The most popular among the class of nyquist filters are raised cosine and root raised cosine filter.

The roll off factor is defined by a fraction of excess bandwidth and the minimum nyquist bandwith. It ranges from 0 to 1.

A system with bandwidth Rs/2 can support a maximum transmission rate of Rs without ISI. Thus for ideal Nyquist filtering the maximum possible symbol transmission rate is called as symbol rate packing and it is equal to 2 symbols/s/Hz.

The sinc shaped pulse is the ideal nyquist pulse. If each pulse in the sequence to be detected is in sinc shape the pulses can be detected without ISI.

A pulse shaping filter should provide the desired roll off and should be realizable, that is the impulse response needs to be truncated to a finite length.

Due to the effect of system filtering the received pulse can overlap on one and another. The tail of one pulse smears into the adjacent symbol interval thereby interfering the detection process. This process is called as intersymbol interference.

For the roll off factor of 0 an ideal rectangular nyquist pulse is obtained. This is called as nyquist minimum bandwidth case.

ASK and PSK needs twice the transmission bandwidth of equivalent baseband signals. Thus these are called as double side band signals.

A nyquist filter is one whose frequency transfer function can be represented by a rectangular function convolved with any real even symmetric frequency function and a nyquist pulse is one whose shape can be represented by sinc function multiplied by another time function.

For raised cosine spectrum the minimum nyquist bandwidth is equal to 1/2T.