Communication Systems
Q. In a communication system, if the signal-to-noise ratio (SNR) is 20 dB, what is the linear SNR?
A.
10
B.
20
C.
100
D.
200
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Solution
Linear SNR = 10^(SNR(dB)/10) = 10^(20/10) = 100.
Correct Answer: C — 100
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Q. In a communication system, what does 'multiplexing' refer to?
A.
Combining multiple signals into one
B.
Separating signals
C.
Amplifying signals
D.
Encoding signals
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Solution
Multiplexing refers to combining multiple signals into one for transmission.
Correct Answer: A — Combining multiple signals into one
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Q. In a communication system, what does 'noise' refer to?
A.
The desired signal
B.
Unwanted disturbances that affect the signal
C.
The modulation technique used
D.
The bandwidth of the channel
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Solution
Noise refers to unwanted disturbances that interfere with the desired signal, affecting the quality of communication.
Correct Answer: B — Unwanted disturbances that affect the signal
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Q. In a communication system, what does 'signal-to-noise ratio' (SNR) measure?
A.
The strength of the signal relative to background noise
B.
The total power of the signal
C.
The bandwidth of the communication channel
D.
The efficiency of the modulation technique
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Solution
Signal-to-noise ratio (SNR) measures the strength of the signal relative to the background noise, indicating the quality of the communication.
Correct Answer: A — The strength of the signal relative to background noise
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Q. In a digital communication system, what does the term 'bit rate' refer to?
A.
The number of bits transmitted per second
B.
The number of bits stored in a device
C.
The frequency of the carrier wave
D.
The duration of each bit
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Solution
Bit rate refers to the number of bits transmitted per second in a digital communication system.
Correct Answer: A — The number of bits transmitted per second
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Q. In amplitude modulation (AM), what does the amplitude of the carrier wave represent?
A.
The frequency of the modulating signal
B.
The phase of the modulating signal
C.
The information signal
D.
The power of the carrier wave
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Solution
In AM, the amplitude of the carrier wave varies in accordance with the amplitude of the modulating signal, which carries the information.
Correct Answer: C — The information signal
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Q. In amplitude modulation (AM), what does the carrier wave represent?
A.
The information signal
B.
The frequency of the modulated signal
C.
The average power of the signal
D.
The high-frequency signal that carries the information
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Solution
In AM, the carrier wave is a high-frequency signal that carries the information signal by varying its amplitude.
Correct Answer: D — The high-frequency signal that carries the information
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Q. In digital communication, what does the term 'bit rate' refer to?
A.
The number of bits transmitted per second
B.
The number of bits stored in a device
C.
The number of bits in a signal
D.
The number of bits required for modulation
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Solution
Bit rate is defined as the number of bits transmitted per second in a digital communication system.
Correct Answer: A — The number of bits transmitted per second
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Q. What is the bandwidth of a signal that has a frequency range from 300 Hz to 3 kHz?
A.
2.7 kHz
B.
3.3 kHz
C.
2.4 kHz
D.
3.0 kHz
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Solution
Bandwidth = f_max - f_min = 3000 Hz - 300 Hz = 2700 Hz or 2.7 kHz.
Correct Answer: A — 2.7 kHz
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Q. What is the bandwidth of a signal that occupies a frequency range from 1 kHz to 3 kHz?
A.
1 kHz
B.
2 kHz
C.
3 kHz
D.
4 kHz
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Solution
Bandwidth = f_max - f_min = 3 kHz - 1 kHz = 2 kHz.
Correct Answer: B — 2 kHz
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Q. What is the bandwidth of a signal that occupies a frequency range from 300 Hz to 3 kHz?
A.
2.7 kHz
B.
3.3 kHz
C.
2.4 kHz
D.
3.0 kHz
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Solution
Bandwidth = f_max - f_min = 3000 Hz - 300 Hz = 2700 Hz = 2.7 kHz.
Correct Answer: A — 2.7 kHz
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Q. What is the effect of increasing the bandwidth of a communication channel?
A.
Increased data rate
B.
Decreased data rate
C.
No effect on data rate
D.
Increased noise
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Solution
Increasing the bandwidth allows for a higher data rate.
Correct Answer: A — Increased data rate
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Q. What is the effect of increasing the transmission power in a communication system?
A.
Increased range
B.
Decreased noise
C.
Higher bandwidth
D.
Lower distortion
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Solution
Increasing the transmission power generally increases the range of the communication system.
Correct Answer: A — Increased range
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Q. What is the Nyquist rate for a signal with a maximum frequency of 1 kHz? (2000)
A.
1 kHz
B.
2 kHz
C.
500 Hz
D.
4 kHz
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Solution
Nyquist rate = 2 * f_max = 2 * 1000 Hz = 2000 Hz = 2 kHz.
Correct Answer: B — 2 kHz
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Q. What is the Nyquist rate for a signal with a maximum frequency of 5 kHz?
A.
5 kHz
B.
10 kHz
C.
15 kHz
D.
20 kHz
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Solution
Nyquist rate = 2 * f_max = 2 * 5 kHz = 10 kHz.
Correct Answer: B — 10 kHz
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Q. What is the Nyquist rate in a communication system?
A.
The minimum sampling rate to avoid aliasing
B.
The maximum data rate achievable
C.
The frequency of the carrier wave
D.
