R4RIN – MCQs, Mock Tests | Electrical measurements Digital Communications MCQs set-3

Modulation channel consists of

1. Amplifier
2. Signal processing units
3. Amplifier & Signal processing units
4. None of the mentioned

✅ Correct Answer: 3

Modulation channel does not accept an analog input signal.

1. True
2. False
3.
4.

✅ Correct Answer: 2

If operating frequency bands are higher ______ is available.

1. Smaller bandwidth
2. Larger bandwidth
3. Smaller & Larger bandwidth
4. Cannot be determined

✅ Correct Answer: 2

Ground wave communication occurs in

1. Low frequency band
2. Medium frequency band
3. Low & Medium frequency band
4. None of the mentioned

✅ Correct Answer: 3

Sampling theorem is used for converting

1. Continuous time signal to discrete
2. Discrete to continuous time signal
3. Continuous time signal to discrete & vice versa
4. None of the mentioned

✅ Correct Answer: 3

A signal can be recovered from its sample by using

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

✅ Correct Answer: 1

Which is practically realizable?

1. A train of pulses
2. Impulse train
3. All of the mentioned
4. None of the mentioned

✅ Correct Answer: 1

In flat top sampling scheme, ______ is kept constant after sampling.

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

✅ Correct Answer: 1

Loop filter is a ______ used to reduce noise.

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

✅ Correct Answer: 1

A stationary stochastic process has

1. Finite energy signal
2. Infinite zero signal
3. Zero energy signal
4. None of the mentioned

✅ Correct Answer: 2

The power spectral density function of the stochastic process is

1. Real
2. Odd
3. Real & odd
4. None of the mentioned

✅ Correct Answer: 1

For a periodic function, the spectral density and auto correlation functions form

1. Fourier transform pair
2. Laplace transform pair
3. Hilbert transform pair
4. Z transform pair

✅ Correct Answer: 1

The capacity of a channel is given by

1. Number of digits used in coding
2. Volume of information it can take
3. Maximum rate of information transmitted
4. Bandwidth requires information

✅ Correct Answer: 3

In a communication system, a process in which statistical averages and time averages are equal is called as

1. Stationary
2. Ergodic
3. Gaussian
4. Poisson

✅ Correct Answer: 2

A rectangular pulse of duration T is applied to a matched filter. The output of the filter is a

1. Rectangular pulse of duration T
2. Rectangular pulse of duration 2T
3. Triangular pulse
4. Sine function

✅ Correct Answer: 3

The line code has a zero dc component for pulse transmission of random binary data is

1. NRZ
2. RZ
3. Alternate mark inversion
4. None of the mentioned

✅ Correct Answer: 3

The auto-correlation of white noise is

1. A delta function
2. A constant
3. Gaussian
4. None of the mentioned

✅ Correct Answer: 1

Ionospheric communication can take place in

1. High frequency band
2. Very high frequency band
3. Ultra high frequency band
4. Super high frequency band

✅ Correct Answer: 1

Satellite communication takes place in

1. Ultra high frequency band
2. Super high frequency band
3. Ultra & Super high frequency band
4. None of the mentioned

✅ Correct Answer: 3

The weighing matrix is

1. Positive quantity
2. Inverse of covariance matrix of the input vector
3. Positive quantity & Inverse of a covariance matrix of the input vector
4. None of the mentioned

✅ Correct Answer: 3

Non uniform tree _____ bit rate.

1. Increases
2. Decreases
3. Does not affect
4. None of the mentioned

✅ Correct Answer: 1

Two clock with rates T1 and T2 are incommensurate if its ratio is

1. Rational
2. Irrational
3. Equal
4. None of the mentioned

✅ Correct Answer: 2

Possible timing error detection methods are

1. Early late
2. Zero crossing
3. Early late & Zero crossing
4. None of the mentioned

✅ Correct Answer: 3

Which has minimum power loss during transmission?

