1.Impulse response
Joseph Fourier first represented Fourier integral theorem in the following DOE:
[1]
Which is then introduced into the first delta function as following:
[1]
And the end end up with what mathematicians called Dirac delta function:
[1]
[1] “Dirac delta function. Internet: http://en.wikipedia.org/wiki/Dirac_delta_function, March.
8, 2013 [March. 10, 2013].
2.Fourier series
The input x(t) is a function with a fundamental period x(t)= 1 from x= 0 to 1 and f(x)= -1 from x= -1 to 0, with a discontinuity at x=0. The following graphs from matlab represents Gibbs phenomena, as n increases the overshot decreases.
The upper is the Gaussian filter, while bottom is the unsharp.