Advanced Communication Systems MCQ

Advanced Communication Systems MCQ

Advanced Communication Systems MCQ, MCQ on Advanced Communication Systems, MCQ on Satellite Communication, MCQ on Mobile Communication, Optical Fiber Communication, Engineering MCQ, Analog Communication MCQ, Advanced Communication Systems MCQ

Pulse Code Modulation (PCM) 

Multiple-Choice Questions on Advanced Communication Systems

Satellite Communication MCQ

Q.1. pick the odd mall out:

• Transponder
• Earth station
• GSM
• Equatorial orbit

Answer: GSM

Q.2. Uplink frequency is ……… downlink frequency in satellite communication.

• greater than
• smaller than
• equal to
• independent of

Answer: greater than

Q.3. In CDMA

• entire bandwidth can be used all the times
• part of the bandwidth can be used all the times
• entire bandwidth can be used on time sharing basis
• none

Answer: entire bandwidth can be used all the times

Q.4. The propagation time from one earth station to another via geo-stationary satellite is approximately

• 300 ms
• 125 ms
• 125 µs
• 25 µs

Answer: 300 ms

Q.5. The figure of merit for a satellite transmitter is

• G/T ratio
• C/N ratio
• EIRP
• none

Answer: G/T ratio

Q.6. The approximate height of the geostationary orbit from the earth’s surface is

• 6,400 km
• 42,200 km
• 3,500 km
• 35,800 km

Answer: 35,800 km

Q.7. The frequency range for satellite communication is

• 1 kHz-100 kHz
• 100 kHz-1 MHz
• 10 MHz-30 MHz
• 1 GHz-30 GHz

Answer: 1 GHz-30 GHz

Q.8. A random satellite moves in

• random paths
• polar orbits
• geostationary orbits
• equatorial plane

Answer: polar orbits

Q.9. Which of the following statements on communication by geosynchronous satellites are correct?

• The propagation loss over each direction (unlink are downlink) is about 200 dB at 5 GHz.
• Radius of the geosynchronous orbit is 42250 km.
• An arc of about 17° must be covered by the satellite antenna in the equatorial plane.
• The polar regions are well covered by the satellite antenna.

Answer: The propagation loss over each direction (unlink are downlink) is about 200 dB at 5 GHz.

Q.10. Which one of the following statements is not correct?

• A geo-synchronous satellite remains practically stationary relative to earth antennas.
• A geo-synchronous satellite means the same thing as a geo-stationary satellite.
• There is a trade-off between the cost of a communication satellite and cost of its earth stations.
• Three geo-synchronous satellites cannot give 100% global coverage.

Answer: There is a trade-off between the cost of a communication satellite and the cost of its earth stations.

Q.11. A geostationary satellite located at about 35000 km from the earth can cover

• Complete surface of the earth
• one hemisphere in one pass
• one side of the earth
• an area depending on antenna used

Answer: one side of the earth

Q.12. Which one of the following is correct?

In satellite communication links, generally

• the uplink carrier frequencies are greater than downlink carrier frequencies
• the uplink carrier frequencies are lesser than downlink carrier frequencies
• both uplink and downlink carrier frequencies are same
• it is not necessary to use carrier at all

Answer: the uplink carrier frequencies are greater than downlink carrier frequencies

Q.13. What was the first commercial geostationary communication satellite?

• INTELSAT-1
• ECHO
• INSAT-1A
• SPUTNIK

Answer: INTELSAT-1

Optical Communication MCQ

Q.14. The order of optical frequencies is

• MHz
• GHz
• kHz
• TeraHz

Answer: TeraHz

Q.15. The angstrom unit for measuring wavelength is equal to

• 10^-10 m
• 10^-10 cm
• 10^-9 m
• 10^-6 m

Answer: 10^-10 m

Q.16. Following is not a usual classification of optical fibre:

• Single-mode step index
• Single-mode graded index
• Multimode step index
• Multimode graded index

Answer: Single-mode graded index

Q.17. The energy gap Eg of a PIN photodetector should be ……. photon energy of light (h_f)

• greater than
• equal to
• smaller than
• independent of

Answer: smaller than

Q.18. The numerical aperture (NA) and acceptance angle θ are related as

• NA = sin θ
• NA = sin^-1 θ
• NA = \sqrt{1-\sin^{2}\theta }
• (d) none

Answer: NA = sin θ

Q.19. The optical fibre uses ……….. portion of the EM spectrum.

