## Nyquist filtering – Example: cellular radio application

#### In some digital communications applications, digital radio for example, the transmission channel itself (the ether) may not impose any significant filtering effect across the modulation bandwidth, and the main filtering is performed by transmitter and receiver circuitry.

#### This transmitter filtering is employed largely to constrain the modulation to the regulated bandwidth, while in the receiver, the filtering is necessary to remove a multitude of other signals entering the receiver, and to minimize the noise entering the demodulator. Often the Nyquist filtering response needed for zero ISI is split equally between the TX and RX systems using a root raised cosine filter pair.

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