Microwave Communication Multiple Choice Questions (MCQs) & Answers

Microwave Communication Multiple Choice Questions(MCQs)& Answers Microwave Communication

Microwave Communication Multiple Choice Questions(MCQs)& Answers

CONCEPTS & THEORIES

microwave-communication

About Microwave Communication


Within the broader spectrum of radio frequency (RF) communications, point-to-point communications are usually carried out using microwave frequencies between 1 GHz and 100 GHz along line-of-sight (LOS) paths called links.
It is a line-of-sight wireless communication technology that uses high frequency beams of radio waves to provide high speed wireless connections that can send and receive voice, video, and data information.
Microwave radio transmission is commonly used in point-to-point communication systems on the surface of the Earth, in satellite communications, and in deep space radio communications. Other parts of the microwave radio band are used for radars, radio navigation systems, sensor systems, and radio astronomy.

Microwave Frequency Bands


Microwave signals are often divided into three categories:
1. ultra high frequency (UHF) (0.3-3 GHz);
2. super high frequency (SHF) (3-30 GHz); and
3. extremely high frequency (EHF) (30-300 GHz).
In addition, microwave frequency bands are designated by specific letters. The designations by the Radio Society of Great Britain are given below.
Microwave frequency bands vs Designation Frequency range
L band-1 to 2 GHz
S band-2 to 4 GHz
C band-4 to 8 GHz
X band-8 to 12 GHz
Ku band-12 to 18 GHz
K band-18 to 26.5 GHz
Ka band-26.5 to 40 GHz
Q band-30 to 50 GHz
U band-40 to 60 GHz
V band-50 to 75 GHz
E band-60 to 90 GHz
W band-75 to 110 GHz
F band-90 to 140 GHz
D band-110 to 170 GHz

QUESTIONS

Microwave Communication Multiple Choice Questions(MCQs)& Answers

1 Which of the following permits a microwave signal to travel in one direction with virtually no loss, but severely attenuates any signal attempting to travel in the reverse direction?
A Isolator
B Wave trap
C Tunnel diode
D Circulator

Answer: Isolator
2 A thin layer of dirt and grime coverts the reflecting surface of the parabolic dish of a radar set. The particular effect on the performance of the radar will be
A A decrease in range
B A reduction in horizontal resolution
C No noticeable effect
D A decrease in gain

Answer: No noticeable effect
3 The main frequency determining element of a klystron is
A The repeller voltage
B The accelerating voltage
C Its resonant cavity
D Its mode of operation

Answer: Its resonant cavity
4 If the duration of the radar transmitted pulse, on a particular range of operation, is increased, the required bandwidth of the receiver’s IF amplifiers
A Must remain as before
B Must be increased
C May be decreased
D Must be doubled

Answer: May be decreased
5 Coupling into and out of a traveling-wave tube can be accompanied by a
A Direct coax-helix match
B Cavity match
C Waveguide match
D All of the above

Answer: All of the above
6 At what position is the input signal inserted into a traveling-wave tube?
A At the cathode end of the helix
B At the collector
C At the collector end of the helix
D At the control grid of the electron gun

Answer: At the cathode end of the helix
7 The cavity resonator
A Is equivalent to an LC resonant circuit
B In a reflect klystron has its output taken from the reflector plate
C Produces a frequency which is independent of the cavity size.
D Has a low Q factor for narrow operation.

Answer: Is equivalent to an LC resonant circuit
8 A shipboard equipment which measures the distance between the ship’s bottom and the ocean floor.
A Fathometer
B Echosounder
C LORAN
D SONAR

Answer: SONAR
9 In microwave transmission using digital radio, what causes most intersymbol interference?
A Delayed spreading
B Rayleigh fading
C Random Doppler shift
D Slow fading

Answer: Delayed spreading
10 Which causes multipath or frequency-selective fading?
A Small reflector
B Nearer reflector
C Further reflector
D Large reflector

Answer: Large reflector
11 Which of the reception problems below that is not due to multipath?
A Delayed spreading
B Rayleigh fading
C Random Doppler shift
D Slow fading

Answer: Slow fading
12 What do you call an attenuation that occurs over many different wavelengths of the carrier?
A Rayleigh fading
B Rician fading
C Wavelength fading
D Slow fading

Answer: Slow fading
13 A Class-S Emergency Position-Indicating Radio Beacon (E.P.I.R.B)
A Must be capable of floating or being secured to a survival
B Must have its battery replaced after emergency use
C May be tested during the first five minutes of any hour
D All of these

Answer: All of these
14 A PPI cathode-ray tube as used on a radar set
A Is used to check the percentage of modulation
B Indicates both the range and azimuth of a target
C Indicates only the range of a target
D Is used for receiver alignment

