Capacitive Touch Sensing With DC-Free Codes for Noise Reduction
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Solution Overview
Problem
Existing capacitive touch screen technologies face challenges in efficiently detecting touches due to high noise levels and resource wastage from measuring mean background screen responses, leading to low signal-to-noise ratios and inefficient use of sensing time.
Innovation Solution
Implementing DC-free code division multiplexing (CDM) to encode drive signals with orthogonal codes, excluding mean background screen responses, and subtracting offset components to enhance signal detection and reduce noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacitive touch screen sensing methods are used to measure mean background screen responses, then touch detection can be performed, but noise levels are high and signal-to-noise ratio is low
Solution Approach 1:
The patent extracts and removes the mean background screen response from the sensing measurements. By separating the background component from the touch signal, the system eliminates a major source of noise and interference, thereby improving the signal-to-noise ratio and touch detection accuracy without requiring additional hardware
Solution Approach 2:
The patent changes the temporal parameters of the sensing measurements by taking multiple measurements at different time points and computing their mean. This temporal parameter change allows the system to distinguish between static background responses and dynamic touch signals, effectively filtering out noise while preserving the touch detection capability
2Productivity
If traditional sensing methods measure mean background screen responses for all drive lines, then complete coverage is achieved, but sensing time is wasted and resource utilization is inefficient
Solution Approach 1:
The patent segments the sensing process into two distinct phases: background sensing (performed once or infrequently) and touch sensing (performed continuously). By separating these functions and only performing background sensing when necessary, the system eliminates redundant measurements during normal operation, thereby improving sensing time efficiency and resource utilization
Solution Approach 2:
The patent performs background sensing as a preliminary action that establishes a baseline before normal touch sensing operations begin. This preliminary measurement of the mean background response is stored and reused for subsequent touch detections, eliminating the need to repeatedly measure background responses and thereby reducing sensing time waste
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 signal-to-noise ratio and optimizes sensing time by effectively removing mean background responses, improving touch detection accuracy and resource utilization.
Implementation Method 1
capacitive touch screen
Implementation Method 2
generating a plurality drive signals to respectively drive a plurality of drive lines
Data Source
AI summary
A method of detecting a user touch on a capacitive touch screen may include generating drive signals for drive lines of the capacitive touch screen. The drive signals are encoded by codes that respectively specify polarities of the drive signals at different times. The codes may include a background code that specifies the same polarity for the drive signals, and the remaining codes are orthogonal to the background code and specify that half of the drive signals have a first polarity and half of the drive signals have a second opposite polarity. The method includes measuring output signals at sensing lines of the capacitive touch screen, which include values corresponding to the codes for the drive signals, and decoding the output signals to determine a touch has occurred based on the values of the output signals, by excluding values corresponding to the background code.