Position detector, integrated circuit and position detection method

Abstract

To suppress attenuation of the amplitude of a pen signal obtained from an electric circuit of a position indicator.SOLUTION: A position indicator includes: a coil 104 which includes a transmission coil 104a configured to function as a sensor and transmit an alternating magnetic field based on a TX signal (transmission signal) to a position indicator 2; and a signal processing circuit 102 which is connected to the coil 104, detects a RX signal (pen signal) generated by the position indicator 2, generates the TX signal with a frequency according to frequency information of the detected RX signal, and transmits the TX signal to the transmission coil 104a.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a position detector, an integrated circuit, and a position detection method. [Background technology]

[0002] 2. Description of the Related Art In recent years, input devices other than a mouse or the like have come to be used as input devices for personal computers, tablet terminals, and the like. This type of input device is composed of, for example, a pen-shaped position indicator and a position detection device having an input area where the position indicator is used to perform pointing operations and input characters, figures, etc.

[0003] The position indicator also includes an electrical circuit for detecting the pen pressure. The electrical circuit for detecting the pen pressure in the position indicator is configured, for example as described in Patent Document 1, as a resonant circuit consisting of a position indication coil and a resonant capacitor, with a variable capacitor connected in parallel to the resonant capacitor. The variable capacitor is made of a rod-shaped member, one end of which is attached to the other end of a core body that serves as a pointing portion that functions as the pen tip. The electrical circuit for detecting the pen pressure in the position indicator utilizes the characteristics of a variable capacitor, whose capacitance value changes when pen pressure is applied to the pointing portion, to output the change in pen pressure as a change in resonant frequency output from the electrical circuit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5534419 Summary of the Invention [Problem to be solved by the invention]

[0005] The position detection device detects a change in the resonance frequency output from an electric circuit of the position indicator as a phase difference. Therefore, in conventional position detection devices, the pen pressure of a position indicator could be detected using only a signal generator consisting of an oscillator that generates a transmission signal of a predetermined single frequency and a current driver, and a synchronous detection circuit that detects the change in frequency of the pen signal detected using the signal of that frequency supplied from the oscillator relative to the transmission signal as a change in phase.

[0006] Here, when no pen pressure is applied to the pointing portion of the position indicator, a pen signal with a large amplitude can be obtained from the electrical circuit of the position indicator by matching the resonant frequency output from the electrical circuit of the position indicator with the single frequency generated in the position detection device (see Figures 14 and 15(B)).

[0007] However, when pen pressure is applied to the pointing portion of the position indicator, the resonant frequency of the pen signal output from the electrical circuit of the position indicator changes, and the resonant frequency output from the electrical circuit of the position indicator and the single frequency generated in the position detection device no longer match (see Figure 15(A)).

[0008] That is, when a writing pressure is applied to the pointing portion of the position indicator, a phenomenon occurs in which the amplitude of the pen signal obtained from the electric circuit of the position indicator is attenuated (see FIG. 15(B)). In addition, the position detector generates a transmission signal of a single frequency for a certain period of time (the "TX period" in Figure 15(B)), and then detects the resonant frequency of the pen signal output from the electrical circuit of the position indicator during the period during which the generation of the transmission signal of the single frequency is stopped (the "RX period" in Figure 15(B)). Therefore, when the position detector detects the resonance frequency of the pen signal, the detection process for the resonance frequency of the pen signal is executed in a state where the degree of attenuation of the amplitude of the pen signal has further increased.

[0009] As described above, in the technology described in Patent Document 1 etc., when pen pressure is applied to the pointing portion of the position indicator, the amplitude of the pen signal obtained from the electrical circuit of the position indicator attenuates, thereby decreasing the S / N ratio of the pen signal obtained from the electrical circuit of the position indicator, which may result in a decrease in the position detection accuracy of the position indicator and a decrease in the detection accuracy of the pen pressure.

[0010] Therefore, the present invention has been made in consideration of the above-mentioned problems, and aims to provide a position detector, an integrated circuit, and a position detection method that suppresses attenuation of the amplitude of the pen signal obtained from the electrical circuit of the position indicator. [Means for solving the problem]

[0011] Form 1: One or more embodiments of the present invention propose a position detector including a coil configured to function as a sensor, the coil including a transmission coil that transmits an alternating magnetic field based on a transmission signal to a position indicator, and a signal processing circuit connected to the coil, detects a pen signal generated by the position indicator, generates the transmission signal having a frequency based on frequency information of the detected pen signal, and transmits it to the transmission coil.

[0012] Form 2: One or more embodiments of the present invention propose an integrated circuit for detecting a position indicated by a position indicator, the integrated circuit being configured to have a plurality of electrodes functioning as a sensor, connected to a coil including a transmission coil that transmits an alternating magnetic field based on a transmission signal to the position indicator, detecting a pen signal generated by the position indicator, generating a transmission signal having a frequency based on frequency information of the detected pen signal, and transmitting an alternating magnetic field to the position indicator via the coil.

[0013] Form 3: One or more embodiments of the present invention propose a position detection method in a position detector, comprising: a first step in which the position detector transmits a first signal to a position indicator; a second step in which the position indicator transmits a second signal to the position detector; a third step in which the position detector detects frequency information from the second signal; a fourth step in which the position detector generates a third signal having a frequency different from that of the first signal based on the frequency information detected in the third step; and a fifth step in which the position detector transmits the third signal generated in the fourth step to the position indicator.

[0014] Form 4: One or more embodiments of the present invention propose a position detector including a detection coil configured to function as a sensor, a transmission coil that transmits an alternating magnetic field based on a transmission signal to a position indicator, and a signal processing circuit connected to the detection coil and the transmission coil, detects a pen signal generated by the position indicator, generates the transmission signal having a frequency based on frequency information of the detected pen signal, and transmits it to the transmission coil. Effect of the Invention

[0015] According to one or more embodiments of the present invention, by suppressing attenuation of the amplitude of the pen signal obtained from the electrical circuit of the position indicator, it is possible to suppress deterioration in the position detection accuracy of the position indicator and deterioration in the detection accuracy of the writing pressure, etc. [Brief description of the drawings]

[0016] [Figure 1] 1 is a diagram showing a configuration of an input device according to a first embodiment of the present invention. [Diagram 2] 1 is a diagram illustrating the operation principle of a position detector according to a first embodiment of the present invention. [Diagram 3] 2 is a diagram illustrating an example of a configuration of a frequency analysis unit in the position detector according to the first embodiment of the present invention. FIG. [Figure 4A]FIG. 4 is a diagram illustrating the frequency characteristics of a TX signal according to the first embodiment of the present invention. [Figure 4B] FIG. 4 is a diagram illustrating a voltage waveform of a TX signal according to the first embodiment of the present invention. [Diagram 5] FIG. 3 is a process flow diagram of the position detector according to the first embodiment of the present invention. [Figure 6] FIG. 3 is a process flow diagram of the position detector according to the first embodiment of the present invention. [Figure 7A] 4 is a diagram illustrating the frequency characteristics of an RX signal according to the first embodiment of the present invention. FIG. [Figure 7B] 4 is a diagram illustrating an example of a voltage waveform of an RX signal according to the first embodiment of the present invention. FIG. [Figure 8] FIG. 11 is a diagram showing a configuration of an input device according to a second embodiment of the present invention. [Figure 9] FIG. 11 is a diagram showing the relationship between an output from a frequency analysis unit of a position detector according to a second embodiment of the present invention and frequency / phase information transmitted to a multiplexer. [Figure 10] FIG. 11 is a process flow diagram of a position detector according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing a configuration of an input device according to a third embodiment of the present invention. [Figure 12] FIG. 13 is a diagram showing the relationship between an output from a frequency analysis unit of a position detector according to a third embodiment of the present invention and frequency / phase information transmitted to a multiplexer. [Figure 13] FIG. 11 is a process flow diagram of a position detector according to a third embodiment of the present invention. [Figure 14A] FIG. 10 is a diagram illustrating the frequency characteristics of a TX signal according to a conventional example. [Figure 14B] FIG. 13 is a diagram illustrating a voltage waveform of a TX signal according to a conventional example. [Figure 15A] FIG. 11 is a diagram illustrating the frequency characteristics of an RX signal according to a conventional example. [Figure 15B] FIG. 13 is a diagram illustrating a voltage waveform of an RX signal according to a conventional example. [Figure 16] 13A to 13C are diagrams illustrating the operation principle of a position detector according to a fourth embodiment of the present invention. [Figure 17] FIG. 11 is a process flow diagram of a position detector according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 13 and FIGS.

