JPH012121A - Position indicator tuning circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of application in the mahjong industry) The present invention provides a system for identifying the state of a position indicator, which detects the designated position of the position indicator and identifies the state of the position indicator. It concerns the tuning path.

Prior Art) Prior to filing this application, the applicant filed Japanese Patent Application No. 6121569.
No. 6 (filed on September 16, 1986) hereinafter referred to as Prior Application 1. ), by exchanging radio waves with the tablet standing indicator, the state of the position indicator, for example, the state of the position indicator based on the coordinates to be input (hereinafter referred to as the pen down state) is identified ( We propose a method for detecting
Also, Patent Application No. 1988-213970 (September 1, 1986)
20) (hereinafter referred to as Prior Application 2), proposed a device that detects the specified position of a position indicator and identifies its state by exchanging radio waves between a tablet and a position indicator.

To briefly explain the content of Prior Application 1, a signal of a predetermined frequency is applied to an antenna coil provided around the coordinate input range of a tablet to emit radio waves, and the radio waves are received by a tuned circuit provided in a position indicator. At this time, by causing the antenna coil, which has stopped supplying the signal, to receive the radio waves emitted from the coil of the tuned circuit that has resonated (tuned), an induced voltage is generated in the antenna coil, and the tuned circuit is The phase of the signal in the circuit is changed in accordance with the change in the state of the position indicator, and the change in the phase of the signal in the tuned circuit is detected from the phase of the induced voltage, thereby determining the state of the position indicator. It was designed to identify the

In addition, to briefly explain the contents of Prior Application 2, a signal of a predetermined frequency is applied to the loop coil of - of a tablet formed by a large number of loop coils arranged in parallel in the position detection direction.
A radio wave is emitted from the loop coil, and the radio wave is received by a tuning circuit installed in the position indicator, and at this time, resonance (tuning) occurs.
By making the - loop coil, which has stopped supplying the signal, receive radio waves emitted from the coil of the tuned circuit, an induced voltage is generated in the - loop coil, and these are applied to the multiple loop coils. Iteratively detects the position where the voltage value is maximum among the many induced voltages generated in each loop coil, that is, the designated position of the position indicator, and determines the phase of the signal in the tuned circuit to indicate the position. The state of the position indicator is determined by detecting a change in the phase of the signal in the tuned circuit from the phase of the induced voltage, thereby identifying the state of the position indicator. be.

When changing the phase of the signal in the tuned circuit, there are cases where the phase is delayed and cases where the phase is advanced, and in either case, it is possible to detect the change in the phase and identify the state of the position indicator. It is possible.

Conventionally, when delaying the phase, in a tuned circuit whose basic configuration is a coil and a capacitor connected in series with the coil, another capacitor is connected in parallel to the capacitor via a switch having a contact that is connected during operation. When the position indicator is in the pen-down state, that is, when the switch is operated, the resonant frequency is reduced by increasing the capacitance value in the circuit, substantially delaying the phase of the signal in the circuit, and reducing the induced voltage. The phase was delayed.

On the other hand, to advance the phase, in a tuned circuit whose basic configuration is a coil and a capacitor connected in series with the coil, another coil is connected in parallel to the coil via a switch that has a contact that is connected during operation. , when the position indicator is in the pen-down state, that is, when the switch is operated, the resonant frequency is increased by -130° by decreasing the induction value in the circuit, and the phase of the signal in the circuit is substantially advanced. This was done to advance the phase of the induced voltage.

(Problems to be Solved by the Invention) However, it is generally difficult to obtain a coil with a desired induction value, and the induction value of the coil tends to change depending on the ambient temperature, and furthermore, the coil has a large loss. As mentioned above, when trying to advance the phase of the signal in the tuned circuit by connecting other coils in parallel, it is difficult to accurately set and maintain the leading phase angle. Moreover, as the loss changes, the attenuation constant in the tuned circuit also changes, and the level of the induced voltage changes, making it difficult to accurately detect the phase angle.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems and provide a tuning circuit for a position indicator that can advance the phase of a signal without using a coil.

