Principles of Electronic Communication Systems 4th Edition Frenzel Solutions
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Principles of Electronic Communication Systems 4th Edition Frenzel Test Bank
Full clear download (no error formatting) at :
https://testbanklive.com/download/principles-of-electronic-communication-systems4th-edition-frenzel-test-bank/
Part B
Answers to Questions,
Problems, Critical
Thinking, and Online
Activities
Chapter 1
Answers to Questions
1. In the nineteenth century.
2. Transmitter, communications channel or medium,
receiver, noise. See Fig. 1-2 in the text.
3. Wire cable, free space (radio and light), fiber-optic
cable, water, the earth. The first three are the most
widely used.
4. Modulator.
5. Demodulator.
6. The combination of a transmitter and a receiver in a
single package that may share some circuits.
7. Attenuation, addition of noise.
8. Communications channel.
9. Noise.
10. Lightning, outer space (sun, stars), manufactured devices
(motors, car ignitions, fluorescent lights, etc.).
11. Baseband signals.
12. Analog and digital.
13. Simplex. Broadcasting, paging, telemetry.
14. Full-duplex. Telephones: standard, cordless, cellular.
15. Half-duplex. Two-way radio, fax machine, computer
modem.
16. Analog.
17. Digital or binary.
18. The analog signals are converted into binary signals first.
19. Information or intelligence signals.
20. Modulation.
21. Demodulation or detection.
22. One that consists of a carrier modulated by one or more
baseband signals.
23. Multiplexing.
24. Demultiplexing.
25. Radio or wireless.
26. Electric or magnetic fields.
27. 1.5 kHz: 124.2 miles, 18 MHz: 54.67 ft, 22GHz: 1.36 cm.
28. Antennas would be too long to be practical, signals
would not travel far, all signals would interfere with one
another.
29. 20 Hz to 20 kHz.
30. 300–3000 Hz.
31. Yes, but only a few, usually military or government
(navigation).
32. 535–1705 kHz.
33. Short waves.
34. VHF.
35. Two-way radio, TV, cellular telephone, radar, satellites.
36. Microwave.
37. Millimeter waves.
38. A micron is one-millionth of a meter or micrometer
(µm) or 10–6 m. It is used to express light wavelength.
39. Infrared, visible, ultraviolet.
40. Heated objects or LEDs and lasers.
41. 0.7 to 100 µm.
42. An angstrom is 10–10 m and is used to state light
wavelength.
43. 0.4 to 0.8 µm.
44. Free space and fiber-optic cable.
45. Facsimile and television.
46. Paging.
47. Telemetry.
48. Cordless telephones, cellular telephones, microwave
relay, satellites.
49. The reflection of radio waves from a distant object.
50. Sonar. Passive sonar listens to underwater sounds.
Active radar sends out an ultrasonic signal and listens
for its reflection or echo to determine range and bearing.
51. Amateur or ham radio.
52. Modem.
53. Local area networks (LANs).
54. Wireless.
55. Engineer, technologist, technician.
56. Design and analysis of circuits, equipment, and systems.
57. Bachelor’s degree (B.S.E.E.).
58. Associate’s degree (A.S.E.E., A.A.S., etc.).
59. Bachelor’s degree in technology.
60. Usually no.
61. Install, operate, maintain, troubleshoot, repair, and
service equipment.
62. Sales, technical writing, training.
63. Manufacturers create products, distributors transfer
products to resellers who market the products, service
organizations install, repair, and maintain the products,
and end users apply the products.
64. Communications standards ensure compatibility and
interoperability of equipment.
65. Communications standards define modulation and/or
multiplexing methods, frequencies of operation,
protocols, and interface methods, including mechanical
connections.
Answers to Problems
1. 7.5 MHz, 60 MHz, 3750 MHz, or 3.75 GHz.
2. ELF.
3. Radar and satellites.
Answers to Critical Thinking
1. Vary carrier amplitude, frequency, or phase.
2. TV remote control (infrared), garage door opener
(radio—VHF or UHF).
3. Stars (suns) radiate radio waves that can be received by
directional antennas that can record azimuth and
elevation to plot star positions.
4. Individual student’s choice.
5. Narrow or restrict the bandwidth of some signals and their
channel bandwidth, use more multiplexing, share
frequencies at different times or when signals do not carry
far. Use more wire or cable systems. In digital systems,
use data compression techniques. Use the optical range.
6. 982.08 ft/µs, 11.8 in/ns, 3 × 108 m/s.
