Impedance blocking filter circuit

Abstract

An impedance blocking filter circuit is provided for use in telecommunication systems for interconnecting between incoming telephone lines and customer's terminal equipment so as to unconditionally block impedances above 20 KHz due to the customer's terminal equipment from an ADSL network unit and / or home networking interface unit. The filter circuit includes first, second, and third inductors connected in series between a first input terminal and a first common point. A first resistor has its one end connected also to the first common point and its other end connected to a first output terminal. Fourth, fifth and sixth inductors are connected in series between a second input terminal and a second common point. A second resistor has its one end also connected to the second common point and its other end connected to a second output terminal. A capacitor has its ends connected across the first and second common points. In other aspects, the filter circuit also includes switching means for eliminating shunt additive capacitance and / or correction circuit means reducing significantly return loss.An impedance blocking filter circuit is provided for use in telecommunication systems for interconnecting between incoming telephone lines and customer's terminal equipment so as to block impedances above a desired frequency range due to the customer's terminal equipment from a DSL network unit and / or home networking interface unit. In one exemplary embodiment, the filter circuit includes first, second, and third inductors connected in series between a first input terminal and a first common point. A first resistor has its one end connected also to the first common point and its other end connected to a first output terminal. Fourth, fifth and sixth inductors are connected in series between a second input terminal and a second common point. A second resistor has its one end also connected to the second common point and its other end connected to a second output terminal. A capacitor has its ends connected across the first and second common points. In other configurations, the filter circuit also includes switching means for eliminating shunt additive capacitance and / or correction circuit means reducing significantly return loss.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present invention is a continuation-in-part application based on prior application Ser. No. 09 / 195,222 filed on Nov. 19, 1998, and entitled “Impedance Blocking Filter Circuit.”The present application is a reissue of U.S. Pat. No. 6,181,777 issued Jan. 30, 2001 of the same title, which is a continuation-in-part of application Ser. No. 09 / 195,522, now U.S. Pat. No. 6,188,750. This application is also related to co-pending reissue application Ser. Nos. 10 / 737,736 filed Dec. 12, 2003, 10 / 366,656 filed Feb. 12, 2003, 10 / 408,030 filed Apr. 3, 2003, and 10 / 748,729 filed Dec. 29, 2003, all of the same title. <?insert-end id="INS-S-00002" ?>BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates generally to telecommunication systems and more particularly, it relates to an impedance blocking filter circuit used in telecommunication systems for interconnecting between incoming telephone lines from a telephon...

AI Technical Summary

Benefits of technology

[0012]Accordingly, it is a general object of the present invention to provide an impedance blocking filter circuit which effectively and efficiently eliminates ADSL interference caused by telephone terminal equipment.

Problems solved by technology

However, since one or more telephone subscriber terminal equipment such as telephone sets, facsimile machines and / or answering devices are also connected to the same incoming telephone lines via internal house wiring, ADSL interference problems may be caused by the terminal equipment which can significantly limit or reduce the data rate.

Images