Question

What is the effect of increasing modulation index in FM?

Answer 1

The effect of increasing modulation index in FM

1. Modulation index means the ratio of the fundamental component amplitude of the line to the neutral inverter output voltage to one-half of the available DC bus voltage.
2. The number of significant sidebands increases as the modulation index for frequency modulation (FM) increases, but the total average power of the sidebands remains constant.
3. A higher modulation index for FM means increased modulation depth, which necessitates additional bandwidth for transmission. The maximum modulating frequency and modulation index affect the efficiency and bandwidth of FM transmissions.
4. Over-modulation occurs when the modulation level exceeds a modulation index of one, i.e. greater than $100\%$ modulation. The carrier undergoes $180°$ phase reversals in which the carrier level attempts to go below zero.