Bidirectional digital signal communication system
First Claim
1. A bidirectional digital signal communication system including a plurality of terminal units in communication with a center unit, wherein each of said terminal units comprises:
- signal generating means for generating digital data spread with a pseudo-noise code;
modulating means for modulating said digital data on a carrier; and
means for transmitting said modulated digital signal to said center unit;
and said center unit comprises;
receiving means for receiving said modulated digital signal;
a pseudo-noise code generator for generating a pseudo-noise code which corresponds to the pseudo-noise code of one of said terminal units;
a multiplier responsive to said receiving means and said pseudo-noise code generator to produce a digital signal de-spread from said pseudo-noise code;
demodulating means connected to said multiplier to reproduce the digital data from said modulated digital signal;
a detector for detecting a maximum level of the digital signal from said multiplier and producing a corresponding level indication signal; and
presetting means including a memory containing a preset code for presetting said pseudo-noise code generator with said preset code in response to said level indication signal.
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Abstract
A bidirectional digital signal communication system includes a plurality of terminal units in communication with a center unit. Each of the terminal units includes a signal generator for generating digital data spread with a PN (pseudo-noise) code, a modulator for modulating the digital data on a carrier, and a transmitter for transmitting the modulated digital signal to the center unit through a transmission line. The center unit includes a receiver for receiving the modulated digital signal, a PN code generator for locally generating a PN code which corresponds to the transmitted PN code, a multiplier supplied with outputs of the receiver and the PN code generator to produce a digital signal de-spread from the PN code, a demodulator connected to the multiplier to reproduce the digital data from the modulated digital signal, and a memory for storing the PN code when the signal level of the multiplier exceeds a predetermined value. The stored PN code is retrieved from the memory to enable rapid synchronization with the next transmission received from the terminal unit.
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Citations
11 Claims
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1. A bidirectional digital signal communication system including a plurality of terminal units in communication with a center unit, wherein each of said terminal units comprises:
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signal generating means for generating digital data spread with a pseudo-noise code; modulating means for modulating said digital data on a carrier; and means for transmitting said modulated digital signal to said center unit; and said center unit comprises; receiving means for receiving said modulated digital signal; a pseudo-noise code generator for generating a pseudo-noise code which corresponds to the pseudo-noise code of one of said terminal units; a multiplier responsive to said receiving means and said pseudo-noise code generator to produce a digital signal de-spread from said pseudo-noise code; demodulating means connected to said multiplier to reproduce the digital data from said modulated digital signal; a detector for detecting a maximum level of the digital signal from said multiplier and producing a corresponding level indication signal; and presetting means including a memory containing a preset code for presetting said pseudo-noise code generator with said preset code in response to said level indication signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification