Synthesis of nonrecursifs filters or FIR

      The synthesis consists in determining the structure of a filter according to the frequency answer which one wants to obtain.

1. Determination by identification in a known structure      
          Let us suppose that one likes to make a low band filter of frequency of cut [Image] ,one can then set the

structure realized with the following FIR filter : [Image].

answer of this filter : [Image] , or : [Image]

One has so this frequency answer :

[Image]

So these answere :

[Image]  [Image]

One notices: fc=fe/4. It is thus necessary to fix fe to have the wished frequency of cut.