Touch Sensor Frequency Scanning to Mitigate Harmonic Aliasing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing touch sensor devices face interference issues due to the emission of higher harmonics when using non-sinusoidal transmitter signals, which can lead to aliasing artifacts that affect the accuracy of touch sensing operations, particularly in larger sensing regions where simultaneous driving of multiple electrodes is necessary to maintain high frame rates.
Innovation Solution
The use of non-sinusoidal transmitter signals with unique base frequencies and an analog-to-digital converter (ADC) sampling frequency is selected to locate aliasing artifacts at frequencies different from the base frequencies, thereby mitigating inter-band interference and maintaining high frame rates for touch sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-sinusoidal transmitter signals are used for simultaneous driving of multiple electrodes, then productivity (frame rate) is improved, but object-generated harmful factors (aliasing artifacts from higher harmonics) worsen
Solution Approach 1:
The patent changes the parameter of transmitter signal waveform from sinusoidal to non-sinusoidal (e.g., square wave, triangle wave) to enable simultaneous driving of multiple electrodes at different frequencies, thereby improving frame rate. This parameter change introduces higher harmonics but allows for frequency separation techniques to manage the resulting aliasing artifacts.
Solution Approach 2:
The patent segments the frequency spectrum into multiple bands, assigning different frequency ranges to different transmitter electrodes. By segmenting the operation into frequency regions rather than time regions, multiple electrodes can be driven simultaneously without their signals interfering with each other, thus maintaining high frame rates while managing harmonic content.
2Productivity
If multiple transmitter electrodes are driven simultaneously to maintain high frame rates, then productivity is improved, but object-affected harmful factors (interference between transmitter signals) worsen
Solution Approach 1:
The frequency spectrum is segmented into distinct bands, with each transmitter electrode assigned a unique frequency or frequency range. This segmentation in the frequency domain allows simultaneous operation of multiple electrodes without temporal interference, as each electrode's signal occupies a separate spectral region that can be independently processed.
Solution Approach 2:
The patent transitions from time-domain multiplexing (sequential driving of electrodes) to frequency-domain multiplexing (simultaneous driving at different frequencies). This dimensional change from time to frequency allows parallel operation of multiple electrodes, improving frame rate while managing interference through frequency separation and signal processing techniques.
Data Source
AI summary
A method for operating an input device, the method involving obtaining a number of non-sinusoidal transmitter signals with unique base frequencies, and selecting a sampling frequency of an analog-to-digital converter (ADC) such that a number of aliasing artifacts associated with higher harmonics of the non-sinusoidal transmitter signals is located at frequencies different from the base frequencies.