Touch Sensing Apparatus With Dynamic Frequency Band Adjustment

The patent implements dynamic frequency band adjustment by making the cut-off frequencies of the high-pass and low-pass filters variable rather than fixed. The high-pass filter's cut-off frequency is adjusted based on touch position to pass different frequency components from different nodes, while the low-pass filter dynamically adjusts its cut-off frequency to maintain optimal noise filtering. This dynamic adaptation allows the system to accurately distinguish touch signals from noise across various touch positions without requiring a completely different circuit for each position.

The patent changes the frequency parameters of the filtering circuits to adapt to different touch positions. By varying the cut-off frequencies of the high-pass and low-pass filters based on the detected touch position, the system optimizes the frequency band for signal detection at each specific location. This parameter adjustment enables the same physical circuit to perform optimally across different spatial positions on the touch panel.

The patent applies different filtering characteristics to different frequency components based on their local properties. The high-pass filter selectively removes low-frequency noise while preserving higher-frequency touch signals, and the low-pass filter removes high-frequency noise while preserving lower-frequency useful signals. By combining these two filters with dynamically adjusted cut-off frequencies, the system creates a band-pass effect that locally optimizes the frequency response for different touch positions, removing harmful noise components while preserving useful signal components.

The system uses feedback from the detected touch position to adjust the filtering parameters. The touch position detection information is fed back to control the cut-off frequencies of the high-pass and low-pass filters, creating a closed-loop system that adapts the noise filtering characteristics based on the current operating conditions. This feedback mechanism ensures that the filtering always optimizes the signal-to-noise ratio for the specific touch position being detected.

The patent implements preliminary timing arrangement by setting the sampling period to start after a predetermined time from the transition time point of the driving signal. This preliminary timing ensures that the sampling occurs during the stable period of the driving signal, avoiding the transient period when load effects are strongest. By pre-calculating and setting this time offset, the system proactively eliminates load influence before sampling occurs, rather than attempting to correct it afterward.

The system uses periodic sampling synchronized with the periodic driving signal. The sampling operation is performed at regular intervals that are synchronized with the driving signal period, specifically at the optimal point in each cycle when the load influence is minimized. This periodic synchronization ensures that every sampling operation benefits from the same optimal timing conditions, consistently reducing load influence across all sampling cycles.