ELECTRONICS AND COMMUNICATION ENGINEERING IMPORTANT MCQ-Microwave,EMFT,Communication Part-3

Q101 THE MAXIMUM POWER THAT CAN BE HANDLED BY A FERRITE COMPONENT IS LIMITED BY
 (a)curie temperature
 (b)saturation magnetization
 (c)line width
 (d)gyromagnetic resonance
 ans-a

Q102 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
 ans-d

Q103 A DUPLEXER IS USED
 (a)to couple two different antennas to a transmitter without mutual interference
 (b)to allow the one antenna to be used for reception or transmission without mutual interference
 (c)to prevent interference b/w two antennas when they are connected to a receiver
 (d)to increases the speed of the pulses in a pulsed radar
 ans-b

Q104 FOR SOME APPLICATION CIRCULAR WAVEGUIDE MAY BE PREFERRED OVER RECTANGULAR ONE BECAUSE OF
 (a)the smaller cross section needed at any frequency
 (b)lower attenuation
 (c)freedom from spurious modes
 (d)rotation of polarisation
 ans-b

Q105 INDICATE WHICH OF THE FOLLOWING CANNOT BE FOLLOWED BY THE WORD WAVEGUIDE
 (a)elliptical
 (b)flexible
 (c)coaxial
 (d)ridged
 ans-c

Q106 IN ORDER TO REDUCE CROSS SECTIONAL DIMENSIONS,THE WAVEGUIDE TO USE IS
 (a)circular
 (b)ridged
 (c)rectangular
 (d)flexible
 ans-b

Q107 FOR LOW ATTENUATION BEST TRANSMISSION MEDIUM IS
 (a)flexible waveguide
 (b)ridged waveguide
 (c)rectangular waveguide
 (d)coaxial line
 ans-c

Q108 A MICROWAVE TUBE AMPLIFIER USES AN AXIAL MAGNETIC FIELD AND A RADIAL ELECTRIC FIELD .THIS IS A
 (a)reflex klystron
 (b)coaxial magnetron
 (c)travelling wave magnetron
 (d)   cfa
 ans-d

Q109 ONE OF THE FOLLOWING IS UNLIKELY TO BE USED AS A PULSED DEVICE.IT IS A
 (a)multicavity klystron
 (b)bwo
 (c)cfa
 (d)twt
 ans-b

Q110 ONE OF THE REASON WHY VACCUM TUBES EVENTUALLY FAIL AT   MICROWAVE FREQUENCIES IS THAT THEIR
 (a)nf increase
 (b)transit time become too short
 (c)shunt capacitive reactances become too large
 (d)series inductive reactances become too small
 ans-a

Q111 INDICATE THE FALSE STATEMENT .TRANSIT TIME IN MICROWAVE TUBE WILL BE REDUCED IF
 (a)the electrodes are brought together
 (b)a higher anode current is used
 (c)multiple or coaxial leads r used
 (d)the anode voltage is made large
 ans-c

Q112 THE MULTICAVITY KLYSTRON
 (a)is not a good low level amplifier because of noise
 (b)has a high repeller voltage to ensure a rapid transit time
 (c)is not suitable for pulsed operation
 (d)needs a long transit time through the buncher cavity to ensure current modulation
 ans-a

Q113 INDICATE THE FALSE STATEMENT.KLYSTRON AMPLIFIERS MAY USE INTERMEDIATE CAVITIES TO
 (a)prevent the oscillations that occurs in two cavity klystron
 (b)increase the bw
 (c)improve the power gain
 (d)increase the efficiency of the klystron
 ans-a

Q114 THE TWT IS SOMETIMES PREFERRED TO THE MULTICAVITY KLYSTRON AMPLIFIER ,BECAUSE THE FORMAR
 (a)is more efficient
 (b)has a greater bw
 (c)has a higher number of modes
 (d)produses a higher o/p power
 ans-b

Q115 THE TRANSIT TIME IN THR REPELLER SPACE OF A REFLEX KLYSTRON MUST BE N+3/4 CYCLE TO ENSURE THAT
 (a)electrons r accelerated by the gap voltage on their return
 (b)returning electrons gives energy to rhe gap oscillations
 (c)it is equal to the period of the cavity oscillations
 (d)the repeller is not damaged by stricking electrons
 ans-b

Q116 THE CAVITY MAGNETRON USE STRAPPING TO
 (a)prevent mode jumping
 (b)prevent cathod back heating
 (c)ensure bunching
 (d)improve the phase focusing
 ans-a

