Predictive ADC Signal Processing for Stylus Noise Rejection
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Solution Overview
Problem
Conventional signal processing devices face challenges in reducing noise interference in reception signals from electromagnetic styluses, leading to decreased accuracy in position detection due to the need for higher-order filters, which increase chip area and hardware burden.
Innovation Solution
A signal processing device comprising an AD converter, memory, prediction logic circuit, error amount detection circuit, and selector, which predicts signal values based on past data and determines error levels to select either the original or predicted value for output, reducing noise impact without increasing chip area or hardware burden.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If higher-order filters are used to reduce noise, then noise reduction effect is improved, but chip area increases in analog filters and hardware burden increases in digital filters
Solution Approach 1:
The patent replaces the mechanical filter system (analog or digital filters requiring high sampling rates) with a prediction-based signal processing system. The AD converter samples at a lower frequency, and a prediction circuit reconstructs the original signal by predicting future sample values based on past samples, eliminating the need for complex filtering hardware while achieving noise reduction
Solution Approach 2:
The patent changes the sampling frequency parameter from high (required by filters) to low (sufficient for prediction). By using prediction algorithms that work with lower sampling rates, the system achieves noise reduction without requiring high sampling frequencies, thereby reducing chip area and hardware burden
2Object-affected harmful factors
If higher-order filters are used to reduce noise, then noise reduction effect is improved, but hardware burden increases due to higher sampling rate processing
Solution Approach 1:
The patent substitutes the complex filter processing system with a prediction-based system. Instead of using high-order digital filters that require extensive computational resources and high sampling rates, the system uses a prediction circuit that reconstructs signals from sparsely sampled data, significantly reducing hardware complexity and processing burden
Solution Approach 2:
The patent extracts only the essential signal information at low sampling rates and uses prediction to reconstruct the full signal. This approach removes the unnecessary complexity of high-rate sampling and filtering, keeping only the minimal hardware needed for prediction-based signal reconstruction
Data Source
AI summary
According to embodiments, a signal processing device includes an AD converter, a memory, a prediction logic circuit, an error amount detection circuit, and a selector. The AD converter converts an input signal to an AD conversion value at a certain sampling frequency. The memory stores an AD conversion output result. The prediction logic circuit predicts a prediction value by using the AD conversion output result at the sampling frequency. The error amount detection circuit determines that there is no error in error determination of the AD conversion value when an error amount between the prediction value and the AD conversion value is smaller than a predetermined amount, and that there is an error in the error determination when the error amount is equal to or larger than the predetermined amount. The selector outputs one of the AD conversion value and the prediction value as an AD conversion output result, on the basis of the error determination.