snuggleshub.com – MCQs, Mock Tests | Electrical measurements Digital Communications MCQs set-12

Entropy calculation returns

1. Random variable
2. Deterministic number
3. Random number
4. None of the mentioned

✅ Correct Answer: 2

Entropy of N random variables is the _____ of the entropy of individual random variable.

1. Sum
2. Product
3. Sum of squares
4. Average

✅ Correct Answer: 1

Average energy per bit is given by

1. average energy symbol/log2 M
2. average energy symbol * log2 M
3. log2 M/ Average energy symbol
4. none of the mentioned

✅ Correct Answer: 1

Which FSK has no phase discontinuity?

1. Continuous FSK
2. Discrete FSK
3. Uniform FSK
4. None of the mentioned

✅ Correct Answer: 1

FSK reception is

1. Phase Coherent
2. Phase non coherent
3. Phase Coherent & non coherent
4. None of the mentioned

✅ Correct Answer: 3

FSK reception uses

1. Correlation receiver
2. PLL
3. Correlation receiver & PLL
4. None of the mentioned

✅ Correct Answer: 3

In non coherent reception _____ is measured.

1. Phase
2. Energy
3. Power
4. None of the mentioned

✅ Correct Answer: 2

Every frequency has ____ orthogonal functions.

1. One
2. Two
3. Four
4. Six

✅ Correct Answer: 2

If we correlate the received signal with any one of the two orthogonal function, the obtained inner product will be

1. In phase
2. Quadrature
3. Zero
4. Cannot be determined

✅ Correct Answer: 3

If we correlate the received signal with both orthogonal function the inner product will be

1. In phase
2. Quadrature
3. In phase and quadrature
4. Unity

✅ Correct Answer: 3

Simulation is used to determine

1. Bit error rate
2. Symbol error rate
3. Bit error
4. Symbol error

✅ Correct Answer: 1

Matched filter is a _____ technique.

1. Modulation
2. Demodulation
3. Modulation & Demodulation
4. None of the mentioned

✅ Correct Answer: 2

Which is called as on-off keying?

1. Amplitude shift keying
2. Uni-polar PAM
3. Amplitude shift keying & Uni-polar PAM
4. None of the mentioned

✅ Correct Answer: 3

QAM uses ______ as the dimensions.

1. In phase
2. Quadrature
3. In phase & Quadrature
4. None of the mentioned

✅ Correct Answer: 3

Which system uses QAM?

1. Digital microwave relay
2. Dial up modem
3. Digital microwave relay & Dial up modem
4. None of the mentioned

✅ Correct Answer: 3

In phase lock which parameter is synchronized

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

✅ Correct Answer: 3

Coherent modulation requires ____ level of synchronization.

1. One
2. Two
3. Three
4. None of the mentioned

✅ Correct Answer: 3

Non coherent system requires

1. Phase synchronization
2. Frequency synchronization
3. Phase & Frequency synchronization
4. None of the mentioned

✅ Correct Answer: 3

For block codes _____ is necessary.

1. Phase synchronization
2. Frequency synchronization
3. Frame synchronization
4. None of the mentioned

✅ Correct Answer: 3

The synchronization necessary for BPSK is

1. Frequency tracking
2. Bit timing
3. Phase tracking
4. All of the mentioned

✅ Correct Answer: 4

Transmitter synchronization implies

1. One way communication
2. Two way communication
3. One & Two way communication
4. None of the mentioned

✅ Correct Answer: 2

As the synchronization levels increases, cost

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

✅ Correct Answer: 2

Synchronization is used in system which has

1. Non coherent modulation techniques
2. Many users accessing
3. Non coherent modulation techniques & Many users accessing
4. None of the mentioned

✅ Correct Answer: 3

Which method has fast acquisition and can work without return link?

1. Open loop method
2. Closed loop method
3. Open & Closed loop method
4. None of the mentioned

✅ Correct Answer: 1

Which method has two way link?

1. Open loop method
2. Closed loop method
3. Open & Closed loop method
4. None of the mentioned

✅ Correct Answer: 2

Which method requires external authority and is inflexible?

