PRE-EMPHASIS / DE-EMPHASIS

Communications Systems Glossary

Communications Systems — Pre-emphasis / de-emphasis

Information on Pre-emphasis/de-emphasis

Although FM systems are relatively immune to noise added in the channel, they are prone to suffer from the effects of non-linear noise introduced as part of the demodulation process in the receiver. This noise is greatest for the higher frequencies, which tend to have the smallest magnitude. Pre-emphasis networks therefore artificially amplify the high frequencies in the transmitter before modulation to prepare them better for the noise introduced in demodulation in the receiver. After demodulation, de-emphasis networks returns the high frequencies to their original amplitudes before passing to the AF amplifier.

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