Measurements and Analysis of the Effects of the Edge on the Radiation from a Printed Circuit Board

• Main Authors: Liu, Cheng-Feng, 劉政峰
• Other Authors: Wu, Lin-Kun
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/38556781295105068052

碩士 === 國立交通大學 === 電機學院碩士在職專班電信組 === 99 === The microstrip line is the basic and popular transmission line structure in the microwave circuit, because of its simple architecture, low cost, and easy to apply in the printed-circuit technology. This thesis investigates the impact on electromagnetic radiation from high-speed circuit board by the board edge effect. PCB traces routed near board edges and carrying high-speed signals are considered to contribute to EMI problems. The measurement results show that board edge does affect the EMI performance and EMI can be suppressed by increasing the distance between trace and board edge. The common-mode current occurs due to a trace near a printed circuit board edge; it can be suppressed by a grounded guard trace. We also verify the 20H-rule. On board with power and ground planes, the fringing field at the edges of the board is contained by increasing the edge of the ground plane size by 20 times the thickness of the dielectric substrate.