Question

What is the effect of increasing modulation index in FM?

Answer 1

Hint: In order to solve this question, we should know that FM stands for Frequency Modulation and In Frequency modulation the frequency of the carrier wave is changed to encode the signal information with respect to the modulation wave. Here we will discuss the effect of increasing the modulation index in FM.

Complete step by step solution:
As we know, the Modulation index is the ratio of frequency deviation to the modulating frequency. and the Bandwidth which is defined as the range of frequencies that are used for a particular kind of signal transmission and it’s different for different types of signals.

Now, the bandwidth B.W of Frequency modulation F.M is related to modulation index and modulating frequency as,
$B.W = 2(\beta + 1){f_m}$
where, $\beta ,{f_m}$ denotes for modulation index and modulation frequency so, from the relation we can see that bandwidth of FM is directly related to modulation index.

Hence, when the modulation index increases the Bandwidth of FM also increases, and when the modulation index decreases the Bandwidth of FM also decreases.

Note: It should be remembered that In the case of Amplitude Modulation A.M the Bandwidth is independent of the modulation index, it only depends upon maximum modulating frequency and its mathematical relation is $B.W = 2{f_m}$.