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  • Question

  • In a travelling wave tube distributed interaction between an electron beam and a travelling wave takes place


  • Options
  • A. True
  • B. False

  • Correct Answer
  • True 

    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.

    Microwave Communication problems

    Search Results

    • 1. In a circular waveguide the dominant mode is

    • Options
    • A. TE01
    • B. TE11
    • C. TE20
    • D. TE21
      • Discuss
    • 2. The diagram to show distance time history of electrons in klystron amplifier is called

    • Options
    • A. apple gate diagram
    • B. asynchronous diagram
    • C. bunching diagram
    • D. velocity modulation diagram
      • Discuss
    • 3. A line has a phase constant of 29.8 rad/m. At 1000 MHz the wavelength is

    • Options
    • A. 29.8 m
    • B. 2.98 m
    • C. 2.1 m
    • D. 0.21 m
      • Discuss
    • 4. The velocity factor of a transmission line depends on

    • Options
    • A. temperature
    • B. skin effect
    • C. relative permittivity of dielectric
    • D. none of the above
      • Discuss
    • 5. Assertion (A): A backward wave oscillator has an internal positive feedback.

      Reason (R): A positive feedback is necessary for sustained oscillations.


    • 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
    • 6. In a klystron amplifier dc electron velocity is v0 and dc electron charge density is r0 the dc beam current is

    • Options
    • A. r0v0
    • B. r0/v0
    • C. v0/r0
    • D. (v0/r0)2
      • Discuss
    • 7. Assertion (A): A coaxial line is a non-radiating line.

      Reason (R): In a coaxial line the electric and magnetic fields are confined to the region between the concentric conductors.


    • 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
    • 8. A loss less line of characteristic impedance Z0 is terminated in pure reactance of -jZ0 value. VSWR is

    • Options
    • A. 10
    • B. 2
    • C. 1
    • D. infinity
      • Discuss
    • 9. In a directional coupler

    • Options
    • A. isolation (dB) equals coupling plus directivity
    • B. coupling (dB) equals isolation plus directivity
    • C. directivity (dB) equals isolation plus coupling
    • D. isolation (dB) equals (coupling) (directivity)
      • Discuss
    • 10. The action of backward wave oscillator is similar to that of

    • Options
    • A. klystron amplifier
    • B. reflex klystron oscillator
    • C. TWT
    • D. magnetron
      • Discuss

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