Bridged tap terminator

Details Bridged tap terminator Bridged tap terminator

1998-11-30

2001-05-29

Chan, Wing F. (Department: 2643)

Telephonic communications

Line equalization or impedance matching

C379S394000, C379S093050, C370S494000

Reexamination Certificate

active

06240178

ABSTRACT:

TECHNICAL FIELD
The present invention relates to terminating bridged taps on a subscriber loop used to carry telephone service signals and digital subscriber line signals.
BACKGROUND ART
A subscriber loop connects a telephone company central office to a demarcation point on customer premises. The subscriber loop is typically a pair of wires such as a twisted pair. Traditionally, a subscriber loop is used to carry plain old telephone service (POTS) signals between central office equipment and customer equipment.
Bridged taps are sometimes introduced into the subscriber loop. Bridged taps typically are wire splices on a cable pair. Bridged taps simplify outside plant design and administration by making a wire pair physically available for termination at different customer locations. Although only one customer would use the cable pair at any time, the bridged tap provides flexibility as to which particular customer is assigned to any particular cable pair. This flexibility simplifies network design that results from frequent customer moves, requests for second lines, and new constructions. Often, a bridged tap is left unterminated once installed in the subscriber loop.
Recently, digital subscriber line (DSL) based services have been provided to customers over subscriber loops. DSL signals operate at a higher bandwidth than POTS signals, permitting voice, data, and video services. Also, DSL signals may be modulated to a frequency range outside the range covered by POTS signals.
Bridged taps in subscriber loops may severely attenuate DSL signals. This is because the unterminated bridged tap appears as a low impedance element over frequency ranges depending on the geometry of the bridged tap. If DSL signals are operating within these frequency ranges, the signals may be severely attenuated.
What is needed is proper termination of bridged taps to allow adequate transmission of both POTS and DSL signals. The termination should provide high tap impedance for POTS signals, low insertion loss for DSL signals, and impedance matching for DSL signals. Bridged tap termination should be adaptable to different tap geometries and subscriber loop variations as well as be economical to produce.
DISCLOSURE OF INVENTION
It is a primary object of the present invention to provide termination of bridged taps in communication lines.
Another object of the present invention is to improve reception on a subscriber loop.
Still another object of the present invention is to provide a bridged tap terminator with high tap impedance for POTS signals.
Yet another object of the present invention is to provide a bridged tap terminator with low insertion loss for DSL signals.
A further object of the present invention is to provide a bridged tap terminator with impedance matching for DSL signals.
A still further object of the present invention is to provide a bridged tap terminator that is economical to produce.
In carrying out the above objects and other objects and features of the present invention, a method is provided for improving reception on a subscriber loop which carries POTS signals and DSL signals. The subscriber loop contains a bridged tap which may attenuate DSL transmissions. The method includes determining coefficients for a terminating filter. The terminating filter provides high tap impedance for POTS signals, low insertion loss for DSL signals, and impedance matching for DSL signals. The terminating filter is constructed based on the determined coefficients. The bridged tap is terminated with the constructed terminating filter.
In an embodiment of the present invention, determining coefficients includes selecting high pass filter coefficients to provide high impedance for POTS signals and low insertion loss for DSL signals. Determining coefficients also includes selecting coefficients to match the bridged tap characteristic impedance. In an alternative embodiment, band pass filter coefficients are selected to provide high impedance for POTS signals and low insertion loss for DSL signals.
A bridged tap terminator for improving reception on a subscriber loop is also provided. The bridged tap terminator includes a filter connected to the bridged tap. The filter provides high impedance for POTS signals and low insertion loss for DSL signals. The bridged tap terminator also includes a matching circuit connected to the filter. The matching circuit provides impedance matching for DSL signals. In alternative embodiments, the filter may be a high pass filter or a band pass filter.
A subscriber loop system is also provided. The subscriber loop system includes a central office with POTS communication equipment and DSL communication equipment. The subscriber loop system also includes at least one customer premises with POTS communication equipment and DSL communication equipment. A subscriber loop connects POTS communication equipment in the customer premises with corresponding POTS communication equipment in the central office. The subscriber loop also connects DSL equipment in the customer premises with corresponding DSL equipment in the central office. The subscriber loop includes a bridged tap. A bridged tap terminator is connected to the bridged tap. The bridged tap terminator has a filter connected to the bridge tap for providing high impedance for POTS signals and low insertion loss for DSL signals. The bridged tap terminator also includes a matching circuit connected to the filter for providing impedance matching for DSL signals.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with accompanying drawings.


REFERENCES:
patent: 5610922 (1997-03-01), Balatoni
patent: 5729824 (1998-03-01), O'Neill et al.
patent: 5757803 (1998-05-01), Russell et al.
patent: 5883941 (1999-03-01), Akers
patent: 5970088 (1999-10-01), Chen
patent: 6002722 (1999-12-01), Wu
patent: 6021167 (2000-02-01), Wu
patent: 6031300 (2000-02-01), Moran

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