(A liF.I.I. SYSTEM 7 ECIIXIC.il. .lOCR.WIL 



filters (having; l\v(» pass liaiuls ami onK' out' attenuation band). Their 

 attenuation constant and phase constant characteristics, with respect 

 to freqiiencN-, arc shown s\ niholically in Fig. 7. The mid-series and 

 mid-shiMit iniajje iniiK-Klance characteristics with respect to frequency 

 are shown in Ki>j. 8. In Table II, the figure at the head of each 

 column indicates the reactance mesh in Fig. 5 which is used for Zi 

 (scries impe<iance) and the figure at the left of each row indicates 

 the mesh in Fig. 5 which is used for Zj (shunt impedance). The 

 figures in the squares of the table denote, reading from left to right, 

 the propagation characteristics (attenuation and phase), the mid- 

 series image impcilance, and the mid-shinit image impedance, re- 

 spectively, as shown in Figs. 7 and S. 



For example, the filter corresponfiing to the third column and to 

 the fourth row (3 — 4) has a series arm composed of an inductance 

 in series with a capacity as indicated by mesh 3 of Fig. 5, and has a 

 shunt arm compo.si'd of an inductance in parallel with a capacity, 

 as designated b>' mesh 4 of Fig. 5. The attenuation constant and 

 phase constant characteristics of this filter are shown symbolically 

 by diagram ."> f)f l-ig. 7, while the mid-series and mid-shunt image 

 impetlances are indicated, respecti\ely, by diagrams 13 and 14 of 

 Fig. 8. The s>nil)olic nature of the diagrams lies in the fact that 

 the abscissae of each diagram co\er the frequency range from zero 

 to infinit\-, and the ordinates of Figs. 7 and 8 cover the attenuation 

 constant and the impedances from zeio to infinity. For example, 

 the structure lited has an attenuation cijnstant characteristic (diagram 

 o of Fig. 7) com|K>sed of a transmission band lying between two at- 

 tenuation bands, the attenuation constant being infinite in one of 

 them at zero frequency, and in the other, at infinite frequency. The 

 phase constant of this structure is — »• radians in the lower of the two 

 attenuation bands, increases from —ir to +7r riulians in the trans- 

 mission band (passing through zero), and is -f ?r radians throughout 

 the up|)cr of the two attenu.ition bands. The mid-series image 

 imiKxIance (diagram 13 of Fig. 8) is a negative reactance in the lower 

 of the two transmission bands, decreasing from infinity, at zero fre- 

 (|uency, to zero at the lower cul-ofT frecjuencN-, is a imre resistance 

 throughout the transmission band, ami is a positi\e reactance, increas- 

 ing from zero to infinity, in the upper of the two attenuation bands. 

 The mid-shunt image imindance characteristic (diagram 14 of Fig. 8) 

 is reciprocal in nature, for this structure, to the mid-series image 

 impc<Iance characteristic. This ty|)c of filter also possesses, in the 

 general case, ;i double banti pass attenuation characteristic and cor- 

 res|X)nding phase and im|K-<lancc characteristics. A discussion of such 



