Hadamard Matrix Driving for Capacitive Touch Sensitivity
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Solution Overview
Problem
Capacitive touch screens face a trade-off between receive sensitivity and driving time, where enhancing sensitivity leads to increased driving time, which reduces sensing speed, and existing methods using Hadamard matrices limit the dynamic range of reception circuits.
Innovation Solution
A coordinate indicating apparatus with a channel electrode system that applies continuous driving signals corresponding to a Hadamard matrix, excluding a time section where signals have the same value, to enhance sensitivity without increasing driving time, by calculating capacitance at intersection points and using sub-groups with shared electrodes to determine object location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If driving time is increased to enhance receive sensitivity of the sensor, then receive sensitivity is improved, but sensing speed is reduced
Solution Approach 1:
The patent applies periodic driving signals corresponding to Hadamard matrix patterns to multiple driving electrodes simultaneously. This periodic modulation allows the system to encode multiple channels of driving signals in a time-multiplexed manner, enabling the receiver to decode capacitance changes from multiple electrodes through correlation detection. This approach enhances receive sensitivity by accumulating signal energy over multiple periodic cycles while maintaining sensing speed through efficient parallel processing of the periodic signals.
2Measurement precision
If Hadamard matrices are used to generate multiple driving signals, then receive sensitivity is enhanced, but dynamic range requirements of reception circuit increase
Solution Approach 1:
The patent extracts and processes only the relevant correlation components from the received signals by comparing them with the known Hadamard matrix patterns. Instead of attempting to process the full dynamic range of all received signals simultaneously, the system extracts the specific signal components corresponding to each driving electrode by correlating with the applied Hadamard codes. This extraction approach reduces the effective dynamic range requirement by focusing computation on the relevant signal portions rather than the entire signal spectrum.
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 approach allows for improved receive sensitivity without prolonging driving time, enabling detection of minute capacitance changes and reducing dynamic range requirements, thus enhancing sensing speed and sensitivity.
Implementation Method 1
a channel electrode 110, which includes a first plurality of electrodes 111-1 to 111-8 arranged in a first direction, and a second plurality of electrodes 112-1 to 112-6 arranged in a second direction perpendicular to the first direction, and which has capacitance between the first plurality of electrodes 111-1 to 111-8 and the second plurality of electrodes 112-1 to 112-6
Implementation Method 2
the capacitance being changed by an approaching contact object
Data Source
AI summary
A coordinate indicating apparatus includes a channel electrode which includes a first plurality of electrodes arranged in a first direction and a second plurality of electrodes arranged in a second direction perpendicular to the first direction, and which has capacitance between the first plurality of electrodes and the second plurality of electrodes, the capacitance being changed by an approaching contact object; a driver configured to apply driving signals to the first plurality of electrodes simultaneously; a receiver configured to receive response signals from the second plurality of electrodes; and a controller configured to determine a location of the contact object based on the driving signals transmitted to the first plurality of electrodes and the response signals received from the second plurality of electrodes, wherein the driver is configured to simultaneously apply, to the first plurality of electrodes, continuous driving signals according to a matrix corresponding to a Hadamard matrix, and wherein the driving signals exclude a time section.