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Home Transmission Lines Electromagnetic Wave Propagation  


Electromagnetic Wave PropagationSuppose that for the infinite line of the preceding section a point an infinite distance from the sending end is considered. At this point, l = ∞ for equations 21 and 22, and these can be equated to zero and become
and
These equations can be written
and
since from the theory of hyperbolic functions
An examination of a table of hyperbolic functions will show that, when l = ∞, tanh lsqrt(zy) = 1.0; therefore, equations 27 and 28 become
and
where Z_{s} is the sendingend impedance of the infinitely long line considered, measured between the two line input terminals. If equations 29 and 30 are substituted in the general expressions 22 and 21, respectively, then
and
Since ε^{x} = (cosh x  sinh x), these equations become
and
where
and is called the propagation constant per loop mile for the line under consideration. Like equations 21 and 22, these equations also give the voltage or current at any point along the line in terms of the sendingend values.


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