ELECTRONICS COMMUNICATION SYSTEM BY GEORGE soundofheaven.info HILL EDITION 37th reprint DZXACRAFRQLZZ For Sale in India Only - George, date Electronic Communication system/George Kennedy, Bernard Davis, provided, with a power output of the order of one-fifth of the main transmitter. Advanced Electronic Communications Systems Wayne Tomasi Sixth Edition Advanced Electronic Communication system/George Kennedy, Bernard Davis. Title: Kennedy's Electronic Communication Systems, 5th edition; Author: George Kennedy, Brendan Davis & SRM Prasanna; Format/binding: Softcover; Book.
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Electronic Communication Systems. Fifth Edition. George Kennedy. Supervising Engineer. Overseas Telecommun/catlons Commission. Austral/a. Bernard Davis. Kennedy. George, date. Electronic Communication system/George Kennedy, Bernard Davis,. 4th ed p. cm. Includes bibliographical references and index. ELECTRONIC COMMUNICATION SYSTEM BY GEORGE soundofheaven.info - Ebook Fifth Edition This edition can be exported from India only by the publisbers.
We're committed to developing high-quality content as well as digital course delivery solutions. What does the meter read now? Multiple-Choice Ques tions Review Problems Microwave Tubes And Circuits Even though. A periodic waveform has amplitude and repeats itself during a specific time period T. Further, a new chapter on fiber optic theory has been added.
This is a minor revised version of the earlier Chapter 8 of the fourth edition. Chapter to is on radiation and propagation of waves. There are several organizations possible for the material presented in the adapted edition.
Chapter 12 is on waveguides. Chapter 17 is on introduction to fiber optic technology and is a minor revised version of Chapter 18 of the fourth edition. Two new sections. Existing material on radio receivers has been thoroughly revised after removing the obsolete data. Even though most of the material in the chapter is on frequency modulation.
The pulse analog modulation part describes pulse amplitude. The main merit of this book is its lucid and simple way of explaining the basic principles ofoperation behind different communication systems. Chapter 4 is a thorough revision of Chapter S of the fourth edition.
I repeatedly came back to this book whenever I had to study communication systems and faced problems in getting a hold on some basic principles. Most of the material remains same as in the fourth edition. This chapter discusses all the different amplitude modulation techniques in practice and hence tbe name of the chapter.
I have attempted to explain the rationale behind the proposed adaptation. That is. This chapter discusses the theory behind analog and digital pulse modulation techniques. Chapter 3 is a new chapter in the adapted version. In view of this chapter. Preface to the Adapted Edition I was motivated to accept this work of adapting this hallmark book by Kennedy and Davis primarily due to the wonderful experience r had in reading from this book during my initial days of exposure to the area of elecrronic commw1ication.
The electromagnetic spectrum and terminologies in communication systems are the two new topics added to the chapter. As a part of this. T'h is chapter is a thorough revision of Chapter I of the fourth edition. Chapter To summarize. Chapter Sis a new chapter on pulse modulation techniques. The pulse digital modulation part explains pulse code. Among the numerous books on communication systems available in the market.
All during my student life and early career. I have tried to come up with a thorough revision of several chapters to eliminate obsolete material and add new ones.
Of course. The material for this chapter is drawn from Chapters 3 and 4 of the fourth edition. The revisions include adding additional material at appropriate places throughout the chapter for better understanding of the concepts.
Chapter 2 is on noise fundamentals. It wouldn't. Error Detection and Correction Time Multiple-Choice Ques tions Review Problems Ms Performance and Applications Con ten ts xiii I Atlienmis wilb Parabolic Reflectors Couplers Radiation Patterns. I Electrnagnetic Radhuion J Rectangular Waveguides Pcrfomrnncc and Applications 4I 3 Detectors and Detector Mounts I Methods of Exciting Waveguides Matching and Attenuation T hus.
The electrical means of communication started with wire telegraphy in the eighteen forties. Explain the term channel noise and its effects. All these different modes bundle. The infommtion transmission between humans si tting very close example. Objectives Upon conipleting the material in Chapter J. For long-distance communication.
