Based on classical circuit theory, this article develops a general analytic solution\nof the telegrapherâ??s equations, in which the length of the cable is explicitly\ncontained as a freely adjustable parameter. For this reason, the solution\nis also applicable to electrically short cables. Such a model has become indispensable\nbecause a few months ago, it was experimentally shown that voltage\nfluctuations in ordinary but electrically short copper lines move at signal velocities\nthat are significantly higher than the speed of light in a vacuum. This\nfinding contradicts the statements of the special theory of relativity but not, as\nis shown here, the fundamental principles of electrical engineering. Based on\nthe general transfer function of a transmission line, the article shows mathematically\nthat an unterminated, electrically short cable has the characteristics\nof an ideal delay element, meaning that an input signal appears at the output\nwith a slight delay but remains otherwise unchanged. Even for conventional\ncables, the time constants can be so small that the corresponding signal velocities\ncan significantly exceed the speed of light in a vacuum. The article also\nanalyses the technical means with which this effect can be conveyed to very\nlong cables.
Loading....