COITPLED AVAVE THKOHY AND WAVEGUIDE APPLICATIONS 



G71 



for the forward wave discrimination and 



for the (hrectix'ity as defined earlier in connection with (4). 



The discrimination fnnction for the composite couphng function 



P,. . . ,. F,{d = 0,d' = 0) F,{d = 0) 1 ,^_. 



Discrmimation = ^ = -. (12) 



Fo 



Fi cos 6' 



The factor 1/cos d' is the discrimination function associated with two 

 point couplings, and the overall discrimination is the 'product of that 

 discrimination and the discrimination associated Avith a single distributed 

 coupling function </)i(.r). This line of thought may be extended to show 

 that use of the same distributed coupling function in place of each point 

 coupling in the multi-element distributions described in the following 

 section results in multiplying the discrimination of the multi-element 

 coupling function by the discrimination associated wdth the distributed 

 coupling function. 



In many cases of interest it is either inconvenient or impossible to use 

 absolutely continuous coupling between transmission lines. In the w^ave- 

 guide case illustrated in Fig. 1, for example, a continuous slot cut in the 

 common Avail Avould not proA'ide coupling of the distributed form due to 

 a AvaA-e Avhich Avould oscillate back and forth in the slot itself. We knoAv, 

 hoAveA-er, that the effects of the continuous coupling distribution can be 



d 



(X) 



Fig. 9 — Schematic of inultii)le distributed coupling functions. 



