Active Resonator Target Circuit for Longer-Range Inductive Sensing
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Solution Overview
Problem
Resonant inductive sensors have a limited sensing range when used with conductive targets, and existing methods to extend this range are not effective in eliminating autonomous oscillations of the target resonator.
Innovation Solution
The implementation of an active resonator target with a negative resistance circuit that couples with the sensor resonator, canceling the loss factor of the target resonator and eliminating autonomous oscillations, thereby enhancing the target quality factor and extending the sensing range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a resonant target is used to extend sensing range, then sensing range is improved, but autonomous oscillations occur in the target resonator
Solution Approach 1:
The patent converts the harmful loss factor in the target resonator into a beneficial element by introducing a negative resistance circuit that actively compensates for the losses. This allows the target resonator to maintain high Q-factor and extended sensing range while preventing autonomous oscillations through controlled impedance matching.
Solution Approach 2:
The patent changes the electrical parameters of the target resonator by introducing a variable negative resistance that dynamically adjusts to cancel the loss factor. This parameter modification enables the system to achieve both extended sensing range and suppression of unwanted oscillations.
2Reliability
If negative resistance is used to cancel loss factor, then target quality factor is improved, but device complexity increases
Solution Approach 1:
The patent introduces a negative resistance circuit as an intermediary element between the sensor resonator and target resonator. This intermediary actively compensates for energy losses in the target resonator, improving the quality factor without requiring fundamental changes to the resonator structure itself.
Solution Approach 2:
The patent modifies the electrical parameters of the target resonator by introducing a variable negative resistance that dynamically adjusts to cancel the loss factor. This parameter modification enables the system to achieve both extended sensing range and suppression of unwanted oscillations.
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 configuration significantly enhances the target quality factor, extending the sensing range by up to 500% of the sensor coil diameter while preventing autonomous oscillations of the target resonator.
Implementation Method 1
the sensor resonator LC circuit projects a magnetic sensing field
Implementation Method 2
the sensor resonator and target resonator form coupled resonators
Data Source
AI summary
A resonant inductive sensing system includes an active resonator target that balances losses in the target resonator. The resonant sensor includes a sensor resonator LC circuit and a resonant target including a target resonator Lt/Ct circuit characterized by a loss factor Rts and a target quality factor Qt. The sensor resonator LC circuit and the target resonator Lt/Ct circuit are configured for operation as coupled resonators. The resonant sensor includes a sensor circuit configured to drive the resonant sensor, such that the sensor resonator LC circuit projects a magnetic sensing field based on a sensor quality factor Q, and an active negative resistance circuit −Ra coupled to the target resonator Lt/Ct circuit, and configured to substantially cancel the loss factor Rts, such that target quality factor Qt is substantially Qt=(√[Lt/Ct]/Rts)(RaRts/[RaRts−Lt/Ct]).