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From an implementation point of view there are two kinds of digital filter : |
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The IIR filter calculates its outputs based on both its input and past values of its output, while the FIR filter only operates on its input signal. |
So what's an impulse? |
An impulse is a signal which has a value of zero everywhere except for a single sample which has a value of one. |
The impulse response of a filter is the output of a filter when the input to the filter is an impulse. |
FIR filters have a finite impulse response because any output sample is only calculated from a finite section of the input signal. |
IIR filters on the other hand feed their output back to their input and hence (theoretically) have infinitely long impulse responses. |
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