Electromagnetic induction pen, integrated circuit and position detection device

Abstract

The present invention improves the detection accuracy of a value indicating the behavior of a user compared to the prior art. An electromagnetic induction pen is provided with: a first resonance circuit (R1) configured so as to include a coil (L) and a capacitor (C); and a variable capacitance capacitor (CSW) connected to the first resonant circuit (R1). The variable capacitance capacitor (CSW) is a change element that changes the resonance frequency of a second resonance circuit (R2) configured so as to include the variable capacitance capacitor (CSW) and the first resonance circuit (R1) in association with the behavior of the user, and the electromagnetic induction pen is further provided with a switching circuit (43). And a switching circuit (43) that switches between the transmission of the reference alternating magnetic field using the first resonance circuit (R1) and the transmission of the modulated alternating magnetic field using the second resonance circuit (R2).

Description

Technical Field

[0001] The invention relates to an electromagnetic induction pen, an integrated circuit and a position detection device. Background Art

[0002] It is known that there is an electromagnetic induction pen that is configured to be able to switch between a first resonant circuit formed by connecting an inductance element and an electrostatic capacitance element in series and a second resonant circuit formed by adding a variable capacitance element to the first resonant circuit, and is configured to send out an alternating magnetic field from either resonant circuit. The variable capacitance element is configured such that the capacitance changes due to the pen pressure (pressure applied to the pen tip) of the electromagnetic induction pen, and is connected in parallel with the electrostatic capacitance element constituting the first resonant circuit. Hereinafter, the alternating magnetic field sent out by the electromagnetic induction pen using the first resonant circuit is referred to as a "reference alternating magnetic field", and the alternating magnetic field sent out by the electromagnetic induction pen using the second resonant circuit is referred to as a "modulated alternating magnetic field".

[0003] The position detection device for detecting the position of such an electromagnetic induction pen is configured to store the frequency of a reference alternating magnetic field sent from the electromagnetic induction pen operating using a first resonance circuit as a reference frequency, and detect the pen pressure based on the difference between the frequency of a modulated alternating magnetic field sent from the electromagnetic induction pen operating using a second resonance circuit and the stored reference frequency. By doing so, even if the resonance frequency (=reference frequency) of the first resonance circuit changes due to the presence of metal near the electromagnetic induction pen, etc., the pen pressure of the electromagnetic induction pen can be detected with high accuracy.

[0004] An example of such an electromagnetic induction pen and position detection device is disclosed in Patent Document 1. The electromagnetic induction pen (position indicator) described in the document is configured to have a normally open junction field effect transistor (JFET) connected in series with the above-mentioned variable capacitance element, and when the alternating magnetic field from the position detection device continues for a certain period of time, the JFET becomes disconnected. Thus, the position detection device of Patent Document 1 can make the electromagnetic induction pen send out a reference alternating magnetic field by making the sending of the alternating magnetic field continue for a specified period of time.

[0005] In addition, Patent Document 1 also discloses: a switch circuit is provided to short-circuit the first resonant circuit, and the switch circuit is controlled to be on when the transmission bit is "0", and the switch circuit is controlled to be off when the transmission bit is "1", thereby enabling digital data to be sent from the electromagnetic induction pen to the position detection device through on-off keying.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: International Publication No. 2016 / 056299 Summary of the invention

[0009] Problems to be solved by the invention

[0010] However, according to the structure described in Patent Document 1, in order for the electromagnetic induction pen to send out a reference alternating magnetic field, the position detection device must continue to send out the alternating magnetic field for more than a specified time. The reference frequency sometimes changes in a time shorter than the specified time. In addition, it is not possible to frequently send out the alternating magnetic field for a long time. Therefore, in the structure described in Patent Document 1, there is the following situation: the reference frequency stored in the position detection device deviates from the actual reference frequency value at the timing of receiving the modulated alternating magnetic field, and as a result, the detection accuracy of the pen pressure decreases. The same is true when the capacitance of the variable capacitance element is changed by using a value other than the pen pressure that represents the user's behavior (such as a value representing the grip pressure of the shell), and the detection accuracy of this value sometimes decreases.

[0011] Therefore, one of the objects of the present invention is to provide an electromagnetic induction pen and an integrated circuit capable of improving the detection accuracy of a value representing a user's behavior compared with conventional ones.

[0012] In addition, according to the structure of Patent Document 1, even when no pressure is applied to the pen tip, the above-mentioned difference (the difference between the frequency of the modulated alternating magnetic field and the reference frequency) sometimes does not become the specified value (usually 0, hereinafter referred to as the "hover indication value") indicating that no pressure is applied to the pen tip. This is caused by the frequency of the alternating magnetic field sent from the electromagnetic induction pen always slightly vibrating due to the self-capacitance of the above-mentioned JFET, external factors, etc., and the processing for substantially determining whether pressure is applied to the pen tip must be installed in the drawing application, so it needs to be improved.

[0013] Therefore, another object of the present invention is to provide a position detection device that can make the difference between the frequency of the reference alternating magnetic field and the frequency of the modulated alternating magnetic field a hovering indication value without applying pressure to the pen tip.

[0014] Furthermore, according to the configuration of Patent Document 1, when the switch circuit is turned on to transmit a bit "0", the electromagnetic induction pen is in a state where no alternating magnetic field is transmitted. This state is disadvantageous and needs to be improved.

[0015] Therefore, another object of the present invention is to provide an electromagnetic induction pen and a position detection device that can maintain the state of the alternating magnetic field from the electromagnetic induction pen even when sending digital data.

[0016] In addition, according to the structure of Patent Document 1, in the embodiment where the electromagnetic induction pen sends the identification signal ID ( Fig.11), the position detection device receives the alternating magnetic field (including the alternating magnetic field for detecting the pen pressure and the alternating magnetic field for receiving the identification signal ID) from the electromagnetic induction pen during the transmission of the burst signal. However, in this structure, the burst signal overlaps with the alternating magnetic field from the electromagnetic induction pen, so sometimes the detection of the pen pressure and the reception of the identification signal ID fail.

[0017] Therefore, another object of the present invention is to provide an electromagnetic induction pen that can prevent a position detection device from failing in detecting an analog operation amount and receiving digital data sent by the electromagnetic induction pen.

[0018] Solutions to Solve Problems

[0019] The electromagnetic induction pen of the first aspect of the present invention includes: a first resonant circuit, which is configured to include an inductance element and an electrostatic capacitance element; and a variation element, which is connected to the first resonant circuit, wherein the variation element is an element that causes the resonant frequency of a second resonant circuit, which is configured to include the variation element and the first resonant circuit, to change in association with the user's behavior, and the electromagnetic induction pen also includes a switching circuit, which switches between the sending of a reference alternating magnetic field using the first resonant circuit and the sending of a modulated alternating magnetic field using the second resonant circuit.

[0020] The integrated circuit of the second aspect of the present invention is an integrated circuit for a position detection device, which receives an alternating magnetic field from an electromagnetic induction pen, wherein the electromagnetic induction pen includes: a first resonant circuit, which is configured to include an inductance element and an electrostatic capacitance element; and a variation element, which is connected to the first resonant circuit, wherein the variation element is an element that changes the resonant frequency of a second resonant circuit, which is configured to include the variation element and the first resonant circuit, in association with the behavior of a user, wherein the alternating magnetic field is a reference alternating magnetic field generated using the first resonant circuit or a modulated alternating magnetic field generated using the second resonant circuit, wherein the integrated circuit determines whether the received alternating magnetic field is the reference alternating magnetic field or the modulated alternating magnetic field, and outputs a digital value corresponding to an analog quantity represented by the modulated alternating magnetic field based on the reception result of the alternating magnetic field determined to be the reference alternating magnetic field.

[0021] The position detection device of the third aspect of the present invention receives a reference alternating magnetic field and a modulated alternating magnetic field respectively from an electromagnetic induction pen, the electromagnetic induction pen comprising: a first resonant circuit, constituted to include an inductance element and an electrostatic capacitance element; and a variation element, connected to the first resonant circuit, the variation element being an element that changes the resonant frequency of a second resonant circuit constituted to include the variation element and the first resonant circuit in association with the behavior of a user, the reference alternating magnetic field being generated using the first resonant circuit, the modulated alternating magnetic field being generated using the second resonant circuit, the position detection device obtaining a first output based on the reference alternating magnetic field, obtaining a second output based on the modulated alternating magnetic field, obtaining a third output by adding or subtracting a specified offset amount from the difference between the first output and the second output, and converting the third output into a digital value using a specified conversion rule.

[0022] The electromagnetic induction pen of the fourth aspect of the present invention includes: a first resonant circuit, which is configured to include an inductance element and an electrostatic capacitance element; and a variation element, which is connected to the first resonant circuit, and the variation element is an element that causes the resonant frequency of a second resonant circuit, which is configured to include the variation element and the first resonant circuit, to change in association with the user's behavior. The electromagnetic induction pen also includes a processing circuit, which switches between the sending of a reference alternating magnetic field using the first resonant circuit and the sending of a modulated alternating magnetic field using the second resonant circuit based on a bit value sent to a position detection device.

[0023] The position detection device of the fourth aspect of the present invention receives an alternating magnetic field from an electromagnetic induction pen, wherein the electromagnetic induction pen includes: a first resonant circuit, which is configured to include an inductance element and an electrostatic capacitance element; and a variation element, which is connected to the first resonant circuit, wherein the variation element is an element that causes the resonant frequency of a second resonant circuit, which is configured to include the variation element and the first resonant circuit, to change in association with the user's behavior, wherein the alternating magnetic field is a reference alternating magnetic field generated using the first resonant circuit or a modulated alternating magnetic field generated using the second resonant circuit, wherein the position detection device determines whether the alternating magnetic field is the reference alternating magnetic field or the modulated alternating magnetic field, and obtains the bit value sent by the electromagnetic induction pen based on the result of the determination.

[0024] The electromagnetic induction pen according to the fifth aspect of the present invention performs a process of transmitting digital data by digital modulation and a process of transmitting an analog operation amount by analog modulation while the sensor controller is not sending an alternating magnetic field.

[0025] Effects of the Invention

[0026] According to the first and second aspects of the present invention, even if the position detection device does not send an alternating magnetic field for a predetermined time or longer, the electromagnetic induction pen can send a reference alternating magnetic field, thereby improving the detection accuracy of the value representing the user's behavior compared with the related art.

[0027] According to the third aspect of the present invention, since a specified bias amount is added to or subtracted from the difference between a first output obtained based on a reference alternating magnetic field and a second output obtained based on a modulated alternating magnetic field, the difference between the frequency of the reference alternating magnetic field and the frequency of the modulated alternating magnetic field can be made a hover indication value without applying pressure to the pen tip.

[0028] According to the fourth aspect of the present invention, bit values ​​can be transmitted by switching between sending out the reference alternating magnetic field and sending out the modulated alternating magnetic field. Therefore, the state of sending out the alternating magnetic field from the electromagnetic induction pen can be maintained even when transmitting digital data.

[0029] According to the fifth aspect of the present invention, since digital data and analog operation amount are sent during the period when the sensor controller does not send out the alternating magnetic field, it is possible to prevent the position detection device from failing in detecting the analog operation amount sent by the electromagnetic induction pen and receiving the digital data. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a diagram showing changes in the reference alternating magnetic field or the modulated alternating magnetic field when metal is brought close to or away from the panel surface of the position detection device while keeping the writing pressure constant.

[0031] Figure 2 It is a diagram showing the configuration of a position detection system 1 according to the first embodiment of the present invention.

[0032] Figure 3 It is a diagram for explaining the operation of the sensor controller 31 and the processing circuit 23 according to the first embodiment of the present invention.

[0033] Figure 4 is shown for reference Figure 3 FIG. 2 is a diagram showing the internal structure of the processing circuit 23 for explaining the operation.

[0034] Figure 5 4 is a diagram showing the detailed configuration of the detection circuit 41 and the wait detection circuit 42.

[0035] Figure 6 1 is a diagram showing simulation results of the electromotive force PE, the waveforms appearing at the output nodes n1 and n2, the clock signal Pen_clk, and the wait detection signal det_wait.

[0036] Figure 7This is a flowchart showing the processing performed by the sensor controller 31 according to the first embodiment of the present invention.

[0037] Figure 8 This is a flowchart showing the processing performed by the sensor controller 31 according to the first embodiment of the present invention.

[0038] Fig. 9 1 is a diagram showing measurement results of temporal changes in the modulation phase phCw, the reference phase phDh, the difference phCw-phDh, and the writing pressure value P acquired by the sensor controller 31 according to the first embodiment of the present invention.

[0039] Fig.10 It is a diagram showing the configuration of a position detection system 1 according to a second embodiment of the present invention.

[0040] Fig.11 It is a diagram for explaining the operation of the sensor controller 31 and the processing circuit 23 according to the second embodiment of the present invention.

