128 



BELL SYSTEM TECHNICAL JOURNAL 



with inductances imposes limitations upon the filter characteristics 

 obtainable. Capacitances may be designed so that the energy dis- 

 sipation is small and negligible as compared to that in the inductances. 

 With ideal reactance elements entirely free from dissipation, filters 

 might be designed for any band width with as little loss in the band as 

 wanted and at the same time frequencies might be rejected outside 

 the band by any amount desired, no matter how near such frequencies 



c^VW 



Fig. 4 — It does not alter the transmission properties of a network such as shown 

 in Figure 4A to remove the impedances in shunt and outside the lattice and replace 

 them by impedances of equal magnitude in shunt across each lattice arm nor by 

 removing the impedances in series with the lattice and replacing them by series 

 impedances inside the lattice of twice the magnitude of those removed. 



were to the edges of the transmitting band. Of course the sharper the 

 filter cut-offs, other requirements being the same, the more complex 

 the filter structure would be even neglecting dissipation. The greater 

 the dissipation in the filter elements, the greater the loss in the trans- 

 mitting range of the filters and the greater the number of cycles 

 required for this loss to rise from the relatively low and uniform loss 

 in the transmitting band to the high loss wanted outside the band. 

 In the design of channel filters for carrier systems, the presence of 