[0018] <First embodiment> A position detector 1 according to this embodiment will be described with reference to FIGS. In the following, the position detector 1 according to the present embodiment will be described by taking as an example an input device including the position detector 1 according to the present embodiment.

[0019] <Input device configuration> As shown in FIG. 1, the input device includes a position detector 1 according to the present embodiment and a position indicator 2.

[0020] <Configuration of position indicator 2> The position indicator 2 indicates its own position to the position detector 1 by electromagnetic induction. As shown in FIG. 1, the position indicator 2 is composed of a position indication coil 13 that forms a resonant circuit 61, a resonant capacitor 60a connected in parallel to the position indication coil 13, and a variable capacitor 15 connected in parallel to the resonant capacitor 60a. A resonant circuit 61 including a variable capacitor 15 resonates with a transmission signal received from a position detector 1, which will be described later, and exchanges energy. The position indicator 2 transmits a resonance signal detected by this resonance circuit 61 to the position detector 1 , thereby indicating the position of the position indicator 2 to the position detector 1 .

[0021] <Configuration of position detector 1> The position detector 1 includes a position detection coil 101 and a signal processing circuit . The position detection coil 101 includes an X-axis direction loop coil group 104a and a Y-axis direction loop coil group 104b, which function as sensors, stacked together. The X-axis direction loop coil group 104 a and the Y-axis direction loop coil group 104 b form a position detection coil 101 . Each of the loop coil groups 104a and 104b is made up of, for example, 40 rectangular loop coils. The loop coils constituting each of the loop coil groups 104a and 104b are arranged at equal intervals and overlap one another.

[0022] The position detector 1 includes a selection circuit 106 to which the X-axis direction loop coil group 104a and the Y-axis direction loop coil group 104b are connected. The selection circuit 106 sequentially selects one of the two loop coil groups 104a and 104b.

[0023] The signal processing circuit 102 is configured to include a switching connection circuit 107, a transmitting amplifier 108, a D / A conversion circuit 109, a waveform generation unit 110, a receiving amplifier 111, an A / D conversion circuit 112, a frequency analysis unit 113, and a control unit 120. In the following, the configuration block consisting of the transmitting amplifier 108, the D / A conversion circuit 109, and the waveform generation unit 110 will be referred to as the "TX unit", and the configuration block consisting of the receiving amplifier 111, the A / D conversion circuit 112, and the frequency analysis unit 113 will be referred to as the "RX unit".

[0024] The switching connection circuit 107 switches the connection destination (transmission side terminal T, reception side terminal R in FIG. 1) to which the loop coil selected by the selection circuit 106 is connected, according to a control signal from the control unit 120 described later. Of these connections, a transmission amplifier 108 is connected to a transmission side terminal T, and a reception amplifier 111 is connected to a reception side terminal R.

[0025] The waveform generating unit 110 generates a transmission signal (hereinafter referred to as a "TX signal") to be supplied to a transmission coil 104 serving as a position detection coil 101 as shown in FIG. 4(A) based on a control signal obtained from a frequency analyzing unit 113 described later via a control unit 120 described later. As shown in FIG. 2, the waveform generating section 110 includes a signal generating section 110A and a multiplexer (MUX) 110B.

[0026] The signal generating section 110A includes a plurality of signal generators that generate a plurality of transmission signals with different frequencies. For example, as shown in FIG. 2, the signal generating unit 110A generates a signal having a frequency f TX , f' TX , f '' TX It generates multiple transmission signals with three different frequencies: The output terminals of the multiple signal generators of the signal generating section 110A are individually connected to multiple input terminals of a multiplexer 110B, and are connected to the output terminal of the multiplexer 110B based on a control signal from the control section 120, which will be described later.

[0027] The multiplexer 110B receives a plurality of transmission signals with different frequencies from the signal generating unit 110A, multiplexes them, and outputs a TX signal having a unique frequency. Specifically, the multiplexer 110B outputs a TX signal corresponding to the frequency / phase of the RX signal input from the frequency analysis unit 113 described later, based on the frequency / phase information of the pen signal (hereinafter referred to as the "RX signal") detected by the detection coil 104 as the position detection coil 101 analyzed in the frequency analysis unit 113 described later. The analog voltage waveform of the TX signal transmitted to the position detector 1 via the transmitting coil 104 serving as the position detection coil 101 is as shown in FIG. 4(B).

[0028] The digital signal output from the waveform generating section 110 is converted to an analog signal in the D / A conversion circuit 109 , amplified in the transmission amplifier 108 , and supplied to the transmission side terminal T of the switching connection circuit 107 .

[0029] The RX signal detected by the detection coil 104 as the position detection coil 101 is amplified in the receiving amplifier 111 via the receiving terminal R of the switching connection circuit 107, and then converted into a digital signal in the A / D conversion circuit 112 and supplied to the frequency analysis unit 113.

[0030] The frequency analysis unit 113 receives the RX signal converted into a digital signal and executes a discrete Fourier transform process. The frequency analysis unit 113 outputs frequency / phase information of the RX signal to the control unit 120, which will be described later, as a result of the execution of the discrete Fourier transform process.

[0031] The frequency analysis unit 113 is, for example, a DFT having one input and six outputs as shown in FIG. 3, and performs frequency analysis on a plurality of discrete frequencies. The frequency analysis result in frequency analysis section 113 is fed back to multiplexer 110B of waveform generation section 110 as a control signal, as shown in FIG.

[0032] The control unit 120 executes overall control of the signal processing circuit 102 based on a control program stored in, for example, a ROM (Read Only Memory) (not shown) or the like. Specifically, the control unit 120 executes RX signal reception processing, discrete Fourier transform processing in the frequency analysis unit 113, frequency / phase information reception processing, signal multiplexing processing in the multiplexer 110B, signal generation processing in the signal generation unit 110A, and control of TX signal transmission processing, etc. The control unit 120 stores the frequency / phase information of the RX signal obtained from the frequency analysis unit 113 in a memory. Based on the pen signal generated by the position indicator 2, the control unit 120 causes the waveform generation unit 110 to generate a transmission signal having a different frequency according to the frequency of the pen signal. The control unit 120 controls the operation of the multiplexer 110B so as to cause the position indicator 2 to emit an alternating magnetic field via the sensors (104a, 104b). When the frequency of the pen signal generated by the position indicator 2 changes with respect to the detected frequency of the pen signal, the control unit 120 controls the operation of the multiplexer 110B to generate a transmission signal following the change in the frequency. The control unit 120 controls the operation of the multiplexer 110B to generate a transmission signal at the timing before the start of the coordinate calculation process of the position indicator 2. The control unit 120 generates a transmission signal multiple times in one coordinate calculation process, and controls the operation of the multiplexer 110B to continuously generate a transmission signal with the same frequency during multiple times when at least one coordinate calculation process is performed. The control unit 120 causes an induced voltage to be generated in each loop coil of the X-axis direction loop coil group 104a and the Y-axis direction loop coil group 104b by the pen signal transmitted from the position indicator 2. The control unit 120 calculates the coordinate values of the indicated positions in the X-axis direction and the Y-axis direction of the position indicator 2 based on the level of the voltage value of the induced voltage generated in each loop coil. The control unit 120 detects the pen pressure based on the phase difference between the transmitted transmission signal and the received pen signal.

