Practical Communication Theory (2nd Edition)
Practical Communication Theory, 2nd Edition enables the reader to quickly and easily generate the answers to realworld problems encountered in specifying, testing, and fielding any type of systems that involve radio propagation. It deals with free space radio propagation and propagation near the ground and over the ridge lines. As a bonus, this book also includes a special antenna and propagation slide rule, with unique scales, along with detailed explanations, and examples, of how to use it. Now in its second edition, Practical Communication has been updated to include new material on radio propagation near the earth in communication bands, which also explains how to use the slide rule scales for each of the appropriate propagation modes. The section on dynamic range has been expanded and there is additional material on knifeedge diffraction. The appendices have also been updated to include extra propagation formulae and graphs.
Inspec keywords: radiowave propagation; radio receivers; antennas; telecommunication links
Other keywords: link equation; radio propagation; antennas; receiver sensitivity; signaltonoise ratio; communication link
Subjects: Radio links and equipment; General electrical engineering topics; Radiowave propagation; Antennas
 Book DOI: 10.1049/SBEW516E
 Chapter DOI: 10.1049/SBEW516E
 ISBN: 9781613531860
 eISBN: 9781613531877
 Page count: 175
 Format: PDF

Front Matter
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1 Introduction
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Like most people, you probably don't care about the mechanics of radio propagation. What everyone cares about is the quality of received signals that we perceive as the fidelity of a voice signal, the clarity of a television image, the accuracy of a radar, or the dependability of a remote control command (among others). But adequate received signal quality is achieved only when all of the elements of the communication link are proper for range and interference environment in which they must operate. This book will allow you to select link components that will deliver the desired received signal quality, to determine the signal quality that will be achieved with a particular link or to determine the conditions (i.e., range and interference) for which a selected link will deliver adequate signal quality.

2 About dB
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In communication theory, we spend a lot of time manipulating widely varying signal strength values. We also deal with noninteger powers and roots of numbers. The use of decibel (dB) forms of numbers and equations greatly simplifies dealing with both of these considerations. Any number expressed in dB is logarithmic, which makes it convenient to compare values that may differ by many orders of magnitude. (Note that numbers in nondB form are called linear to differentiate them from the logarithmic dB numbers).

3 SignaltoNoise Ratio
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In considering communication link performance, signaltonoise ratio (SNR) is an extremely important concept. It is the common way to quantify the quality of the signal at any point in the communication process. Ultimately, it is the SNR that determines whether or not adequate communication takes place, but as will be seen in later chapters its requirement at each point in the link depends on many factors.

4 The Communication Link
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This chapter provides functional descriptions of communication link elements and also of the information signals that links are designed to carry. The communication link is everything required to get information signals from one point to another without wires. In its simplest form, the link includes a transmitter, a receiver, transmitting and receiving antennas, and everything that happens to the signals between the two.

5 The Link Equation
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The link equation described in this chapter calculates received signal power as a function of the various link parameters described in Chapter 4. It is also sometimes called the oneway link equation to distinguish it from radar equations that deal with roundtrip propagation.

6 Receiver Sensitivity and Dynamic Range
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Sensitivity and dynamic range have to do with the range of received signal strength that any kind of receiving system can accept. Sensitivity describes the weakest signals that can be received and processed, and dynamic range deals with the strongest signals that can be present. This chapter details how to calculate both values for analog and for digital receivers.

7 Challenging Conditions
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This chapter covers some of the challenging conditions like attenuation for transmission through rain or fog, nonline of sight transmission, the Doppler effect and antenna misalignment.

Appendix A: Derivation of Equations and Charts
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The derivations presented are included both to show the pedigree of some of the simplified equations in this book, and more importantly, to clearly identify the assumptions and rounding that have been applied.

Appendix B: Signal Strength in the Ether Waves
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It is common practice (including throughout this book) to state the signal strength of transmitted signals in dBm, even though this makes no physical sense. dBm is a unit of electrical power, a ratio of the signal power to one milliwatt. Power is defined only within a circuit. After transmission from an antenna, signals are rigorously defined only in terms of field strength. The correct units are volts per meter (or more often microvolts per meter). However, in many communication theory applications, it is extremely convenient to define a transmitted signal at some point in space in terms of dBm. That definition really assumes the situation shown in Figure B1, in which an ideal unity gain antenna is located at the point in space being considered. The signal power in dBm is then the output of that ideal antenna at that location.

Appendix C: Quick Formulas for Antennas
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This appendix is a collection of formulas and nomographs, which will allow to select the appropriate antenna for any type of communications application.

Appendix D: Quick Formulas for Receiver Sensitivity and Dynamic Range
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This appendix is a collection of formulas and charts, which will allow you to calculate the sensitivity and dynamic range for a wide range of types of receivers and receiving systems.

Appendix E: Quick Formulas for Propagation
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This chapter is a collection of formulas and nomographs, which will allow you to quickly calculate the signal strength at any point in a communication linkin terms of the common link parameters. For each formula or chart, you can select link distance in kilometers (km), statute miles (sm), or nautical miles (nm).

Appendix F: Quick Formulas For Doppler Shift
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A formula for Doppler shift is given together with a formula of the Doppler effect for arbitrary velocity vectors.

Appendix G: Antenna and Propagation Slide Rule
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The slide rule has scales for calculation of antenna parameters, free space propagation, 2ray propagation, the Fresnel zone distance and dB conversion. Figure G1 shows the location of each set of scales on the rule. The accuracy of calculations using this slide rule is approximately 0.2 dB.

Back Matter
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