logo

CuriousTab

CuriousTab

Discussion

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

  • In a TWT the amplitude of resultant wave travelling down the helix


  • Options
  • A. increases exponentially
  • B. increases linearly
  • C. decreases exponentially
  • D. is almost constant

  • Correct Answer
  • increases exponentially 

    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. Assertion (A): Artificial transmission lines are frequently used in laboratories.

      Reason (R): An artificial transmission line can be used to represent an actual line and can also be used as a delay circuit, as attenuator, as filter network etc.


    • 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
    • 2. A quarter wave line open circuited at far end behaves as

    • Options
    • A. inductance
    • B. L and C in parallel
    • C. capacitance
    • D. L and C in series
      • Discuss
    • 3. In a backward wave oscillator the wave travelling along the line winds itself back and forth

    • Options
    • A. True
    • B. False
      • Discuss
    • 4. Skin effect is more pronounced at high frequencies.

    • Options
    • A. True
    • B. False
      • Discuss
    • 5. The reflection coefficient on a line is 0.2 ?45°. The SWR is

    • Options
    • A. 0.8
    • B. 1.1
    • C. 1.2
    • D. 1.5
      • Discuss
    • 6. In a turnstile antenna two-half wave resonant wire radiators are placed at 90° to each other in the same plane and are excited

    • Options
    • A. in phase
    • B. in phase opposition
    • C. 90° out of phase with each other
    • D. 45° out of phase with each other
      • Discuss
    • 7. The frequency of oscillation in a backward wave oscillator can be changed by

    • Options
    • A. varying the voltage which controls beam velocity
    • B. varying the beam current
    • C. both by varying the beam current and by light varying the voltage which controls beam velocity
    • D. changing the rate of thermionic emission
      • Discuss
    • 8. Assertion (A): The impedance of a matched load is equal to characteristic impedance of line.

      Reason (R): A matched termination absorbs all the power incident on it.


    • 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. Which of the following is not a travelling wave?

    • Options
    • A. e = Em sin (?x - ?t)
    • B. e = Em cos (?x - ?t)
    • C. e = Em sin (?t - ?x)
    • D. e = Em sin (?x)
      • Discuss
    • 10. Which of the following parameters is negligible in transmission lines?

    • Options
    • A. R
    • B. L
    • C. C
    • D. G
      • Discuss

    Comments

    There are no comments.
Enter a new Comment




Aptitude

Engineering

Programming

Reasoning

Links

Copyright ©CuriousTab. All rights reserved.