In frequency modulation, what happens to the RF frequency?

In frequency modulation (FM), the key characteristic is that the RF frequency varies continuously in response to the amplitude of the modulating signal. This modulation process means that the frequency of the carrier wave repeatedly increases and decreases, creating a dynamic signal that represents the information being transmitted. Unlike amplitude modulation, where the amplitude of the carrier wave changes while the frequency remains constant, FM allows for richer signal information through these continuous frequency variations.

The continuous nature of these variations is what enables FM to produce higher fidelity and resilience to noise compared to other modulation forms, making it widely used in audio broadcasting and two-way radio communications. This behavior illustrates the fundamental principle of FM, which relies on modulating the frequency around a central value, effectively capturing the input signal's nuances throughout its transmission.