Transcript Chapter 1 Problems

Chapter 4 Problems
ECET 214
Prof. Park
NJIT
Problem 1
SSB transmitters are usually rated in terms of:
a. power gain
b. voltage gain
c. modulation index
d. peak envelope power
Problem 2
Which of the following is required for SSB
transmission?
a. carrier elimination
b. elimination of one sideband
c. a and b
d. none of the above
Problem 3
Which of the following is NOT an advantage that the
phase method of generating has over the filter
method?
a. requires high Q filters.
b. lower intelligence frequencies can be used.
c. greater ease in switching from one sideband to the other.
d. SSB generated directly at desired transmitting frequency.
Problem 4
The major disadvantage of the phase method of
SSB generation is:
a. requires two balance modulators
b. does not use high Q filters
c. 90° phase-shifting network for intelligence
signal
d. all of the above
Problem 5
Which of the following can be used as an SSB
demodulator?
a. RF amplifier
b. audio amplifier
c. AGC circuitry
d. mixer
Problem 6
At 100% modulation, an AM signal has a total
power of 1200 watts. If it was converted to SSB and
the sideband component had the same amplitude
as before, the total power would be:
a. 100 watts
b. 200 watts
c. 400 watts
d. 800 watts
Problem 7
The PEP rating of an SSB transmitter is often misleading
due to:
a. the fact that with normal voice signals, an SSB transmitter
develops an average of only one-third to one-fourth of its
PEP rating.
b. the SSB transmitter's power supplies and components are
not always designed for continuous duty PEP power levels.
c. the PEP rating is the same rating no matter what type of
waveform the transmitter is providing.
d. all of the above.
Problem 8
If the carrier and one of the sidebands are
completely eliminated, the resulting signal is
referred to as:
a. SSB.
b. SSBSC.
c. ACSSB.
d. vestigial sideband.
Problem 9
If the carrier is reduced in amplitude and one of
the sidebands is completely eliminated, the
resulting signal is referred to as:
a. independent sideband.
b. SSBSC
c. ACSSB.
d. vestigial sideband.
Problem 10
The type of sideband that involves having the
upper sideband contain different information
than the lower sideband is referred to as:
a. independent sideband.
b. SSBSC
c. ACSSB.
d. vestigial sideband.
Problem 11
The type of sideband that is used for television
video transmission is called:
a. independent sideband
b. SSBSC
c. ACSSB
d. vestigial sideband
Problem 12
A more recently developed system of sideband
that involves compressing the amplitude of
the intelligence signal before modulation occurs is
called:
a. independent sideband.
b. SSBSC.
c. ACSSB.
d. vestigial sideband.
Problem 13
The most important advantage of SSB over AM is:
a. that it is a more effective utilization of the
available frequency spectrum.
b. that it is less subject to the effects of selective
fading.
c. the resulting savings in power.
d. simplicity in design.
Problem 14
Which is not an advantage of SSB over AM?
a. SSB provides a more effective utilization of
the available frequency spectrum.
b. SSB is less subject to the effects of selective
fading.
c. SSB has a resulting savings in power.
d. simplicity in design.
Problem 15
The output of a balanced modulator in an SSB
transmitter being modulated with a voice
intelligence signal is:
a. conventional AM.
b. SSB.
c. DSB-SC.
d. a sinewave at the carrier frequency.
Problem 16
Which of the following will not work as a
balanced modulator?
a. a dual-gate FET and a band-pass filter
b. a push-pull modulator
c. a ring-diode modulator
d. an LM1496 integrated circuit stage
Problem 17
In a push-pull modulator, the carrier suppression
is accomplished by:
a. a dual-gate FET having symmetry.
b. center-tapped transformers causing canceling
magnetic fields.
c. the nonlinearity of the diodes that are used.
d. symmetrical differential amplifier stages.
Problem 18
In a linear integrated circuit balanced modulator
such as the LM1496, carrier suppression is
accomplished by:
a. center-tapped transformers causing canceling
magnetic fields.
b. a dual-gate FET having symmetry.
c. the nonlinearity of the diodes that are used.
d. symmetrical differential amplifier stages.
Problem 19
Voice transmission requires an audio frequency
range of:
a. 20 Hz to 20 kHz.
b. 30 Hz to 10 kHz.
c. 100 Hz to 3 kHz.
d. 500 Hz to 1 kHz.
Problem 20
In an SSB transmitter having voice modulation using
audio frequencies ranging from 100 Hz to 3 kHz, the
upper and lower sidebands generated by the
balanced modulator are separated by:
a. 500 Hz.
b. 200 Hz.
c. 6 kHz.
d. 40 Hz.
