All-pass network for data transmission over a CATV system

• US 7,739,719 B2
• Filed: 08/03/2004
• Issued: 06/15/2010
• Est. Priority Date: 08/03/2004
• Status: Active Grant

• Current Assignee: PPC Broadband Incorporated (Belden Inc.)
• Original Assignee: John Mezzalingua Associates Incorporated
• Inventors: Olcen, Ahmet Burak, Shafer, Steven K., Palinkas, Raymond
• Primary Examiner(s): Lonsberry; Hunter B.
• Application Number:
  US10/910,234
• Publication Number:
  US 20060031911A1
• Time in Patent Office: 2,142 Days
• Field of Search: 725148-150
• US Class Current: 725/149
• CPC Class Codes: H04N 21/6118 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 7/102 Circuits therefor, e.g. noise reducers, equalisers, amplifiers H04N7/108 takes precedence
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

A cable system, and a method for configuring a path of a cable system, wherein the group delay caused by one or more amplifiers having diplex filter networks is substantially equalized over all frequencies within a predetermined band by the use of one or more all-pass delay equalizers. A method of configuring a path includes steps of determining a delay versus frequency characteristic of the path within the predetermined frequency band, and providing from one to a plurality of all-pass delay equalizers in the path, wherein a collective delay versus frequency characteristic of the all-pass delay equalizer(s) within a predetermined frequency band is a mirror image of that caused by the amplifier(s), such that all frequencies within the predetermined frequency band are delayed by substantially the same amount and hence all frequency components of a signal arrive at a receiver at substantially the same time.

Claims

1. A method for configuring a path of a cable TV system, wherein the path includes from one to a plurality of amplifiers for amplifying signals transmitted along the path to a receiver, the amplifier(s) having diplex filter network(s) for separating forward and return signals, the method comprising the steps of:

determining a collective delay versus frequency characteristic of the path within the predetermined frequency band caused by the amplifier(s) with diplex filter network(s); and

providing from one to a plurality of all-pass delay equalizers in the path, wherein a collective delay versus frequency characteristic of the all-pass delay equalizer(s) within a predetermined frequency band is substantially a mirror image of that caused by the amplifier(s) with diplex filter network(s), such that all frequencies within the predetermined frequency band are delayed by substantially the same amount and hence all frequency components of a signal occupying the predetermined frequency band arrive at the receiver in the path at substantially the same time.

2. The method of claim 1, wherein the providing step comprises providing from one to a plurality of passive non-powered all-pass delay equalizers in the path.

3. The method of claim 1, wherein the providing step comprises providing from one to a plurality of active powered all-pass delay equalizers in the path.

4. The method of claim 1, wherein the path comprises a trunk that extends from a head end facility to a tap, and wherein the providing step comprises providing at least one all-pass delay equalizer in the trunk.

5. The method of claim 4, wherein a plurality of all-pass delay equalizers are provided in the trunk.

6. The method of claim 1, wherein the path comprises a trunk that extends from a head end facility to a tap, and a feeder line that extends from the tap to an end-user facility, and wherein the providing step comprises providing at least one all-pass delay equalizer in the feeder line.

7. The method of claim 6, wherein the providing step further comprises providing at least one all-pass delay equalizer in the trunk.

8. A cable system for transmitting signals having frequency components of different frequencies spanning a predetermined frequency band, the cable system comprising:

a head end facility;

a trunk operable to transmit signals along the trunk to and from the head end facility;

a tap in the trunk;

a feeder line connected at one end to the tap, an opposite end of the feeder line being for connection to an end user'"'"'s equipment;

the cable system defining a forward path for signals transmitted from the head end facility to the end user and a return path for signals transmitted from the end user to the head end facility;

at least one amplifier in the return path for amplifying signals transmitted from the end user to the head end facility, the amplifier(s) having diplex filter network(s) for separating the signals transmitted over the forward and return paths, the diplex filter network(s) causing a delay versus frequency characteristic within the predetermined frequency band for signals transmitted over the return path; and

at least one all-pass delay equalizer in the return path, wherein a delay versus frequency characteristic of the all-pass delay equalizer(s) within the predetermined frequency band is substantially a mirror image of that caused by the amplifier(s) with diplex filter network(s), such that all frequencies within the predetermined frequency band are delayed by substantially the same amount and hence all frequency components of the return signals occupying the predetermined frequency band arrive at the head end facility at substantially the same time.

9. The cable system of claim 8, wherein the at least one all-pass delay equalizer comprises a passive non-powered all-pass delay equalizer.

10. The cable system of claim 8, wherein the at least one all-pass delay equalizer comprises an active powered all-pass delay equalizer.

11. The cable system of claim 8, wherein the at least one all-pass delay equalizer is provided in the trunk.

12. The cable system of claim 11, wherein a plurality of all-pass delay equalizers are provided in the trunk.

13. The cable system of claim 8, wherein the at least one all-pass delay equalizer is provided in the feeder line.

14. The cable system of claim 13, further comprising at least one all-pass delay equalizer in the trunk.

15. The cable system of claim 8, wherein there are from one to a plurality of amplifiers in the trunk for amplifying signals transmitted over the return path, and wherein there are from one to a plurality of all-pass delay equalizers in the trunk, there being one said all-pass delay equalizer for each said amplifier.

16. The cable system of claim 15, wherein each all-pass delay equalizer comprises a plug-in module and each amplifier has a receptacle into which the plug-in module is installed.