91. Two perfect 4-port circulators are cascaded, as shown in fig. to form a 6-port circulator.
    Transmitter (T), receiver (R) antenna (A) and match load (L) are connected to these ports. Which one of the following interconnection schemes is correct?
    
    
    

1. 1. T  R  A   L
      4  5  6   1,2,3

   
   
   

   2. T  R  A   L
      3  5  6   1,2,4

   
   
   

   3. T  R  A   L
      2  3  4   1,5,6

   
   
   

   4. T  R  A   L
      1  3  2   ;4,5,6

   
   
   

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   NA

   Correct Option: A

   NA

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92. Match list-I with list-II and select the correct answer using the codes given below the lists:

    List-I (Microwave Devices)	List-II (Applications)
    A. Reflex klystron	1. Wide band amplification
    B. TWT	2. Very low level amplification
    C. 2-Cavity klystron	3. Low power FM generation
    D. Maser	4. Frequency multiplication

1. 1. A B C D
      1 2 3 4
      

   
   
   

   2. A B C D
      4 3 2 1
      

   
   
   

   3. A B C D
      3 4 1 2
      

   
   
   

   4. A B C D
      3 1 4 2
      

   
   
   

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   NA

   Correct Option: D

   NA

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93. (A) The TW tube which is a wideband microwave amplifier of the helix is used as a slow wave structure of the device.
    (R) The phase velocity of the helix can be profiled along the length of the helix.

1. 1. Both A and R are true and R is correct explanation of A

   
   
   

   2. Both A and R are true but R is not a correct explanation of A

   
   
   

   3. A is true but R is false

   
   
   

   4. A is false but R is true

   
   
   

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   NA

   Correct Option: A

   NA

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94. (A) The variables choosen for the equivalent circuit of a 2 port network in the microwave range of frequencies are travelling waves rather than total voltage and total currents.
    (R) In microwave range equipment is not readily available to measure total voltage and total currents at the ports of the networks. Short and open circuits are difficult to achieve over a broad-band of frequencies and active devices frequently will not have stability for a short or open circuit.

1. 1. Both A and R are true and R is correct explanation of A

   
   
   

   2. Both A and R are true but R is not a correct explanation of A

   
   
   

   3. A is true but R is false

   
   
   

   4. A is false but R is true
      

   
   
   

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   NA

   Correct Option: A

   NA

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95. (A) In some applications, the TM01 mode in circular waveguide is preferred to the TE01 mode or TE11 mode.
    (R) TM01 mode not only overcomes the problem of rotation of polarisation in circular waveguide but also requires a smaller diameter.

1. 1. Both A and R are true and R is correct explanation of A

   
   
   

   2. Both A and R are true but R is not a correct explanation of A

   
   
   

   3. A is true but R is false

   
   
   

   4. A is false but R is true

   
   
   

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   NA

   Correct Option: A

   NA

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