244 



BELL SYSTEM TECHNICAL JOURNAL 



f = V/a/ft. The impedance functions Z^ and Zy are now readih' 

 found by means of (1) and (2), and with the help of Foster's formula 

 the element values can be obtained. These are shown in Fig. 18. 



Li 



L2 



Lz 



L4 



Ls 



L, 



L7 



is 



L9 



Lio 



Ln 



Ln 



Ll3 



0.0675 mh. 



0.6529 mh. 



0.1958 mh. 



0.1770 mh. 



0.1330 mh. 



0.0404 mh. 

 35.66 mh. 



0.1620 mh. 



0.20.21 mh. 



1.335 mh. 



0.1097 mh. 



0.1089 mh. 

 35.86 mh. 

 Fig. 18- 



C, 

 C2 

 C3 

 C4 



a 



C, 

 Cg 

 C9 

 Cio 



Cu 



C12 



= 3.035 mf. 

 = 0.2810 mf. 

 = 0.8622 mf. 

 = 0.8801 mf. 

 = 1.085 mf. 

 = 3.325 mf. 

 = 0.0046 mf. 

 = 1.182 mf. 

 = 0.8703 mf. 

 = 0.1214 mf. 

 = 0.9112 mf. 

 = 1.276 mf. 



Ci3 = 0.0046 mf. 

 -Band pass filter. 



This example illustrates the way in which the analysis may be 

 applied to a typical problem in network design. The practical design 

 would not ordinarily be complete at this point, however, since, as was 

 mentioned previously, it is seldom desirable actually to construct the 

 network as a single symmetrical lattice. Improved stability with 

 respect to variations of the elements from their design values is 

 obtained if the lattice is resolved into its components, that is, the 

 elementary lattice sections which when operated in tandem have the 

 same transmission properties. This question is discussed in a recent 

 paper.^ Furthermore, unbalanced structures equivalent to the sym- 

 metrical lattice but employing fewer elements are known,^* and expense 

 can usually be reduced by resorting to one of these. 



^ H. W. Bode, loc. cit. It may be interesting to observe that in the terminology 

 of that paper the elementary constituents of linear phase shift filters are usually 

 complex m sections. 



*^ A linear phase shift lattice filter cannot, of course, be constructed as a sequence 

 of 11 or T sections, but equivalences in generalized bridged-T configurations exist. 

 General equivalences in configurations employing ideal transformers are familiar in 

 the literature. .See, for example, Cauer, loc. cit., or Jaumann, E. N. T., July, 1932, 

 p. 243. 



