Electronic communication systems by wayne tomasi solution manual pdf

Download now. For Later. Related titles. Carousel Previous Carousel Next. Modern Electronic Communication System 9th edition by beasly and miller. Book Communication Electronics 3rd Ed- Frenzel Communication Electronics, 2nd ed. Chapter 1 Introduction to Electronic Communication Jump to Page. Search inside document. The original souree information can be in analog form, such as the hu- man voice or music, or in digital form, such as binary-coded numbers or alphanumeric codes.

An analog signal contains an infinite number of values. Dig- ital signals are voltages or currents that change in discrete steps or levels. Long-distance communications probably began with smoke signals or tom-tom drums, and that using electricity began in when Samuel Finley Breese Morse invented the first workable telegraph, Morse applied for a patent in and was finally granted it in He used electromagnetic induction to transfer information in the form of dots, dashes, and spaces between a simple transmitter and receiver using a transmission line consisting of a length of metallic wire.

In , Alexander Graham Bell and Thomas A, Watson were the first to successfully transfer human conversation over a crude metallie-wire communica- tions system using a device they called the telephone. Zero dB-SPL is the threshold of hearing. The threshold of pain is approximately dB-SPL.

Tn the electronics communications field, the decibel originally defined only power ra- tios; however, as a matter of common usage, voltage or current ratios can also be expressed in decibels. The practical value of the decibel arises from its logarithmic nature, which per- mits an enormous range of power ratios to be expressed in terms of decibels without using excessively large or extremely small numbers. In essence, the 4B is a transmission-measuring unit used to express relative gains and losses of elec tronic devices and circuits and for describing relationships between signals and noise.

Deci- bels compare one signal level to another. The dB has become the basic yardstick for caleu- lating power reiationships and performing power measurements in electronic communications systems. Mahlon Loomis became the first person to communicate wireless through Earth's almosphere, : First tansatiantic telegraph cable installed.

Watson Invent the telephone, Thomas Aiva Edison invents the phonograph, Heinrich Hertz discovers electromagnetic waves. Fessenden transmits first human speech through radio waves, Reginald A. Fessenden transmits the world's fst radio broadeast using continuous waves.

However, Equation d can be used to represent the dB voltage gain of a device regardless of whether the input and output resistances are equal. With dBm, the reference level is mW i. One milliwatt was chosen for the reference because it equals the average power produced by a telephone transmitter. It was later adapted to electrical units and defined as mW of electrical power measured across a ohm load and was intended to be used on telephone circuits for voice-frequency measurements.

Pi any power in watts, Tables and list power levels in both watts and dBm for power levels above and be- low I mW, respectively. Negative dBm values indicate power lev- cls less than 1 mW, and positive dBm values indicate power levels above 1 mW. For ex- ample, a power level of 10 dBm indicates that the power is 10 dB above 1 mW, or 10 times 1 mW, which equates to 10 mW. A power level of 0. Example Be aia. It ized that the Bel provided too much compression.

For example, the Bel unit compressed absolute ratios ranging from 0. This made it difficult to relate Bel units to true magnitudes of large ratios and impossible to express small differences with any accuracy. For these rea- sons, the Bel was simply multiplied by 10, thus creating the decibel. Determine a the input power in dBm, b output power Pay in watts and dBm, the dB gain of each of the three stages, and 4 the overall gain in dB, Solution a.

When powers are given in dBm, however, they cannot be combined through simple addition. For example, if a signal with a power level of 0 dBm 1 mW is combined with another signal with a power level of 0 dBm 1 mW , the total combined power is obviously 2mW 3 dBm. The com- Dining term is added to the higher of the two power levels to determine the total combined power level. As shown in the table, the closer the two power levels are to each other, the higher the combining term.

Example Determine the total power when a signal with a power level of 20 dBm is combined with a second signal with a power level of 21 dBm. Solution The dB difference in the two power levels is 1 dB. Therefore, from Table , the com- bining term is 2. A receiver is a collection of electronic devices and circuits that accepts the transmitted signals from the transmission medium and then converts those signals back to their original form.

