COUPLED WAVK THKOlfV AND WAVKCUIDK APPLICATIONS 



G87 



(ai — a-i)lc as small as —1, but a value as large as —10 or more is re- 

 quired in order to reduce the loss to is'i** to a moderate value for large 

 integrated coupling (ex) \-alues. 



When {ax — ai) is positive, the attenuation constant for the undriven 

 line is less than that for the driven line, and under these circumstances 

 £"1** can exceed unity. Physically this means that the power loss line is 

 caiiying the energy for a distance and returning it to the driven line at 

 a more distant point. The curves of Fig. 25 and Fig. 26 show the varia- 

 tion of E** and £"2** versus positive {ai — a2)/c values, at fixed values 

 of integrated coupling strength ex. For ex equal to 7r/4, the driven line 

 wave magnitude £'1** decreases as the ratio (ai — q:2)/c assumes small 

 positive values and goes through a balanced type of null near 

 (ai — a-i)/c = 3.5 (see Fig. 25). Again this is the resultant of the lower 

 loss undriven wave carrying power for a distance and returning it to the 

 driven wave in the proper phase to cause cancellation of the straight- 

 through component of the driven wave. For ex between 7r/4 and t/2 the 

 null would move from (ai — a2)/c near 3.5 toward (ai — a2)/c = 0. 



Figures 27 and 28 show the variation of Ei** and E2** versus the 

 integrated coupling strength ex at fixed values of (ai — q;2)/c. In these 



0.2 0.4 0.6 



Fig. 25 — Driven line wave amplitude versus (ai — an)/c with e([ual phase 

 fonstants and ex constant. Positive (ai — a2) indicates the undriven line has the 

 smaller attenuation constant. 



