Branch cut integration method for computing signal propagation through dispersive media

A fast method for computing signals propagating through a waveguide or plasma is presented. This method converts the Bromwich contour into isolated contours encircling the poles and the branch cuts. The contribution of the branch cuts is proved to be equivalent to a low-pass filter, which has some good properties, and the signal passing through it can be calculated by using IFFT of small number of points. This method provides an efficient tool for dispersion problems