COUPLED WAVE THEORY AXD WAVKGUIDE APPLICATIONS 



675 



Thus, something; on the order of 50 or 00 (Mnially spaced couiihngs might 

 be needed. 



Simulation of continuous coupling functions with eciual strength 

 couplings may he carried out as follows: the coupling amplitude \-ersus 

 distance plot may be di\-ided along the distance axis into a number of 

 inter\-als of equal area, and a point coupling placed at the center of each 

 interval. The more efficient continuous coupling functions recjuire more 

 point couplings to get a good simulation in this manner. For example, 

 the function of line 2, Fig. 4, "with c = 22.4 and /.• = 1 has been simulated 

 with 12 and 40 equal strength couplings (as described above) and the 

 exact discrimination plotted using (13) and (14). The results are given 

 in Figs. 13 and 14. The original continuous coupling function yields dis- 

 criminations greater than 38 db for all values of ^/tt greater than 2 ; the 

 40-point simulation approximates this well in the region of Q/-K = 1.7 to 

 4.5, but thereafter begins to fail. The 12-point simulation (Fig. 13) never 

 matches the original but does best in the region of small Q/t. 



It is more efficient to seek high discriminations by tapering the 

 strength of equally spaced couphngs than by tapering the spacing be- 

 tAveen equal strength couplings. However, when Ioav discriminations are 

 acceptable, the relative efficiency of tapering the spacing between con- 



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Fig. 13 — Discrimination for 12 oqiial-strcngth point couplings arranged to 

 simulate the continuous distribution of Fig. 4, line 2. 