[0033] <Processing of the position detector 1> The processing of the position detector 1 according to the present embodiment will be described with reference to FIGS. 5 and 6. In the following, the description will be divided into the case where the process is started when there is a change in the frequency / phase information of the RX signal and the case where the process is started at the timing before the coordinate calculation process of the position indicator 2.

[0034] <Case where the process is started when there is a change in the frequency / phase information of the RX signal> The case where the process is started when there is a change in the frequency / phase information of the RX signal will be described with reference to FIG. 5.

[0035] The control unit 120 causes the signal receiving unit to receive the RX signal from the position indicator 2 (step S110). The RX signal received by the signal receiving unit is converted into a desired digital signal and sent to the frequency analysis unit 113 via the control unit 120 .

[0036] The frequency analysis unit 113 receives the RX signal converted into a digital signal and executes a discrete Fourier transform process. The frequency analysis unit 113 sends frequency / phase information of the RX signal to the control unit 120 as a result of the discrete Fourier transform processing (step S120). At this time, the control unit 120 stores the frequency / phase information of the RX signal obtained from the frequency analysis unit 113 in a memory.

[0037] The control unit 120 compares the frequency / phase information of the RX signal in the memory with the frequency / phase information of the RX signal obtained from the frequency analysis unit 113, and determines whether or not there has been a change in the frequency / phase information of the RX signal (step S130). Then, the control unit 120 compares the frequency / phase information of the RX signal in the memory with the frequency / phase information of the RX signal obtained from the frequency analysis unit 113, and if it determines that there has been no change in the frequency / phase information of the RX signal ("NO" in step S130), it returns to the original processing and transitions to standby mode.

[0038] The control unit 120 compares the frequency / phase information of the RX signal in the memory with the frequency / phase information of the RX signal obtained from the frequency analysis unit 113, and if it determines that there has been a change in the frequency / phase information of the RX signal ("YES" in step S130), it transmits the frequency / phase information of the RX signal from the frequency analysis unit 113 to the multiplexer 110B, and the multiplexer 110B receives the transmitted frequency / phase information of the RX signal (step S140).

[0039] The signal generating section 110A generates a plurality of transmission signals with different frequencies. The multiplexer 110B receives a plurality of transmission signals with different frequencies from the signal generating unit 110A, multiplexes them, and outputs a TX signal that corresponds to the frequency / phase of the RX signal received from the frequency analyzing unit 113 (step S150).

[0040] The control unit 120 causes the position indicator 2 to transmit a TX signal via the signal transmitting unit. The TX signal output from the control unit 120 is transmitted to the position detection coil 101 of the position indicator 2 via the switching connection circuit 107 (step S160).

[0041] <When starting processing before the coordinate calculation processing of the position indicator 2> A case where the process is started at a timing before the coordinate calculation process of the position indicator 2 will be described with reference to FIG.

[0042] The control unit 120 causes the signal receiving unit to receive the RX signal from the position indicator 2 (step S110). The RX signal received by the control unit 120 is converted into a desired digital signal.

[0043] The control unit 120 determines whether or not the current processing mode is the timing before the coordinate detection processing (step S170). If the control unit 120 determines that the current processing mode is not the timing before the coordinate detection processing ("NO" in step S170), it returns the processing to the original state and transitions to the standby mode.

[0044] When the control unit 120 determines that the current processing mode is the timing before the coordinate detection processing ("YES" in step S170), the RX signal received by the signal receiving unit is converted into a desired digital signal and sent to the frequency analysis unit 113 via the control unit 120.

[0045] The frequency analysis unit 113 receives the RX signal converted into a digital signal from the control unit 120 and executes a discrete Fourier transform process. The frequency analysis unit 113 sends frequency / phase information of the RX signal to the multiplexer 110B as a result of the discrete Fourier transform processing (step S120). At this time, the control unit 120 stores the frequency / phase information of the RX signal obtained from the frequency analysis unit 113 in a memory.

[0046] The multiplexer 110B receives the frequency / phase information of the RX signal from the frequency analysis unit 113 (step S140).

[0047] The signal generating section 110A generates a plurality of transmission signals with different frequencies. The multiplexer 110B receives a plurality of transmission signals with different frequencies from the signal generating unit 110A, multiplexes them, and outputs a TX signal that corresponds to the frequency / phase of the RX signal received from the frequency analyzing unit 113 (step S150).

[0048] The control unit 120 causes the position indicator 2 to transmit a TX signal via the signal transmitting unit. The TX signal output from the control unit 120 is transmitted to the position detection coil 101 of the position indicator 2 via the switching connection circuit 107 (step S160).

[0049] <Actions and Effects> As described above, the position detector 1 according to this embodiment includes a sensor having a plurality of electrodes (e.g., the X-axis direction loop coil group 104a and the Y-axis direction loop coil group 104b), and a signal processing circuit 102 connected to the sensor (e.g., the X-axis direction loop coil group 104a and the Y-axis direction loop coil group 104b), which detects a pen signal generated by the position indicator 2, generates a transmission signal of a different frequency according to the frequency of the detected pen signal, and transmits an alternating magnetic field to the position indicator 2 via the sensor (e.g., the X-axis direction loop coil group 104a and the Y-axis direction loop coil group 104b). In other words, the signal processing circuit 102 of the position detector 1 in this embodiment detects the pen signal generated by the position indicator 2, generates a transmission signal of a different frequency depending on the frequency of the detected pen signal, and transmits an alternating magnetic field to the position indicator 2 via sensors (e.g., X-axis loop coil group 104a and Y-axis loop coil group 104b). For example, the position detector 1 according to this embodiment generates and transmits to the position indicator 2 transmission signals of different frequencies depending on the behavior of the position indicator 2, for example, the presence or absence of writing pressure on the position indicator 2. More specifically, the position detector 1 of this embodiment transmits to the position indicator 2 a transmission signal having a frequency corresponding to the frequency transmitted from the position indicator 2, as shown in FIG. 4(A), for example. Therefore, the resonant energy supplied to the position indicator 2 is maintained regardless of whether or not there is pen pressure on the position indicator 2, and the amplitude of the voltage waveform sent from the position indicator 2 is also maintained, as shown in Figure 4 (B). In addition, in the conventional position indicator 2, the resonance frequency f' pen When the position indicator 2 becomes TX However, only the resonance energy due to the frequency characteristic of the resonance signal was obtained, and the resonance signal was attenuated. In this embodiment, as shown in FIG. 7(A) and FIG. 7(B), the position indicator 2 is TX Since it is possible to obtain resonance energy due to the frequency characteristic, it is possible to obtain a resonance signal equivalent to that in the absence of pen pressure without attenuating the resonance signal. Therefore, even if writing pressure is applied to the position indicator 2, a decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the position detection accuracy of the position indicator can be suppressed. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the detection accuracy of the writing pressure in the position indicator 2 can be suppressed. Since the resonance energy supplied to the position indicator 2 is optimized, improvement in the position detection accuracy can be expected, for example, even for the position indicator 2 in a hover state. Because the resonant energy supplied to the position indicator 2 is optimized, even if, for example, a magnet or a metal casing deteriorates over time, or the values ​​of the position indication coil and resonant capacitor that form the resonant circuit in the position indicator 2 change due to environmental conditions, etc., a decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed.