7. The speed of light is 186,000 miles per second (mi/s) or
300,000,000 meters per second (m/s). The speed of
sound is only a fraction of that, or about 1129 feet per
second (ft/s) or 344 meters per second (m/s). You cannot
see light travel because its speed is so fast that it appears
instantaneous. Over long distances as in space, it takes
light-years to go from one place to another. The sun is
B-2
about 93 million miles from earth. It takes light from the
sun 93,000,000 mi/186,000 mi/s = 500 seconds, or
about 8.33 minutes to reach us.
Sound speed is easily observed. Lightning at a
distance is an example. You see the lightning first, and
then hear it (the thunder clap) later.
8. Remote control of automobile door locks and alarms by
key chain transmitters, wireless speakers for stereo.
Reverse control of a cable TV box by the cable company
using digital signals, using cable TV modems for
Internet access, telemetry of signals for water, gas, or
electric utility monitoring. Radar speed measurement of
baseball pitches.
9. Student ideas and innovations.
10. Call the FCC to get advice and direction. Search the
FCC website at www.fcc.gov. Communications
consultants can be hired to help you with this. Order
copies or the relevant U.S. Government Code of Federal
Regulations (CFR) Title 47 from the U.S. Government
Printing Office.
11. Some examples are telephone, cordless telephone,
cellular telephone, CB radio, TV set with remote
control, radio, FM stereo system, garage door opener,
PC with modem to on-line service, cable TV converter
box, fax machine.
12. The “cup and string” communications system is
theoretically sound although very inefficient. If the
string is pulled taut, but not too taut, it will carry sound
waves from one cup to the other. Speaking into one cup
causes the bottom of the cup to vibrate like a diaphragm
in a microphone. This transmits the sound to the string.
The string vibrates the bottom of the receiving cup,
which acts like a speaker cone to transfer the sound to
your ear. The key to the success of this system lies in
the efficient coupling of the string to the bottom of the
cups and the tension on the string. Tension must be
present in order to pick up and transmit the sound. If the
tension is too great, it will inhibit the vibration of the
cup bottoms.
Chapter 2
Answers to Questions
1. XC decreases as frequency increases.
2. XL decreases as frequency decreases.
3. Skin effect is a phenomenon that causes electrons to
flow near the outer surface of a conductor rather than at
the center or uniformly over the cross section. It reduces
the area for electron flow, thus increasing resistance.
The effect is frequency-sensitive, causing a resistance
increase at higher frequencies. Skin effect causes Q to be
lower at the higher frequencies.
4. The inductance of the wire increases, creating a
low-value RF choke.
5. Toroid.
6. In a series resonant circuit at resonance, impedance is
minimum and current is maximum.
7. In a parallel resonant circuit at resonance, impedance is
maximum and line current is minimum.
8. There is an inverse relationship between Q and
bandwidth. High Q means narrow bandwidth, and low Q
translates to wider bandwidth.
9. Bandpass filter.
10. Notch filter.
11. Selectivity is the ability of a circuit to pass signals on a
desired frequency or range of frequencies while rejecting
other signals outside the desired range.
12. Fourier theory states that any nonsinusoidal signal may
be represented or analyzed as the sum of a fundamental
sine wave at the signal frequency plus odd, even, or odd
plus even harmonic sine waves of different phases and
amplitudes.
13. Time domain refers to displaying or expressing a signal
as a varying voltage, current, or power with respect to
time. In the frequency domain, signals are displayed or
expressed as a sequence of voltage or power levels of
sine waves at specific frequencies representing the
Fourier components of the signal.
14. 2400, 4000, 5600, 7200 Hz.
15. See text Fig. 2-61. Even harmonics: half-wave rectified
sine wave. Odd harmonics: 50 percent duty cycle square
wave.
16. The distortion occurs because harmonics may be filtered
out, leaving a different waveshape.
Answers to Problems
1. A = 50,000.
2. A = 0.607.
3. 30,357.14.
4. A = 2310, Vout (stage 3) = 0.2772 V,
Vout (stage 2) = 39.6 mV, Vout (stage 1) = 1.8 mV.
5. A = 5.4, Vin = 0.41 V.
6. 50,000 – 94 dB, 0.607 – 4.34 dB,
30,357.14 – 89.6 dB, 2310 – 67.27 dB,
5.4 – 14.65 dB.
7. 14 dB.
8. Pout = 189,737 W.
9. 37 dBm.
10. 13 dB.
11. 11.37 Ω.
12. 7.1 pF.
13. 4522 Ω.
14. 23.9 MHz.
15. Q = 24.
16. 45.78 MHz.
17. 0.978 µH.
18. fr = 4 MHz, XL = 829 Ω, Q = 59.2, BW = 67.55 kHz.
