106 



Hr.l.L SrSTHM lECIISlCAL JOrRNAI. 



type scries-sluiiit equivalent siruclurc is shown in Fig. 4SB ami con- 

 tains no negative inductances. It will be found that the values 

 chosen correspond to the numerical example of the structure 3 — 3 

 following equation 41. 



2L,= 

 .00448 TT)/" 



L=0ZO0h. 



zc - 

 .0044a mf 



.00577 h, 

 1 (5.0.) ( 



L=.0200h. 



Cs = 00486 mf 



e^y=.OI42hp 



2C - 

 .00446 mf 



2C,=.O0448rT 

 Lj= +.00577 h. 

 C,=.00486 mf 



A B 



Fig. 48— Numerical K.xamplc of a Kilter Section Containing No Negative Inductance 



.\i'im:.\1)1x 



Conditions kor thk Eqiai.ity of the Im.\oe Impkd.xxces of 

 Typu.m. Filter Structures 



It has been stated that the formation of recurrent and composite 

 wave filters is dependent u|M)n the maintenance of equal image im- 

 pedance characteristics (of the sections or half-sections joined) at 

 each junction point throughout the filler. 



.•\ general method of ascertaining the conditions for the equality- 

 of image impedance characteristics will lie demonstrated !)>■ illus- 

 trations from typical pairs of sections. 



Illuslralioii \o. I — Xegalive Inductance in Shunt Arm of One Struc- 

 ture. Consider the filter sections listed as 3-4 (confluent structure) 

 in Table II, and 3-1' in Table III. It will be shown that, under 

 proper conditions, their mid-series image impedance characteristics 

 may be made equal at all fretiuencies. (By reference to the abo\e 

 tables, both sections have mid-.series impedance characteristic No. 13 

 of Fig. 8). 



From equation (6) 

 In l"ig. »".», let 



^1 -/Ji/i+^i/i=jW-i + 



jiaCi 



(100) 



(107) 



