Palm rejection method and sensor controller

Abstract

To exclude a contact position of a palm from an instruction position of an active pen, which will not rely on a result of detection by a process different from detection of the active pen, such as touch detection.SOLUTION: A method of palm rejection is executed by a sensor controller that is connected to a plurality of sensor electrodes and that detects a downlink signal transmitted from an active pen. The downlink signal includes a predetermined waveform portion shared in advance between the sensor controller and the active pen, and the predetermined waveform portion is a portion obtained by modulating a preamble shared in advance between the sensor controller and the active pen. The method includes: a determination step of determining whether or not a phase of the predetermined waveform portion included in the detected downlink signal is inverted; and an output step of outputting a position of the active pen derived on the basis of a distribution of levels of the downlink signal in the plurality of sensor electrodes when it is determined that the phase is not inverted.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] This invention relates to a palm rejection method and a sensor controller. [Background technology]

[0002] A position detector is known that enables pen input using an active pen. An active pen is an electronic pen configured to transmit a downlink signal from a pen tip electrode located at the pen tip. The position detector is configured to attempt to detect the downlink signal at each of several sensor electrodes placed within the touch surface and to detect the indicated position of the active pen based on the results.

[0003] Incidentally, the downlink signal is transmitted through the casing of the active pen to the user's body holding the active pen. As a result, the downlink signal is transmitted not only from the pen tip electrodes but also from the user's palm. Therefore, if the user rests their hand on the touch surface, the downlink signal transmitted from the palm will also be detected by the sensor electrodes. The position detected based on this result cannot be said to accurately reflect the active pen's intended position, so it needs to be excluded from the active pen's intended position. In the following, excluding the palm contact position from the active pen's intended position will be referred to as "palm rejection".

[0004] Patent Document 1 discloses an example of a technology for realizing palm rejection. In this technology, the detection result of a finger touch is combined with the reception result of a downlink signal to determine whether the detected position of the downlink signal is a palm contact point or an active pen indication point. Based on this result, the palm contact point is excluded from the active pen indication points. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2018 / 225204 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the palm rejection described in Patent Document 1 requires the result of touch detection. Therefore, it cannot be performed in a mode that disables touch detection and only detects the active pen (pen-only mode).

[0007] Furthermore, in order to correctly determine the palm contact position in the palm rejection described in Patent Document 1, the area detected by palm contact in touch detection must be large enough to be distinguishable from the area detected by normal finger contact. Therefore, if the palm touch is light and only detected in an area indistinguishable from normal finger contact, correct determination cannot be made.

[0008] Therefore, one of the objectives of the present invention is to provide a palm rejection method and sensor controller that can exclude the palm contact position from the active pen's indicated position, without depending on the results of detection by a process different from the active pen's detection, such as touch detection. [Means for solving the problem]

[0009] The palm rejection method according to the present invention is a palm rejection method performed by a sensor controller connected to a plurality of sensor electrodes and detecting a downlink signal transmitted from an active pen, the method comprising: a determination step of determining whether the phase of the detected downlink signal matches a phase previously shared between the sensor controller and the active pen; and, if determined to match by the determination step, an output step of outputting the position of the active pen derived based on the distribution of levels of the downlink signal at the plurality of sensor electrodes.

[0010] The sensor controller according to the present invention is a sensor controller connected to a plurality of sensor electrodes and detecting a downlink signal having a predetermined frequency or waveform transmitted from an active pen, and determines whether the phase of the detected downlink signal matches a phase pre-shared between the sensor controller and the active pen. When it is determined that they match, the sensor controller outputs the position of the active pen derived based on the distribution of levels in the plurality of sensor electrodes of the downlink signal.

Advantages of the Invention

[0011] Assuming that the human body is not sufficiently grounded, the downlink signal detected via the human body becomes a signal with an inverted phase compared to the downlink signal detected via the pen tip electrode. According to the present invention, since the phase of the downlink signal is determined, the position derived based on the downlink signal detected via the human body can be specified. Therefore, it is possible to exclude the palm contact position from the indicated position of the active pen without depending on the result of detection by a process different from the detection of the active pen such as touch detection.