Among these. The final section briefly discusses about basics or signal representation and analy: Some of these include Modulation mt: Understand the use of modulation. After enjoying these facilities in our daily routines. By observing all these developments. Due to miniaturization. For instance.
Any communication system will have five blocks. Ekctronic Conicatio11 S. Even though this change occurs. Several new modes of electrical communication emerge from time to time due to the continuous techno- logical progress.
Any logical order may be used. Once this is done. At the same time. This book aims at giving qualitative exposure to ctifferent concepts in the commu. This i: I shows the generic block diagram of a communication system.
The different steps involved in the transn-1ission of information may be outlined as follows: After this. The high-frequency signal is essential fQr carrying ot. This transmitter bl.
These acoustic pressure variations are converted into electrical fom1 using microphone as the transducer. This high-frequency signal is more commonly tenned carrier and i:. In the study of electrical communication systems. The carrier signal is characterized by Lhc three parameters amplitude. Trru1sducer is a device wh. The modulated signal from the modulator is transmitted or radiated into the atmosphere using an antenna as the transducer.
Chawl is a physical medium which connects the transmitter block with the receiver block.: Even though we use the words infonnation and message interchangeably. This physical manifestation of the infonnation is tenned as mes:. The infoTTTiation comes from the infom1ation source.
Introduction to Co11w11mic: The block diagram of typical radio transmitter is shown in Fig. The infomiation source converts this information into a physi- cal quantity. Even though. It is raining today at my place is the information and the speech corresponding to it is the message signal.
The modulation process involves varying one of these three parameters in accordance with the variation of the message signal. The speech signal is nothing but the acoustic pressure variations plotted as a function of time.
For electrical communication purpose.
This is because. Information is a very generic word signifying at the abstract level anything intended for communication.. Most of the receivers do conform broadly to the super heterodyne type.
Among the different processing steps employed. The physical medium includes copper wire. The objective of the canal is just to cany the water frorn one reservoir to the other and nothing more. The fo llowing illustration may help us understand the functionality of channel: Suppose we have two water reservoirs connected through a mechanism canal for transferring water from one to the other.
The message signal in the modified form travels through the channel to reach the entry point of the receiver. There are a great variety of receivers in communication systems.
The nature of modification of message signal in the transmitter block is based on the choice of the communication channel. The choice of a particuJar channel depends on the feasibility and also the purpose of communication system. Thus demodulation is essentially an inverse operation of modulation.. This is becau:. The super heterodyne receiver includes proctissing steps like reception.
For instance if the objective is to provide connectivity for speech commtmication among a group of people working in one physically localized place. On similar lines. Assume that there is a spe- cial and rare cultural event from a reputed artist organized at a far distant place destination city from your geographical locatiot1 source city.
The following example may help to better understand the need for modulation. Note that the transmitter and receiver must be in agreen1ent with modulation methods used. The signal which dictates regulation is termed as modulating signal.
The process of regulating is modulation. Even though there are several theories put forward about the comprehension of the information from the message signal. The first one is you because you are the message. Message acts as modulating signal. This may also be due the fact that human brain is the least understood part of human body in tenns of its functional ability.
Thus there arc two important aspects to be observed in this example. Then what will you do?
The obvious choice is you will take the help of transportation vehicle to carry you from the source city to the destination city. Hence before studying the modulation and its types. The output ofa receiver may be fed to a loud speaker. The incoming message signal via speech mode is processed by the speech perception system to comprehend the infonnation.
The modulation process is the most important operation in the modem communication systems. Accordingly the receiver can be a very simple crystal receiver. In electrical communication. The second one is the transpmtation vehicle which is the carrier. Once signals have been translated. This means that more number of message signals can be accommodated at higher frequencies. The ocsillations are sinusoidal in nature and measured as cycles per second or hertz Hz. Most of the message signals like speech and music are in the audio frquency range 20 H.
Once you reach the destination city. Each must be given its own carrier frequency location.
An unmodulated carrier has a constant amplitude. In order to separate Lhe various signals. Exactly similar situation is present in au electrical communication. This is the basic reason why we need to do modulation. Although this separation of signals has removed a number of the difficulties encountered in the absence of modulation. The oscillations can be as low as I Hz and can extend up to a very large value.
