. The Bell System technical journal . o n^W 0 Fig. 10—Schematic of the band elimination filter used at branching points of thetype A system. 210 FILTERS FOR CARRIER SYSTEMS 211 Analysis of an insertion loss ladder tilter shows Ihat it may be considereda composite of image sections which are not matched in image a composite filter this means that the effective pass band has been splitinto a number of pass bands each separated by a small attenuation has formulated the process by which these bands can be soarranged that advantage can be taken of the fact that the im
. The Bell System technical journal . o n^W 0 Fig. 10—Schematic of the band elimination filter used at branching points of thetype A system. 210 FILTERS FOR CARRIER SYSTEMS 211 Analysis of an insertion loss ladder tilter shows Ihat it may be considereda composite of image sections which are not matched in image a composite filter this means that the effective pass band has been splitinto a number of pass bands each separated by a small attenuation has formulated the process by which these bands can be soarranged that advantage can be taken of the fact that the image attenua-tions in these bands for small mismatch are comparable to the terminaleffects and that reflection gains up to 6 db are possible in the same combination of these effects, which can be controlled up to and in-cluding the cut-off, gives the insertion loss -filter its improved performancesince the efective and theoretical cut-offs can be made identical, with no. FREQUENCY, f—^ Fig. 11—Non-dissipative filter characteristic obtained by use of Tchebychefif param-eters in pass bands and attenuation band. frequency space needed for the rounding due to the terminal effects inimage filters. In general the mathematical steps required to design a filter by thismethod are as follows: An insertion loss frequency function is chosen whichwill satisfy the filter requirements and will lead to a structure economicalof elements. From this are found the open and short circuit impedancesof the proposed network which is normally of the standard lattice or ladderforms. Finally from these expressions the element values are determined. The particular form of insertion loss design employed for the filter de-scribed here is a special case of the general theory. The filter requirementslent themselves to the use of Tchebycheff parameters simultaneouslyin the pass bands and attenuation band. The application of these param-eters was first described by Cauer.^ The typ
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