(Means for Solving the Problems) In order to solve the above problems, the present invention includes a coil and a capacitor connected in series to the coil, receives radio waves transmitted from the tablet side, and at this time, In the tuning circuit of the position indicator, which generates radio waves based on the signals generated in the circuit and sends them back to the tablet side, an off switch equipped with a contact that disconnects when activated, and the off switch connected in series. A phase shift circuit consisting of a capacitor of
Provided at least one.

(Function) According to the present invention, radio waves emitted from the tablet side are received by the tuning circuit of the position indicator, but at this time, when the position indicator enters a predetermined state and the off switch operates, other The capacitor is disconnected from the circuit, which reduces the capacitance value within the circuit, increases the resonant frequency, and substantially advances the phase of the signal within the circuit.

(Embodiment) FIG. 1 shows a first embodiment of a tuning circuit for a position indicator according to the present invention. In the figure, 1 is a coil with a core, 2 and 3 are capacitors, and 4 is an off switch.

The coil 1 and capacitor 2 are connected in series with each other. The off switch 4 has a contact that is connected during non-operation and disconnected during operation, and the capacitor 3 is connected in parallel to the capacitor 2 via the off switch 4. These coil 1 and capacitors 2 and 3 constitute a well-known resonant circuit, and the sum of the induction value of coil 1 and the capacitance values of capacitors 2 and 3 is equal to the voltage and current at a predetermined frequency fO. The phase is set to a value that resonates (tunes) in the same phase. Also, capacitor 2
The ratio of the capacitance values of and 3 operates the off switch 4, and when the contact is disconnected, the phase of the current in the above-mentioned resonant circuit is advanced by a predetermined angle, and the phase of the received signal, which will be described later, is advanced by 45 degrees, for example. set to the value.

FIG. 2 shows an example of a position pointing device equipped with the above-mentioned tuning circuit. (referred to as Ben) 10 is shown. The ben 10 includes a pen shaft 11 made of a non-metallic material such as a synthetic resin, and a core 12 for writing such as a ballpoint pen, and a through hole in which the core 12 can be slidably accommodated from the tip end thereof. A bar magnet (magnetic generator) 13, a coil spring 14, and a cored coil 1. The tuning circuit consisting of the capacitors 2 and 3 and the off switch 4, for example 15, is integrated and built-in, and a cap 16 is attached to the rear end. In addition, off switch 4
When the tip of the core body 12 is pushed into the pen shaft 11 by pressing it against the input surface of a tablet (to be described later), the rear end is pressed by the coil spring 14 to operate, and the contact is cut.

FIG. 3 shows an outline of a coordinate input device using the pen 10. In the figure, 20 is a tablet, 30 is a position detection circuit, and 40 is a timing control circuit.

The tablet 20 has a tablet main body 22 and an antenna coil 23 attached to a non-magnetic metal casing 21, and the tablet main body 22 is connected to a position detection circuit 30.
Further, the antenna coil 23 is connected to a timing control circuit 40.

The tablet main body 22 is driven by a position detection circuit 30 and constitutes a detection section that detects the position designated by the bar magnet 13 of the pen 10.
It is stored almost in the center of 1. Note that a frame 24 drawn on the top panel 21a of the housing 21 indicates the coordinate input range.

The tablet main body 22 and position detection circuit 30 include:
For example, patent application No. 59-3224 filed by the present applicant.
No. 4 “Position detection device” (Japanese Patent Application Laid-Open No. 60-176133
(see Japanese Patent Application No. 1982-238532), or the "coordinate position detection device" of Japanese Patent Application No. 1982-129616 (see Japanese Patent Application Laid-Open No. 129616/1982).

The antenna coil 23 is formed by disposing an insulated conductor on the coordinate input range of the tablet body 22, that is, on the surface of the top panel 21a of the housing 21 around the frame 24. Although the coil is shown as one turn in the drawing, it actually consists of several turns.

The timing control circuit 40 is for detecting the operating state of the off switch 4 and identifying the state of the ben 10, and its detailed configuration is shown in FIG. 4 together with the tuning circuit 15.

