MUTUAL IKinCTAXCIi IX llAfi: Ill.TI-.RS W 



I'liiinnl.u- i'2'2) ,iiul ['2'.i) .in- t-xprf^cd in M,i|>ici> .iikI ciniil.ir r.iili.iiis, 

 ri's|Hrli\i'ly. They art- ri'|>ivsi-iit«.'<l in I'U niu\ in nuii.ins \>y f.iniilics 

 <»f fiirvTS siirli as art- shown in l-i^s. 1 1 and 12. 



A i-omi-nii'Mt ratio wliich i-xpresst-s tlie dissipation in any rrartance 

 lUiinnl is the al)solutc r.itio, d, of its effective resistance to its re- 

 actance. Ill the case of a coil, d = R/Lw while in the case of a con- 



di-nser d = RCui. The reciprocal ratio Q= y = -jr =-57^- has al.so l)een 



widely used as a nieasure of dissipation in reactance elements. The 

 ratio (/ or Q will not, in general, Ix- constant over a wide fre(|iiency 



Fig. li — Typical Band Pass W'.ivc Kilter .Section (.Mid-Series Termination) 



range. If the value is known at an iniixirtant frequency in the trans- 

 mission range, it may ordinarily be regarded to hold for the rest of 

 the transmission range. The effect of dissipation on the attenuation 

 constant is most important in the transmission band, where the at- 

 tenuation constant would Ix; zero if there were no dissipation. Its 

 effect is most pronounced in the neighborhood of the cut-off fre- 

 quencies where the transmission bands merge into attenuation bands. 



In the attenuation bands, the general effect of dissipation is negli- 

 gible. It largely controls, however, the value of the attenuation 

 constant at those frequencies at which infinite attenuation would 

 occur if there were no dissipation. The effect of dissipation upon 

 the phase constant is most pronounced in the neighborhood of the 

 cut-off frequencies where resistance rounds off the atjriipt changes in 

 phase which would otherwise occur (see Fig. 12). 



Characteristics of a Typical Filter. In order to illustrate specifically 

 the principles employed in filter design, consider as an example the 

 band pass structure 3 — 3 of Table II. This structure is illustrated 

 in Fig. 13. It will be assumed that the dissipation in the coils cannot 

 be neglected, but that the dissipation in the condensers is of negligible 



