Ultrasonic pulse compression with one-bit time reversal through multiple scattering

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Abstract
We present experimental results that demonstrate the feasibility of one-bit time reversal even through high-order multiple scattering. A short ultrasonic pulse is transmitted and propagates through a random set of steel rods. The scattered waves are recorded on a 128-channel array, time reversed, and retransmitted through the same medium. The time-reversal mirror takes advantage of multiple scattering to compress the scattered waves into a pulse and focus it back onto the source. Paradoxically, we show that the results are even better when the scattered signals are digitized over one bit. Both temporal and spatial resolutions remain unchanged, while the compressed pulse is amplified by 12 dB, and the signal-to-noise ratio is lowered by 1.2 dB. A statistical model is developed, and its predictions are found to be in good agreement with the experimental results.