Acoustic devices for time-multiplexed communication

Claim 1

A transmitter for time-multiplexed communication utilizing complementary non-interacting codes, comprising: an acoustic surface-wave device, which provides two parallel signal propagation paths on its surface, comprising; a substrate, capable of propagating acoustic surface waves; a pair of coded interdigitated electrode structures disposed upon the substrate, one structure in each of the propagation paths, one structure coded according to one member of a complementary pair, the other structure coded according to the other member of a complementary pair, each coded electrode structure transducing an acoustic wave propagating in its respective propagation path into an output electrical signal which may be transmitted externally of the substrate by means of output leads; and two pairs of uncoded interdigitated electrode structures disposed upon the substrate, one pair in each of the two propagation paths on each side of the coded electrode structures; the acoustic surface-wave device having the property that a single electrical pulse applied to the uncoded electrode structure results in a multiple-pulse (or multi-sample) electrical output signal at the output leads; a first signal source for generating pulses, whose output is connected to those two of the uncoded electrode structures which are on the same side of the coded electrode structures; one structure from each pair of uncoded electrode structures, the signal source generating a stream of pulses; a second signal source, also for generating pulses, whose output is connected to the other two uncoded electrode structures, the second signal source generating a stream of pulses in the intervals of time when the first signal source is not generating a stream of pulses; a signal source switch, whose input terminals are connected to the outputs of the first and second signal sources and whose output terminals are connected to, respectively, each pair of the uncoded electrode structures; a multiplexing double-pole double-throw switch, for alternately switching an output signal from each of the coded electrical structures to each of two transmit channels; and a timing and control apparatus connected to the first and second signal sources and to the signal source and multiplexing switches, which control (1) the time periods, or intervals, during which the first and second signal sources are alternately energized, and (2) the switching of the arms of the switches from one position to the other in synchronism with the alternate enegization of the signal sources; with the result that a stream of intermittent pulses from the signal sources becomes a pair of more or less continuous streams of samples which are sent via two transmit channels, with channel exchange occurring at intervals determined by the timing control, the streams of output samples concealing coded information.