PULSE MODULATION TECHNIQUES
STUDY GUIDE
1. What can be done to make an AM communications link more efficient?
A. Decrease the transmitted power
B. Decrease the channel BW required to transmit the same intelligence
C. All of the Above
D. None of the above
2. Distortion when some of the spectral lines that make up the composite waveform fall outside of
the channel passband
A. True
B. False
3. Compared to DSBLC AM signals, SSB results in
A. 6 dB improvement
B. -6 dB improvement
C. 10 dB improvement
D. -10 dB improvement
4. A resistor is a linear device
A. True
B. False
5. A Modulation technique where only the relative positions of the pulses move, according to the
intelligence amplitude
A. PWM
B. PPM
C. PAM
D. PFM
6. The transmission medium of a typical communications system can by a hard wired line or a
radio transmission;
A. True
B. False
7. Most of the Power in a Modulated Waveform is contained in the
A. Carrier
B. LSB
C. USB
D. Modulation Technique
8. The bandwidth of a single sinewave is
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A.
B.
C.
D.
10Hz
100Hz
1000Hz
A Sinewave has zero bandwidth
9. The Nyquist Rate is
A. 2 * BW
B. 3 * BW
C. 4 * BW
D. 5 * BW
10. Carrier circuits may or may not be required, if the channel is hardwired
A. True
B. False
11. In DSBLC AM the carrier is at best 2/3 of the total Power
A. True
B. False
12. The BW of a voice signal over PSTN is
A. 3MHz
B. 3KHz
C. 3.3KHz
D. 300Hz
13. A SSB Variation where only the USB or LSB is transmitted (no carrier)
A. Single Sideband - SSB
B. Single Sideband, Suppressed Carrier - SSBSC
C. Independent Sideband - ISB
D. Vestigial Sideband - VSB
E. Amplitude Compandered Sideband - ACSSB
14. What is a width of a sample (theoretically)?
A. No width
B. 1 pico second
C. 1 nano second
D. 1 micro second
E. 1 mille second
15. At 100% modulation the LSB and USB are at ____ the power of the Carrier
A. 1/2
B. 1/3
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C. 1/4
D. 1/8
16. When an intelligence signal and a carrier signal are inserted into a non-linear mixing device the
following will result
A. A DC Term
B. the original intelligence signal plus its harmonics
C. the original carrier signal, plus its harmonics
D. The sum and difference of the carrier and intelligence signal
E. All of the above
17. If a DC carrier is used, then the intelligence is considered to be at baseband
A. True
B. False
18. If a DC carrier is used, then the intelligence is centered about 0-Hz;
A. True
B. False
19. In practice it is impossible to achieve a "zero-width" sample
A. True
B. False
20. The process of modifying analog information to send over the digital portion of the network is
called
A. modulation
B. encoding
C. decoding
D. demodulating
21. When the modulation index is less than 100% the amplitude of the sidebands will always be
lower than that of the carrier.
A. True
B. False
22. If a DC carried is used, then the spectral footprint of the analog signal is the same as that of the
original intelligence;
A. True
B. False
23. Using a BPF before the non-linear mixer will filter out all but the spectral components
comprising the AM signal
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A. True
B. False
24. A sample width can be ANY duration that also satisfies the Nyquist requirement?
A. True
B. False
25. A Telephone local loop is an example of a DC carrier
A. True
B. False
26. Low duty cycle pulse trains require more transmitter power
A. True
B. False
27. Modulation is the process of varying some characteristic of a carrier wave as the information to
be transmitted on that carrier wave (the intelligence) varies.
A. True
B. False
28. A RS-232 Connection to a printer is an example of a DC carrier
A. True
B. False
29. Continuous analog waveforms have far less transmit power requirements than a skinny pulse
A. True
B. False
30. Carrier circuits are NOT always necessary for radio (RF) transmission
A. True
B. False
31. What is the pulse modulation technique that does not have a constant rate pulse train is
A. PWM
B. PPM
C. PAM
D. PFM
32. What is the purpose of a Balanced Modulator
A. To eliminate the USB
B. To eliminate the LSB
C. To eliminate the Carrier
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D. To eliminate the Balance
33. AGC stands for
A. Analog Gain Converter
B. Automatic Gain Control
C. Anti Gravity Coil
D. Advanced Governing Carrier
34. A carrier signal can be both analog or digital
A. True
B. False
35. Low duty cycle pulse trains does not allow us to interweave many different pulse trains onto a
single communication channel
A. True
B. False
36. Antennas are NOT narrow band devices
A. True
B. False
37. TDM refers to having all of the BW all of the time
A. True
B. False
38. In DSBLC AM signals, most of the transmitted power is wasted on that portion of the signal
which contains on information about the original intelligence signal
A. True
B. False
39. High frequency analog carrier wave reduces both the antenna lenth and the ratio of channel BW
to carrier frequency
A. True
B. False
40. A SSB Variation where a pilot carrier is transmitted with only the LSB or USB
A. Single Sideband - SSB
B. Single Sideband, Suppressed Carrier - SSBSC
C. Independent Sideband - ISB
D. Vestigial Sideband - VSB
E. Amplitude Compandered Sideband - ACSSB
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41. The larger the amplitude of the sidebands, the better the SNR
A. True
B. False
42. Which of the following are examples of a carrier signal
A. The DC battery Voltage that powers your telephone
B. The sinewve carrier fo a radio station
C. The digital pulse train of a T-carrier
D. All of the above
43. When sharing a low duty cycle pulse train, each individual pulse train, is offset slightly in time
and has the same Pulse Repetition Frequency.
