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As with the FIR filter, given a sampled signal s [n], the output of an IIR filter would be given by the following code : |
output [n] = b0 * s [n] + b1 * s [n-1] + b2 * s [n-2] - a1 * output [n-1] - a2 * output [n-2] ;
Notice that the value of output [n] depends on the values of output [n-1] and output [n-2]. As with the FIR filter, undefined values should be set to zero. |
This filter has 5 coefficients (more are possible) and they are grouped according to whether they affect the input (s[n]) or the previous outputs (output [n-whatever]). |
The order of an IIR filter is whatever is the maximum of the number of aX and bX coefficients above. |
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