GB380101A - Method of disturbance prevention in high frequency electrical transmission systems and means therefor - Google Patents

Abstract

380,101. Inductances. STANDARD TELEPHONES & CABLES, Ltd., Connaught House, Aldwych, London.-(Lair, J. J. B. and Perroux, G. E. M. ; 46, Avenue de Breteuil, Paris.) April 1, 1931, No. 9864. [Class 37.] A transmission line TL, Fig. 2, coupling apparatus A, B, is given a high impedance to longitudinal currents by coiling the conductors to form an inductance L, a third conductor W being closely associated with the line to form with condenser C an anti-resonant circuit effectively in series in the circuit comprising the two wires of the line. The third conductor may take the form of a metal tube t, Fig. 19, coiled as an inductance and containing the two wires of the line TL, the condenser being connected to the tube extremities; alternatively the tube may form one of the line conductors or two concentric tubes with a central metal conductor may be employed, Figs. 3 and 4 (not shown). In addition to the use of a tubular inductance such as t, Fig. 19, additional series inductances of metal tubular form may be provided wound close together on an earthed former to provide a drain circuit to earth through the capacity between the wires in the tube and the tube itself, Fig. 6 (not shown). An alternative arrangement of a shunt circuit across the transmission line comprises a pair of wires twisted together, short-circuited and earthed at one quarter wavelength at the signal frequency ; the twisted portion may be coiled to form an inductance and the extremity is then earthed through a condenser, Figs. 8 and 9, (not shown). In the latter case the coiled portion and condenser should be screened. An alternative arrangement which dispenses with the necessity of screening is shown in Fig. 10, in which the two wires a, b of the shunt path are coiled into an inductance L with a third wire c. The wires a, b are short-circuited at Q such that the electrical length of PQ is an odd number of quarter wave-leng thsat the signal frequency; all three conductors are short-circuited and earthed at R, the length PR being a whole number of half wavelengths at the longitudinal current frequency. The invention is specially applicable to aerial feed lines in directional wireless and may also provide a method of reception of two transmitted frequencies, simultaneously or otherwise.