Brief Description of the Drawings

[0012] [Figure 1] It is a diagram showing the configuration of the electronic device 1 according to an embodiment of the present invention. [Figure 2] It is a diagram showing details of the sensor electrode group兼display 4. [Figure 3] It is a diagram showing the format of the downlink signal DS transmitted by the active pen PE. [Figure 4] It is a diagram for explaining the modulation process of the data signal. [Figure 5] It is a diagram showing the equivalent circuits of the active pen PE, the palm PA, and the sensor electrode group兼display 4. [Figure 6](a) is a figure showing the time evolution of the potential VT of the pen tip electrode 21 and the potential VB of the palm PA, simulated using the equivalent circuit of Figure 5, and (b) is a figure showing the time evolution of the potential V4y-1 of the linear conductor 4y-1 and the potential V4y-2 of the linear conductor 4y-2, simulated using the equivalent circuit of Figure 5. [Figure 7] (a) is a figure showing the time evolution of the potential VT of the pen tip electrode 21 and the potential VB of the palm PA, simulated using the equivalent circuit of Figure 5, and (b) is a figure showing the time evolution of the potential V4y-1 of the linear conductor 4y-1 and the potential V4y-2 of the linear conductor 4y-2, simulated using the equivalent circuit of Figure 5. [Figure 8] This figure shows the configuration of the sensor controller 2 according to an embodiment of the present invention. [Figure 9] This is a flowchart showing the pen detection process performed by the sensor controller 2. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0014] Figure 1 shows the configuration of the electronic device 1 according to this embodiment. The electronic device 1 is a device that supports pen input and finger touch input, such as a tablet computer, and as shown in Figure 1, it is composed of a sensor controller 2, a host processor 3, and a sensor electrode group / display 4.

[0015] Figure 1 also shows an active pen PE that performs pen input to the electronic device 1. The active pen PE is a stylus compatible with the active electrostatic method and is configured to communicate bidirectionally with the sensor controller 2, or to transmit signals unidirectionally to the sensor controller 2. Hereinafter, the signal transmitted from the sensor controller 2 to the active pen PE will be referred to as the uplink signal US, and the signal transmitted from the active pen PE to the sensor controller 2 will be referred to as the downlink signal DS. The user performs pen input by operating the active pen PE on the panel surface 1a (touch surface) provided on the electronic device 1, and finger touch input by tracing the panel surface 1a with their finger.

[0016] The host processor 3 is a processor that controls the entire electronic device 1, and the operation of each part within the electronic device 1, as described later, is performed under the control of the host processor 3. The sensor controller 2 is an integrated circuit that uses the sensor electrode group and the sensor electrode group in the display 4 (described later) to derive the position of an indicator object such as the active pen PE or the user's finger on the panel surface 1a, and to receive data transmitted by the active pen PE. The sensor controller 2 is configured to sequentially output the derived position and the data received from the active pen PE to the host processor 3. Based on the position and data thus input, the host processor 3 generates digital ink and performs drawing.

[0017] The sensor electrode group and display 4 is a device that integrates a sensor electrode group for realizing pen input and finger touch input with an electrode group that constitutes a display. Specific forms of the sensor electrode group and display 4 include an in-cell type, where some or all of the electrode group constituting the display is also used as part or all of the sensor electrode group, and an on-cell type, where the electrode group constituting the display and the sensor electrode group are electrically isolated. However, in this embodiment, the sensor electrode group and display 4 will be described as an in-cell type. However, the present invention is also applicable when the sensor electrode group and display 4 is an on-cell type, or when the sensor electrode group and the display are separate devices. Various displays such as liquid crystal displays or organic EL displays can be used as the display constituting the sensor electrode group and display 4, but in this embodiment, the description will be described as a TFT (Thin Film Transistor) type liquid crystal display.

[0018] Figure 2 shows the details of the sensor electrode group and display 4. As shown in the figure, the sensor electrode group and display 4 consists of a plurality of island-shaped conductors 4m arranged in a matrix in the xy plane, starting from the side closest to the panel surface 1a, a plurality of linear conductors 4y extending in the x direction and juxtaposed in the y direction, and a plurality of linear conductors 4x extending in the y direction and juxtaposed in the x direction. In addition to these, the actual sensor electrode group and display 4 also includes various other components such as a liquid crystal layer, but these are omitted from Figure 2.

[0019] Multiple island-shaped conductors 4m, multiple linear conductors 4y, and multiple linear conductors 4x are each switchably connected to either the host processor 3 or the sensor controller 2. This switching is performed by the host processor 3 in a time-division multiplexing manner. The sensor electrode group / display 4 is used as a display when each conductor is connected to the host processor 3, and as a sensor electrode group when it is connected to the sensor controller 2.

