Electrical measurements MCQ Quiz Hub

Browse questions and answers for the Digital Communications MCQs set-5 quiz.

Some of the M-ary waveforms are

1. PAM

2. PPM

3. PDM

4. All of the mentioned

✅ Correct Answer: 4

Which method should be implemented for reducing bandwidth?

1. Multilevel codes

2. Multilevel signalling

3. PAM

4. PDM

✅ Correct Answer: 2

In M-ary PPM waveform, modulation is effected by

1. Delaying

2. Advancing

3. Delaying & Advancing

4. None of the mentioned

✅ Correct Answer: 3

For both PPM and PDM _______ is kept constant.

1. Amplitude

2. Time period

3. Frequency

4. Number of levels

✅ Correct Answer: 1

The method in which small amount of controlled ISI is introduced into the data stream rather than trying to eliminate it completely is called as

1. Correlative coding

2. Duobinary signalling

3. Partial response signalling

4. All of the mentioned

✅ Correct Answer: 4

From digital filter we will get the output pulse as the _______ of the current and the previous pulse.

1. Summation

2. Difference

3. Product

4. Ratio

✅ Correct Answer: 1

In duobinary signalling method, for M-ary transmission, the number of output obtained is

1. 2M

2. 2M+1

3. 2M-1

4. M2

✅ Correct Answer: 3

The method using which the error propagation in dubinary signalling can be avoided is

1. Filtering

2. Precoding

3. Postcoding

4. None of the mentioned

✅ Correct Answer: 2

In precoding technique, the binary sequence is _____ with the previous precoded bit.

1. And-ed

2. Or-ed

3. EXOR-ed

4. Added

✅ Correct Answer: 3

The duobinary filter, He (f) is called as

1. Sine filter

2. Cosine filter

3. Raised cosine filter

4. None of the mentioned

✅ Correct Answer: 2

The method which has greater bandwidth efficiency is called as

1. Duobinary signalling

2. Polybinary signalling

3. Correlative coding

4. All of the mentioned

✅ Correct Answer: 2

In polybinary signalling method the present bit of binary sequence is algebraically added with ______ number of previous bits.

1. j

2. 2j

3. j+2

4. j-2

✅ Correct Answer: 4

The primary advantage of this method is

1. redistribution of spectral density

2. to favor low frequencies

3. redistribution of spectral density & to favor low frequencies

4. none of the mentioned

✅ Correct Answer: 3

Source encoding procedure does

1. Sampling

2. Quantization

3. Compression

4. All of the mentioned

✅ Correct Answer: 4

Which signals are function of time?

1. Random signal

2. Deterministic signal

3. Random & Deterministic signal

4. None of the mentioned

✅ Correct Answer: 2

Auto-correlation function is a

1. Even function

2. Odd function

3. Even & Odd function

4. None of the mentioned

✅ Correct Answer: 1

Shot noise occurs in

1. Transistors

2. Valves

3. Transistors & Valves

4. None of the mentioned

✅ Correct Answer: 3

Source coding reduces

1. Redundancy

2. Average bit rate

3. Redundancy & Average bit rate

4. None of the mentioned

✅ Correct Answer: 3

Delay element in delta modulation acts as

1. First order predictor

2. Second order predictor

3. Third order predictor

4. Fourth order predictor

✅ Correct Answer: 1

Non uniform quantization includes

1. Compression

2. Expansion

3. Compression & Expansion

4. None of the mentioned

✅ Correct Answer: 3

The quantization will be finer when

1. Smaller the number of discrete amplitudes

2. Larger the number of discrete amplitudes

3. Does not depend on amplitudes

4. None of the mentioned

✅ Correct Answer: 2

Different cases of sampling include

1. Ideal impulse sampling

2. Flat-topped sampling

3. Sampling with rectangular pulses

4. All of the mentioned

✅ Correct Answer: 4

Transmitted pulse becomes distorted due to

1. Ideal transmission characteristic

2. Non ideal transmission characteristic

3. All of the mentioned

4. None of the mentioned

✅ Correct Answer: 2

In which mixing is easier?

1. Analog signal

2. Digital signal

3. Analog & Digital signal

4. None of the mentioned

✅ Correct Answer: 2

Which filter does not have sharp output?