In the figure, 401 is a control circuit, 402 is a timing circuit, 403 is a low-pass filter (LPF), 404 is a drive circuit, 405 is a transmission/reception switching circuit, 406 is an amplifier, and 407
408 is a reception timing switching circuit, and 408 is a bandpass filter (B
PF), 409.

410 is a phase detector (PSD), 411, 41
2 is a low pass filter (LPF).

FIG. 5 is a signal waveform diagram at each part of FIG. 4. Below, the state identification operation of Ben 10 will be explained.

The control circuit 401 is composed of a well-known microprocessor, etc., and controls the timing circuit 402, performs analog-to-digital (A/D) conversion of the output values from the low-pass filters 411 and 412, and further performs arithmetic processing to be described later. , calculates the phase difference between voltage and current in the tuned circuit 15 of Ben 10, identifies the operating state of the off switch 4, that is, the state of Ben 10, and sends this to the position detection circuit 30.

The timing circuit 402 generates a rectangular wave signal A1 with a predetermined frequency fO, a signal B obtained by advancing the phase of the rectangular wave signal A by 90 degrees, a transmission/reception switching signal C and a reception timing signal with a predetermined frequency fk. The rectangular wave signal A is sent to a phase detector 409.
The rectangular wave signal B is sent to the phase detector 410, the rectangular wave signal B is sent to the phase detector 410, and the transmission/reception switching signal C is sent to the transmission/reception switching signal. The reception timing signal is sent to the circuit 405, and the reception timing signal is sent to the reception timing switching circuit 4.
Sent on 07.

The sine wave signal E is converted into a balanced signal by a drive circuit 404, and is further sent to a transmission/reception switching circuit 405. Based on the transmission/reception switching signal C, the transmission/reception switching circuit 405 selects one of the driving circuit 404 and the amplifier 406. In order to alternately connect one side to the antenna coil 23, the antenna coil 23
is input with a signal F that outputs or does not output a sine wave signal of frequency fO every time T (-1/2fk),
The signal F is transmitted from the antenna coil 23 as a radio wave.

At this time, if the Ben 10 is held in a substantially upright state, that is, in the use state, within the coordinate input range 24 of the tablet 20, the radio wave excites the coil 1 of the Ben 10, and the tuned circuit 15 causes the An induced voltage G synchronized with the signal F is generated.

Thereafter, the antenna coil 23 is
When the signal is switched to the amplifier 40B side, that is, when the reception period begins, the radio wave from the antenna coil 23 immediately disappears, but the induced voltage G gradually attenuates in accordance with the loss in the tuning circuit 15.

On the other hand, the current flowing through the tuning circuit 15 based on the induced voltage G causes the coil 1 to emit radio waves. Since the radio waves reversely excite the antenna coil 23, an induced voltage due to the radio waves from the coil 1 is generated in the antenna coil 23. The induced voltage is sent from the transmission/reception switching circuit 405 to the amplifier 40G only during the reception period, is amplified, becomes a reception signal H, and is further sent to the reception timing switching circuit 407.

The reception timing switching circuit 407 is essentially sent. A reception timing signal, which is an inverted signal of the reception switching signal C, is input, and the reception signal H is output during the period when the signal is high (H) level, and nothing is output during the period when the signal is at low (L) level. Therefore, its output has a signal E (substantially the received signal H
) is obtained and the signal I is sent to a bandpass filter 408.

The bandpass filter 408 is a filter having a passband centered at the frequency fO, and the signal J having an amplitude corresponding to the energy of the frequency fO acid component in the signal I (strictly speaking, several signals I are filtered by the bandpass filter). 408 and in a converged state) is sent to phase detectors 409 and 410.

The rectangular wave signals A and B are input as detection signals to the phase detectors 409 and 410, respectively, and at this time,
Assuming that the phase of the signal J almost matches the phase of the rectangular wave signal A, the phase detector 409 outputs 1 as a signal that is just inverted to the positive side of the signal J, and the phase detector 410 outputs 1 as a signal that is just inverted to the positive side. and 2 is output for a signal having a symmetrical waveform on the negative side.

