Powerline coupling network

• US 5,485,040 A
• Filed: 01/06/1994
• Issued: 01/16/1996
• Est. Priority Date: 05/10/1991
• Status: Expired due to Term

• Current Assignee: Echelon Corporation (Renesas Electronics Corporation)
• Original Assignee: Echelon Corporation (Renesas Electronics Corporation)
• Inventors: Sutterlin, Philip H.
• Primary Examiner(s): Pellinen, A. D.
• Assistant Examiner(s): Fleming, Fritz M.
• Application Number:
  US08/178,455
• Time in Patent Office: 740 Days
• Field of Search: 307/3, 307/103, 307/104, 340/310 R, 340/310 A, 340/310.07, 340/310.08, 333/32
• US Class Current: 307/3
• CPC Class Codes: H04B 2203/5425 improving S/N by matching impedance, noise reduction, gain control
• CPC Class Codes: H04B 2203/5445 Local network
• CPC Class Codes: H04B 2203/5458 Monitor sensor; Alarm systems
• CPC Class Codes: H04B 2203/5483 using coupling circuits
• CPC Class Codes: H04B 3/56 Circuits for coupling, blocking, or by-passing of signals

Abstract

An apparatus for reducing power line communication signal attenuation is disclosed. This apparatus provides for reduction of power line communication signal attenuation by balancing reactance between chosen circuit elements and the typical impedances found in a house, structure, or similar entity. The present invention uses a series resonant circuitry to couple the communication signal to the power line. The inductance in the series resonant circuitry is chosen to compensate for the de-tuning effect of the typical power line to which it'"'"'s coupled in the communication system.

Claims

1. A circuit for coupling a signal source to a power line having a given impedance due to at least one non-purely resistive load coupled to the power line, such that the power line has a predetermined inductance, and wherein the power line includes two conductors for communicating a signal from the signal source, the circuit comprising:

a resistor having first and second terminals, wherein said first terminal of said resistor is coupled to said signal source, said resistor having sufficient resistance to limit the current of the signal source if the power line is shorted to thus prevent the signal source from saturating;

a coupling transformer having first and second primary terminals and first and second secondary terminals, wherein the first primary terminal is coupled to the second terminal of said resistor and the second primary terminal is coupled to ground potential, and wherein the second secondary terminal is coupled to one of the two conductors of the power line, wherein said coupling transformer transfers the signal between the signal source and the power line, such that the coupling transformer isolates the signal source from the power line when communicating said signal;

a capacitor having first and second terminals, wherein said first terminal of said capacitor is coupled to said the first secondary terminal of said coupling transformer, said capacitor having sufficient impedance to limit the current in the power line at a first frequency when the power line carries current at the first frequency, wherein the capacitor has a predetermined reactance;

an inductive element having first and second terminals, wherein said first terminal of said inductive element is coupled to said second terminal of said capacitor and said second terminal of said inductive element is coupled to the other of the two conductors of said power line, such that said inductive element and said capacitor are coupled in series to form a series resonant circuit, said inductive element having sufficient impedance to compensate for the de-tuning due to said at least one non-purely resistive load coupled to the power line, so that the inductance of the inductive element and the predetermined inductance of the power line at a second frequency offset the predetermined reactance of the capacitor, such that said circuit is tuned, wherein the signal source outputs the second frequency,

wherein the impedance of the inductive element is at a predetermined number of microhenries less than an inductance necessary to offset the predetermined reactance of the capacitor to compensate for impedances attributed to devices coupled to the power line and building wiring and voltage divider effects of the power line.

2. The coupling circuit of claim 1 wherein the impedance of the inductive element is at a value of 17 microhenries less than the inductance necessary to offset the reactance of the capacitor if the power line had no inductance.

3. The coupling circuit of claim 1 wherein the resistance of the resistor is in the range of 5 to 20 ohms.

4. The coupling circuit of claim 3 wherein the capacitor has a value of 0.047 microfarads.

5. The coupling circuit of claim 4 wherein the inductive element is comprised of an inductor which has a value between 18 and 27 microhenries.

6. The coupling circuit of claim 5 wherein the first frequency is rated at 60 hertz.

7. The coupling circuit of claim 6 wherein the second frequency is in the range of 100 to 150 kilohertz.

8. The coupling circuit of claim 4 wherein the coupling transformer and the inductive element together comprise a leaky transformer which has an inductance value of 22 microhenries.