Problem 21
Calculate the required Q for the bandpass
filter depicted in Figure 4-1 for 80 dB
sideband suppression if the carrier
frequency component of the IF is 455 kHz.
a. 1137.5
b. 56,875
c. 227,500
d. 113,750
Problem 22
Crystal filters:
a. have Q values as high as 50,000.
b. employ phasing capacitors to produce a
rejection notch of undesired resonant
frequencies.
c. are quite delicate in construction.
d. all of the above.
Problem 23
Which is not an advantage of ceramic filters over
crystal filters?
a. more rugged in construction.
b. smaller in size.
c. higher Q values.
d. less expensive.
Problem 24
The ratio of the 60 dB and 6 dB bandwidths for
a ceramic filter is known as:
a. the shape factor.
b. the ripple amplitude.
c. the quality factor.
d. the roll-off rate of the skirt.
Problem 25
The variation in attenuation within the
bandpass frequencies of a ceramic filter is
called:
a. the shape factor.
b. the ripple amplitude.
c. the quality factor.
d. the roll-off rate of the skirt.
Problem 26
The first designed sharp filter used in SSB
transmitters to produce SSB is the:
a. crystal filter.
b. ceramic filter.
c. mechanical filter.
d. tank circuit.
Problem 27
The filter consisting of resonant disks, driving rods, bias
magnets and transducer coils is the:
a. crystal filter.
b. ceramic filter.
c. mechanical filter.
d. tank circuit.
Problem 28
In Figure 4-2, the filter Q
required in the linear amplifier
is approximately:
a. 20.
b. 10.
c. 15.
d. 100.
Problem 29
In Figure 4-2, the output signal
of stage (b) is:
a. DSB-SC at 500 kHz.
b. DSB-SC at 10 MHz.
c. SSB at 500 kHz.
d. SSB at 10 MHz.
Problem 30
In Figure 4-2, the output signal
of stage (d) is:
a. DSB-SC at 500 kHz.
b. DSB-SC at 10 MHz.
c. SSB at 500 kHz.
d. SSB at 10 MHz.
Problem 31
In Figure 4-2, the first mixer
and filter are necessary to:
a. produce SSB at the final
transmitter output
frequency.
b. produce SSB using filters
having adequately high Q
values.
c. produce DSB-SC at the final
transmitter output
frequency.
d. produce DSB-SC using filters
having adequately high Q
values.
Problem 32
In Figure 4-2, the second
mixer and filter are necessary
to:
a. produce SSB at the final
transmitter output
frequency.
b. produce SSB using filters
having adequately high Q
values.
c. produce DSB-SC at the
transmitter output
frequency.
d. produce DSB-SC using filters
having adequately high Q
values.
Problem 33
In Figure 4-3, the purpose of Q1 and Q2 are to:
a. mix the carrier with the intelligence signal to
produce DSB-SC.
b. amplify the carrier signal.
c. filter out one of the sidebands.
d. amplify the audio intelligence signals.
Problem 34
In Figure 4-3, the required push-pull action of Q1 and
Q2 is furnished by:
a. the balance potentiometer, R2.
b. the transformer, T1.
c. the fact that one of them is a common gate amplifier
and the other is a common source amplifier.
d. the 0.1 μf capacitor that connects their sources
together.
Problem 35
In Figure 4-3, Q4 is needed:
a. to provide gain to the carrier output signal.
b. to act as an oscillator to produce a carrier signal.
c. to upset the balance of the balanced modulator in
order to produce a carrier output signal.
d. to help filter out the undesired sideband.
Problem 36
In Figure 4-3, the 9 MHz crystal filter can produce either USB or
LSB due to:
a. its bandwidth being wide enough to filter out both sidebands.
b. the 30 pf capacitors across its input and output terminals.
c. the IF amplifier transistor, Q3, having sufficiently high
bandwith.
d. the carrier frequency being slightly altered to create either
sideband at 9 MHz.
Problem 37
Which is not a general method used to generate SSB in
transmitter design?
a. filter method
b. lattice method
c. amplitude-compandoring method
d. phase method
Problem 38
Which is the most popular method used to generate
SSB in transmitter design?
a. filter method
b. lattice method
c. amplitude-compandoring method
d. phase method
Problem 39
The main disadvantage of the phase method in generating
SSB is:
a. the complex method of mixing the carrier with the
intelligence signal.
b the complex method used to amplify the resulting SSB
signal.
c. the complex design of the 90 degree phase shifting
network for the intelligence signal.
d. the complex design of the 90 degree phase shifting
network for the carrier signal.
