Modulation index

The modulation index (or modulation depth) of a modulation scheme describes by how much the modulated variable of the carrier signal varies around its unmodulated level. It is defined differently in each modulation scheme. See:

This disambiguation page lists articles associated with the title Modulation index.
If an internal link led you here, you may wish to change the link to point directly to the intended article.

if we visualize that some distortion will occur if Em > Ec.

                 the relationship between ampls. of m(t) and c(t) is known as modulation co-officent or degree of modulation.

m=Em/Ec it should be always <1