[0050] When the frequency of the pen signal generated by the position indicator 2 changes with respect to the frequency of the detected pen signal, the signal processing circuit 102 of the position detector 1 according to this embodiment generates an output signal that follows the change in frequency. That is, the signal processing circuit 102 of the position detector 1 according to this embodiment generates a transmission signal that follows the change in frequency of the pen signal generated by the position indicator 2. For example, the position detector 1 according to this embodiment generates an output signal that follows the behavior of the position indicator 2, for example, a frequency that changes depending on the presence or absence of writing pressure on the position indicator 2. More specifically, the position detector 1 of this embodiment transmits to the position indicator 2 a transmission signal having a frequency corresponding to the frequency transmitted from the position indicator 2, as shown in FIG. 4(A), for example. Therefore, the resonant energy supplied to the position indicator 2 is maintained regardless of whether or not there is pen pressure on the position indicator 2, and the amplitude of the voltage waveform sent from the position indicator 2 is also maintained, as shown in Figure 4 (B). In addition, in the conventional position indicator 2, the resonance frequency f' pen When the position indicator 2 becomes TX However, only the resonance energy due to the frequency characteristic of the resonance signal was obtained, and the resonance signal was attenuated. In this embodiment, as shown in FIG. 7(A) and FIG. 7(B), the position indicator 2 is TX Since it is possible to obtain resonance energy due to the frequency characteristic, it is possible to obtain a resonance signal equivalent to that in the absence of pen pressure without attenuating the resonance signal. Therefore, even if writing pressure is applied to the position indicator 2, a decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the position detection accuracy of the position indicator can be suppressed. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the detection accuracy of the writing pressure in the position indicator 2 can be suppressed.

[0051] The signal processing circuit 102 of the position detector 1 according to this embodiment generates a transmission signal at a timing before the coordinate calculation process of the position indicator 2 starts. In other words, a decrease in the S / N ratio of the pen signal sent from the position indicator 2 has the greatest effect on the coordinate calculation process of the position indicator 2. However, in the signal processing circuit 102 of the position detector 1 according to this embodiment, a transmission signal is generated at a timing before the coordinate calculation process of the position indicator 2 starts. Therefore, in the coordinate calculation process of the position indicator 2, the coordinate calculation process can be executed using the pen signal sent from the position indicator 2 in which the decrease in S / N is suppressed. Moreover, in the signal processing circuit 102 of the position detector 1 according to this embodiment, a transmission signal is generated at a timing before the coordinate calculation process of the position indicator 2 starts. Therefore, by optimizing the start-up timing of the waveform generating section 110 and the D / A conversion circuit 109, the power consumption of the waveform generating section 110 and the D / A conversion circuit 109 can be minimized. Therefore, even if writing pressure is applied to the position indicator 2, it is possible to suppress a decrease in the S / N ratio of the pen signal sent from the position indicator 2 while minimizing power consumption. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the position detection accuracy of the position indicator can be suppressed. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the detection accuracy of the writing pressure in the position indicator 2 can be suppressed.

[0052] The signal processing circuit 102 of the position detector 1 according to this embodiment generates a transmission signal multiple times in one coordinate calculation process, and generates a transmission signal at the same frequency continuously during the multiple times that at least one coordinate calculation process is performed. For example, when calculating the coordinates of a position indicator 2 existing in an N×N area within a sensor, in one coordinate calculation process, sensing is performed on N X sensors and N Y sensors, that is, the process of generating transmission signals is performed multiple times, and the coordinate calculation process is executed based on the reception intensity distribution of the sensors. Here, if the frequency of the transmission signal is changed during sensing of the N X sensors and the N Y sensors, that is, during multiple times when one coordinate calculation process is performed, the amplitude level of the pen signal will change, and there is a possibility that accurate coordinates cannot be calculated. Therefore, the signal processing circuit 102 generates a transmission signal multiple times in one coordinate calculation process, and by continuously generating a transmission signal at the same frequency during the multiple times that at least one coordinate calculation process is performed, it is possible to prevent adverse effects caused by dynamically changing the frequency.

[0053] <Second embodiment> A position detector 1A according to this embodiment will be described with reference to FIGS. Note that the position detector 1A according to this embodiment differs from the position detector 1 according to the first embodiment only in the configuration of the frequency analysis unit 113A, and therefore only matters relating to the frequency analysis unit 113A will be described below.

[0054] <Configuration of signal processing circuit 102A> As shown in FIG. 8, the signal processing circuit 102A of the position detector 1A according to this embodiment is configured to include a switching connection circuit 107, a transmitting amplifier 108, a D / A conversion circuit 109, a waveform generating unit 110, a receiving amplifier 111, an A / D conversion circuit 112, a frequency analysis unit 113A, and a control unit 120. In addition, since the components having the same reference numerals as those in the first embodiment have the same functions, detailed description thereof will be omitted.

[0055] The frequency analysis unit 113A performs frequency analysis on a plurality of discrete frequencies. The frequency analysis unit 113A extracts, from among the discrete values ​​of the frequency detection, the closest discrete value to which the crest value of the pen signal received from the position indicator 2 indicates a peak, as a frequency. For example, as shown in FIG. 9, the frequency analysis unit 113A performs discrete Fourier transform processing on six frequencies for one input, and outputs the processing results as digital data of the peak value of the pen signal at each frequency. In other words, the frequency analysis unit 113A extracts the crest value for each frequency as a discrete value. For example, if the frequency indicating the peak of the crest value does not match each frequency as a discrete value, the frequency analysis unit 113A extracts the closest discrete value at which the crest value indicates the peak as the frequency. For example, in the example shown in FIG. 9, the frequency indicating the peak of the crest value is D2-3, and the frequency as the nearest discrete value is D2, so the frequency analysis unit 113A extracts D2 as the frequency and sets D2 as the frequency / phase information to be sent.

[0056] <Processing of position detector 1A> The processing of the position detector 1A according to this embodiment will be described with reference to FIG. In the following, a case where processing is started when there is a change in the frequency / phase information of the RX signal will be described as an example. Even when the process is started at a timing before the coordinate calculation process of the position indicator 2, only the timing of the process start is different, and the other processes are the same.

[0057] The control unit 120 causes the signal receiving unit to receive the RX signal from the position indicator 2 (step S110). The RX signal received by the signal receiving unit is converted into a desired digital signal and sent via the control unit 120 to the frequency analysis unit 113A.

[0058] The frequency analysis unit 113A receives the RX signal converted into a digital signal and executes a discrete Fourier transform process. The frequency analysis unit 113A extracts, from the discrete values ​​of the frequency detection, the discrete value closest to the peak value of the pen signal received from the position indicator 2 as a frequency, and sets it as the result of the discrete Fourier transform process. The frequency analysis unit 113A sends frequency / phase information of the RX signal to the control unit 120 as a result of the discrete Fourier transform processing (step S120A). At this time, the control unit 120 stores in a memory the frequency / phase information of the RX signal obtained from the frequency analysis unit 113A.

[0059] The control unit 120 compares the frequency / phase information of the RX signal in the memory with the frequency / phase information of the RX signal obtained from the frequency analysis unit 113A, and determines whether or not there has been a change in the frequency / phase information of the RX signal (step S130). Then, the control unit 120 compares the frequency / phase information of the RX signal in the memory with the frequency / phase information of the RX signal obtained from the frequency analysis unit 113A, and if it determines that there has been no change in the frequency / phase information of the RX signal ("NO" in step S130), it returns to the original processing and transitions to standby mode.

[0060] The control unit 120 compares the frequency / phase information of the RX signal in the memory with the frequency / phase information of the RX signal obtained from the frequency analysis unit 113A, and if it determines that there has been a change in the frequency / phase information of the RX signal ("YES" in step S130), the multiplexer 110B receives the frequency / phase information of the RX signal from the frequency analysis unit 113A (step S140).

[0061] The signal generating section 110A generates a plurality of transmission signals with different frequencies. The multiplexer 110B receives a plurality of transmission signals with different frequencies from the signal generating unit 110A, multiplexes them, and outputs a TX signal that corresponds to the frequency / phase of the RX signal received from the frequency analyzing unit 113A (step S150).