1. Twisted Copper cable at 1KHz
2. Optical fiber
3. Twisted copper cable at 100KHz
4. Wave guide

✅ Correct Answer: 1

Voltage generated by lightning is an example for

1. Energy signal
2. Power signal
3. Energy & Power signal
4. None of the mentioned

✅ Correct Answer: 1

In the digital communication system, signals in different frequency bands are

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

✅ Correct Answer: 1

Properties of impulse function are

1. Symmetry
2. Time scaling
3. Shifting
4. All of the mentioned

✅ Correct Answer: 4

Properties of Fourier transform are

1. Duality property
2. Time shifting property
3. Modulation property
4. All of the mentioned

✅ Correct Answer: 4

A base-band signal can be up-converted using

1. Sine wave
2. Cosine wave
3. Filtering
4. None of the mentioned

✅ Correct Answer: 2

A band-pass signal can be down-converted using

1. Sine wave
2. Cosine wave
3. Time delayed wave
4. None of the mentioned

✅ Correct Answer: 2

In down-conversion multiplication with cosine wave is followed by

1. Low pass filter
2. High pass filter
3. Bandpass filter
4. Bandstop filter

✅ Correct Answer: 1

ADSL has _____ information channels.

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

✅ Correct Answer: 2

Fourier transform of a signal gives the

1. Frequency content
2. Bandwidth
3. Frequency content & Bandwidth
4. None of the mentioned

✅ Correct Answer: 3

Random things in a communication system are

1. Timing offset
2. Device frequency
3. Attenuation
4. All of the mentioned

✅ Correct Answer: 4

Which can be used for periodic and non periodic?

1. Fourier series
2. Fourier transforms
3. Fourier series & transforms
4. None of the mentioned

✅ Correct Answer: 2

A band-pass signal has a Fourier transform equal to

1. One
2. Zero
3. Infinity
4. Cannot be determined

✅ Correct Answer: 2

Which are orthonormal signal representation?

1. Sine and cosine at same frequency
2. Wavelets
3. Complex sinusoids at a different frequency
4. All of the mentioned

✅ Correct Answer: 4

Constellation diagram is plotted in

1. Constellation space
2. Signal space
3. Orthogonal space
4. Boundary space

✅ Correct Answer: 2

Cumulative distributive function is

1. Non negative
2. Non decreasing
3. Non negative & decreasing
4. None of the mentioned

✅ Correct Answer: 3

Which are non negative functions?

1. PDF
2. PMF
3. PDF & PMF
4. None of the mentioned

✅ Correct Answer: 3

The sampling process includes methods such as

1. Filtering
2. Sample and hold
3. Amplifying
4. None of the mentioned

✅ Correct Answer: 2

The output of sampling process are called as ________

1. Pulse code modulation
2. Pulse amplitude modulation
3. Frequency modulation
4. Amplitude modulation

✅ Correct Answer: 2

According to Sampling theorem

1. Ts is greater than 1/2fm
2. Ts is lesser than 1/2fm
3. Ts is equal to 1/2fm
4. Ts is lesser than or equal to 1/2fm

✅ Correct Answer: 4

The fourier tranform of one impulse train is also another impulse train with a period of the output equal to the

1. Period of the input
2. Reciprocal of the period of input signal
3. Half the period of input
4. Twice the period of the input

✅ Correct Answer: 2

The process in which the top of each pulse in the output samples retains the shape of the analog segment is called as ________

1. Natural sampling
2. Ideal sampling
3. Aliasing
4. None of the mentioned

✅ Correct Answer: 1

The effects of aliasing are ________

1. Attenuation of high frequency spectral replicates
2. Non uniform spectral gain applied to desired baseband spectrum
3. Attenuation and non uniform spectral gain
4. None of the mentioned

✅ Correct Answer: 3

Aliasing can be removed using

1. Prefiltering
2. Postfiltering
3. Prefiltering & Postfiltering
4. None of the mentioned

✅ Correct Answer: 3

Which process is more economical?

1. Undersampling
2. Oversampling
3. Aliasing
4. None of the mentioned

✅ Correct Answer: 2

Flat top sampling or practical sampling has

1. Same frequency
2. Same amplitude
3. Same time difference
4. None of the mentioned

✅ Correct Answer: 2

Multiplication of input signal with pulse train is done in ________ sampling.

1. Impulse sampling
2. Natural sampling
3. Flat top sampling
4. None of the mentioned

✅ Correct Answer: 2