9. A circuit for coupling a signal source to a power line having a given impedance due to at least one non-purely resistive load coupled to the power line, such that the power line has a predetermined inductance, and wherein the power line includes two conductors for communicating a signal from the signal source, the circuit comprising:

a resistor having first and second terminals, wherein said first terminal of said resistor is coupled to said signal source, said resistor having sufficient resistance to limit the current of the signal source if the power line is shorted to thus prevent the signal source from saturating;

a coupling transformer having first and second primary terminals and first and second secondary terminals, wherein the first primary terminal is coupled to the second terminal of said resistor and the second primary terminal is coupled to ground potential, and wherein the second secondary terminal is coupled to one of the two conductors of the power line, wherein said coupling transformer transfers the signal between the signal source and the power line, such that the coupling transformer isolates the signal source from the power line when communicating said signal;

a capacitor having first and second terminals, wherein said first terminal of said capacitor is coupled to said the first secondary terminal of said coupling transformer, said capacitor having sufficient impedance to limit the current in the power line at a first frequency when the power line carries current at the first frequency, wherein the impedance of the capacitor is a predetermined reactance;

an inductive element having first and second terminals, wherein said first terminal of said inductive element is coupled to said second terminal of said capacitor and said second terminal of said inductive element is coupled to the other of the two conductors of said power line, such that said inductive element and said capacitor are coupled in series to form a series resonant circuit, said inductive element having sufficient impedance to compensate for the de-tuning due to said at least one non-purely resistive load coupled to the power line, so that the inductance of the inductive element does not cancel out the impedance of the capacitor if the power line had no inductance at a second frequency and yet the inductance of the inductive element and the predetermined inductance of the power line at the second frequency still offsets the predetermined reactance of the capacitor, such that said circuit is tuned, wherein the signal source outputs the second frequency,

wherein the impedance of the inductive element is at a predetermined number of microhenries less than an inductance necessary to offset the predetermined reactance of the capacitor to compensate for impedances attributed to devices coupled to the power line and building wiring and voltage divider effects of the power line.

10. The coupling circuit of claim 9 wherein the impedance of the inductive element is 17 microhenries less than the inductance necessary to offset the reactance of the capacitor if the power line had no inductance.

11. The coupling circuit of claim 9 wherein the first frequency is rated at 60 hertz.

12. The coupling circuit of claim 11 wherein the second frequency is in the range of 100 to 150 kilohertz.

13. The coupling circuit of claim 12 wherein the capacitor has a value of 0.047 microfarads.

14. The coupling circuit of claim 13 wherein the inductive element is comprised of an inductor which has a value of 22 microhenries.

15. The coupling circuit of claim 14 wherein the resistance of the resistor is in the range of 5 to 20 ohms.

16. A circuit for coupling a signal source to a power line having a given impedance due to at least one non-purely resistive load coupled to the power line, such that the power line has a predetermined inductance, and wherein the power line includes two conductors for communicating a signal from the signal source, the circuit comprising:

a resistor having first and second terminals, wherein said first terminal of said resistor is coupled to said signal source, said resistor having sufficient resistance to limit the current of the signal source if the power line is shorted to thus prevent the signal source from saturating;

a transformer having first coil having first and second primary terminals and a second coil having first and second secondary terminals, wherein said first primary terminal is coupled to said second terminal of said resistor and the second primary terminal is coupled to ground, and wherein the second secondary terminal is coupled to one of the two conductors of the power line, said transformer isolating the signal source from the power line during coupling;

a capacitor having first and second terminals, wherein said first terminal of said capacitor is coupled to the first secondary terminal of said second coil of said transformer, said capacitor having sufficient impedance to limit the current in the power line at a first frequency when the power line carries current at the first frequency, wherein the impedance of the capacitor is a predetermined reactance; and

an inductive element having first and second terminals, wherein said first terminal of said inductive element is coupled to said second terminal of said capacitor and said second terminal of said inductive element is coupled to the other of the two conductors of said power line, such that said inductive element, said capacitor and said resistor operate as a series resonant circuit coupled in series, said inductive element having sufficient impedance to compensate for the de-tuning due to said at least one non-purely resistive load coupled to the power line, so that the inductance of the inductive element and the predetermined inductance of the power line at a second frequency offset the predetermined reactance of the capacitor, such that said circuit is tuned and prevents said transformer from becoming saturated, wherein the signal source outputs the second frequency,

wherein the impedance of the inductive element is at a predetermined number of microhenries less than an inductance necessary to offset the predetermined reactance of the capacitor to compensate for impedances attributed to devices coupled to the power line and building wiring and voltage divider effects of the power line.

17. The coupling circuit of claim 16 wherein the impedance of the inductive element is 17 microhenries less than the inductance necessary to offset the reactance of the capacitor if the power line had no inductance.