19. BW = 2.4 MHz.
20. 3.18 mV.
21. Q = 111.116.
22. 389.9 kΩ.
23. See text Fig. 2-62(c). f(t) = 10/π[sin 2π
100,000t – ½ sin 2π 200,000t + ⅓ sin
2π 300,000t – ¼ sin 2π 400,000t. . .].
24. 43.75 MHz.
25. 41.67 ns.
B-3
Answers to Critical Thinking
1. The inductance and capacitance are distributed along
wires, cables, other components, and any related
conductors.
2. The cancellation of XL and XC at resonance and the low
resistance produces a high current flow which, in turn,
produces high voltage drops when Q is high (>10).
3. Low-pass filter.
4. High-pass filter.
5. At resonance, a parallel tuned circuit appears to be a
high pure resistance. Placing a resistor in parallel with it
reduces the effective impedance of the circuit, adding
loss which translates to a lower Q. Lower Q gives wider
bandwidth.
6. (a) fr = 45.97 MHz; (b) Q = 77;
(c) BW = 597 kHz; (d) Z = 17.78 kΩ.
7. 3.98 MHz.
8. C = .0015 µF.
9. (a) 90.44 MHz; (b) 36.17 MHz.
10. Half-wave rectifier. It produces only even harmonics
output. Therefore, its second harmonic is strong, making
it a good doubler. Since no odd harmonics are present,
the high-level harmonics (fourth and higher) are easy to
filter out.
Chapter 3
Answers to Questions
1. Modulation is the process of modifying the
characteristics of a signal called a carrier with another
information signal for the purpose of transmitting the
information signal more efficiently or effectively.
2. Modulation is necessary because the information signal
is usually incompatible with the communications
medium.
3. Modulator. Carrier. Modulating, information, or
intelligence signal.
4. The amplitude of the carrier varies with the intelligence
signal, but frequency and phase are not affected.
5. False.
6. Envelope. It has the shape of the modulating information
signal.
7. Time domain signals.
8. Vc sin 2πfc
t.
9. True.
10. Multiplication.
11. Vm = Vc
.
12. Percentage of modulation.
13. With overmodulation (>100 percent), clipping of the signal
occurs. This introduces harmonics, which also modulate
the carrier. The effect is to distort the signal, reduce its
intelligibility, and increase the bandwidth of the AM signal,
possibly causing interference to adjacent signals.
14. Sidebands.
15. Time domain signal.
16. Frequency domain display. Spectrum analyzer.
17. Nonsinusoidal signals contain harmonics, which are
multiples of the fundamental modulating signal. These
also create sidebands that widen the bandwidth of the
signal.
18. Carrier, lower sideband, upper sideband frequencies.
19. Amplitude shift keying (ASK) or ON–OFF keying
(OOK).
20. It may help explain the operation of some types of
circuits.
21. False. This is not typical, but some kinds of modulator
circuit can cause this.
22. 66.7 percent carrier, 33.3 percent both sidebands, 16.7
percent one sideband.
23. No. The carrier is a signal frequency. The intelligence is
in the sidebands.
24. Double-sideband suppressed carrier (DSB).
25. Balanced modulator.
26. A single sideband.
27. Less bandwidth and spectrum space, more powerefficient, less noise, less fading.
28. Vestigial sideband AM. A portion of the lower sideband
is filtered out to minimize bandwidth.
29. F3 and A4c or A3C.
30. The bandwidth of 2 kHz voice modulated AM signal is
4 kHz. The bandwidth of an AM signal modulated by a
binary signal of 2 kHz is theoretically infinite. Assuming
alternating binary 0s and 1s for a square wave, the
square wave will produce odd harmonics. If the odd
harmonics are significant to the 7th, then the bandwidth
would be 7 × 2 kHz = 14 kHz × 2 = 28 kHz.
Answers to Problems
1. m = (Vmax – Vmin)/(Vmax + Vmin).
2. 31.5 percent.
3. 100 percent.
4. 37.5 V.
5. 80 percent.
6. Vm > Vc
.
7. 3896 kHz, 3904 kHz; BW = 8 kHz.
8. BW = 15 kHz; 2098.5 kHz, 2101.5 kHz,
2097 kHz, 2103 kHz, 2095.5 kHz, 2104.5 kHz,
2094 kHz, 2106 kHz, 2092.5 kHz, 2107.5 kHz.
9. 800 W.
10. 3241.125 W.
11. 70.7 percent.
12. 2209 W.
13. 72.9 percent.
14. 375 W.
15. 825 W.
16. 1095 W.
17. 25 to 33.3 W average.
18. 2,299, [Show Less]