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Definition of "Preemphasis" |
In some transmission and recording systems (e.g. vinyl records, FM radio, analog magnetic tape), there is more noise at higher frequencies. To offset this, the audio signal is "preemphasized" at the transmitter -- filtered with a high-pass filter to boost the higher audio frequencies. A matching low-pass filter is used at the receiver to return to an overall flat audio-frequency response. The filter at the receiver reduces the high-frequency noise introduced by the transmission process. / A system process designed to increase, within a band of frequencies, the magnitude of some (usually higher) frequencies with respect to the magnitude of other (usually lower) frequencies, in order to improve the overall signal-to-noise ratio by minimizing the adverse effects of such phenomena as attenuation differences, or saturation of recording media, in subsequent parts of the system. Example Preemphasis circuit shown to the right. / In some transmission and recording systems (e.g. vinyl records, FM radio, analog magnetic tape), there is more noise at higher frequencies. To offset this, the audio signal is "preemphasized" at the transmitter filtered with a high pass filter to boost the higher audio frequencies. A matching low pass filter is used at the receiver to return to an overall flat audio frequency response. The filter at the receiver reduces the high frequency noise introduced by the transmission process. / In telecommunication preemphasis is the intentional alteration of the amplitude-vs-frequency characteristics of the signal to reduce adverse effects of noise in a communication system. / IEEE 802 refers to a family of IEEE standards dealing with local area. |
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