R4RIN – MCQs, Mock Tests | Electrical measurements Digital Communications MCQs set-6

Which value of r (roll off factor) is considered as Nyquist minimum bandwidth case?

1. 0
2. 1
3. Infinity
4. None of the mentioned

✅ Correct Answer: 1

A pulse shaping filter should satisfy two requirements. They are

1. Should be realizable
2. Should have proper roll off factor
3. Should be realizable & have proper roll off factor
4. None of the mentioned

✅ Correct Answer: 3

Examples of double side band signals are

1. ASK
2. PSK
3. ASK & PSK
4. None of the mentioned

✅ Correct Answer: 3

Channel’s phase response must be a linear function of

1. Time
2. Frequency
3. Time & Frequency
4. None of the mentioned

✅ Correct Answer: 2

Amplitude distortion occurs when

1. Impulse response is not constant
2. Impulse response is constant
3. Frequency transfer function is constant
4. Frequency transfer function is not constant

✅ Correct Answer: 4

Phase distortion occurs when

1. Phase response is function of frequency
2. Phase response is not a function of frequency
3. All of the mentioned
4. None of the mentioned

✅ Correct Answer: 2

Equalization process includes

1. Maximum likelihood sequence estimation
2. Equalization with filters
3. Maximum likelihood sequence estimation & Equalization with filters
4. None of the mentioned

✅ Correct Answer: 3

The maximum likelihood sequence estimator adjusts _______ according to _____ environment.

1. Receiver, transmitter
2. Transmitter, receiver
3. Receiver, receiver
4. None of the mentioned

✅ Correct Answer: 1

The filters used with the equalizer is of ______ types.

1. Feed forward
2. Feed backward
3. Feed forward and feedback
4. None of the mentioned

✅ Correct Answer: 3

Transversal equalizers are ________ and decision feedback equalizers are ______

1. Feed forward, feed back
2. Feed back, feed forward
3. Feed forward, feed forward
4. Feedback, feedback

✅ Correct Answer: 1

Symbol spaced has ____ sample per symbol and fractionally spaced has ___ samples per symbol.

1. One, many
2. Many, one
3. One, one
4. Many, many

✅ Correct Answer: 1

The _______ of the opening of eye pattern indicates the time over which the sampling for detection might be performed.

1. Length
2. Width
3. X-axis value
4. Y-axis value

✅ Correct Answer: 2

Range of time difference of the zero crossing gives the value of

1. Width
2. Distortion
3. Timing jitter
4. Noise margin

✅ Correct Answer: 3

The range of amplitude difference gives the value of

1. Width
2. Distortion
3. Timing jitter
4. Noise margin

✅ Correct Answer: 2

As the eye opens, ISI _______

1. Increases
2. Decreases
3. Remains the same
4. None of the mentioned

✅ Correct Answer: 2

Pseudo noise signal has _______ and _______ SNR for the same peak transmitted power.

1. Larger, smaller
2. Smaller, larger
3. Larger, larger
4. Smaller, smaller

✅ Correct Answer: 3

The index value n, in transversal filter can be used as.

1. Time offset
2. Filter coefficient identifier
3. Time offset & Filter coefficient identifier
4. None of the mentioned

✅ Correct Answer: 3

The over-determined set of equations can be solved using

1. Zero forcing
2. Minimum mean square error
3. Zero forcing & Minimum mean square error
4. None of the mentioned

✅ Correct Answer: 3

If the filter’s tap weight remains fixed during transmission of data, then the equalization is called as

1. Preset equalization
2. Adaptive equalization
3. Fixed equalization
4. None of the mentioned

✅ Correct Answer: 1

Equalization method which is done by tracking a slowly time varying channel response is

1. Preset equalization
2. Adaptive equalization
3. Variable equalization
4. None of the mentioned

✅ Correct Answer: 2

Preamble is used for

1. Detect start of transmission
2. To set automatic gain control
3. To align internal clocks
4. All of the mentioned

✅ Correct Answer: 4

The disadvantage of preset equalizer is that

1. It doesnot requires initial training pulse
2. Time varying channel degrades the performance of the system
3. All of the mentioned
4. None of the mentioned

✅ Correct Answer: 2

For AWGN, the noise variance is

1. N0
2. N0/2
3. 2N0
4. N0/4

✅ Correct Answer: 2

Performance of BFSK signal is ________ than BPSK.

