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, correction circuit means reducing significantly return loss, and switch suppression circuit means for eliminating transients.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present invention is a continuation-in-part application based on prior Ser. No. 09 / 370,137 filed on Aug. 9, 1999, which is, in turn, a continuation-in-part application based on parent application Ser. No. 09 / 195,522 filed on Nov. 19, 1998, and entitled “Impedance Blocking Filter Circuit.”The present reissue application is a continuation application of prior application Ser. No. 10 / 408,030 filed Apr. 3, 2003 of the same title, which is a reissue of U.S. Pat. No. 6,212,259 issued Apr. 3, 2001 of the same title, which is a continuation-in-part application based on prior Ser. No. 09 / 370,137 filed on Aug. 9, 1999, now U.S. Pat. No. 6,181,777, which is, in turn, a continuation-in-part application based on parent application Ser. No. 09 / 195,522 filed on Nov. 19, 1998, now U.S. Pat. No. 6,188,750. <?insert-end id="INS-S-00001" ?>BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates generally to telecommu...

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.

[0015]It is still another object of the present invention to provide an impedance blocking filter circuit which is of a modular design so as to be easily connected in series with the offending telephone terminal equipment.

[0019]The foregoing applies specifically to the disclosure of the parent application Ser. No. 09 / 195,522. A third embodiment of an impedance blocking filter circuit of the present invention added by way of this continuation-in-part application is quite similar to the schematic diagram of FIG. 3, except that the filter circuit therein has been modified so that the resistors R1 and R2 are replaced with first and second tank circuits TC1 and TC2, respectively and a reed switch K1 is connected in series with the capacitor C1. As a result, this third embodiment represents an improvement over the embodiment of FIG. 3 since it overcomes the shunt additive capacitance problem and eliminates the deterioration in the return loss at the phone.

[0021]In a fifth embodiment, there is provided an impedance blocking filter circuit which is quite similar to the schematic circuit diagram of FIG. 3, except that the filter circuit therein has been modified so to eliminate the resistors R1 and R2 and a reed switch K1 is connected in series with the capacitor C1. The four inductors L1-L4 and the reed switch K1 are all housed within a multi-sectioned bobbin structure so to significantly reduce interwinding capacitance.

[0023]A seventh embodiment of an impedance blocking filter circuit of the present invention is added by way of this second continuation-in-part application which is quite similiar to the filter circuit of FIG. 9, except that the filter circuit thereof has been modified to include an inductor L13 interconnected between the inductor L1 and the common point A; an inductor L14 interconnected between the inductor L2 and the common point B; and a capacitor C5 connected across the inductors L1,L2. As a consequence, this seventh embodiment represents an improvement over the embodiment of FIG. 9 since it suppresses switching transients from affecting the line side of the house wiring going to the ADSL modem.

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.

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