Question

A message signal of frequency $100\text{MHz}$ and peak voltage $100\text{V}$ is used to execute amplitude modulation on a carrier wave of frequency $300\text{GHz}$ and peak voltage $400\text{V}$. The modulation index and difference between the two side band frequencies are :

• A. $0.25;2\times {10}^8\text{Hz}$
• B. $4;1\times {10}^8\text{Hz}$
• C. $4;2\times {10}^8\text{Hz}$
• D. $0.25;1\times {10}^8\text{T}$

Answer 1

The correct option is A $0.25;2\times {10}^8\text{Hz}$

Given:
Signal frequency $=100\text{MHz}$,
Peak voltage $=100\text{V}$,
Carrier wave frequency $=300\text{GHz}$,
Peak voltage of carrier wave $=400\text{V}$,

As we know that,
Range of frequency $=(f_c-f_m)$ to $(f_c+f_m)$

$\therefore$ Band width $=2f_m=2\times 100\times {10}^6\text{Hz}=2\times {10}^8\text{Hz}$

Modulation index $=\frac{A_m}{A_c}=\frac{100}{400}=0.25$

Hence option $\left(C\right)$ is correct.