COMPREHENSIVE REVIEWER IN
17. A waveguide mode in which there is no component of electric field in the direction
of propagation given in the British
European standards.
a. H-mode b. E-mode c. TE mode d. M-mode
18. The extra strength needed in order to assure that enough signal reaches the receiving antenna and must be made available to compensate for fades; computed as the difference between the received signal strength and the threshold level
a. Fade Margin b. Threshold Level c. Noise Figure d. RSL
19. The use of redundant system to reduce the effects of multipath fading is
a. Combining b. Modulation c. Multiplexing d. Diversity
20. A profile graph of the microwave energy path
a. Shows the cross section of the earth’s surface
b. Determines LOS or site technical feasibility
c. Determines the actual clearance, antenna heights and system reliability d. All of the preceding
21. In locating microwave relay stations, the systems designer must consider
a. Terrain obstructions and reflection points
b. Site security and navigational hazards c. Availability of power, water source and
accessible roads d. All of the above
22. A microwave path over which radio waves
barely touches the obstruction is called a. Line of Sight
b. Obstructed Path c. Grazing Path d. Crooked Path
23. What is the function of regenerative repeater?
a. To eliminate bias distortion
b. To help in the loading of the telegraphs lines
c. To reduce required signal levels
d. To reshape the pulses after they have become distorted
24. A situation when there is no change in attenuation or “no gain, no loss” occurs when ________ % of the first Fresnel radius clears a path obstruction in microwave systems.
a. 45%
b. 60%
c. 75%
d. 85%
25. ____________ are concentric circular zones about a direct path of a microwave signal called Huygen’s radiation center, forming an imaginary solid called an ellipsoid __________.
a. Temperature zone b. Skip zone
c. Fresnel zone d. Fraunhoffer zone
26. Waveguides are used mainly for microwave transmission because
a. They depend on straight line propagation
b. Losses are heavy at lower frequencies c. They are bulky at lower frequencies d. No generator is powerful enough to
excite them
27. A waveguide assembly that lets the radar transmitter and receiver share an antenna is called
a. Translator b. Diplexer c. Flip-flop d. duplexer
28. ________________ is a graph wherein the terrain in which the microwave beam should traverse.
a. Topograph
b. Radio path profile c. Fresnel graph
d. Net path graph
29. The Fresnel zone is the circular zone about the _______ path.
a. Reflected b. Direct c. LOS d. Refracted
30. The radius in the circular zone is in the first Fresnel zone when the reflected path is _______ longer than the direct path.
a. λ/2 b. λ c. λ/4 d. λ/8
31. At __________ of the first Fresnel zone is a condition where there is no gain and no loss.
a. 0.5 b. 0.6 c. 0.7 d. 0.8
32. The weakest signal the receiver could accept to be considered satisfactory.
a. Threshold b. Fade margin c. RSL
d. NPL
33. The frequency band from 8 to 12 GHz is known as the band.
a. C b. Ku c. X d. Ka
34. The difference between the Received Signal Level and the FM Improvement Threshold
a. System Gain b. Noise Threshold c. Fade Margin d. Reliability
35. A Fade Margin of 28 dB has a reliability of a. 99%
b. 99.9%
c. 99.99%
d. 99.999%
36. Topographical maps are used for
microwave communications systems design because _________ are shown, thereby elevations are known.
a. Latitudes b. Longitudes c. Contour lines
d. Scales
37. The dominant mode in a rectangular waveguide.
a. TEM b. TE1,1 c. TE1,0 d. TM1,1
38. The velocity of a resultant wave as it travels through the waveguide.
a. Speed of light b. Group velocity c. Phase velocity d. Incident velocity
39. The principal mode for a circular waveguide.
a. TE1,0 b. TM2,0 c. TE1,1 d. TEM
40. A type of waveguide that reduces the cutoff wavelength, increases bandwidth and allows for a variation of the characteristics impedance.
a. Ridge b. Rectangular c. Tee
d. Twisted
41. The subscript which indicates the number of λ/2’ s along the waveguide height.
a. m b. n c. a d. b
42. The international equivalent of the TE mode
a. H b. E c. Z d. TEM
43. The smallest free space wavelength that is just unable to propagate in the waveguide under given conditions.
a. Guide b. Phase c. Cut-off d. Group
44. The characteristic wave impedance of a waveguide in the TE mode is _______ that of the TM mode.
a. Equal to b. Higher than c. Lower than
d. NOTA
45. The following are methods of exciting waveguides except
a. Slot coupling b. Antennas c. Flanges
d. Direct coupling
46. Higher order mode-waveguides are not used in practice because they have ______
cut-off frequencies.