[0062] The control unit 120 causes the position indicator 2 to transmit a TX signal via the signal transmitting unit. The TX signal output from the control unit 120 is transmitted to the position detection coil 101 of the position indicator 2 via the switching connection circuit 107 (step S160).

[0063] <Actions and Effects> As described above, the signal processing circuit 102A of the position detector 1A according to this embodiment performs frequency analysis on a plurality of discrete frequencies, and extracts, from among the discrete values ​​of the frequency detection, the discrete value that is closest to the peak value of the crest value of the pen signal received from the position indicator 2 as the frequency. That is, for example, as shown in FIG. 9, when the frequency indicating the peak of the crest value is D2-3, the frequency indicating the peak of the crest value is set to D2 as the nearest discrete value. Here, since the interval between the discrete values ​​is sufficiently small, frequency information indicating the peak of the crest value is sent as D2 to the multiplexer 110B, and a TX signal is output in the signal generating unit 110A. This is expected to have the effect of suppressing a decrease in the S / N ratio of the pen signal sent from the position indicator 2, even if pen pressure is being applied to the position indicator 2. Since it is expected to have the effect of suppressing a decrease in the S / N ratio of the pen signal sent from the position indicator 2, it is also expected to have the effect of suppressing a decrease in the position detection accuracy of the position indicator. Since it is expected that the effect of suppressing the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be achieved, it is also expected that the effect of suppressing the decrease in the detection accuracy of the writing pressure in the position indicator 2 can be achieved.

[0064] <Third embodiment> A position detector 1B according to this embodiment will be described with reference to FIGS. Note that the position detector 1B according to this embodiment differs from the position detectors 1 and 1A according to the first and second embodiments only in the configuration of the frequency analysis unit 113B, and therefore, hereinafter, only matters relating to the frequency analysis unit 113B will be described.

[0065] <Configuration of signal processing circuit 102B> As shown in FIG. 8, the signal processing circuit 102B of the position detector 1A according to this embodiment is configured to include a switching connection circuit 107, a transmitting amplifier 108, a D / A conversion circuit 109, a waveform generating unit 110, a receiving amplifier 111, an A / D conversion circuit 112, a frequency analysis unit 113B, and a control unit 120. In addition, since the components having the same reference numerals as those in the first and second embodiments have the same functions, detailed description thereof will be omitted.

[0066] When the frequency indicating the peak of the crest value of the pen signal received from the position indicator 2 does not match the discrete value of the frequency detection, the frequency analysis unit 113B performs an interpolation calculation between the frequency indicating the peak of the crest value and the adjacent discrete value of the frequency detection, and extracts the frequency. For example, as shown in FIG. 3, frequency analysis section 113B performs discrete Fourier transform processing on six frequencies for one input, and outputs the processing results as digital data of the peak value of the pen signal at each frequency. For example, in the example shown in FIG. 12, the frequency indicating the peak of the crest value is D2-3. The frequency analysis unit 113B performs an interpolation operation on three points, the frequency (D2-3) where the crest value shows a peak and the adjacent discrete values ​​(D2 and D3) of the frequency detection, and extracts the frequency (D2-3) where the crest value shows a peak.

[0067] <Processing of position detector 1B> The process of the position detector 1B according to this embodiment will be described with reference to FIG. In the following, a case where processing is started when there is a change in the frequency / phase information of the RX signal will be described as an example. Even when the process is started at a timing before the coordinate calculation process of the position indicator 2, only the timing of the process start is different, and the other processes are the same.

[0068] The control unit 120 causes the signal receiving unit to receive the RX signal from the position indicator 2 (step S110). The RX signal received by the signal receiving unit is converted into a desired digital signal and sent via the control unit 120 to the frequency analysis unit 113B.

[0069] The frequency analysis unit 113B receives the RX signal converted into a digital signal and executes a discrete Fourier transform process. When the frequency indicating the peak of the crest value of the pen signal received from the position indicator 2 does not match the discrete value of the frequency detection, the frequency analysis unit 113B performs an interpolation calculation between the frequency indicating the peak of the crest value and the adjacent discrete value of the frequency detection, and extracts the frequency. The frequency analysis unit 113B sends frequency / phase information of the RX signal to the control unit 120 as a result of the discrete Fourier transform processing (step S120B). At this time, the control unit 120 stores the frequency / phase information of the RX signal obtained from the frequency analysis unit 113B in a memory.

[0070] The control unit 120 compares the frequency / phase information of the RX signal in the memory with the frequency / phase information of the RX signal obtained from the frequency analysis unit 113B, and determines whether or not there has been a change in the frequency / phase information of the RX signal (step S130). Then, the control unit 120 compares the frequency / phase information of the RX signal in the memory with the frequency / phase information of the RX signal obtained from the frequency analysis unit 113B, and if it determines that there has been no change in the frequency / phase information of the RX signal ("NO" in step S130), it returns to the original processing and transitions to standby mode.

[0071] The control unit 120 compares the frequency / phase information of the RX signal in the memory with the frequency / phase information of the RX signal obtained from the frequency analysis unit 113B, and if it determines that there has been a change in the frequency / phase information of the RX signal ("YES" in step S130), the multiplexer 110B receives the frequency / phase information of the RX signal from the frequency analysis unit 113B (step S140).

[0072] The signal generating section 110A generates a plurality of transmission signals with different frequencies. The multiplexer 110B receives a plurality of transmission signals with different frequencies from the signal generating unit 110A, multiplexes them, and outputs a TX signal that corresponds to the frequency / phase of the RX signal received from the frequency analyzing unit 113B (step S150).

[0073] The control unit 120 causes the position indicator 2 to transmit a TX signal via the signal transmitting unit. The TX signal output from the control unit 120 is transmitted to the position detection coil 101 of the position indicator 2 via the switching connection circuit 107 (step S160).

[0074] <Actions and Effects> As described above, when the frequency at which the crest value of the pen signal received from the position indicator 2 shows a peak does not match the discrete value of the frequency detection, the signal processing circuit 102B of the position detector 1A according to this embodiment performs an interpolation operation between the frequency at which the crest value shows a peak and the adjacent discrete value of the frequency detection to extract the frequency. That is, for example, as shown in FIG. 12, when the frequency showing the peak of the crest value is D2-3, an interpolation operation is performed between three points: the frequency (D2-3) where the crest value shows the peak, and the adjacent discrete values ​​of the frequency detection (D2 and D3), and the frequency (D2-3) where the crest value shows the peak is extracted. Therefore, by extracting the frequency (D2-3) that shows a peak of the crest value close to the true value, it is possible to suppress a decrease in the S / N ratio of the pen signal sent from the position indicator 2, even if pen pressure is applied to the position indicator 2. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the position detection accuracy of the position indicator 2 can be suppressed. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2B can be suppressed, the decrease in the detection accuracy of the writing pressure in the position indicator 2B can be suppressed.

[0075] <Fourth embodiment> The position detector 1 according to this embodiment will be described with reference to FIGS. 1, 3, 4, 6, 7, 16 and 17. FIG. In the following, the position detector 1 according to the present embodiment will be described by taking as an example an input device including the position detector 1 according to the present embodiment.

[0076] <Input device configuration> As shown in FIG. 1, the input device includes a position detector 1 according to the present embodiment and a position indicator 2.

[0077] <Configuration of position indicator 2> The position indicator 2 indicates its own position to the position detector 1 by electromagnetic induction. As shown in FIG. 1, the position indicator 2 is composed of a position indication coil 13 that forms a resonant circuit 61, a resonant capacitor 60a connected in parallel to the position indication coil 13, and a variable capacitor 15 connected in parallel to the resonant capacitor 60a. A resonant circuit 61 including a variable capacitor 15 resonates with a transmission signal received from a position detector 1, which will be described later, and exchanges energy. The position indicator 2 transmits a resonance signal detected by this resonance circuit 61 to the position detector 1 , thereby indicating the position of the position indicator 2 to the position detector 1 .

