IK.tXSMlSSlOX CH.IR.tCTERlSTlCS ()/• U'.H'F.ril.lliRS 575 

 Gei\eral Form of I'miismission Loss Formula 



I'orimil.io (2) and (3) corresponding to l-iKs. 2 and '.\ m.iy \k coni- 

 l)iiK(l. If (3) is written in the general form 



2RI/E=FtFaFiFr, (5) 



we (ibtain with (2) 



e-t- = i 2RIiE \ = e-(t.+L.+t»+i,)^ (0) 



wlure the four factors comprising the current ratio 2RI E are 

 F, = f-^ = the transfer factor between terminals a and b; 



F.=-~r-. — ' , "'" = the terminal factor at terminals a; 



{Wa+Za) E 



,, 2\/WkR I , ■ , f . . . • 1 A 



^6 = /,,r =thc terminal factor at termmals o; 



1 — Torje 

 at terminals a and b where the current reflection coefficients are 



F, = -, ::jr~ ^^'-' interaction factor due to repeated reflections 



Wa-Za . Wi-Zb 



'''^w:+Za^'"^"'=w;+Zb' 



and the transmission losses corresponding to the absolute values of 

 these factors are called, respectively, 



L( = the transfer loss; 



La. Z.i, = the terminal losses at terminals a and /;; 



and Lr = the interaction loss. 



The total transmission loss is the sum of these four losses, thus, 



L = U + La + Lb + Lr. (7) 



The relative importance of the three t\pes of losses, transfer, 

 terminal, and interaction, is usually in the order given. Hence, as 

 a first approximation the transmission loss of a composite wave-filter 

 is given by the transfer loss, /-,, but the error due to the omission of 

 the other losses is often considcraHle. .\ second approximation is 

 obtained by including the terminal losses, La and Lj, and for many 

 purposes this is surticiently accurate. The final step for accuracy is 

 the further addition of the interaction loss, L„ whose effect on the 



