Pandey Rajeev Kumar, Chao Paul C-P
EECS International Graduate Program, National Chiao Tung University, Hsinchu, 300 Taiwan.
Department of Electrical Engineering, National Chiao Tung University, Hsinchu, 300 Taiwan.
Microsyst Technol. 2021;27(6):2315-2343. doi: 10.1007/s00542-020-05106-y. Epub 2020 Nov 27.
This study presents an external temperature sensor assisted a new low power, time-interleave, wide dynamic range, and low DC drift photoplethysmography (PPG) signal acquisition system to obtain the accurate measurement of various bio signs in real-time. The designed chip incorporates a 2-bit control programmable transimpedance amplifier (TIA), a high order filter, a 3:8 programmable gain amplifier (PGA) and 2 × 2 organic light-emitting diode (OLED) driver. Temperature sensor is used herein to compensate the adverse effect of low-skin-temperature on the PPG signal quality. The analog front-end circuit is implemented in the integrated chip with chip area of 2008 μm × 1377 μm and fabricated via TSMC T18 process. With the standard 1.8 V, the experimental result shows that the measured current sensing range is 20 nA-100 uA. The measured dynamic range of the designed readout circuit is 80 dB. The estimated signal to noise ratio is 60 dB@1 uA, and the measured input referred noise is 60.2 pA/Hz. The total power consumption of the designed chip is 31.32 µW (readout) + 1.62 mW (OLED driver@100% duty cycle). The non-invasive PPG sensor is applied to the wrist artery of the 40 healthy subjects for sensing the pulsation of the blood vessel. The experimental results show that for every 1 °C decrease in mean ambient temperature tends to 0.06 beats/min, 0.125 mmHg and 0.063 mmHg increase in hear rate (HR), systolic (SBP) and diastolic (DBP), respectively. Similarly, for every 1 °C increase in mean ambient temperature tends to 0.13 beats/min, 0.601 mmHg and 0.121 mmHg increase in HR, SBP and DBP, respectively. The measured accuracy and standard error for the HR estimation are 96%, and - 0.022 ± 2.589 beats/minute, respectively. The oxygen stauration (SO) measurement results shows that the mean absolute percentage error is less than 5%. The resultant errors for the SBP and DBP measurement are - 0.318 ± 5.19 mmHg and - 0.5 ± 1.91 mmHg, respectively.
本研究提出了一种由外部温度传感器辅助的新型低功耗、时间交错、宽动态范围且低直流漂移的光电容积脉搏波描记法（PPG）信号采集系统，以实时准确测量各种生命体征。所设计的芯片集成了一个2位控制可编程跨阻放大器（TIA）、一个高阶滤波器、一个3:8可编程增益放大器（PGA）和一个2×2有机发光二极管（OLED）驱动器。本文使用温度传感器来补偿低皮肤温度对PPG信号质量的不利影响。模拟前端电路在芯片面积为2008μm×1377μm的集成芯片中实现，并通过台积电T18工艺制造。在标准1.8V电压下，实验结果表明测量的电流传感范围为20nA至100μA。所设计读出电路的测量动态范围为80dB。估计的信噪比在1μA时为60dB，测量的输入参考噪声为60.2pA/Hz。所设计芯片的总功耗为31.32μW（读出）+1.62mW（OLED驱动器，占空比100%）。该无创PPG传感器应用于40名健康受试者的腕动脉，以感测血管的搏动。实验结果表明，平均环境温度每降低1°C，心率（HR）、收缩压（SBP）和舒张压（DBP）分别倾向于增加0.06次/分钟、0.125mmHg和0.063mmHg。同样，平均环境温度每升高1°C，HR、SBP和DBP分别倾向于增加0.13次/分钟、0.601mmHg和0.121mmHg。HR估计的测量精度和标准误差分别为96%和-0.022±2.589次/分钟。血氧饱和度（SO）测量结果表明平均绝对百分比误差小于5%。SBP和DBP测量的最终误差分别为-0.318±5.19mmHg和-0.5±1.91mmHg。
