Investigation of phased array antenna systems for non-contact vital signs sensing
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The continuous and accurate monitoring of human vital signs is an extremely important part of the healthcare industry, as it is the basic means by which healthcare professionals monitor the instantaneous status of their patients. The ability to capture, record, and analyze vital signs information quickly can make a life-and-death difference in the ability for doctors and other healthcare professionals to make quick and informed decisions about patients’ conditions for treatments. Additionally, it has become increasingly desirable to use less invasive means by which to measure the vital signs data. This has led to much increased research spending in non-contact technologies which can monitor and transmit vital signs information quickly to the appropriate healthcare professionals. Additionally, since innovations in biomedical applications have been one of the biggest areas of research and development spending in the world, we will explore the benefits of using specialized antennas for increased performance and practicality of the non-contact vital signs (NCVS) biosensor that we have built in Professor Donald Lie’s RF/Analog SoC Labs. The purpose of this thesis is to explore the uses of high directivity antennas and electronically steerable phased array antenna systems to improve the performance and functionality of modern non-contact vital signs measurement systems. The primary focus of the applications of these specialized antennas in this work will be with the Doppler-based NCVS monitoring biosensor systems. It has been observed that that the accuracy of the NCVS sensor systems described in this and previous works can be diminished by reflections from background clutter in the measurement environment. One specific approach used to try and alleviate this issue is to employ the use of more directive antennas and phased arrays to steer the radiation beam towards a subject if they are not able to be properly illuminated by a typical commercial-off-the-shelf (COTS) antenna. The process and issues involved in designing customizable helical antennas that can be used in phased arrays or individually within the NCVS biosensor system will be described. In this thesis, the performance and accuracy of the NCVS biosensor is determined by the statistical analysis of a vast amount of data it collected and compared with the heart rate data measured from a physical and independent finger pulse sensor as the reference. We will explore how the different antenna and antenna systems affect the performance of the NCVS biosensor in this work. We believe this work is the 1st systematic study on using phased array systems for NCVS sensing performed in a clutter-free anechoic chamber, and it has shed some new and exciting lights on improving the existing NCVS sensor systems as brand new data has been collected and understood, which is especially important for enabling reliable, continuous and ubiquitous heart rate monitoring in the future.