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Q.
In amplitude modulation, the modulation index $m$, is kept less than or equal to 1 because
Communication Systems
Solution:
The modulation index $(m)$ of amplitude modulated wave is
$m=\frac{\text { amplitude of message signal }\left(A_{m}\right)}{\text { amplitude of carrier signal }\left(A_{c}\right)}$
If $m > 1$, then $A_{m} > A_{c}$. In this situation, there will be distortion of the resulting signal of amplitude modulated wave. Maximum modulation frequency $\left(m_{f}\right)$ of $A M$ wave is
$m_{f} =\frac{\Delta v_{\max }}{v_{m(\max )}} $
$=\frac{\text { frequency deviation }}{\text { maximumfrequency value of modulating wave }}$
If $m_{f} > 1$, then $\Delta v_{\max } > v_{m}$. It means, there will be overlapping of both side bands of modulated wave resulting into loss of information.