Spread spectrum power line communications

A spread spectrum power line carrier frequency communications method comprising the steps of:

• connecting a plurality of slave units and one master unit to a common power line,
• checking by each slave unit for the presence of a signal transmitted by any other slave unit and flowing through said power line when each slave unit needs to transmit a signal,
• in the event that a checking slave unit detects transmission by another slave unit, not transmitting a data signal therefrom, but in the event that a checking slave unit does not detect a data signal, a transmitting slave unit, transmitting a data signal, a transmitting slave unit adding a sequential transmission code having the same code pattern as that of a first maximum length sequence transmission code of said data signal and a phase difference inherent in each slave unit to the modulated data signal which is obtained by subjecting a transmitting data signal to spread spectrum modulation with said first maximum length sequence transmission code, said transmitted data signal being transmitted to said master unit through said power line,
• receiving by said master unit the spread spectrum modulated signal transmitted through said power line and demodulating it, and
• said master unit discriminating each transmitting slave unit from the others using the phase difference between the maximum length sequence used when the spread spectrum modulated signal is produced and what is added to the spread spectrum modulated signal and transmitted through said power line.

A system for spread spectrum power line carrier frequency communications, comprising:

• a plurality of slave units and one master unit, each slave unit including:
• first and second maximum length sequence generator circuits for generating maximum length sequences having phase differences inherent in said slave units and identical code patterns, respectively, with said first and second maximum length sequence generator circuits having identical clock pulses as inputs,
• a modulator for spread spectrum modulating a transmitting data signal with the maximum length sequence produced by the first maximum length sequence generator circuit,
• a correlator for correlating a signal supplied by a power line through a coupler with the maximum length sequence produced by said second maximum length sequence generator circuit,
• a synchronizing control circuit for judging the presence of a signal transmitted by any other slave unit from the presence of a correlative output of said correlator when the phases of the maximum length sequence generated by said first maximum length sequence generator circuit and said second maximum length sequence generator circuit are varied,
• a clock control circuit controlled by said synchronizing control circuit for sequentially shifting the phase of the identical clock pulses when the transmission of a data signal is needed, and
• a switch circuit for sending a transmitting signal to said power line through said coupler, said transmitting signal being a combination of the spread spectrum modulated signal produced by said modulator only when said synchronizing control circuit has judged that no signal is transmitted by any other slave unit and the maximum length sequence produced by said second maximum length sequence generator circuit.

A system for spread spectrum power line carrier frequency communications, comprising:

• a plurality of slave units and one master unit, said master unit comprising:
• a first maximum length sequence generator circuit and a second maximum length sequence generator circuit responsive to respective identical clock pulses for respectively producing maximum length sequences having the same code patterns as those produced by said slave unit used for spread spectrum modulation,
• a clock control circuit for outputting said respective identical clock pulses and for sequentially shifting the clock pulse phase supplied to said first and second maximum length sequence generator circuits,
• a synchronizing control circuit for controlling said clock control circuit to sequentially shift the clock pulse phase,
• a correlator for obtaining the correlation of a receiving signal supplied from a power line through a coupler to the maximum length sequence produced by said second maximum length sequence generator circuit and for sequentially shifting the phase of the maximum length sequence produced by said second maximum length sequence generator circuit, a correlative output being used to stop the shifting of the clock pulse phase by said synchronizing control circuit,
• a phase shift control circuit for sequentially shifting the phase of the maximum length sequence produced by said first maximum length sequence generator circuit while the correlative output is being generated by said correlator, and
• a demodulator for producing a receiving signal by demodulating the receiving spread spectrum modulated signal supplied by said coupler using the maximum length sequence produced by said first maximum length sequence generator circuit and stopping the operation of said phase shift control circuit according to said signal received.

A spread spectrum power line carrier frequency line lock communications method comprising the steps of:

• generating first and second clock pulses in each of a transmitter and a receiver, said first clock pulse being synchronized in phase with an A.C. supply flowing in a power line used as a transmission line and having a frequency (K.times.N) times as high as that of said A.C. supply, and said second clock pulse being synchronized in phase with said A.C. supply and having a frequency K/2 times as high as that of said A.C. supply, where N represents the maximum period length of a maximum length sequence generated in said transmitter and K represents an integer;
• generating said maximum length sequence with said first clock pulse providing a basic timing thereof, said maximum length sequence having a generation period coincident with the period of "H" and "L" of said second clock pulse;
• spread spectrum modulating transmission data and supplying it onto said power line;
• and
• spread spectrum demodulating a received modulated signal from said power line by using a maximum length sequence the same as said maximum length sequence synchronized with said A.C. supply.