Answer: Is used for receiver alignment
15 The resonant frequency of a cavity resonator depends upon
A The mode of operation
B Its electrical dimensions
C Its physical dimensions
D The capacitor which tunes it

Answer: Its physical dimensions
16 The maximum usable range of the usual radar set (on any particular range setting) is determined by
A The width of the transmitted pulses
B The interval between transmitted pulses
C The bandwidth of the receiver IF stages
D The duty cycle

Answer: The interval between transmitted pulses
17 A reflex klystron is oscillating at the frequency of its resonant cavity. If the reflector voltage is made slightly less negative, the
A Oscillation will cease
B Output power would increase
C The frequency will decrease
D Bunching would occur earlier in time

Answer: The frequency will decrease
18 The coarse frequency adjustment of a reflex klystron is accomplished by
A The AFC system
B Adjusting the flexible wall of the resonant cavity
C An adjustment in the synchronizer
D Varying the repeller voltage

Answer: Adjusting the flexible wall of the resonant cavity
19 In a pulsed radar set, the STC circuit is used to
A Improve the target bearing resolution
B Increases receiver sensitivity for echoes from targets
C Vary the pulse frequency in order to control the maximum target
D Reduce interference from the effects of sea return

Answer: Reduce interference from the effects of sea return
20 In a pulsed radar set, the function of the duplexer is to
A Aid in calibrating the display unit
B Prevent frequency drift in the klystron
C Allow the transmitter and the receiver to operate from a common antenna
D All of these

Answer: Allow the transmitter and the receiver to operate from a common antenna
21 The highest frequency which a conventional vacuum-tube oscillator can generate is not limited by the
A Electron transit time
B Distributed lead inductance
C Inter-electrode capacitance
D Degree of emission from the cathode

Answer: Degree of emission from the cathode
22 Microwave frequencies are normally regarded as those in the range of
A 1 to 500 MHz
B 1000 to 10,000 GHz
C 1 to 100 GHz
D 10 to 1000 GHz

Answer: 1 to 100 GHz
23 Which of the following operating frequencies is used for the modern loran navigational system?
A Loran C: 100 kHz
B Loran D: 10.2 kHz
C Loran A: 1950 kHz
D Loran B: 900 kHz

Answer: Loran C: 100 kHz
24 Which of the following is used as a high power microwave oscillator?
A Thyratron
B Magnetron
C Klystron
D Reflex-klystron

Answer: Magnetron
25 Which of the following is used as an oscillator device in the SHF band?
A Thyratron tube
B Tunnel diode
C Klystron tube
D Both B and C

Answer: Both B and C
26 What is the purpose of the electromagnetic field which surrounds a traveling-wave tube?
A To accelerate the electron
B To velocity modulate the electron beam
C To keep the electrons from spreading out
D To slow down the signal on the helix

Answer: To keep the electrons from spreading out
27 A traveling-wave tube (TWT) amplifies by virtue of
A The absorption of energy by the signal from an electron stream
B The effect of an external magnetic field
C The energy contained the cavity resonators
D The energy liberated form the collector

Answer: The absorption of energy by the signal from an electron stream
28 When it is desired that short-range targets be clearly seen on a pulsed-radar set, it is important that the receiver and display system have
A A long time constant
B Low-pass filters
C The shortest possible time
D The restricted high-frequency response

Answer: The shortest possible time
29 The aquadag coating on the inside of PPI tube is used
A To focus the beam of primary electrons
B To shield the electron beam from unidirectional magnetic
C As a second anode and to prevent the build-up of secondary field
D All of these

Answer: As a second anode and to prevent the build-up of secondary field
30 A magnetron is operated at a duty cycle of 0.001. It has a peak power output of 100 kilowatts. Its average power is
A 10,000 watts
B 100 watts
C 1,000 watts
D 1,000,000 watts

Answer: 100 watts
31 A high-power microwave pulse of the order of megawatts can be generated by a
A traveling-wave tube
B magnetron
C reflex klystron
D Gunn diode

Answer: magnetron
32 Theoretically electromagnetic radiation field strength varies in inverse proportion to the square of the distance, but when atmospheric attenuation effects and the absorption of the terrain are taken into account the attenuation can be as high as the inverse _______ power of the distance.
A Third
B Fourth
C Fifth
D Sixth

Answer: Sixth
33 Rainfall is an important factor for fading of radio waves at frequencies above
A 10 GHz
B 100 GHz
C 1 GHz
D 100 MHz

Answer: 10 GHz
34 the antenna separations (in meters) required for optimum operation of a space diversity system can be calculated from: where R = effective earth radius (m) and L = path length (m)
A S = 2λR/L
B S = 3λR/L
C S = λR/RL
D S = λR/L

Answer: S = 3λR/L
35 If k-factor is greater than 1, the array beam is bent
A Away from the earth
B towards the ionosphere,
C towards the earth
D towards the outer space

Answer: towards the earth

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