GB776755A - Electrical filter network - Google Patents

Abstract

776,755. Filter networks. BELLING & LEE, Ltd. Dec. 8, 1955 [Oct. 6, 1954], No. 28747/54. Class 40 (8). [Also in Group XL (c)] A network for coupling two transmission lines carrying signals of different frequencies to a common transmission line consists of two sections, either of which is a " T " or " # " network, having a common series or shunt limb, each section having either an open circuiting element in a series limb thereof or a short-circuiting element in a shunt limb. In one embodiment the higher frequency signal passes to the common transmission line via connections C, D and a " T " network comprising series capacitors C4, C5 and a shunt (which is inductive at the higher frequency) formed by a capacitor C2 in series with an inductance L2. The lower frequency signal is fed to the common line via connections A, B and a " # " network comprising a condenser C3, an inductance L1 in parallel with a condenser C1 to form a combination which is inductive at the lower frequency and an open circuit at the higher frequency, and the condenser C4 which is connected to the point D through the combination C2, L2 which is a short circuit at the lower frequency. In further embodiments the coupling network comprises, respectively, (a) a lower frequency " T " network and a higher frequency " # " network; (b) two " T " networks; (c) two " # " networks having a common series capacitor-inductance combination; and (d) two " # " networks having two common series capacitor-inductance combinations. The network may be used for the passage of signals from television or radio aerials operating at different frequencies to a common receiver, or it may be used to separate two signals of different frequencies.