Takhyung Lee

Motion artifact reduction in electrocardiogram using adaptive filtering based on half cell potential monitoring

The electrocardiogram (ECG) is the main measurement parameter for effectively diagnosing chronic disease and guiding cardio-fitness therapy. ECGs contaminated by noise or artifacts disrupt the normal functioning of the automatic analysis algorithm. The objective of this study is to evaluate a method of measuring the HCP variation in motion artifacts through direct monitoring. The proposed wearable sensing device has two channels. One channel is used to measure the ECG through a differential amplifier. The other is for monitoring motion artifacts using the modified electrode and the same differential amplifier. Noise reduction was performed using adaptive filtering, based on a reference signal highly correlated with it. Direct measurement of HCP variations can eliminate the need for additional sensors.

Ultralow-Power Bioimpedance IC With Intermediate Frequency Shifting Chopper

A bioelectrical impedance IC with an intermediate frequency shifting chopper (IFSC) technique driven by a merged clock is presented. The proposed technique enables high-frequency impedance measurements with a narrow bandwidth low-power instrumentation amplifier (IA). The conventional series-connected double choppers required for the frequency shifting operation are replaced with a single chopper driven by a XNOR-merged clock. The proposed IC can measure bioelectrical impedance at a maximum excitation frequency of 1.24 MHz in an IA bandwidth of only 30 kHz. A DC trimming technique that uses a dummy impedance and anti-phase current source can adjust the output offset and prevent output saturation. This DC trimming technique also enables shifting of the impedance measurement scope. The proposed IC is fabricated using 0.13-μm CMOS process, and is shown to achieve a dynamic range of 97.1 dB, and 52 μW of power consumption.

Ambient light cancellation in photoplethysmogram application using alternating sampling and charge redistribution technique.

To overcome a large DC offset, ambient light interference, and optical path variation, a robust PPG readout chip is fabricated using 0.13-μm CMOS process. Against the large DC offset, a saturation detection and current feedback method can compensate a current of up to 30 μA. To be robust against optical path variation, an automatic emitting light compensation method is adopted. To remove the ambient light interference, we propose an alternating sampling and charge redistribution technique, in which no additional power is consumed, and only three differential switches and one capacitor are required. The PPG readout channel consumes 26 μW and has a input referred current noise of 260 pArms.

An ultra-low power (ULP) bandage-type ECG sensor for efficient cardiac disease management

This paper proposed an ultra-low power bandage-type ECG sensor (the size: 76×34×3 (mm3) and the power consumption: 1 mW) which allows for a continuous and real-time monitoring of a users ECG signals over 24h during daily activities.

Exercise amount calculation using a wearable half-cell potential sensor for mobile aerobic exercise management

The obesity has grown to concerning proportions in recent years, and it causes heart disease, type 2 diabetes, breast cancer, and colon cancer. To get healthy weight, commercial wearable devices with a accelerometer have been released to help users to quantitatively manage calories. However, an accelerometer has disadvantages: large power consumption and expensive price. We suggested a new method to measure the exercise amount using a HCP sensor. We performed an experiment to compare accuracies of exercise amount estimation using a HCP sensor with using an accelerometer with five subjects, and the accuracy of the HCP sensor was comparable to it of the accelerometer. Since a HCP sensor has lower power consumption and cheaper price than an accelerometer, wearable sensor can be smaller and cheaper than current commercial devices.