# Low Pass FIR Filters with various Windows.

Cuthbert Nyack
Here some windows which are not normally used as filters are used to illustrate the relation between window characteristics and the resulting frequency response.
For comparison, the frequency response for the rectangular window is shown in blue for all the windows.

Scrollbar 0 changes Fn which sets the function of the applet.
Some of the windows which are illustrated include:-
when Fn = 0.
Exponential Window wx(t) = e(-a *(p |t|)b) for |t| <= 1/2 shown as green, Hamming is shown as red.

when Fn = 1.
Triangle window wt(t) = {1 - 2|t|/t}n for |t| <=t/2.
Rectangle-Triangle combination shown as green.
when a = 0, n = 1 combination is equivalent to a triangle and when a = 1, n = 1 combination is equivalent to a rectangular window.

when Fn = 2.
Cosine Window wc(t) = {cos(pt/t)}n for |t| <=t/2, n = 1 shown as red.

when Fn = 3.
Polynomial window wp(t) = (1 - |t|n)p for |t| <= 1, p = 1 shown as red.
When n = p = 1 result is a triangle window.