1. Linear phase filter

2. Delayed symmetric filter

3. Linear phase & Delayed symmetric filter

4. None of the mentioned

✅ Correct Answer: 3

Using ARMA filter

1. Sampling can be done in real time

2. Gives sharp output

3. All of the mentioned

4. None of the mentioned

✅ Correct Answer: 2

To avoid aliasing

1. Reduce the bandwidth

2. Cut out high frequency

3. Reduce the bandwidth & Cut out high frequency

4. None of the mentioned

✅ Correct Answer: 3

Which requires interpolation filtering?

1. Up-sampler

2. D to A converter

3. Up-sampler & D to A converter

4. None of the mentioned

✅ Correct Answer: 3

A to D conversion process uses

1. Sampler

2. Quantizer

3. Sampler & Quantizer

4. None of the mentioned

✅ Correct Answer: 3

Reconstruction filter is difficult to implement in hardware.

1. True

2. False

3.

4.

✅ Correct Answer: 2

Which process requires low pass filter?

1. Up-sampling

2. Down-sampling

3. Up-sampling & Down-sampling

4. None of the mentioned

✅ Correct Answer: 3

Decreasing the data rate is called as

1. Aliasing

2. Down sampling

3. Up sampling

4. None of the mentioned

✅ Correct Answer: 2

Original signal came to be retraced from sampled version using

1. Low pass filtering

2. High pass filtering

3. Low & High pass filtering

4. None of the mentioned

✅ Correct Answer: 1

The signal can be reconstructed

1. At Nyquist rate

2. Above Nyquist rate

3. At & above the Nyquist rate

4. None of the mentioned

✅ Correct Answer: 3

Which device is needed for the reconstruction of signal?

1. Low pass filter

2. Equalizer

3. Low pass filter & Equalizer

4. None of the mentioned

✅ Correct Answer: 3

The term heterodyning refers to

1. Frequency conversion

2. Frequency mixing

3. Frequency conversion & mixing

4. None of the mentioned

✅ Correct Answer: 3

The causes for error performance degradation in communication systems are

1. Interference

2. Electrical noise

3. Effect of filtering

4. All of the mentioned

✅ Correct Answer: 4

Thermal noise in the communication system due to thermal electrons

1. Can be eliminated

2. Cannot be eliminated

3. Can be avoided upto some extent

4. None of the mentioned

✅ Correct Answer: 2

White noise has _______ power spectral density.

1. Constant

2. Variable

3. Constant & Variable

4. None of the mentioned

✅ Correct Answer: 1

Which are called as hard decisions?

1. Estimates of message symbol with error correcting codes

2. Estimates of message symbol without error correcting codes

3. All of the mentioned

4. None of the mentioned

✅ Correct Answer: 2

The filter which is used to recover the pulse with less ISI is called as

1. Matched filter

2. Correlator

3. Matched filter & Correlator

4. None of the mentioned

✅ Correct Answer: 2

The composite equalizing filter is the combination of

1. Receiving and equalizing filter

2. Transmitting and equalizing filter

3. Amplifier and equalizing filter

4. None of the mentioned

✅ Correct Answer: 1

The sample from the demodulation process consists of sample which is _______ to energy of the received symbol and _____ to noise.

1. Directly and inversely proportional

2. Inversely and directly proportional

3. Both directly proportional

4. Both inversely proportional

✅ Correct Answer: 1

The average noise power of white noise is

1. 0

2. Infinity

3. 1

4. None of the mentioned

✅ Correct Answer: 2

The channel may be affected by

1. Thermal noise

2. Interference from other signals

3. Thermal noise & Interference from other signals

4. None of the mentioned

✅ Correct Answer: 3

Channels display multi-path due to

1. Scattering

2. Time delayed reflections

3. Diffraction

4. All of the mentioned

✅ Correct Answer: 4

The method in which the tail of one pulse smears into adjacent symbol interval is called as

1. Intersymbol interference

2. Interbit interference

3. Interchannel interference

4. None of the mentioned

✅ Correct Answer: 1

If each pulse of the sequence to be detected is in _____ shape, the pulse can be detected without ISI.

1. Sine

2. Cosine

3. Sinc

4. None of the mentioned

✅ Correct Answer: 3

What is symbol rate packing?

1. Maximum possible symbol transmission rate

2. Maximum possible symbol receiving rate

3. Maximum bandwidth

4. Maximum ISI value allowed

✅ Correct Answer: 1

A nyquist pulse is the one which can be represented by _____ shaped pulse multiplied by another time function.

1. Sine

2. Cosine

3. Sinc

4. None of the mentioned

✅ Correct Answer: 3