Power line carrier FSK data system
First Claim
1. A data communication system for communicating data between a first and a second location over an electrical power line which also carries alternating current electrical power having a frequency fPC, the system comprising:
- transmitter means at the first location for providing to the power line a periodic frequency shift keyed (FSK) signal representing a serial input stream of binary bits, the FSK signal having a frequency fFSK and a predetermined data rate, wherein fFSK is greater than the data rate, and the date rate is greater than fPC, the transmitter means comprising;
first means for deriving from the power line a signal having frequency fPC ;
first phase locked loop means locked to the signal having frequency fPC for synthesizing the FSK signal and a transmitter timing signal which determines the data rate, wherein the first phase locked loop means comprises;
first oscillator means for producing the FSK signal with a frequency fFSK which is a function of a first control signal and a second control signal;
divider means for dividing the FSK signal to produce a synthesized signal having a frequency fSPC which is equal to fPC when the first phase locked loop means is in lock and to produce the transmitter timing signal which defines a bit time period for each bit of the serial input stream;
first phase detector means for providing a first phase detector output which is a function of a phase comparison of the signal having frequency fPC and the synthesized signal having frequency fSPC ; and
means for providing the first control signal as a function of the first phase detector output;
control means for providing the second control signal during each bit time period which causes the first oscillator means to produce the FSK signal with a frequency fFSK which is greater than a reference frequency fO to represent a bit of the input stream having first binary state and is less than fO to represent a bit of the input stream having a second binary state;
means for superimposing the FSK signal onto the power line; and
receiver means at the second location for providing a periodic serial output stream of binary bits, the receiver means comprising;
second means for deriving from the power line a signal having frequency fPC ;
second phase locked loop means locked to the signal having frequency fPC for synthesizing a reference signal having frequency fO and a receiver timing signal which determines the data rate, wherein the second phase locked loop means comprises;
second oscillator means for producing the reference signal with a frequency fO which is a function of a control signal;
divider means for dividing the reference signal to produce a synthesized signal having a frequency fSPC which is equal to fPC when the second phase locked loop means is in lock and to produce a receiver timing signal which defines a bit time period for each bit of the serial output stream;
second phase detector means for providing a second phase detector output which is a function of a phase comparison of the signal having frequency fPC and the signal having frequency fSPC ; and
means for providing the control signal to the second oscillator means as a function of the second phase detector output;
means for deriving the FSK signal from the power line; and
frequency discriminator means responsive to the receiver timing signal for providing the periodic serial output stream of binary bits as a function of periodic comparison of the FSK signal and the reference signal.
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Accused Products
Abstract
A frequency shift keyed (FSK) data transmission system utilizes existing power lines to transmit data by superimposing a high frequency FSK signal on the power line carrier. A transmitter includes a phase locked loop which is locked on the power line carrier frequency and which synthesizes the FSK signal and a timing signal which defines the data rate of the transmitter. As each bit is transmitted, an oscillator control signal either speeds up or slows down the loop oscillator temporarily to produce the FSK signal. A receiver demodulates the data transmission from the power line by separating a power line carrier frequency component and a FSK signal component. The receiver includes a phase locked loop which locks onto the power line carrier frequency and which synthesizes a reference frequency and a timing signal which defines the data rate of the receiver. The receiver also includes a frequency discriminator circuit which compares the FSK signal with the synthesized reference signal and produces a digital data output signal at the data rate synthesized by the phase locked loop.
