Trapezoidal Capacitive Sensor Layout for Narrow Pen Touch Detection
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Solution Overview
Problem
Capacitive touch sensors with rhombus-shaped elements face challenges in detecting narrow pen touches due to increased coplanar capacitance and reduced Signal-to-Noise Ratio (SNR) when the number of elements is increased to reduce the short diagonal length.
Innovation Solution
Employing a capacitance detection sensor composed of composite trapezoidal shapes that allow for the detection of vertical pen touch movements without increasing the number of detection sensors, using a Primary Shape CDA with vertically stacked Secondary Shape CDAs and a bundle of signal lines forming coplanar capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of rhombus-shaped detection elements is increased to reduce the short diagonal length for detecting narrow pen touches, then the detection capability for narrow touches is improved, but the coplanar capacitance increases and the Signal-to-Noise Ratio (SNR) decreases
Solution Approach 1:
The patent applies asymmetry by changing the detection element shape from a symmetric rhombus to an asymmetric trapezoid. The trapezoidal shape has a longer bottom base and a shorter top base, creating an asymmetric geometry that reduces coplanar capacitance while maintaining the ability to detect narrow pen touches. This asymmetric design allows the sensor to achieve both narrow touch detection capability and improved SNR by optimizing the shape dimensions rather than simply increasing the number of elements.
2Measurement precision
If the number of rhombus-shaped detection elements is increased, then the detection capability for narrow touches is improved, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the detection elements. Instead of increasing the number of rhombus elements, the invention changes the shape parameters to trapezoidal geometry with specific dimension ratios. This parameter change allows a single trapezoidal element to replace multiple rhombus elements, reducing device complexity while maintaining or improving detection capability for narrow touches.
3Measurement precision
If the short diagonal length of rhombus-shaped elements is reduced to detect narrow pen touches, then the detection precision is improved, but the coplanar capacitance increases
Solution Approach 1:
The asymmetric trapezoidal shape allows optimization of the detection area distribution. The longer bottom base provides sufficient area for capacitance detection while the narrower top portion enables detection of narrow pen touches. This asymmetric geometry decouples the relationship between detection precision and coplanar capacitance, allowing both requirements to be satisfied simultaneously without the direct proportionality that exists in symmetric rhombus shapes.
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
Enhances touch sensitivity and improves SNR by accurately detecting vertical coordinates without increasing the number of sub-CDAs, thereby reducing capacitance and maintaining detection accuracy.
Implementation Method 1
a bundle of signal lines formed by a plurality of CDA signal lines constituting a CDA column; when an arbitrary n-the CDA signal line in the signal line bundle is a Sensing Signal Line (SSL), the SSL is adjacent to either (n−1) the, where a first Voltage Forcing Line (VFL) is located and an alternating voltage is applied, or adjacent to the (n+1) the, where a second VFL is located and an alternating voltage is applied. Each VFL adjacent to the SSL is configured with either identical or different line widths, spacing, and facing lengths to form a Parallel-Plate Coplanar structure. Between the SSL and either the first VFL or the second VFL, a Coplanar Capacitor is formed.
Data Source
AI summary
The present invention relates to a capacitive touch input device utilizing the capacitive sensing method for detecting touch inputs from a finger or a similar conductive object. More specifically, it pertains to a capacitance detection device designed to facilitate the detection of touch coordinates based on the vertical movement of a pen by employing a capacitive detection sensor composed of a composite trapezoidal shape.