[0078] <Configuration of position detector 1> The position detector 1 includes a position detection coil 101 and a signal processing circuit . The position detection coil 101 includes an X-axis direction loop coil group 104a and a Y-axis direction loop coil group 104b, which function as sensors, stacked together. The X-axis direction loop coil group 104 a and the Y-axis direction loop coil group 104 b form a position detection coil 101 . Each of the loop coil groups 104a and 104b is made up of, for example, 40 rectangular loop coils. The loop coils constituting each of the loop coil groups 104a and 104b are arranged at equal intervals and overlap one another.

[0079] The position detector 1 includes a selection circuit 106 to which the X-axis direction loop coil group 104a and the Y-axis direction loop coil group 104b are connected. The selection circuit 106 sequentially selects one of the two loop coil groups 104a and 104b.

[0080] The signal processing circuit 102 is configured to include a switching connection circuit 107, a transmitting amplifier 108, a D / A conversion circuit 109, a waveform generation unit 110, a receiving amplifier 111, an A / D conversion circuit 112, a frequency analysis unit 113, and a control unit 120. In the following, the configuration block consisting of the transmitting amplifier 108, the D / A conversion circuit 109, and the waveform generation unit 110 will be referred to as the "TX unit", and the configuration block consisting of the receiving amplifier 111, the A / D conversion circuit 112, and the frequency analysis unit 113 will be referred to as the "RX unit".

[0081] The switching connection circuit 107 switches the connection destination (transmission side terminal T, reception side terminal R in FIG. 1) to which the loop coil selected by the selection circuit 106 is connected, according to a control signal from the control unit 120 described later. Of these connections, a transmission amplifier 108 is connected to a transmission side terminal T, and a reception amplifier 111 is connected to a reception side terminal R.

[0082] The waveform generating unit 110 generates a transmission signal (hereinafter referred to as a "TX signal") to be supplied to a transmission coil 104 serving as a position detection coil 101 as shown in FIG. 4(A) based on a control signal obtained from a frequency analyzing unit 113 described later via a control unit 120 described later. As shown in FIG. 16, the waveform generating section 110 includes a signal generating section 110A and a multiplexer (MUX) 110B.

[0083] The signal generating section 110A includes a plurality of signal generators that generate a plurality of transmission signals with different frequencies. For example, as shown in FIG. 16, the signal generating unit 110A generates a signal having a frequency f TX , f' TX , f” TX It generates multiple transmission signals with three different frequencies: The output terminals of the multiple signal generators of the signal generating section 110A are individually connected to multiple input terminals of a multiplexer 110B, and are connected to the output terminal of the multiplexer 110B based on a control signal from the control section 120, which will be described later.

[0084] The multiplexer 110B receives a plurality of transmission signals with different frequencies from the signal generating unit 110A, multiplexes them, and outputs a TX signal having a unique frequency. Specifically, the multiplexer 110B outputs a TX signal corresponding to the frequency / phase of the RX signal input from the frequency analysis unit 113 described later, based on the frequency / phase information of the pen signal (hereinafter referred to as the "RX signal") detected by the detection coil 104 as the position detection coil 101 analyzed in the frequency analysis unit 113 described later. The analog voltage waveform of the TX signal transmitted to the position detector 1 via the transmitting coil 104 serving as the position detection coil 101 is as shown in FIG. 4(B).

[0085] The digital signal output from the waveform generating section 110 is converted to an analog signal in the D / A conversion circuit 109 , amplified in the transmission amplifier 108 , and supplied to the transmission side terminal T of the switching connection circuit 107 .

[0086] The RX signal detected by the detection coil 104 as the position detection coil 101 is amplified in the receiving amplifier 111 via the receiving terminal R of the switching connection circuit 107, and then converted into a digital signal in the A / D conversion circuit 112 and supplied to the frequency analysis unit 113.

[0087] The frequency analysis unit 113 receives the RX signal converted into a digital signal and executes a discrete Fourier transform process. The frequency analysis unit 113 outputs frequency / phase information of the RX signal to the control unit 120, which will be described later, as a result of the execution of the discrete Fourier transform process.

[0088] The frequency analysis unit 113 is, for example, a DFT having one input and six outputs as shown in FIG. 3, and performs frequency analysis on a plurality of discrete frequencies. The result of the frequency analysis in frequency analysis section 113 is fed back as a control signal to multiplexer 110B of waveform generation section 110 via control section 120, as shown in FIG.

[0089] The control unit 120 executes overall control of the signal processing circuit 102 based on a control program stored in, for example, a ROM (Read Only Memory) (not shown) or the like. Specifically, the control unit 120 executes RX signal reception processing, discrete Fourier transform processing in the frequency analysis unit 113, frequency / phase information reception processing, signal multiplexing processing in the multiplexer 110B, signal generation processing in the signal generation unit 110A, and control of TX signal transmission processing, etc. The control unit 120 stores the frequency / phase information of the RX signal obtained from the frequency analysis unit 113 in a memory. Based on the RX signal obtained from the frequency analysis section 113, that is, the pen signal generated by the position indicator 2, the control section 120 causes the waveform generation section 110 to generate a transmission signal of a different frequency according to the frequency of the pen signal. The control unit 120 controls the operation of the multiplexer 110B so as to cause the position indicator 2 to emit an alternating magnetic field via the sensors (104a, 104b). When the frequency of the pen signal generated by the position indicator 2 changes with respect to the detected frequency of the pen signal, the control unit 120 controls the operation of the multiplexer 110B to generate a transmission signal following the change in the frequency. The control unit 120 controls the operation of the multiplexer 110B to generate a transmission signal at the timing before the start of the coordinate calculation process of the position indicator 2. The control unit 120 generates a transmission signal multiple times in one coordinate calculation process, and controls the operation of the multiplexer 110B to continuously generate a transmission signal of the same frequency during multiple times when at least one coordinate calculation process is performed. The control unit 120 calculates the coordinate values of the indicated positions in the X-axis direction and Y-axis direction of the position indicator 2 based on the levels of the voltage values of the induced voltages generated in each loop coil of the X-axis direction loop coil group 104a and the Y-axis direction loop coil group 104b by the pen signal transmitted from the position indicator 2. The control unit 120 detects the pen pressure based on the phase difference between the transmitted transmission signal and the received pen signal.

[0090] <Processing of the position detector 1> The processing of the position detector 1 according to the present embodiment will be described with reference to FIGS. 17 and 6. Hereinafter, the description will be divided into the case where the process starts when there is a change in the frequency / phase information of the RX signal and the case where the process starts at the timing before the coordinate calculation process of the position indicator 2.

[0091] <Case where the process starts when there is a change in the frequency / phase information of the RX signal> The case where the process starts when there is a change in the frequency / phase information of the RX signal will be described with reference to FIG. 17.

[0092] The control unit 120 causes the signal reception unit to receive the RX signal from the position indicator 2 (step S110). The RX signal received by the signal reception unit is converted into a desired digital signal and sent to the frequency analysis unit 113 via the control unit 120.

[0093] The frequency analysis unit 113 receives the RX signal converted into a digital signal and executes a discrete Fourier transform process. The frequency analysis unit 113 sends frequency / phase information of the RX signal to the control unit 120 as a result of the discrete Fourier transform processing (step S120). At this time, the control unit 120 stores the frequency / phase information of the RX signal obtained from the frequency analysis unit 113 in a memory.

[0094] The control unit 120 compares the frequency / phase information of the past RX signal with the frequency / phase information of the RX signal currently obtained from the frequency analysis unit 113, and determines whether or not there has been a change in the frequency / phase information of the RX signal (step S130A).

