Coherent Detection

Digital Communications Systems

This set of Digital Communications Multiple Choice Questions & Answers (MCQs) focuses on “Coherent detection”.

1. The correlating detector is also known as
a) Maximum likelihood detector
b) Minimum likelihood detector
c) Maximum & Minimum likelihood detector
d) None of the mentioned

2. The minimum nyquist sampling rate is given as, fs =
a) 1/T
b) T
c) 2/T
d) 2T

3. Phase-locked loop circuitry is used for
a) Carrier wave recovery
b) Phase estimation
c) Carrier wave recovery & Phase estimation
d) None of the mentioned

4. In differential PSK the date is
a) Encoded differentially
b) Decoded differentially
c) Encoded & Decoded differentially
d) None of the mentioned

5. Envelope detector consists of
a) Rectifier and high pass filter
b) Rectifier and low pass filter
c) Amplifier and low pass filter
d) Amplifier and high pass filter

6. The minimum required spacing is the difference between the
a) Center of the spectral main lobe and first zero crossing
b) First and second zero crossing
c) First and last zero crossing
d) None of the mentioned

7. The minimum tone separation corresponds to
a) T
b) 1/T
c) 2T
d) T/2

8. Matched filter is used for
a) Coherent detection
b) Non coherent detection
c) Coherent & Non coherent detection
d) None of the mentioned

9. In differential encoding the _________ different between two wave forms is measured.
a) Magnitude
b) Frequency
c) Phase
d) Time period

10. The error probability of DPSK is ________ worse than PSK.
a) Twice
b) 3 db
c) Twice (3db)
d) None of the mentioned

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