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BELL SYSTEM TECHNICAL JOURNAL 



Hence, the general mid-shunt equivalent wave-filter can be obtained by 

 designing its series and shunt impedances as inverse networks, of im- 

 pedance product R 2 , to the shunt and series impedances, respectively, 

 of the general mid-series equivalent wave-filter , under which conditions 

 the two wave-filters have equivalent propagation constants. 



To illustrate, a structure for the general mid-shunt equivalent 

 low-band-and-high pass wave-filter corresponding to Figs. 2 and 3 is 



KWS SWQ\ ST5W\ /WT\ 



HH HHz« HH HH 



Transmitting Band 



Fig. 4 — General Mid-Shunt Equivalent Low-Band-and-High Pass Wave-Filter 



shown in Fig. 4. The impedance diagram indicates how the trans- 

 mitting and attenuating bands are produced. Here each anti-reso- 

 nant component in the series impedance is responsible for one of the 

 infinite attenuations shown in the equivalent attenuation diagram of 

 Fig. 3. It may be seen also that when in practice it is necessary to 

 balance the two sides of the line, the wave-filter of Fig. 4 requires 

 more series balanced inductances and capacities than that of Fig. 3 

 to give an equivalent propagation constant. For this reason the mid- 

 shunt equivalent wave-filter is usually not as economical as the mid- 

 series equivalent wave-filter. 



3. M-Type Wave-Filters. 



The term M-type will be applied to that case in each of the above 

 general wave-filters in which the coefficients m x . . . m n coalesce to 