[0041] Fig.12 is shown for reference Fig.11 FIG. 2 is a diagram showing the internal structure of the processing circuit 23 for explaining the operation.

[0042] Fig.13 4 is a diagram showing the detailed configuration of the detection circuit 41 , the wait detection circuit 42 , and the long burst detection circuit 44 .

[0043] Fig.14 1 is a diagram showing simulation results of the waveforms of the electromotive force PE, the output nodes n1 and n2, the clock signal Pen_clk, the wait detection signal det_wait, and the long burst detection signal det_lb.

[0044] Fig.15 3 is a diagram showing the internal structure of the timing generation circuit 45 .

[0045] Fig.16 This is a flowchart showing the processing performed by the sensor controller 31 according to the second embodiment of the present invention.

[0046] Fig.17 This is a flowchart showing the processing performed by the sensor controller 31 according to the second embodiment of the present invention.

[0047] Fig.18 It is shown in Fig.16 FIG. 1 is a diagram showing details of the digital data reception process performed in step S37.

[0048] Fig.19 1 is a diagram showing the internal structure of the electromagnetic induction pen 2 in the position detection system 1 according to the third embodiment of the present invention.

[0049] Fig. 20 1 is a flowchart showing a digital data reception process performed by the sensor controller 31 according to the third embodiment of the present invention.

[0050] Fig.21 It is a diagram for explaining the operation of the sensor controller 31 and the processing circuit 23 according to the fourth embodiment of the present invention.

[0051] Fig. 22 It is a diagram for explaining the operation of the sensor controller 31 and the processing circuit 23 according to the fourth embodiment of the present invention.

[0052] Fig.23 It is a diagram for explaining the operation of the sensor controller 31 and the processing circuit 23 according to the fourth embodiment of the present invention.

[0053] Fig.24 This is a flowchart showing the processing performed by the sensor controller 31 according to the fourth embodiment of the present invention.

[0054] Fig.25 This is a flowchart showing the processing performed by the sensor controller 31 according to the fourth embodiment of the present invention.

[0055] Fig.26 1 is a diagram showing a structure of an electromagnetic induction pen 2 according to a fifth embodiment of the present invention.

[0056] Fig. 27 (a) shows the value transmitted by the electromagnetic induction pen 2 according to the fifth embodiment of the present invention, the on / off state of the switch elements 24, 65 to 68, the capacitors C, C SW The combined capacitance C of the capacitors in C1 to C4 incorporated in the resonant circuit C and the resonant frequency f of the resonant circuit R A diagram of the relationship between Fig. 27 (b) shows the resonant frequency f corresponding to each transmission value on a straight line. R Graph of the values ​​of . DETAILED DESCRIPTION

[0057] First, the main subject of the present invention will be described again in detail. Figure 1 This is a diagram showing the change of the reference alternating magnetic field or the modulated alternating magnetic field when the metal is brought close to or away from the panel surface of the position detection device while the pen pressure is kept constant. It should be noted that in this figure, the vertical axis is the phase, which is based on the position detection device being configured to detect the change of the frequency by detecting the phase of the received signal. Hereinafter, the phase corresponding to the frequency of the reference alternating magnetic field is referred to as the "reference phase", and the phase corresponding to the frequency of the modulated alternating magnetic field is referred to as the "modulation phase", and the details of this point will be described later.

[0058] exist Figure 1 In FIG. 4 , the time period when the metal is brought close to the panel surface is shown by arrows (4). As can be understood from the results of this figure, if the metal is brought close to the panel surface, both the reference phase and the modulation phase change significantly. Moreover, the magnitude of the change in the reference phase and the modulation phase is not the same value, so the difference between them also changes. Therefore, although the original pen pressure is constant, the value of the pen pressure detected by the position detection device is not constant.

[0059] In addition, Figure 1 In the measurement results, even when no metal is brought close, the difference between the reference phase and the modulation phase has a slight vibration. This is caused by the self-capacitance of the switch used to switch the first resonant circuit and the second resonant circuit, noise from the outside, etc. The difference vibration means that the value of the pen pressure detected by the position detection device will also vibrate.

[0060] In this way, the phase (frequency) of the alternating magnetic field sent from the electromagnetic induction pen can easily change due to various reasons other than pen pressure. Moreover, such changes can also occur in a very short time, which will reduce the detection accuracy of the values ​​representing the user's behavior, headed by the pen pressure value. It will also become the main reason for the pen pressure to be generated even though the pen tip is not in contact with the panel surface. One of the subjects of the present invention is to improve these conditions. Below, with reference to the accompanying drawings, an embodiment of the present invention for solving such a problem is described in detail.

[0061] Figure 2 1 is a diagram showing a configuration of a position detection system 1 according to a first embodiment of the present invention. As shown in the diagram, the position detection system 1 is configured to include an electromagnetic induction pen 2 and a position detection device 3 each supporting an electromagnetic induction method (EMR method).

[0062] The electromagnetic induction pen 2 is a pen-shaped device including a core 20, a pressure sensor 21, a processing circuit 23, a coil (inductance element) L, a capacitor (static capacitance element) C, and a switch element 24. The pressure sensor 21 includes a variable capacitance capacitor C. SW The first resonant circuit R1 is composed of a coil L and a capacitor C. SW and the switching element 24 constitute a second resonance circuit R2.

[0063] The coil L and the capacitor C are connected in series with each other. SW The switch element 24 is connected in parallel with the capacitor C. SWThe switch element 24 is an on-off switch provided for switching the first resonant circuit R1 and the second resonant circuit R2, and is on-off controlled by the processing circuit 23. In a specific example, the switch element 24 is composed of a JFET. If the processing circuit 23 turns off the switch element 24, the variable capacitance capacitor C SW is disconnected from the circuit, and the first resonance circuit R1 becomes effective. On the other hand, if the processing circuit 23 turns on the switch element 24, the variable capacitance capacitor C SW Being incorporated into the circuit, the second resonant circuit R2 becomes effective.

[0064] Variable capacitance capacitor C SW It is an element (variable element) that plays a role in changing the resonance frequency of the second resonance circuit R2 in association with the user's behavior. SW Or with a variable capacitance capacitor C SW Use other types of variable elements such as variable inductors and variable resistors together.

[0065] In this embodiment, the user's action is to press the pen tip of the electromagnetic induction pen 2 against the panel surface. The pressure sensor 21 is a sensor for detecting the degree of this action, and is specifically configured as a variable capacitance capacitor C SW The capacitance of the variable capacitance capacitor C changes according to the pressure applied to the front end of the core 20 (hereinafter, the value of this pressure is referred to as "writing pressure value P"). The writing pressure value P is an analog quantity that changes continuously. SW The capacitance of the variable capacitance capacitor C also changes continuously. Therefore, it can be said that the transmission of the pen pressure value P by the electromagnetic induction pen 2 is based on analog modulation. It should be noted that other types of behaviors, such as the behavior of holding the side of the electromagnetic induction pen 2, can also be used as the user's behavior. In this case, the variable capacitance capacitor C SW Instead of being built into the pressure sensor 21, a sensor for detecting the extent of this behavior is built into it.

[0066] The position detection device 3 is a device including a plurality of loop coils LC, a switch unit 30, a sensor controller 31, and a host processor 32. A typical example of the position detection device 3 is a tablet terminal or a laptop computer whose display surface also serves as a touch surface, but the position detection device 3 may also be constituted by a digitizer or the like that does not have a display surface.

[0067] The plurality of loop coils LC are coils arranged in the touch surface, and are composed of a plurality of loop coils LCx arranged in the x direction and a plurality of loop coils LCy arranged in the y direction orthogonal to the x direction. One end of each loop coil LC is connected to the switch unit 30, and the other end of each loop coil LC is grounded. The switch unit 30 is a circuit that connects one or more of the plurality of loop coils LC to the sensor controller 31 according to the control of the sensor controller 31.

[0068] The sensor controller 31 is an integrated circuit having the following functions: detecting the position of the electromagnetic induction pen 2 within the touch surface, obtaining the pen pressure value P sent by the electromagnetic induction pen 2, and sequentially supplying the detected position and the obtained pen pressure value P to the host processor 32. In order to perform these processes, the sensor controller 31 is configured to sequentially or simultaneously drive the plurality of loop coils LCy (i.e., supply the drive current Tx thereto), and receive the induced current Rx appearing in the plurality of loop coils LCx.

[0069] If the sensor controller 31 supplies a driving current Tx to the annular coil LCy, an alternating magnetic field AM is generated on the touch surface. If the coil L of the electromagnetic induction pen 2 enters the alternating magnetic field AM, an electromotive force PE is generated at both ends of the coil L. At this time, the effective resonant circuit (the first resonant circuit R1 or the second resonant circuit R2) becomes a resonant state, and as a result, an alternating magnetic field PS (pen signal) is sent out from the electromagnetic induction pen 2. In the following, the alternating magnetic field PS sent out from the electromagnetic induction pen 2 when the first resonant circuit R1 is effective is sometimes referred to as a "reference alternating magnetic field PSS", and the alternating magnetic field PS sent out from the electromagnetic induction pen 2 when the second resonant circuit R2 is effective is sometimes referred to as a "modulated alternating magnetic field PSM". Ideally, the frequencies of the reference alternating magnetic field PSS and the modulated alternating magnetic field PSM are equal to the resonant frequencies of the first resonant circuit R1 and the second resonant circuit R2, respectively. If expressed in a specific mathematical formula, the frequency f1 of the reference alternating magnetic field PSS is expressed as f1=1 / (2π(LC) 1 / 2 ), the frequency f2 of the modulated alternating magnetic field PSM is expressed as f2=1 / (2π(L(C+C SW )) 1 / 2 ).

[0070] The sensor controller 31 is configured to receive the induced current Rx that appears in each of the plurality of loop coils LCx due to the alternating magnetic field PS, detect the position of the electromagnetic induction pen 2 within the touch surface based on the received result, and obtain the pen pressure value P sent by the electromagnetic induction pen 2. Specifically, the position of the electromagnetic induction pen 2 is detected based on the amplitude of the induced current Rx received by each loop coil LCx, and the pen pressure value P sent by the electromagnetic induction pen 2 is obtained based on the frequency of the induced current Rx (=the frequency of the alternating magnetic field PS).

[0071] Here, the specific process of obtaining the pen pressure value P based on the frequency of the induced current Rx is described. First, as a premise, the sensor controller 31 is configured to derive the phase of the induced current Rx at a specified frequency by performing a discrete Fourier transform (or a fast Fourier transform) of the induced current Rx during a specified period after the timing of ending the sending of the alternating magnetic field AM. The specified frequency is, for example, an ideal frequency (i.e., without considering the influence of parasitic capacitance and interference) of the reference alternating magnetic field PSS. The sending of the alternating magnetic field PS by the electromagnetic induction pen 2 starts at a known timing just after the sending of the alternating magnetic field AM ends, and therefore, the phase derived in this way becomes a value reflecting the frequency of the induced current Rx. Therefore, the sensor controller 31 obtains the derived phase as a value representing the frequency of the induced current Rx and obtains the pen pressure value P. Specifically, the sensor controller 31 stores the phase phDh (first output) derived at the timing of the electromagnetic induction pen 2 sending the reference alternating magnetic field PSS as the reference phase, and obtains the phase difference phCw-phDh by subtracting the reference phase from the phase phCw (modulation phase. Second output) derived at the timing of the electromagnetic induction pen 2 sending the modulated alternating magnetic field PSM. Then, the phase phCw-phDh-offset (third output) obtained by subtracting a given offset from the obtained difference phCw-phDh is converted into a digital value using a prescribed conversion rule, thereby obtaining the pen pressure value P sent by the electromagnetic induction pen 2.

[0072] The specific content of the prescribed transformation rule is as shown in the following formula (1). Among them, press in formula (1) is a variable determined by formula (2), and n is a prescribed numerical value greater than 1. Since n>1, the change in the pen pressure value P relative to the change in the amount of user behavior (here, the force of pressing the pen tip against the panel surface) increases as the amount of behavior increases. However, n>1 is not necessarily required, and n=1 or n<1 may also be required. In addition, PressMax in formula (2) is the maximum level of pen pressure value P (for example, 2047), and PhMax is the value of the phase phCw-phDh-offset when the maximum level of pen pressure is applied.

