Limited-diffraction wave generation by approaching theoretical X-wave electrical driving signals with rectangular pulses

The main interest of using limited diffracting waves is motivated by their potential applications in the enlargement of the field depth in acoustic imaging systems, under collimated conditions. In this work, an approach for simplifying the experimental arrangement, needed to generate limited diffracting waves, is proposed. The main idea is to approximate the theoretical X-wave electrical excitations by means of simple driving rectangular pulses. In order to optimize these driving signals in each array annulus, the L2 curve criterion is applied. The differences between theoretical X-wave signals and approximate driving pulses, related to their excitation effects, were minimized by using the time widths and amplitudes of the rectangular pulses as fitting parameters. The good agreement of the source vibration signals and resulting field distributions, provided by the drastic simplification presented here, with those obtained from the classical X-wave excitations, can be justified by the filtering effects induced by the transducer elements in frequency domain. These results suggest the possibility of achieving limited-diffraction waves with relatively simple driving waveforms, which can be implemented with a moderate cost in analogical electronics.