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

    Microwave Communication problems

    Search Results

    • 1. The cut off wavelength in circular waveguide

    • Options
    • A. guide diameter
    • B. square of guide diameter
    • C. cube of guide diameter
    • D. square root of guide diameter
      • Discuss
    • 2. The directivity in a receiving antenna

      1. increases the intercept area in forward direction
      2. reduces the noise picked up from other sources
      3. provides a means of discriminating against undesired signals originating in directions other than in which the desired transmitter lies.
      Which of the above statements are correct?

    • Options
    • A. 1 only
    • B. 1 and 2 only
    • C. 1, 2 and 3
    • D. 2 and 3 only
      • Discuss
    • 3. A loss less line is terminated in a circular lines are E lines

    • Options
    • A. SWR = 0
    • B. SWE = 0
    • C. SWR is finite
    • D. SWR = ?
      • Discuss
    • 4. A magnetron has a cylindrical cathode surrounded by an anode structure having cavities opening into interaction space by means of slots

    • Options
    • A. True
    • B. False
      • Discuss
    • 5. For the strip line in the given figure the capacitance per unit length =

    • Options
    • A.
    • B.
    • C.
    • D.
      • Discuss
    • 6. The directive gain of a transmitting antenna is

    • Options
    • A. proportional to wavelength
    • B. inversely proportional to wavelength
    • C. proportional to square of wavelength
    • D. inversely proportional to square of wavelength
      • Discuss
    • 7. A transmission line has Z0 = 300 ? and ZL = (300 - j300) ohm. The transmission coefficient is

    • Options
    • A. 1.265 ? - 18.43°
    • B. 1.01 ? - 10°
    • C. 1.14 ? 66.68°
    • D. 1.09 ? 66.68°
      • Discuss
    • 8. A coaxial line has L = 500 nH/m and C = 50 pF/m. The characteristic impedance is

    • Options
    • A. 500 ?
    • B. 250 ?
    • C. 100 ?
    • D. 50 ?
      • Discuss
    • 9. Assertion (A): A half wavelength line can be used as a 1 : 1 transformer.

      Reason (R): The input impedance of a half wavelength line is equal to load impedance.


    • 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
    • 10. Consider the following statements

      1. Dissipative attenuator has a fixed value of attenuation.
      2. Reflective attenuator has a fixed value of attenuation.
      3. Both dissipative and reflective attenuators are available only with fixed attenuation.
      4. Both dissipative and reflective attenuators are available with either fixed or variable attenuation.
      Which of the above are correct?

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

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