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Home  >>  JEEMAIN and NEET  >>  Physics  >>  Class12  >>  Communication Systems

A transmitter puts out a total power of 25 Watts of 30% AM signal. Calculate how much power is contained in each of the sidebands and the fraction of power in the carrier.

1 Answer

The total power in an AM signal when the carrier power and the percentage of modulation are known is $P_T = P_c \big ( 1 + \large\frac{m^2}{2}$$\big )$
$\Rightarrow 25 = P_c \big ( 1 + \large\frac{0.3^2}{2}$$\big )$
$\Rightarrow P_c = \large\frac{25}{1.045}$$ = 23.92\;W$
The total power in both side bands $ = 25 - 23.92 = 1.08\;W$
The power in each side band is half of this $ = 0.54\;W$
$\Rightarrow$ The fraction of the power in the carrier is $\large\frac{23.92}{25} $$= 0.957$
answered Jul 12, 2014 by balaji.thirumalai
 

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