Outbound interference reduction in a broadband powerline system

• US 8,938,021 B1
• Filed: 05/06/2004
• Issued: 01/20/2015
• Est. Priority Date: 05/06/2004
• Status: Active Grant

• Current Assignee: AT&T Intellectual Property II LP (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property II LP (AT&T, Inc.)
• Inventors: Henry, Paul Shala
• Primary Examiner(s): NEFF, MICHAEL R
• Application Number:
  US10/839,945
• Time in Patent Office: 3,911 Days
• Field of Search: 375/285, 375/259, 375/318, 340/538.12, 340/310.13, 333/124, 700/22, 700/286
• US Class Current: 375/285
• CPC Class Codes: H04B 2203/5416 by adding signals to the wave form of the power source
• CPC Class Codes: H04B 2203/5425 improving S/N by matching impedance, noise reduction, gain control
• CPC Class Codes: H04B 2203/5483 using coupling circuits
• CPC Class Codes: H04B 3/30 Reducing interference caused by unbalanced currents in a normally balanced line
• CPC Class Codes: H04B 3/54 Systems for transmission via power distribution lines
• CPC Class Codes: H04B 3/542 the information being in digital form
• CPC Class Codes: H04B 3/56 Circuits for coupling, blocking, or by-passing of signals
• CPC Class Codes: H04J 1/08 Arrangements for combining channels branching filters H01P1/213, H03H7/46
• CPC Class Codes: H04L 25/028 Arrangements specific to the transmitter end
• CPC Class Codes: H04L 25/10 Compensating for variations in line balance
• CPC Class Codes: H04L 5/0005 Time-frequency

Abstract

Disclosed is a method and apparatus for reducing outbound interference in a broadband powerline communication system. Data is modulated on first and second carrier frequencies and is transmitted via respective first and second lines of the powerline system. A characteristic of at least one of the carrier signals (e.g., phase or amplitude) is adjusted in order to improve the electrical balance of the lines of the transmission system. This improvement in electrical balance reduces the radiated interference of the powerline system. Also disclosed is the use of a line balancing element on or more lines of the powerline system for altering the characteristics of at least one of the power lines in order to compensate for a known imbalance of the transmission system.

Claims

1. A method for reducing interference radiated by a powerline transmission system comprising:

transmitting first data via a modulated first carrier signal on a first line of the transmission system;

transmitting second data via a modulated second carrier signal on a second line of the transmission system; and

adjusting a characteristic of at least one of the first and second carrier signals based on a known imbalance between the first line and the second line to improve the electrical balance of the first and second lines of the transmission system, wherein the characteristic is carrier signal phase.

2. The method of claim 1 wherein the powerline communication system is a frequency division multiplexed system transmitting data on a plurality of frequency channels.

3. The method of claim 2 wherein adjusting is performed independently for each of the frequency channels.

4. The method of claim 1 further comprising adjusting the characteristic of the first and second carrier signals in response to a dynamic determination of an imbalance in the first and second lines.

5. A method for reducing interference radiated by a powerline transmission system comprising:

transmitting first and second data via modulated first and second carrier signals on respective first and second lines of the transmission system using differential excitation; and

generating the first and second carrier signals having characteristics which compensate for imbalances between first and second transmission lines of the system, wherein the imbalances are determined dynamically.

6. The method of claim 5 further comprising:

dynamically adjusting a signal characteristic of at least one of the carrier signals in response to a dynamically detected imbalance between the first and second transmission lines.

7. A transmitter for use in a powerline communication system having a first transmission line and a second transmission line comprising:

at least one modulator for modulating first and second data onto first and second carrier signals; and

a differential driver connected to the at least one modulator for adjusting a characteristic of at least one of the carrier signals to improve the electrical balance of the powerline communication system based on a known imbalance between the first line and the second line, wherein the characteristic is carrier signal phase.

8. The transmitter of claim 7 wherein the powerline communication system is a frequency division multiplexed system transmitting data on a plurality of frequency channels.

9. The transmitter of claim 8 wherein the differential driver performs the adjusting independently for each of the frequency channels.

10. The transmitter of claim 7 wherein the differential driver adjusts the characteristic of the first and second carrier signals in response to a dynamic determination of an imbalance in the first and second lines.

11. A transmitter for use in a powerline communication system having a first transmission line and a second transmission line comprising:

at least one modulator for modulating first and second data onto first and second carrier signals; and

a differential driver connected to the at least one modulator for generating the first and second carrier signals having characteristics which compensate for imbalances between first and second transmission lines of the system, wherein the imbalances are determined dynamically.

12. The transmitter of claim 11 wherein the differential driver dynamically adjusts a signal characteristic of at least one of the carrier signals in response to a dynamically detected imbalance between the first and second transmission lines.