US2297215A

US2297215A - Electric filter device

Info

Publication number: US2297215A
Application number: US272996A
Authority: US
Inventors: Hagen Wolfgang
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-05-11
Filing date: 1939-05-11
Publication date: 1942-09-29
Anticipated expiration: 1959-09-29
Also published as: CH211213A; FR854443A

Description

Sept. 29, 1942. w. HAGEN 2,297,215 ELECTRIC FI'LIER DEVICE Filed May 11, 1959 Fly. 1

lnvenfohm wlfqany Hqye/I Patented Sept. 29, 1942 ELECTRIC FILTER DEVICE Wolfgang Hagen, Berlin, Germany; vested in the Alien Property Custodian Application May 11, 1939, Serial No. 272,996 In Germany May 11, 1938 2 Claims. (Cl. 17844) This invention relates to electric filter devices, particularly of the type adapted for use in Wireradio systems.

When telephone or other electric communication lines are employed for transmitting intelligence or other performances by high frequency carrier currents, a large number of electric filters is required for impressing these high frequency currents upon such lines and for separating the high frequency carrier currents from the low frequency rnessage currents in the receiving positions. The type of filters customarily used in such wire-radio systems comprises one high-pass filter branch and one low-pass filter branch, the latter in the shape of a coil circuit.

It has heretofore been proposed tosimultaneously employ the high frequency coupling condensers of such filters as members of the coil circuit of the low-pass filter branch, that is, as the shunt condensers thereof. Although this facility actually has involved a considerable structural simplification, it has been found by tests that the attenuation characteristic obtained by lowpass filter branches of the kind in which one inductance coil is inserted in series with each conductor of a two-wire line and in which the high frequency coupling condensers simultaneously act as the shunt capacities of the low-pass filter branch does not involve the desired steepness, from which follows that the filter does not present sharply defined cut-off frequencies.

My invention consists in certain features of novelty which will be readily understood from the following description and be pointed out in the appended claims, reference being made to the accompanying drawing in which Fig. 1 is a diagram explanatory of this invention, Fig. 2 schematically shows an electric filter according to my invention, while Fig. 3 shows one embodiment for realizing the present invention.

It is one object of this invention to overcome the disadvantage above mentioned and to provide means in filter devices of the kind referred to above which allow the attenuation characteristic thereof to get the desired shape.

According to a further feature of this invention, the inductances inserted in series with each of the conductors of a two-wire line are so tuned as to act as resonance circuits.

This effect is achieved according to still a further feature of my invention by forming the inductance coil in two or more individual layers of turns and to connect these layers in series with each other. This facility considerably increases the self-capacity of the inductance coil. It is thus possible by suitably adjusting the self-capacity and the inductance value of such coil to so adjust the resonance frequency of the coil member that this frequency coincides with an ascending branch of the filter attenuation characteristic. Careful tests which have been carried out with a filter device designed in accordance with the above disclosed rule gave the dash curve B of Fig. 1, in which the attenuation is plotted in the ordinate in response to the frequency as represented by the abscissa. The curve A, by comparison, shows the attenuation characteristic of the heretofore known filters.

An electric filter device, and more particularly the low-pass branch thereof is embodied in Fig. 2. The references a. and b denote inductance coils, each connected in series with one conductor of a two-wire communication line. The high frequency message currents are applied tothe outgoing end of a telephone subscribers line A B through a transformer D and the high frequency coupling condensers C which act as shunt capacities of the low-pass filter branch. The low frequency message curents to be transmitted to the subscribers line A B are impressed upon the low-pass filter at the terminals C D. The self-capacitance of the coils a and b is very large, and such high capacitance value will be obtained by arranging the respective windings in the form of two or more separate layers of turns, as shown at E and F of Fig. 3, and by connecting each separate one of said layers in series with'one another. The windings of the inductances are preferably associated with a core of iron.

What is claimed is:

1. An electric filter device having a high-pass branch and a low-pass branch the latter in the shape of a coil circuit comprising, inductance coils, each consisting of a plurality of windings arranged in individual parallel layers and connested in series with each other to artificially enhance the self-capacitance of said coils for selectively tuning them to any desired resonance frequency.

2. Electric filter arrangement comprising input and output circuits, and a low-pass filter, said filter comprising a first coil connected between one side of said input circuit and one side of said output circuit, a second coil connected between the other side of said input circuit and the other side of said output circuit, and at least one condenser shunted across said output circuit, each of said coils comprising at least two windings wound on each other and connected in series.

WOLFGANG HAGEN.