What is a roll-off factor?

The roll-off factor, , is a measure of the excess bandwidth of the filter, i.e. the bandwidth occupied beyond the Nyquist bandwidth of . Some authors use .

Which are the advantages of the raised cosine pulse shape?

The raised-cosine filter offers better performance from the point of view of bandwidth. Even with maximum roll-off factor () the maximum bandwidth is only 1/T. Many QAM systems can work with smaller roll-off factors, thus further reducing the bandwidth.

What is the roll-off factor of an ideal LPF?

A better compromise would be a roll off factor somewhere between 0.25 and 0.5 (B and C).

How is roll-off factor calculated?

You need to identify the passband and the corner frequency by doing a frequency response plot. The corner is usually considered the point where the frequency response drops 3 dB. The rolloff rate is the slope of the section just past the cutoff corner frequency in dB per octave.

What is Nyquist zero ISI criterion?

For nullifying the ISI terms, with an impulse of unit value applied at to the combined filters , the samples of the at the output of the filter combination should be 1 at the sampling instant and zero at all other sampling instants . This is called Nyquist criterion for zero ISI.

What are the advantages of active filters?

Advantages of active filters:

• These filters are more responsible than passive filters.
• No resonance issue.
• It can eliminate any harmonics.
• Used for voltage regulation.
• Used for reactive power compensation.
• It provides reliable operation.
• It can be designed to provide some passband gain.
• No loading problem.

What is the typical value of roll off factor?

Thus, as a universal result, the optimum roll-off factor for the Nyquist pulse transmission is approximately 0.4~0.6. Fig.

How do you find the filter roll off factor?

Rolloff: The slope of the filter’s response in the transition region between the pass-band and stop-band. Rolloff is given in dB/octave (a doubling of frequency) or dB/decade (ten times the frequency). If the response changes rapidly with frequency, that rolloff is termed steep.

What is roll off of a filter?

Roll-off is the steepness of a transfer function with frequency, particularly in electrical network analysis, and most especially in connection with filter circuits in the transition between a passband and a stopband. Roll-off enables the cut-off performance of such a filter network to be reduced to a single number.