Inductive Loop Resonator Control for Low-Emission Vital Sign Sensing
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Solution Overview
Problem
Inductive sensing technologies face challenges in complying with electromagnetic compatibility (EMC) regulations and minimizing power consumption while maintaining signal quality for wearable body sensors, particularly in clinical settings where stringent EMC restrictions and limited battery capacity are concerns.
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 control the oscillator amplitude, allowing for efficient signal measurement and stabilization, thereby addressing EMC compliance and power consumption issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oscillator amplitude is increased to improve signal quality and signal-to-noise ratio, then measurement reliability is improved, but RF emission increases causing EMC compliance issues and higher power consumption
Solution Approach 1:
The patent implements a feedback control mechanism where the measured amplitude of electromagnetic signals from the body is fed back to the oscillator circuit to dynamically adjust its drive amplitude. This closed-loop control ensures the oscillator operates at optimal amplitude for reliable measurement while automatically reducing amplitude when signals are strong, thereby maintaining EMC compliance and reducing unnecessary RF emission.
Solution Approach 2:
The system transitions from a static fixed-amplitude oscillator to a dynamic adjustable-amplitude oscillator. The oscillator drive amplitude is dynamically adapted based on real-time measurement conditions and feedback signals, allowing the system to optimize between measurement reliability and EMC compliance depending on the current sensing requirements and environmental conditions.
2Measurement precision
If the oscillator amplitude is increased to improve signal quality, then signal-to-noise ratio is improved, but power consumption increases reducing battery life
Solution Approach 1:
The feedback control mechanism monitors the measured signal amplitude and adjusts the oscillator drive amplitude accordingly. When sufficient signal strength is achieved for reliable measurement, the system reduces the oscillator amplitude to minimize power consumption, thereby extending battery life while maintaining adequate measurement precision.
Solution Approach 2:
The system dynamically changes the oscillator drive amplitude parameter based on measurement conditions. By adjusting this critical parameter in real-time, the system optimizes the balance between signal-to-noise ratio and power consumption, ensuring reliable measurements are achieved with minimal energy expenditure.
3Measurement precision
If a high-resolution ADC is used to improve measurement precision, then signal measurement accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The feedback control system uses the ADC measurements to regulate oscillator amplitude, creating a closed-loop that compensates for the limited ADC resolution. By dynamically adjusting the oscillator drive based on feedback, the system effectively achieves high measurement precision without requiring a complex high-resolution ADC, thereby reducing device complexity.
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 reduces RF emission and enhances signal-to-noise ratio, ensuring reliable measurement of vital signs while maintaining EMC compliance and optimizing power usage.
Implementation Method 1
Inductive sensing is based on magnetic induction and has several advantages over conductive and capacitive sensing
Implementation Method 2
An electromagnetic excitation signal can be propagated into a body to be investigated. 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
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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.