JP7130617B2 - Active pen and sensor integrated circuit - Google Patents

Description

The present invention relates to an active pen configured to transmit a downlink signal towards a position detection device and a sensor integrated circuit for receiving the downlink signal transmitted by the active pen.

In recent years, there has been a demand for simultaneous input by a plurality of active pens in position detection systems that support input by active pens, and several techniques for this purpose have been proposed. One of them allows multiple active pens to transmit downlink signals at the same time by transmitting downlink signals at different frequencies within the same time slot. Document 1 discloses an example thereof.

U.S. Patent Application Publication No. 2016/0246390

By the way, the inventors of the present application are considering using a frequency dividing circuit in order to realize downlink signals of different frequencies with the simplest possible configuration. For example, if an 8 MHz reference clock is used, 500 kHz can be generated by dividing the frequency by 1/16, 333.3 kHz by dividing by 1/24, and 250 kHz by dividing by 1/32. If a downlink signal is generated using a frequency, it becomes possible to create a carrier wave for the downlink signal with a simple configuration of a frequency dividing circuit.

However, as a result of a more detailed study, it was found that simply using the frequency dividing circuit would complicate the calculations on the side of the sensor integrated circuit that receives the downlink signal, and that it would not be used within one time slot. It was found that the difference in time between the active pens became large, causing a problem that the time could not be used effectively. A detailed description will be given below.

FIG. 14 is a diagram showing the structure of a downlink signal according to the background art of the present invention. It should be noted that the technique itself shown in the figure was conceived by the inventors of the present application, and was not publicly known at the time of filing of the present application. This figure shows an example in which a downlink signal is configured by a BPSK (Binary Phase-Shift Keying) modulated pulse signal. Therefore, in the example of FIG. 14, one symbol (a group of digital data sent by one modulation) consists of one bit. Further, FIG. 14 shows an example in which active pen 1 transmits a downlink signal at 500 kHz, active pen 2 transmits a downlink signal at 333.3 kHz, and active pen 3 transmits a downlink signal at 250 kHz. ing. Furthermore, FIG. 14 shows an example in which the time length of one time slot is 0.25 msec and the size of data transmitted within one time slot is 21 bits.

In order to avoid the occurrence of harmonic noise, the length of time used for transmitting one symbol (time length of window W shown; hereinafter referred to as "symbol time length") should be equal to an integer multiple of the period of the pulse signal. should be set to However, if the symbol time length is set in such a manner, the symbol time length will have different values for each frequency, as shown in FIG. In the example of FIG. 14, the symbol time length is 10 μsec when the frequency is 500 kHz, 9 μsec when the frequency is 333.3 kHz, and 8 μsec when the frequency is 250 kHz. As a result, the start position and end position of the window W are different for each frequency, and the calculation for phase acquisition becomes complicated on the side of the sensor integrated circuit that receives the downlink signal.

In addition, as shown in FIG. 14, there is also a problem that the difference in unused time between active pens within one time slot becomes large. For example, the difference in idle time between active pen 1, which uses a 500 kHz downlink signal, and active pen 3, which uses a 250 kHz downlink signal, is 82−40=42 μsec. This 42 μsec can be said to be a time that cannot be used effectively.

Therefore, one of the objects of the present invention is to generate a carrier wave for a downlink signal with a simple configuration of a frequency dividing circuit, while complicating the calculation for phase acquisition on the side of the sensor integrated circuit that receives the downlink signal. To provide an active pen and a sensor integrated circuit capable of avoiding the above and reducing the difference in unused time between active pens in one time slot.

An active pen according to the present invention is an active pen configured to transmit one or more symbol values in one time slot, dividing a reference clock by a division ratio based on each of a plurality of different frequencies. a frequency dividing unit configured to generate a plurality of carriers having different frequencies by dividing the first carrier generated by the frequency dividing unit with a value of a first symbol to be transmitted; a first downlink signal over a common symbol time length on the plurality of frequencies.

A sensor integrated circuit according to the present invention is connected to a group of sensor electrodes, and based on the electrical charge induced in the group of sensor electrodes, one or more active pens using different ones of a plurality of predetermined frequencies. A sensor integrated circuit that detects a plurality of downlink signals transmitted from, detects an indicated position based on the detected downlink signals, and demodulates values of symbols transmitted by the detected downlink signals, an AD converter that acquires a reception level value corresponding to the charge induced in one of the plurality of sensor electrodes constituting the sensor electrode group; Obtaining the downlink signal transmitted at the corresponding frequency by frequency-analyzing the string of the received level values at the corresponding frequency, and transmitting the obtained downlink signal for each symbol time length common to the plurality of frequencies a plurality of demodulators for obtaining values of the symbols transmitted by the obtained downlink signal by phase analysis.

According to the present invention, since the symbol time lengths of the downlink signals transmitted by the active pens are equal to each other, the downlink signal is received while the carrier for the downlink signal is generated by a simple configuration of the frequency dividing circuit. It is possible to avoid complication of calculation for phase acquisition on the sensor integrated circuit side. In addition, since the total time length of the downlink signal transmitted by each active pen is equal to each other, it is possible to reduce the difference in unused time between active pens within one time slot.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the whole structure of the position detection system 1 by the 1st Embodiment of this invention. It is a figure explaining the principle of OFDM. FIG. 10 is a diagram showing an example in which active pens 2a and 2c are positioned on the same sensor electrode 30X; FIG. 4 is a diagram showing a frequency spectrum of a signal detected by a sensor electrode 30X in the example of FIG. 3; 3 is a diagram showing functional blocks of a signal processing section 26 in the active pen 2a; FIG. It is a figure which shows the functional block of the signal processing part 26 in the active pen 2c. 4 is a diagram showing an example of a clock signal CLK generated by a reference clock generator 42 and a plurality of carriers generated by a frequency divider 43; FIG. FIG. 4 is a diagram showing windows W (signals for one symbol) of downlink signals DS transmitted at six types of frequencies f4, f5, f7, f8, f10, and f14. 3 is a diagram showing internal configurations of a sensor electrode group 30 and a sensor integrated circuit 31. FIG. FIG. 4 is a diagram showing a configuration for receiving a downlink signal DS, which is provided in a receiving section 54; It is a figure which shows the 1st modification of the active pen 2a. It is a figure which shows the 2nd modification of the active pen 2a. FIG. 4 is a diagram showing a configuration for receiving a downlink signal DS provided in a receiving section 54 when multiplication is performed by mixers 64a and 64b in the analog domain; FIG. 2 is a diagram showing the structure of a downlink signal according to the background art of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing the overall configuration of a position detection system 1 according to a first embodiment of the invention. As shown in the figure, the position detection system 1 includes a plurality of active pens 2a to 2c and a position detection device 3. FIG. In the following description, the active pens 2a to 2c may be collectively referred to as the active pen 2 when there is no particular need to distinguish between them.

