Finite impulse response
![A direct form discrete-time FIR filter of order N. The top part is an N-stage delay line with N + 1 taps. Each unit delay is a z−1 operator in Z-transform notation.](/Images/godic/202501/13/FIR_Filter.svg1607.png")
![A lattice-form discrete-time FIR filter of order N. Each unit delay is a z−1 operator in Z-transform notation.](/Images/godic/202501/13/FIR_Lattice_Filter1607.png")
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![Fig. (b) Pole–zero diagram](/Images/godic/202501/13/MA2PoleZero_C.svg1607.png")
In signal processing, a finite impulse response (FIR) filter is a filter whose impulse response (or response to any finite length input) is of finite duration, because it settles to zero in finite time. This is in contrast to infinite impulse response (IIR) filters, which may have internal feedback and may continue to respond indefinitely (usually decaying).