Noise Reduction Circuit for Touch Systems
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Solution Overview
Problem
Touch systems, such as capacitive touch screens, face interference issues due to noise signals that limit the linearity and dynamic range of the receive chain, affecting the accuracy of touch gesture detection.
Innovation Solution
A noise reduction circuit that samples the touch signal to detect noise, generates a reduction signal, and feeds it back to the input stage of the receiver to mitigate noise interference, using a combination of high pass filters, gain circuits, and delay circuits to isolate and adjust the noise signal based on measured noise energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If noise reduction circuit is added to mitigate interference, then signal-to-interference plus noise ratio is improved, but device complexity increases
Solution Approach 1:
A noise reduction circuit is introduced as an intermediary component between the touch sensor and the receiver. This circuit includes a high pass filter to isolate noise signals, a gain circuit to amplify the isolated noise, and a delay circuit to synchronize the noise signal with the touch signal. The processed noise signal is then subtracted from the received touch signal to mitigate interference and improve the signal-to-interference plus noise ratio.
Solution Approach 2:
The noise reduction circuit segments the signal processing into distinct functional stages: noise isolation through high pass filtering, noise amplification through gain circuit, timing synchronization through delay circuit, and interference cancellation through signal subtraction. This segmentation allows each component to be optimized independently while working together to reduce overall interference.
2Object-affected harmful factors
If noise signal is isolated and amplified, then noise interference is reduced, but circuit complexity increases
Solution Approach 1:
The high pass filter acts as an intermediary that selectively isolates noise signals from the composite signal containing both touch and noise components. By filtering based on frequency characteristics, the circuit separates the harmful noise component without affecting the useful touch signal, enabling targeted noise reduction.
Solution Approach 2:
The noise reduction circuit employs feedback mechanisms where the isolated and amplified noise signal is fed back through the delay circuit and then subtracted from the original received signal. This feedback loop continuously adjusts and cancels the noise interference, improving the overall signal quality dynamically.
Data Source
AI summary
A circuit includes a receiver that includes an input stage to receive a touch signal from a touch system. A noise reduction circuit that samples the touch signal to detect a noise signal in the touch signal. The noise reduction circuit generates a reduction signal based on the noise signal that is fed back to the input stage of the receiver to mitigate noise interference of the noise signal with respect to the touch signal at the receiver.