Touch Sensing Receiving Circuit with Frequency-Division Demodulation
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Solution Overview
Problem
Existing touch sensing technologies in devices like smartphones and tablets face challenges in providing good touch sensing performance while sharing a touch electrode and receiving circuit, often resulting in higher costs or increased response times, especially when distinguishing between finger and active pen inputs.
Innovation Solution
The implementation of a receiving circuit with multiple demodulators and analog to digital converters operating at different frequencies to process touch signals from a shared touch electrode, allowing simultaneous detection of finger and active pen inputs without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two touch electrodes are disposed for sensing finger and active pen separately, then touch sensing performance is improved, but device cost increases
Solution Approach 1:
The patent applies periodic action by using different frequencies for finger touch and active pen touch signals. The finger touch signal is modulated at a first frequency while the active pen touch signal is modulated at a second frequency, allowing the receiving circuit to distinguish between different touch types through frequency differentiation. This enables a single touch electrode to detect multiple touch types simultaneously without interference.
2Device complexity
If one touch electrode is disposed and time-division processing is used, then device cost is reduced, but response time increases
Solution Approach 1:
The patent uses periodic action with frequency division instead of time-division multiplexing. By assigning different frequencies to different touch types (finger touch at first frequency, active pen touch at second frequency), the system can process multiple touch signals simultaneously in parallel, eliminating the time delays inherent in sequential time-division processing while still using a single shared touch electrode.
3Device complexity
If one touch electrode is shared for both finger and active pen sensing, then device complexity is reduced, but signal interference occurs
Solution Approach 1:
The patent resolves signal interference by implementing frequency-division multiplexing where finger touch signals are modulated at a first frequency and active pen touch signals are modulated at a second frequency. The receiving circuit includes demodulators tuned to these specific frequencies, allowing it to selectively extract and process each touch type's signal from the combined input without interference, even though both signals are received through the same touch electrode.
Data Source
AI summary
An electrical device is provided and includes a touch electrode and a receiving circuit. The receiving circuit includes a first demodulator, a first analog to digital converter, a second demodulator, and a second analog to digital converter. The first demodulator is coupled to the touch electrode and demodulates a touch signal received from the touch electrode according to a first frequency to generate a first analog signal. The first analog to digital converter is coupled to the first demodulator and converts the first analog signal into a first digital signal. The second demodulator is coupled to the touch electrode and demodulates the touch signal according to a second frequency to generate a second analog signal. The second frequency is different from the first frequency. The second analog to digital converter is coupled to the second demodulator and converts the second analog signal into a second digital signal.