Question

In the equation, 20cos⁡(10^8 t + 3 sin⁡10^9 t) the modulation index is ________

(a) 1

(b) 2

(c) 3

(d) 4

The question was posed to me by my school principal while I was bunking the class.

Question is taken from Representation of SSB-SC in Time & Frequency Domain in division SSB Modulation of Analog Communications

Answer 1

The correct option is (c) 3

To explain: The general expression for FM is as follows:

FM (t) = Ac sin (2πfct + βsin(2πfmt)), where β is the modulation index.

Thus β = 3.