Question

The modulation index $\mu $ in amplitude modulating wave is:
A.$\mu < 1$
B. $\mu > 1$
C. $\mu \geqslant 1$
D. $\mu \leqslant 1$

Answer 1

Hint: As we all know that a baseband message signal is the continuous wave which needs to be modulated. This wave has no intervals and it carries a message signal and on the other hand the carrier wave has no signal.

Complete step by step answer:
We can see that If the amplitude of the low frequency wave is increased, then it its known as amplitude modulation. The modulation index describes the relation between amplitude of the message signal and the amplitude of the carrier wave. It is basically the ratio of amplitude of the message signal and the amplitude of the carrier wave. So we can express the relation of modulation index $\mu $ as:
$\mu = \dfrac{{{A_m}}}{{{A_c}}}$
We come to know that here ${A_m}$ is the amplitude of the message signal wave and ${A_c}$ is the amplitude of the carrier wave. We also know that the amplitude of a carrier wave is always greater than the amplitude of a message signal wave.
Now let’s suppose if amplitude of the carrier wave is not more than the amplitude of the message wave then the signal of the modulated wave would be distorted means when a message signal is modulated then many other frequencies also get generated and they start overlapping and the signal is distorted so if $\mu > 1$, it will result in overlapping of sidebands which results into loss of information.

So, the correct answer is “Option A”.

Note:
As we all know that the positive and negative peaks in the carrier wave are interconnected with an imaginary line. So this line helps in recreating the exact shape of the modulating signal. This imaginary line on the carrier wave is known as Envelope. It is analogous as that of the message signal.