ECE 2023 Final Exam by Ahmed Abdallah ^^
Broadcasting Signal Modulation Quiz
Test your knowledge with an engaging quiz on signal modulation, Fourier series, and power analysis in broadcasting systems. Designed for students and enthusiasts alike, this quiz offers a comprehensive examination of concepts crucial to understanding communication signals.
Key topics include:
- Signal modulation techniques
- Fourier series and transform applications
- Power calculations and efficiency measures
In a broadcasting station; the periodic signal g(t)=t² as shown in figure is used as a modulating signal to modulate cosine wave carrier using carrier frequency 1000 rad/sec and peak amplitude of 1 volt. For this signal; choose the best answer
The DC component of this function (average Value) equal to …..
Zero
1/2 voltage
1/3 voltage
Other Value
Exponential Fourier series parameter (Dn) equal to ……..
.632/(n²π²)
2(-1)❿/(n²π²)
Zero
Other Value
The average power delivered to generate this signal is equal to ……
Zero
2 w
1.84 w
Other Value
The dc power is equal to …..
1/3 w
1/2 w
1/4 w
1/9 w
The fundamental power is equal to ……
0.02 w
1.82 w
0.04 w
0.06 w
The 1st harmonic power will be ……..
2.57 mw
2.5664 w
2.5664 * 10² w
2.59 mw
The harmonics occupy ……… % of the total signal power.
7.6%
92.4%
Other value
0%
For the complex form of Fourier series for this signal ;the phase shift will be ……
0 degrees
90 degrees
180 degrees
270 degrees
Using ……. One can get the bandwidth of the signal
Fourier Series
Fourier transform
Modulation
Spectral density
This function has values for:
an, bn
an, ao
bn , ao
Other
For the following function; using Fourier transform with its properties choose the correct answer for the following questions
The best period for Fourier transform analysis will be …
From 0 to 2A
From 0 to A
From -2A to 2A
From –A to A
The number of impulse functions in the 2nd derivative of this function is …..
2
4
11
Other value
The Fourier transform for one period of this function G(w) will be ….
2(1-cos(WA)/(A²W)
2(1-sin(WA)/(AW²)
2(1-cos(WA)/(AW²)
Other value
The DC value (average value) of this function will be …
1/2 voltage
1/3 voltage
1/4 voltage
zero
The fundamental component magnitude will be …
2/(2π²)
2/(π²)
Other value
Zero
The 1st harmonic component magnitude will be …
2/(9π²)
2/(π²)
zero
Other value
The 2nd harmonic component magnitude will be …
2/(π²)
Zero
2/(2π²)
2/(9π²)
The Fourier spectrum for this signal will be …
Continuous
Discrete
Binary
Periodic
The spectrum of this signal will be as magnitude line spectrum but multiplied by factor…
2
2π
1
Other value
The total power for this signal can be calculated from its spectrum or line spectrum using …
Integration
Differentiation
Parseval’s
Fourier
For the following figure for AM(DSB-LC) modulator model; sketch the output waveform (in Time domain) in your Draft Paper and then with help of your sketches choose the correct answer for the following questions
The peak carrier Magnitude (A) will be ….
25 voltages
50 voltages
75 voltages
100 voltages
The peak magnitude of the signal m(t) will be …
25 voltages
50 voltages
75 voltages
100 voltages
The peak magnitude of the modulated output waveform ϕ(t) will be ….
25 voltages
50 voltages
75 voltages
100 voltages
The Modulation index will be …..
1/4
1/3
1/2
1
The signal power will be ….
K²/4
K²/2
K²/8
K²
The signal power will be ….
156.25 w
312.5 w
78.125 w
625 w
The carrier power will be …
A²
A²/2
A²/4
A²/8
The power efficiency will be ….
Ps/(Ps+Pc)
Ps/Pc
Pc/Pt
Other value
The magnitude of additional carrier which must be added to attain the modulation index 10%
175 volts
200 volts
225 volts
250 volts
When the power efficiency decreased by 20%; the new modulation index will be …
1
0.3
0.304
0.296
A given AM (DSB-LC) Broadcasting station develops an unmodulated power output of 100w across 50 ohm resistive load. When a sinusoidal test tone with peak amplitude of 5 volts is applied to the input of the modulator; it’s found that the average power output increased by 50%. Under these conditions try to choose the correct answer from the following: The average Carrier Power will be …
25 w
50 w
75 w
100 w
Carrier Magnitude (A) will be …
100 volts
75 volts
50 volts
25 volts
The input signal power (Ps) will be …
25 w
50 w
75 w
100 w
The average power of the upper side band power will be …
25 w
50 w
75 w
100 w
The Modulation index will be …
1/4
1/2
3/4
1
The peak magnitude of the modulated output waveform ϕ(t) will be ….
50 volts
100 volts
150 volts
200 volts
The Magnitude of the upper side band power will be …
25 volts
50 volts
75 volts
100 volts
The average signal if the amplitude of the modulation sinusoidal is reduced to 2 volts will be …
4 w
8 w
12 w
25 w
The total average power in the output if the amplitude of the modulation sinusoidal is reduced to 2 volts will be …
96 w
100 w
104 w
108 w
The maximum power efficiency for any transmitter using DSB-LC is
1/3
1/2
2/3
1
…..… is Changing in carrier amplitude according to the change in signal in modulation process
AM
FM
PM
All of them
The Modulation can be performed using ………. In fourier transform.
Time Shift
Frequency Shift
Integration
Differentiation
…….. Communication systems can transmit and receive signals but not at the same time
Simplex
Half-duplex
Full-duplex
b and c
Public Switched Telephone Network (PSTN) in considered to be …..
Simplex
Half-duplex
Full-duplex
b and c
…….. Is dividing the time in to two parts to transmit and receive at the same time.
TDD
TDMA
Both a and b
None of them
……… allow many mobile users to share simultaneously a common bandwidth
FDMA
TDMA
CDMA
All of them
…….. Systems provide a larger radio channel capacity than TDMA systems
FDMA
TDMA
CDMA
Modulation
…….. is Dividing the B.W in to two regions to transmit and receive at the same time.
FDD
FDMA
Both a, and b
None of them
……… Means the maximum data rate that can be achieved in a given channel conditions.
Channel capacity
System capacity
Both a, and b
None of them
For long distance transmission; we can use ……
Amplifier
Modulator
Both a, and b
None of them
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