CROSSTALK IN COAXIAL CABLES 



347 



Z I 



If this is combined with the direct far-end crosstalk —^ , and the 



terms rearranged as in the case of equation (2b), the total far-end 

 crosstalk F. is obtained as 



F. = X^lil -^) - 



/^ 



73' - y 



+ 2^ 



737^ cosh 73/ — cosh 7/ 



(73^ - y')' 



sinh 73/ 



]• 



(17) 



It will be noted that equations (2b) and (17) differ only in the terms 

 which are not proportional to the length and which thus are of de- 

 creasing importance as the length becomes great. 



Near-End Crosstalk 



The indirect near-end crosstalk N/ due to the tertiary current is(x) 

 is given by 



N, 



Jo 2Z 



'''^'\-r^dx 



(18) 



By substituting iz{x) from equation (15) herein, and combining the 

 result with the direct near-end crosstalk, 



Z12 1 - e-^y' 



IZ 27 



we obtain the total near-end crosstalk A^^, which may be written in 

 the form 



N, = X 



1 - e-2.: / (J _ ^^ _^ ^7^(73^ + 7') 



27 



^737^ 



(73^ - 1'')'' 



(73' - 7')' 



(1 -f e-^'T-Q cosh 73/ 

 sinh 73/ 



2e-T' 



(19) 



II — Identical Coaxial Lines Symmetrically Placed with 

 Respect to Each of Two Dissimilar Tertiaries 



We will now consider the case of any number of identical coaxial 

 lines with the outer conductors in continuous electrical contact and 

 symmetrically placed with respect to each of two dissimilar tertiaries 

 with coupling between them. 



In an unpublished memorandum by J. Riordan, the general forms 

 are developed for the currents and voltages in two parallel circuits 

 having uniformly distributed self and mutual impedances and ad- 

 mittances, when these circuits^are subjected to impressed axial fields. 