The distance that can be travelled by a signal in an open atmosphere is directly inversely proportional to its frequency wavelength. In any city. The entire range of frequencie!. The use of modulation process helps in shifting the given message signal frequencies to a very high frequency range where it can occupy only negligible percentage of the spectrum.
In a more fonnal way. A ve11ical antenna of this size is impracticable. In this fashion. There is an even more important argument against transmitting signal frequencies directly. Hence it should take the help of a carrier which has the capacity to take the message to the receiver.
This also overcome Since it is impossible to represent these two variables by a set of three constant pa- rameters. For a message at 1 MHz. The message signal which is to be transmitted to the receiver is like you and cannot travel for long distance by itself. The tuning of such a circuit is nonnally made variable and connected to the tuning control. But at I GHz. Table 1. Apart from this detailed classification. Cellular telephony 3. Even though these are not crisp boundaries.
Ln each range a typical application is only given as an example and is HOT exhaustive. Jntrod11 c: Frequency f Waveh! It is typically measured in seconds sec. Frequency is defined as the number of oscillations per second and is measured ill hertz Hz.
Ji llowing l'ulues: Each range is identified by end frequencies or wavelengths that differ by a factor of TV Remote For the classification purpose. JOO kli z EM waves travel at the speed of light in atmosphere or vacuum.
Modulation In terms of signal and channel bandwidths. This will be made clear in Chapters 3 and 4. Described mathematically in the time domain and in the frequency domain. A high-fidelity audio signal requires a range of 50 to Hz. Spectntnz The frequency domain representation of the given signal. When a carrier has been similarly modulated with each. Baseband Tra11smission Transmission of message signal in its original frequency range.
More specifically it is the range of frequencies over which the infonnation is present io the original signal and hence it may also be termed as signal bandwidth. Broadband Transmission Transmission ofm. Wavelength is defined as the distance travelled by an EM wave during the time of one cycle. If this consists of sinusoidal signals. Demodttlatiou On the similar lines. Bandwidth Bandwidth Bw is that portion of the EM spectrum occupied by a signal..
Since such nonsinusoidal waves occur very frequently as modulating signals in communications. Broadband Signal Message signal tn its modulated frequency range. Baseband Sig11a. Before trying to estimate the bandwidth of a modulated transmission. For wideband speech the frequency range is from O to Hz. At this point. The form for the Fourier series is 11s follows: A periodic waveform has amplitude and repeats itself during a specific time period T. Some examples of wav. I where v 1 "" voltage as a function of time E.
The symbolfin Equation 1. T represents time. This simpl. Each term is a simple mathematical symbol and shall be explained as follows: T27rl11 ] 1. Figure Next we will review the Fourier series. S Example 1. Example 1. The makeup ofa square or rectangular wave is the sum of harmonics the sine wave components at various amplitudes.
The Fourier coefficients for the rectangular waveform in Fig. Some non-sine wave recurring at a rate of times per second will consist of a Hz fundamental sine wave. F w nmx 8x! The bandwidth required will therefore be considerably greater than might have been expected if only the repetition rate of such a wave had been taken into account. It may be shown that any nonsinusoidal. There are an i11finire number ofsuch harmonics. For some wavefonns.
Graphical synthesis may be used. Fourier analysis c. The preceding statement may be verified in any one of three different ways. Indicate the false statement. In each case several of the hannonics will be reqai. St likely amplitude decreases with the harmonic number to affect the signal cl. As a general rule. Circle the letter preceding the ber of harmonics line that correctly completes each sentence.
In a communication system. Some fommlas for frequently encountered nonsinusoidal waves arc now given. Modulation is used to c. It may be proved mathemati- cally by Fourier analysis. Square wave: In this case adding the appropriate sine-wave components. An added advantage of this method. The acoustic channel is used for which of the d.
An antenna in the standard broadcast AM band I0. A message is composed ofunpredictable varia.
