Boosting of higher frequency at the transmitter is done by using

Pre-Emphasis:

• Since in FM, higher frequency components of message signal are more prone to noise as compared to low-frequency components because of which the signal to noise ratio of the FM signal gets degrades at a higher frequency.
• ∴  To improve the SNR of FM signal, we add a circuitry before frequency modulator and this circuit is known as the Pre-emphasis circuit.
• The pre-emphasis circuit only amplifies/boosts the high-frequency component without changing the low-frequency amplitude and by doing this it provides an extra noise immunity to the FM signal and SNR of the FM signal gets improved.

De-emphasis:

• The de-emphasis circuit is used at the receiver side of FM modulation to return the original frequency response.
• De-emphasis circuit de-amplifies the higher frequency components as it is, i.e. it decreases the magnitude of higher frequencies with respect to the magnitude of other lower frequencies.
• De-emphasis is a complement of pre-emphasis, i.e. pre-emphasis circuit only amplifies the high-frequency component without changing the low-frequency amplitude.
• By doing this, it provides an extra noise immunity to the FM signal and SNR of FM signal gets improved.