Efficient Modelling Technique of Lossy Microstrip Line Sections in Digital GaAs Circuits

An engineering solution based on an "ad hoc" synthesis of the impulse response, the forward and the backward characteristic impedances at a given terminal node is presented. The governing principle of this synthesis is to ensure a continuous transition from the quite distributed behaviour of the network (at high frequencies) to the quite lumped one (at low frequencies). Once this "adhoc" synthesis is done, the lossy line sections is interpreted as a recursive filter in order to combine high accuracy and stability with low computing time and storage requirements. Efficiency of this new extension is confirmed by several direct comparisons between computed and measured results on loaded or unloaded single and coupled microstrip line sections etched on GaAs substrates.