Switchable Band-Pass Filter for Finger and Pen Touch Sensing

Solution Overview

Problem

Existing touchscreen display devices face challenges in reliably sensing touch inputs from different types of objects, such as fingers and pens, due to limitations in band pass filter technology, which often require separate filters for each type, occupying significant area.

Innovation Solution

A band pass filter circuit that can switch between differential and single-ended modes, sharing capacitors to filter signals from both fingers and pens, reducing the overall area required.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If separate band pass filters are used for different types of touch objects (fingers and pens), then touch input sensing reliability is improved, but the circuit area occupied increases significantly

Engineering Contradiction:

Improvetouch input sensing reliabilityVSAvoidcircuit area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The band pass filter circuit is designed to perform multiple functions by supporting both differential mode and single-ended mode operations. The same physical circuit and capacitors can filter signals from different types of touch objects (fingers and pens) by switching between modes, eliminating the need for separate filter circuits for each object type.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The circuit incorporates dynamic switching capability between differential and single-ended modes through controlled switching elements. This allows the filter characteristics to be dynamically adjusted based on the type of touch object being detected, enabling the circuit to adapt its filtering behavior rather than requiring fixed separate circuits.

Inventive Principle:

Principle #15Dynamics

2Area of stationary object

If a single band pass filter is used for both fingers and pens, then circuit area is reduced, but touch input sensing reliability deteriorates

Engineering Contradiction:

Improvecircuit areaVSAvoidtouch input sensing reliability

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The band pass filter circuit is designed to perform multiple functions by supporting both differential mode and single-ended mode operations. The same physical circuit and capacitors can filter signals from different types of touch objects (fingers and pens) by switching between modes, eliminating the need for separate filter circuits for each object type.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The circuit changes its operational parameters by switching between differential and single-ended modes. This parameter change allows the same physical circuit to have different filtering characteristics optimized for different touch object types, maintaining reliability while using a single circuit.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If different types of band pass filters are used for different touch objects, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvedetection resolutionVSAvoidcircuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The circuit incorporates dynamic switching capability between differential and single-ended modes through controlled switching elements. This allows the filter characteristics to be dynamically adjusted based on the type of touch object being detected, enabling the circuit to adapt its filtering behavior rather than requiring fixed separate circuits.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The band pass filter circuit is designed to perform multiple functions by supporting both differential mode and single-ended mode operations. The same physical circuit and capacitors can filter signals from different types of touch objects (fingers and pens) by switching between modes, eliminating the need for separate filter circuits for each object type.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12375065B2Band pass filter circuit and sensor device including the same

Publication Date: 2025.07.29 SAMSUNG DISPLAY CO LTD

AI summary

A band pass filter circuit includes an amplifier circuit having a first input terminal to receive a first analog signal; a second input terminal to receive a second analog signal; first and second output terminals; capacitors; and switches. In a first switching mode, the switches are controlled so that the amplifier circuit and a first group of the capacitors connected between the input and output terminals operate as a first band pass filter filtering the first and second analog signals in a differential mode. In a second switching mode, the switches are controlled so that the amplifier circuit and second and third groups of the capacitors form second band pass filters filtering each of the first and second analog signals in a single-ended mode.