Design Of Multi Channel Data Acquisition System For Ultrasonic Detector

Ultrasound diagnosis is an important medical diagnostic technology because of its painless, noninvasive, convenient operation, intuitive display, low cost. It is widely used in the field of medical diagnosis. For ultrasonic diagnosis technology, high ultrasonic frequency leads to higher spatial resolution and better structure. However, the traditional ultrasonic detectors, which are low ultrasonic frequency, have a negative effect on spatial resolution and the image precision. It restricts the development of ultrasound diagnosis. Hence the research of high resolution ultrasound detector becomes very heated in recent years.PVDF piezoelectric films have a piezoelectric effect. When receiving the ultrasonic signal, PVDF piezoelectric films will generate induced charge. Our lab designs a silicon pixel sensor chip named Topmetal. It has the advantages of small size, high position resolution, fast response. It can be used to collect charge and generate an analog electrical signal output. In this way, the application of this chip and PVDF piezoelectric film will do well in high resolution ultrasound detectors, which fully meets people’s requirement.The focus of this thesis is to design a multi-channel DAQ for ultrasonic detector. It uses 8-channel,12bit high speed ADC to sample the analog outputs of pixel sensor. The sampling rate is 25MSPS. The sampling data is transferred to FPGA by LVDS signals. After differential conversion, delay adjustment, serial to parallel conversion and FIFO cache, it is written into SDRAM. The data will be then sent to PC through the PCIe bus. Control commands are transmitted to FPGA through PCIe bus.In this thesis, the main research work includes four parts:Hardware design:It includes the hardware design of Topmetal bonding board, Topmetal driving board and ADC sampling board. Topmetal bonding board connects the chip pad with the PCB board. Driving board provides chip control signals and external reset signals. It also drives the analog outputs. ADC sampling board is used to sample the analog outputs of Topmetal.Logic design:It includes many logic modules, such as clock management module, ADC register configuration module, differential conversion module, delay control module, serial to parallel conversion module, data cache module and QSYS system.Software design:It uses the user interface function of PCIe driver in Linux operation system to realize four functions:ADC register setting, data delay setting, delay analysis and transmission error analysis.System test:It includes hardware test and ultrasonic test. The result shows that the data acquisition system can work stably at the sampling rate of 25MSPS.