Double-Wrapped Coil for Projective Capacitance Sensing
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Solution Overview
Problem
Conventional projective capacitive touch and near touch-sensing devices have limitations in sensing geometry and signal/noise ratio, which affect their efficiency and cost-effectiveness in various applications.
Innovation Solution
The use of a double-wrapped coil configuration with a long sensing gap between two physically and electrically isolated coils, printed on a flexible substrate, enhances the signal/noise ratio and allows for efficient capacitance sensing through a larger capacitance change when touched or near-touched, enabling broader and more cost-effective applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional diamond-shaped conductive pads are used in a matrix configuration, then the device can be manufactured with simple printing processes, but the sensing geometry is limited to the edges of the pads and the signal/noise ratio is reduced
Solution Approach 1:
The conventional diamond pad is segmented into two separate coils that are physically and electrically isolated from each other. This segmentation allows each coil to be optimized independently for capacitive coupling, improving the signal/noise ratio while maintaining ease of manufacture through printing processes.
Solution Approach 2:
The invention transitions from a planar diamond pad configuration to a three-dimensional double-wrapped coil structure. The coils are wrapped around each other in a helical configuration, adding a vertical dimension that increases the effective sensing aperture and improves capacitive coupling without compromising manufacturing simplicity.
2Device complexity
If diamond-shaped conductive pads with gaps are used to form coplanar capacitors, then the device structure is simple, but the effective sensing geometry is limited to the edges of the pads
Solution Approach 1:
The double-wrapped coil structure nests one coil within the other in a helical configuration. This nested arrangement allows the sensing aperture to extend beyond the outer dimensions of the individual coils, effectively increasing the sensing area while maintaining structural simplicity through the nested geometry.
Solution Approach 2:
The helical wrapping of the coils adds a vertical dimension to the sensing geometry, allowing the effective sensing aperture to extend in three dimensions rather than being confined to a planar edge region. This increases the functional sensing area without significantly increasing the planar footprint.
3Ease of manufacture
If conventional coplanar capacitor geometry is used between adjacent pads, then the manufacturing process is straightforward, but the capacitance change signal is weak
Solution Approach 1:
The conventional coplanar capacitor is segmented into two separate helical coils that are physically and electrically isolated. This segmentation allows for optimized capacitive coupling between the coils, producing a stronger signal while maintaining manufacturing ease through printing processes.
Solution Approach 2:
The helical wrapping configuration adds a vertical dimension to the capacitive coupling, increasing the effective overlap area between the drive and sense coils. This dimensional change enhances the capacitance change signal strength while keeping the manufacturing process straightforward.
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 double-wrapped coil design improves the sensitivity and efficiency of touch and near touch sensing, allowing for lower-cost, flexible, and versatile implementations in devices such as keyboards and control panels connected to cloud services, while maintaining sensitivity through thin interlayers like gloves.
Implementation Method 1
The double-wrapped coil configuration with a long sensing gap between two physically and electrically isolated coils enhances the signal/noise ratio and allows for efficient capacitance sensing through a larger capacitance change when touched or near-touched
Implementation Method 2
A drive signal can be applied to one of the pads, on either the row or the column, and, by capacitive coupling, the signal is picked up from the other pad
Data Source
AI summary
Touch user interfaces have been an essential element in the use of smartphones and tablets. An improved touch or near touch sensing structure made of a printed conductive double-wrapped coil is disclosed. A printable substrate is used to provide a base for the double-wrapped coil. On the printable substrate, a double-wrapped coil is printed using at least one flexible conductive material. The double-wrapped coils can be printed sequentially, simultaneously, parts of the two coils are printed and then the rest of the coil parts are printed, or any other useful printing order. The double-wrapped coil provides an increased sensing area and therefore can compute a more efficient capacitance.