In frequency modulation, what is necessary to maintain a stable carrier frequency?

In frequency modulation (FM), maintaining a stable carrier frequency is crucial for effective signal transmission and to prevent distortion. Automatic Frequency Control (AFC) is an essential system used to ensure that the carrier frequency remains stable despite variations in frequency due to factors such as temperature changes or component aging. AFC continually monitors the output frequency and adjusts it back to the desired frequency, compensating for any drift that may occur.

This stabilization process is vital for reliable communication, as any fluctuations in the carrier frequency can result in demodulation errors and degraded signal quality at the receiver. The modulation index, bit rate, and bandwidth, while important aspects of FM and signal characteristics, do not directly provide the mechanism necessary for the stabilization of the carrier frequency itself. Instead, they relate to how the information is encoded or the constraints of the system but do not actively control frequency stability like AFC does.