laboursonline – MCQs, Mock Tests | Electrical measurements Digital Communications MCQs set-10

Turbo code is a

1. Serial concatenation code
2. Parallel concatenation code
3. Block code
4. None of the mentioned

✅ Correct Answer: 2

The minimum nyquist bandwidth needed for baseband transmission of Rs symbols per second is

1. Rs
2. 2Rs
3. Rs/2
4. Rs2

✅ Correct Answer: 3

The capacity relationship is given by

1. C = W log2 ( 1+S/N )
2. C = 2W log2 ( 1+S/N )
3. C = W log2 ( 1-S/N )
4. C = W log10 ( 1+S/N )

✅ Correct Answer: 1

Which parameter is called as Shannon limit?

1. PB/N0
2. EB/N0
3. EBN0
4. None of the mentioned

✅ Correct Answer: 2

Entropy is the measure of

1. Amount of information at the output
2. Amount of information that can be transmitted
3. Number of error bits from total number of bits
4. None of the mentioned

✅ Correct Answer: 1

Equivocation is the

1. Conditional entropy
2. Joint entropy
3. Individual entropy
4. None of the mentioned

✅ Correct Answer: 1

For a error free channel, conditional probability should be

1. Zero
2. One
3. Equal to joint probability
4. Equal to individual probability

✅ Correct Answer: 1

Average effective information is obtained by

1. Subtracting equivocation from entropy
2. Adding equivocation with entropy
3. Ratio of number of error bits by total number of bits
4. None of the mentioned

✅ Correct Answer: 1

Turbo codes are

1. Forward error correction codes
2. Backward error correction codes
3. Error detection codes
4. None of the mentioned

✅ Correct Answer: 1

Components used for generation of turbo codes are

1. Inter leavers
2. Punching pattern
3. Inter leavers & Punching pattern
4. None of the mentioned

✅ Correct Answer: 3

Decoders are connected in series.

1. True
2. False
3.
4.

✅ Correct Answer: 1

The inter leaver connected between the two decoders is used to

1. Remove error bursts
2. Scatter error bursts
3. Add error bursts
4. None of the mentioned

✅ Correct Answer: 2

In soft decision approach what does -127 mean?

1. Certainly one
2. Certainly zero
3. Very likely zero
4. Very likely one

✅ Correct Answer: 2

In soft decision approach 100 means?

1. Certainly one
2. Certainly zero
3. Very likely zero
4. Very likely one

✅ Correct Answer: 4

In soft decision approach 0 represents

1. Certainly one
2. Certainly zero
3. Very likely zero
4. Could be either zero or one

✅ Correct Answer: 4

QPSK is a composite of

1. Two BPSK
2. Three BPSK
3. Two FSK
4. Two M-ary PSK

✅ Correct Answer: 1

The IF transmission bandwidth of MFSK is

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

✅ Correct Answer: 1

The bandwidth efficiency of MFSK is

1. M/log2M
2. log2M/M
3. M/log10M
4. log10M/M

✅ Correct Answer: 2

The bandwidth efficiency increases as M increases.

1. True
2. False
3.
4.

✅ Correct Answer: 2

The bandwidth efficiency of QFSK is _______ that of BFSK.

1. Greater than
2. Less than
3. Equal to
4. None of the mentioned

✅ Correct Answer: 3

Which modulation is the most efficient one?

1. BPSK
2. BFSK
3. QPSK
4. QAM

✅ Correct Answer: 4

The primary communication resource is

1. Transmitted power
2. Received power
3. Efficiency
4. None of the mentioned

✅ Correct Answer: 1

Greater the redundancy lesser is the bandwidth expansion.

1. True
2. False
3.
4.

✅ Correct Answer: 2

Which modulation scheme uses nonlinear transponders?

1. MSK
2. Offset QPSK
3. MSK & Offset QPSK
4. None of the mentioned

✅ Correct Answer: 3

Which modulation requires more bandwidth?

1. QPSK
2. OQPSK
3. BPSK
4. BFSK

✅ Correct Answer: 3

Which modulation has lower side lobe levels?

