Resonant Pen Circuit Switching for Continuous Position Detection
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Solution Overview
Problem
Existing electromagnetic induction pens for position detection on tablet terminals face challenges in maintaining position detection frequency while transmitting digital values, as they require separate periods for position detection and digital value transmission, and suffer from signal-to-noise ratio degradation due to display noise.
Innovation Solution
A position indicator with a resonance circuit and control circuit that switches between two states with different resonance frequencies, allowing continuous transmission of digital values without interrupting position detection, and adjusts resonance frequency to avoid overlap with display noise frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the electromagnetic induction pen uses on-off-keying to transmit digital values, then digital value transmission is achieved, but the position detection frequency is reduced because separate periods are required for position detection and digital value transmission
Solution Approach 1:
The patent combines position detection and digital value transmission into a single continuous alternating magnetic field transmission period. The position detecting device detects position information continuously while the pen transmits digital values through frequency modulation, eliminating the need for separate time periods and thereby maintaining high position detection frequency while achieving digital value transmission.
Solution Approach 2:
The patent employs frequency modulation where the resonance frequency of the pen's coil is dynamically changed according to digital values to be transmitted. This allows the pen to convey information through frequency variations within the continuous alternating magnetic field, enabling simultaneous position detection and data transmission without interrupting the detection process.
2Device complexity
If the resonance frequency of the pen overlaps with the frequency of display noise, then the structure is simple, but the signal-to-noise ratio of the alternating magnetic field deteriorates
Solution Approach 1:
The patent changes the resonance frequency parameter of the pen's coil to a value that does not overlap with the display noise frequency. By adjusting this physical parameter, the system achieves frequency separation between the useful signal and noise, thereby improving the signal-to-noise ratio while maintaining the simplicity of the resonance circuit structure.
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
Enables continuous position detection during digital value transmission and improves signal-to-noise ratio by avoiding frequency overlap with display noise, enhancing the efficiency and accuracy of position detection.
Implementation Method 1
The position detecting device has a function of transmitting an alternating magnetic field through the panel surface by causing a flow of an alternating current to flow in at least one of the loop coils
Implementation Method 2
When a coil included in the electromagnetic induction pen enters the alternating magnetic field, an electromotive force is excited in the coil as a result of electromagnetic induction
Implementation Method 3
When the position detecting device stops transmitting the alternating magnetic field, an electric charge stored in the capacitor generates a current flow in the coil. As a result, an alternating magnetic field is transmitted from the electromagnetic induction pen
Data Source
AI summary
Provided is a position indicator including a resonance circuit including a coil, and a control circuit including a memory that stores a digital value. The control circuit further includes a switch that switches a state of the resonance circuit between a first state and a second state which are different in resonance frequencies from each other, and, at a timing when an alternating magnetic field transmitted from a position detecting device is received, the control circuit controls the switch to set the resonance circuit to the first state, and, at a timing when a digital value stored in the memory is transmitted, the control circuit controls the switch in accordance with the digital value to be transmitted.