In essence, the cartier signal carries the information through the system, The information signal modulates the carrier by changing either its amplitude, frequency, or phase. Modulation is simply the process of changing one or more properties of the analog carrier in proportion with the information signal. An analog communications system is a system in which energy is transmitted and received in analog form a continuously varying signal such as a sine wave.

The term digital communications, however, covers a broad range of communica- tions techniques, including digital transmission and digital radio. If its in analog form, it must be converted to digital pulses prior to trans- mission and converted back to analog form at the receive end.

With digital radio, the modulating signal and the demodulated signal are digital pulses. The digital pulses could originate from a digital transmission system, from a digital source such as a computer, or be a binary-encoded ana log signal.

In digital radio systems, digital pulses modulate an analog carrier. Therefore, the transmission medium may be a physical facility or free space. Ifthe information signal is analog and the amplitude V of the carrier is varied proportional to the information signal, amplitude modulation AM is produced. Ifthe frequency f is varied proportional to the information signal, frequency modulation FM is produced, and, ifthe phase 6 is varied proportional to the informa- tion signal, phase modulation PM is produced.

If the information signal is digital and the amplitude V of the carrier is varied pro- portional to the information signal, a digitally modulated signal known as amplitude shift keying ASK is produced.

Ifthe frequency f is varied proportional to the information sig- nal, frequency shift keying FSK is produced, and, if the phase 8 is varied proportional to the information signal, phase shift keying PSK is produced.

If both the amplitude and the phase are varied proportional to the information signal, quadrature amplitude modulation QAM results. A carrier that has been acted on by an information signal is called a modulated wave or modulated sig- nal.

Demodulation is the reverse process of modulation and conyerts the modulated carrier back to the original information i. Demodu- lation is performed in a receiver by a circuit called a demodulator. For example, all commercial FM stations broadcast voice and music signals that occupy the audio-frequeney band from approx- imately Hz to 15 KHz.

To avoid interfering with each other, each station converts its information to a different frequency band of channel. The term channel is often used to refer to a specific band of frequencies allocated a particular service. Figure is the simplified block diagram for an analog electronic communica- tions system showing the relationship among the modulating signal, the high-frequency carrier, and the modulated wave.

The information can be in analog or digital form, and the modulator can perform either analog or digital modulation. Frequency translation is an intricate part of electronic commu- nications because information signals may be up- and down-converted many times as they are transported through the system called a channel.

In the receiver, the modulated signal is amplified, down-converted in frequency, and then demodulated to reproduce the original source information. This is accomplished by convert- ing the original information into electromagnetic energy and then transmitting it to one or more receive stations where it is converted back to its original form, Electromagnetic en- ergy can propagate as a voltage or current along a metallic wire, as emitted radio waves through free space, or as light waves down an optical fiber.

Electromagnetic energy is dis- tributed throughout an almost infinite range of frequencies. Frequency is simply the number of times a periodic motion, such as a sine wave of voltage or current, occurs in a given period of time. Each complete alternation of the wave- form is called a cycle. The basic unit of frequency is hertz Hz , and one hertz. In electronics it is common to use metric prefixes to rep- resent higher frequencies. The useful electromagnetic frequency spectrum ex- tends from approximately 10 kHz to several billions of hertz.

The lowest frequencies are used only for special applications, such as communicating in water. The International Telecommmunications Union TU is an international agency in control of allocating frequencies and services within the overall frequency spectrum. Extremely low frequencies ELFs are signals in the Hz to Hz range and include ac power distribution signals 60 Hz and loy- frequency telemetry signals. Voice frequencies. Voice frequencies VFs are signals in the Hz.

Standard telephone channels have a Hz to Hz bandwidth and are often called voice- «frequency or voice-band channels. Very low frequencies, Very low frequencies VLFs are signals in the 3-kHz to kHz range, which include the upper end of the human hearing range.

Low frequencies LES are signals in the kHz to kHz range and are used primarily for marine and aeronautical navigation. High frequencies. Ultrahigh frequencies. Ultrahigh frequencies HFS are signals in the MHz to 3-GHzrange and are used by commercial television broadcasting of channels 14 to 83, land mobile communications services, cellular telephones, certain radar and naviga- tion systems, and microwave and satellite radio systems.

