Non-Contact RF Sleep Disorder Diagnosis
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Solution Overview
Problem
Current methods for detecting periodic limb movements (PLM) during sleep are invasive, expensive, and require patients to sleep in a hospital lab, making them impractical for longitudinal studies and home monitoring.
Innovation Solution
A non-contact radio frequency motion sensing apparatus that emits pulsed RF signals, processes reflected signals to produce motion signals, and uses a processor to evaluate these signals and generate an indicator for periodic limb movement detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If continuous wave Doppler radar motion sensors are used for movement detection, then they can receive signals for both near and far objects, but this leads to false triggers due to motion artefact interference and high sensitivity at close range
Solution Approach 1:
The continuous detection range is segmented into multiple range gates (first range gate, second range gate, third range gate) with different sensitivity settings. The first range gate operates at high sensitivity for close-range detection, while the second and third range gates operate at lower sensitivity for medium and far-range detection, respectively. This segmentation allows the system to maintain high detection capability across all ranges while reducing false triggers from distant motion artifacts.
Solution Approach 2:
Different portions of the detection range are assigned different quality characteristics through range-specific sensitivity adjustment. Close-range detection (first range gate) uses high sensitivity to detect subtle movements, while medium-range (second range gate) and far-range (third range gate) detection use progressively lower sensitivity to filter out distant motion artifacts. This local quality differentiation resolves the contradiction between comprehensive detection capability and false trigger reduction.
2Reliability
If pulse Doppler motion sensor with range gating is used, then false triggers from distant objects are reduced, but the sensing region is limited to a specific range
Solution Approach 1:
Multiple range gates (first, second, and third range gates) are merged into a single integrated detection system. Each range gate targets a specific distance zone with appropriate sensitivity, and their combined output provides comprehensive detection coverage from close to far ranges while maintaining false trigger reduction benefits of range gating. This merging approach simultaneously achieves both reliability improvement and adaptability restoration.
Solution Approach 2:
The detection system is designed to perform multiple functions across different ranges: the first range gate handles close-range high-sensitivity detection, the second range gate handles medium-range detection, and the third range gate handles far-range detection. This multi-functionality allows a single system to adapt to various detection scenarios without being limited to a specific range, resolving the contradiction between false trigger reduction and detection versatility.
3Measurement precision
If impulse radar with narrow sensing region is used, then range resolution is improved, but difficulty sensing objects at medium ranges and RF interference issues arise
Solution Approach 1:
The system uses periodic pulse transmission with different pulse widths (first pulse width, second pulse width) to alternately illuminate different range zones. This periodic action with varying pulse characteristics enables the system to maintain good range resolution while improving detection reliability at medium ranges by adapting the pulse duration to the target distance, thereby resolving the contradiction between resolution and medium-range detection capability.
4Measurement precision
If traditional polysomnography with EMG sensors is used for PLM detection, then diagnostic accuracy is high, but the method is invasive, expensive, and requires hospital lab setting
Solution Approach 1:
The patent replaces the mechanical contact-based EMG sensor system with a non-contact radio frequency sensing system. The RF sensors detect limb movements through electromagnetic field interactions without physical contact, eliminating the need for skin preparation, sensor attachment, and hospital-based monitoring. This substitution maintains diagnostic accuracy for PLM detection while dramatically improving ease of operation and enabling home-based monitoring.
Solution Approach 2:
The system introduces radio frequency electromagnetic waves as an intermediary between the detection system and the patient's body movements. Instead of direct mechanical contact with EMG electrodes, the RF waves serve as a mediator that captures motion information non-invasively. This intermediary approach preserves the ability to detect PLM accurately while removing the invasiveness and operational complexity of traditional methods.
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
The system provides a reliable, unobtrusive method for detecting PLM, enabling monitoring in home environments and reducing the costs and invasiveness associated with traditional diagnostic methods.
Implementation Method 1
continuous wave (CW) Doppler radar motion sensors emit a continuous wave radio frequency (RF) carrier and mix the transmitted RF with the return echoes to produce a difference frequency equal to the Doppler shift produced by a moving target
Implementation Method 2
a receiver configured to receive reflected ones of the emitted radio frequency signals
Data Source
AI summary
A sensor may be configured to detect periodic limb movement in a sleeping person. The sensor may be a non-contact sensor, such as a radar motion sensor. The sensor may include a radio frequency transmitter for emitting radio frequency signals toward the person. The sensor may include a receiver for receiving reflected ones of the emitted radio frequency signals and processing the reflected ones of the emitted radio frequency signals to produce motion signal(s). A processor, such as one integrated with or coupled to the sensor, may evaluate the motion signals, such as in-phase and quadrature motion signals, and generate an indicator to identify occurrence of periodic limb movement in the motion signals based on the evaluation of the motion signals.