[0095] The control unit 120 compares the past frequency / phase information of the RX signal with the frequency / phase information of the RX signal obtained from the frequency analysis unit 113, and if it determines that there has been a change in the frequency / phase information of the RX signal ("YES" in step S130A), it transmits the frequency / phase information of the RX signal from the frequency analysis unit 113 to the multiplexer 110B, and the multiplexer 110B receives the transmitted frequency / phase information of the RX signal (step S140).

[0096] On the other hand, the control unit 120 compares the frequency / phase information of the RX signal in the memory with the frequency / phase information of the RX signal obtained from the frequency analysis unit 113, and if it determines that there has been no change in the frequency / phase information of the RX signal ("NO" in step S130A), it does not perform the processing of step S140, but performs the processing of step S150 described below.

[0097] The signal generating section 110A generates a plurality of transmission signals with different frequencies. The multiplexer 110B receives a plurality of transmission signals with different frequencies from the signal generating unit 110A, multiplexes them, and outputs a TX signal that corresponds to the frequency / phase of the RX signal received from the frequency analyzing unit 113 (step S150).

[0098] The control unit 120 causes the position indicator 2 to transmit a TX signal via the signal transmitting unit. The TX signal output from the control unit 120 is transmitted to the position detection coil 101 of the position indicator 2 via the switching connection circuit 107 (step S160).

[0099] <When starting processing before the coordinate calculation processing of the position indicator 2> A case where the process is started at a timing before the coordinate calculation process of the position indicator 2 will be described with reference to FIG.

[0100] The control unit 120 causes the signal receiving unit to receive the RX signal from the position indicator 2 (step S110). The RX signal received by the control unit 120 is converted into a desired digital signal.

[0101] The control unit 120 determines whether or not the current processing mode is the timing before the coordinate detection processing (step S170). If the control unit 120 determines that the current processing mode is not the timing before the coordinate detection processing ("NO" in step S170), it returns the processing to the original state and transitions to the standby mode.

[0102] When the control unit 120 determines that the current processing mode is the timing before the coordinate detection processing ("YES" in step S170), the RX signal received by the signal receiving unit is converted into a desired digital signal and sent to the frequency analysis unit 113 via the control unit 120.

[0103] The frequency analysis unit 113 receives the RX signal converted into a digital signal from the control unit 120 and executes a discrete Fourier transform process. The frequency analysis unit 113 sends frequency / phase information of the RX signal to the multiplexer 110B as a result of the discrete Fourier transform processing (step S120). At this time, the control unit 120 stores the frequency / phase information of the RX signal obtained from the frequency analysis unit 113 in a memory.

[0104] The multiplexer 110B receives the frequency / phase information of the RX signal from the frequency analysis unit 113 (step S140).

[0105] The signal generating section 110A generates a plurality of transmission signals with different frequencies. The multiplexer 110B receives a plurality of transmission signals with different frequencies from the signal generating unit 110A, multiplexes them, and outputs a TX signal that corresponds to the frequency / phase of the RX signal received from the frequency analyzing unit 113 (step S150).

[0106] The control unit 120 causes the position indicator 2 to transmit a TX signal via the signal transmitting unit. The TX signal output from the control unit 120 is transmitted to the position detection coil 101 of the position indicator 2 via the switching connection circuit 107 (step S160).

[0107] <Actions and Effects> As described above, the position detector 1 according to this embodiment includes a sensor having a plurality of electrodes (e.g., the X-axis direction loop coil group 104a and the Y-axis direction loop coil group 104b), and a signal processing circuit 102 connected to the sensor (e.g., the X-axis direction loop coil group 104a and the Y-axis direction loop coil group 104b), which detects a pen signal generated by the position indicator 2, generates a transmission signal of a different frequency according to the frequency of the detected pen signal, and transmits an alternating magnetic field to the position indicator 2 via the sensor (e.g., the X-axis direction loop coil group 104a and the Y-axis direction loop coil group 104b). In other words, the signal processing circuit 102 of the position detector 1 in this embodiment detects the pen signal generated by the position indicator 2, generates a transmission signal of a different frequency depending on the frequency of the detected pen signal, and transmits an alternating magnetic field to the position indicator 2 via sensors (e.g., X-axis loop coil group 104a and Y-axis loop coil group 104b). For example, the position detector 1 according to this embodiment generates and transmits to the position indicator 2 transmission signals of different frequencies depending on the behavior of the position indicator 2, for example, the presence or absence of writing pressure on the position indicator 2. More specifically, the position detector 1 of this embodiment transmits to the position indicator 2 a transmission signal having a frequency corresponding to the frequency transmitted from the position indicator 2, as shown in FIG. 4(A), for example. Therefore, the resonant energy supplied to the position indicator 2 is maintained regardless of whether or not there is pen pressure on the position indicator 2, and the amplitude of the voltage waveform sent from the position indicator 2 is also maintained, as shown in Figure 4 (B). In addition, in the conventional position indicator 2, the resonance frequency f' pen When the position indicator 2 becomes TX However, only the resonance energy due to the frequency characteristic of the resonance signal was obtained, and the resonance signal was attenuated. In this embodiment, as shown in FIG. 7(A) and FIG. 7(B), the position indicator 2 is TX Since it is possible to obtain resonance energy due to the frequency characteristic, it is possible to obtain a resonance signal equivalent to that in the absence of pen pressure without attenuating the resonance signal. Therefore, even if writing pressure is applied to the position indicator 2, a decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the position detection accuracy of the position indicator can be suppressed. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the detection accuracy of the writing pressure in the position indicator 2 can be suppressed. Since the resonance energy supplied to the position indicator 2 is optimized, improvement in the position detection accuracy can be expected, for example, even for the position indicator 2 in a hover state. Because the resonant energy supplied to the position indicator 2 is optimized, even if, for example, a magnet or a metal casing deteriorates over time, or the values ​​of the position indication coil and resonant capacitor that form the resonant circuit in the position indicator 2 change due to environmental conditions, etc., a decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed.

[0108] When the frequency of the pen signal generated by the position indicator 2 changes with respect to the frequency of the detected pen signal, the signal processing circuit 102 of the position detector 1 according to this embodiment generates an output signal that follows the change in frequency. That is, the signal processing circuit 102 of the position detector 1 according to this embodiment generates a transmission signal that follows the change in frequency of the pen signal generated by the position indicator 2. For example, the position detector 1 according to this embodiment generates an output signal that follows the behavior of the position indicator 2, for example, a frequency that changes depending on the presence or absence of writing pressure on the position indicator 2. More specifically, the position detector 1 of this embodiment transmits to the position indicator 2 a transmission signal having a frequency corresponding to the frequency transmitted from the position indicator 2, as shown in FIG. 4(A), for example. Therefore, the resonant energy supplied to the position indicator 2 is maintained regardless of whether or not there is pen pressure on the position indicator 2, and the amplitude of the voltage waveform sent from the position indicator 2 is also maintained, as shown in Figure 4 (B). In addition, in the conventional position indicator 2, the resonance frequency f' pen When the position indicator 2 becomes TX However, only the resonance energy due to the frequency characteristic of the resonance signal was obtained, and the resonance signal was attenuated. In this embodiment, as shown in FIG. 7(A) and FIG. 7(B), the position indicator 2 is f" TX Since it is possible to obtain resonance energy due to the frequency characteristic, it is possible to obtain a resonance signal equivalent to that in the absence of pen pressure without attenuating the resonance signal. Therefore, even if writing pressure is applied to the position indicator 2, a decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the position detection accuracy of the position indicator can be suppressed. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the detection accuracy of the writing pressure in the position indicator 2 can be suppressed.

