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  • Question

  • Read the following statements about TWT

    1. It uses thermionic emission.
    2. It uses an attenuater.
    3. It is inherently a resonant device.
    4. It has broad bandwidth.
    Which of the above are correct?


  • Options
  • A. 1, 2, 3 and 4
  • B. 1, 2 and 3
  • C. 1, 3 and 4
  • D. 1, 2 and 4

  • Correct Answer
  • 1, 2 and 4 

    Explanation
    In a klystron the resonant structure limits the bandwidth.

    A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave.

    The velocity of wave propagation along the helix structure is less than velocity of light.

    The beam and wave travel along the structure at the same speed.

    Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave.

    Therefore the signal gets strengthened and amplified output is delivered at the other end of tube.

    The main features of TWT are :

    1. Frequency range - 0.5 GHz to 90 GHz

    2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz

    3. Efficiency - about 5 to 20%

    4. Noise - about 5 dB for low power TWT 25 dB for high power TWT

    TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.

    More questions

    • 1. A radar has a maximum range of 120 km. The maximum allowable pulse repetition frequency for unambiguous reception is

    • Options
    • A. 1250
    • B. 330
    • C. 2500
    • D. 8330
      • Discuss
    • 2. An unmodulated voltage 10 V effective is applied to a dioxide detector in which load resistance is 4 x 10-5 ohms. A micrometer shows that the rectified DC current in this resistance is 30 A. The input resistance of the detector is

    • Options
    • A. 114 kW
    • B. 336 kW
    • C. 384 kW
    • D. 455 kW
      • Discuss
    • 3. For a BJT a = 0.98, then ? =

    • Options
    • A. 0.02
    • B. 0.5
    • C. 4.9
    • D. 48
      • Discuss
    • 4. If the temperature of an extrinsic semiconductor is increased so that the intrinsic carrier concentration is doubled, then

    • Options
    • A. the majority carrier density is doubled
    • B. the minority carrier density is doubled
    • C. the minority carrier density becomes 4 times the original value
    • D. both the majority and minority carrier densities double
      • Discuss
    • 5. A cycloconverter is

    • Options
    • A. ac-dc converter
    • B. dc-ac converter
    • C. dc-dc converter
    • D. ac-ac converter
      • Discuss
    • 6. Consider the following DO statement in Fortran 77

      DO 52 N = 1, 10, 3

      The number of DO loop executions in the above statement is

    • Options
    • A. 1
    • B. 10
    • C. 3
    • D. 4
      • Discuss
    • 7. In a single phase semiconverter feeding a highly inductive load, the load current is

    • Options
    • A. sinusoidal
    • B. nearly constant
    • C. absolutely constant
    • D. rectangular
      • Discuss
    • 8. If ton and toff are the turn on and turn off times of a thyristor, then

    • Options
    • A. ton and toff are almost equal
    • B. ton >> toff
    • C. toff >> ton
    • D. ton is about twice toff
      • Discuss
    • 9. Which inverter circuit uses coupled inductors?

    • Options
    • A. Modified McMurray full bridge inverter
    • B. McMurray Bedford half bridge inverter
    • C. Modified McMurray Bedford half bridge inverter
    • D. Both (b) and (c)
      • Discuss
    • 10. If there are no permanent dipoles in a dielectric material, the dielectric constant is independent of temperature.

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

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