[0073]

[0074] The offset is used to absorb the small vibration that occurs in the difference between the reference phase and the modulation phase (refer to Figure 1). The larger the value of the offset is, the more vibration can be absorbed. However, if it is too large, the initial pen pressure becomes heavy (that is, it is impossible to draw without pressing the pen tip of the electromagnetic induction pen 2 firmly against the panel surface). On the contrary, if it is too small, so-called ink leakage will occur (the phenomenon of drawing even though no pen pressure is applied). In addition, the appropriate value of the offset is changed not only by the characteristics of the electromagnetic induction pen 2 and the position detection device 3, but also by the external environment such as the temperature. Therefore, the sensor controller 31 is configured to perform a calibration process while the electromagnetic induction pen 2 is hovering to adjust the value of the offset. Specifically, the sensor controller 31 derives the height (distance from the panel surface) of the electromagnetic induction pen 2 from the maximum amplitude of the induced current Rx appearing in the loop coil LCx, measures the difference phCw-phDh when the electromagnetic induction pen 2 is at a certain height or higher and it can be reliably considered that no pen pressure is applied, and determines the value of the offset so that the value obtained by subtracting the offset from the measured difference phCw-phDh becomes a predetermined value (e.g., -30). In this way, the minute vibration appearing in the difference phCw-phDh can be appropriately absorbed.

[0075] Figure 3 1 is a diagram for explaining the operation of the sensor controller 31 and the processing circuit 23 of the present embodiment. First, the sensor controller 31 is configured to operate in any of the three operation modes: Wait, D-Phase, and C-SW. The sensor controller 31 also has an initial setting mode, but the initial setting mode will be described later. Figure 7 The flowchart is used to illustrate.

[0076] The action mode Wait is a mode for causing the electromagnetic induction pen 2 to switch the sent alternating magnetic field (i.e., the on / off of the switch element 24). As will be described in detail later, the electromagnetic induction pen 2 is configured to switch the on / off of the switch element 24 upon detecting that the sensor controller 31 has entered the action mode Wait. The sensor controller 31 that has entered the action mode Wait does not supply the alternating current Tx to the ring coil LCy or receive the induced current Rx at the ring coil LCx within a predetermined time.

[0077] The action mode D-Phase is a mode for acquiring and storing a reference phase based on the reception result of the reference alternating magnetic field PSS sent by the electromagnetic induction pen 2. The sensor controller 31 that enters the action mode D-Phase repeatedly performs the process of supplying the alternating current Tx to the loop coil LCy for a predetermined number of times at intervals of a predetermined time T2 while changing the loop coil LCy for a predetermined number of times within a predetermined time T1. In addition, within the predetermined time T2 when the supply of the alternating current Tx is stopped, the phase of the induced current Rx appearing in the loop coil LCx is derived as described above, and the phase obtained as a result is stored as a reference phase.

[0078] The action mode C-SW is a mode for obtaining the pen pressure value P sent by the electromagnetic induction pen 2 based on the reception result of the modulated alternating magnetic field PSM sent by the electromagnetic induction pen 2. The sensor controller 31 that enters the action mode C-SW repeats the process of supplying the alternating current Tx to the annular coil LCy within the prescribed time T1 for a prescribed number of times at intervals of the prescribed time T2, as in the action mode D-Phase. In addition, within the prescribed time T2 when the supply of the alternating current Tx is stopped, the phase of the induced current Rx appearing in the annular coil LCx is derived as described above. Then, the pen pressure value P is derived based on the difference in phase obtained by subtracting the reference phase from the derived phase. The specific method of deriving the pen pressure value P is as described above.

[0079] Next, let's focus on the processing circuit 23. The waiting detection signal det_wait and the D-Phase enable signal EN_DP shown in the figure are signals generated by the processing circuit 23 according to the alternating magnetic field AM. The processing circuit 23 is configured to maintain the waiting detection signal det_wait high during the period of receiving the alternating magnetic field AM, and on the other hand, make the waiting detection signal det_wait low when a predetermined time has passed since the alternating magnetic field AM is no longer received. The predetermined time is set to a time length slightly shorter than the length of time when the sensor controller 31 enters the action mode Wait. Therefore, every time the sensor controller 31 enters the action mode Wait, the waiting detection signal det_wait temporarily changes to low.

[0080] In addition, the processing circuit 23 is configured to switch the value of the D-Phase enable signal EN_DP between high and low according to the wait detection signal det_wait becoming low. Furthermore, the processing circuit 23 is configured to turn off the switch element 24 when the D-Phase enable signal EN_DP is low, and turn on the switch element 24 when the D-Phase enable signal EN_DP is high. Thus, whenever the sensor controller 31 enters the operation mode Wait, the electromagnetic induction pen 2 operates while switching between the state of sending the reference alternating magnetic field PSS using the first resonant circuit R1 and the state of sending the modulated alternating magnetic field PSM using the second resonant circuit R2.

[0081] Figure 4 is shown for reference Figure 3 FIG. 2 is a diagram showing the internal structure of the processing circuit 23 for explaining the operation. As shown in the figure, the processing circuit 23 is configured to include a power supply circuit 40, a detection circuit 41, a wait detection circuit 42, and a toggle circuit 43.

[0082] The power supply circuit 40 is a circuit that uses the electromotive force PE generated in the first resonance circuit R1 by the alternating magnetic field AM to generate the power supply voltage VDD required for the operation of the processing circuit 23. The detection circuit 41 is a circuit that generates the clock signal Pen_clk based on the electromotive force PE, and the wait detection circuit 42 is a circuit that generates the wait detection signal det_wait based on the clock signal Pen_clk. The wait detection signal det_wait generated by the wait detection circuit 42 is supplied to the switching circuit 43.

[0083] Figure 5 4 is a diagram showing the detailed structure of the detection circuit 41 and the waiting detection circuit 42. As shown in the figure, the detection circuit 41 is configured to include a half-wave voltage doubler rectifier circuit 41a formed using a Schottky barrier diode, a voltage divider circuit 41b, a smoothing circuit 41c formed using a Schottky barrier diode, a voltage divider circuit 41d, an operational amplifier 41e, a resistor element 41f, an inverting buffer circuit 41g, an RC low-pass filter 41h, and an inverting buffer circuit 41i.

[0084] The half-wave voltage doubler rectifier circuit 41a, the voltage divider circuit 41b, the smoothing circuit 41c and the voltage divider circuit 41d are connected in series in sequence. The input node of the half-wave voltage doubler rectifier circuit 41a constitutes the input node of the detection circuit 41, and receives the supply of the electromotive force PE from the first resonant circuit R1. The non-inverting input terminal of the operational amplifier 41e is connected to the output node n1 of the voltage divider circuit 41b, and the inverting input terminal of the operational amplifier 41e is connected to the output node n2 of the voltage divider circuit 41d. The resistor element 41f, the inverting buffer circuit 41g, the RC low-pass filter 41h and the inverting buffer circuit 41i are connected in series in sequence between the output terminal of the operational amplifier 41e and the output node of the detection circuit 41. The signal output from the output node of the detection circuit 41 becomes Figure 4 The clock signal Pen_clk is shown.

[0085] In addition, the waiting detection circuit 42 is configured to include a resistor element 42a, a Schottky barrier diode 42b, a capacitor 42c, and a Schmitt trigger circuit 42d. The resistor element 42a is connected between the input node of the waiting detection circuit 42 to which the clock signal Pen_clk is input and the input terminal of the Schmitt trigger circuit 42d. The Schottky barrier diode 42b is connected in parallel with the resistor element 42a in a direction in which the anode is connected to the input node of the waiting detection circuit 42. The capacitor 42c is connected between the input terminal of the Schmitt trigger circuit 42d and the ground terminal. The output terminal of the Schmitt trigger circuit 42d constitutes the output node of the waiting detection circuit 42. The signal output from the output node of the waiting detection circuit 42 becomes Figure 4 The wait detection signal det_wait is shown.

[0086] Figure 6 1 is a diagram showing simulation results of the electromotive force PE, the waveforms appearing at the output nodes n1 and n2, the clock signal Pen_clk, and the wait detection signal det_wait. The upper part of the diagram shows the corresponding operation mode of the sensor controller 31.

[0087] Figure 6 The specified time T1, T2 and Figure 3 The electromotive force PE gradually increases within the predetermined time T1 during which the sensor controller 31 sends the alternating magnetic field AM. Figure 2 and Figure 4 The capacitor C shown is charged. When the predetermined time T1 has passed, the sensor controller 31 stops sending the alternating magnetic field AM and starts discharging the capacitor C. By this discharge, the alternating magnetic field PS is sent from the coil L. When the switch element 24 is turned on, the variable capacitance capacitor C SW It also becomes the object of this charging and discharging.

[0088] The waveform appearing at the output node n1 is a waveform obtained by rectifying and dividing the waveform of the electromotive force PE. In addition, the waveform appearing at the output node n2 is a waveform obtained by smoothing and dividing the waveform appearing at the output node n1. The clock signal Pen_clk is Figure 5 Under the action of the operational amplifier 41e shown, a binary signal is formed, which becomes high when the waveform appearing at the output node n1 is larger than the waveform appearing at the output node n2, and becomes low when the waveform appearing at the output node n1 is smaller than the waveform appearing at the output node n2. As a result, the clock signal Pen_clk generated in this way becomes high when the alternating magnetic field AM from the sensor controller 31 reaches the coil L, and becomes low when it does not reach.

[0089] The wait detection signal det_wait is a signal that is maintained at high level while the clock signal Pen_clk is high, but becomes low when a predetermined time or longer has passed since the clock signal Pen_clk became low. Figure 5 Specifically describing the operation of the wait detection circuit 42 for generating such a wait detection signal det_wait, when the clock signal Pen_clk is high, the current from the detector circuit 41 flows in through the Schottky barrier diode 42b, so that the potential of the electrode of the capacitor 42c on the detector circuit 41 side rises rapidly, and as a result, the wait detection signal det_wait, which is the output of the Schmitt trigger circuit 42d, also becomes high at substantially the same time as the clock signal Pen_clk becomes high. On the other hand, if the clock signal Pen_clk becomes low, the current flows from the capacitor 42c to the detector circuit 41 through the resistor 42a due to the discharge of the capacitor 42c. If the discharge of the capacitor 42c progresses and the input voltage of the Schmitt trigger circuit 42d becomes lower than a predetermined value, the wait detection signal det_wait, which is the output of the Schmitt trigger circuit 42d, changes to low. As a result of the operation of the wait detection circuit 42 as described above, the wait detection signal det_wait becomes the above-mentioned signal.

[0090] return Figure 4 The switching circuit 43 is a circuit for switching between a state of sending a reference alternating magnetic field PSS using the first resonant circuit R1 and a state of sending a modulated alternating magnetic field PSM using the second resonant circuit R2, and is configured as a D-type flip-flop circuit 43a. An inverted signal of the wait detection signal det_wait is supplied to the clock terminal of the flip-flop circuit 43a, and an inverted signal of the output terminal is supplied to the data terminal of the flip-flop circuit 43a. The output signal of the switching circuit 43 becomes Figure 3As shown in FIG. 1 , the D-Phase enable signal EN_DP is a signal that switches between high and low according to the change of the wait detection signal det_wait to low. Figure 4 As shown, the D-Phase enable signal EN_DP is supplied to the gate of the switch element 24, whereby at the falling edge of the wait detection signal det_wait, the sending of the reference alternating magnetic field PSS and the sending of the modulated alternating magnetic field PSM are switched.

[0091] Figure 7 and Figure 8 1 and 2 are flowcharts showing the processing performed by the sensor controller 31 of the present embodiment. Hereinafter, the operation of the sensor controller 31 of the present embodiment will be described in more detail with reference to these drawings.

[0092] First refer to Figure 7 The sensor controller 31 first enters the initial setting mode (step S1). The initial setting mode is an operation mode for grasping the timing of the electromagnetic induction pen 2 sending out the reference alternating magnetic field PSS and the modulated alternating magnetic field PSM.

[0093] The sensor controller 31 that has entered the initial setting mode performs the supply of the alternating current Tx to each loop coil LCy and the detection of the amplitude of the induced current Rx that appears in each loop coil LCx (step S2). It should be noted that if the sensor controller 31 has already detected the position of the electromagnetic induction pen 2 at this point in time, it is sufficient to perform step S2 only on a predetermined number of loop coils LCy and LCx that are near the detected position. This is explained in the steps S13 and S19 described later (see Figure 8 ), step S33 (refer to Fig.16 )、Step S41 (refer to Fig.17 ) is the same.

[0094] Next, the sensor controller 31 derives the position of the electromagnetic induction pen 2 based on the amplitude of the induced current Rx at each loop coil LCy detected in step S3, and outputs it to the host processor 32 (step S3). In addition, the sensor controller 31 derives the phase of the induced current Rx at the loop coil LCx with the largest amplitude detected in step S3 (step S4), and stores the derived phase (step S5).

[0095] After that, the sensor controller 31 determines whether the processing of steps S2 to S5 has been executed twice (step S6). As a result, if it is determined that the processing has not been executed twice, it waits for a predetermined time (step S7), and then returns to step S3 to repeat the processing. Step S7 is a process for switching the alternating magnetic field PS sent by the electromagnetic induction pen 2. The sensor controller 31 waits for a time that is the same as the duration of the action mode Wait without supplying the alternating current Tx to the ring coil LCy or receiving the induced current Rx at the ring coil LCx.

