192 



BELL SYSTEM TECHNICAL JOURNAL 



It will be found that a filter of several sections of the type described 

 in this paper will have somewhat less loss in the attenuated band than 

 the usual type of design. On the other hand the loss in the band will, 

 in general, be less unless additional elements are used in the standard 

 type of filter to reduce reflection losses. A design for a pair of constant 



— vi). 



LOW PASS I 



HIGH PASS I 



■- vMilrpjmrp 



0.172 0.240 0.140 



LOW PASS IT AND HI HIGH PASS H AND III 



Fig. 9 — The configuration of the filters of Fig. 8. 



0.181 0.105 0.147 0.152 



ih-pHI 



>0.09l feO.126 )pO.I78 



_^I.2I nl^O.aSS =J=0.I78 



STANDARD 

 2.71 0.180 0.172 0.170 o.l49 0.147 0.141 0.0094 



>0.264 fc>0.182 



"0.416 rilO.232 r:j=O.I34 



CONSTANT RESISTANCE 



Fig. 10 — Comparison of the elements of typical standard and constant 

 resistance filters. 



resistance filters having a cross-over frequency of 1000 cycles is 

 compared with a design for a pair of standard filters in Fig. 10, No 

 additional elements have been added to the standard type to improve 

 the impedance.^ The loss characteristics for the two low-pass filters 



'"Impedance Correction of Wave Filters," E. B. Payne, and "A Method of 

 Impedance Correction," H. W. Bode, Bell Sys. Tech. Jour., October 1930. 



"Extensions to the Theory and Design of Electric Wave Filters," Otto J. Zobel, 

 Bell Sys. Tech. Jour., April l'931. 



