What is the modulation index in frequency modulation?

The modulation index in frequency modulation (FM) refers to the measure of frequency variation of the carrier wave. It quantifies how much the frequency of the carrier signal deviates from its unmodulated frequency in response to the input signal. Specifically, the modulation index is defined as the ratio of the frequency deviation (the maximum amount the carrier frequency shifts) to the frequency of the modulating signal.

This parameter is crucial because it directly impacts the bandwidth of the FM signal. A higher modulation index results in a greater deviation of the carrier frequency, leading to a wider bandwidth necessary to accommodate the frequency variations. The modulation index also influences the quality and fidelity of the transmitted signal, as it affects how the information is embedded into the carrier wave.

While other options mention measures such as bandwidth, signal strength, and data transmission speed, these do not specifically connect to the concept of frequency modulation as closely as the modulation index does when discussing the frequency variations of the carrier wave itself.