Finite-Difference Time-Domain Analysis of Electromagnetic Modes Inside Printed Coupled Lines and Quantification of Crosstalk

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 multilayer substrate with complex 3-D 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. The effects of line topology, material properties, and pulse characteristics are examined. At the near end, transverse electromagnetic mode of the source line dictates coupling; however, as the pulse advances, the higher order transverse magnetic mode dominates and exhibits significant contribution to the evolution of the waveform coupled with the victim line at the far end, which is confirmed by cross correlation. This paper has physical significance in devising systems for suppressing unwanted modes responsible for crosstalk and radiation leakage due to fast pulses.