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THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1951 



ment is for the conductor to be twice the thickness of the dielectric. This 

 rule holds, of course, only as long as the effective skin depth defined in 

 equation (III-42) is greater than 5. If use of the ratio t/W = 1/2 finds 5^ 

 smaller than 5, the best thing to do is to increase t/W until the effective 

 skin depth dw becomes equal to s. 



V. Transmission Line Filled with Laminations 



Li the last section, we have calculated the attenuation of the transmission 

 line shown in Fig. 7. By reference to equation (IV-21), it is seen that this 

 attenuation decreases as ^ increases. Since we have assumed in deducing 

 equation (IV-21) that ^ <3C /?, we cannot use that equation to find the atten- 

 uation for s = d. Nevertheless, the suggestion is evident that this case may 

 be particularly interesting. 



Fig. 10 — Plane parallel transmission line filled with laminations. 



Accordingly, let us consider the transmission Une shown in Fig. 10, where 

 the space between the outer shields has been completely filled with lamina- 

 tions. As before, we can write down the following fields: 



In shield: 



rviy-d) 



H, = Ae 



E.^ -A"^- e-'^'-^^ 



= Vi 



to3fxo(r 



(V-l) 

 (V-2) 

 (V-3) 



In laminae; 



H, = cosh ^y 



Ex — z sinh f y 



(V-4) 

 (V-5) 



