A METHOD OF IMPEDANCE CORRECTION 



821 



is proportional to frequency, the desired susceptance curves will be 

 recognized as being approximately those which would be obtained 

 from tuned circuits resonating slightly beyond the cutoff. Since a 

 tuned circuit can be considered as being a series combination of the 

 series and shunt impedance of the "constant-^" filter, any such 

 correcting network designed for a low-pass filter can be adapted to 



1.6 



1.4 



1.2 



o 

 N 1.0 



z 



< 0.8 



0. 

 UJ 



o 



D 

 if) 



0.6 



0.4 



0.2 



0.2 



0.4 0.6 



X 



0.8 



1.0 



Fig. 11 — Susceptance correction of a 3-branch termination. 



I — Desired susceptance. 

 II — Susceptance actually obtained. 



another type of "constant-^" structure by replacing inductances and 

 capacities by the homologous impedances of the other filter. 



This simple combination of series and shunt impedances is, as we 

 have previously seen, capable of giving exact susceptance correction 

 when the conductance controlling network contains only one branch, 

 but it is not, in general, sufficient for 2 and 3 branch networks. Indeed, 

 no physically realizable reactive network will cancel the susceptance 



