Digital Communication Techniques

Christian Gontrand

• Publisher: Wiley-ISTE
• Year: 2020
• Print ISBN: 9781786305404
• eBook ISBN: 9781119705246
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

There have been considerable developments in information and communication technology. This has led to an increase in the number of applications available, as well as an increase in their variability. As such, it has become important to understand and master problems related to establishing radio links, the layout and flow of source data, the power available from antennas, the selectivity and sensitivity of receivers, etc.

This book discusses digital modulations, their extensions and environment, as well as a few basic mathematical tools.

An understanding of degree level mathematics or its equivalent is a prerequisite to reading this book. Digital Communication Techniques is aimed at licensed professionals, engineers, Masters students and researchers whose field is in related areas such as hardware, phase-locked loops, voltage-controlled oscillators or phase noise.

1
Modulation

1.1. Modulation?

1.1.1. Main reasons for modulation

• – In the modulation process, one characteristic of a high-frequency (passband) carrier signal is modified according to the instantaneous amplitude of the signal to be processed (in its baseband).
• – Why does modulation make sense for signal transmission (distance, etc.)?
• – Several signals are transmitted on the same channel.
• – Capacitative or inductive devices need high frequency (carrier) to operate (to ensure Stability and a good Noise Rejection).

1.1.2. Main modulation schemas

• – Examples of application: transmitting audio and video signals.
• – Mobile radio communications, such as cell phones.
  Basic modulation types are as follows:
• – amplitude modulation (AM): modifies the amplitude;
• – frequency modulation (FM): changes the frequency;
• – phase modulation (PM): changes the phase.

1.1.3. Criteria for modulation via electronics

Requirements for signal processing are as follows:

• – speed;
• – reliability and precision;
• – low energy consumption.

Electronics serve to transport information at least energy cost, as quick as possible, in the greatest quantity possible, with the highest quality possible and with maximum reliability.

NOTE.– In electrical engineering, the electrical signal serves to transport the energy and not the information.

1.1.4. Digital modulation: why do it?

Digital modulation provides more information capacity, compatibility with digital data services, better security levels, better communication quality and wider availability than analog, for example.

1.2. Main technical constraints

• – available passband;
• – usable power;
• – level of system background noise.

The radiofrequency (RF) spectrum is aimed at many users and communication services are only growing. Digital modulation has greater capacity to propagate large quantities of information than analog.

If all the frequencies that form the signal to be transmitted are found in the passband supporting the transmission, this signal can be applied to the line directly.

Figure 1.1. Transmission of a signal in baseband. For a color version of this figure, see www.iste.co.uk/gontrand/digital.zip

If all or some of the frequencies forming the signal to be transmitted are found outside the bandwidth of the transmission medium, a modulation will make it possible to shift all the frequencies, in blocks, to higher frequencies (see the so-called heterodyne process) (Figure 1.2).

Figure 1.2. Transmission of a signal via modulation. For a color version of this figure, see www.iste.co.uk/gontrand/digital.zip

Each frequency f of the signal “becomes” f + ∆f.

If ∆f suffices, all frequencies of the sign...

Table of contents

• Cover
• Table of Contents
• Preface
• Introduction
• History Pages
• List of Acronyms
• 1 Modulation
• 2 Some Developments in Modulation Techniques
• 3 Signal Processing: Sampling
• 4 A Little on Associated Hardware
• Conclusion
• APPENDICES
• References
• Index
• End User License Agreement