Communication system for a power distribution line
First Claim
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1. A power line distribution communications system for transmitting selected information on an electric power distribution line transmitting power at a selected power frequency, the power line distribution communications system comprising:
- a transmitter coupled to the electric power distribution line comprising;
an information signal generator providing an information signal;
first reference means for detecting a power frequency of an alternating current transmitted on the electric power distribution line;
a first modulator connected to the information signal generator for taking the information signal as a modulating input for modulation of a subcarrier signal, the first modulator being operably connected to the first reference means such that the subcarrier signal has a frequency derived from and numerically referenced to the detected power frequency; and
a second modulator taking the subcarrier signal as a modulating input for modulation of an output carrier signal, the output carrier signal having a frequency higher than the subcarrier signal; and
a receiver coupled to the electric power distribution line comprising;
second reference means for detecting the power frequency of the alternating current transmitted on the electric power distribution line and providing a reference signal indicative of the detected power frequency;
means for demodulating the subcarrier signal from the output carrier signal; and
means operably connected to the second reference means for demodulating the information signal from the subcarrier signal using the reference signal.
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Abstract
The invention provides a layered modulation data communication systems characterized by numerous, asynchronous data transmitters operating on a power line. Data is modulated onto relatively low frequency subcarriers. Subcarriers are used to modulate carriers centered on a common frequency. The subcarriers are frequency division multiplexed. Data is recovered by demodulating the subcarriers from the carriers and subsequently demodulating the data from the subcarriers.
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Citations
21 Claims
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1. A power line distribution communications system for transmitting selected information on an electric power distribution line transmitting power at a selected power frequency, the power line distribution communications system comprising:
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a transmitter coupled to the electric power distribution line comprising; an information signal generator providing an information signal; first reference means for detecting a power frequency of an alternating current transmitted on the electric power distribution line; a first modulator connected to the information signal generator for taking the information signal as a modulating input for modulation of a subcarrier signal, the first modulator being operably connected to the first reference means such that the subcarrier signal has a frequency derived from and numerically referenced to the detected power frequency; and a second modulator taking the subcarrier signal as a modulating input for modulation of an output carrier signal, the output carrier signal having a frequency higher than the subcarrier signal; and a receiver coupled to the electric power distribution line comprising; second reference means for detecting the power frequency of the alternating current transmitted on the electric power distribution line and providing a reference signal indicative of the detected power frequency; means for demodulating the subcarrier signal from the output carrier signal; and means operably connected to the second reference means for demodulating the information signal from the subcarrier signal using the reference signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of communicating information from a plurality of transmitters to a remote receiver station along a common electric power distribution line transmitting power at a selected power frequency, wherein a transmitter is provided at each of a plurality of spaced-apart transmitting locations, the method comprising the steps of:
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obtaining the information to be transmitted; generating an information signal at each transmitter location using the information to be transmitted; detecting a power frequency of an alternating current transmitted on the electric power distribution line at each transmitting location and providing an output signal as a function of the frequency of the alternating current; generating a subcarrier signal for each of the information signals using the output signal, the subcarrier signal having a frequency derived from and numerically referenced to the detected power frequency; modulating each subcarrier signal as a function of its associated information signal; modulating an output carrier signal with each subcarrier signal, the output carrier signal having a frequency higher than the subcarrier signal; transmitting the output carrier signals over the electric power distribution line; detecting the power frequency of the alternating current transmitted on the electric power distribution line at a receiving location and providing a reference signal indicative of the detected power frequency; recovering all carrier signals from the power distribution line; demodulating the subcarrier signals from the output carrier signals; demodulating the information signals from the subcarrier signals using the reference signal to provide associated output signals; and interpreting each of the output signals to obtain the information from each transmitting location. - View Dependent Claims (16, 17, 18)
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19. A power line distribution communications system for transmitting selected information on an electric power distribution line transmitting power at a selected power frequency, the power line distribution communications system comprising:
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a transmitter coupled to the electric power distribution line comprising; an information signal generator providing an information signal; first reference means for detecting a power frequency of an alternating current transmitted on the electric power distribution line; a first modulator connected to the information signal generator for taking the information signal as a modulating input for modulation of a subcarrier signal; and a second modulator connected to the first modulator for taking the subcarrier signal as a modulating input for modulation of an output carrier signal, the second modulator being operably connected to the first reference means such that the output carrier signal has a frequency derived from and numerically referenced to the detected power frequency and a frequency higher than the subcarrier signal; and a receiver coupled to the electric power distribution line comprising; second reference means for detecting the power frequency of the alternating current on the electric power distribution line and providing a reference signal indicative of the detected power frequency; means for demodulating the subcarrier signal from the output carrier signal; and means operably connected to the second reference means for demodulating the information signal from the subcarrier signal using the reference signal. - View Dependent Claims (20)
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21. A power line distribution communications system for transmitting selected information on an electric power distribution line transmitting power at a selected power frequency, the power line distribution communications system comprising:
a transmitter coupled to the electric power distribution line comprising; an information signal generator providing an information signal; first reference means for detecting a power frequency of an alternating current transmitted on the electric power distribution line; a first modulator connected to the information signal generator for taking the information signal as a modulating input for modulation of a subcarrier signal, the first modulator being operably connected to the first reference means such that the subcarrier signal having a bandwidth less than one hertz and a frequency derived from and numerically referenced to the detected power frequency; and a second modulator taking the subcarrier signal as a modulating input for modulation of an output carrier signal, the second modulator being operably connected to the first reference means such that the output carrier signal has a frequency derived from and numerically referenced to the detected power frequency and higher than the subcarrier signal; and a receiver coupled to the electric power distribution line comprising; second reference means for detecting the power frequency of the alternating current transmitted on the electric power distribution line and providing a reference signal indicative of the detected power frequency; means for demodulating the subcarrier signal from the output carrier signal; and means operably connected to the second reference means for demodulating the information signals from the subcarrier signal using the reference signal.
Specification