A. True
B. False
44. A Modulation technique generated by using a voltage controlled oscillator
A. PWM
B. PPM
C. PAM
D. PFM
45. For a given Q, an antenna designed to operate at a high frequency has a greater BW than one
designed at a lower frequency
A. True
B. False
46. Non-Coded Pulse Modulation Schemes are considered Digital, because one of the defining pulse
parameters has infinite resolution
A. True
B. False
47. A sinewave carrier is an analog signal and is completely defined by the following characteristics
A. Amplitude
B. Frequency
C. Phase
D. All of the Above
48. PLM, PDM, & PWM all refer to Pulse Width Modulation
A. True
B. False
49. Antenna length is proportional to λ/4
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A. True
B. False
50. SSB reduces BW requirements
A. True
B. False
51. Coded (true digital) Schemes, refer to pulse train that are a sequence of digital numbers sent at
a variable clock rate
A. True
B. False
52. The formula for λ is :
A. λ * c
B. f * c
C. f /c
D. c/f
53. AM is the result of an intelligence signal varying the Amplitude of the carrier
A. True
B. False
54. What is the Modulation technique that refers to the conversion of the analog intelligence into a
series of variables width pulses
A. PLM
B. PZM
C. PJM
D. PKM
55. A pure digital signal has only one possible voltage state
A. True
B. False
56. Carrier transmission is generally used when the communications channel is
A. Greater than 100Hz
B. Greater than 1KHz
C. Greater than 1MHz
D. Less than 1MHz
57. A digit coded schemes that encodes information about the change from sample to sample, as
opposed to the actual sample height, is known as
A. PCM
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B.
C.
D.
E.
DM
PPM
PAM
TDM
58. If a sinusoidal carrier at a frequency other than 0Hz is used then the signal is considered to be
A. baseband
B. broadband
C. crossband
D. unbanded
59. In PDM the width of the pulse corresponds to the original intelligence's
A. Phase
B. Width
C. Amplitude
D. Pulse
60. Pulse Amplitude Modulation (PAM) Refers to conversion of the digital intelligence into a pulsetype signal, where the amplitude of the pulses contains the analog information.
A. True
B. False
61. A carrier signal can be either sinusoid or periodic pulse train
A. True
B. False
62. A SSB Variation where two standard AM signals are combined, but modulated on the same
frequency carrier
A. Single Sideband - SSB
B. Single Sideband, Suppressed Carrier - SSBSC
C. Independent Sideband - ISB
D. Vestigial Sideband - VSB
E. Amplitude Compandered Sideband - ACSSB
63. Over modulation occurs when the modulation index is
A. less than 100%
B. 0%
C. .1
D. above 1
64. Signals sent using a continuous wave forms are known as
A. Analog Signals
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B.
C.
D.
E.
F.
Modulation Waveforms
Periodic Pulse Train
Pulse Modulation
Pulse Communications
Digital Data Transmission
65. FM is the result of an intelligence signal varying the Frequency of the carrier
A. True
B. False
66. Pulse Amplitude modulation is usually used as the first step in digitizing an analog signal
A. True
B. False
67. A series of continuous pulses occurring at regular intervals is know as
A. Analog Signals
B. Modulation Waveforms
C. Periodic Pulse Train
D. Pulse Modulation
E. Pulse Communications
F. Digital Data Transmission
68. SSB reduces signal power requirements for the same SNR
A. True
B. False
69. The signal "copy" of the original intelligence
A. Analog Signals
B. Modulation Waveforms
C. Periodic Pulse Train
D. Pulse Modulation
E. Pulse Communications
F. Digital Data Transmission
70. Which of the following is not an attribute of PAM
A. Samples are evenly spaced
B. Pulse widths remain constant
C. The amplitude on the pulses vary in proportion to the intelligence sample amplitude
D. Sampling is done at less than 2 times the bandwidth
71. The transmission of information by modifying the pulses in a continuous pulse train is known as
A. Analog Signals
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B.
C.
D.
E.
F.
