logo

CuriousTab

CuriousTab

Discussion

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

    More questions

    • 1. The problem associated with tuned-radio frequency receiver is

    • Options
    • A. instability
    • B. insufficient adjacent frequency rejection
    • C. bandwidth variation
    • D. all of the above
      • Discuss
    • 2. Which one of the following is not a useful quantity for comparing the noise performance of receivers?

    • Options
    • A. Noise figure
    • B. Noise temperature
    • C. Input noise voltage
    • D. Equivalent noise resistance
      • Discuss
    • 3. To study electromagnetic radiations from astronomical objects, radio astronomers use

    • Options
    • A. low frequencies
    • B. medium frequencies
    • C. microwaves
    • D. either (a) or (b)
      • Discuss
    • 4. Figure shows an RC potentiometer to measure ac voltage. It is desired that V0/Vi should be independent of frequency. The value of C should be

    • Options
    • A. 10 ?F
    • B. 11 ?F
    • C. 0.1 ?F
    • D. 0.09 ?F
      • Discuss
    • 5. Assertion (A): An amorphous material is obtained when mobility of atoms is inhibited during solidification.

      Reason (R): Crystalline state is a natural state for most solids.


    • Options
    • A. Both A and R are true and R is correct explanation of A
    • B. Both A and R are true but R is not correct explanation of A
    • C. A is true but R is false
    • D. A is false but R is true
      • Discuss
    • 6. Match the following:

      List I (Controller) List II (Controller output for unit step input)
      A. Proportional derivative 1.
      B. Proportional plus derivative plus integral 2.
      C. Proportional plus 3.


    • Options
    • A. A-1, B-2, C-3
    • B. A-1, B-3, C-2
    • C. A-3, B-2, C-1
    • D. A-2, B-3, C-1
      • Discuss
    • 7. As frequency is increased, the skin effect

    • Options
    • A. increases
    • B. decreases
    • C. remains the same
    • D. either (b) or (c)
      • Discuss
    • 8. In a controlled rectifier a freewheeling diode is necessary if the load is

    • Options
    • A. inductive
    • B. resistive
    • C. capacitive
    • D. any of the above
      • Discuss
    • 9. A parallel plate capacitor having C = 200 x 10-12 F has loss dielectric having tan ? = 4 x 10-4. At an ac voltage of f = 106 Hz and peak value 2 V, the dielectric losses are

    • Options
    • A. 10-8 W
    • B. 10-6 W
    • C. 10-4 W
    • D. 10-2 W
      • Discuss
    • 10. A full adder can be made out of

    • Options
    • A. two half adders
    • B. two half adders and a OR gate
    • C. two half adders and a NOT gate
    • D. three half adders
      • Discuss

    Comments

    There are no comments.
Enter a new Comment




Aptitude

Engineering

Programming

Reasoning

Links

Copyright ©CuriousTab. All rights reserved.