Comparison of Crosstalk Analysis Methods for Shifted Parallel-Coupled Lines on a PCB

As the circuit density of pattern traces and the data rate on a printed circuit board (PCB) is increased, an unexpected electromagnetic interference (EMI) such as crosstalk can degrade the intended signal transmission. The crosstalk problems on multiconductor transmission lines (MTLs) which are parallel and have the same length have been researched by C. R. Paul[1]. In case of shifted parallel-coupled lines as shown in Fig. 1, the crosstalk can be analyzed by using 1-D FDTD (Finite-Difference TimeDomain) method based on the MTL equations[2]. The shifted parallel-coupled lines are divided into three regions, which are uncoupled line section in line #1, parallel-coupled line section in line #1 and #2, and uncoupled line section in line #2. The uncoupled line section is represented by selfcapacitance and self-inductance and the coupled line section is represented by selfand mutualcapacitance and inductance matrices. On the other hand, Kami[3] suggested a circuit-concept approach by which the crosstalk analysis between two transmission lines of finite length in arbitrary directions is analytically possible. His approach can also be applied to the case of the shifted parallel-coupled lines. In this paper, the crosstalk phenomena of shifted parallel-coupled lines on a PCB are investigated using 1-D FDTD method and the circuit-concept approach, respectively. Also, the theoretical results of these two approaches are compared with the HFSS simulation and the measurement.