Waveguide Vital Sign Sensing Using Evanescent Field Phase Shift
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Solution Overview
Problem
Existing non-contact vital sign monitoring systems face challenges in distinguishing vital signs from background noise and interference due to reflections from body parts and surrounding objects, limiting their practical applicability, especially in ambient health monitoring.
Innovation Solution
A sensor using a waveguide configured to propagate a transmitted signal in a spoof surface plasmon mode to produce an evanescent electromagnetic field, allowing non-contact sensing of physiological parameters by detecting perturbations produced by body motions, which are then processed to determine physiological parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If Doppler radar techniques are used for non-contact vital sign monitoring, then mobility constraints are reduced and user comfort is improved, but background noise from reflections and interference makes it difficult to distinguish vital signs
Solution Approach 1:
The patent introduces an evanescent electromagnetic field as an intermediary between the sensor and the body. This field is generated by a waveguide structure that couples electromagnetic energy to the body without direct contact, enabling vital sign detection while avoiding the background noise problems of traditional Doppler radar. The evanescent field acts as a mediator that provides both the non-contact benefit and the measurement precision.
2Ease of operation
If radiative RF waves are used for remote sensing, then non-contact measurement is achieved, but background noise from reflections and interference increases
Solution Approach 1:
The patent changes the fundamental parameter of electromagnetic wave propagation from radiative to evanescent. By using a waveguide structure that supports surface waves, the system generates an evanescent field that decays exponentially with distance from the waveguide surface. This parameter change allows the field to penetrate the body for sensing while being confined enough to minimize background noise from distant reflections and interference.
3Measurement precision
If evanescent electromagnetic field is used for sensing, then sensing sensitivity is enhanced and background noise is minimized, but the waveguide must be placed at a predetermined distance from the body
Solution Approach 1:
The patent employs a broadband waveguide structure that can adapt to varying distances from the body. The waveguide is designed to support surface wave propagation across a range of frequencies and distances, making the system dynamically adaptable rather than requiring a fixed predetermined distance. This dynamic design reduces the complexity of precise positioning while maintaining high sensing sensitivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances sensing sensitivity by minimizing background noise and enabling convenient, comfortable monitoring of vital signs without skin contact, allowing multiplexed sensing of different body parts simultaneously.
Implementation Method 1
the waveguide is configured to propagate the transmitted signal in a spoof surface plasmon mode along the waveguide to produce an evanescent electromagnetic field
Implementation Method 2
the waveguide propagates the transmitted signal in a spoof surface plasmon mode along the waveguide to produce an evanescent electromagnetic field and to provide a received signal, wherein the waveguide is placed at a predetermined distance away from the body for non-contact sensing of a perturbation produced by a physiological motion of the body using the evanescent electromagnetic field, the perturbation produces a phase shift between the transmitted signal and the received signal
Data Source
AI summary
A sensor 104 for non-contact sensing of a physiological parameter of a body 102 is described. In an embodiment, the sensor 104 comprises: a waveguide, the waveguide comprises a metamaterial and is configured to receive a transmitted signal and to propagate the transmitted signal in a spoof surface plasmon mode along the waveguide to produce an evanescent electromagnetic field and to provide a received signal, wherein the waveguide is placed at a predetermined distance away from the body 102 for non-contact sensing of a perturbation produced by a physiological motion of the body 102 using the evanescent electromagnetic field, the perturbation produces a phase shift between the transmitted signal and the received signal for use in determining the physiological parameter of the body 102. A system 100 and a method 200 for non-contact sensing of a physiological parameter of a body 102 are also described.