1. QPSK is a composite of
A. Two BPSK
B. Three BPSK
C. Two FSK
D. Two M-ary PSK
Answer: A
QPSK is effectively a composite of two BPSK signals transmitted on orthogonal components of the carrier.
2. The IF transmission bandwidth of MFSK is
A. M/T
B. T/M
C. 2M/T
D. M/2
Answer: A
In non-coherent orthogonal MFSK modulation, the IF transmission bandwidth is WIF = M/T.
3. The bandwidth efficiency of MFSK is
A. M/log2M
B. log2M/M
C. M/log10M
D. log10M/M
Answer: B
For non-coherent orthogonal MFSK modulation, the bandwidth efficiency is R/W=log2M/M.
4. The bandwidth efficiency increases as M increases.
A. True
B. False
Answer: B
The bandwidth efficiency decreases as M increases.
5. The bandwidth efficiency of QFSK is _______ that of BFSK.
A. Greater than
B. Less than
C. Equal to
D. None of the mentioned
Answer: C
The bandwidth efficiency of QPSK is equal to that of the BFSK.
6. Which modulation is the most efficient one?
A. BPSK
B. BFSK
C. QPSK
D. QAM
Answer: D
Of all the modulation shown, QAM is the most bandwidth-efficient one.
7. The primary communication resource is
A. Transmitted power
B. Received power
C. Efficiency
D. None of the mentioned
Answer: A
The primary communication resources are transmitted power and channel bandwidth.
8. Greater the redundancy lesser is the bandwidth expansion.
A. True
B. False
Answer: B
Within the same block size, the code with greater redundancy requires more bandwidth expansion.
9. Which modulation scheme uses nonlinear transponders?
A. MSK
B. Offset QPSK
C. MSK & Offset QPSK
D. None of the mentioned
Answer: C
Offset QPSK and MSK are two examples of constant envelope modulation schemes that are attractive for systems using non-linear transponders.
10. Which modulation requires more bandwidth?
A. QPSK
B. OQPSK
C. BPSK
D. BFSK
Answer: C
BPSK requires more bandwidth than the other modulation techniques for the given level of spectral density.
