Patent ID: 7242729

Claim:
A method of decoding a phase shift keying signal carried on a carrier frequency over a power line operating at a power grid frequency, the method comprising the steps of: detecting a zero crossing of the alternating current on a first phase of the power line operated at the power grid frequency; converting at least a portion of a received analog signal carried on the carrier frequency to a set of digital samples, the portion corresponding to the analog signal during a sampling window established in relation to the detected zero crossing on the first phase of the power line; using the detected zero crossing as a trigger to create a set of digital values of an ideal cosine wave with a frequency substantially equal to the carrier frequency; using the detected zero crossing to create a set of digital values of an ideal sine wave with frequency substantially equal to the carrier frequency; multiplying a subset of digital samples with a subset of corresponding created digital values for the ideal cosine wave and storing the sum of the products as the In-Phase Component of the set of digital samples; multiplying a subset of digital samples with a subset of corresponding created digital values for the ideal sine wave and storing the sum of the products as the Quadrature component of the set of digital samples; obtaining a phase offset for the received analog signal from an ideal cosine wave by obtaining the Arctangent of the quotient of the Quadrature component divided by the In-Phase component; and using the obtained phase offset to decode the binary information conveyed by phase shift keying in the received analog signal.