[0020] When the sensor electrode group / display 4 is used as a display, the host processor 3 supplies a common potential Vcom to each of the multiple island-shaped conductors 4m, uses the multiple linear conductors 4x as gate lines to control the on / off state of pixel transistors (not shown), and uses the multiple linear conductors 4y as data / source lines to supply data to the pixels.

[0021] On the other hand, when the sensor electrode group / display 4 is used as a sensor electrode group, the sensor controller 2 uses each of the multiple island-shaped conductors 4m as a sensor electrode to detect finger touch using a self-capacitive method, and uses each of the multiple linear conductors 4x, 4y as a sensor electrode to detect the active pen PE using an active electrostatic method.

[0022] Figure 2 also shows the internal configuration of the Active Pen PE. As shown in the figure, the Active Pen PE consists of a core body 20, a pen tip electrode 21, a pressure sensor 22, a switch 23, a control circuit 24, and a battery 25.

[0023] The core body 20 is a component that makes up the pen tip of the Active Pen PE. The rear end of the core body 20 is connected to the pressure sensor 22. The pen tip electrode 21 is an electrode provided near the tip of the core body 20 and is electrically connected to the control circuit 24. The pressure sensor 22 is a sensor that detects the pressure applied to the tip of the core body 20. The switch 23 is a switch element provided on the surface of the housing of the Active Pen PE and is configured to be turned on and off by the user.

[0024] The control circuit 24 is a circuit that operates using power supplied from the battery 25 and performs various processes. The processes performed by the control circuit 24 include controlling various parts of the active pen PE, as well as transmitting a downlink signal DS by controlling the potential of the pen tip electrode 21, and receiving an uplink signal US by detecting and demodulating fluctuations in the potential of the pen tip electrode 21.

[0025] Figure 3 shows the format of the downlink signal DS transmitted by the control circuit 24. Figure 3(a) shows the downlink signal DS transmitted by the control circuit 24 when the sensor controller 2 and the active pen PE are communicating bidirectionally, and the control circuit 24 has not yet detected the sensor controller 2. In this case, the downlink signal DS consists of a burst signal, which is an unmodulated carrier signal of a predetermined frequency.

[0026] Figure 3(b) shows the downlink signal DS transmitted by the control circuit 24 according to the received uplink signal US when the sensor controller 2 and the active pen PE communicate bidirectionally. The same downlink signal DS is also used when the active pen PE transmits a signal in one direction to the sensor controller 2. This downlink signal DS consists of a burst signal, which is an unmodulated carrier signal of a predetermined frequency, and a data signal, which is obtained by modulating the carrier signal of the predetermined frequency with the transmitted data.

[0027] The data transmitted by the data signal consists of a preamble indicating the start of the data signal and the data requested by the uplink signal US, as shown in Figure 3(b). Error detection data, such as a cyclic redundancy check (CRC) code, may be placed at the end of the data signal.

[0028] The preamble is predetermined data shared in advance between the sensor controller 2 and the active pen PE, and is used by the sensor controller 2 to detect a data signal from a received signal. The data requested by the uplink signal US includes the pen pressure value indicating the pressure detected by the pressure sensor 22, switch information indicating the on / off state of the switch 23, and the pen ID stored in the memory of the control circuit 24. The control circuit 24 acquires data from the pressure sensor 22 and other sources according to the commands contained in the received uplink signal US and places it in the data signal.

[0029] Figure 4 illustrates the modulation process of a data signal. As shown in the figure, the control circuit 24 first acquires a symbol sequence that constitutes the data to be transmitted. A symbol is a unit of information used for modulation and includes values ​​that are converted into bit sequences and values ​​that are not converted into bit sequences. The "P" shown is an example of a symbol value that is not converted into a bit sequence. The values ​​that are converted into bit sequences correspond to bit sequences of a predetermined number of bits, and Figure 4 shows an example corresponding to a 4-bit bit sequence.

[0030] The control circuit 24 stores a table in advance that associates symbol values ​​with spreading codes (chip sequences), and converts each symbol constituting the transmission data into a chip sequence according to this table. Subsequently, the control circuit 24 Manchester encodes the obtained chip sequence so that no 0s or 1s are consecutive, and then modulates the carrier signal with the Manchester encoded chip sequence. Figure 4 shows an example in which this modulation is performed using BPSK (Binary Phase Shift Keying), but other modulation methods may be used. The waveform of the carrier signal thus modulated constitutes the waveform (transmission waveform) of the downlink signal DS transmitted from the pen tip electrode 21.