Q117 A MAGNETIC FIELD IS USED IN THE CAVITY MAGNETRON TO
 (a)prevent anode current in the absence of oscillations
 (b)ensure that the oscillations r pulsed
 (c)help in focusing the electron beam,thus preventing spreading
 (d)ensure that the electrones will orbit around the cathod
 ans-d

Q118 TO AVOID DIFFICULTIES WITH STRAPPING AT HIGH FREQUENCYS,THE TYPE OF CAVITY STRUCTUER USED IN THE MAGNETRON IS THE
 (A)HOLE AND SLOT
 (b)slot
 (c)vane
 (d)rising sun
 ans-d

Q119 THE PRIMARY PURPOSE PF THE HELIX IN THE TWT IS
 (a)prevent the electron beam spreading in the long tube
 (b)reduce axial velocity of the rf field
 (c)ensure broadband operation
 (d)reduce the noise figure
 ans-b

Q120THE ATTENUATOR IN THE TWT IS USED FOR
 (a)help focusing
 (b)prevent oscillations
 (c)prevent saturatuion
 (d)increase gain
 ans-b

Q121 PERIODIC PERMANENT MAGNET FOCUSING IS USED WITH TWT TO
 (a)allow pulsed operation
 (b)improve electron bunching
 (c)avoid the bulk of an electromagnet
 (d)allow coupled cavity operation at the high frequency
 ans-c

Q122 THE TWT IS SOMETIMES PREFERRED TO THE MAGNETRON AS A RADAR TRANSMITTER O/P TUBE BECAUSE IT IS
 (a)capable of longer duty cycle
 (b)a more efficient amplifier
 (c)more broadband
 (d)less noise
 ans-a

Q123 A MAGNETRON WHOSE OSCILLATING FREQUENCY IS ELECTRONICALLY ADJUSTABLE OVER A WIDE RANGE IS CALLED
 (a)coaxial magnetron
 (b)ditcher tuned magnetron
 (c)frequency agile magnetron
 (d)vtm
 ans-d

Q124 INDICATE WHICH OF THEE FOLLOWING IS NOT A TWTY SLOW WAVE STRUCTURE
 (a)periodic permanent magnet
 (b)coupled cavity
 (c)helix
 (d)ring bar
 ans-a

Q125 THE GLASS TUBE OF A TWT MAY BE COATED WITH AQUADAG TO
 (a)help focusing
 (b)provide attenuation
 (c)improve bunching
 (d)increse gain
 ans-b

Q126 A BACKWARD WAVE OSCILLATOR IS BASED ON THE
 (a)rising sun magnetron
 (b)cross field amplifier
 (c)coaxial magnetron
 (d)travelling wave tube
 ans-d

Q127 A PARAMATRIC AMPLIFIER MUST BE COOLED
 (a)because paramatric amplifications generates a lot of heat
 (b)to increase bw
 (c)because it cannot operate at room temp
 (d)to improve the noise performance
 ans-d

Q128 A RUBY MASER AMPLIFIER MUST BE COOLED
 (a)because maser amplifiers generats a lot of heat
 (b)to increase bw
 (c)because it can not operate at room temp
 (d)to improve the noise performance
 ans-c

Q129 THE TRANSMISSION SYSTEM USING TWO GROUND PLANES IS
 (a)microstrip
 (b)elliptical waveguide
 (c)parallel wire line
 (d)stripline
 ans-d

Q130 INDICATE THE FALSE STATEMENT.AN ADVANTAGE OF USING STTRIPLINE OVER WAVVGUIDE IS its
 (a)smaller bulk
 (b)greater bw
 (c)higher power handling capability
 (d)greater compatibility with solid state device
 ans-c

Q131 INDICATE THE FALSE STATEMENT.AN ADVANTAGE OF USING STRIPLINE OVER MICROSTRIPLINE IS ITS
 (a)easier integration with semiconductor devices
 (b)lower tendency to radiate
 (c)higher isolation b/w ajacent ckts
 (d)higher q
 ans-a

Q132 SURFACE ACOUSTIC WAVE PROPAGATE IN
 (a)gallium arsenide
 (b)indium phosphste
 (c)stripline
 (d)quartz crystal
 ans-d

Q133 SAW DEVICES MAY BE USED AS
 (a)transmission media like stripline
 (b)filters
 (c)uhf amplifiers
 (d)oscillator at milimiter frequency
 ans-b

Q134 INDICATE THE FALSE STATEMENT.FET’S R PREFERRED TO BIPOLAR TRANSISTOR AT THE HIGHEST FREQUENCIES BECAUSE THEY ARE
 (a)less noisy
 (b)lend themselves more readily to integration
 (c)are capable of higher efficiencies
 (d)can provide higher gain
 ans-b

