Liu Jian-Hung, Chen Sheng-Yung, Li Pai-Chi
Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan.
IEEE Trans Ultrason Ferroelectr Freq Control. 2009 Feb;56(2):379-86. doi: 10.1109/TUFFC.2009.1047.
The design, fabrication, and evaluation of a high-frequency single-element transducer are described. The transducer has an annular geometry, with the thickness of the piezoelectric material increasing from the center to the outside. This single-element annular transducer (SEAT) can provide a broader frequency range than a conventional single-element transducer with a uniform thickness (single-element uniform transducer, or SEUT). We compared the characteristics of a SEAT and a SEUT. Both transducers used 36 degrees-rotated, Y-cut lithium niobate (LiNbO(3)) material. The SEAT had a diameter of 6 mm and comprised 6 subelements of equal area (electrically connected by a single electrode on each side) whose thickness ranged from 60 microm (center) to 110 microm (outside), which resulted in the center frequency of the subelements varying from 59.8 MHz to 25 MHz. The overall center frequency was 42.4 MHz. The annular pattern was constructed using an ultrasonic sculpturing machine that reduced the root-mean-square value of the surface roughness to 454.47 nm. The bandwidth of the SEAT was 19% larger than that of the SEUT. However, compared with the SEUT, the 2-way insertion loss of the SEAT was increased by 3.1 dB. The acoustic beam pattern of the SEAT was also evaluated numerically by finite-element simulations and experimentally by an ultrasound beam analyzer. At the focus (10.5 mm from the transducer surface), the -6 dB beam width was 108 microm. There was reasonable agreement between the data from simulations and experiments. The SEAT can be used for imaging applications that require a wider transducer bandwidth, such as harmonic imaging, and can be manufactured using the same techniques used to produce transducers with multiple frequency bands.
描述了一种高频单元素换能器的设计、制造和评估。该换能器具有环形几何形状，压电材料的厚度从中心到外部逐渐增加。这种单元素环形换能器（SEAT）能够提供比具有均匀厚度的传统单元素换能器（单元素均匀换能器，或SEUT）更宽的频率范围。我们比较了SEAT和SEUT的特性。两种换能器均使用36度旋转的Y切铌酸锂（LiNbO₃）材料。SEAT的直径为6毫米，由6个等面积的子元件组成（每侧通过单个电极电连接），其厚度范围从60微米（中心）到110微米（外部），这导致子元件的中心频率从59.8兆赫兹变化到25兆赫兹。整体中心频率为42.4兆赫兹。使用超声雕刻机构建环形图案，将表面粗糙度的均方根值降低到454.47纳米。SEAT的带宽比SEUT大19%。然而，与SEUT相比，SEAT的双向插入损耗增加了3.1分贝。还通过有限元模拟对SEAT的声束图案进行了数值评估，并通过超声束分析仪进行了实验评估。在焦点处（距换能器表面10.5毫米），-6分贝波束宽度为108微米。模拟数据和实验数据之间存在合理的一致性。SEAT可用于需要更宽换能器带宽的成像应用，如谐波成像，并且可以使用与生产具有多个频段的换能器相同的技术制造。
