Pen Signal Detection Using Phase Inversion to Cancel HSYNC Noise
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Solution Overview
Problem
High-resolution displays generate short horizontal synchronous pulses, leading to a decrease in the signal-to-noise ratio (S/N ratio) of pen signals due to the interruption of input to the reception circuit, making it difficult to accurately detect pen positions amidst HSYNC noise.
Innovation Solution
A detection method that sets two detection periods based on the noise generation cycle, where the pen signal is transmitted with inverted phases in each period, allowing the processor to acquire and cancel HSYNC noise while preserving the pen signal, thereby maintaining a high S/N ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the input to the reception circuit is interrupted at a timing synchronized with the horizontal synchronization pulse to reduce HSYNC noise influence, then the noise interference is reduced, but the period for detecting pen signal becomes extremely short causing decrease in S/N ratio
Solution Approach 1:
The patent applies periodic action by transmitting the pen signal in two detection periods with different phases (first detection period and second detection period). The pen signal is transmitted in synchronization with the first detection period, and then transmitted again with inverted phase in synchronization with the second detection period. This periodic transmission allows the reception circuit to accumulate signal energy over multiple periods while avoiding the HSYNC noise interruption problem, thereby maintaining high S/N ratio.
Solution Approach 2:
The patent converts the HSYNC noise problem into a benefit by using phase inversion technique. By transmitting the pen signal with inverted phase in the second detection period and combining it with the first detection period signal, the HSYNC noise components cancel each other out while the pen signal components are reinforced. This transforms the harmful noise into a useful cancellation mechanism that improves signal quality.
2Manufacturing precision
If the pen signal transmission period is shortened to accommodate high-resolution display with short horizontal synchronous pulse cycle, then the display resolution is improved, but the detection period for pen signal becomes too short reducing detection accuracy
Solution Approach 1:
The patent resolves this contradiction by using periodic action across multiple detection periods. Instead of relying on a single short detection period, the system transmits and detects the pen signal over multiple periods (first detection period and second detection period). This allows the system to maintain compatibility with high-resolution displays while accumulating sufficient signal energy for accurate detection, thereby preserving both display resolution and detection accuracy.
Solution Approach 2:
The patent applies preliminary action by preparing the detection system in advance for high-resolution display operation. The system is configured to perform detection over multiple periods before the actual pen signal transmission is needed, and the phase inversion technique is pre-established to ensure that when high-resolution display operation begins, the detection accuracy is already optimized.
Data Source
AI summary
A detection method of a pen signal that is an alternating current signal sent from a pen according to the present disclosure includes setting a first detection period and a second detection period that is the period after the first detection period ends based on a generation cycle of noise, transmitting to the pen an uplink signal requesting transmission of the pen signal in synchronization with the first detection period and transmission of the pen signal, whose phase is inverted with respect to the pen signal transmitted in synchronization with the first detection period, in synchronization with the second detection period, and acquiring the pen signal based on a first received signal received from the pen in the first detection period and a second received signal received from the pen in the second detection period.