Ultrasonic phased array device for acoustic imaging in air

Abstract

Keywords: phased arrays, acoustic imaging, object detection, ultrasound,FDTDThe acoustic imaging technology is widely used for medical purposes and underwaterimaging. In this work, an ultrasonic phased array device is developed by usingpiezoelectric transducers to provide autonomous navigation for robots and mobilityaid for visually impaired people. To perform acoustic imaging, two different lineartransducer arrays are composed with phase-delay focusing phenomenon in order todetect proximate objects with no mechanical scanning.The requirement of half wavelength spacing can not be satisfied between elements,because of using general purpose transducers. The transmitter array isformed by aligning the transducers with minimum spacing between them, which is2.11 times of the wavelength. This placement strategy leads to the occurrence ofunwanted grating lobes in the array response. To eliminate these grating lobes, thereceiver array is formed with a different spacing between each transducer. By formingthe receiver array and the transmitter array non-identical, the directivity patternfor both arrays become different. The off-alignment between two arrays causes thegrating lobes to appear at different places. Since the overall gain of the system isthe product of receiver gain and transmitter gain, the grating lobes diminish for theoverall system.The developed phased array device can transmit/receive ultrasonic waves to/fromthe arbitrary front directions using electronic sector scanning circuits. A detailedscan can be performed to detect the presence of an object or distinguish differentobjects.