[0096] When it is determined in step S6 that the process has been performed twice, the sensor controller 31 determines whether the alternating magnetic field PS sent out by the electromagnetic induction pen 2 at last is the reference alternating magnetic field PSS or the modulated alternating magnetic field PSM based on the two phases stored in step S5 twice (steps S8 and S9). Specifically, the determination is made based on the magnitude of the two phases. Fig. 9 As shown in FIG. 1 , the modulation phase is a value larger than the reference phase regardless of whether there is a pen pressure or not. Therefore, the sensor controller 31 can distinguish the modulation phase from the reference phase based on the magnitude of the two phases. Furthermore, if the sensor controller 31 determines that the reference alternating magnetic field PSS is present, the processing proceeds to Figure 8 In step S10, if it is determined that the alternating magnetic field PSM is modulated, the processing proceeds to Figure 8 Step S17.

[0097] Move to Figure 8 In step S10, the sensor controller 31 stores the last derived phase as the reference phase. Then, the operation mode Wait is entered to wait for a predetermined time (step S11), and then the operation mode C-SW is entered (step S12), and the supply of the AC current Tx to each loop coil LCy and the detection of the amplitude of the induced current Rx appearing in each loop coil LCx are executed (step S13).

[0098] Next, the sensor controller 31 derives the position of the electromagnetic induction pen 2 based on the amplitude of the induced current Rx at each ring coil LCy detected in step S13, and outputs it to the host processor 32 (step S14). In addition, the sensor controller 31 derives the phase of the induced current Rx at the ring coil LCx with the largest amplitude detected in step S15 (step S16). Then, based on the derived phase and the reference phase stored in the most recent step S10, the pen pressure value P sent by the electromagnetic induction pen 2 is derived, and output to the host processor 32 (step S17). The specific method of deriving the pen pressure value P is as described above.

[0099] Next, the sensor controller 31 enters the action mode Wait again and waits for a specified time (step S17), and then enters the action mode D-Phase (step S18), executes the supply of AC current Tx to each circular coil LCy and detects the amplitude of the induced current Rx appearing in each circular coil LCx (step S19).

[0100] Next, the sensor controller 31 derives the position of the electromagnetic induction pen 2 based on the amplitude of the induced current Rx at each loop coil LCy detected in step S19, and outputs it to the host processor 32 (step S20). In addition, the sensor controller 31 derives the phase of the induced current Rx at the loop coil LCx with the largest amplitude detected in step S15 (step S21), and stores the derived phase as the reference phase (step S10). The subsequent processing is as described above, and the sensor controller 31 thereafter repeatedly executes the action mode Wait, the action mode C-SW, the action mode Wait, and the action mode D-Phase in sequence.

[0101] As described above, according to the position detection system 1 of this embodiment, even if the position detection device 3 does not send out the alternating magnetic field for a predetermined time or longer, the electromagnetic induction pen 2 can alternately send out the reference alternating magnetic field and the modulated alternating magnetic field. Therefore, the detection accuracy of the values ​​representing the user's behavior, such as the pen pressure value P, can be improved compared with the past.

[0102] In addition, according to the position detection system 1 of the present embodiment, since the sensor controller 31 determines the type of the alternating magnetic field PS (reference alternating magnetic field PSS or modulated alternating magnetic field PSM), the sensor controller 31 can correctly receive the reference alternating magnetic field PSS and the modulated alternating magnetic field PSM autonomously sent out by the electromagnetic induction pen 2 in a prescribed order. Therefore, unlike the second embodiment described later, it is not necessary for the sensor controller 31 to reset the order of sending the alternating magnetic field PS by the electromagnetic induction pen 2. Therefore, as the electromagnetic induction pen 2, in addition to the electromagnetic induction pen of the type that generates power based on the alternating magnetic field AM described in the present embodiment, an electromagnetic induction pen of the type that operates using power supplied from a built-in battery (that is, a type that performs one-way communication from the electromagnetic induction pen 2. EM method) can also be used. In the case of using the electromagnetic induction pen 2 of the latter type, the switching between sending out the reference alternating magnetic field PSS and sending out the modulated alternating magnetic field PSM in the electromagnetic induction pen 2 is not performed at the falling edge of the waiting detection signal det_wait, but is performed at the edge of the clock signal output from the built-in oscillator.

[0103] In addition, according to the position detection system 1 of this embodiment, since the offset is subtracted from the difference phCw-phDh, the difference between the frequency of the reference alternating magnetic field and the frequency of the modulated alternating magnetic field can be made into a hovering indication value when no pressure is applied to the pen tip of the electromagnetic induction pen 2. It should be noted that although the subtraction operation is performed in this embodiment, the offset may be added to the difference phCw-phDh according to the calculation method of the pen pressure value P, etc.

[0104] Fig. 9 1 is a diagram showing the measurement results of the time changes of the modulation phase phCw, the reference phase phDh, the difference phCw-phDh, and the writing pressure value P obtained in the sensor controller 31 of this embodiment. In this figure, the phase phCw becomes larger when the pen tip of the electromagnetic induction pen 2 is pressed against the panel surface. At other times, the pen tip of the electromagnetic induction pen 2 is separated from the panel surface (hovering state).

[0105] like Fig. 9 As shown, according to the position detection system 1 of this embodiment, although the difference phCw-phDh is not 0 during hovering, the pen pressure value P during hovering is 0. Therefore, it can be said that according to the position detection system 1 of this embodiment, it is not necessary to install a process for substantially determining whether pressure is applied to the pen tip in the drawing application.

[0106] It should be noted that, in this embodiment, the sensor controller 31 is configured to Figure 7 In step S5, the phase of the induced current Rx (the phase of the alternating magnetic field PS) is stored, and in step S8, the type of the alternating magnetic field PS sent by the electromagnetic induction pen 2 is determined based on the two stored phases. However, the sensor controller 31 may also Figure 7 In step S5, the frequency or amplitude of the induced current Rx (the frequency or amplitude of the alternating magnetic field PS) is stored, and in step S8, the type of the alternating magnetic field PS sent by the electromagnetic induction pen 2 is determined based on the two stored frequencies or amplitudes.

[0107] Alternatively, you can replace Figure 7 In steps S6, S8, and S9, when the phase (or frequency, amplitude) of the induced current Rx satisfies the specified conditions, it is determined whether the alternating magnetic field PS sent by the electromagnetic induction pen is the reference alternating magnetic field PSS. In this case, the sensor controller 31 repeatedly performs the processing of steps S2 to S5 with step S7 sandwiched therebetween until the determination result that it is the reference alternating magnetic field PSS appears, and when the determination result that it is the reference alternating magnetic field PSS appears, the processing proceeds to step S10.

[0108] Next, the position detection system 1 of the second embodiment of the present invention is described. The position detection system 1 of this embodiment is different from the position detection system 1 of the first embodiment in that the electromagnetic induction pen 2 sends digital data (a set of bit values ​​of "0" or "1") to the position detection device 3, and the position detection device 3 resets the order of sending the reference alternating magnetic field PSS and the modulated alternating magnetic field PSM sent by the electromagnetic induction pen 2. The other points are the same as the position detection system 1 of the first embodiment, so the following description will continue with the differences from the position detection system 1 of the first embodiment.

[0109] Fig.10 1 is a diagram showing the configuration of a position detection system 1 according to the present embodiment. Figure 2 The position detection system 1 shown is different in that the electromagnetic induction pen 2 has side switches 22 a and 22 b and the first resonance circuit R1 has a switch element 25 .

[0110] The side switches 22a and 22b are respectively on-off switches provided on the surface of the housing of the electromagnetic induction pen 2, and are configured to be able to be turned on and off by the user. The processing circuit 23 is configured to be able to obtain the on-off state of the side switches 22a and 22b as 1-bit on-off information. The processing circuit 23 of this embodiment is configured to have the following functions: in addition to the on-off information, 4-bit digital data representing the identification information (2-bit information) of the electromagnetic induction pen 2 written in advance into the processing circuit 23 is generated, and sent to the position detection device 3 at the timing specified by the position detection device 3.

[0111] The switch element 25 is an on-off switch connected in parallel with the capacitor C, and is controlled on and off by the processing circuit 23. In a specific example, the switch element 25 is composed of a JFET. The operation when the switch element 25 is off is as described in the first embodiment. If the processing circuit 23 turns on the switch element 25, the coil L is short-circuited, so the first resonant circuit R1 and the second resonant circuit R2 no longer function as resonant circuits, and the alternating magnetic field PS is no longer sent from the electromagnetic induction pen 2. The processing circuit 23 uses this to send the bit value. That is, when sending "1", the switch element 25 is controlled to be off, and on the other hand, when sending "0", the switch element 25 is controlled to be on. Therefore, when sending "1", as usual, an alternating magnetic field PS (reference alternating magnetic field PSS or modulated alternating magnetic field PSM) is sent from the electromagnetic induction pen 2. On the other hand, when sending "0", the alternating magnetic field PS is no longer sent from the electromagnetic induction pen 2. Therefore, the sensor controller 31 can use the on-off keying method, which is a kind of amplitude shift keying method, to demodulate the bit value sent by the electromagnetic induction pen 2.

[0112] Fig.112 is a diagram for explaining the operation of the sensor controller 31 and the processing circuit 23 of the present embodiment. The sensor controller 31 of the present embodiment is configured to include Figure 3 In addition to the three action modes Wait, D-Phase, and C-SW shown in the figure, the electromagnetic induction pen 2 can also be operated in the action modes LB and ID. It should be noted that, as described in detail below, in this embodiment, the position detection device 3 resets the order in which the electromagnetic induction pen 2 sends out the reference alternating magnetic field PSS and the modulated alternating magnetic field PSM. Therefore, in the sensor controller 31 of this embodiment, it is not necessary to Figure 7 The initial setting mode is shown.

[0113] The action mode LB is a mode for forcibly activating the first resonance circuit R1 in the electromagnetic induction pen 2 (i.e., disconnecting the switch element 24) so ​​as to reset the order of sending out the reference alternating magnetic field PSS and the modulated alternating magnetic field PSM by the electromagnetic induction pen 2 and to reset the 3-bit counter cnt_s (described later) provided in the electromagnetic induction pen 2. The sensor controller 31 which enters the action mode LB is Figure 3 The process of supplying the alternating current Tx to each annular coil LCy is continued for a predetermined time T3 which is longer than the predetermined time T1 and T2 shown. As a result, the alternating magnetic field AM is continuously sent from the panel surface for the predetermined time T3. Hereinafter, the alternating magnetic field AM sent in this way is referred to as a "long burst signal". The details will be described later. After the action mode LB, the first resonant circuit R1 in the electromagnetic induction pen 2 becomes effective. Therefore, the sensor controller 31 which has finished the action in the action mode LB enters the action mode D-Phase.

[0114] The action mode ID is a mode for causing the electromagnetic induction pen 2 to send digital data. The electromagnetic induction pen 2 is configured to send 1 bit of data (bit value) for one action mode ID using the on and off of the above-mentioned switch element 25. The data sent in this way is a discrete digital quantity, and therefore, the transmission is based on digital modulation. The sensor controller 31 demodulates the bit value sent by the electromagnetic induction pen 2 based on whether the induced current Rx is received after the alternating magnetic field AM is sent. As described above, the digital data sent by the electromagnetic induction pen 2 is 4-bit data, and therefore, the sensor controller 31 is configured to receive all of the 4-bit digital data by entering the action mode ID 4 times with the action mode Wait sandwiched therebetween.

[0115] The processing circuit 23 of the present embodiment is configured to operate using, in addition to the clock signal Pen_clk, the wait detection signal det_wait, and the D-Phase enable signal EN_DP described in the first embodiment, a long burst detection signal det_lb, a 3-bit counter cnt_s, a D-Phase detection signal det_dp, a digital data transmission period detection signal det_id, a first side switch selection signal sel_sw0, a second side switch selection signal sel_sw1, a first identification information selection signal sel_id0, a second identification information selection signal sel_id1, and a digital data transmission enable signal EN_ID.

[0116] As described in the first embodiment, the clock signal Pen_clk is a signal that becomes high when the alternating magnetic field AM from the sensor controller 31 reaches the coil L, and becomes low when it does not reach. The processing circuit 23 is configured to maintain the long burst detection signal det_lb at a low level when the clock signal Pen_clk is low, and on the other hand, to make the long burst detection signal det_lb high when the clock signal Pen_clk continues to be high for a predetermined time or more. Thus, the long burst detection signal det_lb becomes a signal that changes to a high level only when a long burst signal is received from the sensor controller 31.

