GB803435A - Improvements in or relating to electric direction couplers - Google Patents

Abstract

803,435. Directional coupling circuits. TELEFONAKTIEBOLAGET L. M. ERICSSON. Nov. 4, 1955 [Nov. 4, 1954], No. 31649/55. Class 40 (8). A directional coupler comprises two conductors each having a number of spaced-apart sections 111, 4111, Fig. 10 (a theoretical diagram), juxtaposed in pairs and connected by loops of equal electrical length, the loops in one conductor connecting the end of each section with the beginning of the next posterior section and in the other conductor connecting the end of each section with the beginning of the next anterior section. The conductors are parts of transmission lines, e.g. the internal conductors of a piar of coaxial lines. It is stated in the Specification that the ratio of the distributed magnetic and electric coupling between the conductors with the above arrangement is - 1 and that, if the four pairs of terminals of the coupler are correctly terminated, no coupling exists between pairs of terminals at the same extremity of the coupler. In one construction (Fig. 4) the inner conductors 11, 41 of coaxial sockets 13, 43 are wound in opposite senses in the grooves of a dielectric core, the conductors crossing each other twice in each loop. Strips 12 of insulating material are provided between the conductors at the crossing points. The outer conductors of the coaxial sockets 13, 43 may be connected to a shield surrounding the windings (Fig. 6, not shown) or to a conductor extending along the axis of the dielectric core (Fig. 7, not shown). In another construction (Fig. 8) the two conductors are wound in the same sense on adjacent formers which are surrounded by an earthed conductor 17. The degree of mismatch between a generator and a load connected respectively to terminals 43, 43, Fig. 4, may be determined by measuring the voltages at the terminals 13, 13. The ratio of the voltages gives the reflection coefficient of the load as a function of frequency. In the modified circuit of Fig. 3 whichincludes a source 2, a load 3, two directional couplers 5, 5<SP>1</SP>, meters 6<SP>1</SP>, 7 and matched terminations 10, the expression giving the reflection coefficient in terms of the ratio of the measured voltages includes no frequency terms. A brief mathematical discussion of the circuits is given in the Specification.