Metal Detector Coil Damping for Internal Resonance Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Metal detectors face challenges in efficiently detecting short time-constant metal targets due to electrical resonances in coil windings, which cause spurious signals and delay in receive synchronous demodulation, affecting the target-signal-to-uncancelled-soil-noise-signal ratio.
Innovation Solution
The implementation of a winding configuration with resistive components to damp internal resonances, specifically the second-order and third-order resonances, by connecting resistive components across different parts of the winding and using an active electrostatic screen to reduce the effective capacitance, thereby accelerating the decay of transients and minimizing spurious signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the coil winding is used without resistive damping components, then the Q factor is high and energy efficiency is improved, but internal resonances cause spurious signals and delay receive synchronous demodulation
Solution Approach 1:
The patent converts the harmful internal resonances and spurious signals into a beneficial outcome by introducing resistive damping components that specifically target and dampen these unwanted resonances. The damping components are strategically placed to reduce Q factors at specific resonance frequencies while preserving the overall detection performance, effectively transforming the problematic high-Q resonances into controlled, damped responses that eliminate spurious signals and reduce demodulation delay.
Solution Approach 2:
The patent changes the electrical parameters of the coil winding by introducing resistive components that modify the Q factor at specific frequency ranges. By adjusting the resistance values and positioning of damping components, the system optimizes the balance between maintaining sufficient Q for sensitivity and reducing Q at resonance frequencies to eliminate spurious signals and reduce demodulation delays.
2Reliability
If resistive components are added to damp internal resonances, then spurious signals are reduced and detection sensitivity is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent segments the coil winding into multiple sections with different damping characteristics. By dividing the winding into segments and applying resistive damping selectively to specific sections rather than uniformly across the entire coil, the system achieves effective resonance suppression while minimizing the total amount of damping material required, thus reducing complexity and cost.
Solution Approach 2:
The patent applies local quality by positioning resistive damping components at specific locations along the winding where internal resonances are most problematic. Rather than uniformly damping the entire coil, the damping is concentrated at strategic points where it most effectively reduces spurious signals, optimizing performance while minimizing added complexity.
3Use of energy by moving object
If the winding has high Q factor, then energy efficiency is improved, but transients decay slowly causing delay in receive synchronous demodulation
Solution Approach 1:
The patent applies dynamics by creating a frequency-dependent Q factor through the resistive damping components. The system maintains high Q factor at frequencies away from resonances to preserve energy efficiency, while dynamically reducing Q factor at specific resonance frequencies to accelerate transient decay. This dynamic parameter adjustment allows the coil to be energy-efficient during normal operation while quickly settling after transmit pulses.
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 solution enhances the sensitivity to short time-constant targets by reducing the delay in receive synchronous demodulation and minimizing spurious signals, improving the target-signal-to-uncancelled-soil-noise-signal ratio and overall detection performance.
Implementation Method 1
at least one resistive component for connecting a first part of the winding to a second part of the winding, wherein the resistive component is configured to damp an internal resonance of the winding with an order greater than 1
Implementation Method 2
using an active electrostatic screen to reduce the effective capacitance
Implementation Method 3
transmit electronics generating a repeating transmitted signal cycle of a fundamental period, which is applied to an inductor, for example a transmit winding, which transmits a resulting varying magnetic field
Implementation Method 4
receive electronics that process a received signal from a receiver/antenna that measures a received magnetic field
Data Source
AI summary
A winding of an antenna of a metal detector, the winding includes multi-turn wire with both ends connected to the metal detector; and at least one resistive component for connecting a first part of the winding to a second part of the winding. The first part or the second part are not both ends of the winding. The resistive component is configured to damp an internal resonance of the winding with an order greater than 1.