Attenuation of Curved Structural Surfaces in PMUT Measurements

This work presents the attenuation effect due to the surface curvature for the ultrasound pulse-echo detection scheme. The magnitude of attenuation due to the curved surface is simulated and experimentally validated by a piezoelectric micromachined transducer (pMUT) array as a model with 39 × 39 elements and 3 mm × 3mm in size made of 1 µm-thick A1N piezoelectric layer, and 5 urn-thick Si elastic layer. Experimental validations have been conducted to measure the diameter variations of silicone tubes with different diameters in the mineral oil environment to mimic the acoustic properties of the human tissue and blood vessel. Under an applied voltage of 12 V, three sine cycles of 1–10 MHz frequency are emitted and the echo signals from tubes with diameters 2 to 12 mm at a distance of 25 mm are captured. The measured and simulated attenuation is around 7dB for those surfaces to emulate arteries and veins for applications in blood pressure measurements. These results help both the design and analysis of ultrasound detections by pMUTs encountering non-flat surfaces both qualitatively and quantitatively for various applications.