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Home Electronics and Communication Engineering Microwave Communication See What Others Are Saying!
  • Question
  • Assertion (A): A backward wave oscillator can be used as a sweep generator.

    Reason (R): The frequency of oscillation of a backward wave oscillator can be changed by varying the voltage which controls the beam velocity.


  • 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.


    More questions

    • 1. If an amplifier with gain of - 1000 and feedback factor ? = - 0.1 had a gain change of 20% due to temperature, the change in gain of the feedback amplifier would be

    • Options
    • A. 10%
    • B. 5%
    • C. 0.2%
    • D. 0.01%
    • Discuss
    • 2. Permeability is analogous to

    • Options
    • A. resistivity
    • B. retentivity
    • C. conductivity
    • D. coercivity
    • Discuss
    • 3. In a Gunn diode oscillator drift velocity of electron is 107 cm/s and active region length is 10 x 10-4 cm. The natural frequency of oscillation is

    • Options
    • A. 1 MHz
    • B. 10 MHz
    • C. 1 GHz
    • D. 10 GHz
    • Discuss
    • 4. A cycloconverter is a group of controlled rectifiers.

    • Options
    • A. True
    • B. False
    • Discuss
    • 5. If the valence electron is separated from a copper atom, the remaining part of atom has a net charge of

    • Options
    • A. 1
    • B. - 1
    • C. 0
    • D. + 3
    • Discuss
    • 6. A single phase bridge type cycloconverter uses eight thyristors.

    • Options
    • A. True
    • B. False
    • Discuss
    • 7. ?r is determined by the atomic structure of the dielectric.

    • Options
    • A. True
    • B. False
    • Discuss
    • 8. An SBS can conduct is one direction only.

    • Options
    • A. True
    • B. False
    • Discuss
    • 9. The resistivity of intrinsic semiconductors, at room temperature, is of the order of

    • Options
    • A. 1 ?-m
    • B. 1000 ?-m
    • C. 106 ?-m
    • D. 10-3 ?-m
    • Discuss
    • 10. The orientation polarization of a polyatomic gas is inversely proportional to absolute temperature.

    • Options
    • A. True
    • B. False
    • Discuss


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