# 3.4 Raised cosine filtering ## Raised cosine filter family |
Example 3.1 | Question 3.3 Question 3.4 |

#### A commonly used realization of the Nyquist filter is a raised cosine filter, so called because the transition band (the zone between passband and stopband) is shaped like part of a cosine waveform. The sharpness of the filter is controlled by the parameter a, the filter roll-off factor. When a = 0 this conforms to an ideal brick-wall filter. |

#### The bandwidth B occupied by a raised cosine filtered data signal is thus increased from its minimum value, Bmin = 0.5 X 1/Ts, to: #### Actual modulation bandwidth, B = Bmin(1 + a)