Remote sensing of heart rate using millimeter-wave interferometry and probabilistic interpolation

Ilya V. Mikhelson, Sasan Bakhtiari, Thomas W. Elmer, Shaolin Liao, Alan V. Sahakian*

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Using a 94-GHz homodyne interferometer employing a highly-directional quasi-optical lens antenna aimed at a human subject's chest, we can measure chest wall displacement from up to 10m away and through common clothing. Within the chest displacement signal are motions due to cardiac activity, respiration, and gross body movement. Our goal is to find the heart rate of the subject being monitored, which implies isolation of the minute movements due to cardiac activity from the much larger movements due to respiration and body movement. To accomplish this, we first find a subset of the true heartbeat temporal locations (called "confident" heartbeats) in the displacement signal using a multi-resolution wavelet approach, utilizing Symlet wavelets. Although the chest displacement due to cardiac activity is orders of magnitude smaller than that due to respiration and body movement, wavelets find those heartbeat locations due to several useful properties, such as shape matching, high-pass filtering, and vanishing moments. Using the assumption that the " confident" heartbeats are randomly selected from the set of all heartbeats, we are able to find the maximum a posteriori statistics of an inverse Gaussian probability distribution modeling the inter-heartbeat times. We then analyze the " confident" heartbeats and decide which heartbeats are probabilistically correct and which are not, based on the inverse Gaussian distribution we calculated earlier. The union of the " confident" set, after pruning, and the interpolated set forms a very close approximation to the true heartbeat temporal location set, and thus allows us to accurately calculate a heart rate.

Original languageEnglish (US)
Title of host publicationSmart Biomedical and Physiological Sensor Technology X
StatePublished - Aug 8 2013
EventSmart Biomedical and Physiological Sensor Technology X - Baltimore, MD, United States
Duration: May 1 2013May 2 2013

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


OtherSmart Biomedical and Physiological Sensor Technology X
CountryUnited States
CityBaltimore, MD


  • Ambulatory monitoring
  • Heart rate
  • Heartbeat detection
  • Millimeter-wave
  • Remote sensing

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging

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