All-Digital Dynamic Focusing Transmit Beamformer for High-Frequency Ultrasonic Imaging System Applications

• Main Authors: FU, YA-YU, 傅雅鈺
• Other Authors: SHENG, DUO
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/d4af5q

碩士 === 輔仁大學 === 電機工程學系碩士班 === 106 === General traditional high-frequency beamformers are mostly implemented by FPGA, but the delay resolution of FPGA is not enough to meet the high-frequency ultrasonic system, and it is not suitable to be integrated into a portable ultrasonic system. Therefore, this study uses an integrated circuit to implement a transmitter beamformer. The main structure of this circuit is divided into all-digital delay locked Loop, beamforming delay line control code generator, and beamforming delay line based on a flip-flop. All-digital delay-locked loop locks different delay times based on different depths of focus, generating digital control code delay cell. In order to avoid the use of multiple all-digital delay-locked loops to achieve the function of dynamic focusing, a method of digital dynamic focusing is proposed. A register is used to store the digital control code required for each depth. Finally, the digital control code which is received from beamforming delay line is determined by the multiplexer. This can reduce circuit complexity and area to achieve better imaging quality. We use the TSMC 0.18µm technology to realizing the D-Flip Flop Based Beamforming, and the whole chip area is 1193µm × 1020µm. In the typical case, the range of delay cell is 864.28ps to 1920.6ps, and the resolution is 1.88ps. In ultrasonic system, the delay time required for ultrasonic depth of focus is simulated by MATLAB and Field II simulation. Considering the limitation of delaying the cell element essence in best case, typical case, and worst case environment, the depth of focus of 5mm, 6.25mm and 7.5mm was simulated, and the lateral resolution are0.03899mm, 0.04191mm and 0.0495mm respectively.