隨著印刷電路板佈線密度的增加及CPU時脈頻率的增高，電磁干擾(EMI)、電磁耐受性(EMS)與電磁耦合等電磁相容性(EMC)的相關問題，成為未來PCB發展的重要關鍵因素之一。而本文所欲探討之現象，主要是電磁耦合所導致的串音問題，文中針對不同的傳輸線結構，如microstrips、coplanar strips與修正型微帶線等，採用全波馬克斯威爾方程式，用完美匹配層(PML)的邊界條件以時域有限差分法(FDTD)分析之。
就microstrips而言，串音電場值隨著導體寬度的增加及導線間距的增加而降低，且其接地方式因為迴路面積固定而較coplanar strips為佳。而就coplanar strips之結構而言，串音電場值隨著導體寬度的增加而降低；但若增加導線間距時，串音電場值則在5~15GHz頻段內會隨著導線間距增加，迴路面積增大而增加。另外，對電場源而言，rise time較小(訊號上升速度較快)之電場源其串音現象較為嚴重；反之，對於一個rise time較大之電場源，其串音電場值則隨著頻率之增加而漸趨弱小。
對於接地構形，coplanar strips之接地參考線越接近信號線時，串音電場值較小，串音問題能獲得較佳之改善；而對於修正型微帶線結構，由於基板上導線與下接地線成對稱，互感值較小而能有效減低串音現象。另外，對PCB之基板而言，由於串音電場隨著自容量增加而減小，故介電常數大者為佳；但介電常數較小者在某些諧頻時decay較快。

With the increasing density of printed circuit board (PCB) layouts and higher CPU clock frequency, the EMC problem becomes one of the dominant factors of future PCB development. In this thesis, a finite difference time domain (FDTD) numerical method is used to simulate the crosstalk, the trace-to-trace coupling which distorts the signal integrity, between PCB lands for different PCB layouts including microstrips and coplanar strips in frequency ranges up to 20GHz. And Maxwell’s equations are chosen to simulate the crosstalk phenomena, and perfectly matched layers (PML) are used as the absorbing boundary condition.

For microstrips, the crosstalk electric fields decrease as the width of metal lines and the distance between two different metal lines increase. And for coplanar strips, the crosstalk electric fields also decrease as the width of metal lines increase, but it would increase when the distance between different metal lines increase because of the increase of the loop area. In addition, for sources of the PCB circuits, the smaller the rise time is, the more serious the crosstalk phenomena are.

Additionally, for grounding, when the grounding lines of coplanar strips are as near as signal lines as possible, the crosstalk electric fields are smaller. And for modified microstrips, the phenomenon of crosstalk can be reduced because signal lines and grounding lines are symmetric with the substrate. Furthermore, it is observed that the crosstalk can be reduced by using appropriate layouts, and the nonsynchronous phenomenon caused by different mode velocities can be reduced by proper arrangement of ground planes.

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