A Baseline-Tracking Single-Channel I/Q Impedance Plethysmogram IC for Neckband-Based Blood Pressure and Cardiovascular Monitoring

An impedance plethysmogram (IPG) IC with wide-range fine baseline tracking capability is proposed to provide continuous blood pressure (BP) and cardiovascular monitoring just by wearing a neckband wearable device. For the baseline tracking, a mixed-mode baseline cancellation (MM-BC) scheme is proposed to achieve wide dynamic range (DR) and high SNR performance, where an artifact-detecting continuous-time (CT)-
$\Delta \Sigma $
ADC is included together for high-resolution conversion. For cost-effective IPG design, a phase synchronizer concept is introduced to provide I/Q detection capability with single readout channel, supporting both configurations of two-electrode and four-electrode. A proposed readout integrated circuit (ROIC) prototype for the proposed IPG was fabricated, where an electrocardiogram (ECG) readout path is integrated together. The proposed IPG schemes were experimentally verified to achieve good performances of 145.2-dB DR and 103.5-dB SNR. For system-level feasibility, a neckband device prototype was also manufactured, and its cardiovascular monitoring functionality was functionally verified. Based on its IPG and ECG measurements, continuous BP measurement based on the pulse arrival time (PAT) was experimentally verified with a reference BP device.