Field coupling to nonuniform microstrip transmission lines

In this paper we present an efficient new method for frequency domain and transient analysis of the single nonuniform lossless microstrip transmission line excited by an external electromagnetic wave. First the nonuniform transmission line has been subdivided into a large number of uniform sections called steplines. Then the effect of the external wave on the uniform sections has been derived. Finally, by applying the boundary conditions at the discontinuities of the steplines and satisfying the terminal conditions the induced voltage and currents at the terminals have been derived. So, the solution in the frequency domain is obtained, and then the FFT algorithm is used to find the time domain response of the line.