基于MEMS技术可植入微压力传感器的检测电路设计

摘要

To monitor the pressure in vivo,an implantable,wireless blood and intracranial pressure sensor is presented based on micro electro mechanical system(MEMS)technology and a solution to reading signal.Since this pressure sensor is a capacitive pressure sensor,the capacitance signal of the sensor is converted into a voltage signal through the integrated circuit CAV414.According to theoretical calculations,the value of pressure sensor capacitance is about 15 pF.The IC is optimized for capacities within the wide range from 10 pF to 2 nF with possible changes from 5％ to 100％ of reference capacity.Therefore,the minimum value of detectable capacitance change is 0.75 pF.The output voltage range of 0-5 V can be used as the input signal source for the integrated analog-to-digital converter(ADC).The chip ADC0809 is selected as the ADC.The ADC0809 is a monolithic CMOS device with an 8-channel multiplexer and an 8-bit analog-to-digital(A/D)converter.The 8-bit parallel digital output signal from the ADC0809 can be directly applied to subsequent digital signal processing,which is implemented based on the field programmable gate array(FPGA).%为实现体内压力(如:血压、颅内压等)的实时监测,采用微机电系统(MEMS)技术制造出植入式微压力传感器.由于它是电容式传感器,在信号读取系统中,首先通过集成电路CAV414将电容信号转换为电压信号.通过理论计算和实际试验测试,微压力传感器初始电容值为15 pF.CAV414检测范围是10 pF～2 nF,检测精度为电容初始值的5％,因此在该系统中可检测到的电容最小变化量为0.75 pF,其输出电压范围为0～5 V,该电压信号可以直接作为模拟/数字转换器(ADC)的输入信号.选用ADC0809实现模拟信号向数字信号的转换.ADC0809为一款8通道8位模数转换器,通过FPGA实现对ADC0809的驱动控制.ADC0809的8位输出信号直接作为数字信号的输入,在本文试验中数字信号处理通过FPGA编程实现.