GB554329A - Impedance hatching networks for use in electrical transmission systems - Google Patents

Abstract

554,329. Impedance networks. STANDARD TELEPHONES & CABLES, Ltd. July 17, 1942, No. 9967. Convention date, July 25, 1941. [Class 40 (iii)] A matching network for coupling two unequal impedances R 1 , R 2 comprises a series arm consisting of two closely-coupled inductances L 1 , L 2 in series-opposing relationship and a shunt arm consisting of a condenser C and resistance R in parallel. The impedance R 1 may be a transmission line, which the network may be designed to match over a wide band of frequencies, while the impedance R 2 may be an amplifier. Since the coupling is mainly resistive at low frequencies, and mainly inductive at high frequencies, the conditions for matching at those frequencies are R=R 1 R 2 / (R 2 -R 1 ) and L 1 /L 2 =R 1 /R 2 , while the condition for matching at the intermediate frequencies is In addition L 1 may be chosen so that the gain characteristic serves to some extent to neutralize attenuation distortion in the transmission line. The network may be constructed in balanced form as shown in Fig. 3 for use with amplifiers working in push-pull. Condensers C 1 , C 2 prevent the flow of direct current through the network, and the plate current of the amplifiers may be derived from the mid-point of resistances R 3 , R,. A shunt condenser C 3 forms a low-pass filter section with the leakage inductance of L 1 , L 2 , while series inductances L 3 , L, provide another similar section in conjunction with capacity component of the impedance R 2 .