a. Low b. High
c. Indeterminate d. Fixed
47. Indicate which of the following cannot be followed by the word “waveguide”
a. Elliptical b. Flexible c. Coaxial d. Ridged
48. A piston attenuator is a a. Vane attenuator
b. Waveguide below cut-off c. Mode filter
d. Flap attenuator
49. Which of the following waveguide tuning components is not easily adjustable?
a. Screw b. Stub c. Iris d. Plunger
50. Which of the following is not a waveguide termination component?
a. Tapered pyramid b. Post
c. Tapered resistance card d. Stepped resistance card
51. What microwave component can sample part of the power travelling through the waveguide?
a. Directional coupler b. Magic tee
c. Circulator
d. Re-entrant cavity
52. The following are gases used for LASER’s except
a. Helium b. Neon c. Argon d. ruby
53. Also known as the optical maser a. Ruby maser
b. LASER
c. Quantum mechanics d. GaAs maser
54. Paramagnetic means _____________
magnetic a. Almost b. Fully c. Slightly d. Electro
55. Tuning the ruby maser is done by adjusting the _________ to alter the energy level of the ferrous chromium.
a. Electric field b. Magnetic field c. Pumping of electrons d. Electromagnetic field
56. To overcome the very narrow bandwidth in ruby maser, _______ is used.
a. Magnetron b. TWT
c. IMPATT diode d. Gunn diode
57. The following are applications of masers except
a. Radioastronomy b. Radiotelescope c. Radar
d. ET communications
58. A parametric amplifier is a device which amplifies signal by varying the
a. Resistance b. Reactance c. Magnetic field d. Electric field
59. The following are parts of the parametric amplifier except
a. Idling circuit b. Pump circuit c. Tuned circuit d. Filter circuit
60. The number of cavities in a magnetron used in practice.
a. 4 b. 6 c. 8 d. 10
61. Changing the anode voltage to change the velocity of the electrons in a magnetron tube
a. Frequency pushing b. Frequency pulling c. Strapping
d. Pumping
62. The lowest frequency that will propagate through the waveguide while operating in a particular mode.
a. Critical frequency b. Cut-off frequency c. MUF
d. UHF
63. The mode of a waveguide where there is no component of magnetic field in the
direction of propagation a. TE
b. TM c. H d. TEM
64. The following are slow wave structures used to retard the RF field in a TWT except a. Helix
b. Attenuator
c. Waveguide coupled cavity d. NOTA
65. A rectangular waveguide is 5.1 cm by 2.4 cm. The cut-off frequency for the dominant mode is
a. 2.94 GHz b. 6.25 GHz c. 664 MHz d. 57.7 GHz
66. Calculate the cut-off wavelength, the guide wavelength and the characteristic
impedance of a circular waveguide whose internal diameter is 4 cm for a 10 GHz signal propagated in it in the dominant mode. (kr=1.84)
a. 6.83 cm, 3 cm, 420ῼ b. 3 cm , 6.83 cm, 420 ῼ c. 6.83 cm, 3.34 cm, 420 ῼ d. 6.83 cm, 3.34 cm, 338 ῼ
67. A wave is propagated in a parallel plane waveguide. The frequency is 6 GHz and the plane separation is 3 cm. The cut-off wavelength for the dominant mode, the group and phase velocities are
a. 5 cm, 166 Mm/sec,543 Mn/sec b. 6 cm, 166 Mm/sec,543 Mn/sec c. 6 cm, 543 Mm/sec,166 Mn/sec d. 5 cm, 543 Mm/sec,166 Mn/sec
68. If the MTBF of a communication circuit is 20,000 hours and its MTTR is 5 hours, what is its unavailability?
a. 0.00025 b. 99.975%
c. 0.25 % d. 00.975%
69. What would be the ERP, in watts if the transmitter output is 30 dBm and the transmission line loss is 20 dB and the antenna connected to it has a power gain of 60 dB?
a. 10,000 watts b. 1000 watts c. 100 watts d. 10 watts
70. Also referred to as the Transferred Electron Device
a. Magnetron b. TWT
c. Gunn diode d. APD
71. Also known as the Esaki diode a. Gunn
b. Tunnel c. IMPATT d. PIN diode
72. The following are negative resistance amplifiers except
a. Tunnel b. Gunn c. IMPATT d. PIN diode
73. Regarded as the oldest semiconductor device
a. Shottky Barrier diode b. PIN diode
c. Point contact diode d. Triode
74. Also called the hot electron diode a. PIN diode
b. ESBAR c. APD d. Gunn diode
75. Also called tunnel rectifiers a. Backward diode b. Schottky barrier diode c. APD
d. PIN diode
76. Varactors are variable __________ diode.
a. Reactance b. Capacitance c. Inductance d. Resistance
77. Diodes designed to store energy in their capacitance during forward bias and generates harmonics in the reverse bias.
