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

  • Assertion (A): The phenomenon of differential mobility is called transferred electron effect.

    Reason (R): GaAs exhibits transferred electron effect.


  • 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 Gunn diode uses GaAs which has a negative differential mobility, i.e., a decrease in carrier velocity with increase in electric field.

    This effects is called transferred electron effect. The impedance of a Gunn diode is tens of ohms.

    A Gunn diode oscillator has a resonant cavity, an arrangement to couple Gunn diode to cavity, biasing arrangement for Gunn diode and arrangement to couple RF power to load.

    Applications of Gunn diode oscillator include continuous wave radar, pulsed radar and microwave receivers.

    Microwave Communication problems

    Search Results

    • 1. VSB modulation is preferred in TV because

    • Options
    • A. it reduces the bandwidth requirement to half
    • B. it avoids phase distortion at low frequencies
    • C. it results in better reception
    • D. none of the above
      • Discuss
    • 2. The range of a cordless telephone is about

    • Options
    • A. 1000 m
    • B. 500 m
    • C. 100 m
    • D. 10 m
      • Discuss
    • 3. Energy content of atmospheric noise

    • Options
    • A. does not depend on frequency
    • B. decreases as frequency is increased
    • C. increases as frequency is increased
    • D. either (a) or (c) depending on the temperature
      • Discuss
    • 4. Non-coherently detection is not possible for

    • Options
    • A. PSK
    • B. ASK
    • C. FSK
    • D. both (a) and (c)
      • Discuss
    • 5. Radio broadcasts are generally

    • Options
    • A. amplitude modulation
    • B. frequency modulation
    • C. both amplitude and frequency modulation
    • D. neither amplitude nor frequency modulation
      • Discuss
    • 6. A line is excited by a 100 V dc source. If reflection coefficients at both ends are 1 each then

    • Options
    • A. there will be no oscillations on line
    • B. there will be only 1 or 2 oscillations on line
    • C. there will be a finite number of oscillations on line
    • D. the oscillations will continue indefinitely
      • Discuss
    • 7. Reflex klystron oscillator is essentially a low power device

    • Options
    • A. True
    • B. False
      • Discuss
    • 8. A resistive microwave load with ZL = 150 ? is connected to 50 ? coaxial line. SWR is

    • Options
    • A. more than 3
    • B. less than 3
    • C. equal to 3
    • D. either (a) or (c)
      • Discuss
    • 9. Assertion (A): A backward wave oscillator has an internal positive feedback.

      Reason (R): A positive feedback is necessary for sustained oscillations.


    • 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
    • 10. The velocity factor of a transmission line depends on

    • Options
    • A. temperature
    • B. skin effect
    • C. relative permittivity of dielectric
    • D. none of the above
      • Discuss

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