AbstractThe Green's functionG(x, x')of a non‐uniform transmission line is formulated exactly in terms of partial transmission matrix parameters associated with different segments of the line. Exact differential expressions relate the transmission parameters to each other, and it is shown thatG(x, x')can be expressed entirely in terms of a single transmission parameterB(x, x')and its derivatives. The voltage responseV(x)on any doubly‐terminated line with arbitrary current source density along the line is given. A new perturbation technique, based on a Volterra integral equation, is developed which determinesV(x)in terms of known functions and arbitrary perturbing immittances on the l