Problem 40
ACSSB is:
a. a method of compressing the audio before
modulation and to expand it following demodulation.
b. an acronym for amplitude compandored singlesideband.
c. a new method of allowing narrow band voice
communications with the performance of FM systems
for the land-mobile communication industry.
d. all of the above.
Problem 41
The signal processor that increases all negative dBm
power levels and at the same time decreases all
positive dBm power levels is:
a. a signal expander.
b. a linear amplifier.
c. a signal compressor.
d. a phase-locked loop.
Problem 42
The signal processor that decreases all negative
dBm power levels and at the same time
increases all positive dBm power levels is:
a. a signal expander.
b. a linear amplifier.
c. a signal compressor.
d. a phase-locked loop.
Problem 43
Why is the carrier signal needed in an SSB receiver?
a. It is needed for the receiver to maintain its
sensitivity and selectivity.
b. It is needed for the demodulator to be able to
recreate the intelligence.
c. The carrier actually contains the intelligence
signal.
d. Without a carrier, the signal strength of the
received station is zero.
Problem 44
The standard SSB demodulator consists of:
a. an RF amplifier, nonlinear mixer, and IF
amplifier stage.
b. a nonlinear diode and a low-pass filter.
c. a sharp bandpass filter and an audio amplifier
stage.
d. a beat frequency oscillator, nonlinear mixer,
and low-pass filter.
Problem 45
In an SSB receiver, if the BFO drifts slightly off of
the carrier frequency:
a. the output intelligence is badly distorted.
b. the output intelligence amplitude is reduced.
c. the noise level increases.
d. harmonics are produced by mixing action of
the nonlinear device.
Problem 46
In Figure 4-4, the purpose of stage (b) is:
a. to demodulate the 20 MHz USB signal.
b. to create a 1 MHz SSB IF signal.
c. to recreate the 100 Hz to 3 kHz intelligence
signal.
d. to act as a product detector.
Problem 47
In Figure 4-4, what stages have tracking capacitors?
a. stages d and f
b. stages d and e
c. stages b and e
d. stages a and c
Problem 48
In Figure 4-4, what frequency must the BFO be set
at for optimum results?
a. 455 kHz
b. 20 MHz
c. 1 MHz
d. 21 MHz
Problem 49
In Figure 4-4, most of the selectivity and sensitivity
are furnished by:
a. stage a.
b. stage b.
c. stage e.
d. stage d.
Problem 50
In Figure 4-4, the SSB demodulation is
accomplished by:
a. stages b and c.
b. stages d and f.
c. stages d and e.
d. stages e and f.
Problem 51
In which stages of Figure 4-4 should an AGC control
signal be applied?
a. stages a and d
b. stages b and e
c. stages c and f
d. stages e and g
Problem 52
In Figure 4-5, transistor Q1 functions:
a. to recreate the original intelligence signal from
the original SSB signal.
b. as a product detector.
c. to mix the VFO output signal with the received RF
signal in order to produce a 453.55 kHz IF signal.
d. as an RF amplifier stage of the received SSB
signal.
Problem 53
In Figure 4-5, transistor Q2 acts as:
a. an IF amplifier stage.
b. a beat frequency oscillator.
c. a variable frequency oscillator.
d. a mixer stage.
Problem 54
In Figure 4-5, transistor Q3 acts as:
a. an IF amplifier stage.
b. a beat frequency oscillator.
c. a variable frequency oscillator.
d. a mixer stage.
Problem 55
In Figure 4-5, transistor Q4 functions as:
a. a product detector.
b. an RF mixer to create the IF frequency.
c. a variable frequency oscillator.
d. a beat frequency oscillator.
Problem 56
In Figure 4-5, transistor Q5 functions as:
a. a product detector.
b. an RF mixer to create the IF frequency.
c. a variable frequency oscillator.
d. a beat frequency oscillator.
Problem 57
In Figure 4-5, the purpose of switches S1A and S1B
is to:
a. ensure that the USB or LSB mixer output signal
remains in the middle of the IF bandwidth filter.
b. alter the BFO frequency slightly by selecting
separate crystals.
c. alter the VFO frequency slightly by adding bias to
the switching diode, D2.
d. all of the above.
Problem 58
The image shown in figure 4-6
is an example of:
a. double sideband output
spectrum
b. DSB-SC
c. Upper sideband with a
suppressed lower sideband
d. Lower sideband with a
suppressed upper sideband
e. SSB-FC