A Power Efficient Spectrophotometry & PPG Integrated Circuit for Mobile Medical Instruments

Numerous non-invasive spectrophotometry and photoplethysmography (PPG) based monitoring and imaging techniques have been developed in the past decades, including arterial oxygenation estimation with pulse oximetry, tissue perfusion assessment with near-infrared spectroscopy (NIRS), and thereon based brain activity imaging. Applications in medical- and neuroscience research as well as mobile diagnostics, long-term monitoring devices, and fitness trackers require a small form factor. The non-invasive and convenient optical interface to tissue is a major reason for the popularity of the aforementioned techniques, especially in the consumer market and in monitoring particularly vulnerable neonate patients. This however comes with considerable power consumption for tissue illumination which renders data acquisition current consumption relevant – if not dominant – in the system. This thesis presents a PPG analogue front-end designed for integration in a multi-biosensor system-on-chip. Compared to the state-of-the-art, a power saving of 68% has been achieved for equal signal quality and conditions. Further emphasis lies on low receiver noise, high maximum sampling rate, ambient light suppression, multi-channel capability, and area efficiency. In addition to the front-end circuit implementation, preliminary hardware prototypes for wearable and implantable medical instrumentation are presented, and the use of pulse wave velocity for blood pressure estimation is investigated as a potentially less-invasive alternative to catheter based pressure transducers in implantable telemetric systems for long-term experiments in laboratory animals. In such a device multiple vital signs, i.e., heart rate, blood pressure, respiratory rate, and arterial oxygenation could be covered by a single PPG probe.