Distributed modem architectures for power line communication systems and other wired communication systems

• US 8,897,342 B2
• Filed: 08/04/2011
• Issued: 11/25/2014
• Est. Priority Date: 08/04/2011
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Zuckerman, Lawrence H., Tsao, Perry I., Yang, Thomas, McGuire, Keiichi, Gong, Chenguang, Bairi, Ravichander
• Primary Examiner(s): Bayard, Emmanuel
• Application Number:
  US13/198,498
• Publication Number:
  US 20130034137A1
• Time in Patent Office: 1,209 Days
• Field of Search: 375219-222, 375256-258, 375/329, 375/331
• US Class Current: 375/219
• CPC Class Codes: H04L 25/0266 Arrangements for providing Galvanic isolation, e.g. by means of magnetic or capacitive coupling
• CPC Class Codes: H04L 25/0278 Arrangements for impedance matching

Abstract

A master modem is configured to generate a carrier signal for transmission over a wired connection. A slave modem is configured to change an impedance of the wired connection to alter generation of the carrier signal by the master modem. The impedance of the wired connection is changed based on data to be provided by the slave modem. The master modem can demodulate its own carrier signal to obtain the data provided by the slave modem. The impedance of the wired connection could be changed by changing an impedance of a transformer winding or inductor of the slave modem, where the transformer winding or inductor is coupled to the wired connection. The impedance of the wired connection could also be changed by changing a reactance of a circuit coupled to the wired connection.

Claims

1. A method of communicating over a DC power line forming a wiring loop for DC current, the method operable with a distributed modem architecture that includes at least one active node and at least one passive node (collectively, nodes), comprising:

AC coupling each active node and each passive node to the power line wiring loop through respective active and passive node couplers that are tuned to an AC carrier signal, and that enable substantially continuous DC current flow through the power line wiring loop,

generating, at the active node, the AC carrier signal with an AC carrier frequency, coupled into the power line wiring loop through the active node coupler;

receiving, at the passive node, the AC carrier signal;

communicating data, from a transmitting passive node to at least one receiving node, at the AC carrier frequency within an AC carrier frequency band by;

changing at a transmitting passive node, the AC impedance of the associated passive node coupler, and thereby changing an AC impedance of the power line wiring loop within the AC carrier frequency band, wherein the AC impedance of the power line wiring loop is changed within the AC carrier frequency band based on data to be transmitted by the transmitting passive node so as to modulate the data onto the AC carrier signal within the AC carrier frequency band;

detecting, at the receiving node, the change in the AC impedance of the power line wiring loop, and thereby detecting the modulated data.

2. The method of claim 1, wherein the passive node coupler comprises one of a transformer winding or an inductor coupled in series with the power line wiring loop.

3. The method of claim 1, wherein changing the AC impedance of the power line wiring loop comprises:

changing a reactance of the passive node coupler.

4. The method of claim 1, further comprising:

converting, at the passive node, the AC carrier signal to DC power for the passive node using a transformer.

5. The method of claim 1, wherein obtaining the data comprises demodulating the data from the AC carrier signal using at least one of:

frequency modulation-based demodulation, phase modulation-based demodulation, and amplitude modulation-based demodulation.

6. The method of claim 1, further comprising:

transmitting the AC carrier signal over different power lines at different times; and

obtaining data from different passive nodes connected to the power lines, wherein the data is obtained from an individual one of the passive nodes when (i) passive nodes connected to inactive power lines enter a high-impedance state, (ii) passive nodes connected to an active power line enter a low impedance state, and (iii) the individual passive nodes toggles between the high-impedance state and the low-impedance state.

7. The method of claim 1, wherein:

generating the AC carrier signal comprises using an oscillator; and

obtaining the data using changes in the AC carrier signal comprises demodulating data in a signal output by the oscillator.

8. The method of claim 1, wherein:

generating the AC carrier signal comprises using an oscillator; and

obtaining the data using changes in the AC carrier signal comprises demodulating a signal generated across an inductive structure that receives the AC carrier signal.

9. A system for communicating over a DC power line forming a wiring loop for DC current, operable as a distributed modem architecture, comprising:

at least one active node configured to generate an AC carrier signal with an AC carrier frequency, coupled into the power line wiring loop through the active node coupler;

at least one passive node configured to communicate with the active node over the power line wiring loop, including;

a passive node coupler including an inductive structure coupled to the power line wiring loop, and configured to receive the AC carrier signal over the power line wiring loop; and

transmit circuitry configured to change an AC impedance of passive node coupler within an AC carrier frequency band, and thereby change the AC impedance of the power line wiring loop within the AC carrier frequency band, wherein the AC impedance of the power line wiring loop is changed within the AC carrier frequency band based on data to be transmitted by the passive node, so as to modulate the data onto the AC carrier signal within the AC carrier frequency band.

10. The system of claim 9, wherein the inductive structure comprises one of:

a transformer winding and an inductor.

11. The system of claim 9, wherein the transmit circuitry comprises a parallel-tuned circuit coupled in parallel with the inductive structure, the parallel-tuned circuit and the inductive structure configured to resonate and change their reactance.

12. The system of claim 9, wherein the transmit circuitry comprises a capacitive or resistive structure coupled in parallel with the inductive structure, the capacitive or resistive structure configured to change the impedance of the inductive structure.

13. The system of claim 9, wherein the active node comprises:

a carrier signal generator configured to generate the AC carrier signal for transmission over the power line; and

receive circuitry configured to obtain the data transmitted by the passive node using changes in the AC carrier signal, the changes in the AC carrier signal caused by changes in the AC impedance of the power line wiring loop made by the passive node so as to modulate the data onto the AC carrier signal.

14. The system of claim 13, wherein:

the carrier signal generator comprises an oscillator; and

the active node coupler comprises a transformer configured to couple the AC carrier signal to the power line wiring loop.

15. The system of claim 13, wherein the receive circuitry comprises:

an inductive structure configured to receive the AC carrier signal; and

a demodulator configured to demodulate a signal generated across the inductive structure.

16. The system of claim 13, wherein:

the receive circuitry is configured to identify a frequency having less interference than a current frequency of the AC carrier signal and to cause the AC carrier signal generator to change the current frequency of the AC carrier signal.

17. The system of claim 13, wherein the receive circuitry comprises a phase shift keying (PSK) demodulator configured to:

receive a preamble from the passive node;

extract symbol timing information using the preamble; and

obtain the data from the passive node using the symbol timing information;

wherein the PSK demodulator is configured to obtain the data even when there is unknown and varying phase shifts of symbols from the passive node defining the data.