1. Open loop method
2. Closed loop method
3. Open & Closed loop method
4. None of the mentioned

✅ Correct Answer: 1

Which method needs precorrect time?

1. Open loop method
2. Closed loop method
3. Open & Closed loop method
4. None of the mentioned

✅ Correct Answer: 1

In open loop method, the time reference error __________ with respect to time.

1. Increases exponentially
2. Decreases exponentially
3. Increases quadratically
4. Decreases quadratically

✅ Correct Answer: 1

When a terminal is able to utilize the measurements made on the return link it is called as

1. Open loop method
2. Closed loop method
3. Quasi close loop method
4. None of the mentioned

✅ Correct Answer: 3

Which reduces the effective distance between signals in signal space?

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

✅ Correct Answer: 3

The system which has ______ signal to noise ratio can tolerate larger timing error.

1. Large
2. Small
3. Large & Small
4. None of the mentioned

✅ Correct Answer: 1

Phase locked loops consists of

1. Phase detectors
2. Loop filter
3. Voltage controlled oscillator
4. All of the mentioned

✅ Correct Answer: 4

In VCO the output frequency is a linear function of its input

1. Frequency
2. Voltage
3. Time period
4. None of the mentioned

✅ Correct Answer: 2

PLL designs have

1. First order loop
2. Second order loop
3. Higher order loop
4. None of the mentioned

✅ Correct Answer: 2

A cycle slip occurs when the magnitude of the original phase error exceeds

1. Î radians
2. 2Ï€ radians
3. Ï€/2 radians
4. Ï€2 radians

✅ Correct Answer: 2

When phase noise and phase jitter is doubled, the phase variance increases by

1. Two times
2. Four times
3. 0.5 times
4. 8 times

✅ Correct Answer: 2

Acquisition is a ______ operation.

1. Linear
2. Non linear
3. Linear & Non linear
4. None of the mentioned

✅ Correct Answer: 2

To avoid the loop to be driven to lock, the sweep rate should be

1. Smaller
2. Larger
3. It does not depend on it
4. None of the mentioned

✅ Correct Answer: 1

Which method is more accurate?

1. Closed loop synchronizer
2. Open loop synchronizer
3. Closed & Open loop synchronizer
4. None of the mentioned

✅ Correct Answer: 1

What is the function of the edge detector?

1. Differentiation
2. Rectification
3. Differentiation & Rectification
4. None of the mentioned

✅ Correct Answer: 3

Continuous phase modulation has

1. More bandwidth efficiency
2. More smoothness
3. More bandwidth efficiency & smoothness
4. None of the mentioned

✅ Correct Answer: 3

CPM has

1. Narrower bandwidth
2. Wider bandwidth
3. More bandwidth requirement
4. None of the mentioned

✅ Correct Answer: 1

The number of filters in CPM receiver structure is

1. LM
2. ML
3. M/L
4. None of the mentioned

✅ Correct Answer: 2

In which modulation schemes, the spreading of spectrum occurs?

1. Frequency modulation
2. Amplitude modulation
3. Frequency & Amplitude modulation
4. None of the mentioned

✅ Correct Answer: 1

Gaussian noise has _____ power spread _____ over all frequencies.

1. Zero, uniformly
2. Zero, non uniformly
3. Infinite, uniformly
4. Infinite, non uniformly

✅ Correct Answer: 3

Jamming is caused by

1. Multipath
2. Natural phenomena
3. Multipath & Natural phenomena
4. None of the mentioned

✅ Correct Answer: 3

Which system makes the detection difficult for all users other than the intended users?

1. Low probability of intercept
2. Low probability of detection
3. Low probability of intercept & detection
4. None of the mentioned

✅ Correct Answer: 3

The radio meter consists of

1. Low pass filter
2. High pass filter
3. Band pass filter
4. Band reject filter

✅ Correct Answer: 3

Spread spectrum signals are used for

1. Ranging
2. Determination of position
3. Ranging & Determination of position
4. None of the mentioned

✅ Correct Answer: 3

Uncertainty in the delay measurement is _________ to the bandwidth of signal pulse.

1. Directly proportional
2. Inversely proportional
3. Not related
4. None of the mentioned

✅ Correct Answer: 2

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Digital Communications MCQs set-12