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ECE :: Microwave Communication

  1. If a short line is terminated in characteristic impedance it behaves as an infinite line.

  2. A.
    True
    B.
    False

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  3. Ga As exhibits negative differential mobility

  4. A.
    True
    B.
    False

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  5. Consider the following statements

    1. Bunching of electrons occurs in two cavity klystron amplifier.
    2. Bunching of electrons occurs in multi cavity klystron amplifier.
    3. Bunching of electrons occurs in reflex cavity klystron amplifier.
    Which of the above statements are correct?

  6. A.
    1, 2, and only
    B.
    1, 2 and 3 only
    C.
    1 and 3 only
    D.
    2 and 3 only

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  7. Assertion (A): For high frequency lines inductive reactance is very high as compared to ac resistance.

    Reason (R): Due to skin effect ac resistance of line is higher than dc resistance.

  8. 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

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  9. Consider the following applications

    1. Switch
    2. Attenuator
    3. Phase shifter
    4. Oscillator
    In which of the above can a PIN diode be used?

  10. A.
    1 2 3 and 4
    B.
    1 2 and 3 only
    C.
    1 and 2 only
    D.
    2, 3 and 4 only

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  11. Which one of the following is not a negative resistance device?

  12. A.
    Gunn diode
    B.
    Tunnel diode
    C.
    Impatt diode
    D.
    Varactor diode

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  13. Microwave links are typically 50 km apart

  14. A.
    because of atmospheric attenuation
    B.
    because of output tube power limitation
    C.
    because of earth's curvature
    D.
    to ensure that applied dc voltage is not excessive

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  15. For matching over a range of frequencies in a transmission line it is best to use

  16. A.
    a balun
    B.
    a broad band directional coupler
    C.
    double stub
    D.
    a single stub of adjustable position

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  17. Assertion (A): In the interaction region of magnetron an electron is subjected to three forces: force due to electric field, force due to magnetic field and centrifugal force.

    Reason (R): The mechanism of generation of microwaves, in a magnetron, involves interaction of electromagnetic fields with electrons moving in static electric and magnetic fields oriented at right angles to each other.

  18. 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

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  19. Which of the following is wrong for a magic used to tee?

  20. A.
    E and H arms are decoupled
    B.
    coplanar arms are coupled
    C.
    all ports are perfectly matched
    D.
    A signal into coplanar arm splits equally between E and H arms

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