This set of Digital Communications Multiple Choice Questions & Answers (MCQs) focuses on “Intersymbol interference 1”.
1. The method in which the tail of one pulse smears into adjacent symbol interval is called as
a) Intersymbol interference
b) Interbit interference
c) Interchannel interference
d) None of the mentioned
View Answer
Explanation: Due to the effect of system filtering the received pulse can overlap on one and another. The tail of one pulse smears into the adjacent symbol interval thereby interfering the detection process. This process is called as intersymbol interference.
2. If each pulse of the sequence to be detected is in _____ shape, the pulse can be detected without ISI.
a) Sine
b) Cosine
c) Sinc
d) None of the mentioned
View Answer
Explanation: The sinc shaped pulse is the ideal nyquist pulse. If each pulse in the sequence to be detected is in sinc shape the pulses can be detected without ISI.
3. What is symbol rate packing?
a) Maximum possible symbol transmission rate
b) Maximum possible symbol receiving rate
c) Maximum bandwidth
d) Maximum ISI value allowed
View Answer
Explanation: A system with bandwidth Rs/2 can support a maximum transmission rate of Rs without ISI. Thus for ideal Nyquist filtering the maximum possible symbol transmission rate is called as symbol rate packing and it is equal to 2 symbols/s/Hz.
4. A nyquist pulse is the one which can be represented by _____ shaped pulse multiplied by another time function.
a) Sine
b) Cosine
c) Sinc
d) None of the mentioned
View Answer
Explanation: A nyquist filter is one whose frequency transfer function can be represented by a rectangular function convolved with any real even symmetric frequency function and a nyquist pulse is one whose shape can be represented by sinc function multiplied by another time function.
5. Examples of nyquist filters are
a) Root raised cosine filter
b) Raised cosine filter
c) Root raised & Raised cosine filter
d) None of the mentioned
View Answer
Explanation: The most popular among the class of nyquist filters are raised cosine and root raised cosine filter.
6. The minimum nyquist bandwidth for the rectangular spectrum in raised cosine filter is
a) 2T
b) 1/2T
c) T2
d) 2/T
View Answer
Explanation: For raised cosine spectrum the minimum nyquist bandwidth is equal to 1/2T.
7. Roll off factor is the fraction of
a) Excess bandwidth and absolute bandwidth
b) Excess bandwidth and minimum nyquist bandwidth
c) Absolute bandwidth and minimum nyquist bandwidth
d) None of the mentioned
View Answer
Explanation: The roll off factor is defined by a fraction of excess bandwidth and the minimum nyquist bandwith. It ranges from 0 to 1.
8. Which value of r (roll off factor) is considered as Nyquist minimum bandwidth case?
a) 0
b) 1
c) Infinity
d) None of the mentioned
View Answer
Explanation: For the roll off factor of 0 an ideal rectangular nyquist pulse is obtained. This is called as nyquist minimum bandwidth case.
9. A pulse shaping filter should satisfy two requirements. They are
a) Should be realizable
b) Should have proper roll off factor
c) Should be realizable & have proper roll off factor
d) None of the mentioned
View Answer
Explanation: A pulse shaping filter should provide the desired roll off and should be realizable, that is the impulse response needs to be truncated to a finite length.
10. Examples of double side band signals are
a) ASK
b) PSK
c) ASK & PSK
d) None of the mentioned
View Answer
Explanation: ASK and PSK needs twice the transmission bandwidth of equivalent baseband signals. Thus these are called as double side band signals.
Sanfoundry Global Education & Learning Series – Digital Communications.
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