Biological Signal Processing Using Auto-Correlated Carrier Sequences
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Solution Overview
Problem
Biological signals are difficult to record non-invasively from a body surface due to low amplitude and interference from noise sources, such as electromagnetic radiation and mechanical vibrations, which conventional filtering techniques cannot effectively address.
Innovation Solution
A computer-implemented method and system using highly auto-correlated carrier sequence codes (HACS) for biological signal recording, where control signals are transmitted to a subject, and the received evoked biological signal is modulated and demodulated using a carrier sequence code with an autocorrelation function, allowing for noise artifact filtering based on peak to sideband ratio calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional filtering techniques are used to remove noise from biological signals, then noise reduction is achieved, but the filtering is ineffective when noise power spectrum overlaps with biological signal spectrum
Solution Approach 1:
The patent applies periodic modulation using a pseudo-random binary sequence (PRBS) carrier wave to the biological signal. By modulating the signal at a specific frequency and demodulating it later, the signal is shifted to a different frequency domain where it can be distinguished from overlapping noise, enabling effective filtering even when noise and signal spectra overlap
Solution Approach 2:
The patent introduces a PRBS carrier sequence as an intermediary to transfer the biological signal to a different frequency domain. This carrier sequence acts as a mediator that allows the signal to be separated from noise through correlation detection, where the known carrier sequence enables selective extraction of the modulated signal from the noisy environment
2Measurement precision
If electromagnetic shielding and vibrational isolation are used to minimize noise impact, then noise reduction is achieved, but these control measures are not feasible in real world applications
Solution Approach 1:
The patent replaces mechanical and electromagnetic shielding approaches with a signal processing approach. Instead of physically isolating the sensor from noise sources, the system uses digital signal processing techniques including modulation, correlation detection, and adaptive filtering to reject noise, thereby eliminating the need for complex physical shielding and isolation mechanisms
3Measurement precision
If the transmission source transmits energy towards the subject, then evoked biological signals are generated, but low amplitude signals are obscured by high amplitude ambient noise
Solution Approach 1:
The transmission source modulates the transmitted energy using a periodic PRBS carrier sequence, causing the biological tissue to generate evoked responses at the same modulation frequency. This periodic modulation allows the weak biological signals to be distinguished from ambient noise through frequency-selective correlation detection, effectively increasing signal detectability despite low amplitude
Solution Approach 2:
The system uses correlation detection with the known PRBS carrier sequence as a form of feedback mechanism. By continuously comparing the received signal with the transmitted carrier sequence and adjusting the detection based on the correlation output, the system enhances the detectability of weak evoked signals while suppressing uncorrelated ambient noise
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 enhances the signal-to-noise ratio of biological signals, effectively filtering out noise and reconstructing true biological signals even in high noise environments, improving the accuracy of biological signal recording.
Implementation Method 1
receiving at a receiver of the sensor an evoked biological signal in response to energy reflection returned from the subject
Implementation Method 2
modulating the sampled evoked biological signal with a carrier sequence code resulting in a modulated evoked biological signal
Implementation Method 3
The carrier sequence code has an autocorrelation function
Data Source
AI summary
A computer-implemented method for biological signal recording, including modulating a sampled evoked biological signal with a carrier sequence code resulting in a modulated evoked biological signal. The carrier sequence code has an autocorrelation function. The method includes demodulating the modulated evoked biological signal by calculating a convolution of the modulated evoked biological signal with the carrier sequence code resulting in an evoked biological signal spectrum. The evoked biological signal spectrum has a peak to sideband ratio as a function of the carrier sequence code. The method includes calculating deviations between each element of the sampled evoked biological signal and the peak to sideband ratio and filtering noise artifacts from the sampled evoked biological signal based on the deviations. Peak to sideband ratios may also be optimized by varying the sampling rate.