Transient Analysis of Mode Structures and Quantification of Crosstalk in Printed Metal Strips

A detailed analysis of mode structures inside coupled microstrip lines and their correlation with crosstalk between traces has been performed. The use of finite-difference time-domain and singular value decomposition methods for modal identification followed by cross correlation for crosstalk prediction is demonstrated in this paper. The combination of these methods is robust, versatile and ideal for pulsed applications in an inhomogeneous, anisotropic multi-layer substrate with complex 3D structures. Moreover, all possible modes are extracted in a single analysis. This novel approach provides a quantitative measurement of crosstalk by establishing correlation between modes evolving inside the source line and the field waveforms coupled with the victim line. To our knowledge, this is the first time such a study has been performed. The effects of line topology and pulse characteristics are examined. At the early stage of pulse evolution, the TEM mode of the source line dictates coupling, however, as the pulse advances the higher-order TM mode dominates and exhibits significant contribution to the evolution of the waveform coupled with the victim line which is confirmed by cross-correlation. This study has physical significance in devising systems for suppressing unwanted modes responsible for crosstalk and radiation leakage due to UWB pulses.