[0117] The 3-bit counter cnt_s is a counter that defines the order of digital data sent by the electromagnetic induction pen 2. The processing circuit 23 is configured to reset the value of the 3-bit counter cnt_s to 0 when the long burst detection signal det_lb becomes high, and then increment the value of the 3-bit counter cnt_s by 1 each time the wait detection signal det_wait becomes low. This increment continues until the value of the 3-bit counter cnt_s becomes 4, and after becoming 4, the state of 4 is maintained until the long burst detection signal det_lb becomes high again.

[0118] The D-Phase detection signal det_dp is a signal indicating the switching timing of the resonant circuit. The processing circuit 23 is configured to, in principle, switch the value of the D-Phase detection signal det_dp between high and low according to the change of the waiting detection signal det_wait to low. However, the processing circuit 23 is configured not to switch the value of the D-Phase detection signal det_dp when the value of the 3-bit counter cnt_s is 1 to 3 and when the value of the 3-bit counter cnt_s becomes 4 and the waiting detection signal det_wait changes to low for the first time. This is to avoid the switching of the resonant circuit during the transmission of digital data. In addition, the processing circuit 23 is configured to make the value of the D-Phase detection signal det_dp high according to the change of the long burst detection signal det_lb to low. This is a structure for forcibly making the first resonant circuit R1 effective by using a long burst signal, thereby resetting the order in which the electromagnetic induction pen 2 sends out the reference alternating magnetic field PSS and the modulated alternating magnetic field PSM.

[0119] The digital data transmission period detection signal det_id is a signal indicating the transmission period of digital data. The processing circuit 23 is configured to make the value of the digital data transmission period detection signal det_id high when the waiting detection signal det_wait changes to low when the value of the 3-bit counter cnt_s is 0, and to make the value of the digital data transmission period detection signal det_id low when the waiting detection signal det_wait changes to low for the first time after the value of the 3-bit counter cnt_s is restored to 4.

[0120] The first side switch selection signal sel_sw0 indicates Fig.10 The processing circuit 23 is configured to make the first side switch selection signal sel_sw0 high for a predetermined time when the value of the 3-bit counter cnt_s changes to 1. In addition, the second side switch selection signal sel_sw1 is a signal indicating the timing of transmitting the on / off information of the side switch 22a shown. Fig.10 The processing circuit 23 is configured to make the second side switch selection signal sel_sw1 high for a predetermined time in response to the value of the 3-bit counter cnt_s changing to 2.

[0121] The first identification information selection signal sel_id0 and the second identification information selection signal sel_id1 are signals indicating the transmission timing of the first bit and the second bit of the identification information (2-bit information) of the electromagnetic induction pen 2. The processing circuit 23 is configured to make the first identification information selection signal sel_id0 high for a predetermined time when the value of the 3-bit counter cnt_s changes to 3. In addition, the processing circuit 23 is configured to make the second identification information selection signal sel_id1 high for a predetermined time when the value of the 3-bit counter cnt_s changes to 4.

[0122] The D-Phase enable signal EN_DP is Fig.10 The control signal of the switch element 24 shown in FIG. 24. The processing circuit 23 is configured to make the inverted signal of the D-Phase detection signal det_dp become the D-Phase enable signal EN_DP when the detection signal det_id is low during the digital data transmission, and to fix the D-Phase enable signal EN_DP to high when the detection signal det_id is high during the digital data transmission. By fixing the D-Phase enable signal EN_DP to high when the detection signal det_id is high during the digital data transmission, the transmission of digital data performed by the electromagnetic induction pen 2 is transmitted by on-off keying of the modulated alternating magnetic field PSM. The processing circuit 23 may also fix the D-Phase enable signal EN_DP to low when the detection signal det_id is high during the digital data transmission, in which case the transmission of digital data is performed by on-off keying of the reference alternating magnetic field PSS.

[0123] Digital data transmission enable signal EN_ID is Fig.10 The processing circuit 23 is configured to make the digital data transmission enable signal EN_ID low when the bit value to be transmitted is "1", and to make the digital data transmission enable signal EN_ID high when the bit value to be transmitted is "0". Thus, the control of the above-mentioned switch element 25 is realized (disconnected when "1" is transmitted, and connected when "0" is transmitted).

[0124] Fig.12 is shown for reference Fig.11FIG. 2 is a diagram of the internal structure of the processing circuit 23 for explaining the operation of the processing circuit 23. As shown in the figure, the processing circuit 23 of the present embodiment is configured to include a power supply circuit 40, a detection circuit 41, a wait detection circuit 42, a long burst detection circuit 44, a timing generation circuit 45, and four switch elements 46a to 46d. Among them, the power supply circuit 40, the detection circuit 41, and the wait detection circuit 42 are the same as the power supply circuit 40, the detection circuit 41, and the wait detection circuit 42 described in the first embodiment. The long burst detection circuit 44, the timing generation circuit 45, and the switch elements 46a to 46d are described in detail below.

[0125] The long burst detection circuit 44 generates a long burst detection signal det_lb based on the clock signal Pen_clk generated by the detection circuit 41. The long burst detection signal det_lb generated by the long burst detection circuit 44 is supplied to the timing generation circuit 45 together with the wait detection signal det_wait generated by the wait detection circuit 42.

[0126] Fig.13 4 is a diagram showing the detailed configuration of the detection circuit 41, the wait detection circuit 42, and the long burst detection circuit 44. This diagram is a diagram in which the configuration related to the long burst detection circuit 44 is added to Figure 5 The resulting picture.

[0127] The long burst detection circuit 44 is configured to include a resistor element 44a, a Schottky barrier diode 44b, a capacitor 44c, and a Schmitt trigger circuit 44d. The resistor element 44a is connected between the input node of the long burst detection circuit 44 to which the clock signal Pen_clk is input and the input terminal of the Schmitt trigger circuit 44d. The Schottky barrier diode 44b is connected in parallel with the resistor element 44a in a direction in which the cathode is connected to the input node of the long burst detection circuit 44. The capacitor 44c is connected between the input terminal of the Schmitt trigger circuit 44d and the ground terminal. The output terminal of the Schmitt trigger circuit 44d constitutes the output node of the long burst detection circuit 44. The signal output from the output node of the long burst detection circuit 44 becomes the above-mentioned long burst detection signal det_lb.

[0128] Fig.14 1 is a diagram showing simulation results of the waveforms of the electromotive force PE, the output nodes n1, n2, the clock signal Pen_clk, the wait detection signal det_wait, and the long burst detection signal det_lb. The upper part of the diagram shows the corresponding action mode of the sensor controller 31. Among them, "W" means the action mode Wait.

[0129] like Fig.14As shown in FIG. 1 , during the period when the sensor controller 31 enters the action mode LB and sends the long burst signal, the electromotive force PE maintains a constant amplitude, and the clock signal Pen_clk is kept high. If the period during which the clock signal Pen_clk is kept high exceeds a predetermined time, the long burst detection circuit 44 operates, as shown in FIG. Fig.14 As shown, the long burst detection signal det_lb changes to high.

[0130] If you refer to it again Fig.13 Specifically describing the generation of the long burst detection signal det_lb by the long burst detection circuit 44, when the clock signal Pen_clk is low, the current flows from the capacitor 44c to the detector circuit 41 through the Schottky barrier diode 44b by the discharge of the capacitor 44c. This discharge is performed quickly, so that at about the same time when the clock signal Pen_clk becomes low, the long burst detection signal det_lb as the output of the Schmitt trigger circuit 44d also becomes low. On the other hand, if the clock signal Pen_clk becomes high, the current from the detector circuit 41 flows through the resistor 44a, so that the potential of the electrode of the capacitor 44c on the detector circuit 41 side gradually rises. If this potential exceeds a certain value, the long burst detection signal det_lb as the output of the Schmitt trigger circuit 44d changes to high. As a result of the operation of the long burst detection circuit 44 as described above, the long burst detection signal det_lb becomes the above-mentioned signal.

[0131] return Fig.14 The waveform of the electromotive force PE when the sensor controller 31 enters the action mode ID becomes the same as the waveform when it enters the action mode D-Phase or the action mode C-SW. That is, the electromotive force PE gradually rises within the prescribed time T1 when the sensor controller 31 sends the alternating magnetic field AM. Figure 2 After a predetermined time T1 has passed, the sensor controller 31 stops sending the alternating magnetic field AM, and the capacitor C and the variable capacitor C SW Since the sensor controller 31 is configured to configure the action mode Wait before and after the action mode ID, Fig.14 As shown, before and after the action mode ID, the wait detection signal det_wait is activated to low.

[0132] return Fig.12The switch element 46a is a switch that is turned on when the side switch 22a is turned on, and is turned off when the side switch 22a is turned off. The power supply voltage VDD is supplied to one end of the switch element 46a from the power supply circuit 40, and the ground potential is supplied to the other end of the switch element 46a via the resistor element. The potential of the other end of the switch element 46a (the power supply voltage VDD when the switch element 46a is turned on, and the ground potential when the switch element 46a is turned off) is supplied to the timing generation circuit 45 as the switch information SW0.

[0133] Similarly, the switch element 46b is a switch that is turned on when the side switch 22b is turned on, and is turned off when the side switch 22b is turned off. The power supply voltage VDD is supplied to one end of the switch element 46b from the power supply circuit 40, and the ground potential is supplied to the other end of the switch element 46b via the resistor element. The potential of the other end of the switch element 46b (the power supply voltage VDD when the switch element 46b is turned on, and the ground potential when the switch element 46b is turned off) is supplied to the timing generation circuit 45 as the switch information SW1.

[0134] The switch element 46c is a switch that is turned on when the first bit of the identification information of the electromagnetic induction pen 2 is "1", and is turned off when the first bit of the identification information of the electromagnetic induction pen 2 is "0". The power supply voltage VDD is supplied to one end of the switch element 46c from the power supply circuit 40, and the ground potential is supplied to the other end of the switch element 46c via the resistor element. The potential of the other end of the switch element 46c (the power supply voltage VDD when the switch element 46c is turned on, and the ground potential when the switch element 46c is turned off) is supplied to the timing generation circuit 45 as the identification information ID0.

[0135] Similarly, the switch element 46d is a switch that is turned on when the second bit of the identification information of the electromagnetic induction pen 2 is "1", and is turned off when the second bit of the identification information of the electromagnetic induction pen 2 is "0". The power supply voltage VDD is supplied to one end of the switch element 46d from the power supply circuit 40, and the ground potential is supplied to the other end of the switch element 46d via the resistor element. The potential of the other end of the switch element 46d (the power supply voltage VDD when the switch element 46d is turned on, and the ground potential when the switch element 46d is turned off) is supplied to the timing generation circuit 45 as the identification information ID1.

[0136] The timing generation circuit 45 is a circuit that receives inputs of the wait detection signal det_wait, the long burst detection signal det_lb, the switch information SW0, SW1, and the identification information ID0, ID1, and generates a D-Phase enable signal EN_DP and a digital data transmission enable signal EN_ID. Fig.11 The 3-bit counter cnt_s, D-Phase detection signal det_dp, digital data transmission period detection signal det_id, first side switch selection signal sel_sw0, second side switch selection signal sel_sw1, first identification information selection signal sel_id0 and second identification information selection signal sel_id1 shown are generated or used inside the timing generation circuit 45.

[0137] Fig.15 1 is a diagram showing the internal structure of the timing generation circuit 45. As shown in the figure, the timing generation circuit 45 includes an adder 50, D-type flip-flop circuits 51, 53, 55, logic circuits 52, 54, 56, and AND circuits 57a to 57d, and an OR circuit 58.

[0138] The flip-flop circuit 51 is a circuit that outputs the value supplied to the data terminal from the output terminal when the clock terminal is activated. A 3-bit value is supplied to the data terminal of the flip-flop circuit 51 from the adder 50, and the output value of the flip-flop circuit 51 is Fig.11 The 3-bit counter cnt_s shown is supplied to the logic circuit 56 .

[0139] The adder 50 is a circuit that supplies a 3-bit value obtained by adding 1 to the 3-bit counter cnt_s output from the flip-flop circuit 51 to the data terminal of the flip-flop circuit 51. However, the adder 50 is configured to supply 4 to the data terminal of the flip-flop circuit 51 when the addition result becomes 5. Thus, the output value of the adder 50 is suppressed to an integer value of 4 or less.

[0140] The inverted signal of the wait detection signal det_wait is supplied to the clock terminal of the flip-flop circuit 51. Thus, the 3-bit counter cnt_s, which is the output value of the flip-flop circuit 51, increases by 1 each time the wait detection signal det_wait is activated to be low. However, since the output value of the adder 50 is suppressed to an integer value less than 4 as described above, the 3-bit counter cnt_s is also 4 at most. In addition, the inverted signal of the long burst detection signal det_lb is supplied to the reset terminal of the flip-flop circuit 51. Thus, if the long burst detection signal det_lb becomes high, the 3-bit counter cnt_s is reset to 0.

