Method and structure for coupling power-line carrier current signals using common-mode coupling

Claim 1

A power line carrier communication system for communicating between a first subscriber site and a second subscriber site of a power distribution system which conveys power at an alternating current power line frequency, where the first subscriber site is coupled to a common primary distribution line through a first distribution transformer and the second subscriber is coupled to the common primary distribution line through a second distribution transformer, comprising: a transmitter at the first subscriber site which outputs a signal at a transmitter output, said signal being referenced to an earth ground and being a modulated carrier signal characterized by a carrier frequency, said carrier frequency being different from the power line frequency; first secondary distribution means coupled to a secondary side of the first distribution transformer and to a first power feeder at the first subscriber site for distributing power to said first power feeder; second secondary distribution means coupled to a secondary side of the second distribution transformer and to a second power feeder at the second subscriber site for distributing power to said second power feeder; a first plurality of coupling capacitors, wherein each of said coupling capacitors is coupled at a first terminal to said transmitter output and is coupled at a second terminal to a line of said first secondary distribution means; and a second plurality of coupling capacitors, wherein each of said coupling capacitors is coupled at a first lead to a line of said second secondary distribution means; and a receiver at the second subscriber site, commonly coupled at an input to a second lead of each one of said second plurality of coupling capacitors, said input receiving said signal from said transmitter as a voltage relative to said earth ground, said signal received after propagating through said first plurality of coupling capacitors, said first distribution transformer, the common primary distribution line, said second distribution transformer, and said second plurality of coupling capacitors.

Claim 9

A method for communicating between a first subscriber site and a second subscriber site of a power distribution system, where a communication path crosses at least a first distribution transformer and a second distribution transformer which are both coupled to a common primary distribution line, comprising the steps of: common-mode coupling a transmitter to at least two lines of a first secondary distribution line, said first secondary distribution line also coupling electrical power from the first distribution transformer to the first subscriber site; common-mode coupling a receiver to at least two lines of a second secondary distribution line, said second secondary distribution line also coupling electrical power from the second distribution transformer to the second subscriber site; generating a packet comprising data to be communicated and an address corresponding to said second subscriber site; outputting a signal representative of said packet from said transmitter, said signal conveyed as a varying voltage relative to earth ground on both of said at least two lines of said first secondary distribution line, said signal being of equal phase and amplitude on each of said at least two lines of said first secondary distribution line; receiving said signal at least at said receiver, said signal conveyed as a varying voltage relative to earth ground on both of said at least two lines of said second secondary distribution line, said signal being of equal phase and amplitude on each of said at least two lines of said second secondary distribution line; converting said signal into a received packet, said address being readable in said received packet; comparing said address to a receiver address; and accepting said received packet when said address and said receiver address match, and discarding said received packet when said address and said receiver address do not match.

Claim 10

A method for communicating between a first subscriber site and a second subscriber site of a power distribution system, where a communication path crosses at least a first distribution transformer and a second distribution transformer which are both coupled to a common primary distribution line, comprising the steps of: common-mode coupling a transmitter to at least two lines of a first secondary distribution line, said first secondary distribution line also coupling electrical power from the first distribution transformer to the first subscriber site; common-mode coupling a receiver to at least two lines of a second secondary distribution line, said second secondary distribution line also coupling electrical power from the second distribution transformer to the second subscriber site; generating a packet comprising data to be communicated and an address corresponding to said second subscriber site; outputting a signal representative of said packet from said transmitter, said signal conveyed as a varying voltage relative to earth ground on both of said at least two lines of said first secondary distribution line, said signal being of equal phase and amplitude on each of said at least two lines of said first secondary distribution line; receiving said signal at least at said receiver, said signal conveyed as a varying voltage relative to earth ground on both of said at least two lines of said second secondary distribution line, said signal being of equal phase and amplitude on each of said at least two lines of said second secondary distribution line; converting said signal into a received packet, said address being readable in said received packet; comparing said address to a receiver address; and accepting said received packet when said address and said receiver address match, and discarding said received packet when said address and said receiver address do not match.