74 



/</■;/./. srsriLM ir.ciix ic.il joikxal 



The dissNinmctriial networks oidinariK I'lniiloNt'd in coni]>()site 

 structures art- usually L t\ i>c networks each of which may be regarded 

 as one-half the corresponding symmetrical 7" or tt network. General- 

 ized forms of such networks are shown in Figs. 14A, B, and C. By 

 joining two of these half-sections, such as are shown in Figs. 14B 



Kig. 14 — (JcniTalizcd Series-Shunt Structure Dividtvl Into Siiiccssive Half-Sections 

 (i,-TyiK-) 



and C, we may form the full T section shown in Fig. 2. Similarly, 

 by joining the two half-sections illiistrateil in Figs. 14A and B, the 

 full w section of l-"ig. 4 results. The transfer constant, 0i,, of a half- 

 section, such as is shown in I'igs. 14A, B, or C, is one-half the transfer 

 constant of the corresponding full section, that is. 



o 6 • u. K' 



(42) 



Hence, the attenuation constant and phase constant of a half-section 

 are, respectively, one-half the attenuation constant and phase constant 

 of a full section. An important relationshi|i between the half-section 

 and the full section, which makes it conxenient to use half-sections 

 in composite wave filter structures, is that the image impedances, 

 Z/, and Z;,, of any half-section are equal respectively to the mid- 

 series and the mid-shunt image impedances of the corresponding 

 full sections. 



A typical example of the method of forming a comjiosite low pass 

 wave filter is gi\en in Fig. 1'), where three half-sections of different 

 types and one full section are combined into a composite lilter. The 

 designations Ih-Iow the diagrams in Fig. 15A refer to the number of 

 full sections and to the ratio/, /(. In a practical filter, the various 

 shunt coiulensersand series coils are combined as illustrated in Fig. l.")B. 



The com|Hisite nature of the attenuation characteristic of the lilter 

 of l"ig. 15B is illustrated in I'ig. Ill, on a non-dissijiatixe basis. In 



