Define the terms ‘modulation index’ for an AM wave. What would be the modulation index for an AM wave for which the maximum amplitude is ‘a’ and the minimum amplitude is ‘b’?

The Modulation Index for amplitude can be defined as the measure of the extent by which the amplitude varies about an unmodulated carrier.

It is expressed as,



Am=Amplitude of modulating wave, Ac=Amplitude of Carrier wave


If a is maximum modulation then,



if b is minimum modulation then,



So,



So,



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