What does modulation actually do to a me. The carrier performs certain functions in radio communications. Which of the following steps is not included in d. All sound is concentrated from 20 Hz to frequency 20kHz b. The process of sending 4. Write the typical frequency ranges for the following classification of EM spectrum: Explain the need for modulation.
Define noise. The need for modula. UHF communications tion can best be exemplified by the following. From the transmitter and receiving started as early as the signal deterioration because of noise is usu.
Describe their functionality. Amplitude modulation is the process of is List the basic functions of a radio transmitter and the corresponding functions of the receiver.
What are they? Mention the elements of a communication system. Indicate the true statement. Where is it most likely to affect the signal? In radio receivers. It may sometimes even force a reduction in the bandwidth of a system.
It may be subdivided according to type. There are numerous ways of classifying noise. Measuring it is very contentious: Noise can limit the range of systems. After studying this chapter. Note how radiotelescopes are always located away from industry. In television receivers "snow" or "confetti" colored snow becomes superimposed on the picture.
It affects the sensitivity of receivers. Objectives Upon completing the material in Chapter 2. Internal noise is both more quantifiable and capable of being reduced by appropriate receiver design. The methods of calculating the noise produced by various:: It is ever present and limits the perfonnancc of most systems.
Calculate noise levels for a variety of conditions using the equations in the text. International satellite earth station Noise may be defined. It is most convenient here to divide noise into two broad groups: Many disturbances of an electrical nature produce noise in receivers. The very important noise quantities. External noise is difficult to treat quantitatively. Even though the additional noise produced comes from A limited portion of the sun's surface.
Static from distant sources will vary in intensity actord. Most of these sounds arc the result of spurious radio waves which induce voltages in the antertna.
For convenience. An astonishing variety of strange sounds will be heard. They represent atmospheric noise. It originates in the fonn of amplitude-modulated impulses.
The majority of these radfo waves come from natural sources of disturbance. Atmospheric noise consists of SpLtrious radio signals with components distributed over a wide range of freq uencies.
The usual increase in its level talccs place at night. Field strength is inversely proport ional to frequency. Such noJse consists of impulses. The static is likely to be n16re severe but less frequent if the storm is local.
Atmospheric noise becomes Jess severe at frequencies above about 30 MHz because of two separate factors. Static is caused by lightning discharges in thunderstonns and other natural electric d. Thus the "temperature" of a body is the statistical root mean square nns value of the veloc- ity of motion of the particles in the body.
It is due to the rapid and random motion of the molecules atoms and electrons inside the component itself. The noise received is called thennal or black-body noise and is distributed fairly uniformly over the entire sky. Fluorescent lights are another powerful source of such noise and therefore should not be used where sensitive receiver reception or testing is being conducted. The nature of industrial noise is so variable that it is difficult to analyze it on any basis other than the sta- tistical.
Under this heading. The noise is produced by the arc discharge present in all these operations. Summary Space noise is observable at frequencies in the range from about 8 MHz to somewhat above 1. In thenriodynamics. As the theory states. Noise 17 can become significant. We also receive noise from the center of our own galaxy the Milky Way. Random noise power is proportional to the bandwidth ove. Not very much of it below 20 MHz penetrates down through the ionosphere.
Such noise is generally random.. A random voltage across the resistor definitely exists and may be both measured and calculated. Using Equation 2. This noise voltage is caused by the random movement of electrons within the resistor.
Since it is random and therefore has a finite nns value but no de component. That is correct if the measuring instrument is a direct current de voltmeter. Assmne that RL is noiseless and is receiving the maximum noise power generated by R.
Then P. It is tnte that as many electrons arrive at one end of the resistor as at the other over any long period oftirne.
It must be realized that all fonn ulns referring to random noise arc applicable only to the m1s value of such noise. At any instant of time. The rate of arrival of electrons at either end of the resistor therefore varies randomly. The resistor is a noise generatur. The paths taken are random and therefore unequal. Noise 19 and V.
Note especially that the generated noise voltage is quite independent of the frequency at which it is measured. V Fig. Example 2. It is caused by rando. The most important of all the other sources is the shot effect. Hence the name shot noise. Although the average output current of a device is governed by tlle various bias voltages.
