CMUT及其阵列工作机理与应用基础研究

发布时间：2018-01-13 03:02

本文关键词：CMUT及其阵列工作机理与应用基础研究　出处：《天津大学》2016年博士论文　论文类型：学位论文

【摘要】：超声成像技术广泛应用于医学、军事、工业、农业等众多领域,而超声传感器是实现超声成像的关键部件之一。基于MEMS技术的电容式微机械超声传感器(Capacitive Micromachined Ultrasonic Transducer,CMUT)具有传统压电超声传感器所不具备的显著优势,有望替代传统压电超声传感器成为市场的主流产品。针对电容式微机械超声传感器开展相关理论与应用基础研究,具有十分重要的研究价值和现实意义。本文的主要内容如下:首先,在加工制造之前对CMUT进行特性分析可以为优化设计参数提供依据。在详细阐述CMUT工作原理和相关理论的基础上,研究了CMUT的建模理论。建立了CMUT微元的小信号等效电路模型和有限元模型,利用有限元模型进行了静态分析、模态分析和谐响应分析。为了能够快速、有效地对CMUT微元和CMUT进行特性分析,推导并建立了一种状态方程-SIMULINK模型,并对CMUT微元和CMUT进行了发射与接收特性分析,为后续实际应用和测试提供了重要的理论依据和参考。其次,CMUT与CMUT阵列的指向性是其在远场的重要特性之一。通过详细分析设计参数对其指向性的影响,结合CMUT和CMUT阵列的特点,提出了合理选择CMUT阵列设计参数的准则。针对所设计的CMUT及其阵列,推导出了三种不同的CMUT指向性函数和四种不同的CMUT阵列指向性函数,并进行了对比分析。针对指向性图中出现的旁瓣现象,研究了多种旁瓣抑制方法,有效地降低了旁瓣辐值。再次,超声传感器的声场分布特性直接影响着其成像质量。在论述相关声场理论的基础上,研究了基于瑞利-索末菲积分公式、角谱方法和空间冲激响应的声场分析方法,并针对CMUT和CMUT阵列的特点,研究了相应的声场分析方法。通过计算辐射声场,分析了CMUT阵列的聚焦与偏转性能,研究了阵列孔径尺寸对聚焦距离的影响,并分析了CMUT阵列设计参数对其空间脉冲回波响应的影响。然后,不同的成像方法具有不同的性能和特点,实际应用中需要综合考虑多种因素选择合适的方法。在论述相控阵成像、合成孔径聚焦成像和相控子阵成像三种不同成像方法工作原理的基础上,通过计算相应的有效孔径和合成波束,对其进行了对比分析,并基于CMUT线阵,验证分析了三种成像方法的成像效果。对于阵元数目较多的CMUT面阵,设计了几种特殊的相控子阵成像方案,可以有效地降低成像系统的复杂性,并提高成像的实时性。最后,通过对CMUT线阵进行全面的测试与分析,进一步验证了所设计CMUT及其阵列的性能,为今后设计超声成像系统提供了重要的数据参考。
[Abstract]:Ultrasonic imaging technology is widely used in many fields such as medicine, military, industry, agriculture and so on. The ultrasonic sensor is one of the key components of ultrasonic imaging. Capacitive Micro Mechanical Ultrasonic Sensor based on MEMS (. Capacitive Micromachined Ultrasonic Transducer. CMUTs have significant advantages that traditional piezoelectric ultrasonic sensors do not have. It is expected to replace the traditional piezoelectric ultrasonic sensor to become the mainstream product in the market. The basic research on the theory and application of capacitive micro-mechanical ultrasonic sensor is carried out. It has very important research value and practical significance. The main contents of this paper are as follows: first of all. The characteristic analysis of CMUT before machining and manufacturing can provide the basis for optimizing design parameters. On the basis of elaborating the working principle and related theories of CMUT in detail. The modeling theory of CMUT is studied. The small signal equivalent circuit model and finite element model of CMUT microelement are established, and the static analysis is carried out by using the finite element model. Modal analysis and harmonic response analysis. In order to analyze the characteristics of CMUT differentials and CMUT quickly and effectively, a state equation (SIMULINK) model is derived and established. The transmission and reception characteristics of CMUT microelements and CMUT are analyzed, which provides an important theoretical basis and reference for the subsequent practical application and testing. Secondly. The directivity of CMUT and CMUT arrays is one of their important characteristics in the far field. Through the detailed analysis of the influence of design parameters on their directivity, the characteristics of CMUT and CMUT arrays are combined. The criteria for reasonably selecting the design parameters of CMUT arrays are presented. The designed CMUT and its arrays are considered. Three different CMUT directivity functions and four different CMUT array directivity functions are derived and compared. Several sidelobe suppression methods are studied, which can effectively reduce the sidelobe radiations. Thirdly, the acoustic field distribution characteristics of ultrasonic sensors have a direct impact on the imaging quality. The acoustic field analysis method based on Rayleigh-Sommerfeld integral formula, angular spectrum method and spatial impulse response is studied, and the characteristics of CMUT and CMUT arrays are discussed. The focusing and deflection performance of CMUT array is analyzed by calculating the radiation sound field, and the effect of array aperture size on the focusing distance is studied. The influence of CMUT array design parameters on the spatial pulse echo response is analyzed. Then, different imaging methods have different performance and characteristics. It is necessary to consider a variety of factors to select suitable methods in practical application. On the basis of discussing three different imaging methods: phased array imaging, synthetic aperture focusing imaging and phase control subarray imaging, the working principles of these three imaging methods are discussed. By calculating the corresponding effective aperture and synthetic beam, we compare and analyze them. Based on the CMUT linear array, we verify and analyze the imaging effect of three imaging methods. For the CMUT array with a large number of elements. Several special phased array imaging schemes are designed, which can effectively reduce the complexity of the imaging system and improve the real-time imaging. Finally, through the overall test and analysis of CMUT linear array. The performance of the designed CMUT and its array is further verified, which provides an important data reference for the design of ultrasonic imaging system in the future.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP212

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