InterviewSolution
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InterviewSolution
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An audio signal is modulated by a carrier wave of 20 MHz such that the bandwidth required for modulation is 3 kHz. Could this wave be demodulated by a diode detector which has the values of R and C as (i) `R = 1 k Omega, C = 0.01 mu F (ii) R = 10 k Omega, C = 0.01 muF (iii) R = 10k Omega , C = 1 mu muF`.A. `R=1kOmega,C=0.01muE`B. `R=10kOmega,C=0.01muF`C. `R=10kOmega,C=0.1pF`D. None of these |
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Answer» Correct Answer - A `v_(c)=20MHz=20xx10^(6)Hz` `(1)/(v_(c))=(1)/(20)xx10^(-6)=0.05xx10^(-6)=0.5xx10^(-7)s` Band width =`20_(m)=3kHz=3xx10^(3)Hz` `v_(m)=1.5xx10^(3)Hz` `(1)/(v_(m))=(1)/(1.5)xx10^(-3)=0.7xx10^(-3)s`. Diode detector can demodulate when `(1)/(v_(c))ltltRCltlt(1)/(v_(m))` (i)RC=`1kOmegaxx0.01muF=10^(3)xx(0.01xx10^(-6))=10^(-5)s`. it can be demodulated. (ii) RC=`10kOmegaxx1xx10^(-8)=10^(-4)s` It can be demodulated (iii) RC`=10kOmegaxx1pF=10^(4)xx10^(-12)=10^(-8)s` It cannot be demodulated. |
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