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Mu-derived Communications Filter

IP.com Disclosure Number: IPCOM000062251D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Conner, DE: AUTHOR

Abstract

This article describes a lowpass filter which allows telephone wires to transmit data at multi-megabits per second rate without undue radiation. The basic lowpass filter includes a transformer (T) coupled by a common mode conductor (L) to an RC network.

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Mu-derived Communications Filter

This article describes a lowpass filter which allows telephone wires to transmit data at multi-megabits per second rate without undue radiation. The basic lowpass filter includes a transformer (T) coupled by a common mode conductor (L) to an RC network.

The design of the lowpass filter is based upon the relative permeability and frequency relationship of a given magnetic core material. To take full advantage of this relationship, the primary and secondary windings of the transformer should be configured so that the primary and secondary coupling is essentially via the core material for any frequency of interest. is accomplished by providing maximum separation of the windings on the core. In a transformer so designed, as the relative permeability of the core approaches unity with increasing frequency, the degree of coupling between primary and secondary windings is essentially that of an air core device with a coupling determined primarily by the distance between the winding

Fig. 1 depicts a Mu-derived lowpass filter with transformer T1, a common mode inductor L1 and an R1C1 network across the output. Capacitor C1 is chosen to provide for a sharper rolloff characteristic beyond the filter rate frequency. Its value is dependent upon the magnitude of the transformer leakage inductance and the desired cutoff frequency. Resistor R1 is used t provide the necessary damping of the transient response of transformer leakage inductance and c...