Stylus Position Signaling Using Cyclic Shift Spread Codes
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Solution Overview
Problem
Existing communication methods between a position indicator and a position detector, such as those using direct spread techniques, face challenges in achieving high bit rates due to the requirement of multiple chips to express one bit, making it difficult to increase the chip rate.
Innovation Solution
A sensor controller and position indicator system that utilizes cyclic shifting of a code string to generate a chip string, allowing for the expression of 2 bits or more with one code string, thereby achieving a high bit rate at the same chip rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct spread technique is used for communication between position indicator and detector, then noise resistance is improved, but bit rate deteriorates due to requiring multiple chips to express one bit
Solution Approach 1:
The patent changes the encoding parameter from using multiple chips per bit (direct spread) to using cyclic shift quantities of a single code string to represent multiple bits. This parameter change allows achieving high bit rates while maintaining noise resistance through the autocorrelation properties of the code string.
Solution Approach 2:
The code string serves multiple functions: it provides noise resistance through autocorrelation characteristics while simultaneously encoding multiple bits through cyclic shifting. This multi-functionality resolves the contradiction between reliability and productivity.
2Reliability
If multiple chips are used to express one bit in direct spread technique, then noise resistance is improved, but chip rate increase becomes difficult
Solution Approach 1:
The patent changes the fundamental parameter from chip-based encoding to shift-quantity-based encoding. By representing multiple bits through the shift quantity of a single code string rather than through multiple chips, the system achieves high bit rates without requiring increased chip rates.
Solution Approach 2:
The patent transitions from encoding information in the time dimension (multiple chips) to encoding information in the shift quantity dimension. This dimensional change allows achieving high information density without increasing the chip rate.
3Productivity
If cyclic shifting of code string is used to generate chip string, then bit rate is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex multi-chip encoding mechanisms with a simpler cyclic shifting operation on a single code string. This substitution reduces device complexity while maintaining high bit rate performance through the mathematical properties of cyclic shifts.
Data Source
AI summary
A stylus includes an integrated circuit, wherein the integrated circuit is configured to perform receiving, from a sensor controller of a position detector, a preamble signal generated by modulating a chip string with a defined code pattern of the preamble signal. After receiving the preamble signal, the integrated circuit performs receiving, from the sensor controller, a command signal generated by modulating a second chip string with data. The integrated circuit, by referring to a polarity of the preamble signal, decodes the data based on the command signal. The integrated circuit controls, based on the data, transmission of a signal to the position detector.