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Home ‣ Electronics and Communication Engineering ‣ Microwave Communication See What Others Are Saying!
  • Question

  • In a TWT the axial component of electric field advances along the tube


  • Options
  • A. at a velocity that is almost equal to speed of light
  • B. at a velocity that is a small fraction of speed of light
  • C. at a velocity that is about 50% of speed of light
  • D. at a velocity that may be even more than speed of light

  • Correct Answer
  • at a velocity that is a small fraction of speed of light 

    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. Frequency range for satellite communication is

    • Options
    • A. 1 kHz to 100 kHz
    • B. 100 kHz to 10 MHz
    • C. 10 MHz to 100 MHz
    • D. 1 GHz to 30 GHz
      • Discuss
    • 2. To prevent a DC return between source and load, it is necessary to use

    • Options
    • A. resistor between source and load
    • B. inductor between source and load
    • C. capacitor between source and load
    • D. either (a) or (b)
      • Discuss
    • 3. Dielectric constant of transformer oil is about

    • Options
    • A. 1
    • B. 4
    • C. 10
    • D. 20
      • Discuss
    • 4. Which one of the following can be used for amplification of microwave energy?

    • Options
    • A. TWT
    • B. Magnetron
    • C. Reflex klystron
    • D. Gunn diode
      • Discuss
    • 5. Which of the following is wrong for a magic used to tee?

    • Options
    • A. E and H arms are decoupled
    • B. coplanar arms are coupled
    • C. all ports are perfectly matched
    • D. A signal into coplanar arm splits equally between E and H arms
      • Discuss
    • 6. A UJT exhibits negative resistance characteristics when

    • Options
    • A. Current is less than valley current
    • B. Current is less than peak current
    • C. Current is more than peak current but less than valley current
    • D. None of the above
      • Discuss
    • 7. The signal defined by the equations f(t) = 0 for t < 0, f(t) = E for 0 ? t ? a and f(t) = 0 for t > a is

    • Options
    • A. a step function
    • B. a pulse function
    • C. a shifted step function originating at t = a
    • D. none of the above
      • Discuss
    • 8. Which of the following real variable names is not valid in Fortran?

    • Options
    • A. BETA
    • B. ALPHA
    • C. A
    • D. AB * 2
      • Discuss
    • 9. TE10 mode of propagation of electromagnetic energy in waveguides can be thought of as

    • Options
    • A. three TEM waves travelling along length of wave-guide
    • B. One TEM wave travelling along length of wave guide and one TEM wave propagation in the transverse plane
    • C. One TEM wave travelling along the length of wave guide and two TEM waves
    • D. none of the above
      • Discuss
    • 10. In sinusoidal PWM for inverters the width of different pulses are not the same.

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

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