Each of the active pens 2a to 2c is an electronic pen compatible with, for example, an active electrostatic system. Among them, the active pen 2c includes a core body 20, electrodes 21 and 22, a writing pressure detection section 23, a switch 24, a power supply 25, and a signal processing section 26, as shown in FIG. Also, the active pens 2a and 2b have the same configuration as the active pen 2c, except that the electrodes 22 are not provided. In the following, the configuration of the active pen 2 will be described by focusing on the active pen 2c.

Each of the electrodes 21 and 22 is a conductor provided near the core 20 and electrically connected to the signal processing section 26 by wiring. The electrode 22 is provided at a position farther from the tip (pen tip) of the core 20 than the electrode 21 and is typically used by the position detection device 3 to detect the tilt of the active pen 2 .

The pen pressure detection unit 23 is a functional unit that detects the force (pen pressure) applied to the tip (pen tip) of the core 20 . More specifically, the writing pressure detection section 23 is in contact with the rear end portion of the core body 20, and through this contact, when the user presses the tip of the active pen 2 against the touch surface, the core body 20 is detected. configured to detect forces applied to the In a specific example, the pen pressure detection unit 23 is configured by a variable capacitance module whose capacitance changes according to the force applied to the pen tip.

The switch 24 is a switch provided on the side surface of the active pen 2 and configured to be turned on and off by the user. The power supply 25 is for supplying operating power (DC voltage) to the signal processing section 26, and is composed of, for example, a cylindrical AAAA battery.

The signal processing section 26 is a processing section configured by a circuit group formed on a substrate (not shown), and is connected to the electrodes 21 and 22, the writing pressure detection section 23, and the switch 24, respectively. The signal processing unit 26 is configured to be able to transmit and receive signals to and from the position detection device 3 using the electrodes 21 and 22 among them. Hereinafter, the signal transmitted from the position detection device 3 to the active pen 2 among the signals thus transmitted and received is referred to as an uplink signal US, and the signal transmitted from the active pen 2 to the position detection device 3 is referred to as a downlink signal DS. .

The uplink signal US includes a command indicating the content of control over the active pen 2 . The downlink signal DS includes a burst signal, which is an unmodulated carrier wave signal, and a data signal, which is a carrier wave signal modulated with predetermined data. The signal processing unit 26 acquires data to be transmitted by the data signal according to the command included in the uplink signal US, and modulates the carrier wave signal with the acquired data to transmit the data signal. The data transmitted by the data signal includes the writing pressure detected by the writing pressure detection unit 23, information indicating the ON/OFF state of the switch 24, the pen ID written in advance in the signal processing unit 26, and the like.

Transmission and reception of the uplink signal US and the downlink signal DS are performed in units of frames. This frame is, for example, a display period for one screen of the display included in the position detection device 3, as will be described later. In a typical example, an uplink signal US is transmitted at the beginning of a frame, followed by a downlink signal DS. In this case, the uplink signal US serves to inform the active pen 2 of the start timing of the frame. The transmission time of the downlink signal DS within a frame is divided into a plurality of time slots, and within each time slot, a plurality of active pens 2 simultaneously transmit a predetermined number of symbols of the downlink signal DS.

In this embodiment, the frequency of the carrier of the downlink signal DS is set to , a plurality of mutually orthogonal frequencies are used. The concept of a plurality of orthogonal frequencies conforms to Orthogonal Frequency Division Multiplexing (OFDM) generally used in wireless communication fields such as wireless LAN and 3GPP (Third Generation Partnership Project). In addition, in this embodiment, by setting the symbol time length to the same value regardless of the frequency, it is possible to avoid complication of calculation for phase acquisition on the side of the sensor integrated circuit 31 that receives the downlink signal DS. To reduce the difference in unused time between active pens 2 within a time slot. These points will be explained in detail later.

The position detection device 3 is a device that has a touch surface and is configured to detect the position of each active pen 2 within the touch surface. Typically, the position detection device 3 is a computer such as a tablet terminal, and the display surface of the display serves as a touch surface. However, the position detection device 3 may be a digitizer that does not have a display surface. Below, description is continued assuming that the position detection device 3 is a tablet terminal.

The position detection device 3 includes a sensor electrode group 30 arranged directly below the touch surface, a sensor integrated circuit 31, and a host processor 32 that controls the functions of each part of the position detection device 3 including these. be.

The sensor electrode group 30 constitutes a mutual capacitance type touch sensor, and has a configuration in which a plurality of sensor electrodes 30X and a plurality of sensor electrodes 30Y are arranged in a matrix. The plurality of sensor electrodes 30X each extend in the illustrated Y direction and are configured by a plurality of linear conductors arranged at equal intervals in the X direction orthogonal to the Y direction. Further, the plurality of sensor electrodes 30Y are configured by a plurality of linear conductors extending in the X direction and arranged at regular intervals in the Y direction. FIG. 1 shows only a portion of each of the plurality of sensor electrodes 30X and 30Y. The plurality of sensor electrodes 30Y may also serve as a common electrode of the display, and the position detection device 3 in that case is called an "in-cell type" as will be described later.

The sensor integrated circuit 31 has a function of detecting the pointing position of each active pen 2 on the touch surface, receiving data transmitted by each active pen 2 using the downlink signal DS, and detecting the position of the finger on the touch surface. and a function to detect When the position detection device 3 is of the in-cell type, the sensor integrated circuit 31 also has a function of applying a common potential required for display operation to the plurality of sensor electrodes 30Y.

Details of the sensor integrated circuit 31 will be described later with reference to FIG. It has a function of transmitting a link signal US and receiving a downlink signal DS transmitted by each active pen 2 . When a burst signal in the downlink signal DS is received, the sensor integrated circuit 31 derives the indicated position of the active pen 2 based on the received level of the burst signal at each of the sensor electrodes 30X and 30Y, and supplies it to the host processor 32. do. Also, when the data signal in the downlink signal DS is received, the sensor integrated circuit 31 extracts the data transmitted by the active pen 2 by demodulating the data signal and supplies it to the host processor 32 .

The host processor 32 is a central processing unit that controls the position detection device 3 as a whole. On the host processor 32, various applications such as a drawing application and a communication application are operable. The drawing application generates and stores stroke data indicating respective trajectories on the touch surface based on a series of positions of the active pen 2 or finger sequentially supplied from the sensor integrated circuit 31, and renders the stored stroke data. play a role in When the drawing application receives the data transmitted by the active pen 2 from the sensor integrated circuit 31, the drawing application controls the line width, transparency, line color, etc. of the stroke data to be rendered according to the supplied data.