1. QPSK
2. OQPSK
3. BPSK
4. MSK

✅ Correct Answer: 4

Which modulation is spectrally more efficient?

1. BPSK
2. MSK
3. QPSK
4. OQPSK

✅ Correct Answer: 2

Which modulation spectrum has narrow main lobe?

1. QPSK
2. OQPSK
3. BPSK
4. MSK

✅ Correct Answer: 1

Which technique can be used for bandwidth reduction?

1. BPSK
2. QPSK
3. MPSK
4. MFSK

✅ Correct Answer: 3

QPSK amplitude modulates

1. Sine function
2. Cosine function
3. Sine & Cosine function
4. None of the mentioned

✅ Correct Answer: 3

QAM is a combination of

1. ASK and FSK
2. ASK and PSK
3. PSK and FSK
4. None of the mentioned

✅ Correct Answer: 2

Which refers to the presence of error correction coding scheme?

1. Coded
2. Uncoded
3. Coded & Uncoded
4. None of the mentioned

✅ Correct Answer: 1

The system will be more bandwidth efficient as WTb decreases.

1. True
2. False
3.
4.

✅ Correct Answer: 1

In MPSK, R/W

1. Increases with increase in M
2. Increases with decrease in M
3. Decreases with increase in M
4. Is not dependent on M

✅ Correct Answer: 1

In MFSK, R/W

1. Increases with increase in M
2. Increases with decrease in M
3. Decreases with increase in M
4. Is not dependent on M

✅ Correct Answer: 3

Which modulation is selected for power limited system?

1. MPSK
2. MFSK
3. MPSK & MFSK
4. None of the mentioned

✅ Correct Answer: 2

The transmission rate is given as

1. R/log2M
2. log2M/R
3. R/log10M
4. log10M/R

✅ Correct Answer: 1

Code’s redundancy is given as

1. n/k
2. k/n
3. nk
4. None of the mentioned

✅ Correct Answer: 1

For more than two quantization level, _______ is used.

1. Hard decision
2. Soft decision
3. Hard & Soft decision
4. None of the mentioned

✅ Correct Answer: 2

How can the throughput of the system be increased?

1. Increasing EIRP
2. Increasing channel bandwidth
3. Decreasing system losses
4. All of the mentioned

✅ Correct Answer: 4

In which technique spot beam antennas are used to point the radio signals in different directions?

1. Code division
2. Space division
3. Frequency division
4. None of the mentioned

✅ Correct Answer: 2

In polarization division technique ______ polarization is used.

1. Orthogonal
2. Non orthogonal
3. Orthogonal & Non orthogonal
4. None of the mentioned

✅ Correct Answer: 1

Channelization characterized by orthogonal spectra is called as

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

✅ Correct Answer: 2

In double side band spectrum which side-band is called as inverted side-band?

1. LSB
2. USB
3. LSB & USB
4. None of the mentioned

✅ Correct Answer: 1

The mixing and filtering of DSB removes

1. LSB
2. USB
3. LSB & USB
4. None of the mentioned

✅ Correct Answer: 2

The super group is made up of

1. Five groups
2. Sixty channels
3. Five groups & Sixty channels
4. None of the mentioned

✅ Correct Answer: 3

The orbital period of communication satellites is _______ as that of earth’s rotational period.

1. Same
2. Greater
3. Lesser
4. None of the mentioned

✅ Correct Answer: 1

Adding improvement to the signal subset choice by starting with the densest possible lattice for the space is called as

1. Optimum signal constellation boundaries
2. Higher density lattice structures
3. Trellis coded modulation
4. None of the mentioned

✅ Correct Answer: 2

Choosing a closely packed signal subset from any regular lattice or array of candidate points is called as

1. Optimum signal constellation boundaries
2. Higher density lattice structures
3. Trellis coded modulation
4. None of the mentioned

✅ Correct Answer: 1

Trellis coded modulation uses

1. Non binary method
2. Uses redundant bits
3. No expansion of bandwidth
4. All of the mentioned

✅ Correct Answer: 4