Test: Modem Digital Modulation & Detection Techniques
10 Questions MCQ Test | Test: Modem Digital Modulation & Detection Techniques
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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.
Reason (R): In BPSK, phase of sinusoidal carrier is changed according to the data bit to be transmitted.
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.
Which of the following modulation scheme is most affected by noise?
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
A. BPSK
B. AM
C. QPSK
D. ASK
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
The bit rate of a digital communication system is 34 Mbps. The modulation scheme is QPSK. The baud rate of the system is
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
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?
- 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
Comparison of MSKand QPSK scheme shows that
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).
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?
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,
The error probability of QPSK is
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.
Bandwidth of BPSK is ___ than that of BFSK.
Minimum bandwidth required in BPSK = 2fb.
Minimum bandwidth required in BFSK = 4fb.
Hence, bandwidth of BPSK is lower than that of BFSK.
The error probability of QPSK is
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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