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  • Question

  • Assertion (A): PIN diode can be used as attenuator and limiter.

    Reason (R): PIN diode has a thin intrinsic layer.


  • 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

  • Correct Answer
  • Both A and R are correct but R is not correct explanation of A 

    Explanation
    A PIN diode has an intrinsic (i) layer between p and n layers. When reverse bias is applied depletion layers are formed at p-i and i-n junctions.

    The effective/width of depletion layer increases by the width of i layer. It can be used as a voltage controlled attenuator.

    At high frequencies the rectification effect ceases and impedance of diode is effectively that of i layer.

    This impedance varies with the applied bias. It is used in high frequency switching circuits, limiters, modulators etc.

    Microwave Communication problems

    Search Results

    • 1. In Reflex Klystron oscillator the focussing electrode is at a high potential

    • Options
    • A. True
    • B. False
      • Discuss
    • 2. If other parameter are constant, transmission loss at 5 GHz as compared to that at 0.5 GHz is

    • Options
    • A. 20 dB more
    • B. 20 dB less
    • C. 700 dB more
    • D. 100 dB less
      • Discuss
    • 3. In the given figure the reflected voltage wave after first reflection is

    • Options
    • A. 18 V
    • B. -18 V
    • C. 30 V
    • D. -30 V
      • Discuss
    • 4. A quarter wave line short circuited at load end behaves as

    • Options
    • A. an inductance
    • B. an inductance and capacitance in series
    • C. a capacitance
    • D. an inductance and capacitance in parallel
      • Discuss
    • 5. Assertion (A): A line of length and short circuited at far end has an input impedance of infinity.

      Reason (R): A line of length and short circuited at far end behaves as a parallel resonant circuit.


    • 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
    • 6. For the strip line in the given figure the capacitance per unit length =

    • Options
    • A.
    • B.
    • C.
    • D.
      • Discuss
    • 7. 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
    • 8. 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
    • 9. 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
    • 10. 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

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