a. Step recovery b. Gunn
c. APD d. IMPATT
78. A cross between the TWT and the magnetron in its operation
a. CFA b. BWO c. EIA d. Twystron
79. The following are parts of a multicavity klystron except
a. Buncher cavity b. Catcher cavity c. Cathode d. Attenuator
80. The very first microwave transistors a. GaAs FET
b. Si BJT c. MIC d. NOTA
81. The most common microwave FET which is also known as the MESFET
a. Dual GaAs FET b. Si BJT
c. MIC
d. Schottky Barrier Gate
82. It looks like a shorter, thicker TWT a. CFA
b. BWO c. EIA d. Twystron
83. A Twystron is a hybrid combination of a. TWT and Magnetron
b. TWT and Klystron c. TWT and Ubitron d. TWT and gyrotron
84. A multicavity klystron with interconnected multigap cavities
a. TWT b. Twystron c. EIA d. Gyrotron 85. SAW propagate in
a. GaAs b. InP c. Stripline d. Quartz crystal
86. The output from a laser is monochromatic;
this means that it is a. Infrared
b. Narrow beam
c. Polarized
d. Single frequency
87. The ruby laser differs from the ruby maser in that the former
a. Does not require pumping b. Needs no resonator c. Is an oscillator
d. Produces much lower powers
88. The transmission system using two ground planes
a. Microstrip
b. Elliptical waveguide c. Parallel wire line d. Stripline
89. A BWO is based on the a. Rising sun magnetron b. CFA
c. Coaxial magnetron d. TWT
90. One of the following is unlikely to be used as a pulsed device
a. Multicavity klystron b. BWO
c. CFA d. TWT
91. A microwave tube amplifier uses an axial magnetic field and a radial electric field a. Reflex klystron
b. Coaxial magnetron c. TW magnetron d. CFA
92. The attenuator is used in the TWT to a. Help bunching
b. Prevent oscillation c. Prevent saturation d. Increase gain
93. The glass tube of a TWT may be coated with aquadag to
a. Help focusing
b. Provide attenuation c. Improve bunching d. Increase gain
94. The cavity magnetron uses strapping to a. Prevent mode jumping
b. Prevent cathode back heating c. Ensure bunching
d. Improve the phase focusing effect 95. Compared with equivalent transmission
lines, 3-GHz waveguides (indicate false statement)
a. Are less lossy
b. Can carry higher powers
c. Are less bulky
d. Have lower attenuation
96. Indicate the false statement. When the free-space wavelength of a signal equals the cut-off wavelength of the guide
a. The group velocity of the signal becomes zero
b. The phase velocity of the signal becomes infinite
c. The characteristic impedance of the guide becomes infinite
d. The wavelength within the waveguide becomes infinite
97. A disadvantage of microstrip with respect to stripline circuits is that the former a. Do not lend themselves to
printed-circuit techniques
b. Are more likely to radiate c. Are bulkier
d. Are more expensive and complex to manufacture
98. In order to couple two generators to a waveguide system without coupling them to each other, one could not use a
a. Rat-race b. E-plane T c. Hybrid ring d. Magic T 99. A PIN diode is
a. A metal semiconductor point-contact diode
b. A microwave mixer diode
c. Often used as a microwave detector d. Suitable for use as a microwave
switch
100. For handling high powers, the best transmission medium is
a. Stripline b. Microstrip
c. Rectangular waveguide d. Coaxial line
COMMUNICATIONS ENGINEERING PART 8
SATELLITE COMMUNICATIONS 1. The first duplex satellite is
a. Moon b. Sputnik 1 c. Telstar d. Early Bird
2. The FDMA technique wherein voice band
channels are assigned on “as needed” basis.
a. PAMA b. DAMA c. SSMA d. CDMA
3. A form of CDMA where a digital code is used to continually change the frequency of the carrier.
a. Spread Spectrum b. Frequency Hopping c. Store and Forward d. SPADE
4. The satellite frequency reuse method which sends different information signals using vertical or horizontal electromagnetic polarization.
a. Multiple coverage areas b. Dual polarization c. Spatial separation d. Spread spectrum
5. A satellite communication link between Pinugay Earth Station, Philippines and Mt.
Fucino Earth Station, Italy is to be
established. If the assigneduplink frequency at Pinugay Earth Station is 6175 MHz, what is the downlink frequency at Mt. Fucino Earth Station, in MHz?