Generally, frequencies above 1 GHz are considered microwave frequencies, which includes the upper end of the UHF range. Superhigh frequencies. Superhigh frequencies SHFs are signals in the 3-GHz to GHz range and include the majority of the frequencies used for microwave and satellite radio communications systems.

Extremely high frequencies. Extremely high frequencies EHFs are signals in the GHz to GHz range and are seldom used for radio communications except in very sophisticated, expensive, and specialized applications. Infrared frequencies are signals in the 0.

Infrared signals are used in heat-seeking guidance systems, electronic photography, and astronomy. Visible light. Visible light includes electromagnetic frequencies that fall within the visible range of humans 0.

Wavelength is the length that one cycle of an electromagnetic wave occu- pies in space ie, the distance between similar points in a repetitive wave. The emission classifications are identified by a three-symbol code containing a combination of letters and numbers as 10 10 10 10" 10? The second symbol is a number that identifies the type of emission, and the third symbol is another letter that describes the type of information being transmitted.

For exam- pile, the designation A3E describes a double-sideband, full-carrer, amplitude-modulated sig- nal carrying voice or music telephony information. Noise is discussed later in this chapter.

In other words, the bandwidth of the commu- nications channel must be equal to or greater than the bandwidth of the information. For ex- ample, voice frequencies contain signals between Hz. As a general rule, a communications channel cannot propagate 4 signal that contains a frequency that is changing at a rate greater than the bandwidth of the channel. Information theory can be used to determine the information capacity of a data communications system. Information capacity is a measure of how much information can be propagated through a communica- tions system and is a function of bandwidth and transmission time.

Information capacity represents the number of independent symbols that can be car- ried through a system in a given unit of time, The most basic digital symbol used to repre- sent information is the binary digit or bit.

Therefore, it is often convenient to express the information capacity of a system as a bit rare. Bitrate is simply the number of bits trans- mitted during one second and is expressed in bits per second bps. In , R. Hartley of Bell Telephone Laboratories developed a useful relationship among bandwidth, transmission time, and information capacity. The higher the signal- to-noise ratio, the better the performance and the higher the information capacity.

Solution a. The sum and dif- ference frequencies are called cross products. Cross products are produced when harmonics as well as fundamental frequencies mix in a nonlinear device. The harmonics have been eliminated from the dia- gram for simplicity.

Example For nonlinear amplifier with two input frequencies, 3 kHz and 8 kHz, determine First thre harmonics pretent in the output foreach input frequency. Cross-product frequencies produced for values of mand n of and 2. The first three harmonics include the two original frequencies, 3 kHz and 8 kHz; two times each ofthe original frequencies, 6 KH and 16 kHe; and thee times each of the orginal fre- quencies, 9 KH and 24 kHz Bb.

As the name implies, impulse noise consists of sudden bursts of irregu- larly shaped pulses that generally last between a few microseconds and several mil- liseconds, depending on their amplitude and origin. The significance of impulse noise hits on voice communications is often more annoying than inhibitive, as impulse hits produce a sharp popping or crackling sound. First, the ov noise figure of 3. From Equation , itcan be seen thatthe first stage in a series of amplifiers, as found in audio amplifiers and radio receivers, contributes the most to the overall ns figure.

This is true as long as the gain of the first stage is sufficient to reduce the effect the succeeding stages. For example, if A, and Ay in Example were only 3 dB, overall noise figure would be 4. Figure shows how signal-to-noise ratio can be reduced as a signal pi through a two-stage amplifier circuit. As the figure shows, both the input signal and the put noise are amplified 10 dB in amplifier 1.

Amplifier 1, however, adds an additional 1 of noise i. Again, the signal and noise are both amplified by 10 dB ia: plifier2. Amplifier 2, however, adds 2. To achieve a more accurate time-domain waveform, it would be necessary t0 solve for» for more values of time than are shown inthis diagram, we Ga awhuobeda ake FIGURE The bandwidth of a frequency spec- trum is the range of frequencies contained in the spectrum.

