Answer to Question #90171 in Electrical Engineering for Shivam Nishad

Question

Draw the time domain wave forms of AM wave for modulation index Ma = 0 and >1.

Answer 1

The time domain is the representation of the amplitude-modulated (AM) wave called envelope joining the pikes of the unmodulated carrier wave. The modulation index is the amplitude of the modulating signal over amplitude of the carrier signal:

$$M_a=\frac{V_M}{V_C}.$$

Assume that the carrier signal (orange) amplitude is 1. Then, in case of $M_a=0$, the modulating signal amplitude is 0 (blue) and it looks like this:

Consider an overmodulated signal with the modulation index more than 1, assume it is 1.5. In this case the amplitude of the modulating signal (blue) is 1.5, and relatively to the carrier signal (i.e. with regard to 1) the modulating signal will vary from 1.5 to -1.5: