Experimental Studies of Two-Way Single Element Time Reversal in a Noisy Waveguide.

摘要

As the United States Navy considers operation closer to shore, it must account for the impact of shallow water ocean environments on the performance of active sonar. Multi-path propagation and high ambient noise in these areas pose a unique detection challenge for current sonar systems. A possible solution for this problem involves the use of processing that is actually enhanced by multi-path propagation, and can perform in the presence of in-band noise. Time-Reverse Acoustics (TRA) has been used with many transducer elements to focus acoustic energy in a very small region. Used as a single element active sonar, it can focus the return of an active pulse at the receiver location. To test the performance of a TRA-based sonar in the presence of noise, ultrasonic signals were used in a laboratory waveguide, so that the scale of wavelength to water depth approximates a shallow channel with a flat, lossy bottom. Several sequences of a traditional sinusoidal pulse and the time- reversed reception were performed with varying noise levels. The gain in detection signal-to-noise ratio (SNR) was on average +7.3+0.8dB using TRA. Further, the TRA processing provided a noticeable detection when noise had completely obscured the reception of the initial pulse.