WorksheetsDIGICOMMS 1-50
Total questions: 50
Worksheet time: 25mins
Name
Class
Date
1.
Instead of a single bit, a QPSK symbol contains:
a)
a byte
b)
4 bits
c)
a dibit
d)
a Q-bit
2.
In FSK, which frequency is always lesser in value?
a)
mark frequency
b)
space frequency
c)
either mark or space frequency
d)
mark and space frequency are equal
3.
For QAM, a “constellation diagram” shows:
a)
location of symbols in symbol space
b)
separation of symbols in symbol space
c)
effects of noise on symbols
d)
all of the above
4.
What is the unit of bandwidth efficiency?
a)
bits per second
b)
bits per cycle
c)
bps per cycle
d)
bps per second
5.
Pulse code modulation is preferred to PAM because of its:
a)
resistance to quantizing error
b)
simplicity
c)
lower cost
d)
superior noise immunity
6.
For QAM, the two dimensions of its symbol space are:
a)
amplitude and frequency
b)
amplitude and phase angle
c)
frequency and phase angle
d)
I-bits and Q-bits
7.
Which of the following uses input bits called quadbit?
a)
BPSK
b)
QPSK
c)
8PSK
d)
16PSK
8.
The number of amplitude, frequency, or phase changes per second is known as:
a)
data rate
b)
frequency of operation
c)
speed limit
d)
baud rate
9.
What is the solution for granular noise in Delta Modulation PCM?
a)
increase the step size
b)
decrease the step size
c)
increase the input signal
d)
decrease the input signal
10.
When calculating the maximum number of users, a limiting factor in FDM is:
a)
type of media
b)
length of channel
c)
bandwidth of each signal
d)
all of the above
11.
As the bit rate of an FSK signal decreases, the bandwidth:
a)
decreases
b)
increases
c)
remains the same
d)
doubles
12.
Which of the following is correct?
a)
the bit rate may be greater than the baud rate
b)
the baud rate may be greater than the bit rate
c)
the bit and baud rates are always the same
d)
the bit and baud rates are not related
13.
For FSK, as the difference between the two carrier frequencies increases, the bandwidth:
a)
decreases
b)
increases
c)
remains the same
d)
halves
14.
Which of the following is equivalent to baud?
a)
bits per second
b)
samples per second
c)
symbols per second
d)
all of these
15.
Which of the following is not a typical FDM application?
a)
telemetry
b)
stereo broadcasting
c)
telephone
d)
secure communications
16.
In order to reduce quantization error, the number of quantization levels must be:
a)
increased
b)
decreased
c)
increased by 50%
d)
decreased by 50%
17.
In trellis coding, the number of data bits is ____ the number of transmitted bits.
a)
equal to
b)
less than
c)
more than
d)
double that of
18.
Framing bits in DS-1 are used to:
a)
detect errors
b)
carry signaling
c)
synchronize the transmitter and receiver
d)
all of the above
19.
The circuit that performs demultiplexing in an FDM system is a(n):
a)
op amp
b)
bandpass filter
c)
discriminator
d)
subcarrier oscillator
20.
In Delta Modulation PCM, granular noise occurs when:
a)
the input does not change
b)
the input changes very fast
c)
the amplitude changes during sample pulse time
d)
the sample exceeds the highest quantization interval
21.
What is the object of trellis coding?
a)
to narrow the bandwidth
b)
to simplify modulation
c)
to increase the data rate
d)
to reduce the error rate
22.
If the number of possible states per symbol is increased, the information capacity:
a)
increases
b)
decreases
c)
increases by 50%
d)
decreases by 50%
23.
Most FDM telemetry systems use:
a)
AM
b)
FM
c)
SSB
d)
PSK
24.
The biggest disadvantage of PCM is:
a)
inability to handle analog signals
b)
high error rate due to quantization
c)
incompatibility with TDM
d)
large bandwidth required
25.
