What happens in over modulation?

In the context of signal processing and communication systems, overmodulation occurs when the amplitude of a modulated signal exceeds the maximum value that can be accurately represented or transmitted. This can lead to distortion and loss of information in the signal. Overmodulation typically occurs in analog modulation schemes such as amplitude modulation (AM) and frequency modulation (FM).

Amplitude Modulation (AM):
In AM, the information signal (typically an audio signal) is used to vary the amplitude of a high-frequency carrier signal. The carrier carries the modulated information over the communication channel. If the amplitude of the modulating signal exceeds the maximum limit allowed by the modulation scheme, the signal becomes overmodulated. This results in the peaks of the carrier wave being "clipped" or cut off, leading to distortion of the original signal.

Frequency Modulation (FM):
In FM, the frequency of the carrier signal is varied in proportion to the modulating signal. If the amplitude of the modulating signal is too high, the frequency deviation can exceed the allowed range, causing overmodulation. This results in the FM signal occupying a wider bandwidth than usual and can lead to interference with neighboring channels or adjacent frequency bands.

In both cases, overmodulation causes the modulated signal to deviate significantly from the intended modulation scheme, making it difficult for the receiver to accurately demodulate the original information. This distortion can result in poor audio quality, data corruption, and reduced transmission range, among other issues.

However, it's important to note that some modern communication systems and devices incorporate mechanisms to prevent or mitigate overmodulation. These systems might include techniques like automatic gain control (AGC) and limiting to ensure that the signal remains within the acceptable range and to avoid excessive distortion.