Microwaves and radar system - Electronics Engineering test questions

Microwaves and radar system - Electronics Engineering test questions

(1) Microwave energies propagate the length of the waveguide by __________ its side walls.

(A) Refraction off
(B) Reflection off
(C) Moving off
(D) None of the above

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(2) TRAPATT diode is preferred over IMPATT diode because of

(A) High η
(B) Less sensitivity to harmonics
(C) Lower noise
(D) Ability to operate at higher frequencies

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(3) Two entities that are combined to form a Magic Tee are

(A) One H? and two E plane tees
(B) One H? and one E plane tee
(C) Two H? and two plane tees
(D) Two H? and one E plane tee

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(4) Which one of the following device behaviour is governed by bulk effect?

(A) IMPATT diode
(B) Gunn diode
(C) Tunnel diode
(D) PIN diode

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(5) To couple two waveguides a choke flange may be used

(A) As it is simpler than any other method of joining
(B) To help the alignment of the waveguides
(C) To compensate for discontinuities at the joint
(D) T increase the bandwidth of the system

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(6) Standard mismatching in microwave circuits have SWR from

(A) 1 : 0.5 to 2 : 1
(B) 1.2 : 1 to 2 : 1
(C) 0.5 : 1 to 2 : 1
(D) 1.33 : 1 to 2 : 1

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(7) The waveguide tuning component, which is not easily adjustable, is

(A) Screw
(B) Iris
(C) Stub
(D) Plunger

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(8) Operating frequency of the reflex klystron is as high as

(A) 70,000 MHz
(B) 50,000 MHz
(C) 20,000 MHz
(D) 10,000 MHz

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(9) Let the peak power = 10,00,000 W and average power = 800 W. The duty cycle will be

(A) 0.008 %
(B) 0.8 %
(C) 0.08 %
(D) 8 %

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(10) The microwave tube that uses buncher and catcher cavities is

(A) Klystron
(B) Magnetron
(C) Reflex klystron
(D) Travelling-wave tube

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(12) A frequency at which microwave ovens operate is

(A) 50 μHz
(B) 2.45 GHz
(C) 3.3 GHz
(D) 4.5 GHz

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(13) In the repeller space of a reflex klystron, the transit time must be n + ¾ cycle to ensure that

(A) It is equal to the period of the cavity oscillations
(B) The repeller is not damaged by striking electrons
(C) Returning electrons has given energy to the gap oscillations
(D) Electrons are accelerated by the gap voltage on their return

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(14) ___________ is unlikely to be used as a pulsed device

(A) BWO
(B) TWT
(C) CFA
(D) Multi-cavity klystron

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(15) The microwave tube amplifier that uses an axial magnetic field and radial electric field is

(A) Reflex klystron
(B) CFA
(C) Coaxial magnetron
(D) Travelling wave magnetron

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(16) Which of the following materials are generally preferred for waveguides?

(A) Cast iron and steel
(B) Non metallic solids including plastic
(C) High carbon steel and vanadium steel
(D) Brass and aluminium

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(17) Which of the following statement is false? In microwave tubes Transit time will be reduced if

(A) The electrodes are brought closer together
(B) Multiple or coaxial leads are used
(C) The anode voltage is made larger
(D) The anode current is made larger

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(18) With a parabolic reflector cassegrain feed is used to

(A) Increase the system beam width
(B) Increase the system gain
(C) Allow the feed to be placed at convenient point
(D) Reduce the main reflector size

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(19) What is the primary purpose of the helix in a travelling wave tube?

(A) To reduce noise figure
(B) To prevent the electron beam from spreading in the long tube
(C) To reduce the axial velocity of the RF field
(D) To ensure broadband operation

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(20) In a magnetron why does the electrons travel in a cycloidal path?

(A) Strong field is supplied by the permanent magnet
(B) The cathode is positive
(C) The anode is negative
(D) The cavities are resonant

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(21) In one resolution of the scanner the number of heading marker lines produced will be

(A) 10
(B) 8
(C) 4
(D) 1

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(22) Sea clutter returns occur

(A) Due to reflections from land
(B) Due to reflections from rain clouds
(C) At short ranges
(D) None of the above

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(23) A control voltage is produced in an AFC to control the frequency of

(A) Local oscillators
(B) Magnetrons
(C) Wobbulator
(D) PRF generator

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(24) For IFF the one that is used is

(A) Ordinary radar
(B) Beacon
(C) CW radar
(D) MTI

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(25) From the options given below which one is not a display method?

(A) Computer feeding
(B) PPI
(C) A scope
(D) Monopulse conical scanning

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(26) Consider a radar having the capture area of receiving antenna A. The maximum range will be proportional to

(A) √A
(B) 1 / √A
(C) A
(D) A^²

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(27) Let the generator’s transmitting frequency be 3 GHz. A target is moving radially towards generator with a velocity of 360 Km/hour. The frequency of the target will be

(A) 1 KHz
(B) 1.5 KHz
(C) 2 KHz
(D) 300 Hz

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(28) Aircraft surveillance radars mostly operate in

(A) C band
(B) S band
(C) L band
(D) X band

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(29) On which factor the maximum range of radar depends?

(A) Pulse duration
(B) Pulse energy
(C) Pulse frequency
(D) None of the above

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(30) To track and target the location precisely retards operate in

(A) S band
(B) L band
(C) D band
(D) None of the above

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(31) In a MTI radar, the quartz delay line is used to

(A) Match the phase of COHO and output oscillator
(B) Match the phase of COHO and STALO
(C) Match the signal with echo
(D) Subtract a complete scan from previous scan

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(32) In a radar when the return echo arrives after the allocated pulse interval, then

(A) The receiver will get overloaded
(B) It may interfere with the operation of the transmitter
(C) The target will appear closer than it really is
(D) It will not be received

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(33) What is the cause of “second time around” echoes?

(A) Echoes that arrive after transmission of the next pulse
(B) Extreme ends of bandwidth
(C) Second time reflection from target
(D) Echoes returning from targets beyond the cathode ray tube range

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(34) The remedy for the problem of “blind speed “ is

(A) Variation of PRF
(B) Use of monopulse
(C) Use of MTI
(D) Change in Doppler frequency

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(35) Let the cross-section of a target is changing. In this case tracking is generally done by

(A) Duplex scanning
(B) Monopulse
(C) Duplex switching
(D) Any of the above

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(36) In MTI radar, COHO operates

(A) Pulse repetition frequency
(B) At supply frequency
(C) Station frequency
(D) At intermediate frequency

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(37) VOR stands for

(A) Visually operated radar
(B) Voltage output of regulator
(C) VHF omni range
(D) None of the above

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(38) What will be the value of PRT when PRF =1500 Hz?

(A) 5000 μsec
(B) 666 μsec
(C) 1200 μsec
(D) 60 μsec

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(39) In synchronization with the antenna, the deflection coils must be rotated to ensure correct

(A) Bearing of target displayed
(B) Range of target displayed
(C) Frequency of transmission
(D) Amplitude of echoes

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(40) Let the maximum range of radar be doubled with all the other factors remaining constant. The peak power must be increased

(A) 32 fold
(B) 4 fold
(C) 16 fold
(D) 8 fold

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