Spread spectrum communication device
First Claim
1. A spread spectrum communication method for communication data by spreading spectrum thereof, using a PN code, comprising:
- A. on the transmitter side, a step of code phase shift keying modulating each bit of data to be transmitted, including;
a) a step of generating a first PN code train consisting of a repetition of first PN codes with a predetermined period and a second PN code train shifted by a predetermined phase with respect to said first PN codes; and
b) a step of generating a spread-spectrum-modulated output by selecting either said first PN code train or said second PN code train according to each said bit of said data to be transmitted; and
B. on the receiver sidea) a step of generating a correlation-modulated output by correlation-demodulating a received input with a third PN code train consisting of a repetition of second PN codes inverted in time with respect to said first PN codes with said predetermined period; and
b) a step of code phase shift keying modulating said correlation-demodulated output, including;
i) a step of generating a first time window pulse train consisting of a pulse train with a period, which is a half of said predetermined period, in synchronism with said correlation-demodulated output, a second time window pulse train consisting of a pulse train shifted by a predetermined phase with respect to said first time window pulse train and a bit duration specifying signal indicating a duration of each said bit of said transmitted data;
ii) a step of generating of two-valued pulse output obtained by converting said correlation-demodulated output with a predetermined threshold;
iii) a step of detecting a difference between a number of pulses of said two-valued pulse output within said first time window pulse train and a number of pulses of said two-valued pulse output within said second time window pulse train in the duration of each said bit; and
iv) a step of determining a state of each said bit, depending on a polarity of said difference.
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Abstract
In a spread spectrum communication system for communicating data by spreading spectrum thereof, using PN codes, on the transmitter side, a first modulated output portion, which is spread-spectrum-modulated, containing no data to be transmitted and a second modulated output portion, which is spread-spectrum-modulated, following the first modulated output portion and containing data to be transmitted are generated; and the second modulated output portion is transmitted with a low electric power and the first modulated output portion with a high electric power. On the receiver side, a correlation-demodulated output is generated by correlation-demodulating a received input; and from the correlation-demodulated output consisting of a first correlation-demodulated output portion corresponding to the first modulated output portion and a second correlation-demodulated output portion corresponding to the second modulated output portion the first correlation-demodulated output portion is detected. Further timing signal serving as a reference for an operation on the receiver side is generated, starting from the first correlation-demodulated output portion.
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Citations
7 Claims
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1. A spread spectrum communication method for communication data by spreading spectrum thereof, using a PN code, comprising:
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A. on the transmitter side, a step of code phase shift keying modulating each bit of data to be transmitted, including; a) a step of generating a first PN code train consisting of a repetition of first PN codes with a predetermined period and a second PN code train shifted by a predetermined phase with respect to said first PN codes; and b) a step of generating a spread-spectrum-modulated output by selecting either said first PN code train or said second PN code train according to each said bit of said data to be transmitted; and B. on the receiver side a) a step of generating a correlation-modulated output by correlation-demodulating a received input with a third PN code train consisting of a repetition of second PN codes inverted in time with respect to said first PN codes with said predetermined period; and b) a step of code phase shift keying modulating said correlation-demodulated output, including; i) a step of generating a first time window pulse train consisting of a pulse train with a period, which is a half of said predetermined period, in synchronism with said correlation-demodulated output, a second time window pulse train consisting of a pulse train shifted by a predetermined phase with respect to said first time window pulse train and a bit duration specifying signal indicating a duration of each said bit of said transmitted data; ii) a step of generating of two-valued pulse output obtained by converting said correlation-demodulated output with a predetermined threshold; iii) a step of detecting a difference between a number of pulses of said two-valued pulse output within said first time window pulse train and a number of pulses of said two-valued pulse output within said second time window pulse train in the duration of each said bit; and iv) a step of determining a state of each said bit, depending on a polarity of said difference. - View Dependent Claims (2, 3)
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4. A spread spectrum communication device for communication data by spreading spectrum thereof, using PN codes, consisting of:
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A. a transmitter comprising; a) PN code train generating means for generating a first PN code train consisting of a repetition of first PN codes with a predetermined period; b) shift register means for generating a second PN code train by delaying said first PN code train by a predetermined phase; c) switching means for generating a spread-spectrum-modulated output by selecting either said first PN code train or said second PN code train according to a state of each bit of data to be transmitted; and d) transmitting means for transmitted said spread-spectrum-modulated output; and B. a receiver comprising; a) correlator means for generating a correlation-demodulated output by correlation-demodulating a received input with a third PN code train consisting of a repetition of second PN codes inverted in time with respect to said first PN codes with said predetermined period; b) timing circuit means including first pulse generating means for generating a first time window pulse train having a period which is half of said predetermined period, shift register means for generating a second time window pulse train by delaying said first time window pulse train by a predetermined phase, and logic means for generating a bit duration ending pulse indicating an end of the duration of each said bit of said transmitted data; c) two-valued data forming means for generating a two-valued pulse output obtained by converting said correlation-demodulated output into two-valued data with a predetermined threshold; d) first gate means for passing pulses of said two-valued pulse output within said first time window pulse train and second gate means for passing pulses of said two-valued pulse output within said second time window pulse train; e) up/down counter means receiving pulses from said first gate means and pulses from said second gate means as an upcount input and a down-count input, respectively; and f) logic means for outputting a polarity of a count output just before the generation of said bit duration ending pulse as a state of said each bit. - View Dependent Claims (5, 6, 7)
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Specification