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Question: Answered & Verified by Expert
An amplitude modulated wave is as shown in figure. Calculate
(i) the percentage modulation,
(ii) peak carrier voltage and
(iii) peak value of information voltage

PhysicsCommunication System
Solution:
2724 Upvotes Verified Answer
As the given diagram,
$$
\begin{aligned}
&\text { Maximum voltage } \mathrm{V}_{\max }=\frac{100}{2}=50 \mathrm{~V} \\
&\text { Minimum voltage } \mathrm{V}_{\min }=\frac{20}{2}=10 \mathrm{~V}
\end{aligned}
$$
(i) Percentage of modulation, $m$
$$
\begin{aligned}
&=\left(\frac{\mathrm{V}_{\max }-\mathrm{V}_{\min }}{\mathrm{V}_{\max }+\mathrm{V}_{\min }}\right) \times 100=\left(\frac{50-10}{50+10}\right) \times 100 \\
&=\frac{40}{60} \times 100=66.67 \%
\end{aligned}
$$
(ii) Peak carrier voltage,
$$
\mathrm{V}_{\mathrm{o}}=\frac{\mathrm{V}_{\max }+\mathrm{V}_{\min }}{2}=\frac{50+10}{2}=30 \mathrm{~V}
$$
(iii) Peak value of information voltage,
$$
\begin{aligned}
\mathrm{V}_{\mathrm{om}} &=\mathrm{mV}_{\mathrm{oc}} \\
&=\frac{66.67}{100} \times 30=20 \mathrm{~V}
\end{aligned}
$$

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