[0141] The flip-flop circuit 53 is similar to the flip-flop circuit 51. It is a circuit that outputs the value supplied to the data terminal from the output terminal when the clock terminal is activated. A 1-bit value is supplied to the data terminal of the flip-flop circuit 53 from the logic circuit 52, and the output value of the flip-flop circuit 53 is Fig.11 The D-Phase detection signal det_dp shown is supplied to the logic circuit 56 .

[0142] The logic circuit 52 is a circuit that inverts the output value (0 or 1) of the flip-flop circuit 53 and supplies it to the data terminal of the flip-flop circuit 53 only when the value of the 3-bit counter cnt_s is 4. In addition, similarly to the flip-flop circuit 51, an inverted signal of the wait detection signal det_wait is supplied to the clock terminal of the flip-flop circuit 53. Therefore, the value of the D-Phase detection signal det_dp is inverted between 0 and 1 every time the wait detection signal det_wait is activated to low only when the value of the 3-bit counter cnt_s is 4.

[0143] In addition, similarly to the flip-flop circuit 51, an inverted signal of the long burst detection signal det_lb is supplied to the reset terminal of the flip-flop circuit 53. Thus, the value of the D-Phase detection signal det_dp is reset to 1 in response to the long burst detection signal det_lb becoming high.

[0144] The flip-flop circuit 55 is a circuit that outputs the value supplied to the data terminal from the output terminal when the clock terminal is activated, similar to the flip-flop circuits 51 and 53. A 1-bit value is supplied to the data terminal of the flip-flop circuit 55 from the logic circuit 54, and the output value of the flip-flop circuit 55 is Fig.11 The digital data transmission period detection signal det_id shown is supplied to the logic circuit 56 .

[0145] The logic circuit 54 is a circuit that inverts the output value (0 or 1) of the flip-flop circuit 53 and supplies it to the data terminal of the flip-flop circuit 53 when the value of the 3-bit counter cnt_s is 0, and supplies 0 to the data terminal of the flip-flop circuit 53 when the 3-bit counter cnt_s is 4. In addition, similarly to the flip-flop circuits 51 and 53, the inverted signal of the wait detection signal det_wait is supplied to the clock terminal of the flip-flop circuit 55. Therefore, the value of the digital data transmission period detection signal det_id becomes 1 when the wait detection signal det_wait changes to low when the value of the 3-bit counter cnt_s is 0, and becomes 0 when the wait detection signal det_wait changes to low when the value of the 3-bit counter cnt_s is 4.

[0146] The logic circuit 56 is a circuit that generates the D-Phase enable signal EN_DP, the first side switch selection signal sel_sw0, the second side switch selection signal sw1, the first identification information selection signal sel_id0, and the second identification information selection signal sel_id1 based on the values ​​of the 3-bit counter cnt_s, the D-Phase detection signal det_dp, and the digital data transmission period detection signal det_id. Specifically, the logic circuit 56 is configured to make the inverted signal of the D-Phase detection signal det_dp become the D-Phase enable signal EN_DP when the digital data transmission period detection signal det_id is low, and to fix the D-Phase enable signal EN_DP to high when the digital data transmission period detection signal det_id is high, thereby generating the D-Phase enable signal EN_DP.

[0147] Here, the generation of the D-Phase enable signal EN_DP when the digital data transmission period detection signal det_id is low is similar to the generation of the D-Phase enable signal EN_DP except that the D-Phase detection signal det_dp is sandwiched. Figure 4 The operation of the switching circuit 43 shown is the same. Therefore, it can be said that the timing generating circuit 45 includes the switching circuit 43.

[0148] In addition, the logic circuit 56 performs the following processing: according to the change of the value of the 3-bit counter cnt_s to 1, the first side switch selection signal sel_sw0 is activated to be high within the specified time, according to the change of the value of the 3-bit counter cnt_s to 2, the second side switch selection signal sel_sw1 is activated to be high within the specified time, according to the change of the value of the 3-bit counter cnt_s to 3, the first identification information selection signal sel_id0 is activated to be high within the specified time, and according to the change of the value of the 3-bit counter cnt_s to 4, the second identification information selection signal sel_id1 is activated to be high within the specified time.

[0149] AND circuit 57a is a switch selection signal sel_sw0 and Fig.12 The AND circuit 57b is a circuit that outputs high when both switch information SW0 are high and outputs low in other cases. Fig.12 The AND circuit 57c is a circuit that outputs high when both the switch information SW1 are high and outputs low in other cases. Fig.12 The AND circuit 57d is a circuit that outputs high when both the identification information ID0 are high and outputs low otherwise. Fig.12The circuit shown is a circuit that outputs high when both identification information ID1 are high, and outputs low otherwise.

[0150] The OR circuit 58 is a circuit that outputs a low value when the outputs of the four AND circuits 57a to 57d are all low, and outputs a high value in other cases. The above-mentioned digital data transmission enable signal EN_ID becomes an inverted signal of the output of the OR circuit 58. Thus, the digital data transmission enable signal EN_ID becomes a low value when the bit value to be transmitted is "1", and becomes a high value when the bit value to be transmitted is "0", thereby realizing the control of the above-mentioned switch element 25 (disconnected when "1" is transmitted, and connected when "0" is transmitted).

[0151] Fig.16 and Fig.17 1 and 2 are flowcharts showing the processing performed by the sensor controller 31 of the present embodiment. Hereinafter, the operation of the sensor controller 31 of the present embodiment will be described in more detail with reference to these drawings.

[0152] First refer to Fig.16 , the sensor controller 31 first enters the action mode LB (step S30) and sends out a long burst signal (step S31). As a result, the order in which the electromagnetic induction pen 2 sends out the reference alternating magnetic field PSS and the modulated alternating magnetic field PSM is reset, and the alternating magnetic field PS sent out next by the electromagnetic induction pen 2 must become the reference alternating magnetic field PSS. Therefore, the sensor controller 31 then enters the action mode D-Phase (step S32), and performs the supply of the alternating current Tx to each loop coil LCy and the detection of the amplitude of the induced current Rx appearing in each loop coil LCx (step S33).

[0153] Next, the sensor controller 31 derives the position of the electromagnetic induction pen 2 based on the amplitude of the induced current Rx at each loop coil LCy detected in step S33, and outputs it to the host processor 32 (step S34). In addition, the sensor controller 31 derives the phase of the induced current Rx at the loop coil LCx with the largest amplitude detected in step S33, and stores it as a reference phase (step S35).

[0154] Next, the sensor controller 31 determines whether it is the reception timing of the digital data from the electromagnetic induction pen 2 (step S36). The determination result becomes positive just after the long burst signal is sent in step S31 (that is, after the operation mode D-Phase is executed only once after the long burst signal is sent), and becomes negative at other time points. The sensor controller 31 that obtains the positive determination result in step S36 performs the digital data reception process for receiving the digital data sent by the electromagnetic induction pen 2 (step S37).

[0155] Fig.18 It is shown in Fig.16 As shown in the figure, the sensor controller 31 first substitutes 1 into the variable i (step S50), and then selects one of the multiple loop coils LCy and the multiple loop coils LCx that is closest to the immediately previous step S34 (refer to Fig.16 ) in step S51.

[0156] Next, the sensor controller 31 enters the action mode Wait and waits for a predetermined time (step S52), and then enters the action mode ID (step S53), and performs the supply of the alternating current Tx to the loop coil LCy selected in step S51 and the detection of the induced current Rx appearing in the loop coil LCx selected in step S51 (step S54). Then, the sensor controller 31 demodulates the i-th bit value sent by the electromagnetic induction pen 2 based on the detection result of the induced current Rx (steps S55 to S57). Specifically, it is determined whether the induced current Rx is detected in step S44 (step S55), and "1" is obtained when it is determined to be detected (step S56), and "0" is obtained when it is determined not to be detected (step S57).

[0157] After that, the sensor controller 31 increases the variable i by 1 (step S58) and determines whether the variable i exceeds 4 (step S59). If the variable i does not exceed 4, the process returns to step S52 and repeats the process. If the variable i exceeds 4, the digital data receiving process ends. Through the above process, the sensor controller 31 receives the 4-bit digital data sent by the electromagnetic induction pen 2.

[0158] return Fig.16 The sensor controller 31 that has completed the digital data reception processing in step S37 or obtained a negative determination result in step S36 enters the action mode Wait and waits for a specified time (step S38), and then determines whether the specified time has passed since the last transmission of the long burst signal (step S39). As a result, if it is determined that the specified time has passed, it returns to step S30 and enters the action mode LB again. If it is determined that the specified time has not passed, the processing is transferred to Fig.17 Step S40.

[0159] Move to Fig.17 In step S40, the sensor controller 31 enters the operation mode C-SW. Fig.16Similarly to step S33, supply of the alternating current Tx to each loop coil LCy and detection of the amplitude of the induced current Rx appearing in each loop coil LCx are performed (step S41).

[0160] Next, the sensor controller 31 derives the position of the electromagnetic induction pen 2 based on the amplitude of the induced current Rx at each ring coil LCy detected in step S41, and outputs it to the host processor 32 (step S42). In addition, the sensor controller 31 derives the phase of the induced current Rx at the ring coil LCx with the largest amplitude detected in step S41 (step S43). Then, based on the derived phase and the reference phase stored in the most recent step S35, the pen pressure value P sent by the electromagnetic induction pen 2 is derived, and output to the host processor 32 (step S44). The specific method of deriving the pen pressure value P is as described in the first embodiment.

[0161] After that, the sensor controller 31 enters the action mode Wait and waits for a predetermined time (step S45), and then determines whether the predetermined time has passed since the last transmission of the long burst signal (step S46). As a result, if it is determined that the predetermined time has passed, the sensor controller 31 returns to step S30 and enters the action mode LB again, and if it is determined that the predetermined time has not passed, the sensor controller 31 returns to step S32 and enters the action mode D-Phase again.

[0162] As described above, according to the position detection system 1 of this embodiment, as in the first embodiment, by alternately sending out a reference alternating magnetic field and a modulated alternating magnetic field from the electromagnetic induction pen 2, it is possible to improve the detection accuracy of values ​​representing the user's behavior, such as the pen pressure value P, compared with the past, and to send digital data from the electromagnetic induction pen 2 to the position detection device 3.

[0163] In addition, according to the position detection system 1 of the present embodiment, the sensor controller 31 can reset the order in which the electromagnetic induction pen 2 sends out the reference alternating magnetic field PSS and the modulated alternating magnetic field PSM. Therefore, the sensor controller 31 does not need to perform the initial setting mode described in the first embodiment, and accordingly, the derivation of the pen pressure value P can be started in advance.

[0164] In addition, according to the position detection system 1 of the present embodiment, digital data (switch information SW0, SW1 and identification information ID0, ID1) and analog operation amount (pen pressure value P) are sent during the period when the sensor controller 31 does not send out the alternating magnetic field AM. Therefore, the position detection device 3 can be prevented from failing in detecting the analog operation amount sent by the electromagnetic induction pen 2 and receiving the digital data.

[0165] Next, the position detection system 1 of the third embodiment of the present invention is described. The position detection system 1 of this embodiment is different from the position detection system 1 of the second embodiment in that the electromagnetic induction pen 2 sends 1-bit digital data not by the presence or absence of the sending of the alternating magnetic field PS but by the type of the sent alternating magnetic field PS (reference alternating magnetic field PSS or modulated alternating magnetic field PSM). The other points are the same as the position detection system 1 of the second embodiment, so the following description will continue with a focus on the differences from the position detection system 1 of the second embodiment.

[0166] Fig.19 2 is a diagram showing the internal structure of the electromagnetic induction pen 2 in the position detection system 1 of this embodiment. Fig.12 As can be understood from the comparison, the electromagnetic induction pen 2 of the present embodiment is different from the electromagnetic induction pen 2 of the second embodiment in that the processing circuit 23 includes an AND circuit 47 and the first resonance circuit R1 does not include a switching element 25 .

[0167] The AND circuit 47 is a circuit that outputs a high signal when the D-Phase enable signal EN_DP and the digital data transmission enable signal EN_ID outputted from the timing generation circuit 45 are both high, and outputs a low signal otherwise. The output of the AND circuit 47 is supplied to the gate of the switching element 24. Fig.11 As shown in FIG. 1 , the D-Phase enable signal EN_DP when the electromagnetic induction pen 2 sends digital data is fixed to high. Fig.15 As understood, the digital data transmission enable signal EN_ID is fixed to high when digital data is not transmitted from the electromagnetic induction pen 2. Therefore, according to the AND circuit 47, when digital data is transmitted from the electromagnetic induction pen 2, the value of the digital data transmission enable signal EN_ID is supplied to the gate of the switching element 24, so that when the transmitted bit value is "1" (that is, when the digital data transmission enable signal EN_ID is low), the reference alternating magnetic field PSS is transmitted, and when the transmitted bit value is "0" (that is, when the digital data transmission enable signal EN_ID is high), the modulated alternating magnetic field PSM is transmitted. In addition, according to the AND circuit 47, when digital data is not transmitted from the electromagnetic induction pen 2, either the reference alternating magnetic field PSS or the modulated alternating magnetic field PSM is transmitted according to the D-Phase enable signal EN_DP.

