| 摘要 |
A modulation/demodulation system and method comprising transmitting structure having first and second PN generators which produce distinct, synchron ized, first and second PN sequences. A tapped delay line generates a plurality of symb ols from the second PN sequence, each symbol corresponding to an offset of the secon d PN sequence by one or more chips from the epoch of the first PN sequence. A plurality of output taps are associated with the lapped delay line, with each ta p corresponding to one of the symbols. A symbol selection device associated with t he output taps selects from amongst the symbols based upon one or more message sign al bits. The selected symbols and first PN sequence are applied to separate channel s of a modulator to modulate a carrier signal. At a destination, first and second loc al PN generators generate first and second PN sequences which correspond to the first and second PN sequences in the transmitting structure. A tapped delay line connected to the second local PN generator generates a plurality of symbols which correspond to the symbols in the transmitting structure. An analog baseband signal is recovered fr om the modulated carrier signal and sampled, and each sample is multiplied by the symbo ls from the tapped delay line. The resulting products are filtered, summed and comp ared to a predetermined threshold, and the sum which exceeds the threshold is convert ed to a bit pattern. Consecutive bit patterns are combined to produce a serial data st ream which corresponds to the message signal.
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