1. 3db worse
2. 3db better
3. 6db worse
4. 6db better

✅ Correct Answer: 1

A Gaussian distribution into the non linear envelope detector yields

1. Rayleigh distribution
2. Normal distribution
3. Poisson distribution
4. Binary distribution

✅ Correct Answer: 1

The non coherent FSK needs ________ Eb/N0 than coherent FSK.

1. 1db more
2. 1db less
3. 3db more
4. 3db less

✅ Correct Answer: 1

The DPSK needs ________ Eb/N0 than BPSK.

1. 1db more
2. 1db less
3. 3db more
4. 3db less

✅ Correct Answer: 1

Coherent PSK and non coherent orthogonal FSK have a difference of ______ in PB.

1. 1db
2. 3db
3. 4db
4. 6db

✅ Correct Answer: 3

Which is easier to implement and is preferred?

1. Coherent system
2. Non coherent system
3. Coherent & Non coherent system
4. None of the mentioned

✅ Correct Answer: 2

Which is the main system consideration?

1. Probability of error
2. System complexity
3. Random fading channel
4. All of the mentioned

✅ Correct Answer: 4

Wavelength and antenna size are related as

1. λ/2
2. λ/4
3. 2λ
4. 4λ

✅ Correct Answer: 2

The detection method where carrier’s phase is given importance is called as

1. Coherent detection
2. Non coherent detection
3. Coherent detection & Non coherent detection
4. None of the mentioned

✅ Correct Answer: 1

The coherent modulation techniques are

1. PSK
2. FSK
3. ASK
4. All of the mentioned

✅ Correct Answer: 4

The real part of a sinusoid carrier wave is called as

1. Inphase
2. Quadrature
3. Inphase & Quadrature
4. None of the mentioned

✅ Correct Answer: 1

Antipodal signal sets are those vectors that can be illustrated as

1. Two 180 opposing vector
2. Two 90 opposing vector
3. Two 360 opposing vector
4. None of the mentioned

✅ Correct Answer: 1

The FSK signal which has a gentle shift from one frequency level to another is called as

1. Differential PSK
2. Continuous PSK
3. Differential & Continuous PSK
4. None of the mentioned

✅ Correct Answer: 2

Which modulation scheme is also called as on-off keying method?

1. ASK
2. FSK
3. PSK
4. GMSK

✅ Correct Answer: 1

In amplitude phase keying each phase vector is separated by

1. 90
2. 0
3. 45
4. 180

✅ Correct Answer: 3

The transformation of the waveform into a single point in signal space is called as

1. Vector point
2. Predetection point
3. Preamplification point
4. Transformation point

✅ Correct Answer: 2

The correlating detector is also known as

1. Maximum likelihood detector
2. Minimum likelihood detector
3. Maximum & Minimum likelihood detector
4. None of the mentioned

✅ Correct Answer: 1

The minimum nyquist sampling rate is given as, fs =

1. 1/T
2. T
3. 2/T
4. 2T

✅ Correct Answer: 1

Phase-locked loop circuitry is used for

1. Carrier wave recovery
2. Phase estimation
3. Carrier wave recovery & Phase estimation
4. None of the mentioned

✅ Correct Answer: 3

In differential PSK the date is

1. Encoded differentially
2. Decoded differentially
3. Encoded & Decoded differentially
4. None of the mentioned

✅ Correct Answer: 1

Envelope detector consists of

1. Rectifier and high pass filter
2. Rectifier and low pass filter
3. Amplifier and low pass filter
4. Amplifier and high pass filter

✅ Correct Answer: 2

The minimum required spacing is the difference between the

1. Center of the spectral main lobe and first zero crossing
2. First and second zero crossing
3. First and last zero crossing
4. None of the mentioned

✅ Correct Answer: 1

The minimum tone separation corresponds to

1. T
2. 1/T
3. 2T
4. T/2

✅ Correct Answer: 2

Matched filter is used for

1. Coherent detection
2. Non coherent detection
3. Coherent & Non coherent detection
4. None of the mentioned

✅ Correct Answer: 1

In differential encoding the _________ different between two wave forms is measured.

1. Magnitude
2. Frequency
3. Phase
4. Time period

✅ Correct Answer: 3

The error probability of DPSK is ________ worse than PSK.

1. Twice
2. 3 db
3. Twice (3db)
4. None of the mentioned

✅ Correct Answer: 3

The limit which represents the threshold Eb/N0 value below which reliable communication cannot be maintained is called as

1. Probability limit
2. Error limit
3. Shannon limit
4. Communication limit

✅ Correct Answer: 3