If fm is the modulation frequency in FM, the modulation index

• Communication Systems

If f_m is the modulation frequency in FM, the modulation index is proportional to

1. f_m
2. 1/f_m²
3. f_m²
4. 1/f_m

Answer

The value of the modulation index indicates by how much the modulated variable varies around its unmodulated level. It relates to variations in the carrier frequency:

h = Δf/f_m

where f_m is the modulation frequency and Δf is the frequency deviation.

The correct option is D.