PHASE DISTORTION AND PHASE DISTORTION CORRECTION 213 



alternating the coil and lattice loads affords some improvement '"n 

 this respect. Another possible means of reducing the time interval 

 T — To at the higher frequencies is to reduce the spacing of the 



L/2 



Fig. 



L/2 



13b — Section of non-dissipative lattice loaded line. L = .066 henry, Co = .0705 

 microfarad, r = .50 (19 gauge cable). 



loading coils on the ordinary loaded line, keeping the attenuation per 

 mile the same as before. As this change increases N and fc in the 

 same ratio, the effect is to reduce T — To. 



3. Lattice Type Terminal Network 

 Instead of being used to replace the coil unit in the long periodically 

 loaded line for the purpose of reducing the phase distortion, the 

 lattice network ^^ may be applied to the coil loaded line as a terminal 

 phase compensator, a use to which it is peculiarly adapted by virtue 

 of the nature of its characteristics.^*^ These have been known for 

 many years. The ideal non-dissipative simple lattice type recurrent 

 network, shown in Fig. 14, with series inductance L and crossed 

 capacity C per section, has a pure resistance characteristic impedance 



a phase angle 



K = ^ILIC 

 <l)ico) = 27Vtan-i(«V^/2), 



r27) 



(28) 



where N is the number of sections, and zero attenuation for all fre- 

 quencies.^^ These relations readily follow from the general formulas 

 (32)-(35) given below. The phase angle (Fig. 15), therefore, is 



^^ The possible usefulness of the lattice network as a phase shifting device was 

 pointed out in a general way by G. A. Campbell. See references 12 and 13. 



1^ In this connection see references 12, 13 and 14 to the work of Karl Kupfmuller 

 of the Siemens-Halske Company of Berlin, who independently applied the simple 

 lattice network in the same way. 



^' See reference 13. 