Modulation Waveforms
Periodic Pulse Train
Pulse Modulation
Pulse Communications
Digital Data Transmission
72. At 100% modulation the LSB and USB are at ____ the amplitude of the Carrier
A. 1/2
B. 1/3
C. 1/4
D. 1/8
73. A mixer is an example of a non-linear modulating device
A. True
B. False
74. The process of modifying digital information to send over the analog portion of the network is
called
A. modulation
B. encoding
C. decoding
D. demodulating
75. The basic types of PAM relating to how the modulation waveform is sampled
A. Natural Sampling
B. Flat-top Sampling
C. Slant-top Sampling
D. A & B only
E. None of the Above
76. In modulation we strive to achieve large sideband amplitudes because the intelligence of the
sideband is
A. True
B. False
77. A signal procession technique whereby information is encoded by varying one or more pulse
parameters in a periodic pulse train
A. Analog Signals
B. Modulation Waveforms
C. Periodic Pulse Train
D. Pulse Modulation
E. Pulse Communications
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F. Digital Data Transmission
78. A linear device is ideal for Amplitude Modulation
A. True
B. False
79. Each sample of the intelligence is first encoded into a sequence of ones and zeros (binary)
before transmission
A. Analog Signals
B. Modulation Waveforms
C. Periodic Pulse Train
D. Pulse Modulation
E. Pulse Communications
F. Digital Data Transmission
80. PM is the result of an intelligence signal varying the Phase of the carrier
A. True
B. False
81. SSB reduces nois power entering the receiver
A. True
B. False
82. Pulse Modulation varies which of the following periodic pulse train parameters?
A. Amplitude
B. Width
C. Time of Occurrence
D. All of the Above
83. A SSB Variation where a trace of one sideband and carrier is left over. (Used in analog TV
broadcasts).
A. Single Sideband - SSB
B. Single Sideband, Suppressed Carrier - SSBSC
C. Independent Sideband - ISB
D. Vestigial Sideband - VSB
E. Amplitude Compandered Sideband - ACSSB
84. The periodic pulse train is the carrier in Pulse Communication
A. True
B. False
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85. The Modulation technique that refers to a series of constant amplitude, and constant width
pulses, whose relative position with the pulse train conveys the analog intelligence.
A. PWM
B. PPM
C. PAM
D. PFM
86. The Modulation technique that require the Superposition of sawtooth generator on intelligence
signal is
A. PWM
B. PPM
C. PAM
D. PFM
87. Any modulation technique will result in a new, composite waveform
A. True
B. False
88. Pulse communication is usually utilized when the communication channel is greater than 1MHz
A. True
B. False
89. Pulse communication is usually utilized when inexpensive wired or fiberoptic transmission is
NOT possible
A. True
B. False
90. PRF refers to
A. Pulse Resonance Frequency
B. Pulse Repetition Frequency
C. Pulse Response Fragment
D. Pulse Return Fragment
91. Pulse communication can also use the modulated pulse train as the input to a 2nd modulator,
which impresses the modulated pulse train onto a high frequency sinusoidal carrier.
A. True
B. False
92. Both sidebands in a modulated waveform contain the same information
A. True
B. False
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93. When view in the frequency domain, the new modulation waveform is comprised of additional
spectral components
A. True
B. False
94. A differentiator is commonly known as
A. DIFF
B. HPF
C. LPF
D. None of the above
95. Why use pulse modulation instead of CW (Continuous Wave) analog Modulation?
A. The transmitter can operate with much less power
B. TDM
C. Single Cable, Multiple Channels
D. All of the Above
96. In Pulse Modulation, each pulse represents an amplitude sample of the original waveform.
A. True
B. False
97. In Pulse Modulation, we can reconstruct the original intelligence, if the sampling is done at less
than two (2) times the analog BW of the signal.
A. True
B. False
98. A Modulation technique where PWM is applied to the intelligence and inverted
A. PWM
B. PPM
C. PAM
D. PFM
99. A SSB Variation where the intelligence amplitude is compressed at the transmitter (can provide
FM quality)
A. Single Sideband - SSB
B. Single Sideband, Suppressed Carrier - SSBSC
C. Independent Sideband - ISB
D. Vestigial Sideband - VSB
E. Amplitude Compandered Sideband - ACSSB
100.
In the frequency domain, the collection of side frequencies above the carrier is generally
referred to as the Lower Side Band (LSB)
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A. True
B. False
101.
The concept of frequency translation, refers to the fact that spectral lines must stay
together as a single entity.
A. True
B. False
102.
A.
B.
C.
D.
Halving the carrier amplitude will drop its power to ____ of its original value
1/2
1/3
1/4
1/8
103.
SSB reduces the distortion of the intelligence signal at the receiver
A. True
B. False
104.
A diode is an example of a non-linear device
A. True
B. False
105.
A.
B.
C.
D.
What is the Analog bandwidth
The Highest significant frequency component
The Fundamental frequency component
The Even Harmonics
The Odd Harmonics
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