1 is a low-pass filter 41 with a sufficiently low cutoff frequency for the signal.
1, the control circuit 40 converts the signal J into a DC signal L1 having a voltage value corresponding to approximately 1/2 of the amplitude of the signal J, for example, vl.
1, and the signal 2 is also passed through a similar low-pass filter 4.
12, it is converted into a DC signal L2 and sent to the control circuit 401, but here, since the signal has the same positive and negative components in 2, the voltage value of the output of the low-pass filter 412 is 0 [Vl becomes.

The control circuit 401 A/D converts the output values of the low-pass filters 411 and 412, here signals L1 and L2, and further uses these digital values to perform calculation processing according to the following equation (1), and then outputs the output values from the phase detectors 409 and 412. Signal added to 410,
Here, the phase difference θ between J and the rectangular wave signal A is calculated.

θ−j a n” (VQ /VP ) −・
(1) Here, VP is the digital value corresponding to the output of the low-pass filter 411, and vQ is the digital value corresponding to the output of the low-pass filter 411.
The digital value corresponding to the output of 2 is shown. For example, in the case of the signal J mentioned above, the voltage value of the signal L1 is Vl, but
Since the voltage value of the signal L2 is O[v, that is, VQ-0, the phase difference is θ-0''.

The submerged phase difference θ represents the phase difference between the received signal H (or signal ■) and the rectangular wave signal A, in other words, the phase difference between the voltage and current in the tuning circuit 15, and the phase difference θ
-θ″, the voltage and current in the tuned circuit 15 are in phase, and the contacts of the off switch 4 are connected, that is, the off switch 4 is not operating and the pen 10 is not bent down. (Note that the phase difference between the received signal H (or signal I) and the rectangular wave signal A and the tuning circuit 15
The phase difference between voltage and current at is not the same except for the case of θ'', but there is a fixed constant relationship.)

Furthermore, the phase of the signal J is 4 from the bandpass filter 408.
Assuming that a signal J- which is 5@advanced is output, the signal J' is sent to the phase detectors 409 and 410 as before,
However, since the ratio of the positive and negative side components of the signal Kl' and the ratio of the positive and negative side components of the signal 2' are equal, 1° and 2° are filtered by low-pass filters 411 and 412, respectively, to output signals L1° and L having the same voltage value, for example, Vl.
2' and is sent to the control circuit 401.

Similarly to the above, the control circuit 401 converts the signals LL' and L2° into A.
/D conversion and the arithmetic processing of equation (1) above is performed, but the voltage values of the signals L1° and L2' are both v2, and VP-V
Q, so the phase difference is θ-45″.

Therefore, the phase difference θ between the received signal and the rectangular wave signal A at this time is
-45°, the phase of the current in the tuned circuit 15 is ahead of the phase of the voltage by the predetermined angle, and the contact of the off switch 4 is disconnected.
It can be seen that the pen 10 is operating and the pen 10 is in the pen down state.

In this way, in the control circuit 401, the low-pass filter 41
The phase difference between the received signal and the rectangular wave signal A is calculated from the output values of 1 and 412, and based on this, the phase difference between the voltage and current in the tuning circuit 15 can be detected, and the operating state of the off switch 4, that is, the pen It is possible to accurately identify whether or not the pen 10 is in the pen-down state.

Note that the information indicating whether or not the pen 10 identified here is in the pen-down state is information that specifies the value that should actually be input among the coordinate values detected by the tablet 20 and the position detection circuit 30. used.

Further, the pen 10 equipped with the tuning circuit 15 can be similarly used for a device that performs position detection based on the reflected radio waves in the tuning circuit 15, as described in the prior art section, but in this case, a bar magnet is used. 13 becomes unnecessary.

