GB614720A - Improvements in and relating to electric filter circuits - Google Patents

Abstract

614,720. Impedance networks. GENERAL ELECTRIC CO., Ltd., and LEVY, M. M. July 22, 1946, No. 21825. [Class 40 (viii)] A filter network has a bridging network connected between points thereon, the difference between the time delay along the filter network between the points and that along the bridging network being substantially equal to the periodic time or an integral multiple of the damped oscillation generated at the output terminals of the network in response to a short pulse applied to the input terminals of the network. The result of this is to superimpose an advanced and delayed train of oscillations on the parent oscillation and permits, among other things, of making the output oscillation, from a short pulse, symmetrical. This is a condition that renders the phase frequency characteristic of the filter linear. Another use of the method of the invention is in producing a distortion correcting network. More than one bridging network can be used involving various multiples of the periodic time. In the example shown, the terminals of the filter are T1 and T2 and two bridging arrangements, consisting simply of condensers C3 and C4, are used. In this case, the filter sections are prolonged beyond the output terminal so as to delay both of the components introduced by each bridge. The lumped impedance circuits shown may be replaced by coaxial lines.