In mathematics, a nonrecursive filter only uses input values like x[n − 1], unlike recursive filter where it uses previous output values like y[n − 1].

In signal processing, non-recursive digital filters are often known as Finite Impulse Response (FIR) filters, as a non-recursive digital filter has a finite number of coefficients in the impulse response h[n].[1]

Examples:

  • Non-recursive filter: y[n] = 0.5x[n − 1] + 0.5x[n]
  • Recursive filter: y[n] = 0.5y[n − 1] + 0.5x[n]


An important property of non-recursive filters is, that they will always be stable. This is not always the case for recursive filters.

  1. ^ Helms, H (September 1, 1968). "Nonrecursive digital filters: Design methods for achieving specifications on frequency response". IEEE Xplore. Archived from the original on August 10, 2024. Retrieved August 10, 2024.