Passive system used to merge telephone and broadband signals onto one coaxial cable

• US 6,144,399 A
• Filed: 03/25/1999
• Issued: 11/07/2000
• Est. Priority Date: 03/25/1999
• Status: Expired due to Fees

• Current Assignee: Comcast MO Group Incorporated (Comcast Corporation)
• Original Assignee: MediaOne Group Inc. (Comcast Corporation)
• Inventors: Manchester, Earl E., Musselman, Miles E.
• Primary Examiner(s): Faile, Andrew I.
• Assistant Examiner(s): Tran, Hai V.
• Application Number:
  US09/276,058
• Time in Patent Office: 593 Days
• Field of Search: 348/6, 348/12-13, 348/552, 455/3.1, 455/5, 455/6.3, 333/126, 333/129, 333/132, 333/167, 379/344, 379/345
• US Class Current: 725/127
• CPC Class Codes: H04L 12/2801 Broadband local area networks

Abstract

An apparatus and a method for simultaneously transporting telephone signals and broadband signals on a single coaxial cable. The ring line and tip line of the telephone signals are dc coupled onto the inner and outer conductors of the coaxial cable, while the information wire and reference ground of the broadband signal are ac coupled onto the inner and outer conductors of the coaxial cable respectively. Low pass filters at each end of the coaxial cable pass the telephone signal in and out of telephone jacks while blocking the broadband signals. High pass filters at each end of the coaxial cable allow the broadband signals to pass in and out of coaxial connectors while blocking the telephone signals. The coaxial cable is isolated from earth ground to prevent shorting of the telephone electrical power to earth ground. A ground block may be added to connect the reference ground of the incoming broadband signal to earth ground. The ground block may include surge suppression to protect the information wire of the incoming broadband signal.

Claims

1. An apparatus that transports a telephone signal and a broadband signal between a first location and a second location along a coaxial cable comprising:

a first low pass filter at the first location dc coupling a first ring line of the telephone signal to an inner conductor of the coaxial cable, and dc coupling a first tip line of the telephone signal to an outer conductor of the coaxial cable;

a first high pass filter at the first location ac coupling a first information wire of the broadband signal to the inner conductor of the coaxial cable, and ac coupling a first reference ground of the broadband signal to the outer conductor of the coaxial cable;

a second low pass filter at the second location dc coupling a second ring line of the telephone signal to the inner conductor of the coaxial cable, and dc coupling a second tip line of the telephone signal to the outer conductor of the coaxial cable;

a second high pass filter at the second location ac coupling a second information wire of the broadband signal to the inner conductor of the coaxial cable, and ac coupling a second reference ground of the broadband signal to the outer conductor of the coaxial cable.

2. The apparatus of claim 1 further comprising a ground block at the first location connecting the first information wire and the first reference ground to the first high pass filter, and connecting the first reference ground to an earth ground.

3. The apparatus of claim 1 wherein the first low pass filter, the second low pass filter, the first high pass filter, and the second high pass filter have a first, a second, a third, and a fourth roll off frequency respectively in a range from approximately 50 kilohertz to approximately 5 megahertz, and wherein the first and second roll off frequencies are below the third and fourth roll off frequencies.

4. The apparatus of claim 1 wherein the first low pass filter comprises a first pair of inductors connected in series between the first ring line of the telephone signal and the inner conductor of the coaxial cable at the first location, a first capacitor connected from a first junction between the first pair of inductors to an earth ground, a second pair of inductors connected in series between the first tip line of the telephone signal and the outer conductor of the coaxial cable at the first location, and a second capacitor connected from a second junction between the second pair of inductors to the earth ground.

5. The apparatus of claim 1 wherein the second low pass filter comprises a third pair of inductors connected in series between the second ring line of the telephone signal and the inner conductor of the coaxial cable at the second location, a fourth pair of inductors connected in series between the second tip line of the telephone signal and the outer conductor of the coaxial cable at the second location, and a third capacitor connected from a third junction between the third pair of inductors to a fourth junction between the fourth pair of inductors.

6. The apparatus of claim 1 wherein the first high pass filter comprises a fifth capacitor connected between the first information wire of the broadband signal and the inner conductor of the coaxial cable at the first location, and a sixth capacitor connected between the first reference ground of the broadband signal and the outer conductor of the coaxial cable at the first location.

7. The apparatus of claim 1 wherein the second high pass filter comprises a seventh capacitor connected between the second information wire of the broadband signal and the inner conductor of the coaxial cable at the second location, and an eighth capacitor connected between the second reference ground of the broadband signal and the outer conductor or the coaxial cable at the second location.

8. A method of transporting a telephone signal and a broadband signal between a first location and a second location along a coaxial cable comprising:

low pass filtering the telephone signal at the first location with a first low pass filter;

dc coupling the telephone signal filtered by the first low pass filter onto the coaxial cable at the first location;

high pass filtering the broadband signal at the first location with a first high pass filter;

ac coupling the broadband signal filtered by the first high pass filter onto the coaxial cable at the first location;

transporting the telephone signal and the broadband signal coupled to the coaxial cable from the first location to the second location;

dc coupling the telephone signal and the broadband signal transported by the coaxial cable to the second location to a second low pass filter;

low pass filtering the dc coupled telephone signal and broadband signal at the second location with the second low pass filter to isolate the telephone signal from the broadband signal;

ac coupling the telephone signal and the broadband signal transported by the coaxial cable to the second location to a second high pass filter; and

high pass filtering the ac coupled telephone signal and broadband signal with the second high pass filter to isolate the broadband signal from the telephone signal.

9. The method of claim 8 wherein the broadband signal is defined by voltages between an information wire and a reference ground, the method further comprising connecting the reference ground to an earth ground at the first location before high pass filtering with the first high pass filter.

10. The method of claim 8 wherein the first low pass filter, the second low pass filter, the first high pass filter and the second high pass filter have a first, a second, a third and a fourth roll off frequency respectively in a range from approximately 50 kilohertz to approximately 5 megahertz, and wherein the first and second roll off frequencies are below the third and fourth roll off frequencies.