Human Body Communication Interference Subtraction
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Solution Overview
Problem
The human body acts as an antenna at the FM frequency band, limiting high-speed ultra-low power (ULP) Human Body Communication (HBC) implementation due to interference, with existing solutions like adaptive frequency hopping and fixed narrowband signaling being energy-inefficient and requiring bulky filters.
Innovation Solution
The implementation of capacitive voltage-mode signaling and time-domain interference sampling and subtraction techniques to enhance communication reliability and efficiency by utilizing the human body as a broadband channel, suppressing interference and achieving flat-band frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the human body is used as a conducting medium for HBC, then power consumption is reduced and security is improved, but interference from the body acting as an antenna at FM frequency band limits high-speed implementation
Solution Approach 1:
The patent changes the operating frequency from the problematic FM band to a higher frequency band (e.g., 676.5 MHz to 679.5 MHz) where the body's antenna effect is minimized. This parameter change allows the system to maintain ultra-low power consumption while achieving high-speed data transmission with improved communication reliability by operating in a frequency range where the body does not resonate.
Solution Approach 2:
The patent converts the harmful body antenna effect at FM frequencies into a beneficial narrowband interference that can be precisely characterized and subtracted. By sampling the interference component and subtracting it from the received signal, the system transforms the previously problematic body resonance into a manageable signal component that enables high-speed communication.
2Reliability
If adaptive frequency hopping or fixed narrowband signaling is used to circumvent interference, then communication reliability is improved, but energy efficiency deteriorates and bulky filters are required
Solution Approach 1:
The patent extracts and removes the interference component from the received signal by sampling the interference (when no data is transmitted) and subtracting it from the signal received during data transmission. This extraction approach eliminates the need for bulky filters and energy-intensive frequency hopping, achieving both high reliability and energy efficiency.
Solution Approach 2:
The patent implements a feedback mechanism where the received signal is sampled during interference-only periods and then subtracted from the signal received during data transmission periods. This feedback-based interference cancellation enables reliable high-speed communication without requiring bulky filters or consuming excessive energy.
3Object-affected harmful factors
If narrowband signaling is used to avoid interference, then interference suppression is achieved, but device complexity increases due to bulky filters
Solution Approach 1:
The patent replaces the mechanical/filter-based interference suppression approach with a signal processing approach. Instead of using bulky physical filters to block FM band interference, the system uses digital subtraction of sampled interference from the received signal, dramatically reducing device complexity while maintaining effective interference suppression.
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
These techniques enable efficient, secure, and low-energy communication by transforming the human body into a broadband channel with megabits/second data transfer speeds, overcoming interference challenges and improving power efficiency compared to previous narrowband wireless or HBC systems.
Implementation Method 1
capacitive voltage-mode communication between wearable health monitoring devices
Implementation Method 2
human body is used as a conducting medium, which exhibits significantly lower loss than radio frequency propagation through air
Implementation Method 3
the human body acts as an antenna at the FM frequency band
Data Source
AI summary
A communication interference rejection system comprising a relatively low-impedance voltage mode driver output which receives a signal from a sensor, the sensor near a user's skin, a receiver operatively connected to a device connected to a body of a user, wherein the receiver configured to receive a signal transmitted through the body of the user. The signal comprises a relatively substantially small constant amplitude component and a relatively large sinusoidal or modulated interference component, the interference component due to human body antenna effect, the receiver comprising a high-impedance termination to minimize channel loss, the receiver further configured to receive frequencies in the 10 KHz to 10 MHz range.