When amplified. A low voltage fed to this amplifier would be masked by the noise and lost. This stems from the fact that it is random and therefore evenly distributed over the frequency spectmm. In bipolar transistors. They all show that such noise is inversely proportional to transconductance and also directly proportional to output current. The minute currents induced in the input of the device by random fluctuations in the output current become of great importance at such frequencies and create random noise frequency distortion.
In addition. A noise figure see Sect-ion 2. Many variables are involved in the generation of this noise in the various amplifying devices. Shot noise behaves in a similar manner to thennal agitation noise. So far as the use of R is concerned. The most convenient method of dealing with shot noise is to find the value or fortnula for an equivalent input-noise resistor. This precedes the device. For noise only. Once this high-frequency noise makes its presence felt.
Tbc noise current has been replaced by a resistance so that it is now easier to add shot noise to thermal noi. RF transistors are remarkably low-noise.
The value of the equivalent shot-noise resistance R. The sum of two such nns voltages in series is given by the square root of the sum of their squares. Approximate formulas for equivalent shot. The result of all this is that it is preferable to measure noise at such high frequencies. This means that the total noise voltage is less than that due to any of the individual resistors.
Tt may appear logical to combine all the noise resistances at the input. The process might then be continued. The bandwidth of the amplifier is 6 MHz.. This is. Solution V. This greatly simplifies subsequent calculations. It is even better to go one step further and find an equivalent resistance for such an input voltage.
The result JJ useless because the argument assumed that it is important to find the total output noise voltage. Now the noise resistance actually present at the input of the second stage is R2. The same noise voltage would be present at the output if there were no R3 there.. Tnstead R. The-series resistance of the coil. As Example 2. I required to determine the noise voltage across the capacitor. For the second stage. Noise 23 ll. To either side ofresonance the presence of the tuned circuit affects noise in just the same way as any other voltage.
This will allow us Consider Fig.. In the preceding sections dealing with noise calculations. Calculate the equivalent input-noise 1'esistance of this two-stage amplifier.. The more interesting case is a tuned circuit which is not ideal. Thus i. Equation 2. The second 1s companson of n01se and signal at the same point to ensure that the n01se 1s..
The noise current in the circuit will be. It is fed from a source antenna of internal impedance R. For example. Instead of equivalent noise resistance.
Noise 25 not excessive. In the second instance. Therefore 2. In addi- tion. The noise figure of practical receivers can be kept to below a couple of decibels up to frequencies in the lower gigahertz range by a suitable choice of the first transistor. At frequencies higher than that. The noise figure Fis defined as the ratio of the signal-to-noise power supplied to the input tenninals of a receiver or amplifier to the signal-to-noise power supplied to the output or load resistor.
As a matter offact. Each is treated as a four-tenninal network having an input impedance R1. An effort is naturally made to keep the signal. It is defined as the ratio of signal power to noise power at the same point.
Calculate the generalized form of noise figure from steps 3 and 6 2. Calculate Pno from Rcq if possible 2. Each is now shown. The calculation procedure may be broken down into a number of general steps. Rt gain"' A Fig. It is seen from Fig. Write P for the noise output power to be determined later 2. Determine the signal output power P. An actual fonnula for F may now be obtained by substitution for the output noise power Putting it another way. All this applies here 1 with the minor exception that these noise resistances must now be added to the parallel combination of R0 and R.
Note that Equation 2. Noise 27 2. For the ti. It is convenient to define R: This may be seen from reexamining Equation 2. Not the least reason for its use is convenience. Note that this constitutes n lnrgc enough mismatch.
This is a situation exploited very often in prac6ce. Under matched conditions R. Controversy exists regarding which is the better all-around measurement. Jf all the noise of the receiver were generated by R0. Noise 29 P. T0F -. It is then possible to use Equation' If this is to lead to the conect value of noise output - power. It must be repeated that the equiva- lent noise temperature is just a convenient fiction. In defining the equivalent noise temperature of a receiver or amplifier.