Here, OFDM mentioned above will be described. FIG. 2 is a diagram explaining the principle of OFDM. The figure shows frequency spectra of signals U1(f) to U7(f) transmitted and received by OFDM, with the horizontal axis representing the frequency f and the vertical axis representing the amplitude.

Signals U1(f) to U7(f) are signal groups designed such that their center frequencies f ₁ to f ₇ are orthogonal to each other, and satisfy the following equation (1). where T is the symbol time length, and δ _ij is a delta function that is 1 when i=j and 0 when i≠j.

By designing the signals U1(f) to U7(f) in this way, as shown in FIG. 2, the signal power density of the other signals becomes 0 at the center frequency of each signal. , are received in a superimposed manner, they can be received by distinguishing them. Specifically, the following equations (2) and (3) are calculated for the received signal f(t), and bit determination is performed based on the results for each frequency, whereby the signal Signals U1(f) to U7(f) can be discriminated and received.

Such OFDM is generally used in the wireless communication field as described above, and is usually used to multiplex and transmit a large amount of data from one transmitter. On the other hand, in the present embodiment, a different frequency is assigned to each active pen 2, and the downlink signal DS is transmitted using the assigned frequency. multi-pen transmission).

A more specific example will be described. FIG. 3 is a diagram showing an example in which the active pens 2a and 2c shown in FIG. 1 are positioned on the same sensor electrode 30X. In the figure, downward arrows indicate downlink signals DS, and upward arrows indicate uplink signals US. The figure also shows a glass plate 33 arranged on the sensor electrode group 30 . A touch surface of the position detection device 3 is configured by the surface of the glass plate 33 . In the example of FIG. 3, the downlink signal DS transmitted from the electrode 21 of the active pen 2a is the signal U2(f) shown in FIG. 2, and the downlink signal DS transmitted from the electrode 21 of the active pen 2c is shown in FIG. 2, and the downlink signal DS transmitted from the electrode 22 of the active pen 2c is the signal U7(f) shown in FIG.

FIG. 4 is a diagram showing the frequency spectrum of the signal detected by the sensor electrode 30X in the example of FIG. The signals U2(f), U6(f), and U7(f) are superimposed and detected by the sensor electrode 30X. Since the signal power density of (f) and U7(f) is 0, the sensor integrated circuit 31 observes the amplitude of the center frequency of the signal U2(f), thereby detecting the downlink signal DS transmitted by the active pen 2a. can be obtained. Similarly, since the signal power densities of the signals U2(f) and U7(f) are 0 at the center frequency of the signal U6(f), the sensor integrated circuit 31 observes the amplitude of the center frequency of the signal U6(f). By doing so, the downlink signal DS transmitted from the electrode 21 by the active pen 2c can be acquired. Further, since the signal power density of the signals U6(f) and U7(f) is 0 at the center frequency of the signal U7(f), the sensor integrated circuit 31 observes the amplitude of the center frequency of the signal U7(f). Thereby, the downlink signal DS transmitted from the electrode 22 by the active pen 2c can be obtained.

In the example of FIG. 4, the peaks of the signals U6(f) and U7(f) are smaller than the amplitude of the signal U2(f) because the active pen 2a is in the pen-down state ( This is because the active pen 2c is in a hover state (a state in which the pen tip is away from the touch surface), while the pen tip is in contact with the touch surface. The position detection device 3 must detect the position of not only the active pen 2 in the pen-down state with a large amplitude but also the active pen 2 in the hover state with a small amplitude. are orthogonal as shown in FIG. 4, the downlink signal DS of the active pen 2 with the larger amplitude (pen-down state) is the downlink signal DS of the active pen 2 with the smaller amplitude (hover state). It is possible to avoid affecting the DS reception level.

Hereinafter, the configuration of the active pen 2 for transmitting the downlink signal DS according to this embodiment will be described in detail, and then the configuration of the sensor integrated circuit 31 for receiving the downlink signal DS according to this embodiment will be described. I will explain in detail.

FIG. 5 is a diagram showing functional blocks of the signal processing section 26 in the active pen 2a. Although not shown, the signal processing section 26 in the active 2b also has similar functional blocks. As shown in the figure, the signal processing unit 26 in the active pen 2a includes a receiving unit 40, a control unit 41, a reference clock generating unit 42, a dividing unit 43, a modulating unit 44, and an amplifying unit 45. be done.

The receiving unit 40 is a detection circuit that detects the uplink signal US received by the electrode 21 , acquires the frame start timing based on the reception timing of the uplink signal US, and notifies the control unit 41 of it. Moreover, the command transmitted by the sensor integrated circuit 31 is obtained by demodulating the uplink signal US and supplied to the control unit 41 .

The control section 41 is a processor having a function of controlling each section in the active pen 2 and incorporates a memory (not shown). This memory stores the time length of the frame, the position of each time slot within the frame, one or more combinations of a plurality of time slots contained within the frame to be used for transmission of the downlink signal DS, Various information related to transmission and reception of the uplink signal US and the downlink signal DS are stored in advance, such as the number of bits to be transmitted in and the symbol time length of the downlink signal DS. Based on the uplink signal US received by the unit 40, the modulating unit 44 is caused to transmit the downlink signal DS.

Here, the symbol time length is the time corresponding to the unit time of demodulation processing in the position detection device 3 that detects the downlink signal DS. is set to a value common to the frequencies of By doing this, the symbol time length of the downlink signal DS transmitted from each active pen 2 becomes the same value regardless of the frequency of the downlink signal DS. It becomes possible to receive the downlink signal DS transmitted by each active pen 2 without performing any calculation. This point will be explained in more detail later.

The operation of the control section 41 will be specifically described. First, the control unit 41 acquires the position of each time slot within the frame based on the start timing of the frame notified from the receiving unit 40 . Further, based on the command (setting data) supplied from the receiving unit 40, the control unit 41 controls the frequency to be used for transmitting the downlink signal DS, the content of the data to be transmitted by the downlink signal DS, and the content of the data to be transmitted by the downlink signal DS. determines one or more time slots to be used for transmission of . Among them, the frequency is one of six types of frequencies f4, f5, f7, f8, f10, and f14, which will be described later, and the control unit 41 is configured to set the determined frequency to the frequency dividing unit 43. .

The data transmitted by the downlink signal DS includes the writing pressure detected by the writing pressure detection unit 23, switch information indicating the ON/OFF state of the switch 24, pen ID written in advance in a memory (not shown) in the control unit 41, and the like. is included. The control unit 41 acquires the writing pressure from the writing pressure detection unit 23 when the content of the determined data is the writing pressure, and acquires the switch information from the switch 24 when it is the switch information. In this case, the pen ID is obtained from the built-in memory. The control unit 41 generates a data signal constituting the downlink signal DS based on the various data acquired in this way, and further generates the downlink signal DS by adding a predetermined burst signal.

