Capacitive Touch Sensing with Peak Detection and Deferred DSP

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Solution Overview

Problem

Existing touch input detection systems are burdensome and inefficient, particularly when rapid measurements are required, as they digitally process each electrode output, consuming significant computing resources and not optimized for time domain differential processing.

Innovation Solution

The system measures peak voltage at electrodes over a measurement period and defers digital signal processing until after peak electrode capacitance is sampled, using a capacitive sensor with a driver circuit, measurement circuit, and signal processing circuit that includes a peak detector and time domain differential processing to determine touch inputs, suitable for both self-capacitance and mutual capacitance sensors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If digital signal processing is performed on each electrode output in real-time, then touch input detection accuracy is improved, but computing resource consumption increases significantly

Engineering Contradiction:

Improvetouch input detection accuracyVSAvoidcomputing resource consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The system performs preliminary analog processing of electrode signals before digital conversion, including amplification, filtering, and peak detection in the analog domain. This preliminary action reduces the complexity and computational load of subsequent digital signal processing while preserving touch detection accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces digital signal processing operations with analog circuit implementations. Specifically, analog amplifiers, filters, and peak detectors substitute for computationally intensive digital algorithms, thereby reducing computing resource consumption while maintaining measurement precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Speed

If rapid measurements are performed on multiple electrodes simultaneously, then response time is improved, but device complexity increases

Engineering Contradiction:

Improveresponse timeVSAvoidcircuit complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent combines multiple electrode measurement circuits into a shared architecture with common components such as multiplexers, reference voltage sources, and signal processing stages. This merging approach enables rapid simultaneous measurement of multiple electrodes while reducing overall device complexity through component sharing.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The system employs periodic sampling and multiplexed measurement sequences that rapidly cycle through multiple electrodes in a structured manner. This periodic action approach allows fast response times by systematically acquiring data from all electrodes in quick succession while using a single measurement channel.

Inventive Principle:

Principle #19Periodic action

3Measurement precision

If time domain differential processing is implemented, then touch signature accuracy is improved, but processing overhead increases

Engineering Contradiction:

Improvetouch signature accuracyVSAvoidprocessing overhead

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs preliminary analog differentiation and peak detection before digital processing. By detecting voltage peaks and calculating time-domain differentials in the analog domain using dedicated circuits, the system reduces the processing overhead required in the digital domain while maintaining accurate touch signature extraction.

Inventive Principle:

Principle #10Preliminary action

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 conserves computing resources and enables rapid measurement of electrode capacitance, reducing power consumption and response time while maintaining high signal fidelity and accuracy in detecting touch inputs.

Implementation Method 1

a driver circuit adapted to providing a stimulus voltage, for example a repeating square wave, to a capacitive coupling

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

The measurement circuit includes a peak detector and provides an output proportional to the peak voltage across the capacitive coupling over a measurement period

Methodology Applied

Scientific EffectPeak detection:

Implementation Method 3

a strobe electrode and a sense electrode defining a capacitive coupling therebetween, the capacitive coupling being adapted to vary in response to a touch input

Methodology Applied

Scientific EffectCapacitive sensing: Capacitance

Data Source

PatentUS11730910B2Simultaneous time domain differential sensing and electric field sensing

Publication Date: 2023.08.22 ALSENTIS LLC

AI summary

Systems and methods for determining a touch input are provided. The systems and methods generally include measuring the peak voltage at an electrode over a measurement period and determining a touch input based on the peak voltage. The systems and methods can conserve computing resources by deferring digital signal processing until after a peak electrode capacitance has been sampled. The systems and methods are suitable for capacitive sensors using self-capacitance and capacitive sensors using mutual capacitance. The systems and methods are also suitable for capacitive buttons, track pads, and touch screens, among other implementations.