A line lock communication apparatus for a spread spectrum power line carrier frequency communication system, comprising:

• a transmitter including a line lock clock generator for generating a first clock pulse which is synchronized in phase with an A.C. supply flowing in a power line utilized as a transmission line, said first clock pulse having a frequency K.times.N times as high as that of said A.C. supply, where N represents the maximum period length of a maximum length sequence used in said transmitter and K represents an integer, said line lock clock generator also generating a second clock pulse which is synchronized in phase with said A.C. supply and which represents a generation period of said maximum length sequence by changing its level between "H" and "L", a maximum length sequence generator for generating said maximum length sequence, said maximum length sequence having said first clock pulse as a basic timing thereof and having a period synchronized with a change in level between "H" and "L" of said second clock pulse, a spread spectrum modulator for product-modulating transmission data using said maximum length sequence generated by said maximum length sequence generator to thereby generate a modulated signal in which said transmission data are spread spectrum modulated over a wide band, and a coupler for supplying said spread spectrum modulated signal onto said power line;
• and
• a receiver including a line lock clock generator and a maximum length sequence generator having the same construction as that of said transmitter, a coupler for receiving said modulated signal from said power line, and a spread spectrum demodulator for demodulating said modulated signal transferred from said coupler using said maximum length sequence generated from said maximum length sequence generator so as to provide reception data.

A spread spectrum power line carrier frequency communications system, comprising:

• a transmitter providing a maximum length sequence and transmission data which are product-modulated so that said transmission data generate a spread spectrum modulated signal which is supplied onto a power line, and
• a receiver for receiving said modulated signal from said power line and product-demodulating said modulated signal using a maximum length sequence that is the same as that used in said transmitter to thereby obtain reception data,
• wherein said spread spectrum modulated signal in said transmitter is modulated again by using a clock pulse and is then transmitted to said receiver through said power line, and
• wherein a frequency of a clock pulse used when said maximum length sequence is generated, a frequency of said clock pulse used when said spread spectrum modulated signal is modulated again, and a maximum code length of said maximum length sequence are of values at which a spectrum distribution of a transmitter output does not affect other equipment connected to said power line.

A spread spectrum power line carrier frequency communications apparatus, comprising:

• a transmitter including a clock generator for generating a first clock pulse, a maximum length sequence generator for generating a maximum length sequence in response to said first clock pulse produced by said clock generator, a spread spectrum modulator for performing spread spectrum modulation of transmission data using said maximum length sequence, a clock oscillator for generating a second clock pulse, a modulator for modulating an output of said spread spectrum modulator using said second clock pulse, and a coupler for transferring the modulated output to said power line;
• and
• a receiver connected to said transmitter through a power line utilized as a transmission line, said receiver including a coupler for receiving the modulated output on said power line, a clock generator for generating a first clock pulse having the same frequency as said first clock pulse generated in said transmitter, a maximum length sequence generator for generating a maximum length sequence having the same code pattern as said maximum length sequence generated in said transmitter by using said first clock pulse generated in said clock generator of said receiver, a second clock oscillator for generating a second clock pulse having the same frequency as said second clock pulse generated in said clock oscillator of said transmitter, a demodulator for demodulating an output of said coupler connected to said power line by using said second clock pulse generated by said second clock oscillator to thereby isolate a spread spectrum modulated signal, and a spread spectrum demodulator for demodulating an output of said demodulator by using said maximum length sequence generated by said maximum length sequence generator to thereby isolate reception data, wherein respective frequencies of said first and second clock pulses and the maximum code length of said maximum length sequence in each of said transmitter and said receiver are of values at which a spectrum distribution of said transmission output transmitted from said transmitter has no influence on other equipment connected to said power line.

