Doppler Radar Respiration Monitoring via Vector Scalar Product

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Solution Overview

Problem

Current Doppler radar sensors operating below 25 GHz face challenges in reliably detecting respiration activity due to large wavelengths compared to thorax motion amplitudes, leading to inaccurate signal interpretation and high false alarm rates in clinical settings.

Innovation Solution

A method using a two-channel Doppler radar sensor that calculates a scalar product of normalized time derivatives of electromagnetic signals to determine the change from expiration to inspiration, allowing for breath-to-breath detection with reduced false alarms and increased accuracy, employing a criterion based on the angle between vectors defined by time derivatives for reliable thorax movement analysis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If Doppler radar sensors operating below 25 GHz are used, then the device complexity and cost are reduced, but the measurement precision of respiration activity deteriorates due to large wavelengths compared to thorax motion amplitudes

Engineering Contradiction:

Improvedevice complexityVSAvoidmeasurement precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent transitions from single-channel to two-channel Doppler radar signal processing, adding a temporal dimension to the measurement. By comparing signals at two different time points (t1 and t2), the system can detect direction changes of thorax movement, thereby improving measurement precision without increasing hardware complexity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent changes the evaluation parameter from raw signal amplitude to the scalar product of normalized time derivatives of signals at different time points. This parameter transformation enables reliable detection of respiration direction changes even with low-frequency radar signals, resolving the contradiction between device simplicity and measurement precision

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If conventional Doppler radar signal interpretation is used, then the ease of operation is maintained, but the reliability of respiration detection deteriorates due to high false alarm rates in clinical settings

Engineering Contradiction:

Improveease of operationVSAvoidreliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces conventional signal amplitude-based detection with a vector-based directional analysis method. By calculating the scalar product of time derivative vectors at different time points, the system objectively determines respiration direction changes, eliminating subjective signal interpretation and reducing false alarms while maintaining ease of operation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system continuously monitors the scalar product value and uses feedback to identify reliable respiration events. When the scalar product indicates a direction change consistent with actual respiration physiology, the system confirms the detection, thereby improving reliability without complicating operation

Inventive Principle:

Principle #23Feedback

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

This approach enables reliable and accurate breath-to-breath detection of inspiration and expiration, reducing false alarm rates and improving the accuracy of breathing rate monitoring without requiring complex signal processing or hardware-defined parameters, thus providing a cost-effective solution for remote respiration monitoring.

Implementation Method 1

emitting an electromagnetic signal towards the patient; receiving a reflected electromagnetic signal reflected from the patient

Methodology Applied

Scientific EffectElectromagnetic radiation and reflection: Reflection

Implementation Method 2

Doppler radar sensors have been identified as a promising technology for contactless measurements of respiration and cardiac activity

Methodology Applied

Scientific EffectDoppler effect: Doppler Effect

Data Source

PatentUS8870785B2Contactless respiration monitoring of a patient

Publication Date: 2014.10.28 KONINKLIJKE PHILIPS NV

AI summary

Respiration of a patient is detected by emitting an electromagnetic signal towards the patient; receiving a reflected electromagnetic signal reflected from the patient; converting the reflected electromagnetic signal, yielding a first signal; phase-shifting the reflected electromagnetic signal and converting the phase-shifted reflected electromagnetic signal, yielding a second signal; determining a first vector being defined by the time derivatives of the first signal and the second signal, for a common first point in time; determining a second vector being defined by the time derivatives of the first signal and the second signal, for a common second point in time; and calculating the scalar product of the normalized first vector and the normalized second vector as an indicator value for a change from expiration to inspiration of the patient or vice versa. A change from expiration to inspiration of the patient or vice versa is preferably indicated if the indicator value is below a threshold value, preferably below a value of 0. In this way, respiration is monitored contactlessly and remotely based on the Doppler radar principle which is reliable and easy to handle.