a. 4545 b. 3950 c. 3789 d. 4200
6. A satellite equipped with electronic devices to receive, amplify, convert and retransmit signals.
a. Passive b. Active c. Uplink d. Downlink
7. “The orbit of any planet is an ellipse with the sun at one focus”. This is
a. Kepler’s First Law b. Kepler’s Second Law c. Kepler’s Third Law
d. Law of Universal Gravitation 8. The point in an satellite orbit which is
farthest away from the earth a. Perigee
b. Apogee c. Azimuth
d. Ascending node
9. The first active satellite which transmitted telemetry information
a. Telstar 1 b. Aguila II c. Palapa A 1 d. Sputnik
10. The portion of the satellite communication link involving the transmission of traffic from ground station to satellite.
a. Uplink b. Lowlink c. Paylink
d. Bus transmission
11. It is spacecraft places in orbit around the earth carrying on-board microwave receiving and transmitting equipment.
a. Communication satellite b. Terrestrial link
c. Transponder
d. Microwave repeater
12. Satellite position has an/a ___________
angle with respect to the horizon.
a. Azimuth b. Depression c. Elevation d. Critical
13. A satellite that revolves from North to South.
a. Equatorial b. Polar c. Orbital d. Inclined
14. The Kepler’s Law which is also known as the Law of Areas.
a. First Law b. Second Law c. Third Law
d. None of the above
15. The satellite multiple access technique which uses the spread spectrum technology is
a. FDMA b. TDMA c. CDMA d. DAMA
16. The point where the orbit crosses the equatorial plane going from South to North.
a. Ascending Node b. Descending Node c. Apogee
d. Perigee
17. The footprint which covers approximately one-third of the earth’s surface using a 17 degree beamwidth.
a. Spot coverage b. Zonal coverage c. Earth coverage d. Regional coverage
18. An earth station transmits signal to a satellite 38,500 km., directly overhead it.
What is the propagation delay when the signal is received back at the same earth station, in milliseconds.
a. 257 b. 200 c. 285 d. 185
19. When a satellite orbits in the opposite direction as the earth’s rotation with an angular velocity less than that of the earth.
a. Bus transmission b. Payload
c. Prograde d. Retrograde
20. The actual user information conveyed through the satellite system.
a. Bus transmission b. Payload
c. Prograde d. Retrograde
21. The spatial separation between geosynchronous satellites a. 1 – 3 degrees
b. 3 – 6 degrees c. 6 – 8 degrees d. 8 – 10 degrees
22. _______________ detects the satellite signal relayed from the feed and converts it to an electric current, amplifies and lower its frequency.
a. Feedhorn b. Satellite dish c. Satellite receiver d. LNB
23. What kind of battery panels are used in some advance satellites?
a. Gallium Arsenide solar panel b. Silicon based panels
c. Germanium based panels d. Gallium Phosphate solar panel 24. Footprint refers to coverage area in the
globe
a. Satellite radiation polarization b. Satellite navigation
c. Satellite radiation pattern d. Satellite coverage
25. Satellite system or part of a satellite system, consisting of only one satellite and the operating earth station.
a. Satellite system b. Satellite network c. Space system d. Multi-satellite link
26. Known to be the first satellite capable to receive and transmit simultaneously.
a. Syscom I b. Echo I c. Telstar I d. Score
27. A satellite receives an uplink frequency of ____________ MHz from a ground station of 3700 MHz.
a. 8150 MHz b. 1475 MHz c. 2225 MHz d. 5925 MHz
28. What band does VSAT first operate?
a. X-band b. C-band c. Ku-band d. L-band
29. Satellite engine use a. Liquid fuel b. Jet propulsion
c. Ion propulsion system d. Solar jet
30. The first passive satellite transponder a. Early bird
b. Score c. Moon d. Sputnik
31. Satellite used for intercontinental communications are known as a. Comsat
b. Domsat c. Marisat d. Intelsat
32. AsiaSat 1 covers how many countries in Asia?
a. 38 b. 40 c. 44 d. 42
33. An area on the surface of the earth within which the boresight of the steerable satellite beam intended to be pointed.
a. Equivalent boresight area b. Contour boresight area
c. Coordination boresight area d. Effective boresight area
34. Refers to the man-made body sent into continuous orbit around the earth, which provides propagation paths for radio waves between terrestrial transmitters and
receivers.
a. Rocket b. Allotter relay c. Space shuttle
d. Communication satellite 35. What is the basic function of a
communications satellite?
