Center-Tapped Inductive Position Sensing for Miniaturized EMC-Robust Coils
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Solution Overview
Problem
Conventional inductive position sensors face challenges in maintaining accurate signal strength and electromagnetic compatibility (EMC) immunity as they are miniaturized, leading to increased susceptibility to noise and interference.
Innovation Solution
A center-tapped transmit coil system is used, where the target's position induces an inductance imbalance, allowing for a single step of induction and larger useful signal amplitude, enabling miniaturized designs with improved EMC performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional inductive position sensors are miniaturized, then device size is reduced, but signal strength diminishes and EMC immunity deteriorates
Solution Approach 1:
The transmit coil is divided into two separate parts (first and second transmit coils) that are electrically independent. Each coil part connects to a separate receive input, creating independent signal paths. This segmentation allows the system to maintain adequate signal strength from each individual coil while keeping the overall device compact, as each coil can be optimized for its specific function without requiring excessive size.
Solution Approach 2:
The patent introduces a third dimension to the signal reception by utilizing the center-tap connection as an additional independent receive input. Instead of using only the two ends of the transmit coil, the center-tap provides a third electrical coupling path to the receiver, creating a three-dimensional signal space that enhances measurement capabilities and signal strength without increasing physical coil size.
2Measurement precision
If a single TX coil and three RX coils system is used, then position sensing is achieved, but the coil system size must be large to maintain adequate signal strength
Solution Approach 1:
The patent combines the functions of separate transmit and receive coils into a single center-tapped transmit coil structure. The same physical coil serves as both the transmit element and the receive element through its three terminals (first terminal, center-tap, second terminal). This merging eliminates the need for separate RX coils while maintaining position sensing capability, significantly reducing the overall coil system area.
Solution Approach 2:
The center-tapped transmit coil performs multiple functions simultaneously: it acts as the transmit coil for generating the magnetic field, and through its three terminals, it provides three independent signal paths for reception. This multi-functionality allows a single coil structure to replace what would traditionally require separate TX and RX coils, reducing the required coil system area while maintaining measurement precision.
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 solution provides larger received signal strengths and better EMC performance by relying on a single induction step, reducing coil and coupling requirements, thus facilitating compact sensor designs.
Implementation Method 1
an integrated circuit (IC) is used to excite a transmit (TX) coil, typically operating in the few MHz frequency range. This excitation induces eddy currents in the target. The eddy currents then induce currents in a set of three receive (RX) coils
Implementation Method 2
A transmitter that includes a positive output terminal connected to the first terminal of the transmit coil and a negative output terminal connected to the second terminal of the transmit coil. The transmitter is designed to apply an oscillating signal between the first and second terminals of the transmit coil. A change of the position of the target results in a change of the inductance imbalance of the center-tapped transmit coil.
Data Source
AI summary
A position sensor for determining the position of a target includes a center-tapped transmit coil with three terminals: a first terminal, a center-tap, and a second terminal. The sensor has a transmitter that applies an oscillating signal across the first and second terminals of the transmit coil. A receiver is connected to the first terminal, second terminal, and center-tap of the transmit coil. The processing circuit calculates the target's position by applying a transformation to the signals received from the three terminals.