[0168] Fig. 20 1 is a flowchart showing the digital data receiving process performed by the sensor controller 31 of this embodiment. Fig.18As can be understood from the comparison, the digital data receiving process performed by the sensor controller 31 of the present embodiment is different from the digital data receiving process performed by the sensor controller 31 of the second embodiment in that steps S60 to S62 are performed instead of steps S54 and S55. The following description will focus on the difference.

[0169] After the sensor controller 31 of this embodiment enters the operation mode ID in step S53, it supplies the alternating current Tx to the loop coil LCy selected in step S51 and derives the phase of the induced current Rx appearing in the loop coil LCx selected in step S51 (step S60). Then, the sensor controller 31 performs the phase derivation based on the derived phase and the phase of the induced current Rx in the most recent step S35 (see step S60). Fig.16 ) is used to demodulate the i-th bit value sent by the electromagnetic induction pen 2 (steps S61, S62, S56, and S57). Specifically, based on the derived phase and the stored reference phase, it is determined whether the received alternating magnetic field PS is the reference alternating magnetic field PSS or the modulated alternating magnetic field PSM (steps S61 and S62), and when it is determined to be the reference alternating magnetic field PSS, "1" is obtained (step S56), and when it is determined to be the modulated alternating magnetic field PSM, "0" is obtained (step S57). In this way, the sensor controller 31 can receive the bit value sent by the electromagnetic induction pen 2.

[0170] As described above, according to the position detection system 1 of this embodiment, the electromagnetic induction pen 2 can send digital data by switching between sending the reference alternating magnetic field PSS and sending the modulated alternating magnetic field PSM. Therefore, when sending digital data, the state of sending the alternating magnetic field PS from the electromagnetic induction pen 2 can be maintained.

[0171] Next, the position detection system 1 of the fourth embodiment of the present invention is described. The position detection system 1 of this embodiment is different from the position detection system 1 of the second embodiment in that the electromagnetic induction pen 2 is configured to continuously send digital data including switch information SW0, SW1 and identification information ID0, ID1 regardless of whether a long burst signal is received. The other points are the same as the position detection system 1 of the second embodiment, so the following description will continue with a focus on the differences from the position detection system 1 of the second embodiment.

[0172] Figure 21~Figure 23 This is a diagram for explaining the operation of the sensor controller 31 and the processing circuit 23 according to the present embodiment. Fig. 22 Show Fig.21 The follow-up, Fig.23 Show Fig. 22As shown in these figures, the sensor controller 31 of the present embodiment is configured to, after entering action mode LB and the subsequent action mode D-Phase, sequentially enter action mode Wait, action mode ID, action mode Wait, action mode C-SW, action mode Wait, action mode ID, action mode Wait, action mode D-Phase, and repeat the same actions until entering action mode LB next time (for example, until a specified time has passed since the last long burst signal was sent). Figure 21~Figure 23 An example is shown in which the earliest action mode LB passes through action modes D-Phase and C-SW 6 times each and then enters action mode LB again. However, this is just an example used to show the action when entering the next action mode LB. The actual sensor controller 31 only needs to enter action mode LB at a lower frequency.

[0173] The internal structure of the processing circuit 23 is Fig.12 The internal structure shown is the same. However, there are some differences in the structure and operation of the timing generation circuit 45 from the second embodiment. Specifically, the timing generation circuit 45 of this embodiment is first configured to have a 4-bit counter cnt_s instead of a 3-bit counter cnt_s. The timing generation circuit 45 is configured to reset the value of the 4-bit counter cnt_s to 0 when the long burst detection signal det_lb becomes high, and then increment the value of the 4-bit counter cnt_s by 1 at the timing when the wait detection signal det_wait becomes low for the odd number of times from the timing when the long burst detection signal det_lb becomes high. This increment continues until the value of the 4-bit counter cnt_s becomes 9. After becoming 9, the value of the 4-bit counter cnt_s is temporarily restored to 1, and the same increment is continued again.

[0174] In addition, the timing generation circuit 45 of the present embodiment is configured to change the value of the D-Phase detection signal det_dp to low according to the long burst detection signal det_lb becoming high, and then switch the value of the D-Phase detection signal det_dp between high and low at the timing when the waiting detection signal det_wait becomes low for the 4n+2nd and 4n+3rd times (n is an integer greater than 0) from the timing when the long burst detection signal det_lb becomes high. With respect to the D-Phase enable signal EN_DP generated according to the D-Phase detection signal det_dp, the timing generation circuit 45 of the present embodiment is configured to always make the inverted signal of the D-Phase detection signal det_dp the D-Phase enable signal EN_DP. Thus, the alternating magnetic field sent by the electromagnetic induction pen 2 becomes the modulated alternating magnetic field PSM when the sensor controller 31 enters the operation mode C-SW, and becomes the reference alternating magnetic field PSS when the sensor controller 31 enters the operation mode D-Phase or the operation mode ID.

[0175] The digital data sent by the electromagnetic induction pen 2 of this embodiment includes the start data STA of each 1 bit and the stop data STP0~STP3 of 4 bits in addition to the above-mentioned switch information SW0, SW1, identification information ID0, ID1. The timing generation circuit 45 controls the digital data transmission enable signal EN_ID in such a way that the total 9-bit value is sent 1 bit at a time corresponding to the value of the 4-bit counter cnt_s. Specifically, it is configured to control the digital data transmission enable signal EN_ID based on the start data STA, switch information SW0, SW1, identification information ID0, ID1, and stop data STP0~STP3 in sequence according to the value of the 4-bit counter cnt_s changing to 1~9. As a result, after sending the long burst signal, the sensor controller 31 receives the start data STA, switch information SW0, SW1, identification information ID0, ID1, and stop data STP0~STP3 in sequence every time it enters the action mode ID. In this case, the start data STA and the stop data STP0~STP3 are used to determine the start and end of the data received by the sensor controller 31.

[0176] Fig.24 and Fig.25 Flowcharts showing the processing performed by the sensor controller 31 of this embodiment. Fig.16 and Fig.18 The obtained graph is Fig.16 and Fig.18 The same parts are marked with Fig.16 and Fig.18 The same reference numerals are used herein. Fig.24 and Fig.25 The operation of the sensor controller 31 according to the present embodiment will be described in more detail.

[0177] First refer to Fig.24 , the sensor controller 31 and Fig.16 After the processing of steps S30 to S35 is performed in the same manner as in the example, a digital data receiving process for receiving the digital data transmitted by the electromagnetic induction pen 2 is performed (step S70).

[0178] Fig.25 Shown in Fig.24 As shown in the figure, the sensor controller 31 of this embodiment and the Fig.18 After the processing of steps S51 to S57 is performed in the same manner as in the example, the bit value obtained in step S56 or step S57 is stored (step S71). Then, it is determined whether the first bit of the latest 9 bits is equal to the start data STA, and the last 4 bits are equal to the stop data STP0 to STP3 (steps S72, S73).

[0179] If it is determined to be equal in step S73, the sensor controller 31 obtains the switch information SW0, SW1 and the identification information ID0, ID1 based on the 2nd to 5th bits of the latest 9 bits (step S74), and ends the digital data reception process. If it is not determined to be equal in step S73, the sensor controller 31 does not execute step S74 and ends the digital data reception process.

[0180] return Fig.24 After completing the digital data reception process of step S70, the sensor controller 31 and Fig.16 and Fig.17 In the example of , the processing after step S38 is performed in the same manner. Thus, it is possible to alternately enter the operation mode D-Phase and the operation mode C-SW with the operation mode ID sandwiched therebetween, and to enter the operation mode LB again when a predetermined time has passed since the last transmission of the long burst signal.

[0181] According to the position detection system 1 of the present embodiment, the effect of significantly reducing the frequency of sending long burst signals can be obtained compared with the position detection system 1 of the second embodiment. That is, in the position detection system 1 of the present embodiment, the electromagnetic induction pen 2 repeatedly sends 9-bit information including switch information SW0, SW1 and identification information ID0, ID1 regardless of whether the long burst signal is received or not, so the sensor controller 31 can continuously receive switch information SW0, SW1 and identification information ID0, ID1 from the electromagnetic induction pen 2 even if the trigger of the long burst signal is not generated. Therefore, the sensor controller 31 of the present embodiment does not need to send a long burst signal in order to make the electromagnetic induction pen 2 send the switch information SW0, SW1 and identification information ID0, ID1, so the frequency of sending long burst signals can be significantly reduced. In one example, the sensor controller 31 only sends a long burst signal for the purpose of initializing the transmission order of the reference alternating magnetic field PSS and the modulated alternating magnetic field PSM when the electromagnetic induction pen 2 is newly detected.

[0182] Next, the position detection system 1 of the fifth embodiment of the present invention is described. The position detection system 1 of this embodiment is different from the position detection system 1 of the second embodiment in that the electromagnetic induction pen 2 is configured to simultaneously send multi-bit digital data by frequency shift keying. The other points are the same as the position detection system 1 of the second embodiment, so the following description will continue with a focus on the differences from the position detection system 1 of the second embodiment.

[0183] Fig.26 2 is a diagram showing the structure of the electromagnetic induction pen 2 of this embodiment. Fig.10 As can be understood from the comparison, the electromagnetic induction pen 2 of the present embodiment is different from the electromagnetic induction pen 2 of the second embodiment in that the switching element 25 is replaced with capacitors C1 to C4 and switching elements 65 to 68 .

[0184] Capacitors C1~C4 are connected in parallel with capacitor C, respectively. In addition, switch elements 65~68 are connected in series with capacitors C1~C4, respectively. The electromagnetic induction pen 2 of this embodiment is configured so that, when a reference alternating magnetic field PSS is sent out, switch element 24 is turned off and switch elements 65~68 are turned on. Thus, in this embodiment, the frequency of the reference alternating magnetic field PSS (reference frequency) becomes a value determined by the combined capacitance of capacitors C and C1~C4 (frequency f0 described later). In addition, when a modulated alternating magnetic field PSM is sent out, the electromagnetic induction pen 2 is configured so that all switch elements 24, 65~68 are turned on. Thus, in this embodiment, the frequency of the modulated alternating magnetic field PSM becomes a value determined by the combined capacitance of capacitors C, C SW , the value determined by the combined capacitance of C1 to C4 (the frequency f SW ).

[0185] On the other hand, when transmitting digital data, the electromagnetic induction pen 2 of this embodiment is configured to turn off the switch element 24 and control the on and off of the switch elements 65 to 68 according to the transmitted value. As a result, the frequency of the alternating magnetic field sent from the electromagnetic induction pen 2 becomes a value determined by the combined capacitance of the capacitor C and the capacitor connected to the capacitor C among the capacitors C1 to C4 (frequency f0 to f4 described later). 15 ) The electromagnetic induction pen 2 of this embodiment is configured to transmit 4-bit digital data by utilizing the frequency property of such an alternating magnetic field.

[0186] Fig. 27 (a) shows the value sent by the electromagnetic induction pen 2 (including the pen pressure value P as the analog operation amount) and the on-off state of the switch elements 24, 65 to 68, the capacitors C, C SW The combined capacitance C of the capacitors in C1 to C4 incorporated in the resonant circuit C , and the resonant frequency f of the resonant circuit R In this diagram and the following description, capacitors C and C SW The capacitances of C1~C4 are represented as C, C SW , C1~C4, and the inductance of coil L is represented as L.

[0187] like Fig. 27 As shown in (a), the synthetic capacitance C when the electromagnetic induction pen 2 sends the pen pressure value P C The value becomes C+C SW +C1+C4+C3+C4. Variable capacitance capacitor C SW Capacitance C SW As described above, it is an analog quantity that changes continuously. Therefore, in this case, the frequency f of the alternating magnetic field sent from the electromagnetic induction pen 2 is SW Becomes according to the capacitance C SW Therefore, it can be said that the transmission of the writing pressure value P by the electromagnetic induction pen 2 is based on analog modulation (more specifically, frequency modulation).

[0188] On the other hand, when the electromagnetic induction pen 2 transmits 4-bit digital data, the synthetic capacitance C C The value of C varies discontinuously from C to C+C1+C4+C3+C4 in 16 steps. C The value of the alternating magnetic field sent from the electromagnetic induction pen 2 is f0~f 15 Therefore, it can be said that the transmission of digital data by the electromagnetic induction pen 2 is based on digital modulation (more specifically, frequency shift keying).

