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

  • The electric field in a TWT due to applied signal


  • Options
  • A. is directed along the helix axis
  • B. is directed radially from helix axis
  • C. is inclined to the helix axis by about 60°
  • D. is inclined to the helix axis by about 45°

  • Correct Answer
  • is directed along the helix axis 

    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. Varactor diodes use

    • Options
    • A. silicon
    • B. GaAs
    • C. either (a) or (b)
    • D. neither (a) nor (b)
      • Discuss
    • 2. If load impedance ZL >> Z0, then

    • Options
    • A. Z0 = ZL (VSWR)
    • B. ZL = Z0 (VSWR)
    • C. ZL = Z0 (VSWR - 1)
    • D. ZL = Z0 VSWR
      • Discuss
    • 3. In a line with finite attenuation

    • Options
    • A. power transmission is least efficient when there are no standing waves on the line
    • B. power transmission is most efficient when there are no standing waves on line
    • C. Load power depends on phase constant
    • D. standing waves will always exist on the line
      • Discuss
    • 4. In a klystron amplifier the force on all electrons

    • Options
    • A. causes acceleration of all electrons
    • B. causes retardation of all electrons
    • C. causes acceleration of some electrons and retardation of others
    • D. none of the above
      • Discuss
    • 5. The number of PM radio channels which can be accommodated in a spectrum of 300 MHz is about

    • Options
    • A. 10
    • B. 100
    • C. 500
    • D. 1500
      • Discuss
    • 6. The radiation resistance of a circular loop of one turn is 0.01 ohm. For 5 turn loop the radiation resistance is

    • Options
    • A. 0.002 ?
    • B. 0.01 ?
    • C. 0.05 ?
    • D. 0.25 ?
      • Discuss
    • 7. In a klystron amplifier the bunching effect

    • Options
    • A. converts velocity modulation into current modulation of beam
    • B. converts current modulation into velocity modulation of beam
    • C. both (c) and (b)
    • D. neither (a) nor (b)
      • Discuss
    • 8. Assertion (A): Impatt diode is an avalanche diode.

      Reason (R): Avalanche breakdown phenomenon occurs when a p-n junction is reverse biased.


    • 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
    • 9. A TE10 rectangular waveguide is to be designed for operation over 25-35 GHz and the band centre is 1.5 times the cutoff frequency. The dimension of broadside is

    • Options
    • A. 15 mm
    • B. 10 mm
    • C. 9 mm
    • D. 7.5 mm
      • Discuss
    • 10. In the given figure a short circuited transmission line resonator If n = 1, 2, 3...

    • Options
    • A. For series reasonance ?l = np and for parallel resonance
    • B. For series resonance and for parallel resonance ?l = np
    • C. ?l = np for both series and parallel resonance
    • D. for both series and parallel resonance
      • Discuss

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