The bandwidth is calculated by subtracting the lowest frequency from the highest. The bandwidth of the frequency spec- trum shown in Figure for Example is Hz. The bandwidth of a communications chan- nel must be sufficiently large wide to pass all significant information frequencies. Speech contains frequency components ranging from approximately Hz to 8 kHz, although most of the energy is distributed in the Hz to Hz band with the fundamental frequency of typical human voice about Hz.

How- ever, standard telephone circuits have a passband between Hz and Hz, as shown in Figure , which equates to a bandwidth of Hz. Twenty-seven hun- dred hertz is well beyond what is necessary to convey typical speech information. Ifa cable television transmission system has a passband from kHz to kHr, ithas a bandwidth of kHz 4. As a general rule, a communications channel cannot propagate a signal through it that is changing at a rate that exceeds the bandwidth of the channel.

In general, the more complex the information signal, the more bandwidth required to transport it through a communications system in a given period of time. Approximately 3 kHz of bandwidth is required to propagate one voice-quality analog telephone conversation.

In contrast, it takes approximately 32 kHz of bandwidth to propagate one voice-quality digi tal telephone conversation. However, the amplitude of the spectral components depends con the duty cycle.

Sin xis simply 1 sinusoidal waveform whose instantaneous amplitude depends on. With only x in the denominator, the denominator increases with x. Figure shows the frequency spectrum for a rectangular pulse with a pulse width- to-period ratio of 0.

It can be seen that the amplitudes of the harmonics follow a damped sinusoidal shape. All spectram components between the first and second null frequencies are in the second Jobe and are negative, components between the second and third nulls are in the third lobe and positive, and so on.

The following characteristics are true for all tepetitive rectangular waveforms: 1. The de component is equal to the pulse amplitude times the duty cycle. Determine the peak amplitudes of the first 10 harmonics. Sketch the frequency spectrum. Solution a, From Equation , the de component is. The frequency spectrum is shown in Figure Figure shows the effect that reducing the duty cycle ie. Such a spectrum is impossible to pro- duce, let alone to propagate, which explains why itis difficult to produce extremely narrow pulses.

Increasing the period of a rectangular waveform while keeping the pulse width con- stant has the same effect on the frequency spectrum, Power and Energy Spectra In the previous sections, we used the Fourier series to better understand the frequency- and time-domain representation of a complex signal.

Both the frequency and the time domain can be used to illustrate the relationship of signal voltages magnitudes with respect to ei- ther frequency or time for a time-varying signal. However, there is another important application of the Fourier series. Thus, the relationship between the amount of energy transmitted and the amount re- ceived is an important consideration. Therefore, i tionship between energy and power versus frequency. It resembles its voltage-versus-frequency spectrum except it has more lobes and a much larger primary: lobe.

Note also that all the lobes are positive because there is no such thing as negative power, From Figure , it can be seen that the power in a pulse is relatively wide frequency spectrum, However, note that most of that power is within the primary lobe.

Chaprer 2 is important that we examine the rela- P x R. Often there is a need to obtain the frequency-domain behavior of signals that are being collected in the time domain i. This is why the discrete Fourier transform was developed. With the discrete Fourier transform, a time-domain signal is sam- pled at discrete times. The samples are fed into a computer where an algorithm computes the anerard oneten aiseamccante bie iam arin hee one witteantedee samples.

For any reasonable number of samples, the computation time is excessive, Conse- quently, in a new algorithm called the fast Fourier transform FET was developed by Cooley and Tukey. The FFT is now available as a subroutine in many scientific subroutine libraries at large computer centers. Effects of Bandlimiting on Signals All communications channels have a limited bandwidth and, therefore, have a limiting ef- fect on signals that are propagated through them. We can consider a communications chan- nel to be equivalent to an ideal linear-phase filter with a finite bandwidth.

Consequently, both the frequency content and the shape of the waveform are changed. Figure shows the time-domain waveform for the square wave used in Ex- ample If this waveform is passed through a low-pass filter with an upper cutoff fre- quency of 8 kHz, frequencies above the eighth harmonic 9 KHz and above are cut off, and the waveform shown in Figure b results, Figures c, d, and e show the waveforms produced when low-pass filters with upper cutoff frequencies of 6 kHz, 4 kHz, and 2 kHz are used, respectively.

