Surface Acoustic Wave Touch Panel Signal Segmentation
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Solution Overview
Problem
Large-size surface acoustic wave (SAW) touch panels face challenges in accurately detecting touch positions due to signal attenuation over long propagation distances, leading to weak signals that are difficult to distinguish from noise.
Innovation Solution
The method involves segmenting SAW signals multiple times and amplifying them differentially to construct a complete output electrical signal, with a two-stage detection process to enhance signal strength and accuracy, using a reflector array and control circuit to generate and process SAW segments and output electrical signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the SAW touch panel size is increased, then the detection area is expanded, but the SAW signal attenuation increases making touch detection difficult
Solution Approach 1:
The patent divides the large SAW touch panel into multiple detection regions, each equipped with its own transducer elements and reflection units. This segmentation allows each region to independently generate and detect SAW signals, preventing signal attenuation from affecting the entire panel. The control circuit processes signals from multiple segments to determine touch positions across the expanded detection area.
Solution Approach 2:
The patent implements different densities of reflection units in different regions of the SAW touch panel. Reflection units are arranged with higher density in regions where signal attenuation is more severe, and lower density where signals remain stronger. This local quality adjustment optimizes signal reception across the entire large panel while maintaining accurate touch detection in each specific region.
2Device complexity
If reflection units are evenly arranged, then the structure is simple, but SAW signals available for reflection decrease affecting detection accuracy
Solution Approach 1:
The patent employs asymmetric arrangement of reflection units, where the density and distribution of reflectors vary across different regions of the SAW touch panel. This asymmetric configuration optimizes the reflection of SAW signals in each specific region, ensuring sufficient signal availability for accurate touch position detection while adapting to the local signal attenuation characteristics of each area.
Solution Approach 2:
The patent adjusts the density parameter of reflection units across different regions of the SAW touch panel. By varying the density from sparse in certain areas to dense in others, the system optimizes signal reflection and reception characteristics. This parameter change enables the panel to maintain detection accuracy across the entire large surface while managing the complexity of the reflection unit arrangement.
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 significantly increases the size of detectable SAW touch panels by adaptively maintaining signal strength within a predefined range, allowing for more accurate detection of touch positions beyond previous limitations.
Implementation Method 1
It converts an electrical signal to the SAW signal by using a transducer including a piezoelectric material
Implementation Method 2
These reflectors r are all partially transmissive and partially reflective. Meanwhile, the SAW signals Signal_V1 and Signal_V2 necessary for sensing a possible touch point P input on each horizontal axis and vertical axis are provided by this partially transmissive and partially reflective effect of the reflectors r
Data Source
AI summary
The present invention provides a method and device for position detection. For detection of a touch position, a segment of surface acoustic wave (SAW) is provided multiple times to be propagated on a SAW touch panel, and the multiple SAW segments are received by the SAW touch panel. In addition, during or after reception, partial output electrical signals are provided based on different portions of each received SAW segment to construct a complete output electrical signal.