[0031] Returning to Figure 2, the detection of the active pen PE will be outlined using the example of bidirectional communication between the sensor controller 2 and the active pen PE. The sensor controller 2, which has not yet detected the active pen PE, periodically transmits an uplink signal US using one or both of the multiple linear conductors 4x and multiple linear conductors 4y. Upon receiving this uplink signal US, the active pen PE first transmits a downlink signal DS of the type shown in Figure 3(a). The sensor controller 2 sequentially scans all of the multiple linear conductors 4x and multiple linear conductors 4y to obtain the signal level of this downlink signal DS in each linear conductor 4x,4y. Then, based on the distribution, it derives the position of the active pen PE and stores it in memory (global scan).

[0032] Subsequently, the active pen PE, having received the uplink signal US again, transmits a downlink signal DS of the type shown in Figure 3(b). The sensor controller 2, upon receiving this downlink signal DS, first receives a burst signal using only a predetermined number of linear conductors 4x,4y located near the location of the active pen PE stored in memory, and derives a new location of the active pen PE based on the distribution of the signal levels. Then, it updates the location of the active pen PE stored in memory based on the derived location (local scan). Next, the sensor controller 2 acquires the data transmitted by the active pen PE by receiving a data signal using the linear conductor 4x or linear conductor 4y closest to the location of the active pen PE. The location stored in memory and the acquired data are then sequentially output from the sensor controller 2 to the host processor 3, as described above.

[0033] To briefly explain the case where the active pen PE transmits a downlink signal DS in one direction to the sensor controller 2, the active pen PE is configured to periodically transmit a downlink signal DS of the type shown in Figure 3(b). When the sensor controller 2 has not yet detected the active pen PE, it performs the global scan described above based on this downlink signal DS. After the position of the active pen PE is temporarily stored in memory through the global scan, the sensor controller 2 then performs the local scan and receives data signals described above based on the downlink signal DS transmitted from the active pen PE. In this way, the sensor controller 2 can update the position of the active pen PE and acquire the data transmitted by the active pen PE, just as in the case where the sensor controller 2 and the active pen PE communicate bidirectionally. The position stored in memory and the acquired data are sequentially output from the sensor controller 2 to the host processor 3, just as in the case where the sensor controller 2 and the active pen PE communicate bidirectionally.

[0034] Returning to Figure 1, when the active pen PE transmits a downlink signal DS, the downlink signal DS is also transmitted to the user's body holding the active pen PE through the housing of the active pen PE. As a result, if the user has their hand on the panel surface 1a, the downlink signal DS is also transmitted from the user's palm PA, as shown in Figure 1. This results in two peaks in the signal level detected during the global scan, which may prevent the sensor controller 2 from correctly detecting the position of the active pen PE. Therefore, in this embodiment, the sensor controller 2 is configured to take advantage of the fact that the downlink signal DS includes a predetermined waveform portion (i.e., a transmission waveform corresponding to the preamble) that is shared in advance between the sensor controller 2 and the active pen PE, and to determine whether the phase of the received downlink signal DS matches the phase shared in advance between the sensor controller 2 and the active pen PE based on the phase of this predetermined waveform portion, thereby excluding the palm PA contact position from the indicated position of the active pen PE.

[0035] Furthermore, in order to achieve this exclusion, it is necessary to determine the phase of the downlink signal DS before determining the instruction position of the active pen PE. To do this, it is necessary to detect multiple positions using a global scan and perform a local scan and receive data signals at each of these positions. Therefore, in this embodiment, the receiving unit within the sensor controller 2 is configured to enable such processing.

[0036] In the following, we will first explain the relationship between the downlink signal DS and its phase, referring to Figures 5 to 7. Then, we will explain the configuration of the receiving unit provided in the sensor controller 2, referring to Figure 8. Finally, we will explain in detail the processing performed by the sensor controller 2, referring to Figure 9.

[0037] FIG. 5 is a diagram showing an equivalent circuit of the active pen PE, the palm PA, and the sensor electrode group兼display 4. In this equivalent circuit, the human body is regarded as a perfect conductor and in a floating state. As shown in FIG. 5, this equivalent circuit is composed of four capacitances C1 to C4. Capacitance C1 is the coupling capacitance between the linear conductor 4y closest to the pen tip electrode 21 (hereinafter referred to as "linear conductor 4y-1") and the pen tip electrode 21. Capacitance C2 is the coupling capacitance between the linear conductor 4y closest to the palm PA (hereinafter referred to as "linear conductor 4y-2") and the palm PA. Capacitances C3 and C4 are the coupling capacitances between the linear conductors 4y-1 and 4y-2 and the ground terminal of the electronic device 1, respectively.

