FIR General Information

FIR, or Finite Impulse Response, filters have the distinctive trait that their impulse response lasts for a finite duration of time as opposed to IIR, or Infinite Impulse Response, filters whose impulse response is infinite in duration. This trait is due to the fact that there are no feedback paths in the filter. All Z transform terms are in the numerator. Z transforms written in the Z**-1 notation only contain a "1" in the denominator. Z transforms written in the Z**+1 notation, as in FilterSolutions, only have a Z**N in the denominator, where N is the number of states in the filter.

FIR filters offer several advantages over IIR filters:

• Completely constant group delay throughout the frequency spectrum.

• Complete stability at all frequencies regardless of the size of the filter.

FIR filters also come with some disadvantages as well:

• The frequency response is not as easily defined as it is with IIR filters.

• The number of states required to meet a frequency specification may be far larger than that required for IIR filters.

FilterSolutions allows up to 10,000 taps to create the FIR filter.