Power line communications spread spectrum symbol timing and random phasing
First Claim
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1. A system for spread spectrum power line communications comprising:
- a harmonic modulation transmitter for transmitting message bits on a power line exhibiting a synchronous noise spectrum, said transmitter being adapted to;
synthesize a predetermined waveform having M tones, modulate the M tones with data by the transmitter, and interstitially insert the M tones in the power line synchronous noise spectrum, said transmitter having;
carrier wave synthesis means for creating a carrier wave having M frequency lobes between interference lobes,a first timing controller to determine bit periods, said timing controller being synchronized with a power line voltage and including means for estimating a phase of the synchronous noise spectrum and comparing the estimated phase to an externally-supplied phase offset to generate a timing signal,bit encoder means coupled to the timing controller and the carrier wave synthesis means which inverts the carrier waveform for a single bit period for one bit value of said message bit and leaves the carrier wave unchanged for a second message bit value to create an encoded message, anda summation device coupled to the bit encoder for summing the encoded message with existing signals on the power line; and
a harmonic modulation receiver coupled to the power line for receiving a message transmitted by the transmitter in the form of the modulated M tones and having;
a second timing controller coupled to the power line to derive timing signals for a received message and including means for detecting zero crossings of a power line waveform and generating a resynchronization signal for periodically resynchronizing a sampling clock,a sampler responsive to the timing controller which converts a continuous time signal into a series of discrete time samples,a quantizer responsive to the timing controller and coupled to the sampler,a Fourier transform device for performing a Fourier transform on the samples to obtain Fourier coefficients, anda decoder responsive to the Fourier coefficients for recovering the message bits transmitted by the transmitter.
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Abstract
A system for spread spectrum power line communications employs a harmonic modulation (HM) transmitter coupled to the power line for transmitting message bits to an HM receiver. The spread spectrum accommodates a plurality of HM transmitters simultaneously occupying the same bandwidth. The spectrum of HM, in a frequency range above 60 Hz but below the maximum frequency that will carry through a distribution transformer, is ideal in combating carrier synchronous noise since it can be interleaved with the noise harmonics and therefore be effectively spectrally disjoint with the synchronous noise process spectrum.
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Citations
4 Claims
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1. A system for spread spectrum power line communications comprising:
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a harmonic modulation transmitter for transmitting message bits on a power line exhibiting a synchronous noise spectrum, said transmitter being adapted to;
synthesize a predetermined waveform having M tones, modulate the M tones with data by the transmitter, and interstitially insert the M tones in the power line synchronous noise spectrum, said transmitter having;carrier wave synthesis means for creating a carrier wave having M frequency lobes between interference lobes, a first timing controller to determine bit periods, said timing controller being synchronized with a power line voltage and including means for estimating a phase of the synchronous noise spectrum and comparing the estimated phase to an externally-supplied phase offset to generate a timing signal, bit encoder means coupled to the timing controller and the carrier wave synthesis means which inverts the carrier waveform for a single bit period for one bit value of said message bit and leaves the carrier wave unchanged for a second message bit value to create an encoded message, and a summation device coupled to the bit encoder for summing the encoded message with existing signals on the power line; and a harmonic modulation receiver coupled to the power line for receiving a message transmitted by the transmitter in the form of the modulated M tones and having; a second timing controller coupled to the power line to derive timing signals for a received message and including means for detecting zero crossings of a power line waveform and generating a resynchronization signal for periodically resynchronizing a sampling clock, a sampler responsive to the timing controller which converts a continuous time signal into a series of discrete time samples, a quantizer responsive to the timing controller and coupled to the sampler, a Fourier transform device for performing a Fourier transform on the samples to obtain Fourier coefficients, and a decoder responsive to the Fourier coefficients for recovering the message bits transmitted by the transmitter. - View Dependent Claims (2, 3, 4)
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Specification