Tcq' the equivalent noise temperature. Finally we have.. It will be recalled that the equivalent noise resistance introduced in Section 2. It is the d. When dealing with random noise calculations it comparing the noise performance of receivers: Circle the letter preceding the a. Thermal noise is independent of the frequency a.
Equivalent noise resistance vaJues. Industrial noise is usually o the impulse c. Galactic noise a. Cosmic noise L. Space noise generally covers a wide frequency doubled. The square of the b. One of the following types of noise becomes of c. One of the following is not a useful quantity for 9. Noise figure c. The value of a resistor creating thermal noise is 8.
Solar noise line that correctly completes each sentence. Atmospheric noise great importance at high frequencies. The noise power generated is therefore spectrum. Input noise voltage a. Indicate the noise whose source is in a category consists ofan incomplete statement followed by four different from that oftbe other three. Boltzmann's constant fiers. Which two broad classifications of noise are the width. HF mixers are generally noisier than HF ampli.
Noise temperature b. Random noise power is inversely proportional surement for comparing amplifier noise charac. A random voltage across a resistance cannot The noise output of a resistor is amplified by a noiseless amplifier having a gain of 60 and a bandwidth of20 kHz.
Noise 31 JO. When might the latter. Review Problems I. If this receiver is connected to an antenna with an impedance of 75 fl. How can some of them be avoided or minimized? What is the strongest source of extraterrestrial noise? The front end of a television receiver.
Define signal-to-noise ratio and noise figure ofa receiver. Noise in mixers is caused by inadequate image c. Which of lhe following statements is tme? What does the meter read now? Which of the following is the most reliable mea. The RF amplifier of a receiver has an input resistance of l n. Flicker is sometimes called demodulation a.
Discuss the types. The amplifier has a input resistor and a shot-noise equivalent resistance of fl. A meter connected to the output of the amplifier reads I mV rms.
Calculate the minimum signal voltage that the receiver of Problem 2. Review Questions I. Describe briefly the forms of noise to which a transistor is prone. Given that the bandwidth is 1. A parallel-tuned circuit.
An amplifier operating over the frequency range of to kHz bas a kfl input resistor. A receiver has an overall gain A. What is transit-time effect? How it is generated?
Describe briefly how this can be measured using the diode generator. Write the relation for maximum noise power output of a resistor. What is ideal and practical values of noise figure? Why they arc so explain. One of the terms of this formula will be the noise output power. What is noise temperature'? How is it related to noise figure? Write the expression for therms noise voltage.
Derive the relation between noise figure and temperature. The students will also be able to calculate the frequencies present. This clas- sification is mainly based on the nature of message or modulating signal. This is based on how many components of the basic amplitude modulated signal are chosen for transmission.
If the message to be transmitted is continuous or analog in nature. The amplitude of the carrier signal is varied in accordance with the message to obtain modulated signal in case of amplitude modulation. Upon studying this chapter. Based on this observation.
In analog communication. Understand the differences between AM and its variants. Tbis chapter deals with the amplitude modulation techniques employed in analog communication. After studying the theory of amplitude modulation techniques. This chapter deals with amplitude modulation techniques in detail. Objectives Upon completing the material in Chapter The modulation techniques in analog communicatiot1 can be classified into amplitude modulation AM and angle modulation techniques.
The angle modulation employs variation of angle of the carrier signal in proportion to the message. SSB and VSB signals Anulyze and detem1ine through computation the carrier power and sideband power in AM and its variants Solve problems involving frequency components.
This is followed by a description of different methods for the generation of AM. The next chapter deals with angle modu. Explain different approaches for the generation of AM. The communication process can be broadly divided into two types.
AM is defined as a system of modulation in which the amplitude of the carrier is made proportional to the instantaneous amplitude of the modulating voltage. In practice. Digital Modulation Techniques 7. Radio Transmitters And Receivers 8. Television Broadcasting 9. Transmission Lines Radiation And Propagation Of Waves Antennas Waveguides, Resonators And Components Microwave Tubes And Circuits Semiconductor Microwave Devices And Circuits Radar Systems Broadband Communication Systems Introduction To Fiber Optic Technology Seller Inventory International Edition.
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