Adaptive Stylus Receiver Narrowband Interference Suppression
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Solution Overview
Problem
Stylus receivers face challenges in decoding signals due to narrowband interference, which is not effectively suppressed by existing methods, leading to decreased signal-to-noise ratio and increased power consumption, and must comply with IEC61000-4-6 Level 2 compliance tests.
Innovation Solution
An adaptive stylus receiver is implemented, using an analog-to-digital converter, digital band pass filter, and frequency detection logic to digitize and process signals, estimating and suppressing narrowband interference with a narrowband notch filter, and increasing the pseudo noise sequence length without degrading performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the signal amplitude transmitted by the touchscreen is increased to overcome narrowband interference, then the signal-to-noise ratio improves, but the power consumption of the touchscreen panel increases
Solution Approach 1:
The patent extracts and removes the narrowband interference signal from the received signal using a notch filter tuned to the interference frequency. This allows the desired signal to be preserved without increasing transmission amplitude, thereby improving signal-to-noise ratio without increasing power consumption.
Solution Approach 2:
The patent changes the frequency domain characteristics of the received signal by applying adaptive filtering techniques. The system dynamically adjusts filter parameters (notch depth, bandwidth, center frequency) to match the interfering signal characteristics, effectively suppressing interference while maintaining the original signal amplitude and power consumption levels.
2Reliability
If the number of chips in the pseudo noise sequence is increased to improve signal-to-noise ratio, then the decoding reliability improves, but the power consumption and silicon area of the correlation receiver increase
Solution Approach 1:
The patent removes narrowband interference before the correlation decoding process using a notch filter. This preprocessing step eliminates the need to increase PN sequence length for interference rejection, thereby maintaining decoding reliability without increasing power consumption or silicon area of the correlation receiver.
Solution Approach 2:
The patent performs interference suppression as a preliminary action before the main correlation decoding operation. By removing the narrowband interference component prior to correlation, the system ensures that the correlation receiver operates on a cleaner signal, maintaining reliability without requiring additional processing resources.
3Object-affected harmful factors
If a fixed notch filter is used to suppress narrowband interference, then the interference rejection works for known frequencies, but the system cannot adapt to varying interference frequencies and fails compliance tests
Solution Approach 1:
The patent implements a dynamic notch filter whose center frequency, bandwidth, and depth parameters are continuously adjusted based on the detected interference characteristics. The system monitors the frequency spectrum and adapts the filter parameters in real-time to track varying interference frequencies, ensuring effective rejection across different operating conditions and compliance with IEC61000-4-6 Level 2 tests.
Solution Approach 2:
The patent employs a feedback mechanism where the received signal is analyzed to detect narrowband interference components, and this information is fed back to adjust the notch filter parameters. The system continuously monitors signal quality and adapts the filter configuration to maintain optimal interference rejection performance under varying conditions.
Data Source
AI summary
Disclosed is an adaptive stylus receiver to adaptively determine presence of narrowband interference. The receiver comprises an analog-to-digital converter to digitize an incoming digitally modulated (DM) signal at a predetermined sampling frequency, a digital band pass filter configured to receive digitized DM signal and to generate a first set of frequencies from the digitized DM signal, and a frequency detection logic to adaptively determine presence of narrowband interference in a first set of frequencies, the frequency detection logic configured to estimate frequency components from the first set of frequencies, provide a first set of coefficients to a narrowband notch filter, binning of coefficients for frequencies below a threshold value, adaptively estimate narrowband notch filter coefficients by binning and provide estimated narrowband notch filter coefficients to the narrowband notch filter to suppress the narrow band interference from the first set of frequencies.