Capacitive Touch Sensing Circuit Multi-Frequency Noise Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional capacitive touch panels face inefficiencies in filtering lower frequency noises, leading to poor touch sensing efficiency and potential failure to meet frame report rate specifications.
Innovation Solution
The capacitive touch sensing circuit employs multiple periodic-wave signal generation modules, mixing modules, and integration modules to generate and integrate signals with different frequencies, allowing for extended integration cycles without reducing frame report rate, thereby filtering lower frequency noises effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If smaller frequency nf0 is used to filter lower frequency noises, then noise filtering capability is improved, but integration cycle 1/nf0 becomes longer and touch sensing efficiency deteriorates
Solution Approach 1:
The patent divides the touch sensing system into multiple independent channels, each with its own periodic-wave signal generation module, mixing module, and integration module. Each channel operates at different frequencies (nf0, 2nf0, 3nf0, etc.), allowing parallel processing of multiple frequency components simultaneously. This segmentation enables the system to maintain short integration cycles while effectively filtering various frequency noises through multiple parallel paths.
Solution Approach 2:
The patent employs periodic-wave signals with different frequencies (nf0, 2nf0, 3nf0, etc.) for driving electrodes and performing mixing operations. By using multiple periodic signals with harmonic frequency relationships, the system can synchronize integration cycles across different channels, achieving both short integration times and effective noise filtering through constructive interference of desired signals and destructive interference of noise components.
2Object-affected harmful factors
If smaller frequency nf0 is used to filter lower frequency noises, then noise filtering capability is improved, but frame report rate decreases
Solution Approach 1:
The patent segments the touch panel into multiple first channels and second channels, with each first channel processed by dedicated periodic-wave signal generation, mixing, and integration modules. This parallel channel structure allows simultaneous processing of multiple frequency components, enabling the system to maintain high frame report rates while effectively filtering lower frequency noises through coordinated integration across channels.
Solution Approach 2:
By using periodic-wave signals with frequencies nf0, 2nf0, 3nf0, etc., and synchronizing their integration cycles, the patent enables multiple channels to complete their sensing operations in parallel within the same frame period. This periodic multi-frequency approach allows the system to achieve both effective low-frequency noise filtering and high frame report rates.
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 enhances capacitive touch sensing efficiency by maintaining frame report rate while filtering lower frequency noises, improving noise reduction and touch sensing accuracy.
Implementation Method 1
N periodic-wave signal generation modules generate N first periodic-wave signals having N frequencies to N first channels respectively
Implementation Method 2
The N mixing modules receive the analog front-end signal from the analog front-end circuit module respectively and receive N second periodic-wave signals having the N frequencies respectively, and then mix the analog front-end signal and the N second periodic-wave signals respectively into N mixed signals
Implementation Method 3
The N integration modules receive the N mixed signals respectively and integrate the N mixed signals respectively to generate N output signals
Implementation Method 4
the sine-wave input signal TX is received and amplified by the parasitic mutual capacitance Cm at intersection points of horizontal electrodes E and vertical electrodes D of the capacitive touch panel TP
Data Source
AI summary
A touch sensing circuit includes N periodic-wave signal generation modules, an analog front-end circuit module, N mixing modules, and N integration modules. N is an integer. The N periodic-wave signal generation modules generate N first periodic-wave signals having N frequencies to N first channels of a capacitive touch panel. The analog front-end circuit module receives and demodulates the N first periodic-wave signals passing through N mutual capacitance at N intersection points of the N first channels and a second channel to output an analog front-end signal. The N mixing modules mix the analog front-end signal and N second periodic-wave signals having the N frequencies respectively into N mixed signals. The N integration modules integrate the N mixed signals to generate N output signals.