This application note considers the design of frequency-

selective filters, which modify the frequency content

and phase of input signals according to some specification.

Two classes of frequency-selective digital filters

are considered: infinite impulse response (IIR) and finite

impulse response (FIR) filters. The design process

consists of determining the coefficients of the IIR or FIR

filters, which results in the desired magnitude and

phase response being closely approximated.