A compact acoustic waveguide for air-coupled ultrasonic phased arrays at 40 kHz

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.