696 



THE BELL SYSTEM TECHNICAL JOUKNAL, MAY 1954 



guides having one wall cut away to accept a coupling insert. In one set 

 of observations, the insertion loss in the driven-line and the transfer 

 loss to the undriven line were recorded for a variable number of No. 22 

 copper wires dividing a coupling aperture lll-i" long and linearly tapered 

 from 0.030" height at the ends to 0.33" height at the center. The results 

 are recorded in Fig. 37. At 102 holes, negligible power was abstracted 

 from the driven line, and the transfer loss to the undriven line forward 

 wave I E2 I was about 18 db. Note that more coupling was observed at 



3.3 34 

 \o IN CM 



uj 

 a 



Z ^ 



If) 

 P 7 



(b) 



50 HOLES 



JRANSFER LOSS E2 



INSERTION LOSS E, 



33 



3.4 



IN CM 



Fig. 37 — The transfer loss and the insertion loss versus frequency for the 

 coupled waveguides of Fig. 36, showing the cyclical exchange of power as the 

 coupling was increased Vjy reducing the number of dividing wires in the fixed 

 coupling aperture. 



