| Piezoelectric micromachined ultrasonic transducers(PMUTs)have developed rapidly in recent years and have been widely used in human imaging,wearable devices,and underwater acoustics.In this paper,the air-coupled PMUTs are studied,and three applications based on the time-of-flight are realized: air-coupled distance measurement,imaging and detecting,and indoor positioning.According to different application characteristics,the device is designed,fabricated,and characterized.The main work of this paper is as follows.First of all,this paper carries out the design of PMUT: The devices’ performance requirements of different applications are analyzed.For applications such as pulse-echo that require high axial emission sound pressure,the influence of the rectangular array parameters on its directivity is studied.An Archimedean spiral transducers array that can improve the axial sound pressure is proposed and characterized.Indoor localization requires a large receiving angle receiver,a low-frequency PMUT is designed and prepared for it.Secondly,this paper realizes the application of ranging,air-coupled imaging and detection.The impedance matching and the amplifier circuit design are carried out based on the analysis of the electrical characteristics for the PMUT array.Then the time-of-flight ranging with a range of 15 cm and error of 3‰ is completed.In addition,a duplexer circuit is designed for pulse-echo air-coupled imaging and detection,which can achieve a recognition rate of 96% for varied materials.Finally,ultrasonic indoor localization is realized in this paper.The model of the time difference of arrival localization is analyzed,and a solution method based on a quantum genetic algorithm is proposed.The working structure of the base station and the address code are designed,then the hardware design is completed.The final test results show that the indoor localization system based on PMUT can achieve centimeter-level positioning. |
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