Question

Depth of modulation in terms of $E_{max}$ and $E_{min}$ is

• A. $m_a=\frac{E_{max}+E_{min}}{E_{min}}$
• B. $m_a=\frac{E_{max}-E_{min}}{E_{max}}$
• C. $m_a=\frac{E_{max}-E_{min}}{E_{max}+E_{min}}$
• D. $m_a=\frac{E_{max}+E_{min}}{E_{max}-E_{min}}$

Answer 1

The correct option is C $m_a=\frac{E_{max}-E_{min}}{E_{max}+E_{min}}$

The depth of modulation is given by:

$m_a=\frac{E_m}{E_c}$

From, amplitude modulation waveform, it is clear that,

$E_m=\frac{E_{max}-E_{min}}{2}$ .................eq1

and $E_c=E_{max}-E_m$

$E_c=E_{max}-\frac{E_{max}-E_{min}}{2}$

$E_c=\frac{E_{max}+E_{min}}{2}$ ....................eq2,

Dividing eq1 by eq2, we get:

$m_a=\frac{E_m}{E_c}=\frac{E_{max}-E_{min}}{E_{max}+E_{min}}$