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Home ‣ Electronics and Communication Engineering ‣ Microwave Communication Comments
  • Question

  • Assertion (A): In the interaction region of magnetron an electron is subjected to three forces: force due to electric field, force due to magnetic field and centrifugal force.

    Reason (R): The mechanism of generation of microwaves, in a magnetron, involves interaction of electromagnetic fields with electrons moving in static electric and magnetic fields oriented at right angles to each other.


  • Options
  • A. Both A and R are correct and R is correct explanation of A
  • B. Both A and R are correct but R is not correct explanation of A
  • C. A is correct but R is wrong
  • D. A is wrong but R is correct

  • Correct Answer
  • Both A and R are correct and R is correct explanation of A 

    Explanation
    It is somewhat similar to TWT and can deliver microwave power over a wide frequency band.

    It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT.

    The growing RF wave travels in opposite direction to the electron beam.

    The frequency of wave can be changed by changing the voltage which controls the beam velocity.

    Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current.

    It features are:

    1. Frequency range - 1 GHz to 1000 GHz.

    2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed).

    It is used as signal source in transmitters and instruments.

    Microwave Communication problems

    Search Results

    • 1. If antenna diameter is increased four times, the maximum range is increased by a factor of

    • Options
    • A. 2
    • B. 2
    • C. 4
    • D. 0.2
      • Discuss
    • 2. Microwave links are typically 50 km apart

    • Options
    • A. because of atmospheric attenuation
    • B. because of output tube power limitation
    • C. because of earth's curvature
    • D. to ensure that applied dc voltage is not excessive
      • Discuss
    • 3. Ga As exhibits negative differential mobility

    • Options
    • A. True
    • B. False
      • Discuss
    • 4. A reflex klystron oscillator uses

    • Options
    • A. one cavity resonator
    • B. two cavity resonators
    • C. three cavity resonators
    • D. none of the above
      • Discuss
    • 5. If a line having Z0 = 300 ? 0 W is short circuited at far end, VSWR is

    • Options
    • A. 0 
    • B. 1
    • C. ?
    • D. 2
      • Discuss
    • 6. If VSWR is infinite, the transmission line is terminated in

    • Options
    • A. short circuit
    • B. complex impedance
    • C. open circuit
    • D. either (a) or (c)
      • Discuss
    • 7. Impedance inversion may be obtained with

    • Options
    • A. a short circuited stub
    • B. a quarter wave line
    • C. an open circuited stub
    • D. a half wave line
      • Discuss
    • 8. In a circular waveguide TE21 mode has lowest cutoff frequency

    • Options
    • A. True
    • B. False
      • Discuss
    • 9. Assertion (A): For high frequency lines inductive reactance is very high as compared to ac resistance.

      Reason (R): Due to skin effect ac resistance of line is higher than dc resistance.


    • Options
    • A. Both A and R are correct and R is correct explanation of A
    • B. Both A and R are correct but R is not correct explanation of A
    • C. A is correct but R is wrong
    • D. A is wrong but R is correct
      • Discuss
    • 10. For matching over a range of frequencies in a transmission line it is best to use

    • Options
    • A. a balun
    • B. a broad band directional coupler
    • C. double stub
    • D. a single stub of adjustable position
      • Discuss

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