Time-reversal communication through a highly scattering medium

Abstract

An ultrasonic time-reversal array system is used to transmit communication signals across an aluminum slab with 195 holes drilled through it. Multiple scattering and mode conversion stretches a 0.4-microsecond transmitted pulse into a received signal that rings for over 75 microseconds with little attenuation. Communication through such a medium is subject to severe multipath distortion. Four variations of a time-reversal receiver are used to mitigate multipath distortion and allow error-free transmission of a variety of bit sequences [see Candy et al. J. Acoust. Soc. Am. Suppl. 115, 2367 (2004)]. Performance of point-to-point receivers constructed from different segments of the Green’s function (channel response) is compared. [This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.]