High-frequency signal transmission line losses make it difficult for the receiver to interpret the information correctly.The following two causes of transmission line losses are due to the transmission medium:
Dielectric absorption: High-frequency signals excite molecules in the insulator, which causes the insulator to absorb signal energy. This absorption reduces the signal strength. Dielectric absorption relates to the PCB materia
and can be lessened by careful material selection.
Skin effect: Varying current waveforms caused by AC and high-frequency signals tend to travel on the conductor’s surface. Signals traveling on the surface cause the self-inductance of the material to produce an increased
inductive reactance at high frequencies, which forces electrons to the material’s surface. The effective reduction of conductive area causes an increase of resistance and, therefore, attenuation of the signal. Increasing track width
can reduce the skin effect, but this is not always possible. Figure shows a cross sectional view of a printed circuit board (PCB).
高频信号的传输损耗导致接收器难以正确解析信息.如下两种损耗和传输介质相关:
介质损耗:高频信号激发介质中的偶极子,这会让介质吸收信号的能量降低信号强度.介质吸收和PCB的材料有关,通过选择不同的材料可以降低介质损耗.
趋肤效应:交流或者高频的信号总是趋向于在导体的表面传输.材料的自感导致在导体内部传输的电流受到更大的感抗,从而使电流向导体表面集中.趋肤效应增大了电流受到的阻抗,使信号衰减.频率越高,趋肤效应越显著,从而使高频信号经受更大的衰减.增加传输线的宽度可以降低趋肤效应的影响,但是并不是总可以这样做.图示一个PCB板上传输线的截面.
The main part of this article is translated from write paper of Altera. But the original text have an error in it. Can you point it out ?
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keendawn_745908826 2010-11-5 10:25
用户1277994 2010-11-3 14:51
用户1575195 2010-10-29 21:59
tamkay:
I agree with u. Thanks for your attention.
B&R!
tamkay_819533976 2010-10-29 11:02
The effective reduction of conductive area
应为：
The reduction of effective conduactive area
tamkay_819533976 2010-10-29 10:56
Signals traveling on the surface cause the self-inductance of the material to produce an increased
inductive reactance at high frequencies, which forces electrons to the material’s surface.
应为
Signals traveling on the surface cause the self-inductance of the material to produce an decreased
inductive reactance at high frequencies, which forces electrons to the material’s surface.
电流从表面流过有利于减小感抗，而电流总是倾向从阻碍最小的路径流过，所以材会产生趋肤效应。