Discontinuities in planar millimeter circuits by FD-TD method

The successful application of FD-TD methods to millimetric planar transmission lines presupposes a satisfactory answer to the problem of infinite line termination absorbing boundary condition (ABC) in presence of high frequency dispersion. It is the purpose of this work to evaluate the efficiency of some commonly employed ABCs and to present a technique that reduces reflection error to less than 1% for microstrip and coplanar line circuits up to and beyond 50 GHz, that is lower than the discretization and round-off errors introduced by the FD-TD technique. The authors report some examples of microstrip and coplanar line circuits, comparing results with those obtained by other authors as well as with those of commercial packages and with experimental data.