SCATTERING MATRIX APPROACH FOR FREQUENCY AND TIME-DOMAIN CROSSTALK ANALYSIS IN MULTILAYER PCBS

The problem of crosstalk evaluation among PCB traces in a multilayer s tructure is studied by means of an S-matrix technique. Two bundles of parallel lines, perpendicularly crossing on different layers, are anal ysed, and this complex structure is decomposed into subsystems, each o f them characterised by its S matrix. The elementary subsystems consis t of bundles of parallel lines and crosses of two lines. A particular algorithm, developed to number the ports of each subsystem, allows one to easily recognise the interconnected ports and the external ports ( I/O ports), to achieve the S matrix of the overall structure in terms of the I/O ports. The application of this technique to a 3 x 3 and a 7 x 7 configuration shows a good agreement between theoretical and expe rimental results. Finally, the analysis in the frequency domain is ext ended to the time domain by a standard FFT algorithm, and, as an examp le, an ESD current flowing along a line is examined, as well as its co upling toward an adjacent and crossing line.