Analysis of Model Parameters and Experimental Setup for Accurate Characterization of Ultrasound Phased Arrays Using a Low-Cost Sensor

Background: Ultrasound Phased Arrays (UPAs) are an emerging technology for contactless midair haptics and acoustic levitation, offering many advantages compared to other contactless methods. Accurate characterization of the airborne ultrasound field produced by UPAs is crucial for evaluating their performance. Objective: This paper introduces a novel UPA design and investigates the feasibility of using a low-cost commercial piezoelectric transducer, i.e., the Murata MA40S4R, for its characterization, in contrast to very expensive microphones commonly employed in literature for testing. Methods: The characterization is conducted both on the Murata MA40S4R transducer and on the proposed UPA, analyzing the experimental setup, the fitting of model parameters, the effect of wave reflection, duty-cycle dependency, and different directivity patterns on system performance. The architecture of the proposed UPA, the measurement chain, and the measurement protocol are described to ensure an accurate characterization procedure, and the influence of model parameters and experimental setup on the accuracy of measured data is investigated. Results: The performed tests show that experimental measurements closely match predicted data after optimizing the model parameters and setup, achieving a root-mean-square relative pressure error of 4.1% in the focal region. Conclusion: This research highlights the possibility of obtaining accurate ultrasound field measurements with a very low-cost sensor, paving the way for accessible UPAs characterization and development.