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Test: Modem Digital Modulation & Detection Techniques - Electronics and Communication Engineering (ECE) MCQ


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10 Questions MCQ Test - Test: Modem Digital Modulation & Detection Techniques

Test: Modem Digital Modulation & Detection Techniques for Electronics and Communication Engineering (ECE) 2024 is part of Electronics and Communication Engineering (ECE) preparation. The Test: Modem Digital Modulation & Detection Techniques questions and answers have been prepared according to the Electronics and Communication Engineering (ECE) exam syllabus.The Test: Modem Digital Modulation & Detection Techniques MCQs are made for Electronics and Communication Engineering (ECE) 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Modem Digital Modulation & Detection Techniques below.
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Test: Modem Digital Modulation & Detection Techniques - Question 1

Assertion (A): Binary phase shift keying (BPSK) is the most efficient of the three digital modulation, i.e., ASK, FSK and PSK.
Reason (R): In BPSK, phase of sinusoidal carrier is changed according to the data bit to be transmitted.

Detailed Solution for Test: Modem Digital Modulation & Detection Techniques - Question 1

BPSK is the most efficient of the three digital modulation, i.e. ASK, FSK and PSK because BPSK is used for high bit rates. Reason is also a true statement but not the correct explanation of assertion.

Test: Modem Digital Modulation & Detection Techniques - Question 2

Which of the following modulation scheme is most affected by noise?

Test: Modem Digital Modulation & Detection Techniques - Question 3

Match List-I with List-ll and select the correct answer using the codes given below the lists:

List-I
A. BPSK
B. AM
C. QPSK
D. ASK 

List-ll
1. A group of two binary bits is represented by one phase state.
2. A binary bit is represented by one phase state.
3. Carrier ON or OFF depending on whether ‘V or ‘0’ is to be transmitted.
4. Detected using envelope detector

Test: Modem Digital Modulation & Detection Techniques - Question 4

The bit rate of a digital communication system is 34 Mbps. The modulation scheme is QPSK. The baud rate of the system is

Detailed Solution for Test: Modem Digital Modulation & Detection Techniques - Question 4

In BPSK, baud rate is half the bit rate due to which there is more effective utilization of the available bandwidth of the transmission channel. Given, bit rate = 34 Mbps

Test: Modem Digital Modulation & Detection Techniques - Question 5

Consider the following statements;
1. BPSK has a bandwidth which is lower than that of a BFSK signal.
2. BPSK yields the maximum value of probability of error compared to ail the three digital modulation techniques i.e. ASK, FSK and PSK.
3. Binary FSK has the highest system complexity.
4. Binary ASK is demodulated using coherent detection while binary FSK and PSK are demodulated using envelope detection

Which of the statements given above are correct?

Detailed Solution for Test: Modem Digital Modulation & Detection Techniques - Question 5
  • Statement-1 is correct.
  • BPSK has the best performance of all the three digital modulation techniques in presence of noise, it yields the minimum value of probability of error compared to ASK, FSK and PSK. Hence, statement-2 is false.
  • Statement-3 is correct since binary FSK has highest system complexity while binary ASK has least system complexity.
  • Binary ASK is demodulated using envelope detection while binary FSK and PSK are demodulated using coherent detection.

Hence, statement-4 is fals

Test: Modem Digital Modulation & Detection Techniques - Question 6

Comparison of MSKand QPSK scheme shows that

Detailed Solution for Test: Modem Digital Modulation & Detection Techniques - Question 6

More energy (or power) is contained in the main lobe of MSK (about 99% of the total energy or power) as compared to the QPSK (about 90% of the total energy or power).

Test: Modem Digital Modulation & Detection Techniques - Question 7

In a digital continuous-time communication system, the bit rate of NRZ data stream is 1 Mbps and carrier frequency of transmission is 100 MHz. What is the bandwidth requirement of the channel in BPSK and QPSK systems respectively?

Detailed Solution for Test: Modem Digital Modulation & Detection Techniques - Question 7

The bit period of NRZ data stream is

In BPSK, each binary bit is a symbol, therefore symbol duration Ts = Tb = 1 μs.
∴ The bandwidth required for BPSK system is

In QPSK, we group two successive bits to form one symbol, therefore symbol duration,

Test: Modem Digital Modulation & Detection Techniques - Question 8

The error probability of QPSK is

Detailed Solution for Test: Modem Digital Modulation & Detection Techniques - Question 8

The error probability of QPSK is same as BPSK.
The bit error probability is determined when the signal interference and Gaussian noise are applied to the input of the QPSK receiver. The interference is approximated by a sum of sine waves with constant amplitudes and uniformly distributed phases.

Test: Modem Digital Modulation & Detection Techniques - Question 9

Bandwidth of BPSK is ___ than that of BFSK.

Detailed Solution for Test: Modem Digital Modulation & Detection Techniques - Question 9

Minimum bandwidth required in BPSK = 2fb.
Minimum bandwidth required in BFSK = 4fb.
Hence, bandwidth of BPSK is lower than that of BFSK.

Test: Modem Digital Modulation & Detection Techniques - Question 10

The error probability of QPSK is

Detailed Solution for Test: Modem Digital Modulation & Detection Techniques - Question 10

The error probability of QPSK is better (or lower) than that of BPSK due to which QPSK is used for very high bit rate data transmission.

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