WorksheetsIntroduction to Communication Systems Quiz
Total questions: 54
Worksheet time: 50mins
The theory of radio waves was originated by:
Marconi
Bell
Maxwell
Hertz
The person who sent the first radio signal across the Atlantic ocean was:
Marconi
Bell
Maxwell
Hertz
The transmission of radio waves was first done by:
Marconi
Bell
Maxwell
Hertz
A complete communication system must include:
a transmitter and receiver
a transmitter, a receiver, and a channel
a transmitter, a receiver, and a spectrum analyzer
a multiplexer, a demultiplexer, and a channel
Radians per second is equal to:
2π × f
f ÷ 2π
the phase angle
none of the above
The bandwidth required for a modulated carrier depends on:
the carrier frequency
the signal-to-noise ratio
the signal-plus-noise to noise ratio
the baseband frequency range
When two or more signals share a common channel, it is called:
sub-channeling
signal switching
SINAD
multiplexing
TDM stands for:
Time-Division Multiplexing
Two-level Digital Modulation
Time Domain Measurement
none of the above
FDM stands for:
Fast Digital Modulation
Frequency Domain Measurement
Frequency-Division Multiplexing
none of the above
The wavelength of a radio signal is:
equal to f ÷ c
equal to c ÷ λ
the distance a wave travels in one period
how far the signal can travel without distortion
Distortion is caused by:
creation of harmonics of baseband frequencies
baseband frequencies "mixing" with each other
shift in phase relationships between baseband frequencies
all of the above
The collection of sinusoidal frequencies present in a modulated carrier is called its:
frequency-domain representation
Fourier series
spectrum
all of the above
The baseband bandwidth for a voice-grade (telephone) signal is:
approximately 3 kHz
20 Hz to 15,000 Hz
at least 5 kHz
none of the above
Noise in a communication system originates in:
the sender
the receiver
the channel
all of the above
"Man-made" noise can come from:
equipment that sparks
temperature
static
all of the above
Thermal noise is generated in:
transistors and diodes
resistors
copper wire
all of the above
Shot noise is generated in:
transistors and diodes
resistors
copper wire
none of the above
The power density of "flicker" noise is:
the same at all frequencies
greater at high frequencies
greater at low frequencies
the same as "white" noise
So called "1/f" noise is also called:
random noise
pink noise
white noise
partition noise
"Pink" noise has:
equal power per Hertz
equal power per octave
constant power
none of the above
When two noise voltages, V1 and V2, are combined, the total voltage VT is:
VT = sqrt(V1 × V1 + V2 × V2)
VT = (V1 + V2)/2
VT = sqrt(V1 × V2)
VT = V1 + V2
Signal-to-Noise ratio is calculated as:
signal voltage divided by noise voltage
signal power divided by noise power
first add the signal power to the noise power, then divide by noise power
none of the above
SINAD is calculated as:
signal voltage divided by noise voltage
signal power divided by noise power
first add the signal power to the noise power, then divide by noise power
none of the above
Noise Figure is a measure of:
how much noise is in a communications system
how much noise is in the channel
how much noise an amplifier adds to a signal
signal-to-noise ratio in dB
The part, or parts, of a sinusoidal carrier that can be modulated are:
its amplitude
its amplitude and frequency
its amplitude, frequency, and direction
its amplitude, frequency, and phase angle
The telephone was invented in the year (a) .
Radio signals first were sent across the Atlantic in the year (a) .
The frequency band used to modulate the carrier is called the (a) band.
The job of the carrier is to get the information through the (a) .
The bandwidth of an unmodulated carrier is (a) .
The 'B' in Hartley's Law stands for (a) .
The more information per second you send, the ____________________ the bandwidth required.
greater
larger
wider
In (a) , you split the bandwidth of a channel into sub-channels to carry multiple signals.
In (a) , multiple signal streams take turns using the channel.
VHF stands for the (a) frequency band.
The VHF band starts at (a) MHz.
The UHF band starts at (a) MHz.
A radio signal's (a) is the distance it travels in one cycle of the carrier.
In free space, radio signals travel at approximately (a) meters per second.
The equipment used to show signals in the frequency domain is the _________________________.
Mathematically, a spectrum is represented by a (a) series.
Disabling a receiver during a burst of atmospheric noise is called ____________________.
noise blanking
blanking
For satellite communications, (a) noise can be a serious problem.
Thermal noise is caused by the random motions of (a) in a conductor.
Name the five elements in a block diagram of a communications system.
Source
Transmitter
Channel
Receiver
Destination
Name five types of internal noise.
Thermal
Shot
Partition
1/f
transit-time
Why is thermal noise called "white noise"?
What is "pink noise"?
Suppose there is 30 μV from one noise source that is combined with 40 μV from another noise source. Calculate the total noise voltage.
If you have 100 mV of signal and 10 mV of noise, both across the same 100-ohm load, what is the signal-to-noise ratio in dB?
The input to an amplifier has a signal-to-noise ratio of 100 dB and an output signal-to-noise ratio of 80 dB. Find NF, both in dB and as a ratio.
A microwave receiver has a noise temperature of 145 K. Find its noise figure.
Two cascaded amplifiers each have a noise figure of 5 and a gain of 10. Find the total NF for the pair.
Explain why you could use a diode as a noise source with a spectrum close to that of pure thermal noise. How would you control the amount of noise generated?
