A Study of a New Time-Domain Method of Lines and Its Application for the Characterization of Microstrip Line and Its Discontinuities

A new time domain method for the analysis of planar guided wave propagation and scattering is developed in which an analytical process is incorporated along one of the spatial dimensions. The method makes use of the Method of Lines which has been applied to microwave problems in the time- harmonic cases. The procedure and the formulation of the proposed method to calculate the time history of a pulse scattered in a partially filled waveguide and a finned waveguide are described in detail. The cutoff characteristics of the structures can be derived via the Fourier transform of the time-domain pulse scattering data. The results are compared with other available data. The method is extended to characterize three dimensional structures. The procedure and the formulation of the three dimensional analysis are explained. The propagation and scattering data of a pulse in a planar transmission line with its discontinuities can be obtained by using the three dimensional analysis. From the time domain data, the frequency-domain characteristics for a wide range of frequencies can be extracted by the Fourier transform. The important design parameters such as the characteristic impedance and the propagation constant of a uniform microstrip line and the scattering parameters of its discontinuities (step-in-width, open end and gap discontinuities) are presented and compared with available published data. (JHD)