The control unit 41 that has generated the downlink signal DS determines the symbol sequence SS to be transmitted in each of the determined one or more time slots based on the content of the generated downlink signal DS. The part corresponding to the burst signal in the symbol string SS is determined so that the phase of the pulse signal repeats the same value. By doing so, the burst signal becomes a tone signal in which pulse signals having the same phase are repeatedly transmitted. The control unit 41 is configured to supply the determined symbol sequence SS in parallel to the modulation unit 44 at a timing corresponding to each time slot (timing based on the uplink signal US).

The reference clock generation unit 42 is a functional unit that generates a clock signal CLK (reference clock), which is a pulse signal with a predetermined frequency. Although this predetermined frequency is 8 MHz in FIG. 5 and each figure to be described later, it is a matter of course that other frequencies may be used. In the following description, it is assumed that the clock signal CLK is an 8 MHz pulse signal.

The frequency dividing unit 43 divides the clock signal CLK by frequency dividing ratios based on a plurality of mutually different frequencies (six types of frequencies f4, f5, f7, f8, f10, and f14, which will be described later). A frequency dividing circuit configured to generate a plurality of carrier waves having different frequencies. Specifically, it is configured to generate a carrier wave having a frequency (for example, frequency f8) set by the control unit 41 by frequency division. The carrier wave output from the frequency divider 43 may be a pulse signal as shown in FIG. 7, which will be described later.

The modulation unit 44 modulates the carrier (first carrier) generated by the frequency dividing unit 43 with the value of the symbol to be transmitted (first symbol value) supplied from the control unit 41, and obtains It is a transmitting circuit (transmitting section) that transmits the received signal (first downlink signal) over the symbol time length previously stored in the memory of the control section 41 .

Specifically, as shown in FIG. 5, the modulating section 44 includes a serial output section 44a and a mixer 44b. The serial output unit 44a is configured to serially supply the symbol string SS supplied in parallel from the control unit 41 symbol by symbol to the mixer 44b.

The mixer 44b is a circuit that controls the phase of the carrier wave generated by the frequency dividing section 43 according to the value of the symbol supplied from the serial output section 44a. The value is arranged to be multiplied by the carrier generated by the frequency divider 43 . Phase control by the mixer 44b is performed by BPSK. That is, the mixer 44b controls the phase of the carrier wave so that the phase becomes 0 when the value of the symbol supplied from the serial output section 44a is 0, and the phase of the symbol supplied from the serial output section 44a becomes 1. It is configured to control the phase of the carrier so that the phase becomes π when .

The mixer 44 b is configured to supply the signal for one symbol obtained as a result of phase control to the amplifier 45 over the symbol time length stored in advance in the memory of the controller 41 . The amplifier 45 amplifies the signal thus supplied from the mixer 44 b and supplies it to the electrode 21 . As a result, a downlink signal DS having a symbol time length common to a plurality of frequencies that can be used for transmission of the downlink signal DS is transmitted from the electrode 21 toward the sensor integrated circuit 31 .

FIG. 6 is a diagram showing functional blocks of the signal processing section 26 in the active pen 2c. The difference from the functional block of the active pen 2a shown in FIG. is. The following description focuses on the difference from the active pen 2a.

The control unit 41 of the active pen 2c is configured to determine two frequencies to be used for transmitting the downlink signal DS based on the command (setting data) supplied from the receiving unit 40. FIG. The control unit 41 sets each of the determined two frequencies to the frequency dividing unit 43 . The frequency divider 43 is configured to generate carrier waves by frequency division for each of the two frequencies (for example, frequencies f4 and f14) set by the controller 41 .

The control unit 41 also controls the symbols to be transmitted in each of one or more time slots from the electrode 21 (first electrode) based on the downlink signal DS generated based on the data acquired from the writing pressure detection unit 23 or the like. A sequence SS1 and a symbol sequence SS2 to be transmitted in each of one or more time slots from electrode 22 (second electrode) are determined. Then, they are configured to be supplied to the modulating section 44 in parallel at timings corresponding to the respective time slots.

The serial output unit 44a serially supplies the symbol string SS1 supplied in parallel from the control unit 41 to the mixer 44b one symbol at a time, and serially supplies the symbol string SS2 supplied in parallel from the control unit 41 to the mixer 44b. It is configured to feed, symbol by symbol, serially to the mixer 44c.

The mixer 44b shifts the phase of one of the two carriers (first carrier) generated by the frequency divider 43 according to the symbol value (first symbol value) sequentially supplied from the serial output unit 44a. Control. In addition, the mixer 44c converts the other (second carrier) of the two carriers generated by the frequency divider 43 based on the symbol value (second symbol value) sequentially supplied from the serial output unit 44a. Control the phase.

Each of the mixers 44 b and 44 c is configured to supply a signal for one symbol obtained as a result of phase control to the amplifying section 45 over a symbol time length stored in advance in the memory of the control section 41 . The amplifier 45 amplifies the signal supplied from the mixer 44 b and supplies it to the electrode 21 , and the amplifier 46 amplifies the signal supplied from the mixer 44 c and supplies it to the electrode 22 . As a result, downlink signals DS (first and second downlink signals) having a common symbol time length for a plurality of frequencies that can be used for transmission of the downlink signals DS are transmitted from each of the electrodes 21 and 22. will be

Six types of frequencies f4, f5, f7, f8, f10, and f14 that can be set in the frequency divider 43 will be described in detail below.

FIG. 7 is a diagram showing an example of the clock signal CLK generated by the reference clock generator 42 and multiple carriers generated by the frequency divider 43. As shown in FIG. The figure shows a waveform for one symbol time length (for example, 35 μsec). As shown in the figure, both the clock signal CLK and each carrier are composed of pulse signals.

The frequencies set in the frequency divider 43 are selected so that integral multiples of the period match the common symbol time length and are orthogonal to each other. The six frequencies f4, f5, f7, f8, f10, and f14 shown are examples of frequencies that can be selected in this way. Specifically, the frequency f4 is a frequency of approximately 114.2857143 kHz obtained by dividing the frequency of the clock signal CLK by 70, and 4 waves is exactly 35 μsec. The frequency f5 is a frequency of about 142.857143 kHz obtained by dividing the frequency of the clock signal CLK by 56, and 5 waves is exactly 35 μsec. The frequency f7 is a frequency of 200 kHz obtained by dividing the frequency of the clock signal CLK by 40, and 7 waves are exactly 35 μsec. The frequency f8 is a frequency of about 228.5714286 kHz obtained by dividing the frequency of the clock signal CLK by 35, and 8 waves is exactly 35 μsec. The frequency f10 is a frequency of about 285.7142857 kHz obtained by dividing the clock signal CLK by 28, and 10 waves is exactly 35 μsec. The frequency f14 is a frequency of 400 kHz obtained by dividing the frequency of the clock signal CLK by 20, and 14 waves is exactly 35 μsec.

