VARIABLE EQUALIZERS 



241 



produced in the networks we have already considered since, as equation 

 (8) shows, the variable attenuation will change sign if the phase shift 

 of the auxiliary network is allowed to increase beyond 45°. 



In the fourth structure, shown by Fig. 10, both ^o and (^ are variable. 





ZmZ 



11^21 



^Ro^^ 



Wo 



Fig. 10 — A variable equalizer with a constant ratio between the reference loss 

 and the variable characteristic. 



Their ratio, however, is constant, and the overall loss characteristic 

 of the structure is therefore proportional to some fixed characteristic 

 at all settings of the variable resistance. This property suggests that 

 the network may be of interest for such applications as the equalization 

 of varying lengths of a given transmission line. 