The bit rate always equals the baud rate in which type of signal?
a)
FSK
b)
QAM
c)
4-PSK
d)
all of the above
26.
To accurately reproduce a modulating signal, minimum samples per cycle:
a)
one
b)
two
c)
three
d)
four
27.
The best frequency demodulator is the:
a)
PLL discriminator
b)
pulse-averaging discriminator
c)
Foster-Seeley discriminator
d)
ratio detector
28.
In digital transmission, follower distortion is produced when:
a)
amplitude changes during sample pulse time
b)
Nyquist criterion is not met
c)
rounding off values
d)
sample exceeds highest quantization interval
29.
A modulator converts a(n) ____ signal to a(n) ____ signal.
a)
digital; analog
b)
analog; digital
c)
PSK; FSK
d)
FSK; PSK
30.
In digital transmission, signal degradation can be removed using:
a)
an amplifier
b)
a filter
c)
a regenerative repeater
d)
all of the above
31.
Pulse-amplitude modulation signals are multiplexed by using:
a)
subcarriers
b)
bandpass filters
c)
A/D converters
d)
FET switches
32.
In TDM, for n signal sources, each frame contains ____ slots.
a)
n
b)
n + 1
c)
n − 1
d)
0 to n
33.
Natural sampling does not use:
a)
a sample-and-hold circuit
b)
true binary numbers
c)
a fixed sample rate
d)
an A/D converter
34.
In PAM demultiplexing, the receiver clock is derived from:
a)
WWV
b)
internal oscillator
c)
the PAM signal itself
d)
the 60-Hz power line
35.
Quantization noise is produced when:
a)
amplitude changes during sample pulse
b)
Nyquist criterion is not met
c)
rounding off values
d)
sample exceeds quantization interval
36.
In TDM, the transmission rate is usually ____ the sum of source rates.
a)
greater than
b)
less than
c)
equal to
d)
one less than
37.
In DS-1, bits are “robbed” to:
a)
provide synchronization
b)
carry signaling
c)
cancel echoes
d)
check for errors
38.
AT&T FDM hierarchy bandwidth is found by multiplying:
a)
number of voice channels by 4000 Hz
b)
sampling rate by 4000 Hz
c)
channels by 8 bits/sample
d)
sampling rate by 8 bits/sample
39.
Bit-stuffing is formally called:
a)
compensation
b)
rectification
c)
justification
d)
frame alignment
40.
In PSK, as M decreases, the signal spacing:
a)
increases
b)
decreases
c)
increases by 50%
d)
decreases by 50%
41.
DS-1 through DS-4 are ____ while T-1 through T-4 are ____.
a)
services; multiplexers
b)
services; signals
c)
services; lines
d)
multiplexers; signals
42.
In C = 2B log₂M, M is the:
a)
noise margin
b)
modulation index
c)
number of possible states per symbol
d)
maximum symbols per second
43.
Bit error rate is best described as:
a)
theoretical expectation
b)
determined before transmission
c)
empirical record of actual performance
d)
all of the above
44.
A quantizer is a:
a)
multiplexer
b)
demultiplexer
c)
A/D converter
d)
D/A converter
45.
A good eye pattern shows:
a)
the eye maximally open
b)
eye closed
c)
eye half open
d)
eye alternately opens and closes
46.
Emphasizing low-level signals is called:
a)
quantizing
b)
companding
c)
pre-emphasis
d)
sampling
47.
Guard bands increase bandwidth for:
a)
FDM
b)
TDM
c)
both A and B
d)
none
48.
Eye pattern shows the effect of:
a)
too many highs
b)
too many lows
c)
intermodulation distortion
d)
intersymbol interference
49.
Not a benefit of companding:
a)
minimizes noise
b)
minimizes bits
c)
minimizes quantization error
d)
minimizes bandwidth
50.
Slope overload occurs when:
a)
input does not change
b)
input changes very fast
c)
amplitude changes during pulse
d)
sample exceeds quantization interval
100 %