a. To act as a receiving antenna for broadcast FM
b. To compensate for the antenna limitations
c. To eliminate aerodynamic drag d. To acts as receiving antenna for
broadcast AM
36. Typical round-trip distance and transmission time for a satellite relay
a. About 300 ms and 90,000 km,
d. 90,000 mi and 300 ms, respectively 37. The figure of a satellite defines in orbit
a. Circle b. Elliptical c. Parabolic d. Hyperbolic
38. Considered as the corrupting influence(s) in the satellite movement.
a. Gravitational pill between the earth and the orbiting satellite
b. Atmospheric drag on the satellite c. Orbital ellipse
d. All of these
39. The orbit of communications satellites id defined by the angle with respect to the earth equator, which is the 0o plane. What is (are) the basic orbital angle(s)?
a. Polar b. Inclined c. Equatorial d. All of the above
40. How do we measure the position of a satellite?
a. By its elevation angle with respect to the
horizon
b. By its azimuth angle measured clockwise from the direction of true north
c. Through the line of apsides d. A and B are correct
41. Which of the following cause(s) the satellite’s orbital distortions?
a. Sun b. Earth c. Moon
d. All of the above
42. What is the approximate service life of communications satellites?
a. 3 years only b. 5 to 20 years c. 20 to 60 years d. 100 years
43. Representing application of the extraordinary advances technology of satellites to solve the problem of accurate, reliable, 26 hr/day navigation.
a. Global Positioning System (GPS) b. Navigation System using Timing and
Ranging (NAVSTAR) c. A and B are correct d. LORAN
44. A system based on the accurate knowledge by the vessel of the position of each of four satellites, as calculated by the time with respect to the user.
a. GPS b. A or D c. LORAN d. NAVSTAR
45. Segment(s) of a complete GPS system is(are)
a. Control segment b. Space segment c. User segment d. All of these
46. Its function assures the overall system performance and accuracy
a. Control segment b. Space segment c. User segment d. All of these
47. The user segment is used to received signals for the GPS system from the four satellites, compute the time differences, and determine position, while space segment’s function is(are)
a. To received signals for the GPS system from the four satellites, compute the distance differences, and determine position
b. To transmit time codes and orbital position information to the users c. To assure the overall performance and
accuracy
d. All of the above
48. How do you describe the complete signal path of the satellite communications operation?
a. Begins at a ground station, proceeds to an uplink, then to a downlink, and ends at a receiving ground station.
b. From the satellite, to a downlink, tehn to a ground station.
c. Begins at a ground station, proceeds to an uplink, to the satellite itself, to a downlink, and ends at a receiving ground station
d. All of these
49. What is a passive satellite?
a. A satellite capable of receiving, amplifying, and retransmitting
information to and from earth stations.
b. A bent-pipe or a reflector which bounces a signal from one place to another.
c. A satellite which receives transmissions from earth stations, stored them on magnetic tape, and rebroadcast them to ground stations farther along in its orbit.
d. A or C
50. How does communication between satellite be achieved
a. Using satellite cross-links b. Intersatellite links (ISLs) c. Through is ground stations d. A or B is correct
51. Which of the following refers to a delayed repeater satellite?
a. A satellite capable of receiving, amplifying, and retransmitting
information to and from earth stations.
b. A bent-pipe or a reflector which bounces a signal from one place to another.
c. A satellite which receives
transmissions from earth stations, stored them on magnetic tape, and rebroadcast them to ground stations farther along in its orbit.
d. All of these
52. Satellite orbiting in the same direction as earth’s rotation and at an angular velocity greater than the earth is called prograde orbit; and a satellite orbiting which is in the opposite direction as Earth’s rotation or in the same direction but at an angular velocity less than that of Earth is known as
a. Haley’s orbit b. Elliptical orbit c. Equatorial orbit d. Retrograde orbit
53. Are satellites that orbit in a circular pattern with an angular velocity equal to that of earth.
a. Geostationary or geosynchronous satellite
b. Nonsynchronous satellite c. Orbital satellites
d. B or C is correct
54. What do you call of a satellite used to provide satellite services within a single country?
a. Orbital satellite b. Geostationary satellite c. Nonsynchronous satellite d. Domestic satellite or domsat
55. Which of the following is not an advantage of geosynchronous orbit?
a. No need to switch from one satellite to another as satellites orbit overhead, therefore, no breaks of transmission due to switching times.
b. High-altitude geosynchronous satellites can cover a much larger area
c. Geosynchronous satellites require higher transmit powers and more sensitive receivers because of the longer distances and greater path loss.
c. Geosynchronous satellites require higher transmit powers and more sensitive receivers because of the longer distances and greater path loss.