Question

The ratio of $E_{max}-E_{min}$ to $E_{max}+E_{min}$ is known as

• A. Range of modulating signal
• B. Amplitude variation of modulating signal
• C. Depth of modulation
• D. Frequency of modulation

Answer 1

The correct option is C Depth of modulation

The two sideband components have equal amplitudes, which are proportional to the amplitude of the modulating signal. Given figure shows the carrier and sideband components of the amplitude-modulated wave of figure below it as they appear in the frequency domain (amplitude versus frequency).
A measure of the degree of modulation is $m$, the modulation index. This is usually expressed as a percentage called the percent modulation. In the time domain, the degree of modulation for sinusoidal modulation is calculated as follows:
$m=\frac{E_{max}-E_C}{E_C}$
Since, the modulation is symmetrical, we get

$E_{max}-E_C=E_C-E_{max}$

and

$\frac{E_{max}+Emin}{2}=E_C$

Thus, we get

$m=\frac{E_{max}-E_{min}}{E_{max}+E_{min}}$