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Characteristics of a Discretely Weighted Conical Transducer for Generation of Limited Diffraction Beams

We proposed discretely weighted conical transducers as a simple and practical method of generating Bessel-type limited diffraction beams. In this paper we present the design and fabrication of a discretely weighted conical transducer and examine its capability of generating narrow-beam ultrasound. The transducer has eight annular electrodes, to which position-dependent discrete voltages are applied to create approximately the desired velocity distribution of vibration. It is shown experimentally that an almost uniform -6 dB beamwidth of 6–9 wavelengths is obtained in the axial range of z=10 mm to 200 mm using a transducer 25 mm in diameter operating at 3.6 MHz.