• IR
• VHF
• UHF
• HF

Answer: IR

Q.20. For a step-index fibre, the NA across the core

• is variable
• is constant
• may be both
• none

Answer: is constant

Q.21. Population inversion is a property found in

• LED
• photodiode
• FET
• LASER

Answer: LASER

Q.22. Glass fibre has refractive indices n1 of 1.5 and n2 of 1. Assuming c = 3 x 10⁸ m/s, the multipath time dispersion will be

• 2.5 ns/m
• 2.5 µs/m
• 5 ns/m
• 5 µs/m

Answer: 2.5 ns/m

Q.23. Assertion (A): Optical fibres have broader bandwidth compared to conventional copper cables.

Reason (R): The information-carrying capacity of optical fibres is limited by Rayleigh scattering loss.

• Both A and R are true and R is the correct explanation of A.
• Both A and R are true but R is NOT the correct explanation of A.
• A is true but R is false.
• A is false but R is true.

Answer: Both A and R are true but R is NOT the correct explanation of A.

Q.24. Assertion (A): Optical fibres are highly desirable for communication links for lasers.

Reason (R): Active nature of optical fibres provide high spectral purity of the signal.

• Both A and R are true and R is the correct explanation of A.
• Both A and R are true but R is NOT the correct explanation of A.
• A is true but R is false.

Answer: Both A and R are true and R is the correct explanation of A.

Q.25. A certain optical fibre has a refractive index of clad (n1) = 1.40 and that of core (n2) = 1.05. Its numerical aperture will be

• 0.8575
• 0.9260
• 0.3500
• 0.1585 

Answer: 0.9260

Q.26. The normalized frequency of a step-index fibre is 28 at 1300 am wavelength. What is the total number (approximately) of guided modes that can be supported by the fibre?

• 50
• 200
• 400
• 800

Answer: 400

Q.27. The refractive index of glass is 1.5. Find the wavelength of a beam of light with the frequency of 10¹⁴ Hz in a glass. Assume the velocity of light is 3 x 10⁸ m/s in a vacuum.

• 3 µm
• 3 mm
• 2 µm
• 1 µm

Answer: 2 µm

Q.28. Light travels along the optical fibres by which mechanism?

• Refraction
• Reflection
• Scattering
• Total internal reflection

Answer: Total internal reflection

Q.29. Which one of the following is the correct statement?

The graded-index optical fibre cable can be considered to have

• smaller numerical aperture than step-index cable
• several layers of cladding and each layer having a smaller index number relative to its distance from the core
• several layers of cladding and each layer having a higher index number relative to its distance from the core
• large beam spread

Answer: several layers of cladding and each layer having a smaller index number relative to its distance from the core

Q.30. In the design of a single-mode step-index fibre close to upper cut-off, the single-mode operation is NOT preserved if

• radius as well as operating wavelength are halved
• radius as well as operating wavelength are doubled
• radius is halved and operating wavelength is doubled
• radius is doubled and operating wavelength is halved

Answer: radius is doubled and operating wavelength is halved

Q.31. Dispersion in an optical fibre used in a communication link is of which type?

• Angular dispersion
• Modal dispersion
• Chromatic dispersion
• Dispersion arising due to structural irregularities in the fibre

Answer: Modal dispersion

Q.32. Losses in optical fibres can be caused by which of the following?

1. Impurities
2. Microbending
3. Stepped-index operation

Select the correct answer using the codes given below:

• 1 and 3
• 2 and 3
• 1 and 2
• 3 only

Answer: 1 and 2

Q.33. A single-mode fibre does not suffer from which type of dispersion?

• Waveguide dispersion
• Material dispersion
• Intermodal dispersion
• Polarization mode dispersion

Answer: Material dispersion

Mobile Communication MCQ

Q.34. Which one is the second generation mobile communication system?

• AMPS
• IMT-2000
• GSM
• None

Answer: GSM

Q.35. The main objective of CELL in a cellular mobile system is

• frequency re-use
• higher bandwidth
• simple modulation techniques
• hand-off

Answer: frequency re-use

Q.36. A cluster of cells in the collection of adjacent cells with

• same operating spectrum
• different operating spectrum
• combination of same and different operating spectrum  
• None

Answer: different operating spectrum

Q.37. In a GSM system, 8 channels can co-exist in a 200 kHz bandwidth using TDMA. A GSM-based cellular operator is allocated 5 MHz bandwidth. Assuming a frequency reuse factor of 1.5 i.e. a five-cell repeat pattern, the maximum number of simultaneous channels that can exist in one cell is

• 200
• 40
• 25
• 15

Answer: 40