214 BELL SYSTEM TECHNICAL JOURNAL 



Aside from its purely theoretical interest, the analysis leads to two 

 results of immediate practical value. The first is the introduction of 

 new characteristics by the complex m and A-derived sections. The h- 

 derived structures can be dismissed briefly. They are chiefly of inter- 

 est for their impedance characteristics, which resemble those found in 

 symmetrical lattices. They allow us, however, to extend these imped- 

 ances to unsymmetrical structures and they also allow us to extend 

 considerably the range of impedances, even of symmetrical structures, 

 which can be realized in the ladder form. The complex m structures, 

 on the other hand, are chiefly of interest for their novel phase and 

 attenuation characteristics. The novel phase characteristics are par- 

 ticularly important since the elementary constituents of the linear 

 phase shift filters described in the accompanying paper usually turn 

 out to be complex m sections. 



The second general result is an increase in our knowledge of the 

 relations existing between filters of different physical configurations. 

 This last point is particularly important because it allows us to convert 

 filters from one type of configuration to an equivalent type which may 

 be better suited for purposes of practical construction. For example, 

 it allows us to convert the general lattice filter, which is very convenient 

 for theoretical purposes but is very difficult to build practically, into a 

 composite of simple lattices and ordinary ladder sections. 



