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FIR Filter Design

Digital filters with finite-duration impulse response (all-zero, or FIR filters) have both advantages and disadvantages compared to infinite-duration impulse response (IIR) filters.

FIR filters have the following primary advantages:

The primary disadvantage of FIR filters is that they often require a much higher filter order than IIR filters to achieve a given level of performance. Correspondingly, the delay of these filters is often much greater than for an equal performance IIR filter.

Filter Method
Filter Functions
Apply window to truncated inverse Fourier transform of desired "brick wall" filter
fir1, fir2, kaiserord
Multiband with Transition Bands
Equiripple or least squares approach over sub-bands of the frequency range
firls, firpm, firpmord
Constrained Least Squares
Minimize squared integral error over entire frequency range subject to maximum error constraints
fircls, fircls1
Arbitrary Response
Arbitrary responses, including nonlinear phase and complex filters
Raised Cosine
Lowpass response with smooth, sinusoidal transition

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