FIG. 6 shows a second embodiment of the tuning circuit of the present invention, in which two leading phase angles and two lagging phase angles are realized. In the same figure, 51 is a coil with a core, 52, 53, 54, 55° 56 is a capacitor, 57.
58 is a switch, and 59° and 60 are off switches. Coil 51 and capacitor 52 are connected in series with each other, capacitors 53 and 54 are connected in parallel with capacitor 52 via switches 57 and 58, and furthermore,
Capacitors 55 and 56 are connected in parallel to capacitor 52 via off switches 59 and 60.

At the predetermined frequency fO, the sum of the induction value of the coil 51 and the capacitance values of the capacitors 52, 55 and 56 is:
The voltage and current phases are set to values that resonate with the same phase. Further, the capacitance value of the capacitor 55 is set to a value that, when the off switch 59 is operated and the cone capacitor 55 is disconnected, causes the phase of the circuit to advance and the phase of the received signal to advance by a certain angle, for example, 30''; The capacitance value of the capacitor 56 is set to such a value that when the off switch 60 is operated and the capacitor 56 is disconnected, the phase of the circuit is advanced and the phase of the received signal is advanced by a certain angle, for example, 60 degrees. The capacitance value of the capacitor 53 is set to a value that, when the switch 57 is operated and the capacitor 53 is connected, delays the phase of the circuit and delays the phase of the received signal by a certain angle, for example, 30''. The value is switch 5
8 and connects the capacitor 54, the phase of the circuit is delayed and the phase of the received signal is set at a certain angle, for example 60°.
It is set to a delay value.

When a position indicator equipped with such a tuned circuit is used as the coordinate input device, the phase difference between voltage and current in that circuit is calculated in the same manner as described above (however, the lagging phase is a value with a negative sign). ), the operating state of each switch 57-60 is detected and the state of the position indicator is identified.

(Effects of the Invention) As explained above, according to the present invention, since another capacitor is connected in parallel to the capacitor connected in series to the coil that transmits and receives radio waves through the off switch,
By operating the off switch and disconnecting the contact, the capacitance value in the circuit can be reduced, the resonant frequency thereof can be increased, and the phase of the signal in the circuit can be substantially advanced. The capacitance value of a capacitor is generally accurate and does not change much depending on the ambient temperature, so the leading phase angle can be set and maintained with high precision.Also, the loss of a capacitor is small, so it is not necessary to cut it. also, the attenuation constant in the tuned circuit does not change much, and therefore it is always positive i.
This has advantages such as being able to detect a leading phase angle and providing a position indicator with extremely good operability.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of a tuning circuit for a position indicator according to the present invention, FIG. 2 is a sectional view of a stylus pen equipped with the tuning circuit shown in FIG. 1, and FIG. A perspective view showing an outline of a coordinate input device using a stylus pen, FIG. 4 is a detailed configuration diagram of a timing control circuit, FIG. 5 is a signal waveform diagram of each part in FIG. 4, and FIG. 6 is a position of the present invention. FIG. 7 is a diagram showing a second embodiment of the tuning circuit of the indicator. 1... Coil with core, 2, 3... Capacitor, 4
... Off switch, 10 ... Stylus pen, 15
... Tuning circuit, 20 ... Tablet, 30 ... Position detection circuit, 40 ... Timing control circuit. :S 8 Figure 3 A standing servant appearance 2 each

Claims (2)

[Claims] (1) It has a coil and a capacitor connected in series to the coil, receives radio waves transmitted from the tablet side, generates radio waves based on the signals generated in the circuit, and sends them back to the tablet side. A tuned circuit for a position indicator, characterized in that it includes at least one phase shift circuit consisting of an off switch with a contact that disconnects when activated and another capacitor connected in series with the off switch. A tuning circuit for the position indicator. (2) It has a coil and a capacitor connected in series to the coil, and receives the radio waves sent from the tablet side. At this time, it generates radio waves based on the signals generated in the circuit, and sends them back to the tablet side. In a tuned circuit for a position indicator, the phase shift circuit includes an off switch with a contact that disconnects when activated, another capacitor connected in series with the off switch, and a contact that connects when activated. What is claimed is: 1. A tuning circuit for a position indicator, comprising at least one switch and a phase shift circuit consisting of a separate capacitor connected in series with the switch.