We shall use the Fourier transform
(6)
Taking into account that
(7)
and using the notation , we obtain from (5)
(9)
Solving system (9), we get for
(10)
For , we have
(11)
with
(12)
(13)
(14)
Hence
Using the inverse Fourier transforms ([4], Appendix 1)
(where is Heaviside’s function), we get
(15)
(16)
(17)
(18)