FIG. 8 is a diagram showing windows W (signals for one symbol) of the downlink signal DS transmitted at each of six frequencies f4, f5, f7, f8, f10, and f14. According to this embodiment, since the symbol time length is constant regardless of the frequency of the downlink signal DS, the time length of the window W also has a constant value regardless of the frequency. As a result, in the sensor integrated circuit 31 that receives the downlink signal DS, there is no need to change the position of the window W depending on the frequency of the downlink signal DS. can be avoided. In addition, since the total time length of the downlink signal DS transmitted by each active pen 2 within one time slot is equal to each other, it is possible to reduce the difference in the unused time between the active pens 2 within one time slot. become.

As described above, according to the active pen 2 according to the present embodiment, the time length of the window W of the downlink signal DS transmitted by each active pen 2 is equal to the common symbol time length. With a simple configuration, it is possible to generate a carrier wave for the downlink signal DS and avoid complication of calculation for phase acquisition on the side of the sensor integrated circuit 31 that receives the downlink signal DS. In addition, since the total length of time of the downlink signal DS transmitted by each active pen 2 is equal to each other, it is possible to reduce the difference in unused time between active pens 2 within one time slot.

Next, the configuration of the sensor integrated circuit 31 for receiving the downlink signal DS according to this embodiment will be described in detail.

FIG. 9 is a diagram showing the internal configuration of the sensor electrode group 30 and the sensor integrated circuit 31. As shown in FIG. As described above, the sensor electrode group 30 is composed of a plurality of sensor electrodes 30X and 30Y. If the touch surface is constituted by the display surface of the display, one of the sensor electrodes 30X, 30Y can also be used as a common electrode within the display. A type of position detection device 3 that uses one of the sensor electrodes 30X and 30Y as a common electrode within the display is called, for example, an "in-cell type." On the other hand, the type of position detection device 3 in which the sensor electrodes 30X and 30Y and the common electrode in the display are provided separately is called, for example, an "out-cell type" or an "on-cell type." In the following description, it is assumed that the position detection device 3 is of the in-cell type, but the present invention is similarly applicable to an out-cell or on-cell position detection device.

When the display executes pixel driving processing, it is necessary to maintain the potential of the common electrode at a predetermined common potential Vcom. Therefore, in the in-cell position detection device 3, the sensor integrated circuit 31 cannot communicate with the active pen 2 and detect the finger while the display is performing pixel driving processing. Therefore, the host processor 32 causes the sensor integrated circuit 31 to communicate with the active pen 2 and detect the finger by using the horizontal blanking interval and the vertical blanking interval in which pixel drive processing is not performed. Specifically, the display period for one screen is regarded as one frame, and the horizontal blanking interval and vertical blanking interval included therein are regarded as time slots. The sensor integrated circuit 31 is controlled to perform the detection of .

The sensor integrated circuit 31 includes an MCU 50, a logic section 51, transmission sections 52 and 53, a reception section 54, and a selection section 55, as shown in FIG.

The MCU 50 and the logic unit 51 are control units that control transmission/reception operations of the sensor integrated circuit 31 by controlling the transmission units 52 and 53 , the reception unit 54 and the selection unit 55 . Specifically, the MCU 50 is a microprocessor that has ROM and RAM inside and operates by executing programs stored therein. The MCU 50 also has a function of outputting a common potential Vcom and a command COM. Command COM corresponds to the command included in the uplink signal US described above. On the other hand, the logic unit 51 is configured to output control signals ctrl_t, ctrl_r, sTR, selX, and selY under the control of the MCU 50 .

The commands COM output by the MCU 50 include the allocation of one or more time slots and frequencies for each electrode included in each active pen 2 being detected, and the data signals that the active pens 2 transmit in the downlink signal DS. It contains information (setting data) indicating the content of the data to be set. The MCU 50 is configured to determine one or more time slots and frequencies to be assigned to each active pen 2 based on the number of active pens 2 being detected, etc., and place them in the command COM.

The transmitter 52 is a circuit that generates a finger detection signal FDS used to detect a finger under control of the MCU 50 . The finger detection signal FDS is, for example, a signal made up of K pulse trains each containing K pulses (“1” or “−1” data). However, K is the number of sensor electrodes 30Y. Also, the contents of the K pulse trains (that is, combinations of K pulses) are all different.

The transmission unit 53 is a circuit that generates an uplink signal US based on the command COM supplied from the MCU 50 and the control signal ctrl_t from the logic unit 51 . Specifically, a predetermined preamble is added to the beginning of the command COM supplied from the MCU 50, and the resulting symbol sequence is spread by a predetermined spreading code (for example, an 11-chip long spreading code having autocorrelation characteristics). and further modulating, for example by cyclic shift, to generate the uplink signal US.

The selection unit 55 includes a switch 56 and conductor selection circuits 57x and 57y.

The switch 56 is a switch element configured such that the common terminal is connected to one of the T1 terminal, T2 terminal, D terminal, and R terminal. Of these terminals, the T2 terminal is actually a set of terminals corresponding to the number of the sensor electrodes 30Y. The common terminal of the switch 56 is connected to the conductor selection circuit 57y, the T1 terminal is connected to the output terminal of the transmission section 53, the T2 terminal is connected to the output terminal of the transmission section 52, and the D terminal is the MCU 50 that outputs the common potential Vcom. , and the R terminal is connected to the input terminal of the receiving section 54 .

The conductor selection circuit 57x is a switch element for selectively connecting the multiple sensor electrodes 30X to the common terminal of the switch 56. FIG. The conductor selection circuit 57x is also configured to be able to connect some or all of the plurality of sensor electrodes 30X to the common terminal of the switch 56 at the same time.

The conductor selection circuit 57y is a switching element for selectively connecting the plurality of sensor electrodes 30Y to the input end of the receiving section 54. FIG. The conductor selection circuit 57y is also configured to be able to connect some or all of the plurality of sensor electrodes 30Y to the input terminal of the receiving section 54 at the same time. Further, when the T2 terminal and the common terminal are connected in the switch 56, the conductor selection circuit 57y connects the plurality of terminals constituting the T2 terminal and the plurality of sensor electrodes 30Y one-to-one.

The selector 55 is supplied with four control signals sTR, selX, and selY from the logic unit 51 . Specifically, the control signal sTR is supplied to the switch 56, the control signal selX to the conductor selection circuit 57x, and the control signal selY to the conductor selection circuit 57y. The logic unit 51 controls the selection unit 55 using these control signals sTR, selX, and selY to transmit the uplink signal US or the finger detection signal FDS, apply the common potential Vcom, and apply the downlink signal DS or and reception of the finger detection signal FDS.

