. The Bell System technical journal . ystem is stable it will be foundthat A^ will have the same value in the bridged T structure as it hadfor the single series negative impedance. Thus, if A^ is the same in the case of the bridged T as in the singleseries impedance, the gain advantage can be obtained by comparingformulas on Figs. 12 and 13 from w^hich it can be seen that the gainadvantage of the bridged T is equal in db to 20 logio [1 + (A^/2)]. If asingle series repeater can be used in a line to give an insertion gain of6 db {N = 1) then a bridged T can be used to provide 20 logio (1 + )o
. The Bell System technical journal . ystem is stable it will be foundthat A^ will have the same value in the bridged T structure as it hadfor the single series negative impedance. Thus, if A^ is the same in the case of the bridged T as in the singleseries impedance, the gain advantage can be obtained by comparingformulas on Figs. 12 and 13 from w^hich it can be seen that the gainadvantage of the bridged T is equal in db to 20 logio [1 + (A^/2)]. If asingle series repeater can be used in a line to give an insertion gain of6 db {N = 1) then a bridged T can be used to provide 20 logio (1 + )or db additional. Thus, in this case the series repeater gives 6 dbgain as compared to 6 + or db for the bridged T. These gains aretheoretical; in actual lines with simply constructed repeaters the com-parison may not be c^uite so favorable to the bridged T. THE NEGATIVE IMPEDANCE CONVERTER So far the discussion of the E2 and E3 repeaters has been in terms ofa black box which translates a positive impedance into a negative. INSERTION LOSS _ o„ , „^ I;IN DECIBELS ^O LOG,o— INSERTION GAIN _ -,„ , nr -^3 IN DECIBELS ^0 LOG,o -^ = -20 LOGio- 20 LOGio (b) 2Zo (c) Fig. 1,3 —• Insertion gain of the E2 repeater. NWiATIVE IMPKDAXCK TKLKrHOX K UKlKATKRS 1073 impedance tlirouiih a multiplyiiiu; and pluise shift operation. It will hointer(>stinj>; to (\amin(> tlicsc boxes to see what faetors determine theircharacteristics. THE E2 CONVERTER The E2 negative impedance converter is the same as the El. As dis-cussed elsewhere^ it can be represented schematically as in Fig. 14(a)and also in terms of the eciuivalent circuit of Fig. 14(b) if the coils areassumed to be ideal. The conv(M-t(M- performs much like a impedance seen through it is not only transformed in magnitude bythe ratio of ] 1 — jU|8 1 to | 1 + m 1 it is also modified by the phase shiftof this factor which over the operating band of freciuencies approximates180 degrees. The symbol m s
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