[0038] Let the potential of the pen tip electrode 21 with respect to the ground terminal of the electronic device 1 be V T and the potential of the palm PA with respect to the ground terminal of the electronic device 1 be V B and the potential of the downlink signal DS be V S Then, they have the relationship shown in the following formula (1). V T -V B =V S ···(1)

[0039] Also, let the impedance between the ground terminal of the electronic device 1 and the pen tip electrode 21 be Z TG and the impedance between the ground terminal of the electronic device 1 and the palm PA be Z BG Then, from Kirchhoff's first law, the following formula (2) holds. V T / Z TG +V B / Z BG =0 ···(2)

[0040] From formulas (1) and (2), the following formulas (3) and (4) are obtained. V T =-V S Z BG / (Z TG +Z BG ) ···(3) V B =V S ZBG / ( Z TG + Z BG ) ···(4)

[0041] From equations (3) and (4), the potential V of the pen tip electrode 21 is obtained. T and the potential V of the palm PA B It is understood that these two are in opposite phases to each other. The sensor controller 2 in this embodiment utilizes this relationship to exclude the contact position of the palm PA from the indicated position of the active pen PE.

[0042] Figures 6(a) and 7(a) show the potential V simulated using the equivalent circuit of Figure 5. T ,V B This figure shows the time evolution of [the voltage]. Figures 6(b) and 7(b) also show the potential V of the linear conductor 4y-1 simulated using the equivalent circuit in Figure 5. 4y-1 and the potential V of the linear conductor 4y-2 4y-2 This figure shows the time evolution of the bond capacitance C1. However, Figures 6(a) and 6(b) show the case where the bond capacitance C1 is 1 pF, and Figures 7(a) and 7(b) show the case where the bond capacitance C1 is 0.1 pF. In all figures, the bond capacitances C2, C3, and C4 are assumed to be 3 pF, 100 pF, and 100 pF, respectively.

[0043] As shown in Figures 6(a) and 7(a), the potential V of the pen tip electrode 21 T and the potential V of the palm PA B These are in opposite phases to each other. This is the result shown in equations (3) and (4) above. On the other hand, from the results in Figures 6(a) and 7(a), the potential V B The amplitude is the potential V T It is understood that this becomes smaller compared to the amplitude.

[0044] In contrast, as shown in Figures 6(b) and 7(b), the potential V of the linear conductor 4y-1 4y-1 The potential V of the linear conductor 4y-2 4y-2 In that they are in opposite phases to each other, the potential V T and potential V B Similar to, but with potential VT ,V B Unlike the previous case, the amplitude is the same value. The sensor controller 2 actually detects the potential V T ,V B Instead, potential V 4y-1 ,V 4y-2 Therefore, from the results in Figures 6(b) and 7(b), it can be understood that it is not possible to distinguish between the indicated position of the active pen PE and the contact position of the palm PA by looking only at the amplitude of the detected potential. Thus, in the sensor controller 2 according to this embodiment, the potential V 4y-1 ,V 4y-2 By referring to the phase, the contact position of the palm PA is excluded from the indicated position of the active pen PE.

[0045] Figure 8 shows the configuration of the sensor controller 2 according to this embodiment. However, the figure only shows the part of the various components provided in the sensor controller 2 that is related to receiving the downlink signal DS. As shown in the figure, the sensor controller 2 according to this embodiment is composed of an MCU (Micro Control Unit) 10, a memory 11, n receiving units 12-1 to 12-n, and a selection unit 13.

[0046] The MCU10 is a processor that reads and executes programs stored in the memory 11. The processing performed by the MCU10 includes the control of various parts within the sensor controller 2. The memory 11 is a storage device composed of volatile memory, non-volatile memory, or both, and stores programs executed by the MCU10, as well as functioning as the MCU10's work memory. This function as work memory includes the ability to temporarily store one or more locations derived by the MCU10 as a result of global scans and local scans. The memory 11 also plays a role in storing the same table of spreading codes (chip sequences) as those stored in the control circuit 24 of the active pen PE.

[0047] Each receiving unit 12-1 to 12-n is configured to include a buffer 30, a bandpass filter 31, an analog-to-digital (AD) converter 32, a demodulation unit 33, and a correlation calculation unit 34. The buffer 30 is connected to one of the multiple linear conductors 4x, 4y via a selection unit 13, and plays the role of amplifying the current induced in the connected linear conductor and supplying it to the bandpass filter 31.

