11. The front end of an amplifier chain in a microwave communication system is kept immersed in liquid nitrogen to:
    

1. 1. Dissipate heat generated by amplifier
      
      

   
   
   

   2. Expand its noise figure
      

   
   
   

   3. Improve its noise figure
      

   
   
   

   4. Reduce the distortion produced by the amplifier

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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12. In a rectangular waveguide there is one half-wave variation of electric field across the narrow dimension and two half-wave variations of electric field across the wider dimension. What is dominant mode?
    

1. 1. TM₁₂
      

   
   
   

   2. TE₂₁
      

   
   
   

   3. TE₁₂
      

   
   
   

   4. TM₂₁
      

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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13. Which one of the following is a transferred electron device?
    

1. 1. BARITT diode
      

   
   
   

   2. IMPATT diode
      

   
   
   

   3. Gunn diode
      

   
   
   

   4. Step recovery diode

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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14. The kinetic energy of the beam remains uncharged in the interaction between an electron beam and RF wave in a:
    

1. 1. Multi-cavity klystron
      

   
   
   

   2. Crossed field amplifier
      

   
   
   

   3. Travelling-wave tube
      

   
   
   

   4. Gyrotron

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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15. The slow-wave structure of TWT is provided with an attenuator. Which one of the following is the function of such an attenuator?
    

1. 1. It prevents the RF power from reaching the output of the device when the beam is switched on
      

   
   
   

   2. It prevents oscillations in the device
      

   
   
   

   3. It reduces the noise level of the device
      

   
   
   

   4. It is used to broadband the device

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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