When transmitting the uplink signal US, the logic unit 51 controls the selection unit 55 so that all the sensor electrodes 30Y are connected to the input terminal of the transmission unit 53 at the same time.

Regarding the reception of the downlink signal DS, the logic unit 51 receives the downlink signal DS for detecting the undetected active pen 2 (global scan) and the downlink signal from the detected active pen 2 Different control is performed when receiving DS (sector scan). Specifically, first, the logic unit 51 for global scanning controls the selection unit 55 so that all the sensor electrodes 30X and 30Y are sequentially connected to the input terminals of the reception unit 54 . Next, the logic section 51 for sector scanning is configured such that, when receiving a burst signal, several sensor electrodes 30X and 30Y positioned near the pointing position of the active pen 2 are sequentially applied to the receiving section 54. The selector 55 is controlled so as to be connected to the input terminal. Subsequently, when receiving the data signal, the selector 55 is controlled so that the sensor electrode 30X or the sensor electrode 30Y closest to the pointing position of the active pen 2 is connected to the input end of the receiver 54 .

The logic unit 51 when transmitting/receiving the finger detection signal FDS changes the selection unit 55 so that the plurality of terminals constituting the T2 terminal of the switch 56 and the plurality of sensor electrodes 30X are connected one-to-one. Control. While maintaining this state, the selector 55 is controlled such that the plurality of sensor electrodes 30X are sequentially selected one by one and the selected sensor electrodes 30X are connected to the receiver .

When applying the common potential Vcom, the logic section 51 controls the selection section 55 so that all the sensor electrodes 30Y are connected to the D terminal of the switch 56 at the same time. As a result, the potential of each sensor electrode 30Y becomes equal to the common potential Vcom.

The receiving unit 54 is a circuit that receives the finger detection signal FDS transmitted by the transmitting unit 52 and the downlink signal DS transmitted by the active pen 2 based on the control signal ctrl_r of the logic unit 51 . At the timing of receiving the finger detection signal FDS, the receiving unit 54 acquires K current values for each sensor electrode 30X, and for each of the K pulse trains described above, K pulses forming the pulse train. , and the obtained K current values, thereby calculating the detection level for each intersection of each sensor electrode 30X and each sensor electrode 30Y. Based on the result, a touched area (touch area) within the touch surface is determined and output to the host processor 32 via the MCU 50 .

On the other hand, at the timing of receiving the downlink signal DS, the receiving unit 54 selects a plurality of predetermined frequencies (for example, the six types of frequencies f4 and f5 described above) based on the charges induced in the sensor electrode group 30. , f7, f8, f10, f14) are used to distinguish and detect a plurality of downlink signals DS transmitted from one or more active pens 2 using different ones of the detected plurality of downlink signals DS. It is configured to detect the indicated position based on each and to demodulate the value of the symbol transmitted by each of the plurality of detected downlink signals DS.

FIG. 10 is a diagram showing a configuration for receiving the downlink signal DS provided in the receiving section 54. As shown in FIG. As shown in the figure, the receiving unit 54 includes a buffer 60, a bandpass filter 61, an AD conversion unit 62, a replication unit 63, a demodulation unit 64, a position detection unit 65, and a data acquisition unit 66. . Among these, the demodulator 64, the position detector 65, and the data acquirer 66 are provided for each of a plurality of frequencies used for transmission of the downlink signal DS.

An input terminal of the buffer 60 is connected to one of the plurality of sensor electrodes 30X and 30Y (connected to the receiver 54 by the selector 55) forming the sensor electrode group 30 via the selector 55. FIG. The buffer 60 serves to amplify the current induced in the sensor electrode connected to the input terminal and supply it to the bandpass filter 61 .

The bandpass filter 61 is a filter circuit that removes low frequency noise and harmonic noise from the current supplied from the buffer 60 . The low-frequency noise removed by the bandpass filter 61 includes, for example, low-frequency noise from the power supply that may exist around the position detection device 3 .

The AD converter 62 is a circuit that samples and quantizes the output current of the bandpass filter 61 to acquire a reception level value corresponding to the charge induced in the corresponding sensor electrode. The sampling frequency of the AD converter 62 is set to a frequency sufficiently higher than the frequency of the pulse signal forming the downlink signal DS (for example, the frequency of the clock signal CLK shown in FIG. 7). The AD converter 62 is configured to supply the acquired reception level value to the sequential duplicator 63 .

The duplication unit 63 is a circuit that duplicates the sequence of reception level values supplied from the AD conversion unit 62 and supplies it to each of the plurality of demodulation units 64 in parallel.

Each of the plurality of demodulators 64 acquires the downlink signal DS transmitted at the corresponding frequency by frequency-analyzing the string of reception level values supplied from the duplicator 63 at the corresponding frequency, and acquires the acquired downlink It is a functional unit that acquires the value of the symbol transmitted by the acquired downlink signal DS by phase-analyzing the signal DS for each symbol time length (symbol time length common to a plurality of frequencies) described above. 2, it comprises mixers 64a and 64b and a phase/absolute value acquiring section 64c.

The mixers 64a and 64b are circuits for multiplying the sequence of reception level values supplied from the duplicator 63 by the carrier wave of the corresponding frequency. A mixer 64a is supplied with a carrier wave reproduced from a string of reception level values by a reproduction circuit (not shown). Further, a carrier wave obtained by shifting the phase of this carrier wave by π/2 is supplied to the mixer 64a. The reason why the two mixers 64a and 64b are used is that by checking the phase change of the downlink signal DS rather than the phase itself, even if the phase rotates during transmission/reception of the downlink signal DS, the This is to enable reception of the downlink signal DS. Such a demodulation method is generally called DBPSK (Differential Binary Phase-Shift Keying).

The phase/absolute value acquisition unit 64c acquires the downlink signal DS transmitted at the corresponding frequency based on the output signals of the mixers 64a and 64b. Then, by phase-analyzing the obtained downlink signal DS for each symbol time length (symbol time length common to a plurality of frequencies), the value of the symbol transmitted by the obtained downlink signal DS is obtained. Configured. Thus, the fact that the phase/absolute value acquisition unit 64c can perform phase analysis with a common symbol time length (that is, the symbol time length does not have to be changed for each frequency) is one of the effects of the present invention. . The phase/absolute value acquiring unit 64c also performs absolute value analysis for acquiring the level value of the acquired downlink signal DS.