[0109] The signal processing circuit 102 of the position detector 1 according to this embodiment generates a transmission signal at a timing before the coordinate calculation process of the position indicator 2 starts. In other words, a decrease in the S / N ratio of the pen signal sent from the position indicator 2 has the greatest effect on the coordinate calculation process of the position indicator 2. However, in the signal processing circuit 102 of the position detector 1 according to this embodiment, a transmission signal is generated at a timing before the coordinate calculation process of the position indicator 2 starts. Therefore, in the coordinate calculation process of the position indicator 2, the coordinate calculation process can be executed using the pen signal sent from the position indicator 2 in which the decrease in S / N is suppressed. Moreover, in the signal processing circuit 102 of the position detector 1 according to this embodiment, a transmission signal is generated at a timing before the coordinate calculation process of the position indicator 2 starts. Therefore, by optimizing the start-up timing of the waveform generating section 110 and the D / A conversion circuit 109, the power consumption of the waveform generating section 110 and the D / A conversion circuit 109 can be minimized. Therefore, even if writing pressure is applied to the position indicator 2, it is possible to suppress a decrease in the S / N ratio of the pen signal sent from the position indicator 2 while minimizing power consumption. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the position detection accuracy of the position indicator can be suppressed. Since the decrease in the S / N ratio of the pen signal sent from the position indicator 2 can be suppressed, the decrease in the detection accuracy of the writing pressure in the position indicator 2 can be suppressed.

[0110] The signal processing circuit 102 of the position detector 1 according to this embodiment generates a transmission signal multiple times in one coordinate calculation process, and generates a transmission signal at the same frequency continuously during the multiple times that at least one coordinate calculation process is performed. For example, when calculating the coordinates of a position indicator 2 existing in an N×N area within a sensor, in one coordinate calculation process, sensing is performed on N X sensors and N Y sensors, that is, the process of generating transmission signals is performed multiple times, and the coordinate calculation process is executed based on the reception intensity distribution of the sensors. Here, if the frequency of the transmission signal is changed during sensing of the N X sensors and the N Y sensors, that is, during multiple times when one coordinate calculation process is performed, the amplitude level of the pen signal will change, and there is a possibility that accurate coordinates cannot be calculated. Therefore, the signal processing circuit 102 generates a transmission signal multiple times in one coordinate calculation process, and by continuously generating a transmission signal at the same frequency during the multiple times that at least one coordinate calculation process is performed, it is possible to prevent adverse effects caused by dynamically changing the frequency.

[0111] In the above embodiment, the sensor is illustrated as having rectangular coils arranged crosswise in a two-dimensional space in a first direction and a second direction on a single substrate, but this is not limited to this. For example, it has been described that the transmission coil for generating an alternating magnetic field for the position indicator 2 and the detection coil for detecting the pen signal generated by the position indicator 2 are the same coil and used in a time-division manner, but these may also be separate coils.

[0112] Also, for example, the transmission coil and the detection coil may be provided separately on different substrates. In this case, a pen signal may be detected by a detection coil in one layer, and an alternating magnetic field having a frequency corresponding to (tracking) the detected frequency may be generated from a transmission coil provided in another layer.

[0113] Furthermore, the coils are not limited to being rectangular and arranged in two directions, and for example, block-shaped coils may be arranged two-dimensionally to cover the detection surface.

[0114] Furthermore, the multiple electrodes constituting the sensor do not necessarily have a loop-like coil shape, and may be part of an electrode that electromagnetically forms a coil. For example, specific examples include a comb-shaped coil and two wires functioning as a pseudo coil.

[0115] The position detectors 1, 1A, 1B of the present invention can be realized by recording the processing of the control units 120, 120A, 120B in a recording medium readable by a computer system, and having the control units 120, 120A, 120B read and execute the programs recorded in the recording medium. The computer system here includes hardware such as an OS and peripheral devices.

[0116] Furthermore, "computer system" also includes the homepage providing environment (or display environment) if a WWW (World Wide Web) system is used. The above program may be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium, or by transmission waves in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has the function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

[0117] The program may be for implementing some of the functions described above, or may be a so-called differential file (differential program) that can implement the functions described above in combination with a program already recorded in the computer system.

[0118] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of the present invention are also included. For example, the position indicator 2 exemplified in the first to fourth embodiments includes an electronic pen, a stylus, and the like, but the shape is not necessarily limited to a pen type.

[0119] <Additional notes> one or more processors; one or more memories communicatively connected to the one or more processors; a coil configured to function as a sensor, the coil including a transmission coil that transmits an alternating magnetic field to a position indicator based on a transmission signal; Equipped with The one or more processors: a signal processing circuit connected to the coil, for detecting a pen signal generated by the position indicator, for generating the transmission signal having a frequency based on frequency information of the detected pen signal, and for transmitting the transmission signal to the transmission coil; a position detector including: [Explanation of symbols]

[0120] 1; Position detector 1A; Position detector 1B; Position detector 2;Position indicator 101: Position detection coil 102: Signal processing circuit 104a: X-axis direction loop coil group 104b: Y-axis direction loop coil group 106; Selection circuit 107; Switching connection circuit 108;Transmitting amplifier 109;D / A conversion circuit 110;Waveform generation section 110A: Signal generating section 110B; Multiplexer 111; Receiving amplifier 112: A / D conversion circuit 113: Frequency analysis section 113A: Frequency analysis section 113B: Frequency analysis section 120; Control section

Claims

1. A coil configured to function as a sensor, the coil including a transmission coil for transmitting an alternating magnetic field based on a transmission signal to the position indicator; a signal processing circuit connected to the coil, for detecting a pen signal generated by the position indicator, for generating the transmission signal having a frequency based on frequency information of the detected pen signal, and for transmitting the transmission signal to the transmission coil; a position detector including

2. 2. The position detector according to claim 1, wherein, when the frequency of the pen signal generated by the position indicator changes with respect to the frequency of the detected pen signal, the signal processing circuit generates the transmission signal in accordance with the change in frequency.

3. 3. The position detector according to claim 2, wherein the signal processing circuit generates the transmission signal at a timing before the start of a coordinate calculation process for the position indicator.

4. the signal processing circuit generates the transmission signal a plurality of times in one coordinate calculation process, 4. The position detector according to claim 3, wherein the transmission signal is generated at the same frequency continuously during the plurality of times in which the coordinate calculation process is performed at least once.

5. 2. The position detector according to claim 1, wherein the signal processing circuit performs frequency analysis on a plurality of discrete frequencies, and extracts, from among the discrete values ​​of frequency detection, the discrete value that is closest to the discrete value at which the crest value of the pen signal received from the position indicator shows a peak, as the frequency.

6. 6. The position detector according to claim 5, wherein, when the frequency indicating a peak of the crest value of the pen signal received from the position indicator does not match a discrete value of the frequency detection, the signal processing circuit performs an interpolation operation between the frequency indicating the peak of the crest value and an adjacent discrete value of the frequency detection to extract the frequency.

7. An integrated circuit for detecting a position indicated by a position indicator, The integrated circuit is configured to function as a sensor with a plurality of electrodes, and is connected to coils including a transmission coil that transmits an alternating magnetic field to the position indicator based on a transmission signal; an integrated circuit that detects a pen signal generated by the position indicator, generates a transmission signal having a frequency based on frequency information of the detected pen signal, and transmits an alternating magnetic field to the position indicator via the coil.

8. A position detection method for a position detector, comprising: a first step in which the position detector transmits a first signal to a position indicator; a second step in which the position indicator transmits a second signal to the position detector; a third step of detecting frequency information from the second signal by the position detector; a fourth step in which the position detector generates a third signal having a different frequency from the first signal based on the frequency information detected in the third step; a fifth step in which the position detector transmits the third signal generated in the fourth step to the position indicator; A position detection method comprising:

9. a detection coil configured to function as a sensor; a sending coil for sending an alternating magnetic field to a position indicator based on a sending signal; a signal processing circuit connected to the detection coil and the transmission coil, for detecting a pen signal generated by the position indicator, generating the transmission signal having a frequency based on frequency information of the detected pen signal, and transmitting the transmission signal to the transmission coil; a position detector including

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