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UID:20260523T215144EDT-4962MU8iSZ@132.216.98.100
DTSTAMP:20260524T015144Z
DESCRIPTION:Abstract\n\nIn recent years\, photoplethysmography (PPG) is con
 sidered extensively because it is a low-cost electro-optical technique for
  measuring the volumetric variations of blood and contains valuable health
  information such as heart rate (HR)\, respiration rate (RR)\, blood press
 ure (BP)\, and blood oxygen saturation (SpO2). However\, PPG sensing in we
 arable devices remains constrained by two primary challenges for long-term
  deployment: (1) the high-power consumption of the light-emitting diodes (
 LEDs) and (2) the requirement for high dynamic range in signal acquisition
 . In order to enable energy-efficient\, wearable\, and long-lasting health
  monitoring devices this work addresses these challenges by proposing two 
 innovations: (1) a No-LED (ambient light) mode for PPG signal acquisition 
 to significantly reduce power consumption\, and (2) a current-mode analog-
 front end (AFE) architecture designed to achieve ultra-low-power operation
  while maintaining high dynamic range performance.\n\nIn the first part of
  the work a flexible wireless finger patch capable of recording PPG signal
 s under diverse ambient lighting conditions (No-LED) is researched. Experi
 mental evaluation on 12 subjects demonstrated that under sufficient ambien
 t light such as sunlight\, room light\, the acquired PPG signals can be pl
 aced in the reliable or acceptable category and can measure HR and BP with
  good accuracy. The calculated maximum mean absolute error (MAE) for HR in
  comparison to the reference measurement is small (3.4 BPM). For BP predic
 tion an average MAE of 8.1 mmHg and 6.05 mmHg for systolic BP (SBP) and di
 astolic BP (DBP)\, respectively are obtained.\n\nAs a user can be without 
 enough ambient light for a significant portion of the day\, it is importan
 t to have PPG sensor-based wearables that work in both No-LED and LED-ON m
 ode light. Moreover\, the reported finger patch cannot measure SpO2\, whic
 h is an important health parameter. To overcome these limitations\, in the
  second part of the work a ring–bracelet flexible wearable device is explo
 red. The wearable integrates an optimized photodiode–LED configuration to 
 work in both No-LED (when there is enough ambient light) and low intensity
  LED modes (when there is not enough ambient light) and an accelerometer f
 or motion artifact reduction. It also utlizes optical filters for SpO2 mea
 surement. This system achieved a maximum measurement error of 3 bpm for HR
  and 2.9% for SpO₂\, while continuously consuming only 262.5 μW in No-LED 
 mode and 652.5 μW in low-LED mode).\n\nWhile the wearable devices explored
  in first and second part demonstrate the feasibility of No-LED operation\
 , their readout circuits were not optimized for weak PPG signals under amb
 ient light or low-LED illumination. To address this limitation\, a novel c
 urrent-based readout architecture (I-readout) is developed. The designed P
 PG signal readout works entirely in the current domain\, eliminating the n
 eed for high-performance closed-loop amplifiers and enabling integration w
 ith other current/voltage-output sensors. The architecture achieves an 86 
 dB dynamic range while consuming only 70 μW in the AFE. Total system power
  remains as low as 150 μW with the low-LED active and 70 μW in No-LED mode
 \, representing the first application of current-mode signal by minimizing
  or eliminating active LED usage and leveraging efficient current-domain s
 ignal processing\, this work collectively lays the foundation for a new ge
 neration of ultra-low-power\, scalable\, and sustainable wearable health m
 onitoring technologies by PPG sensing.\n
DTSTART:20260323T170000Z
DTEND:20260323T190000Z
LOCATION:Room 603\, McConnell Engineering Building\, CA\, QC\, Montreal\, H
 3A 0E9\, 3480 rue University
SUMMARY:PhD defence of Shahab Mahmoudi Sadaghiani – Reducing Power Consumpt
 ion of Photoplethysmography (PPG) based Wearables with No-LED mode and Cur
 rent-to-Digital Converter (CDC) Readout
URL:/ece/channels/event/phd-defence-shahab-mahmoudi-sa
 daghiani-reducing-power-consumption-photoplethysmography-ppg-based-371991
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