The position detection unit 65 detects a plurality of sensor electrodes 30X and 30Y (in the case of global scanning, all sensor electrodes 30X and 30Y; in the case of sector scanning, several electrodes positioned near the pointing position of the active pen 2). sensor electrodes 30X and 30Y), based on the level values obtained by the corresponding phase/absolute value obtaining unit 64c, to detect the pointing position of the active pen 2. FIG. The pointing position thus detected is the pointing position of the active pen 2 that has transmitted the downlink signal DS at the corresponding frequency. The position detection unit 65 outputs the detected pointing position to the host processor 32 shown in FIG. 9 via the MCU 50 .

The data acquisition unit 66 is a functional unit that acquires data transmitted by the active pen 2 based on the symbol value acquired by the corresponding phase/absolute value acquisition unit 64c. The data detected in this manner is the data transmitted by the active pen 2 that transmitted the downlink signal DS at the corresponding frequency. The data acquisition unit 66 outputs the acquired data to the host processor 32 shown in FIG. 9 via the MCU 50 .

As described above, according to the sensor integrated circuit 31 according to the present embodiment, by receiving the downlink signal DS according to the present embodiment from each active pen 2, the indicated position of each active pen 2 and each active The data transmitted by the pen 2 can be obtained.

Although preferred embodiments of the present invention have been described above, the present invention is by no means limited to such embodiments, and the present invention can be implemented in various forms without departing from the gist thereof. is of course.

For example, in the present embodiment, the modulation unit 44 is configured to transmit each symbol over the symbol time length previously stored in the memory of the control unit 41 of the active pen 2. may be stored in advance in association with each frequency, and the modulating unit 44 may transmit a signal corresponding to the number of waves corresponding to the frequency of the downlink signal DS. Even in this way, it is possible to make the time length of the window W of the downlink signal DS transmitted by each active pen 2 equal to the common symbol time length.

Further, the “symbol time length common to a plurality of frequencies” in the present embodiment includes the case where the symbol time length differs for each frequency as long as the reception by the sensor integrated circuit 31 is not hindered. In other words, the receiving operation of the sensor integrated circuit 31 is designed in consideration of a certain degree of error in order to absorb the path difference of each downlink signal DS. Even if the symbol time length corresponding to each frequency differs within this error range, the sensor integrated circuit 31 can absorb the difference. The symbol time length may be different for each frequency.

In addition, in the present embodiment, an example of using six types of frequencies f4, f5, f7, f8, f10, and f14 whose integral multiples of the period completely match the symbol time length has been described. As long as there is no problem with reception by the integrated circuit 31, a frequency whose integral multiple of the period does not completely match the symbol time length may be used. More specifically, provided that the error is 3% or less, more preferably 1% or less, the integral multiple of the period and the symbol time length may not match. Within this error range, even if, for example, 21 symbols are transmitted, the accumulation of errors can be suppressed, and noise given to downlink signals DS of other frequencies can be suppressed. Further, by using a differential scheme such as DBPSK or QBPSK as the modulation scheme, it is possible to suppress the influence on the accuracy of demodulation of the downlink signal DS to be demodulated.

Further, the active pen 2 on the transmitting side repeatedly transmits the same data with the same modulation method several times (for example, two or three times). , 35 usec) (for example, 70 usec, 105 usec) may be used as the demodulation unit. By doing so, the signal-to-noise ratio (S/N ratio) on the receiving side can be improved, and as a result, the bit error rate of bit decoding can be reduced.

Further, in the present embodiment, an example in which the downlink signal DS is configured by a pulse signal has been described. A wave filter may be further provided to transmit the downlink signal DS output from the sinusoidal filter. This makes it possible to reduce harmonic noise.

Also, in this embodiment, an example of BPSK modulating the carrier wave to generate a downlink signal has been described, but other modulation schemes such as QPSK (Quadrature Phase-Shift Keying) and 16QAM (16 Quadrature Amplitude Modulation) are used. Of course, you may use it.

FIG. 11 is a diagram showing a first modification of the active pen 2a according to this embodiment. The active pen 2a according to this modified example differs from the active pen 2a shown in FIG. 5 in that the phase control of the carrier wave generated by the frequency divider 43 is performed by QPSK instead of BPSK. The following description focuses on the differences.

The active pen 2 a according to this modified example is configured to have a phase shifter 47 . The phase shifter 47 has a function of shifting the phase of the carrier generated by the frequency divider 43 by π/2. The modulation section 44 according to this modification is supplied with two of the carrier wave output from the frequency dividing section 43 and the carrier wave output from the phase shift section 47 . Although the phase shifting section 47 is provided separately from the frequency dividing section 43 in this modification, the frequency dividing section 43 may be provided with a phase shifting function.

The modulation section 44 is configured to have a mixer 44c in addition to the mixer 44b. In this modification, one symbol is composed of two bits, and the serial output section 44a is configured to supply one bit of these to the mixer 44b and the other one bit to the mixer 44c.

The mixer 44b controls the phase of the carrier wave output from the frequency dividing section 43 according to the bit values sequentially supplied from the serial output section 44a. The mixer 44c controls the phase of the carrier wave output from the phase shifter 47 according to the bit values sequentially supplied from the serial output section 44a. As a result, the mixer 44b outputs a pulse signal corresponding to cos(2πft) or -cos(2πft) according to the value of the corresponding bit, and the mixer 44c outputs sin( θ) or −sin (2πft). However, f is the frequency of the carrier wave and t is the time.

The active pen 2a according to this modification further includes an adder 48. FIG. The adder 48 is a functional unit that adds the signal output from the mixer 44b and the signal output from the mixer 44c. The signal generated by the adder 48 is either cos (2πft+π/4), cos (2πft+3π/4), cos (2πft+5π/4), or cos (2πft+7π/4) depending on the value of the corresponding symbol. corresponding pulse signal.

The adding unit 48 is configured to supply the generated signal to the amplifying unit 45 over the symbol time length pre-stored in the memory of the control unit 41 for each symbol. The amplifier 45 amplifies the signal thus supplied from the mixer 44 b and supplies it to the electrode 21 . As a result, also in this modification, a downlink signal DS having a common symbol time length is transmitted for a plurality of frequencies that can be used for transmission of the downlink signal DS.

Also, in the present embodiment, an example of sequentially transmitting the burst signal and the data signal that make up the downlink signal DS has been described, but using the principle of the present embodiment, it is also possible to transmit these simultaneously become. This point will be described below with a specific example.

FIG. 12 is a diagram showing a second modification of the active pen 2a according to this embodiment. The active pen 2a according to this modification differs from the active pen 2a shown in FIG. 5 in that the burst signal and the data signal are simultaneously transmitted at different frequencies. The following description focuses on the differences.

The control unit 41 of the active pen 2a according to this modification is configured to determine two frequencies to be used for transmitting the downlink signal DS based on the command supplied from the receiving unit 40. FIG. The control unit 41 sets each of the determined two frequencies to the frequency dividing unit 43 . The frequency divider 43 is configured to generate a carrier wave by dividing each of the two frequencies (for example, frequencies f4 and f14) set by the controller 41 .

