Book contents
- Frontmatter
- Contents
- List of figures
- List of tables
- List of contributors
- Preface
- Acknowledgments
- 1 Fundamentals of digital television
- 2 Audio and video coding
- 3 Fundamentals and standards of video and audio compression
- 4 Channel coding for digital television
- 5 Digital and analog transmission systems
- 6 Advanced Television Systems Committee standard (ATSC)
- 7 Digital video broadcasting (DVB)
- 8 International Services Digital Broadcasting for Terrestrial Television Broadcasting (ISDB)
- 9 International System for Digital Television (ISDTV)
- 10 Digital terrestrial television multimedia broadcasting (DTMB)
- Appendix A Evolution of television standards
- Appendix B Signal analysis
- Appendix C Random signals and noise
- Glossary
- References
- Index
5 - Digital and analog transmission systems
Published online by Cambridge University Press: 28 January 2010
- Frontmatter
- Contents
- List of figures
- List of tables
- List of contributors
- Preface
- Acknowledgments
- 1 Fundamentals of digital television
- 2 Audio and video coding
- 3 Fundamentals and standards of video and audio compression
- 4 Channel coding for digital television
- 5 Digital and analog transmission systems
- 6 Advanced Television Systems Committee standard (ATSC)
- 7 Digital video broadcasting (DVB)
- 8 International Services Digital Broadcasting for Terrestrial Television Broadcasting (ISDB)
- 9 International System for Digital Television (ISDTV)
- 10 Digital terrestrial television multimedia broadcasting (DTMB)
- Appendix A Evolution of television standards
- Appendix B Signal analysis
- Appendix C Random signals and noise
- Glossary
- References
- Index
Summary
Introduction
Digital television signals are mainly transmitted over the air, which is also called terrestrial transmission, through cable systems, by geostationary satellites, using a microwave carrier, and over the Internet. For each transmission channel, a specific modulation scheme must be selected as the most appropriate, depending on the type of noise, power limitation, fading characteristics, transmission rate or cost.
Carrier waves are employed to allow efficient radiation of radio signals, because it is important to match the wavelength and the principal dimension of the transmitting and receiving antennas. The information is represented by an electrical signal, called a modulating signal, used to modify one or more parameters of the carrier. Appendix B presents a review of signal analysis and the use of the frequency spectrum by several services.
Modulation is the variation of one or more characteristics of the carrier waveform as a function of the modulating signal. The sinusoidal waveform is traditionally used as the carrier, and the modulation can be performed in three distinct ways:
Amplitude modulation (AM), if amplitude is the carrier parameter that is varied. This is the oldest modulation scheme; its fatherhood was disputed by Lee DeForest and Howard Armstrong.
Quadrature modulation (QUAM), if both the amplitude and the phase of the carrier are varied simultaneously. Single sideband (SSB) was the first QUAM scheme.
Angle modulation, if either the phase (PM) or the frequency (FM) is the carrier parameter that changes. The first FM modulator was designed by Howard Armstrong in 1933.
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- Information
- Digital Television Systems , pp. 94 - 117Publisher: Cambridge University PressPrint publication year: 2009