Loop Resonator Feedback Control for Low-Power Inductive Body Sensing
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Solution Overview
Problem
Inductive sensing technologies face challenges in complying with electromagnetic compatibility (EMC) regulations and minimizing power consumption for wearable body sensors, particularly in clinical settings, where stringent EMC restrictions and limited battery capacity require balancing signal quality with reduced power usage.
Innovation Solution
A physiological parameter inductive sensing system utilizing a loop resonator with an oscillator circuit, an analog to digital converter with reduced bits or trits, and a feedback controller to stabilize oscillator amplitude, allowing for efficient signal measurement and control, thereby optimizing signal quality and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amplitude of the oscillator circuit is increased to improve signal quality and signal-to-noise ratio, then measurement reliability is improved, but power consumption increases
Solution Approach 1:
The patent implements a feedback control mechanism where the measured amplitude of electromagnetic signals from the body is used to dynamically adjust the oscillator circuit amplitude. The system continuously monitors the signal amplitude and modifies the excitation signal strength accordingly, ensuring optimal signal quality while minimizing unnecessary power consumption. This closed-loop control allows the system to maintain reliable measurements at the lowest necessary power level.
Solution Approach 2:
The oscillator circuit amplitude is made dynamic rather than fixed. The system adapts the excitation signal amplitude in real-time based on the measured body signals and environmental conditions. This dynamic adjustment allows the system to increase power only when needed for reliable measurement and reduce power when signal conditions are favorable, resolving the contradiction between measurement reliability and power consumption.
2Measurement precision
If the oscillator amplitude is increased to improve signal quality, then signal-to-noise ratio is improved, but electromagnetic compatibility compliance becomes more difficult
Solution Approach 1:
The feedback mechanism measures the actual electromagnetic signal amplitude received from the body and uses this information to adjust the oscillator amplitude. This ensures that the excitation signal is strong enough to achieve good signal-to-noise ratio while avoiding excessive amplitudes that would cause EMC compliance issues. The system only uses the minimum necessary amplitude for reliable measurement.
Solution Approach 2:
The system dynamically changes the amplitude parameter of the oscillator circuit based on measured conditions. By adjusting this parameter in real-time, the system optimizes the balance between signal quality and electromagnetic field strength, achieving good signal-to-noise ratio while maintaining EMC compliance through adaptive parameter control.
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 effectively addresses EMC compliance and power efficiency, enhancing signal-to-noise ratio and reliability of vital sign measurements while maintaining low power consumption, enabling accurate tracking of physiological parameters like heart and lung dynamics without invasive contact.
Implementation Method 1
Inductive sensing is based on magnetic induction and has several advantages over conductive and capacitive sensing
Implementation Method 2
The excitation electromagnetic signal causes magnetic induction in the body, i.e. the generation of eddy currents in the tissue of the body due to the application of an external magnetic field
Data Source
AI summary
A physiological parameter inductive sensing system has a loop resonator which inductively couples with electromagnetic signals emitted from the body. The loop resonator forms part of an oscillator circuit, and negative feedback control is used to control the oscillator circuit, based on a measured oscillation amplitude. Within the feedback control loop, an analog to digital converter is used with a first number of bits (or trits), and successive outputs of the analog to digital converter are combined to derive an output value with a resolution of a second number of bits, greater than the first number of bits (or trits). The feedback control of the amplitude of the oscillator circuit is achieved using the output value.