US 6,181,777 B2 · 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.

Claims20

Dependent claims

An impedance blocking filter circuit used in telecommunication systems for interconnecting between incoming telephone lines and customer's terminal equipment so as to unconditionally block impedances from above 20 KHz due to the customer's terminal equipment from an ADSL network unit and/or home networking interface unit, said filter circuit comprising:

first, second, and third inductors connected in series between a first input terminal and a first common point;
said first inductor having its one end connected to said first input terminal and its other end connected to one end of said second inductor, said second inductor having its other end connected to one end of said third inductor, said third inductor having its other end connected to said first common point;
fourth, fifth, and sixth inductors connected in series between a second input terminal and a second common point;
said fourth inductor having its one end connected to said second input terminal and its other end connected to one end of said fifth inductor, said fifth inductor having its other end connected to one end of said sixth inductor, said sixth inductor having its other end connected to said second common point;
first switching means having a first end and a second end and being responsive to DC loop current for electrically connecting said first end to said second end;
a capacitor having a first end connected to said first common point and a second end connected to said first end of said switching means, said second end of said switching means being connected to said second common point;
and
correction circuit means interconnected between said common points and said output terminals for significantly reducing return loss caused by inductive impedance when the customer's terminal equipment goes off-hook.

5 more elements

first, second, and third inductors connected in series between a first input terminal and a first common point;
said first inductor having its one end connected to said first input terminal and its other end connected to one end of said second inductor, said second inductor having its other end connected to one end of said third inductor, said third inductor having its other end connected to said first common point;
fourth, fifth, and sixth inductors connected in series between a second input terminal and a second common point;
said fourth inductor having its one end connected to said second input terminal and its other end connected to one end of said fifth inductor, said fifth inductor having its other end connected to one end of said sixth inductor, said sixth inductor having its other end connected to said second common point;
first switching means having a first end and a second end and being responsive to DC loop current for electrically connecting said first end to said second end;
a capacitor having a first end connected to said first common point and a second end connected to said first end of said switching means, said second end of said switching means being connected to said second common point;
and
bobbin means including at least a first narrow section on which is wound said second inductor, first wider sections on which are wound said third inductor, a second narrow section on which is wound said fifth inductor, and second wider sections on which are wound said sixth inductor for reducing interwinding capacitance so as to increase the useful frequency range, said bobbin means having a center portion for receiving said first switching means.

5 more elements

Dependencies are inferred from the claim text.

Impedance blocking filter circuit

Life of this patent

Impedance blocking filter circuit

Life of this patent

Abstract

Claims20