98 



FELL SYSTHM TliCllXICAL JOURNAL 



Types of Sections Obtainable Whose Series-Shunt Equivalent Sections 

 Contain Xegative Inductances. It lias already been pointed out that 

 the following meshes of Fig. 5 may be at least partly composed of 

 mutual inductances: — Nos. 1, 3, 4, 5a, iib, la, lb, 8a and 8fc. When 



^^j,,,^ ^^sm^^ ^^ '^iHH^> <ifl> 



>xftfllbHl-Lj- ->Jiaay|,^ — KMiJyjH-^ tZ||_[^^]J~ 



Kig. 42 — Two-Terminal Reactance Meshes of Four or Less Elements, Containing 

 Negative Inductance and Effectively Realizable Within Filter Sections . 



the connection of the coils is such that the mutual inductance effectively 

 results in |)roducing a negative arm in the mesh in which the mutual 

 inductance exists, the meshes may be shown as illustrated in Kig. 42. 

 The reactance-frequency characteristics of these arms arc given in Fig. 

 43. It is to be noted that two general forms of reactance characteristics 

 exist for arms oa' and o6' and that one form of reactance characteristic 



5'b 



FiK- -43 — Reactance-Frequency Characteristics of the Meshes of Fig. 42 Shown in 

 Symbolic Form 



is common to the two reactance arms. This dualit\- of characteristic 

 arises from the fact that the arms each contain two inductances, one 

 positive and one negative, and that the general shape of the reactance 

 characteristic is determined b\' the predominance of either the posi- 

 tive or the negative inductance. The characteristic which is peculiar 

 to arm ha' occurs when the negative inductance of this arm is smaller 

 than the positive inductance. Likewise, the characteristic peculiar 

 to arm 56' occurs when the negative inductance of this arm is larger 