The modulation section 44 is configured to have a mixer 44c in addition to the mixer 44b. The serial output unit 44a separates the symbol string SS supplied from the control unit 41 into a symbol string forming a burst signal and a symbol string forming a data signal, and sends the former to the mixer 44b and the latter to the mixer 44c. Feed serially, symbol by symbol. The operation of each of the mixers 44b and 44c that have received the symbol strings in this way is the same as that of the active pen 2c described with reference to FIG. However, in this modified example, the output signals of the mixers 44b and 44c are commonly supplied to the adder 48. FIG.

The adder 48 adds the signal output from the mixer 44b and the signal output from the mixer 44c in the same manner as the adder 48 shown in FIG. A signal obtained by this processing is amplified by the amplifier 45 and supplied to the electrode 21 . As a result, although the burst signal and the data signal are superimposed and transmitted in this modification, they are transmitted in an orthogonal frequency division multiplexed state, so the sensor integrated circuit 31 separates them. can do.

Further, in the present embodiment, as shown in FIG. 10, the bandpass filter 61 and the AD conversion unit 62 are provided in the preceding stage of the replication unit 63, and multiplication is performed by the mixers 64a and 64b in the digital domain. Multiplication by mixers 64a and 64b may be performed in the analog domain.

FIG. 13 is a diagram showing a configuration for receiving the downlink signal DS provided in the receiving section 54 when multiplication is performed by the mixers 64a and 64b in the analog domain. As shown in the figure, in this case, the input ends of the mixers 64a and 64b are directly connected in common to the output end of the bandpass filter 61, and the AD signal is connected between the mixers 64a and 64b and the phase/absolute value acquisition unit 64c. A conversion unit 64d is provided. The function of the AD converter 64d is the same as that of the AD converter 62 shown in FIG. This allows multiplication by the mixers 64a and 64b in the analog domain.

2, 2a to 2c active pen 3 position detection device 20 core 21, 22 electrode 23 writing pressure detection unit 24 switch 25 power supply 26 signal processing unit 30 sensor electrode group 30X, 30Y sensor electrode 31 sensor integrated circuit 32 host processor 33 glass plate 40 reception unit 41 control unit 42 reference clock generation unit 43 frequency division unit 44 modulation unit 44a serial output units 44b, 44c mixers 45, 46, 60 amplification unit 47 phase shift unit 48 addition unit 51 logic units 52, 53 transmission unit 54 reception Section 55 Selection Section 56 Switches 57x, 57y Conductor Selection Circuit 60 Buffer 61 Bandpass Filters 62, 64d AD Conversion Section 63 Duplication Section 64 Demodulation Sections 64a, 64b Mixer 64c Phase/Absolute Value Acquisition Section 65 Position Detection Section 66 Data Acquisition Section CLK Clock signal COM Commands ctrl_t, ctrl_r, sTR, selX, selY Control signal DS Downlink signals f4, f5, f7, f8, f10, f14 Frequency FDS Finger detection signal selX Control signals SS, SS1, SS2 Symbol string US Uplink signal Vcom common potential W window

Claims (13)

an active pen,
a signal generator;
By dividing the frequency of the signal generated by the signal generator, the first frequency selected from among a plurality of mutually orthogonal frequencies whose integral multiples of each cycle match the common symbol time length. a divider circuit for generating a first carrier;
transmitting circuitry for transmitting a first downlink signal by modulating the first carrier with a value of a first symbol to be transmitted over the common symbol duration;
Active pen including. wherein the first carrier is a pulse signal and the common symbol time length is an integer multiple of the period of the pulse signal;
An active pen according to claim 1. The common symbol time length is a time corresponding to a unit time of demodulation processing in a position detection device that detects the first downlink signal,
An active pen according to claim 1. further comprising first and second electrodes;
the frequency dividing circuit further generates a carrier wave of a second frequency different from the first frequency selected from the plurality of frequencies by dividing the signal generated by the signal generating unit;
the transmitting circuit further transmits a second downlink signal by modulating the second carrier with a second symbol value over the common symbol duration;
the transmission circuitry is configured to transmit the first downlink signal from the first electrode while transmitting the second downlink signal from the second electrode;
An active pen according to claim 1. the frequency dividing circuit further generates a carrier wave of a second frequency different from the first frequency selected from the plurality of frequencies by dividing the signal generated by the signal generating unit;
the transmitting circuit is configured to transmit the second carrier unmodulated and simultaneously with the first downlink signal over the common symbol duration;
An active pen according to claim 1. further comprising a detection circuit for detecting an uplink signal transmitted by the position detection device;
The transmission circuit is configured to transmit the first downlink signal at timing relative to the uplink signal detected by the detection circuit.
An active pen according to claim 1. further comprising a detection circuit for detecting an uplink signal transmitted by the position detection device;
wherein the first frequency is selected from among the plurality of frequencies based on configuration data included in the uplink signal;
An active pen according to claim 1. the transmission circuitry includes a sine wave filter that sinusoidalizes the first downlink signal, and is configured to transmit the first downlink signal output from the sine wave filter;
An active pen according to claim 1. the value of the first symbol is a value representing multiple bits;
An active pen according to claim 1. Among a plurality of predetermined frequencies which are connected to the sensor electrode group and which are orthogonal to each other and whose integral multiples of each period match a common symbol time length, based on the charge induced in the sensor electrode group Detect a plurality of downlink signals transmitted from one or more active pens using a different one of, detect the pointing position based on the detected downlink signal, and transmit by the detected downlink signal A sensor integrated circuit for demodulating symbol values, comprising:
an AD conversion unit that acquires a reception level value corresponding to the charge induced in one of the plurality of sensor electrodes constituting the sensor electrode group;
each corresponding to a different one of the plurality of frequencies, and obtaining and obtaining the downlink signal transmitted at the corresponding frequency by frequency-analyzing the string of received level values at the corresponding frequency; a plurality of demodulation units that acquire the values of the symbols transmitted by the acquired downlink signals by phase-analyzing the downlink signals for each of the common symbol time lengths;
A sensor integrated circuit comprising: Each of the plurality of demodulators further performs an absolute value analysis to acquire a level value of the acquired downlink signal,
The sensor integrated circuit comprises:
a position detection unit that detects an indicated position of the active pen based on the level value obtained for each of the plurality of sensor electrodes that constitute the sensor electrode group;
further comprising
11. The sensor integrated circuit of claim 10. The plurality of downlink signals includes two downlink signals transmitted from each of two different electrodes of one of the active pens.
11. The sensor integrated circuit of claim 10. the plurality of downlink signals includes two downlink signals transmitted from electrodes of each of two of the active pens;
11. The sensor integrated circuit of claim 10.

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