. Compression measurements.

8. Digital Signal Quality.

Why measure signal quality? What degrades digital signal quality? Bit error rate. Measuring bit error rate. Viewing modulation with constellation and eye diagrams. Troubleshooting with constellation diagrams. Modulation quality measurements. Error vector magnitude. Measuring EVM. Modulation error ratio. MER diagnostics for troubleshooting and margin. Jitter is all in the timing. Instruments for signal quality measurements.

9. Average Power Measurements.

What is a power measurement? Power transfer. Digital signals are different. Types of power measurements. Average power. Power and bandwidth. Relative signal level measurements. Measuring digital signal average power. Total system power.

10. Peak, Peak-to-Average, and Burst Power Measurements.

The influence of peak and burst power on signal quality. The nature of non-continuous power. Peak power and peak-to-average power ratio. Measuring peak-to-average ratio. Measuring burst power. Peak and burst measurements.

11. Distortion, Noise, and Interference.

Effects on digital signals. Intermodulation distortion. Distortion levels. A new role for noise measurements. Troubleshooting and measuring noise performance. Interference. Test equipment for noise and distortion measurements.

Appendix A: Glossary.

Appendix B: Performance and Measurement Map.

Appendix C: Equipment for Testing Digital Signals in Cable TV Systems.

Appendix D: Answers to Chapter Questions.

Appendix E: Collected Bibliography.



Digital technology is coming to a cable system near you. How will this new technology affect your day-to-day job? Why is it that you feel a bit lost when you open a cable television or broadcast trade magazine and find unfamiliar concepts, words, phrases, and acronyms? I certainly did when I started research for this book. Fortunately, I just asked my partner in this project, Francis Edgington. He has helped many of you with your digital signal cable measurement questions. We have learned an important lesson.

A system that keeps high analog performance standards may not provide the same reliability for digital signals. Worse, your analog proof-of-performance measurements do not help you troubleshoot or fix a digital signal problem. Digital video signals, in and of themselves, do not show you their contents or their quality. They recover from stress automatically, to provide the best picture, sound, or data to your subscriber, but may be close to crashing without your knowing it.

Our first goal is to acquaint you with the fundamentals of digital technology, system integration, and quality parameters as they relate to the delivery of digital video over cable and optical fiber systems so you can study what you need, when you need it. Our second goal is to leverage your basic knowledge into making realistic measurements on digital signals in your cable system with the tools at hand. The third goal is to help you recognize the symptoms of trouble caused by digital signals in your analog environment so you can efficiently get it operating again.

This book is for cable, telephony, and radio frequency (RF) and optical fiber system technicians and engineers who install, upgrade, and maintain analog- and digital-signal systems. To get the most out of this book you should be experienced or at least familiar with the signal technologies and testing of NTSC or PAL cable television systems. This includes some fundamental test instrument knowledge, such as the way a television channel looks in the time and frequency domains, but not necessarily the modulation theory behind the video formats. You should also understand the fundamentals of distortion and carrier-to-noise ratio in systems with multiple channels. You can pick up most of this background from the book Cable Television Proof-of-Performance, listed in the bibliography of the first chapter.

The chapters have been kept small to allow reading in one or two brief sessions. The beginning of each chapter outlines what you will learn. As a review, each chapter includes a summary and questions for review. The answers to the review questions are in an appendix.

Here is the contents by chapter:

  • Chapter 1 introduces the differences and similarities between analog and digital signals.
  • Chapter 2 teaches you how information is sent on carriers using modulation.
  • Chapter 3 introduces the transformation of an analog signal into a digital bit stream.
  • Chapter 4 discusses the distribution of signals, and how digital signals are layered to protect themselves from transmission harm.
  • Chapter 5 shows how digital modulation is created and viewed.
  • Chapter 6 digs deeper into the methods used for making a digital signal compact, resistant to transportation problems, and self-correcting.
  • Chapter 7 summarizes the uses and attributes of several popular digital modulation formats and multiplexing schemes.
  • Chapter 8 describes the measurement of digital signal quality.
  • Chapter 9 helps you make digital signal power measurements.
  • Chapter 10 helps you make burst power measurements.
  • Chapter 11 shows how distortion, noise, and interference affect digital signals.
  • Appendices contain a glossary of terms and acronyms used in the book, a performance and measurement map, a test equipment survey, answers to the chapter questions.

Many people helped to inspire and watch over our creation of this book. First is Helen Chen of Hewlett-Packard, who, along with her design team, organized the cable television digital test scenario in articles first published in 1995. Her firsthand tutoring of the strengths and weaknesses of digital signals and their transport were fundamental to the creation of this book. Next we wish to acknowledge the people who put long hours in reading and critiquing the manuscript: Ian Johnston, Jack Moran, Bill Morgan, and Ian Wright. We would also like to thank Randy Goehler, Dan Kahn, Even Kristoffersen, and David Whitton for their notes, updates, and encouragement along the way.

We hope you enjoy the reading. We have tried to keep the tone light, and the explanations simple. Our goal is to give you enough background in digital technology to help you make fast and efficient measurements. Please do not hesitate to let us know if we have succeeded, or where we can improve the material. Here are our Internet addresses:

Jeffrey L. Thomas
Francis M. Edgington


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