Itcan be seen from Figure that bandlimiting a signal changes the frequency con- tent and, thus, the shape of its waveform and, if sufficient bandlimiting is imposed, the waveform eventually comprises only the fundamental frequency. In a communications sys- tem, bandlimiting reduces the information capacity of the system, and, if excessive band- limiting is imposed, a portion of the information signal can be removed from the composite waveform.

Mixivig is the process of combining two or more signals and is an essential process in electronic communications. In essence, there are two ways in which signals can be combined or mixed: linearly and nonlinearly. With nonlinear mixing, the input signals combine in a nonlinear fashion and produce additional frequency components. The output from a nonlinear amplifier with a single-frequency input signal is not a single sine or cosine wave.

Integer multiples of a base frequency are called harmonics. As stated previously, the original input frequency f, isthe first harmonic or the fundamental frequency, 2, is the second harmonic, 3f, isthe third, and so on.

Figure b shows the output waveform in the time domain for a nonlinear amplifier with a single-input frequency. It can be seen thatthe output waveform is simply the summa- tion ofthe input frequency and its higher harmonics multiples of the fundamental frequency. Figure c shows the output spectrum in the frequency domain, Note that adjacent har- sonics are separated in frequency by a value equal to the fundamental frequency, fr Nonlinear amplification of a single frequency results in the generation of multiples or harmonics of that frequency.

If the harmonics are undesired, itis called harmonic dis- tortion. No additional harmonies are generated beyond the second. An infinite number of harmonic and cross-product frequencies are pro- duced when two or more frequencies mix in a nonlinear device.

Ifthe cross products are un- desired, it is called intermodulation distortion. Figure shows the out- put spectrum from a nonlinear amplifier with two input frequencies. Intermodulation distortion is the generation of any unwanted cross-product fre- quency when two or more frequencies are mixed in a nonlinear device.

Example For nonlinear amplifir with two input frequencies, 5 kHz and 7 kz, 8, Determine the firs three harmonics present inthe output foreach input frequency. Determine the cross products produced inthe output for values of m and n of 1 and 2. Draw the outpot frequency spectrum forthe harmonics and cross-product frequencies determined in steps and Solution a. The first three harmonics include the two original input frequencies of 5 kHz and 7 kz; to times each ofthe original input frequencies, 10 kHz and 14 kHz; and thee times each of the original input frequencies, 15 kHz and 21 kHe.

Briefly describe the differences between analog and digital signals. Describe rime domain and give an example ofa time-domain instrument. Describe a complex signal. Whats the significance of the Fourier series? Describe the following wave symmetries: even, odd, and half wave. Define frequency specirum and bandwidth.

Describe the frequency content of a square wave. A rectangular wave, Explain the terms power spectra and energy spectra. Describe the differences between discrete and fast Fourier transforms, , Briefly describe the effects of bandlimiting electrical signals Describe what is meant by linear summing. For the tain of square waves shown below, a, Determine the amplitudes of the first five harmonics. Determine the de component. Sketch the frequency spectrum, Describe the spectrum shown below.

Determine the first three harmonics present in the output for each frequency. Draw the output spectrum for the harmonics and cross-product frequencies det stops a and b. In many of these applica- tions, more than one frequency is required, and very often these frequencies must be synchronized to each other.

Therefore, signal generation, frequency synchronization, and frequency synthesis ate essential parts of an electronic communications system. The Purpose of this chapter is to introduce the reader to the basic operation of oscillators, phase-locked loops, and frequency synthesizers and to show how these circuits are used. An oscillators a device that produces oscillations i.

If an oscillator is self-sustaining, the changes in the waveform are continuous and repetitive; they occur at a periodic rate. A self-sustaining oscillator is also called a free-runnin oscillator.

Oscillators that are not self-sustaining require an external input signal or trigger to produce a change in the output waveform. Oscillators that are not self-sustaining called triggered or one-shot oscillators. Communication systems engineering solutions manual pdf Goodreads helps you keep track of books you want to read. Want to Read saving…. Want to Read Currently Reading Read.

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