108 Citations
17 Claims
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1. A data communication system for communicating data between a first and a second location over an electrical power line which also carries alternating current electrical power having a frequency fPC, the system comprising:
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transmitter means at the first location for providing to the power line a periodic frequency shift keyed (FSK) signal representing a serial input stream of binary bits, the FSK signal having a frequency fFSK and a predetermined data rate, wherein fFSK is greater than the data rate, and the date rate is greater than fPC, the transmitter means comprising; first means for deriving from the power line a signal having frequency fPC ; first phase locked loop means locked to the signal having frequency fPC for synthesizing the FSK signal and a transmitter timing signal which determines the data rate, wherein the first phase locked loop means comprises; first oscillator means for producing the FSK signal with a frequency fFSK which is a function of a first control signal and a second control signal; divider means for dividing the FSK signal to produce a synthesized signal having a frequency fSPC which is equal to fPC when the first phase locked loop means is in lock and to produce the transmitter timing signal which defines a bit time period for each bit of the serial input stream; first phase detector means for providing a first phase detector output which is a function of a phase comparison of the signal having frequency fPC and the synthesized signal having frequency fSPC ; and means for providing the first control signal as a function of the first phase detector output; control means for providing the second control signal during each bit time period which causes the first oscillator means to produce the FSK signal with a frequency fFSK which is greater than a reference frequency fO to represent a bit of the input stream having first binary state and is less than fO to represent a bit of the input stream having a second binary state; means for superimposing the FSK signal onto the power line; and receiver means at the second location for providing a periodic serial output stream of binary bits, the receiver means comprising; second means for deriving from the power line a signal having frequency fPC ; second phase locked loop means locked to the signal having frequency fPC for synthesizing a reference signal having frequency fO and a receiver timing signal which determines the data rate, wherein the second phase locked loop means comprises; second oscillator means for producing the reference signal with a frequency fO which is a function of a control signal; divider means for dividing the reference signal to produce a synthesized signal having a frequency fSPC which is equal to fPC when the second phase locked loop means is in lock and to produce a receiver timing signal which defines a bit time period for each bit of the serial output stream; second phase detector means for providing a second phase detector output which is a function of a phase comparison of the signal having frequency fPC and the signal having frequency fSPC ; and means for providing the control signal to the second oscillator means as a function of the second phase detector output; means for deriving the FSK signal from the power line; and frequency discriminator means responsive to the receiver timing signal for providing the periodic serial output stream of binary bits as a function of periodic comparison of the FSK signal and the reference signal. - View Dependent Claims (2, 3)
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4. A transmitter of a periodic frequency shift keyed (FSK) signal carried on an electrical power line which also carries alternating current electrical power having a frequency fPC, the FSK signal having a frequency fFSK during each of a sequence of bit time periods which represent binary bits to be transmitted, the transmitter comprising:
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means for deriving from the power line an input signal having frequency fPC ; phase locked loop means locked to the input signal having frequency fPC for synthesizing the FSK signal and a transmitter timing signal which determines the bit time periods, wherein the phase locked loop means comprises; oscillator means for producing the FSK signal with a frequency fFSK which is a function of a first control signal and a second control signal; divider means for dividing the FSK signal to produce a synthesized signal having a frequency fSPC which is equal to fPC when the first phase locked loop means is in lock and to produce the transmitter timing signal which defines the bit time period for each bit to be transmitted; phase detector means for providing a first phase detector output which is a function of a phase comparison of the signal having frequency fPC and the synthesized signal having frequency fSPC ; and means for providing the first control signal as a function of the first phase detector output; control means for providing the second control signal during each bit time period which causes the oscillator means to produce the FSK signal with a frequency fFSK which is greater than a reference frequency fO if the bit to be transmitted has a first binary state and which is less than fO if the bit to be transmitted has a second binary state; and means for providing the FSK signal to the power line. - View Dependent Claims (5)
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6. A receiver for demodulating a periodic frequency shift keyed (FSK) signal carried on an electrical power line which also carries alternating current electrical power having a frequency fPC to produce a periodic binary output signal, at a predetermined data rate, which has a first state when the FSK signal has a frequency fFSK which is greater than a reference frequency fO and which has a second state when fFSK is less than fO, wherein frequencies fO and fFSK are greater than the data rate and wherein the data rate is greater than fPC, the receiver comprising:
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means for deriving from the power line a first input signal having the frequency fPC ; means for deriving from the power line a second input signal having the frequency fFSK ; phase locked loop means for locking onto frequency fPC of the first input signal and producing a first synthesized signal having the frequency fO and a second synthesized signal having a frequency which is related to the predetermined data rate;
the phase locked loop comprising;oscillator means for producing the first synthesized signal having frequency fO which is a function of an oscillator control signal; divider means for dividing the frequency of the first synthesized signal to produce the second synthesized signal and a third synthesized signal of frequency fSPC which is equal to fPC when the phase locked loop is in lock; loop phase detector means for providing a phase detector output which is a function of a phase comparison of the first input signal and the third synthesized signal; and means for providing the oscillator control signal as a function of the phase detector output to cause the third synthesized signal to have frequency fSPC =fPC and be locked in phase with the first input signal; and frequency discriminator means for providing the binary output signal, at the data rate determined by the second synthesized signal, as a function of a comparison of the second input signal and the first synthesized signal. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification