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Home Electronics and Communication Engineering Microwave Communication Comments

  • Question
  • In a klystron amplifier the input cavity is called


  • Options
  • A. buncher
  • B. catcher
  • C. Pierce gun
  • D. collector

  • Correct Answer
  • buncher 

    Explanation
    A Klystron is a vacuum tube used for generation/amplification of microwaves.

    An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode.

    This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher.

    As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle.

    Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation.

    The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam.

    The input is fed at buncher cavity and output is taken at catcher cavity.

    In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used.

    The features of a multicavity klystron are :

    1. Frequency range - 0.25 GHz to 100 GHz

    2. Power output - 10 kW to several hundred kW

    3. Power gain - 60 dB (nominal value)

    4. Efficiency - about 40%.

    A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.


    Microwave Communication problems


    Search Results


    • 1. Microwave resonators are used in

    • Options
    • A. microwave oscillators
    • B. microwave narrow band amplifier
    • C. microwave frequency metres
    • D. all of the above
    • Discuss
    • 2. A 10 km long line has a characteristic impedance of 400 ohms. If line length is 100 km, the characteristic impedance is

    • Options
    • A. 4000 ?
    • B. 400 ?
    • C. 40 ?
    • D. 4 ?
    • Discuss
    • 3. A line has Z0 = 300 ? 0° ?. If ZL = 150 ? 0° ?, reflection coefficient is

    • Options
    • A. 0.5
    • B. 0.3333
    • C. -0.3333
    • D. -0.5
    • Discuss
    • 4. As the frequency is increased, the charging MVAR in a cable

    • Options
    • A. decreases
    • B. increases
    • C. remain the same
    • D. decreases or remains the scheme
    • Discuss
    • 5. Which of the following lines is non-radiating?

    • Options
    • A. Open two wire
    • B. Coaxial
    • C. Both
    • D. None of the above
    • Discuss
    • 6. Assertion (A): TWT uses a focussing mechanism to prevent the electron beam from spreading.

      Reason (R): In a TWT the electron beam has to travel a much longer distance than in klystron.


    • 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
    • 7. For a 50 ? resistor for 3 GHz application, the stray capacitance should be less than

    • Options
    • A. 1 ?F
    • B. 1 nF
    • C. 1 pF
    • D. 0.1 pF
    • Discuss
    • 8. Which of the following devices uses a slow wave structure?

    • Options
    • A. Klystron two cavity amplifier
    • B. Klystron multicavity amplifier
    • C. Reflex klystron oscillator
    • D. TWT
    • Discuss
    • 9. Which of the following can be accessed only sequentially?

    • Options
    • A. Floppy disk
    • B. Hard disk
    • C. Magnetic tape
    • D. ROM
    • Discuss
    • 10. In ALU 1C 74181 the addition and subtraction is in

    • Options
    • A. 2's complement
    • B. 1's complement
    • C. binary
    • D. none of the above
    • Discuss


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