1236 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1954 



the signal pulse at the same point, 



1^ —{n—l){ax—ci{)z /q\ 



(1 - l^^l- ' ^^^ 



These expressions show that the largest unused mode amplitude at any 

 point in the line will be the one most recently converted from the signal 

 wave and will be nearest to the signal pulse in time position. 



The sketch shown in Fig. 19 represents schematically the signal pulse, 

 the unused mode pulse and the reconverted pulse amplitudes after n trips 

 past the conversion point. It is interesting to note that the most recent 

 (the n"*) conversion to the unused mode appears in a time position close 

 to the signal pulse whereas the most recent reconversion appears at a 

 time far removed from the signal pulse. 



Let us investigate the ratios (5) through (8) under conditions repre- 

 sentative of those in the 5" diameter waveguide line. Row 2 of Figure 15 

 shows that after 40 trips down and back on the 500-foot line, i.e., after 

 80 trips past the center of this line (where there is assumed a single con- 

 version point), the amplitude of the reconverted pulses which appear 

 just before and just after the signal pulse are about equal to the signal 



z ^A 

 <J < 



^4 



K"i 



LU 1- 



%i 



Z<i 



O 



O 



(Tl 



a. 



RECONVERSION 

 1st 



2nd 



3rd 



etc 



Fig. 19 — Sketch of pulse amijlitudos in a line having etiually spaced conversion 

 points. 



