GB615355A - Transmission line bridge circuits - Google Patents

Abstract

615,355. Impedance matching. STANDARD TELEPHONES & CABLES, Ltd. June 28, 1946, No. 19415. Convention date, July 7, 1945. [Class 40 (viii)] In a system for intercoupling one or more sources such as 10, Fig. 1, to one or more loads 11, 12 comprising a bridge network 1 ... 4 of transmission lines, one of which contains a transposition, the sources comprise a wide band of frequencies and improved matching over the whole range is effected by giving the transmission lines an electrical length of 90 degrees at the mid-band frequency. The characteristic impedances of the transmission lines are so related to that of the load lines 7, 8 and the feeder line 6 as to produce perfect matching at two frequencies equally spaced on either side of the mid-band frequency. Further improvement may be effected by interposing impedance transforming sections 13 ... 16, Fig. 2, between the sources or loads and the bridge, the sections having a length equal to that of the arms 1 ... 4. Then by making the characteristic impedance of the feed lines 6 ... 9 greater than that of the sections 13 ... 16, deviation from the mid-band frequency causes a reactive component to be introduced by the bridge arm 3 which is partly neutralized by the reactive component of opposite sign introduced by the combination of lines 7, 14. By suitably relating the above characteristic impedances to that of the bridge arms, substantial matching may be obtained at three different frequencies. Specification 491,359 is referred to.