FIR filter (windowing method)

     As we know IIR filter requires infinite no. of samples.But it is difficult to store such many values.One of the solution for it is to go for truncation of these infinite values and making it finite i.e. nothing but FIR filter. For that we took same input as that of Butterworth filter. We used windowing method to do that. There are no. of windows that can be used for designing of FIR filters, selection criteria of a window is to have a maximum attenuation in stopband and transition width should be as small as possible. Procedure to do this is to first find desired h(n) i.e. hd(n) and multiply it with required window function.

   The reason for using a FIR filter was that we can't always have a stable IIR filter. But FIR filters are always stable. And reason for this is position of the poles, they lie on the origin in digital filter.Also linear phase FIR filter reduces distortion in the output.