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Spread spectrum communications system
| Details |
Inventors: Nakamura, Masaru;
Assignee: Ricoh Company, Ltd. (Tokyo, JP)
Primary Examiner: Gregory; Bernarr E.
Assistant Examiner:
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt
A spread spectrum communications system includes: a transmitter having an input information a modulator for generating a spread spectrum signal in accordance with an input information signal together with a pseudonoise clock signal used to generate a first pseudonoise signal formed of a plurality of chips, a switch for switching on and off a locally generated carrier signal of said input information signal in accordance with the spread spectrum signal, a first means for inverting a phase of the spread spectrum signal when the value of the pseudonoise signal is equal to one, a second means for multiplying the inverted-phase spread spectrum signal by the carrier signal so as to produce a transmit signal at an output of the second means, and an output means for outputting the transmit signal from the second means so that the transmit signal is transmitted from the transmitter; and a receiver which receives the transmit signal from the transmitter, the receiver having a detector for obtaining a baseband signal from the transmit signal received at the detector, and a demodulation part for demodulating the baseband signal with a second pseudonoise signal which is generated synchronously with the transmit signal, so as to reproduce the input information signal. |
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DETAILED DESCRIPTION Accordingly, it is a general object of the present invention to provide an improved spread spectrum communications system in which the above described problems are eliminated.
Another, more specific object of the present invention is to provide an improved technique for generating a spread spectrum signal in which the carrier is suppressed enough which signal is transmitted and received by a spread spectrum communications system.
Still another object of the present invention is to provide a spread spectrum communications system in which the above signal generating technique is applied to spread spectrum modulation and demodulation of the spread spectrum communications system.
A further object of the present invention is to provide a spread spectrum communications system which does not require the synchronization of the carrier signal with the clock signal.
The above mentioned objects of the present invention are achieved by a spread spectrum communications system which includes: a transmitter having an input information, a modulation part for generating an ss signal in accordance with the input information, together with a clock signal which is used to generate a first pn signal formed of a plurality of chips, a switch for switching on and off a carrier signal in accordance with the ss signal of the modulation part, a first part for inverting a phase of the ss signal of the modulation part when the first pn signal is continuously at a high value from chip to chip, a second part for combining the inverted-phase ss signal of the first part with the carrier signal of the switch to produce a transmit signal, and an output part for outputting the transmit signal so that the transmit signal is transmitted from the transmitter; and a receiver which receives the transmit signal from the transmitter, the receiver having a detector for obtaining a baseband signal from the transmit signal received at the detector, and a demodulation part for demodulating the baseband signal with a second pn signal which is generated synchronously with the transmit signal, so as to reproduce data corresponding to the input information
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Telecommunications 
