JEE Main & Advanced Physics Communication System / संचार तंत्र Question Bank Critical Thinking

  • question_answer
    An amplitude modulated wave is modulated to 50%. What is the saving in power if carrier as well as one of the side bands are suppressed

    A)            70%                                          

    B)            65.4%

    C)            94.4%                                      

    D)            25.5%

    Correct Answer: C

    Solution :

                       \[{{P}_{sb}}={{P}_{c}}\,{{\left( \frac{{{m}_{a}}}{2} \right)}^{2}}={{P}_{c}}\frac{{{(0.5)}^{2}}}{4}=0.0625\,{{P}_{c}}\] Also \[P={{P}_{c}}\,\left( 1+\frac{m_{a}^{2}}{2} \right)={{P}_{c}}\,\left( 1+\frac{{{(0.5)}^{2}}}{2} \right)=1.125{{P}_{c}}\] \ % saving\[=\frac{(1.125{{P}_{c}}-0.0625{{P}_{c}})}{1.125{{P}_{c}}}\times 100=94.4%.\]


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