The bandwidth of the communication channel
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Solution
The Nyquist rate is the minimum sampling rate required to avoid aliasing, which is twice the highest frequency of the signal.
Correct Answer: A — The minimum sampling rate to avoid aliasing
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Q. What is the Nyquist rate in communication systems?
A.
The minimum sampling rate to avoid aliasing
B.
The maximum frequency of the signal
C.
The bandwidth of the communication channel
D.
The maximum data rate of a channel
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Solution
The Nyquist rate is the minimum sampling rate required to avoid aliasing, which is twice the maximum frequency of the signal.
Correct Answer: A — The minimum sampling rate to avoid aliasing
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Q. What is the Nyquist rate in the context of signal sampling?
A.
The minimum sampling rate to avoid aliasing
B.
The maximum frequency of the signal
C.
The bandwidth of the signal
D.
The average power of the signal
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Solution
The Nyquist rate is defined as twice the maximum frequency of the signal, which is the minimum sampling rate required to avoid aliasing.
Correct Answer: A — The minimum sampling rate to avoid aliasing
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Q. What is the Nyquist rate?
A.
The minimum sampling rate to avoid aliasing
B.
The maximum frequency of a signal
C.
The bandwidth of a communication channel
D.
The rate of data transmission in a channel
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Solution
The Nyquist rate is the minimum sampling rate required to avoid aliasing, which is twice the maximum frequency of the signal.
Correct Answer: A — The minimum sampling rate to avoid aliasing
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Q. What is the primary advantage of using digital signals over analog signals in communication systems?
A.
Higher bandwidth
B.
Less susceptibility to noise
C.
Easier to modulate
D.
Lower power consumption
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Solution
Digital signals are less susceptible to noise, making them more reliable for communication compared to analog signals.
Correct Answer: B — Less susceptibility to noise
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Q. What is the primary function of a modulator in a communication system?
A.
To amplify the signal
B.
To convert the signal into a suitable form for transmission
C.
To demodulate the received signal
D.
To filter out noise
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Solution
A modulator converts the baseband signal into a form suitable for transmission over a communication channel.
Correct Answer: B — To convert the signal into a suitable form for transmission
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Q. What is the primary function of a transponder in satellite communication?
A.
To amplify the signal
B.
To receive and retransmit signals
C.
To modulate the signal
D.
To filter out noise
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Solution
A transponder in satellite communication receives signals from the ground, processes them, and retransmits them back to Earth.
Correct Answer: B — To receive and retransmit signals
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Q. What is the primary function of an antenna in a communication system?
A.
To amplify the signal
B.
To convert electrical signals into electromagnetic waves
C.
To modulate the signal
D.
To demodulate the signal
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Solution
An antenna converts electrical signals into electromagnetic waves for transmission and vice versa for reception.
Correct Answer: B — To convert electrical signals into electromagnetic waves
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Q. What is the primary purpose of a demodulator in a communication system?
A.
To amplify the signal
B.
To convert the signal back to its original form
C.
To filter the noise
D.
To encode the signal
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Solution
A demodulator converts the modulated signal back to its original form.
Correct Answer: B — To convert the signal back to its original form
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Q. What is the primary purpose of a modulator in a communication system?
A.
To amplify the signal
B.
To convert digital signals to analog
C.
To filter noise
D.
To encode information
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Solution
A modulator converts digital signals to analog for transmission.
Correct Answer: B — To convert digital signals to analog
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Q. What is the primary purpose of modulation in communication systems?
A.
To increase the bandwidth of the signal
B.
To reduce noise in the signal
C.
To allow the transmission of signals over long distances
D.
To convert digital signals to analog signals
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Solution
Modulation allows signals to be transmitted over long distances by shifting the frequency of the signal to a higher range, making it suitable for transmission through various media.
Correct Answer: C — To allow the transmission of signals over long distances
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Q. What is the purpose of a demodulator in a communication system?
A.
To encode the signal for transmission
B.
To convert the modulated signal back to its original form
C.
To amplify the received signal
D.
To filter out unwanted frequencies
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Solution
A demodulator's purpose is to convert the modulated signal back to its original baseband form for further processing.
Correct Answer: B — To convert the modulated signal back to its original form
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Q. What is the role of a demodulator in a communication system?
A.
To amplify the received signal
B.
To convert the modulated signal back to its original form
C.
To filter out noise from the signal
D.
To encode the signal for transmission
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Solution
A demodulator's primary function is to convert the modulated signal back to its original form so that the information can be retrieved.
Correct Answer: B — To convert the modulated signal back to its original form
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Q. What is the role of a transponder in satellite communication?
A.
To amplify the received signal
B.
To convert signals from one frequency to another
C.
To modulate the signal for transmission
D.
To demodulate the received signal
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Solution
A transponder receives signals at one frequency, amplifies them, and then converts them to another frequency for transmission back to Earth.
Correct Answer: B — To convert signals from one frequency to another
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Q. Which modulation technique is most commonly used in digital communication systems?
A.
Amplitude Modulation (AM)
B.
Frequency Modulation (FM)
C.
Phase Shift Keying (PSK)
D.
Quadrature Amplitude Modulation (QAM)
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Solution
Quadrature Amplitude Modulation (QAM) is widely used in digital communication systems due to its efficiency in transmitting data.
Correct Answer: D — Quadrature Amplitude Modulation (QAM)
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