Ultrasonic High Frequency Kerfless Linear Array
Date Issued
2007
Date
2007
Author(s)
Wang, Weng-Tao
DOI
zh-TW
Abstract
Linear arrays have been widely used in medical ultrasonic imaging systems due to the abilities of dynamic focusing and electronic scanning. In order to improve image resolution, high frequency (≧20 MHz) array transducers have also been fabricated. One of the most critical problems when fabricating a high frequency array is the limitation of current dicing technologies. To avoid grating lobes, the interelement spacing needs to be less than half a wavelength. At higher frequencies, the spacing is small and this in turns limits the kerf width between two adjacent channels. Additionally, thickness of the piezoelectric material is also proportional to wavelength. At high frequencies, the piezoelectrical material becomes fragile particularly during dicing. In order to alleviate these problems, a kerfless linear array is proposed in this research. Because the piezoelectric material remains one piece, cross talk becomes significant and this lowers the image quality. To alleviate the cross talk problem, a signal processing method is also investigated.
Both PZFlex and Field II simulations are performed. A 20 MHz kerfless linear array is also fabricated. LiNbO3 is used as the piezoelectric material with a thickness of 184μm after lapping. The pitch is 75μm, within which 65μm is the electrode width and 10μm is the spacing between electrodes. The elevational focus is 9mm. We use flexible printed circuit board for circuit connection. Experimental data shows that 20 MHz ultrasonic signal can be generated successfully. The pulse echo signal has a peak-to-peak voltage of 0.7 V with a 20 dB pre-amp. We also use a hydrophone to measure the cross-talk level of adjacent elements. The average cross-talk level within 3 consecutive elements is about -3 dB.
Subjects
單一探頭
陣列探頭
壓電材料
無切割
cross-talk
鈮酸鋰
single crystal
array transducer
high frequency array
piezoelectric material
kerfless
LiNbO3
Type
thesis
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