[0189] Here, the resonant frequency f of the resonant circuit R The specific value is expressed as f using the mathematical formula R =(2π(L×C C ) -1 ). Therefore, the resultant capacitance C C The larger the value of is, the higher the resonant frequency f R The smaller the value of .

[0190] Fig. 27 (b) shows the resonant frequency f corresponding to each transmission value on a straight line. R As shown in the figure, the resonance frequency f when the electromagnetic induction pen 2 transmits the writing pressure value P R The value of frequency f SW At the ratio frequency f0~f 15 This is because the synthetic capacitance C in this case C The value of C+C SW +C1+C4+C3+C4 regardless of the capacitance C SW Whatever the value of Fig. 27 The composite capacitance C shown in (a) C The largest value among multiple values ​​of .

[0191] On the other hand, the resonance frequency f when the electromagnetic induction pen 2 transmits digital data is R The value becomes the reference frequency f0 and the frequencies f1~f 15 Any one of them. At frequencies f0~f 15 The reason why the reference frequency f0 is the smallest is that the synthetic capacitance C corresponding to the sent value 0000 C The value of C+C1+C4+C3+C4 is greater than the synthetic capacitance C corresponding to the other sent values ​​0001~1111 C It should be noted that the synthetic capacitance C corresponding to the transmitted value 0001~1111 C The magnitude relationship of the values ​​of C1 to C4 varies depending on the specific values ​​of the capacitors C1 to C4. However, if the capacitance ratio is set to C1:C2:C3:C4 = 8:4:2:1, the larger the transmission value, the greater the synthetic capacitance C. C The smaller the relationship.

[0192] As described above, according to the position detection system 1 of the present embodiment, by making the resonance frequency f R Digital modulation is performed by increasing the resonant frequency f0 to a value smaller than the reference frequency f0. RThe analog modulation is performed by continuously changing, so the frequency change from the reference frequency f0 can be suppressed compared to the case where both digital modulation and analog modulation are performed on the same positive and negative sides from the reference frequency f0. Therefore, according to the position detection system 1 of this embodiment, the range of the discrete Fourier transform (or fast Fourier transform) of the induced current Rx performed by the sensor controller 31 can be narrowed.

[0193] As mentioned above, although the preferred embodiment of the present invention has been described, the present invention is not limited to such embodiment at all, and the present invention can be implemented in various forms within the scope not departing from the gist of the present invention.

[0194] For example, the method for transmitting digital data in the fifth embodiment can also be applied to the transmission of digital data by the electromagnetic induction pen 2 in the second embodiment or the fourth embodiment. That is, the electromagnetic induction pen 2 in the second embodiment or the fourth embodiment can also transmit 4 bits of digital data simultaneously by frequency shift keying realized by the on-off control of the switch elements 65 to 68, instead of transmitting 1 bit of digital data by amplitude shift keying realized by the on-off control of the switch element 25. By doing so, more digital data can be transmitted, or digital data of a specified number of bits can be transmitted in a shorter time, or both can be achieved.

[0195] Description of Reference Numerals

[0196] 1 Position detection system

[0197] 2 Electromagnetic induction pen

[0198] 3 Position detection device

[0199] 20 Core

[0200] 21. Pressure sensor

[0201] 22a, 22b side switches

[0202] 23 Processing circuit

[0203] 24, 25 Switching elements

[0204] 30 Switch

[0205] 31 Sensor Controller

[0206] 32 Host processor

[0207] 40 Power circuit

[0208] 41 Detection circuit

[0209] 41a Half-wave voltage doubler rectifier circuit

[0210] 41b, 41d voltage divider circuit

[0211] 41c Smoothing circuit

[0212] 41e Operational Amplifier

[0213] 41f, 42a, 44a Resistor element

[0214] 41g, 41i Inverting Buffer Circuit

[0215] 41h RC low pass filter

[0216] 42 Waiting detection circuit

[0217] 42b, 44b Schottky barrier diode

[0218] 42c, 44c capacitors

[0219] 42d, 44d Schmitt trigger circuit

[0220] 43 Switching Circuit

[0221] 43a, 51, 53, 55 trigger circuits

[0222] 44 Long burst detection circuit

[0223] 45 Timing Generation Circuit

[0224] 46a~46d, 65~68 switch elements

[0225] 47, 57a~57d and circuit

[0226] 50 Adder

[0227] 52, 54, 56 Logic circuits

[0228] 58 or circuit

[0229] AM Alternating Magnetic Field

[0230] C, C1~C4 capacitors

[0231] C SW Variable Capacitors

[0232] L Coil

[0233] LC, LCy, LCx Toroidal Coils

[0234] PS Alternating Magnetic Field

[0235] PSM modulated alternating magnetic field

[0236] PSS reference alternating magnetic field

[0237] R1 First resonant circuit

[0238] R2 Second resonant circuit.

Claims

1. An electromagnetic induction pen, comprising: A first resonant circuit is configured to include an inductor element and a capacitor element; as well as a variable element connected to the first resonant circuit, The variation element is an element that varies the resonance frequency of the second resonance circuit including the variation element and the first resonance circuit in association with the behavior of the user. The electromagnetic induction pen further includes a switching circuit that switches between sending out a reference alternating magnetic field using the first resonant circuit and sending out a modulated alternating magnetic field using the second resonant circuit.

2. The electromagnetic induction pen according to claim 1, wherein: There is a sending-off period in which neither the reference alternating magnetic field nor the modulated alternating magnetic field is sent out between the sending-off of the reference alternating magnetic field and the sending-off of the modulated alternating magnetic field.

3. The electromagnetic induction pen according to claim 1, wherein: The switching circuit is configured to switch between sending out the reference alternating magnetic field and sending out the modulated alternating magnetic field in response to a lapse of a predetermined time or longer from when the alternating magnetic field is no longer received from the position detection device.

4. The electromagnetic induction pen according to claim 1, wherein: The switching circuit repeatedly sends out the reference alternating magnetic field and the modulated alternating magnetic field in a predetermined manner after a predetermined timing detected in the electromagnetic induction pen.

5. The electromagnetic induction pen according to claim 4, wherein: The prescribed timing is given by the alternating magnetic field from the position detection device.

6. The electromagnetic induction pen according to claim 5, wherein: The electromagnetic induction pen resets the sending order of the reference alternating magnetic field and the modulated alternating magnetic field according to the alternating magnetic field being continuously received from the position detection device within a predetermined time.

7. An integrated circuit for a position detection device, The integrated circuit receives an alternating magnetic field from an electromagnetic induction pen, wherein the electromagnetic induction pen comprises: A first resonant circuit is configured to include an inductor element and a capacitor element; and a variation element connected to the first resonant circuit, the variation element being an element that changes the resonant frequency of a second resonant circuit including the variation element and the first resonant circuit in association with a user's behavior, the alternating magnetic field being a reference alternating magnetic field generated using the first resonant circuit or a modulated alternating magnetic field generated using the second resonant circuit, The integrated circuit determines whether the received alternating magnetic field is the reference alternating magnetic field or the modulated alternating magnetic field. The integrated circuit outputs a digital value corresponding to an analog quantity represented by the modulated alternating magnetic field based on a reception result of the alternating magnetic field determined to be the reference alternating magnetic field.

8. The integrated circuit according to claim 7, wherein: The integrated circuit receives the alternating magnetic field twice before the determination. The integrated circuit performs the determination based on the phase, frequency or amplitude of each of the two received alternating magnetic fields.

9. The integrated circuit according to claim 7, wherein: The integrated circuit determines that the received alternating magnetic field is the reference alternating magnetic field when the phase, frequency or amplitude of the received alternating magnetic field satisfies a predetermined condition.

10. The integrated circuit according to claim 7, wherein: The electromagnetic induction pen is configured to repeatedly send out the reference alternating magnetic field and the modulated alternating magnetic field in a predetermined order. After determining that the received alternating magnetic field is the reference alternating magnetic field, the integrated circuit receives the reference alternating magnetic field and the modulated alternating magnetic field in the prescribed order.

11. A position detection device, The position detection device receives a reference alternating magnetic field and a modulated alternating magnetic field respectively from an electromagnetic induction pen, and the electromagnetic induction pen comprises: A first resonant circuit is configured to include an inductor element and a capacitor element; and a variation element connected to the first resonant circuit, the variation element being an element that changes the resonant frequency of a second resonant circuit including the variation element and the first resonant circuit in association with a user's behavior, the reference alternating magnetic field being generated using the first resonant circuit, and the modulated alternating magnetic field being generated using the second resonant circuit, The position detection device obtains a first output based on the reference alternating magnetic field, The position detection device obtains a second output based on the modulated alternating magnetic field, The position detection device obtains a third output by adding or subtracting a predetermined offset amount from a difference between the first output and the second output. The position detection device converts the third output into a digital value using a predetermined conversion rule.

12. The position detection device according to claim 11, wherein: The predetermined offset amount is determined based on a difference between the first output and the second output in a state where the behavior is not performed.

13. The position detection device according to claim 11, wherein: The predetermined conversion rule is a rule that, when the third output is smaller than a value indicating that the behavior is not performed, causes the digital value to be a value indicating that the behavior is not performed.

14. The position detection device according to claim 11, wherein: The predetermined conversion rule is configured such that the larger the amount of the behavior, the larger the amount of change in the digital value relative to the change in the amount of the behavior.

15. An electromagnetic induction pen, comprising: A first resonant circuit is configured to include an inductor element and a capacitor element; as well as a variable element connected to the first resonant circuit, The variation element is an element that varies the resonance frequency of the second resonance circuit including the variation element and the first resonance circuit in association with the behavior of the user. The electromagnetic induction pen further includes a processing circuit that switches between sending out a reference alternating magnetic field using the first resonant circuit and sending out a modulated alternating magnetic field using the second resonant circuit based on a bit value sent to a position detection device.

16. A position detection device, The position detection device receives an alternating magnetic field from an electromagnetic induction pen, and the electromagnetic induction pen comprises: A first resonant circuit is configured to include an inductor element and a capacitor element; and a variation element connected to the first resonant circuit, the variation element being an element that changes the resonant frequency of a second resonant circuit including the variation element and the first resonant circuit in association with a user's behavior, the alternating magnetic field being a reference alternating magnetic field generated using the first resonant circuit or a modulated alternating magnetic field generated using the second resonant circuit, The position detection device determines whether the alternating magnetic field is the reference alternating magnetic field or the modulated alternating magnetic field. The position detection device obtains the bit value transmitted by the electromagnetic induction pen based on the result of the determination.

17. An electromagnetic induction pen, The electromagnetic induction pen performs a process of transmitting digital data by digital modulation and a process of transmitting an analog operation amount by analog modulation during a period in which the sensor controller does not send out an alternating magnetic field.

18. The electromagnetic induction pen according to claim 17, wherein: The transmission of the digital data and the transmission of the analog operation amount are executed while being switched in a predetermined sequence.

19. The electromagnetic induction pen according to claim 18, wherein: The prescribed sequence is the following sequence: after sending out a reference alternating magnetic field from a first resonant circuit having a reference frequency that does not vary according to the analog operation amount as a resonant frequency, the sending of the digital data based on the digital modulation is performed multiple times, and then, a modulated alternating magnetic field is sent out from a second resonant circuit having a frequency that varies according to the analog operation amount as a resonant frequency.

20. The electromagnetic induction pen according to claim 18, wherein: The prescribed sequence is a sequence in which a reference alternating magnetic field is sent out from a first resonant circuit having a reference frequency that does not vary according to the analog operation amount and a modulated alternating magnetic field is sent out from a second resonant circuit having a frequency that varies according to the analog operation amount as a resonant frequency, alternately, and the digital data is sent through the digital modulation between the sending out of the reference alternating magnetic field and the sending out of the modulated alternating magnetic field.

21. The electromagnetic induction pen according to claim 17, wherein: The digital modulation is amplitude shift keying, The analog modulation is frequency shift keying that expresses the analog operation amount using a change amount from a reference frequency that does not change in accordance with the analog operation amount.

22. The electromagnetic induction pen according to claim 17, wherein: The digital modulation is performed by increasing the resonance frequency of the resonance circuit from a reference frequency that does not change according to the analog operation amount, and the analog modulation is performed by continuously changing the resonance frequency of the resonance circuit within a range of values ​​smaller than the reference frequency.

23. The electromagnetic induction pen according to claim 22, wherein: The electromagnetic induction pen has: a variable capacitance capacitor whose capacitance varies according to the analog operation amount; and One or more capacitors are connected in parallel with the variable capacitance capacitor, The analog modulation is performed by connecting the variable capacitance capacitor and the one or more capacitors to the resonant circuit. The digital modulation is performed by disconnecting the variable capacitance capacitor from the resonance circuit and connecting one or more of the one or more capacitors to the resonance circuit according to a transmission value.

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