Q135 THE BIGGEST ADVANTAGE OF THE TRAPATT DIODE OVER THE IMPATT DIODE IS IT’S
 (a)lower noise
 (b)higher efficiency
 (c)ability to operate at higher frequency
 (d)lesser sensitivity to harmonics
 ans-b

Q136 INDICATE WHICH OF THE FOLLOWING DIODE WILL PRODUCE THE HIGHEST PULSED POWER O/P
 (a)varactor
 (b)gunn
 (c)schottky diode
 (d)rimpatt diode
 ans-d

Q137 INDICATE WHICH OF THE FOLLOWING DIODE DOES NOT USES -VE RESISTANCE IN IT’S OPERATION
 (a)backward
 (b)gunn
 (c)impatt
 (d)tunnel
 ans-a

Q138 ONE OF THE FOLLOWING IS NOT USED AS A MICROWAVE MIXER OR DETECTOR
 (a)crystal diode
 (b)schottky barrier diode
 (c)backward diode
 (d)pin diode
 ans-d

Q139 ONE OF THE FOLLOWING MICROWAVE DIODE IS SUITABLE FOR VERY LOW POWER OSCILLATOR ONLY
 (a)tunnel
 (b)avalanche
 (c)gunn
 (d)impatt
 ans-a

Q140 THE TRANSFERRED-ELECTRON BULK EFFECT OCCURS IN
 (a)germenium
 (b)gallium arsenide
 (c)silicon
 (d)metal semiconductor junctions
 ans-b

Q141 THE GAIN BW FREQUENCY OF A MICROWAVE TRANSISTOR,is THE FREQUENCY AT WHICH
 (a)alpha of the transistor falls by 3db
 (b)beta of the transistor falls by 3 db
 (c)power gain of the transistor falls to unity
 (d)beta of the transistor falls to unity
 ans-d

Q142 A VARACTOR DIODE MAY BE USEFUL AT MICROWAVE FREQUENCY(INDICATE THE FALSE STATEMENT)
 (A)for electronic tunning
 (b)for frequency multiplication
 (c)as an oscillator
 (d)as a paramatric amplifier
 ans-c

143 FOR A MICROWAVE TRANSISTOR TO OPERATE AT THE HIGHEST FREQUENCY(INDICATE THE FALSE STATEMENT)
 (a)collector voltage must be large
 (b)collector current must be large
 (c)base should be thin
 (d)emitter area must be large
 ans-d

Q144 IF HIGH ORDER FREQUENCY MULTIPLICATION IS REQUIRED FROM A DIODE MULTIPLIER
 (a)the resestive cutoff frequency must be high
 (b)a small value of base resistance is required
 (c)a step recovery diode must be used
 (d)a large range of capacitance variation is needed
 ans-c

Q145 TRAVELLING WAVE PARAMATRIC AMPLIFIER ARE USED TO
 (a)provide a greater gain
 (b)reduce the number of varactor diode required
 (c)avoid the need of coupling
 (d)provide a greater bw
 ans-d

Q146 A PARAMATRIC AMPLIFIER SOMETIMES USES A CIRCULATOR TO
 (a)prevent noise feedback
 (b)allow antenna to be used simultaneously for transmission and reception
 (c)seperate the signal and idler frequency
 (d)permit more efficient pumping
 ans-a

Q147 THE NON DEGENERATED ONE PORT PARAMATRIC AMPLIFIER SHOULD HAVE A HIGH RATIO OF PUMP TO SIGNAL FREQUENC BECAUSE THIS
 (a)permits satisfactory high frequency operation
 (b)yields a low nf
 (c)reduces pump power required
 (d)permits satisfactory low frequency operation
 ans-b

Q148 THE TUNNEL DIODE
 (a)has a tiny hole through it’s center to facilitate tunneling
 (b)ia a point contact diode with a very high reverse resistance
 (c)uses a high doping level to provide a narrow junction
 (d)works by quantam tunneling exhibited by gallium arsenide only
 ans-c

Q149 A TUNNEL DIODE IS LOSELY  COUPLED TO IT’S CAVITY IN ORDER TO
 (a)increase the frequency stability
 (b)increase the available -ve resistance
 (c)faciliting tunning
 (d)allow operation at the high frequency
 ans-a

Q150 THE -VE RESISTANCE IN A TUNNEL DIODE
 (a)is amximum at the peak point of the characteristics
 (b)is available b/w peak n vally point
 (c)is maximum at valley point
 (d)may be improved by use of reverse bias
 ans-b

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ELECTRONICS AND COMMUNICATION ENGINEERING IMPORTANT MCQ-Microwave,EMFT,Communication Part-4
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