In amplitude modulation, the modulation index mu, is kept less than or equal to 1 because.

Options

A. `m gt 1`, will result in interference between carrier frequency and message frequency, resulting into distortion
B. `m gt 1`, will result in overlapping of both side bands resulting into loss of information
C. `m gt 1`, will result in change in phase between carrier signal and message signal
D. `m gt 1`, indicates amplitude of message signal greater than amplitude of carrier signal resulting into distortion

Answer

B, D

Explanation

The modulation index (m) of amplitude modulated wave is
`m=("amplitude of message signal"(A_(m)))/("amplitude of carrier signal"(A_(c )))`
If `m gt 1`, then `A_(m) gt A_(c )`.
In this situation, there will be distortion of the resulting signal of amplitude modulated wave. Maximum modulation frequency `(m_(f))` of `A_(m)` wave is
`m_(f) = (Deltav_("max"))/(v_(m)("max"))`
`=("frequency deviation")/("maximum frequency value of modulating wave")`
If `m_(f) gt 1`, then `Deltav_("max")gt v_(m)`. It means, there will be overlapping of both side bands of modulated wave resulting into loss of information.