Radiation And Microwave Techniques Set 5

Electrical Engineering

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This set of Radiation and Microwave Techniques Multiple Choice Questions & Answers (MCQs) focuses on Radiation And Microwave Techniques Set 5

Q1 | The phase velocity for the TE10 mode in an air filled rectangular waveguide is
  • less than c
  • greater than c
  • equal to c
  • none of the above
Answer: equal to c
Q2 | The phase velocity of an electrometric wave propagating in a hollow metallicrectangular waveguide in the TE10 mode is
  • equal to its group velocity
  • less than velocity of light in free space
  • equal to velocity of light in free space
  • greater than velocity of light in free space
Answer: equal to velocity of light in free space
Q3 | . Consider an air filled rectangular waveguide with a cross – section of5 cm × 3 cm.For this waveguide, the cut off frequency (in MHz) of TE21mode is
  • 7.81 ghz
  • 9.01 ghz
  • 11.2 ghz
  • 6.89 ghz
Answer: 7.81 ghz
Q4 | The cut off frequency of waveguide depends upon
  • the dimensions of the waveguide.
  • the dielectric property of the medium in the waveguide.
  • the characteristic impedance of the waveguide
  • the transverse and axial components of the fields
Answer: the dimensions of the waveguide.
Q5 | ency forthe dominant mode is
  • 2.5 ghz
  • 10 ghz
  • 5 ghz
  • 12.5 ghz
Answer: 2.5 ghz
Q6 | ency of 30GHz is (free space impedance 0 =377 Ω)
  • 308 Ω
  • 400 Ω
  • 355 Ω
  • 461 Ω
Answer: 400 Ω
Q7 | When an electromagnetic waves are propagated in a waveguide
  • they travel along a broader walls of the guide
  • they are reflected from the walls but do not travel along them
  • they travel through the dielectric without touching the walls
  • they travel along all four walls of the waveguide
Answer: they are reflected from the walls but do not travel along them
Q8 | Which of the following waveguides tuning components is not easily adjustable?
  • screw
  • stub
  • iris
  • plunger
Answer: iris
Q9 | A directional coupler with three or more holes is sometimes used in preference tothe two-hole couple
  • because it is more efficient
  • to increase coupling of signal
  • to reduce spurious mode generation
  • to increase the bandwidth of the system
Answer: to reduce spurious mode generation
Q10 | A ferrite is
  • a nonconductive with magnetic properties
  • an intermetallic compound with particularly good conductivity
  • an insulator which heavily attenuates magnetic fields
  • a microwave semiconductor invented by faraday
Answer: a nonconductive with magnetic properties
Q11 | A PIN diode is
  • a metal semiconductor point-contact diode
  • a microwave mixer diode
  • suitable for use as a microwave switch
  • often used as a microwave detector
Answer: suitable for use as a microwave switch
Q12 | A microwave tube amplifier uses an axial magnetic field and a radial electric field.This is the
  • reflex klystron
  • coaxial magnetron
  • travelling wave magnetron
  • cfa
Answer: coaxial magnetron
Q13 | Indicate the false statement. Transit time in microwave tubes will be reduced if
  • the electrodes are brought closer together
  • a higher anode current is used
  • multiple or coaxial leads are used
  • the anode voltage is made larger
Answer: multiple or coaxial leads are used
Q14 | The multicavity klystron
  • is not a good low-level amplifier because of noise
  • has a higher repeller voltage to ensure a rapid transit time
  • is not suitable for pulsed operation
  • needs a long transit time through the buncher cavity to ensure current modulation
Answer: is not a good low-level amplifier because of noise
Q15 | The cavity magnetron uses strapping to
  • prevent mode jumping
  • prevent cathode back heating
  • ensure bunching
  • improve the phase focusing effect
Answer: prevent mode jumping
Q16 | The primary purpose of the helix in a traveling-wave tube is to
  • prevent the electron beam from spreading in the long tube
  • reduce the axial velocity of the rf field
  • ensure broadband operationreduce the noise figure
  • none ofthe above.
Answer: reduce the axial velocity of the rf field
Q17 | The TWT is sometimes preferred to the magnetron as a radar transmitter outputtube because it is
  • capable of a longer duty cycle
  • a more efficient bandwidth
  • more broadband
  • less noisy
Answer: capable of a longer duty cycle
Q18 | A magnetron whose oscillating frequency is electronically adjustable over a widerange is called a
  • coaxial magnetron
  • dither-tuned magnetron
  • frequency agile magnetron
  • vtm
Answer: vtm
Q19 | A disadvantage of microstrip compared with strip line is that micro strip
  • does not readily lend itself to printed circuit techniques
  • is more likely to radiate
  • is bulkier
  • is more expensive and complex to manufacture
Answer: does not readily lend itself to printed circuit techniques
Q20 | For best low-level noise performance in the X-band, an amplifier should use
  • a bipolar transistor
  • a gunn diode
  • a step-recovery diode
  • an impatt diode
Answer: a step-recovery diode
Q21 | Considering a coaxial transmission line, maximum voltage on the line divided bythe minimum voltage equals the
  • characteristic impedance
  • iswr
  • vswr
  • inductive reactance
Answer: vswr
Q22 | In a transmission line, if the SWR or maximum current to a minimum currentratio of 2:1, the ratio of the maximum voltage to the minimum voltage is
  • 1:4
  • 4:1
  • 1:2
  • 2:1
Answer: 2:1
Q23 | The load is properly matched with the transmission line if the standing wave ratiois equal to
  • 50
  • 10
  • 5
  • 1
Answer: 1
Q24 | Which of the following is used to measure SWR?
  • multimeter
  • spectrum analyzer
  • reflectometer
  • oscilloscope
Answer: reflectometer
Q25 | Reflections on a transmission line can occur when
  • impedance of the source and load are matched
  • impedance of the source and the load are mismatched
  • resonance conditions are obtained
  • power transfer between source and load is maximum
Answer: impedance of the source and the load are mismatched
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