Multi-Stimulus Touch Demodulation With Phase Compensation Matrix
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Solution Overview
Problem
Conventional multi-stimulus touch controllers face inefficiencies due to phase delays in sense signals caused by varying signal path lengths, making it difficult to accurately process composite sense signals.
Innovation Solution
A single-chip multi-touch controller is developed, incorporating a transmit oscillator, transmit and receive channels, and a demodulation section with a vector operator to generate and process drive signals, allowing for phase compensation of sense signals through a phase-compensated decode matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple drive lines are stimulated simultaneously to generate composite sense signals, then system efficiency is improved, but phase delays in sense signals are introduced due to varying signal path lengths
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing phase compensation values for each drive line in a lookup table before actual touch sensing operations. During sensing, the appropriate phase compensation value is retrieved and applied to the sense signal based on which drive lines are active, eliminating the need for real-time phase calculation and maintaining both high efficiency and measurement precision.
2Measurement precision
If phase compensation is applied to each drive line, then measurement precision of sense signals is improved, but device complexity increases
Solution Approach 1:
The patent changes the parameter approach by representing phase compensation as discrete lookup table entries indexed by drive line combinations rather than implementing continuous phase adjustment circuitry. This allows precise phase compensation through simple table lookups and bitwise operations, avoiding complex analog phase shifters or real-time digital signal processing while maintaining measurement precision.
3Ease of manufacture
If conventional multi-stim systems are used, then ease of manufacture is maintained, but processing efficiency of composite sense signals deteriorates
Solution Approach 1:
The patent substitutes mechanical signal processing approaches with digital processing methods. Instead of using complex analog phase alignment circuits or mechanical delay lines, the invention uses digital lookup tables and bitwise operations to achieve phase compensation, maintaining ease of manufacture with standard digital logic while dramatically improving sense signal processing efficiency.
Data Source
AI summary
Determining a compensated phase matrix for a multi-stimulus demodulation process is provided. A first drive line of a multi-stimulus sensing system is selected, and a stimulation signal is transmitted on the selected drive line. A channel gain resulting from the stimulation signal is measured from a received sense signal resulting from the stimulation signal. The measured channel gain is compared with a known channel gain to obtain an individual phase compensation for the selected drive line. A compensated phase matrix is formed of the individual phase compensation values for multiple drive lines.