Overmodulation
Encyclopedia
Overmodulation is the condition that prevails in telecommunication
when the instantaneous level of the modulating signal exceeds the value necessary to produce 100% modulation
of the carrier
. In the sense of this definition, it is almost always considered a fault
condition. In layman's terms, the signal is going "off the scale". Overmodulation results in spurious emissions by the modulated carrier, and distortion
of the recovered modulating signal. This means that the envelope of the output waveform is distorted.
Although overmodulation is sometimes considered permissible, it should not occur in practice; a distorted waveform envelope will result in a distorted output signal of the receiving medium.
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
when the instantaneous level of the modulating signal exceeds the value necessary to produce 100% modulation
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...
of the carrier
Carrier wave
In telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...
. In the sense of this definition, it is almost always considered a fault
Fault (technology)
In document ISO/CD 10303-226, a fault is defined as an abnormal condition or defect at the component, equipment, or sub-system level which may lead to a failure....
condition. In layman's terms, the signal is going "off the scale". Overmodulation results in spurious emissions by the modulated carrier, and distortion
Distortion
A distortion is the alteration of the original shape of an object, image, sound, waveform or other form of information or representation. Distortion is usually unwanted, and often many methods are employed to minimize it in practice...
of the recovered modulating signal. This means that the envelope of the output waveform is distorted.
Although overmodulation is sometimes considered permissible, it should not occur in practice; a distorted waveform envelope will result in a distorted output signal of the receiving medium.
See also
- Clipping (audio)Clipping (audio)Clipping is a form of waveform distortion that occurs when an amplifier is overdriven and attempts to deliver an output voltage or current beyond its maximum capability...
- Overshoot (signal)Overshoot (signal)In signal processing, control theory, electronics, and mathematics, overshoot is when a signal or function exceeds its target. It arises especially in the step response of bandlimited systems such as low-pass filters...
- VOGADVOGADIn electronics systems, a VOGAD or voice-operated gain-adjusting device is a type of automatic gain control or compressor for microphone amplification. It is usually used in radio transmitters to prevent overmodulation and to reduce the dynamic range of the signal which allows increasing average...
(Voice Operated Gain Device)