Air-coupled 40-KHZ ultrasonic 2D-phased array based on a 3D-printed waveguide structure

We present a fully-populated 8×8 2D-phased array, capable of emitting directed air-coupled ultrasound at 40 kHz with λ/2-pitch size for zero grating lobes. In comparison to our previous work, in which we describe a 1D-phased array, we use 3D-printing to realize the wave guide structure. Besides the key idea to separate the vibrating from the acoustic aperture, the 3D-printing approach allows implementing a versatile fullypopulated air-coupled 2D-phased array transducer with superior performance. We are using commercially available transducers with a diameter of 10mm on the vibrating aperture side. Focal laws and beam steering true time delays are calculated by a custom FPGA board, extended with ultrasound pulsers. The array features beam steering in two directions over an opening angle of 110° with outstanding sound pressure levels (SPL) exceeding 145 dB SPL and 136 dB SPL at a distance of 0.3m and 1 m, respectively. The main lobe is symmetric and has a full angle of about 14° (− 3 dB). Our results prove that the approach of using the 3D-printed waveguide structure has the potential to be useful for numerous ultrasonic air-coupled applications.