Signal decoding method and apparatus
First Claim
1. 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.
2 Assignments
0 Petitions
Accused Products
Abstract
An apparatus and method for use by a receiver in decoding information sent by phase-shift keying over a carrier frequency is disclosed. The method is well suited for use with power line carrier (PLC) applications as it is adapted to appropriately position the sampling window based on a zero crossing of one of the phases of the power line. The method allows for receipt and processing of information on more than one carrier frequency and from transmitters operating on a phase of the power line that is different than the phase used by the receiver to detect the zero crossings of the alternating current at the power grid frequency on the power line. A number of alternative embodiments are included.
-
Citations
20 Claims
-
1. 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A method of matching an incoming analog signal conveying one of X possible phase shifts on one of Y possible carrier frequencies by:
-
A. detecting a zero crossing of an alternating current at a power grid frequency on a first phase of a power line; B. obtaining a digital representation of an analog signal received at the receiver at a time interval after the detected zero crossing; C. creating a set of products by multiplying the digital representation of the analog signal at the time interval after the zero line crossing by calculated values for the time interval after the zero crossing for various combinations of the X possible phase shifts and the Y possible carrier frequencies; D. storing each of the products in an accumulator used to accumulate products for a particular combination of a particular one of the X possible phase shifts and one of the Y possible carrier frequencies; E. incrementing the time interval by an amount Delta; F. repeating steps B, C, D, and E until the desired set of samples from that analog signal have been digitized, leading to the accumulation of products of the digitized analog signal multiplied by corresponding calculated values for the relevant intervals; G. discerning which of the X possible phase shifts and which of the Y possible carrier frequencies were used to create the analog signal by examining the relative sizes of the various accumulators; and H. decoding the binary information conveyed by the phase shift. - View Dependent Claims (11, 12, 13)
-
-
14. A receiver for decoding binary information conveyed by phase shift keying over a power line carrier, the receiver comprising:
-
a zero crossing detector for detecting a set of zero crossings of an alternating current at a power grid frequency on a first phase of the power line; an input for receiving an analog signal obtained from a pick-up coil connected to one of the phases of the power line carrier; a digital converter to convert a portion of the analog signal received during a sampling window into a series of digital values, the start of the sampling window set based on the detection of a zero crossing and the sampling window set to capture the analog signal sent between two zero crossings of the alternating current at the power grid frequency on the power line phase carrying the analog signal; a multiplier/accumulator module for; multiplying a series of number pairs, each number pair consisting of a digital value a certain offset into the sampling window and a digital value of an ideal cosine wave at a first specific frequency expected at that offset into the sampling window for a transmitter using that specific frequency to convey information via phase shift keying; accumulating as the I value for that first specific frequency, the sum of the products from the multiplication of the sampled digital values and the corresponding ideal cosine wave values for the first specific frequency; multiplying a second series of number pairs, each number pair consisting of the digital value a certain offset into the sampling window and a digital value of an ideal sine wave at a first specific frequency expected at that offset into the sampling window for a transmitter using that specific frequency to convey information via phase shift keying; accumulating as a Q value for that first specific frequency the sum of the products from the multiplication of the sampled digital values and the corresponding ideal sine wave values; and a means for converting the I and Q values for a specific frequency into a conveyed phase shift for the analog signal received during that sampling window for that specific frequency to decode the binary information conveyed by the phase shift. - View Dependent Claims (15, 16, 17, 18, 19, 20)
-
Specification