18. A circuit for coupling a signal source to a power line having a given impedance due to at least one non-purely resistive load coupled to the power line, such that the power line has a predetermined inductance, and wherein the power line includes two conductors for communicating a signal from the signal source, the circuit comprising:

a resistor having first and second terminals, wherein said first terminal of aid resistor is coupled to said signal source, said resistor having sufficient resistance to limit the current of the signal source if the power line is shorted to thus prevent the signal source from saturating;

a coupling transformer having a first coil having first and second primary terminals and a second coil having first and second secondary terminals, wherein said first primary terminal is coupled to said second terminal of said resistor and the second primary terminal is coupled to ground, and wherein the second secondary terminal is coupled to one of the two conductors of the power line, said transformer isolating the signal source from the power line during coupling; and

a capacitor having first and second terminals, wherein said first terminal of said capacitor is coupled to said the first secondary terminal of said coupling transformer and the second terminal of the capacitor is coupled to the other of said two conductors of the power line, said capacitor having sufficient impedance to limit the current in the power line at a first frequency when the power line carries current at the first frequency, wherein the impedance of the capacitor is a predetermined reactance,

wherein said coupling transformer has a leakage inductance, said leakage inductance being sufficient to compensate for the de-tuning due to said at least one non-purely resistive load coupled to the power line, so that the leakage inductance of the coupling transformer and the predetermined inductance of the power line at a second frequency offset the predetermined reactance of the capacitor, such that said circuit is tuned, wherein the signal source outputs the second frequency, and further wherein the leakage inductance of the coupling transformer is at a predetermined number of microhenries less than an inductance necessary to offset only the predetermined reactance of the capacitor to compensate for impedances attributed to devices coupled to the power line and building wiring and voltage divider effects of the power line.

19. A circuit for coupling a communication signal to a power line, wherein said power line operates at a power distribution frequency, said circuit comprising:

a transformer;

a capacitor coupled in a series between the transformer and the power line, wherein the capacitor has sufficient impedance to limit current drawn from the power line at the power distribution frequency, and further wherein the capacitor has a capacitive reactance; and

an inductive element coupled in series with the capacitor, wherein the inductive element has an inductance less than the inductance that fully cancels the capacitive reactance of the capacitor at frequencies used for communication; and

wherein the inductance of the inductive element compensates for impedances attributed to devices coupled to the power line and building wiring and voltage divider effects of the power line.

20. The circuit defined in claim 19 wherein the communication signal is generated by a communication signal source, and wherein the circuit further comprises a resistive element coupled between the communication signal source and the transformer, wherein the resistive element limits current from the communication signal source when impedance of the power line becomes a short circuit at said frequencies used for communication.

21. The circuit defined in claim 19 wherein the power distribution frequency comprises 50 Hz.

22. The circuit defined in claim 19 wherein the power distribution frequency comprises 60 Hz.

23. The circuit defined in claim 19 wherein frequencies used for communication signal source ranges from 100 KHz to 150 KHz.

24. A circuit for coupling a communication signal to a power line, wherein the power line operates at a power distribution frequency, said circuit comprising:

a transformer;

a capacitor coupled between the transformer and the power line having sufficient impedance to limit current drawn from the power line at the power distribution frequency, wherein the capacitor has a capacitive reactance;

an inductive element directly connected in series to the capacitor, such that the transformer, the power line, the capacitor and the inductive element are coupled in series, wherein the inductive element has an inductance less than the inductance that fully cancels the capacitive reactance of the capacitor at frequencies used for communication, and wherein the inductance of the inductive element compensates for impedances attributed to devices coupled to the power line and building wiring and voltage divider effects of the power line.

25. The circuit defined in claim 24 wherein the communication signal is generated by a communication signal source, and wherein the circuit further comprises a resistive element between the communication signal and the transformer, wherein the resistive element limits current from the communication signal source when impedance of the power line becomes a short circuit at said frequencies used for communication.

26. The circuit defined in claim 24 wherein the power distribution frequency comprises 50 Hz.

27. The circuit defined in claim 24 wherein the power distribution frequency comprises 60 Hz.

28. The circuit defined in claim 24 wherein frequencies used for communication ranges from 100 KHz to 150 KHz.

29. A circuit for coupling a communication signal to a power line, wherein the power line operates at a power distribution frequency, said circuit comprising:

a transformer having a leakage inductance;

a capacitor coupled in series between the transformer and the power line, wherein the capacitor has sufficient impedance to limit current drawn from the power line at the power distribution frequency, and wherein the capacitor has capacitive reactance, and

further wherein the leakage inductance is less than the inductance that fully cancels the capacitive reactance of the capacitor at frequencies used for communication and compensates for impedances attributed to devices coupled to the power line and building wiring and voltage divider effects of the power line.

30. The circuit defined in claim 29 wherein the power line includes non-purely resistive impedances and the leakage inductance of the transformer reduces voltage divider effects attributed to non-purely resistive impedances of the power line.

31. The circuit defined in claim 29 wherein the communication signal is generated by a communication signal source, and wherein the circuit further comprises a resistive element between the communication source signal and the transformer, wherein the resistive element limits current from the communication signal source when impedance of the power line becomes a short circuit at said frequencies used for communication.