[0048] The bandpass filter 31 is a filter circuit that extracts only the signal in a predetermined frequency band to which the downlink signal DS belongs from the output current of the buffer 30. The bandpass filter 31 plays a role in removing low-frequency noise and harmonic noise from the output current of the buffer 30.

[0049] The AD conversion unit 32 is a circuit that acquires the received level value of the downlink signal DS by sampling and quantizing the output signal of the bandpass filter 31. The sampling frequency of the AD conversion unit 32 is set to a frequency that is sufficiently higher than the frequency of the downlink signal DS. The AD conversion unit 32 is configured to sequentially supply the acquired received level value to the MCU 10 and the demodulation unit 33.

[0050] The demodulation unit 33 is a circuit that acquires a series of chip sequences transmitted by the active pen PE by demodulating the downlink signal DS based on a series of received level values ​​output from the AD conversion unit 32. The series of chip sequences acquired by the demodulation unit 33 is supplied to the correlation calculation unit 34.

[0051] The correlation calculation unit 34 is a circuit that reconstructs the sequence of symbols that constitute the downlink signal DS by calculating the correlation between a series of chip sequences supplied from the demodulation unit 33 and each of a plurality of chip sequences pre-stored in the memory 11. The sequence of symbols reconstructed by the correlation calculation unit 34 is supplied to the MCU 10.

[0052] The selection unit 13 is a multiplexer provided between each of the multiple linear conductors 4x, 4y and the receiving units 12-1 to 12-n. The connection state of the selection unit 13 is controlled by the MCU 10. Specifically, when performing a global scan, the MCU 10 first controls the selection unit 13 so that each of the multiple linear conductors 4x, 4y is sequentially connected to the receiving unit 12-1. Then, the MCU 10 obtains the distribution of the received level of the downlink signal DS by referring to the received level values ​​sequentially output from the AD conversion unit 32 of the receiving unit 12-1, and derives the position of the peak of this distribution. If there are multiple peaks in the distribution, multiple positions will be derived. The MCU 10 stores one or more derived positions in the memory 11 as the detection result of the global scan.

[0053] When performing a local scan, the MCU 10 assigns a different receiving unit 12-k (where k is one of 1 to n) to each of the one or more locations stored in the memory 11. For each assigned receiving unit 12-k, the selection unit 13 is controlled so that a predetermined number of linear conductors 4x, 4y located near the corresponding location are sequentially connected. As a result, the MCU 10 obtains the distribution of the received level of the downlink signal DS for each receiving unit 12-k by referring to the received level values ​​sequentially output from the AD conversion unit 32 of the receiving unit 12-k. The MCU 10 then derives the peak position of this distribution for each receiving unit 12-k and overwrites the corresponding location stored in the memory 11 with the derived position.

[0054] When receiving a data signal, the MCU 10 assigns a different receiving unit 12-k to each of the one or more positions stored in the memory 11, and controls the selection unit 13 so that the linear conductor 4x (or linear conductor 4y) closest to the corresponding position is connected to each assigned receiving unit 12-k. As a result, the MCU 10 refers to the symbol sequence output sequentially from the correlation calculation unit 34 of each receiving unit 12-k and first attempts to detect the preamble. At this time, in addition to the preamble that has been stored in advance, the MCU 10 also attempts to detect the part of the symbol sequence that corresponds to the preamble when the phase of the downlink signal DS input to the receiving unit 12-k is inverted (hereinafter referred to as the "inverted preamble"). If the preamble is detected, the MCU 10 determines that the phase of the downlink signal DS matches the phase previously shared between the sensor controller 2 and the active pen PE, while if the inverted preamble is detected, the MCU 10 determines that the phase of the downlink signal DS does not match (is inverted) the phase previously shared between the sensor controller 2 and the active pen PE.

[0055] Based on the results of the determination, the MCU 10 acquires the transmission data of the active pen PE based on the symbol sequence output from the receiving unit 12-k that receives the downlink signal DS, which it has determined has a phase that matches the phase previously shared between the sensor controller 2 and the active pen PE. The MCU 10 outputs this data to the host processor 3 along with the position stored in the memory 11 for the receiving unit 12-k. Since other positions are not output to the host processor 3, this makes it possible to exclude the palm PA contact position from the active pen PE's indicated position.

