A compact acoustic waveguide for air-coupled ultrasonic phased arrays at 40 kHz
Matthias Rutsch, Gianni Allevato, Jan Hinrichs, Christoph Haugwitz, Regine Augenstein, Thomas Kaindl, Mario Kupnik · 2022 IEEE International Ultrasonics Symposium (IUS) · 2022
Acoustic waveguides offer the separation of the transducers aperture from the radiating aperture. In previous work, we used this design freedom to build air-coupled phased arrays with an inter element-spacing of half the wavelength. This approach can be used for grating lobe-free beamforming for numerous applications such as sonar and flow metering or even non-destructive testing. The previous waveguide, however, was complex with its 8×8 element design. In this work, we focus on 1D line arrays and reduce the overall complexity of the waveguide in three steps. First, Bézier-shapes are implemented into the waveguide, which provide printed circuit board (PCB) compatibility and reduce the assembly time of the transducers. Second, rectangular output ports increase the SPL by 7 dB compared to round ports. Third, the reduction of the waveguide length not only reduces fabrication time and cost but also reduces the blind zone of the ultrasonic sonar by 57%. All waveguide geometries were simulated using the boundary element method and validated in an anechoic chamber including a calibrated measurement microphone.