Active Pen Frequency Division for Common Symbol Timing
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Solution Overview
Problem
Existing position detecting systems face complex computation for phase acquisition and unequal unused time in time slots when using frequency dividing circuits for generating downlink signals with different frequencies, leading to inefficient utilization.
Innovation Solution
An active pen and sensor integrated circuit that uses a frequency dividing circuit to generate carrier waves with orthogonal frequencies, ensuring equal symbol durations and reducing unused time differences, allowing simultaneous transmission of downlink signals without complex phase acquisition computations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If frequency dividing circuits are used to generate carrier waves with different frequencies for simultaneous transmission by multiple active pens, then the configuration becomes simple, but the symbol durations differ between frequencies causing complex phase acquisition computation
Solution Approach 1:
The patent changes the frequency parameter of carrier waves while maintaining a common symbol duration. By carefully selecting frequencies (500 kHz, 333.3 kHz, 250 kHz) that are integer divisors of a reference frequency (1 MHz) and ensuring their periods divide evenly into the symbol duration (10 μsec), the system achieves both simple frequency division and uniform symbol timing, eliminating complex phase acquisition computations.
2Adaptability or versatility
If different frequencies are assigned to multiple active pens for simultaneous transmission, then simultaneous input is enabled, but unused time in time slots becomes unequal leading to inefficient time utilization
Solution Approach 1:
The patent optimizes the frequency parameter selection to ensure that the number of symbols transmitted by each active pen within a time slot is equal. By choosing frequencies where 500 kHz transmits 10 symbols, 333.3 kHz transmits 10 symbols, and 250 kHz transmits 10 symbols in a 100 μsec time slot, the system achieves equal time utilization without wasted periods, enabling efficient simultaneous input from multiple pens.
3Object-affected harmful factors
If symbol duration is set to integer multiple of pulse signal period to avoid harmonic noise, then transmission quality improves, but symbol durations differ between frequencies causing unequal time utilization
Solution Approach 1:
The patent carefully selects frequency parameters (500 kHz, 333.3 kHz, 250 kHz) that satisfy two conditions simultaneously: (1) each frequency is an integer divisor of the reference frequency to avoid harmonic noise, and (2) the period of each frequency divides evenly into the common symbol duration (10 μsec). This ensures equal time utilization across all frequencies while maintaining transmission quality.
Data Source
AI summary
An active pen is provided, which facilitates avoiding complex computation for phase acquisition on the side of a sensor integrated circuit configured to receive downlink signals from active pens, and allows for generating carrier waves for the downlink signals using a simple configuration, namely, a frequency dividing circuit, while reducing a difference in unused time in one time slot between the active pens. An active pen 2 is configured to transmit one or more symbol values in one time slot, and includes a frequency dividing circuit 43 configured to frequency-divide a reference clock with a frequency division ratio based on each of a plurality of frequencies different from each other, to thereby generate a plurality of carrier waves having frequencies different from each other. The active pen 2 includes a modulation (transmission) circuit 44 configured to transmit a first downlink signal in a symbol duration that is common among the plurality of frequencies, the first downlink signal obtained by modulating a first carrier wave, which is among the plurality of carrier waves generated by the frequency dividing circuit 43, with a value of a first symbol that is a transmission target.