Digitizer Noise Reduction via Multi-Frequency Signal Sampling
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Solution Overview
Problem
Existing digitizer systems face challenges in accurately detecting electromagnetic styluses due to noise interference, particularly from user fingers, which can induce signals at the same frequency as the stylus, leading to erroneous detection and positioning issues.
Innovation Solution
A method and apparatus for noise reduction in digitizers that involve sampling multiple detecting elements simultaneously and reducing noise by determining a ratio between signals at a predetermined frequency and an arbitrary frequency, allowing for the identification and subtraction of noise from the stylus signal, using a candidate carrier of mere noise to correct signal outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If band pass filter and Fourier transform are used to process the received signal, then noise at frequencies other than stylus frequency is removed, but noise at the same frequency as the stylus cannot be eliminated
Solution Approach 1:
The patent segments the signal processing into multiple frequency components by sampling at least two different frequencies. By dividing the signal into frequency components and processing them separately, the system can identify and remove noise at the stylus frequency while preserving the actual stylus signal.
Solution Approach 2:
The patent changes the sampling frequency parameter to at least two different frequencies. By varying the frequency parameter and comparing the results, the system can distinguish between noise and actual signal, enabling removal of noise at the stylus frequency that cannot be eliminated by fixed-frequency filtering alone.
2Object-affected harmful factors
If differential amplifiers are used to eliminate common noise on all conductive lines, then noise from distant objects is removed, but noise specific to individual lines or the stylus frequency remains
Solution Approach 1:
The patent introduces an intermediary processing step that samples signals at multiple frequencies and uses ratio calculation as a mediator to distinguish between noise and signal. This intermediary frequency-domain analysis enables more precise noise removal than direct time-domain differential amplification alone.
3Object-affected harmful factors
If multiple detecting elements are sampled simultaneously, then noise can be identified and subtracted, but the system complexity increases
Solution Approach 1:
The patent makes the sampling system universal by using the same detecting elements and sampling circuitry for multiple frequencies. This multi-functional approach allows noise reduction without proportionally increasing hardware complexity, as the same components serve multiple frequency sampling purposes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively eliminates noise at the stylus frequency, improving the accuracy of stylus detection and positioning by distinguishing between stylus signals and noise, even when noise levels are stronger or weaker than the stylus signal.
Implementation Method 1
External excitation coils that surround the sensor are utilized to energize the stylus
Implementation Method 2
a plurality of detecting elements for detecting an electromagnetic signal at one of a number of predetermined frequencies
Data Source
AI summary
A method for noise reduction in a digitizer, the digitizer comprising a plurality of detecting elements for detecting an electromagnetic signal at one of a number of predetermined frequencies: the method comprising: sampling at least two of said detecting elements substantially simultaneously to obtain outputs therefrom, and reducing the output on one of said two elements in accordance with the output on the other of said elements.