(A) low power bio impedance measurement system

Abstract

Cardiovascular disease (CVD) is one of the main causes of the death in the world. Heart rate (HR) and pulse wave velocity (PWV) is widely used to diagnosis the CVD. The bio impedance (BI) measurement method can be an option to measure these bio signals. By measuring the BI of the blood vessel, the HR and the PWV can be measured on a small IC chip. Before the chip design, some BI experiments are carried out to find out the characteristics of the BI. The miniaturized PCB board (H/W) is designed to measure the BI on the wrist. The labview (S/W) is used to calculate the PWV from the measured BI and ECG. Based on this BI experiment, the H/W system can be integrated on a small chip. To realize the traditional BI measurement system, IA, MIXER, BPF, VGA and ADC are integrated on the chip. For the MIXER, the S/H down conversion technique is proposed to eliminate the use of the LPF. For the BPF, the switched capacitor technique is used to realize the large RC constant in the small IC chip. Finally, for the VGA, the offset cancellation technique is proposed by combining the traditional backward and forward cancellation techniques. The total BI measurement system is implemented by using dongbu 0.13um CMOS process. This traditional amplitude-modulated BI measurement has some problems. To solve these problems, the novel phase-modulated BI measurement method is proposed. The proposed architecture concentrates on the phase modulation of the measured voltage difference. To measure the quantity of the phase modulation, it consists of IA, limiter, time domain HPF and TDC. The IA is same as the one in the traditional BI measurement method. The time domain HPF uses the phase locked loop (PLL) structure, which consists of the PD, the CP and VCDL. Finally, the GRO TDC is designed to convert the time interval to the digital output. The proposed system is implemented by using dongbu 0.13um CMOS process. The measurement result shows the functionalities of the designed blocks are verifie...