Non-linear ultrasonic harmonic generation in air for the wideband testing of porous membranes using narrowband and low frequency transmitters presented at IEEE-IUS 2023 in Montreal, Canada. Work carried out within the Liste2Future EU funded project

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This work pretend to extend both the bandwidth and the generation of frequencies over 100 kHz by using MEM transducers and nonliner armonic generation in the air, to make possible the extension of the usability of present air-coupled PMUTs to frequencies over 100 kHz, which is critical for the use of this technology in materials characterization and NDT.

The characterization and test of porous and microporous thin layers using air-coupled ultrasound is
extremely attractive for quality control in different industries, including air-filtration, Li-ion batteries, venting materials, etc. This work explores the possibility of using low frequency and narrowband transducers to generate harmonics in the air and use them to characterize this type of materials. This can help to avoid transducers limitations in terms of both center frequency and frequency bandwidth. The proposed set up consist of low frequency and narrowband excitation, harmonic generation in
the air and the use of a wide band receiver. The setup configuration requirements are analyzed and described in detailed in this study. A comparison of the proposed technique results with linear conventional wideband air-coupled measurements demonstrates the potential of the presented
method as a less demanding alternative in terms of equipment needs and time required. This can be of special interest for the deployment of solutions based on MEMs transducers, mainly PMUTs, that show some limitations in the maximum frequency and bandwidth when operating in air.

Authors acknowledge fellowship JCI (JC2020-043487-I) funded by MCIN/AEI/10.13039/501100011033 and by “European Union NextGenerationEU/PRTR”. Funding by project Listen2Future is acknowledged. Under grant 101096884, Listen2Future is co-funded by the European Union.