Single-Chain RF Motion Detection Using Phase-Difference Baselines
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Solution Overview
Problem
Existing RF sensing technologies using a single RF chain for motion detection are less accurate than those with multiple chains due to interference from sampling frequency offset, carrier frequency offset, and timing synchronization errors, and amplitude-based detection is not as sensitive as phase-based detection.
Innovation Solution
A single RF chain system uses phase differences between tones to identify and remove interference caused by sampling frequency offset, carrier frequency offset, and timing synchronization errors, determining a baseline when motion is absent and comparing phase differences with this baseline to detect the presence or absence of motion using mean squared error (MSE) thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple RF chains are used for phase-based motion detection, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates virtual copies of multiple RF chain functionality through signal processing. By generating synthetic reference signals and comparing received signals against these virtual references, the system achieves phase-based motion detection accuracy equivalent to multiple physical RF chains while using only a single physical chain, thus resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent replaces the mechanical/physical system of multiple RF chains with a signal processing system. Instead of using multiple physical radio frequency components to achieve phase comparison, the invention uses digital signal processing techniques including FFT, phase difference calculation, and interference removal algorithms to substitute the physical multi-chain architecture, thereby maintaining measurement precision while reducing device complexity and cost
2Device complexity
If amplitude-based motion detection is used in single RF chain devices, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent fundamentally changes the detection parameter from amplitude to phase. By extracting phase information from the received signals and comparing phase differences between reference and received signals, the system achieves high sensitivity motion detection while maintaining single RF chain simplicity. This parameter transformation allows the system to overcome the inherent limitation of amplitude-based detection and achieve phase-based precision with simplified hardware
3Measurement precision
If phase-based detection is used in single RF chain systems, then measurement precision is improved, but reliability deteriorates due to interference from sampling frequency offset, carrier frequency offset, and timing synchronization errors
Solution Approach 1:
The patent converts the harmful effects of frequency offsets and synchronization errors into beneficial information. By deliberately introducing known frequency offsets in the reference signal generation and using the phase difference measurements to identify and compensate for these offsets, the system transforms potential sources of error into calibration opportunities. The interference patterns caused by offsets are used to determine and correct the offset values themselves, thereby improving reliability while maintaining phase-based detection precision
Solution Approach 2:
The patent implements feedback mechanisms where the detected phase differences and identified interference patterns are used to adjust and correct the reference signal generation parameters. The system continuously monitors for frequency offsets and timing errors, then feeds this information back to adjust the reference signal frequency and timing, creating a self-correcting system that maintains high measurement precision and reliability even in the presence of interference
Data Source
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AI summary
In an aspect, a wireless device receives one or more sensing sets. Each sensing set has one or more sensing packets. The wireless device determines one or more motion detection metrics. Each motion detection metric is based on phase differences between tones of the one or more sensing packets for each of the one or more sensing sets. The wireless device determines one or more detected motion magnitudes based on a comparison of each motion detection metric for each of the one or more sensing sets and a baseline metric. The wireless device detects a motion based on at least a portion of the one or more detected motion magnitudes exceeding a first motion threshold.