Golay Sequence Digitizer Touch Sensing
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Solution Overview
Problem
Current multi-touch detection methods for capacitive digitizer systems are inefficient due to the need for sequential triggering of grid lines and the requirement for dedicated correlators for orthogonal frequencies, which limits performance and increases computational complexity.
Innovation Solution
The method employs a Golay pair of sequences, transmitted on multiple driver lines with different phase shifts and delays, allowing for simultaneous triggering and separation of responses using a single correlator, enhancing noise immunity and resolution through time domain multiplexing and encoding on carrier signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sequential triggering of grid lines is used for multi-touch detection, then touch detection capability is achieved, but detection speed and refresh rate are limited
Solution Approach 1:
The patent applies preliminary action by pre-transmitting Golay pair sequences on all driver lines before actual touch detection. The sequences are encoded with orthogonal frequencies and transmitted in advance, so when touches occur, the system can immediately process the pre-configured signal structure without sequential setup delays, thereby improving detection speed.
Solution Approach 2:
The patent implements periodic action through the use of Golay pair sequences transmitted at regular intervals with specific time delays. The sequences are transmitted periodically on different driver lines with orthogonal frequency encoding, allowing the system to maintain continuous detection capability while reducing the time loss associated with sequential triggering through structured periodic transmission patterns.
2Measurement precision
If dedicated correlators for orthogonal frequencies are used, then frequency separation is achieved, but device complexity and computational requirements increase
Solution Approach 1:
The patent applies merging by combining multiple correlator functions into a single correlator that can process multiple orthogonal frequencies simultaneously. The Golay pair sequences are encoded with orthogonal frequencies and transmitted with specific time delays, allowing one correlator to separate and identify signals from multiple driver lines by detecting the characteristic time delay patterns, thereby reducing device complexity while maintaining frequency separation accuracy.
Solution Approach 2:
The patent implements universality by designing a single correlator that performs multiple functions: it processes signals from different driver lines, separates orthogonal frequencies, and identifies touch locations. The correlator is designed to handle the Golay pair sequence structure with time delays, making it a universal processor that eliminates the need for dedicated correlators for each frequency or driver line, thus reducing computational requirements.
3Reliability
If Golay pair sequences with time domain multiplexing are used, then signal-to-noise ratio is enhanced, but transmission time increases
Solution Approach 1:
The patent applies periodic action by transmitting Golay pair sequences in structured time intervals with specific delays between different driver lines. The sequences are transmitted periodically rather than continuously, allowing the system to achieve enhanced signal-to-noise ratio through the coherent integration of correlated signals while controlling transmission time through the periodic nature of the sequence transmission pattern.
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 improves multi-touch detection accuracy and refresh rate by clearly identifying responses from each driver line, reducing dynamic range and enhancing signal-to-noise ratio, while allowing for simultaneous triggering of multiple lines, thus overcoming limitations of existing methods.
Implementation Method 1
Input to the digitizer sensor includes one or more of electromagnetic (EM) transmission from the stylus touching the sensing surface and capacitive coupling due to a conductive object such as a finger touching the screen
Implementation Method 2
Input to the digitizer sensor includes one or more of electromagnetic (EM) transmission from the stylus touching the sensing surface
Data Source
AI summary
A method for multi-touch detection on a grid based capacitive sensor includes transmitting consecutively a first and then a second sequence of a Golay pair of sequences on a first driver line of a grid based capacitive sensor and transmitting the first and then the second sequence of a Golay pair of sequences on a second driver line, at a predefined delay with respect to transmission on the first driver line. Output on a receiver line of the grid based capacitive sensor is sampled and output originating from the first driver line is separated from output originating from the second driver line. The presence of an input object is detected responsive to the output as separated.