[0056] Figure 9 is a flowchart showing the pen detection process performed by the sensor controller 2. As shown in the figure, the sensor controller 2 first enters discovery mode to detect the active pen PE (step S1), and performs a global scan that sequentially scans all of the multiple linear conductors 4x, 4y (step S2). The sensor controller 2 determines whether or not it has detected a downlink signal DS as a result of performing this global scan (step S3), and if it has not been detected, it returns to step S2 and repeats the global scan.

[0057] On the other hand, if it is determined in step S3 that detection has occurred, the sensor controller 2 derives one or more positions based on the results of the global scan and stores them in the memory 11 shown in Figure 8 (step S4). The details of this deriving process are as described above. After completing step S4, the sensor controller 2 enters an operation mode that accepts pen input from the detected active pen PE (step S5).

[0058] When the sensor controller 2 enters operation mode, it performs the above-described local scan in parallel using the receiving units 12-1 to 12-n shown in Figure 8 for each of the one or more locations stored in memory 11 (step S6). The sensor controller 2 then determines whether or not it has detected the downlink signal DS as a result of this local scan (step S7). If it has not detected it, it returns to discovery mode and continues processing. On the other hand, if it determines that it has detected it, it derives the location based on the result of the local scan and overwrites the location stored in memory 11 (step S8). The details of this derivation are also as described above. Here, depending on the location, it is possible that no peak is detected in the distribution of the received level of the downlink signal DS. In such cases, the sensor controller 2 performs a process to erase the corresponding location from memory 11.

[0059] Next, the sensor controller 2 receives data signals at each location stored in the memory 11 (step S9). Specifically, it acquires the symbol sequence output from each receiving unit 12-k shown in Figure 8. Then, it performs a phase determination on each of the received data signals (symbol sequences) (step S10, determination step). As described above, this determination is performed by attempting to detect a preamble and an inverted preamble in the symbol sequence output from each receiving unit 12-k. If a preamble is detected, it is determined that the phase of the downlink signal DS matches the phase previously shared between the sensor controller 2 and the active pen PE. On the other hand, if an inverted preamble is detected, it is determined that the phase of the downlink signal DS does not match (is inverted) the phase previously shared between the sensor controller 2 and the active pen PE.

[0060] Next, the sensor controller 2 acquires the transmission data from the active pen PE based on the data signal that it determined in step S10 to have a matching phase with the downlink signal DS (step S11), and outputs it to the host processor 3 along with the position stored in the memory 11 corresponding to the data signal (step S12, output step). Other positions stored in the memory 11 are not output. As a result, only the position derived based on the downlink signal DS having a phase that matches the phase previously shared between the sensor controller 2 and the active pen PE, and the data acquired based on the downlink signal DS, are output to the host processor 3. The sensor controller 2 then returns to step S6 and continues processing.

[0061] As described above, in the palm rejection method performed by the sensor controller 2 according to this embodiment, the phase of the downlink signal DS is determined in step S10, so the position derived based on the downlink signal DS detected via the human body can be identified. Therefore, it becomes possible to exclude the palm PA contact position from the indicated position of the active pen PE, without depending on the detection result by a process different from the detection of the active pen PE, such as touch detection.

[0062] Although preferred embodiments of the present invention have been described above, the present invention is not limited in any way to these embodiments, and it goes without saying that the present invention can be implemented in various forms without departing from its essence.

[0063] For example, in the above embodiment, an example was described in which the MCU 10 attempts to detect the preamble and inverted preamble in the symbol sequence output from each receiver 12-k. However, this process may be omitted when the sensor controller 2 and the active pen PE communicate bidirectionally. That is, when the sensor controller 2 and the active pen PE communicate bidirectionally, the sensor controller 2, which is entered into operation mode, is synchronized with the active pen PE. Therefore, the timing at which the downlink signal DS includes the preamble can be known in advance, and the phase of the downlink signal DS can be determined by determining whether the preamble or the inverted preamble was output from each receiver 12-k at that timing.

[0064] Furthermore, although the above embodiment described an example in which the phase of the downlink signal DS is determined based on the phase of the preamble, any predetermined data shared in advance between the sensor controller 2 and the active pen PE can be similarly used to determine the phase of the downlink signal DS, even if it is data other than the preamble. For example, if the data signal includes start bits and stop bits, the phase of the downlink signal DS may be determined based on the phase of one or both of these bits.

[0065] Furthermore, if the data signal includes error detection data, it may be determined that the phase of the downlink signal DS is inverted if errors are detected consecutively. Alternatively, if an error is detected, the chip sequence output from the demodulation unit 33 may be inverted and re-inputted to the correlation calculation unit 34 to obtain a new symbol sequence, and if the obtained symbol sequence includes a preamble, it may be determined that the phase of the downlink signal DS is inverted.