A spread spectrum power line communications system, comprising:

• a transmitter unit and a receiver unit which are connected through power lines utilized as a transmission path, said transmitter unit comprising:
• a clock pulse generating circuit for producing a clock pulse,
• a transmitting maximum length sequence generating circuit for producing a maximum length sequence with the aid of said clock pulse produced by said clock pulse generating circuit,
• a modulator for spread spectrum modulating data to be transmitted using said maximum length sequence, and
• a coupler for supplying the resulting spread spectrum modulated signal to said power lines;
• and
• said receiver unit comprising:
• a clock pulse generating circuit for generating a clock pulse synchronous with said clock pulse in said transmitter unit,
• a receiving maximum length sequence generating circuit for producing a maximum length sequence which is the same as the maximum length sequence in said transmitter unit, with the aid of said clock pulse produced by said clock pulse generating circuit of said receiver unit,
• a coupler for receiving said modulation signal supplied through said power lines,
• a voltage-controlled variable gain receiving amplifier for amplifying an output of said coupler,
• a clock pulse phase swinging circuit for stepping the phase of said clock pulse produced by said clock pulse generating circuit of said receiver unit in a predetermined direction to thereby swing the phase of said clock pulse,
• a level controlling maximum length sequence generating circuit for producing a level controlling maximum length sequence which is the same in code pattern as said maximum length sequence generated by said receiving maximum length sequence generating circuit, with the aid of the clock pulse provided by said clock pulse phase swinging circuit,
• a correlation unit for correlating said level controlling maximum length sequence with an output signal of said voltage-controlled variable gain receiving amplifier,
• a detecting and smoothing circuit for detecting and smoothing an output of said correlation unit,
• an error detecting circuit for applying the difference between an output signal of said detecting and smoothing circuit and a reference value as a level control signal to said voltage-controlled variable gain receiving amplifier, and
• a spread spectrum demodulator for demodulating the received signal from said variable gain receiving amplifier by multiplicative demodulation using said maximum length sequence supplied by said receiving maximum length sequence generating circuit.

A power line transmission type spread spectrum communications method, comprising the steps of:

• on a data transmitting side, subjecting a maximum length sequence and transmission data to multiplication modulation so as to produce a modulation signal in which said transmission data are spread in the form of a spectrum,
• supplying said modulation signal to power lines,
• on the data receiving side, subjecting a maximum length sequence which is the same as that produced at the time of data transmission and reception data of said modulation signal received through said power lines to multiplication demodulation,
• correlating said modulation signal supplied to said power lines with said transmitted maximum length sequence in a correlating means,
• detecting and smoothing a correlation output of said correlation means, and
• when the level of a signal which is obtained by detecting and smoothing said correlation output becomes lower than a reference value, switching a frequency band used for said modulation signal.

A power line transmission type spread spectrum communication system, comprising a transmitter unit and a receiver unit which are connected to each other through power lines which are utilized as a data transmission path,

• said transmitting unit comprising:
• a clock pulse generating circuit for generating a clock pulse;
• a maximum length sequence generating circuit for generating a maximum length sequence with the aid of said clock pulse produced by said clock pulse generating circuit;
• a divider for dividing said clock pulse so as to produce a frequency division output of said clock pulse;
• a selector for selecting between said clock pulse produced by said clock pulse generating circuit and said frequency division output of said divider;
• modulation means for subjecting an output signal of said selector, said maximum length sequence and transmission data to multiplication modulation;
• and
• a first coupler for supplying an output of said modulator to said power lines;
• and
• said receiver unit comprising:
• a second coupler for receiving a modulation signal supplied to said power lines by said first coupler;
• a correlation unit for obtaining the correlation between an output signal of said second coupler and said maximum length sequence of said transmitting unit;
• a rectifying and smoothing circuit for rectifying and smoothing an output signal of said correlation unit;
• a switching control circuit for switching said selector when the level of an output signal of said rectifying and smoothing circuit becomes lower than a reference value;
• a synchronous maximum length sequence generating circuit for producing a demodulating maximum length sequence which is the same as the maximum length sequence used for the spread spectrum modulation of transmission data on the side of the transmitter unit;
• and
• a demodulator in which an output signal of said coupler is multiplied by said demodulating maximum length sequence to obtain reception data.