Common mode signal reduction in powerline communication devices

Patent metadata

Field	Value
Publication number	US-9001926-B2
Application number	US-201213564558-A
Country	US
Kind code	B2
Filing date	Aug 1, 2012
Priority date	Aug 1, 2012
Publication date	Apr 7, 2015
Grant date	Apr 7, 2015

Abstract

An active common mode current limiting mechanism limits common mode currents in a powerline communication device. A powerline coupler determines a common mode signal component of an output signal of the powerline communication device. The powerline coupler provides voltage estimates of the common mode signal component to a signal processing unit. The signal processing unit generates samples of the voltage estimates of the common mode signal component. The signal processing unit adjusts transmit voltage levels of the powerline communication device based on the samples of the voltage estimates of the common mode signal component to limit the common mode signal component of the output signal.

First claim

What is claimed is:

1. A method for limiting a common mode signal component of a powerline communication device, comprising:
determining, using a feedback loop of the powerline communication device, a common mode signal component of an output signal of the powerline communication device;
providing, via the feedback loop, voltage estimates of the common mode signal component to a signal processing unit of the powerline communication device;
generating samples of the voltage estimates using an analog-to-digital converter of the signal processing unit, in response to the signal processing unit receiving the voltage estimates; and
adjusting a transmit voltage of the powerline communication device based, at least in part, on the samples of the voltage estimates, wherein said adjusting comprises,
determining a common mode voltage level of a carrier frequency associated with the samples; and
adjusting a differential mode voltage gain associated with the carrier frequency to maintain the common mode signal component below a threshold limit.

2. The method of claim 1 , wherein said determining the common mode signal component of the output signal comprises:
providing the output signal to a common mode choke on the feedback loop; and
generating the common mode signal component of the output signal using the common mode choke.

3. The method of claim 1 , wherein said adjusting the transmit voltage of the powerline communication device comprises:
determining a common mode voltage level of the carrier frequency;
determining an orthogonal frequency-division multiplexing (OFDM) carrier weight for the carrier frequency based, at least in part, on the common mode voltage level; and
adjusting a differential mode voltage gain associated with the carrier frequency, wherein said adjusting the differential mode voltage gain comprises multiplying a modulated symbol with the OFDM carrier weight.

4. The method of claim 3 , wherein the carrier frequency is an OFDM carrier associated with the samples.

5. The method of claim 1 , wherein said providing, via the feedback loop, the voltage estimates comprises providing, via a feedback loop of a powerline coupler, the voltage estimates from the powerline coupler to the signal processing unit.

6. A method for limiting a common mode signal component of a powerline communication device, comprising:
determining estimates of a common mode current of a differential output signal at first and second terminals of the powerline communication device, wherein the common mode current is associated with a carrier frequency;
determining a first frequency dependent carrier weight and a second frequency dependent carrier weight for the carrier frequency based, at least in part, on the estimates; and
adjusting a transmit voltage associated with the differential output signal, wherein said adjusting the transmit voltage comprises applying the first frequency dependent carrier weight and the second frequency dependent carrier weight to the carrier frequency.

7. The method of claim 6 , wherein said adjusting the transmit voltage comprises:
adjusting a first root mean square (RMS) voltage of a first signal at the first terminal using the first frequency dependent carrier weight; and
adjusting a second RMS voltage of a second signal at the second terminal using the second frequency dependent carrier weight.

8. The method of claim 7 , further comprising:
providing a first current on the first terminal based on the first RMS voltage;
providing a second current on the second terminal based on the second RMS voltage, wherein the first current is different from the second current; and
differentially driving the first current on the first terminal and the second current on the second terminal to a powerline communication coupler of the powerline communication device using a differential digital-to-analog converter (DAC).

9. The method of claim 7 , wherein:
the first frequency dependent carrier weight is a first orthogonal frequency-division multiplexing (OFDM) carrier weight, and the second frequency dependent carrier weight is a second OFDM carrier weight;
said adjusting the first RMS voltage comprises multiplying a first terminal modulated symbol with the first OFDM carrier weight; and
said adjusting the second RMS voltage comprises multiplying a second terminal modulated symbol with the second OFDM carrier weight.

10. The method of claim 6 , wherein the first frequency dependent carrier weight and the second frequency dependent carrier weight are determined by a carrier scaling control unit using real-time measurements of the common mode current.

11. The method of claim 6 , wherein said determining the estimates of the common mode current comprises,
receiving, at a signal processing unit of the powerline communication device, the estimates of the common mode current from a powerline coupler of the powerline communication device, and
generating samples of the estimates using an analog-to-digital converter of the signal processing unit.

12. The method of claim 6 , further comprising amplifying the common mode current at the first and second terminals to adjust the estimates of the common mode current.

13. The method of claim 6 , further comprising utilizing a calibration table to account for limitations of a common mode current measuring device to adjust the estimates of the common mode current.

14. The method of claim 6 , wherein the first and second terminals of the powerline communication device comprise a line terminal wire and a neutral terminal wire, respectively, of the powerline communication device.

15. The method of claim 6 , wherein the first and second terminals of the powerline communication device comprise a line terminal wire and a protective earth terminal wire, respectively, of the powerline communication device.

16. A network device comprising:
a powerline communication (PLC) coupler operable to:
determine, using a feedback loop of the network device, a common mode signal component of an output signal of the network device, wherein said determining the common mode signal comprises,
providing the output signal to a common mode choke on the feedback loop; and
generating the common mode signal component using the common mode choke;

provide, via the feedback loop, voltage estimates of the common mode signal component to a PLC processing unit of the network device; and

the PLC processing unit operable to,
generate samples of the voltage estimates of the common mode signal component using an analog-to-digital converter of the PLC processing unit, in response to receiving the voltage estimates; and
adjust a transmit voltage of the network device based, at least in part, on the samples of the voltage estimates.

17. The network device of claim 16 , wherein the PLC processing unit operable to adjust the transmit voltage of the network device comprises the PLC processing unit operable to:
determine a common mode voltage level of a carrier frequency associated with the samples of the voltage estimates; and
adjust a differential mode voltage gain associated with the carrier frequency to maintain the common mode signal component below a threshold limit.

18. The network device of claim 16 , wherein the PLC processing unit operable to adjust the transmit voltage comprises the PLC processing unit operable to:
determine a common mode voltage level of a carrier frequency associated with the samples of the voltage estimates;
determine an orthogonal frequency-division multiplexing (OFDM) carrier weight for the carri

Assignees

• Shad Faisal M
• Qualcomm Inc

Inventors

• Shad Faisal M

Classifications

• H04B3/542 Primary

  the information being in digital form · CPC title

• H04B2203/5425

  improving S/N by matching impedance, noise reduction, gain control · CPC title

• H04B2203/5416

  by adding signals to the wave form of the power source · CPC title

• H04B2203/5495

  having measurements and testing channel · CPC title