Pre-emphasis and De-emphasis

Pre-emphasis and de-emphasis are techniques used in communication systems to improve the signal-to-noise ratio (SNR) of the transmitted signal.

Pre-emphasis and De-emphasis
Pre-emphasis and De-emphasis

Pre-emphasis is a process that boosts the higher frequencies of the audio signal before it is modulated onto a carrier signal. The pre-emphasis is typically achieved by passing the audio signal through a high-pass filter with a predetermined frequency response. This technique is used in FM broadcasting to improve the SNR of the received signal by reducing the effect of noise on the high-frequency components of the audio signal.

De-emphasis is the opposite of pre-emphasis and is used in the receiver to restore the original frequency response of the audio signal. The de-emphasis is achieved by passing the received signal through a low-pass filter with a frequency response that is the inverse of the pre-emphasis filter used in the transmitter. This technique is used in FM receivers to improve the SNR of the received signal by reducing the effect of noise on the high-frequency components of the audio signal.

The pre-emphasis and de-emphasis filters are designed according to a standard, such as the RIAA equalization standard for vinyl records, or the NRSC pre-emphasis/de-emphasis standard for FM broadcasting. By using pre-emphasis and de-emphasis, the SNR of the transmitted signal can be improved, resulting in a higher-quality audio signal for the listener.