Impedance discontinuities cause attenuation, attenuation distortion, standing waves, ringing and other effects because a portion of a transmitted signal will be reflected back to the transmitting device rather than continuing to the receiver, much like an echo. This effect is compounded if multiple discontinuities cause additional portions of the remaining signal to be reflected back to the transmitter. This is a fundamental problem with the daisy chain method of connecting electronic components.
When a returning reflection strikes another discontinuity, some of the signal rebounds in the original signal direction, creating multiple echo effects. These forward echoes strike the receiver at different intervals making it difficult for the receiver to accurately detect data values on the signal. The effects can resemble those of jitter.
這個有趣啦...
訊號線的導體,若是做的不太漂亮,例如說粗細變化、損傷、雜質、結晶不連續之類的,那麼便會形成個阻抗不連續面,
電訊號傳到那個位置就會有部分反射回去,傳過去的訊號量就會低一些,
這個我們小時候甩童軍繩時就玩過。
問題還不只是衰減而已,倘若這種不連續處很多,那會如何?
原訊號與反射訊號就會在這些不連續處亂反射,來來去去,像是很多條訊號線的組合,這很妙吧?