A simple simulation approach based on the modified central difference (MCD) method for analyzing the coupling characteristics of coupled transmission lines (CTL) is presented. Gaussian pulse responses on the sense line are demonstrated by graphical expressions. The frequency characteristics of the coupling factor is efficiently derived from the extracted input and output responses by using the fast Fourier transform (FFT) technique. It is shown that this approach is useful to analyze the coupling characteristics of symmetrical and asymmetric multi-section CTL.

Recently, dielectric material with a large relative dielectric constant (εr100) has received much attention as a substrate suitable for microwave integrated circuits. In this letter, an analysis on transmission-line-characteristics of a new type broadside-coupled strip transmission-line is presented which consists of two center strips placed respectively on the upper- and lower-side surface of a rectangular dielectric substrate with a large relative dielectric constant and two ground electrodes placed respectively on the other surfaces of the rectangular substrate. Analytical expressions for characteristic impedances of this transmission-line are given through a conformal mapping technique. The graphs of characteristic impedances and the coupling factor as a function of various waveguide-parameters are also given to facilitate the design works. Using this new strip-line, microwave miniature multi-stage broadside-coupled filters are easy to realize.

This paper presents two types of two-variable analog filters with maximally flat magnitude-squared attenuation response in the two-dimensional pass region. These are applied in order to obtain five types for the distribution of two-dimensional pass regions with respect to the design of microwave band pass filters consisting of a cascade of commensurate-line filter and lumped LC filter or a cascade of two commensurate-line filters in different propagation times.

In this letter, an analysis on transmission-characteristics of a new type broadside-coupled strip transmission-line is presented which consists of two center strips placed respectively on the upper- and lower-side surface of a rectangular dielectric substrate with a large dielectric constant and two ground electrodes placed respectively on the other surfaces of the rectangular substrate. Analytical expressions for characteristics of this transmission-line are given througn a conformal mapping technique and numerical results are given to facilitate the design works. Using this new strip-line, microwave miniature multi-stage broadside-coupled filters are easily realized.