[0066] Furthermore, although the above embodiment describes an example in which multiple receiving units 12-1 to 12-n are provided in the sensor controller 2, it is also possible to provide only one receiving unit. In this case, it will not be possible to determine the phase of the downlink signal DS in parallel at multiple locations, but it will be possible to determine at least whether the received downlink signal DS was transmitted from the pen tip electrode 21 or the palm PA. [Explanation of Symbols]

[0067] 1 Electronic equipment 1a Panel surface 2 Sensor Controller 3 Host Processors 4. Sensor electrode group and display 4m island-shaped conductor 4x, 4y linear conductor 10 MCU 11 memory 12 Receiver 13 Selection Section 20 Core body 21 Pen tip electrode 22 Pressure Sensor 23 switches 24 Control circuits 25 batteries 30 buffers 31 Bandpass Filter 32 Analog-to-Digital (AD) Conversion Section 33 Demodulation Unit 34 Correlation Calculation Unit DS Downlink Signal PA Palm PE Active Pen US Uplink Signal

Claims

1. A palm rejection method performed by a sensor controller connected to multiple sensor electrodes and detecting a downlink signal transmitted from an active pen, The downlink signal includes a predetermined waveform portion that has been shared in advance between the sensor controller and the active pen. The portion of the predetermined waveform is the portion obtained by modulating a preamble that has been previously shared between the sensor controller and the active pen. A determination step of determining whether the phase of the portion of the predetermined waveform included in the detected downlink signal is inverted, If the determination step determines that the signal is not inverted, the output step outputs the position of the active pen derived based on the level distribution of the downlink signal at the multiple sensor electrodes, A method that includes this.

2. The output step, if it is determined by the determination step that the signal is inverted, does not output the position of the active pen derived based on the level distribution of the downlink signal at the multiple sensor electrodes. The method according to claim 1.

3. The determination step determines that the phase of the portion of the predetermined waveform included in the detected downlink signal is not inverted if the symbol sequence obtained by demodulating the downlink signal includes the preamble, and determines that the phase of the portion of the predetermined waveform included in the detected downlink signal is inverted if the symbol sequence includes an inverted preamble, which is the portion of the symbol sequence obtained by demodulating the downlink signal that corresponds to the preamble if the phase of the portion of the predetermined waveform included in the downlink signal is inverted. The method according to claim 1 or 2.

4. The sensor controller and the active pen are configured to communicate bidirectionally in a synchronized state. The determination step involves determining whether the symbol sequence obtained by demodulating the downlink signal contains the preamble or the inverted preamble at the timing when the downlink signal contains the preamble. The method according to claim 3.

5. The sensor controller includes a plurality of receiving units, Each of the aforementioned receiving units is configured to receive the downlink signal, The determination step involves determining whether the phase of the portion of the predetermined waveform included in the downlink signal detected in each of the plurality of receiving units is inverted. The output step outputs the position of the active pen derived based on the level distribution of the downlink signal at the plurality of sensor electrodes for which the determination step determines that the phase of the predetermined waveform portion is not inverted, while not outputting the position of the active pen derived based on the level distribution of the downlink signal at the plurality of sensor electrodes for which the determination step determines that the phase of the predetermined waveform portion is inverted. The method according to any one of claims 1 to 4.

6. The aforementioned sensor controller Based on the reception level value of the downlink signal at each of the aforementioned plurality of sensor electrodes, a plurality of positions are derived. A different receiving unit is assigned to each of the derived multiple locations. For each of the assigned receiving units, connect the sensor electrode closest to the corresponding position. The determination step involves determining whether the phase of a predetermined waveform portion included in the downlink signal detected by the receiving unit connected to any of the sensor electrodes is inverted. The method according to claim 5.

7. A sensor controller connected to multiple sensor electrodes, which detects a downlink signal of a predetermined frequency or waveform transmitted from an active pen, The downlink signal includes a predetermined waveform portion that has been shared in advance between the sensor controller and the active pen. The portion of the predetermined waveform is the portion obtained by modulating a preamble that has been previously shared between the sensor controller and the active pen. Determine whether the phase of the predetermined waveform portion included in the detected downlink signal is inverted. If it is determined that the signal is not inverted, the position of the active pen, derived based on the level distribution of the downlink signal across the multiple sensor electrodes, is output. Sensor controller.

Images