AlN薄膜PMUT阵列指向性仿真分析与阵列优化

Simulation analysis of directivity and optimization of the array of the AlN thin film PMUT array

由于氮化铝压电薄膜相对较低的压电常数限制了氮化铝基微机械超声换能器的发展和应用,因此针对该问题研究了氮化铝基微机械超声换能器阵列的指向性。首先依据瑞利原理计算了换能器阵的远场声压以及归一化指向性函数;进而仿真分析了阵元半径、阵元间距、阵元数量以及工作频率等因素对阵列波束宽度、方向锐度角和旁瓣级的影响,并对换能器阵进行了优化;最后根据优化结果、面积和填充效率等因素进行综合考虑,确定了换能器阵的最终结构尺寸,并对其声压分布进行了可视化仿真。仿真结果表明,优化后换能器阵具有较为理想的声压分布,指向性良好,主瓣尖锐,主瓣的-3 dB波束宽度为9°左右,旁瓣级为0.228左右。

The relatively low piezoelectric constant of the aluminum nitride piezoelectric film limits the development and application of the piezoelectric micro-machined ultrasonic transducer based on the aluminum nitride.Therefore,the directivity of the piezoelectric micro-machined ultrasonic transducer array is studied for this problem.First,the far-field sound pressure and normalized directivity function of the transducer array are calculated according to the Rayleigh principle.Furthermore,the effects of array element radius,array element spacing,array element number and operating frequency on the beam width,direction sharpness angle and sidelobe level of the array are analyzed,and the transducer array is optimized.Finally,based on the optimization results,area and filling efficiency,the final structure size of the transducer array is determined and the sound pressure distribution visually simulated.The results show that the optimized transducer array has an ideal sound pressure distribution,good directivity and sharp main lobe.The-3 dB beamwidth of the main lobe is about 9°and the sidelobe level is about 0.228.