WO2010114165A1 - Proximity sensor and radio receiving apparatus - Google Patents

Abstract

A proximity sensor, which operates with low power and detects a subject to be detected at high accuracy, and/or a radio receiving apparatus is provided. The proximity sensor and/or the radio receiving apparatus is provided with a receiving antenna which receives radio waves, a resonant element connected to the receiving antenna, and an exciting means which excites the resonant element at a predetermined frequency.

Description

Proximity sensor and radio wave receiver

The present invention relates to a proximity sensor and a radio wave receiver that detect the position of an object.

Proximity sensors that have two antennas, generate an alternating electromagnetic field from one antenna, receive this by the other antenna, detect the phase of the received signal, and detect the position and movement of the object have been proposed. (For example, refer to Patent Documents 1 and 2).
FIG. 26 is a circuit diagram showing a configuration of a conventional proximity sensor 100 described in Patent Documents 1 and 2.
In the proximity sensor 100, the AC signal Ea is transmitted from the transmission antenna 103 based on the signal of the oscillator 102, and the AC signal Eb is taken into the circuit by the reception antenna 104. Next, the signal taken into the circuit by the receiving antenna 104 is directly amplified by the amplifier 108, and then detected by the signal of the oscillator 102 by the phase detector 109. Further, the output of the phase detector 109 is converted into a direct current by the LPF 110 and a change in the electromagnetic wave in the inspection region is output from the output terminal 111 as a change in the direct current voltage.
In addition, many methods have been proposed for receiving radio waves with high sensitivity in radio wave receivers that are equipped with an antenna, receive the antenna signal, and extract the signal from the received radio wave. ing.
In an environment where only weak radio waves can be obtained, it is necessary to increase the reception sensitivity of the radio wave receiver, but the most effective for this is a resonance with a magnitude comparable to the wavelength of the radio wave received by the antenna part of the radio wave receiver. This is a method using a mold antenna.
For this reason, in personal devices where the size of the radio wave receiving apparatus is limited, it is common to use an extremely short wavelength that requires only a small antenna.
However, a circuit using a short wavelength, that is, a high frequency requires a large power consumption. On the other hand, in a device with limited power, such as a radio timepiece, it is not allowed to have a gigahertz frequency circuit in which the antenna has a size of about a centimeter.
The frequency band currently used by the watch for radio wave correction is a very long wave band called VLF. For example, radio waves used in a radio timepiece are two waves of 40 kHz and 60 kHz in Japan. However, since the resonance type antenna of this frequency band requires a length of several kilometers, the resonance type antenna cannot be used. The reception sensitivity of the non-resonant antenna is extremely small compared to the resonant antenna.
For these reasons, there is a craving for a reception method with high reception sensitivity in low-power devices such as watches.
FIG. 27 is a diagram showing a radio wave receiver of a basic radio timepiece.
As shown in FIG. 27, the receiving circuit 110 amplifies the radio wave signal received by the antenna 113 by the amplifier circuit 115 with AGC, frequency-selects using the crystal filter 116 as a band-pass filter, and signals of the selected frequency It is known that the wave detector 117 is used to detect the wave (for example, Patent Document 3). The output of the detector 117 is smoothed by the smoothing circuit 118 and output from the output terminal 119.
Also known is a method in which the degree of freedom of frequency selection is increased by the superheterodyne method (for example, Patent Document 4).
JP 2006-275629 A (page 3-5, FIG. 1) JP 2007-171031 A (page 4-6, FIG. 1) JP 2002-267775 A (page 2-5, FIG. 1) Japanese Patent Laid-Open No. 6-214054 (page 2-6, FIG. 1)

However, in the proximity sensor 100, since the signal taken into the circuit by the receiving antenna 104 is very weak, sufficient gain cannot be obtained unless the frequency is high due to the nature of the antenna or the interaction between the object to be detected and the radio wave. . Therefore, in order to obtain sufficient detection sensitivity as a proximity sensor, the proximity sensor 100 needs to generate a signal having a very high frequency from the oscillator 102. For example, the proximity sensor described in Patent Document 1 assumes at least a high frequency of the HF band, and the proximity sensor disclosed in Patent Document 2 assumes the GHz band.
In order to generate a high-frequency signal, a large amount of energy must be input, and there is a problem in that a circuit configuration that consumes a large amount of power to handle the high-frequency signal must be used for the entire circuit.
Therefore, an object of the present invention is to provide a proximity sensor that can solve the above-described problems.
Another object of the present invention is to provide a proximity sensor that operates with low power and can detect an object to be detected with high accuracy.
Furthermore, conventional radio wave receivers use a low-sensitivity non-resonant antenna and do not use any special measures for radio wave reception or radio wave amplification methods. There was a problem that.
Therefore, an object of the present invention is to provide a radio wave receiving apparatus that can solve the above-described problems.
Another object of the present invention is to provide a radio wave receiver that can receive radio waves with high sensitivity while using a non-resonant antenna that operates with low power and has low sensitivity.
The proximity sensor of the present invention includes a receiving antenna that receives radio waves, a resonant element connected to the receiving antenna, and an excitation unit that excites the resonant element at a predetermined frequency.
Further, the proximity sensor of the present invention includes an AC signal generation source, a transmission antenna that transmits radio waves based on a signal of the AC signal generation source, a reception antenna that receives radio waves, a resonant element connected to the reception antenna, Phase detection means for detecting a phase of a signal received by a receiving antenna, which is a signal of an AC signal generation source, is provided.
In the proximity sensor of the present invention, in addition to the above-described configuration, the resonant element is preferably excited in advance based on the signal of the AC signal source.
Further, in the proximity sensor of the present invention, in addition to the above-described configuration, it is preferable that the resonant element is excited in advance by electrical coupling based on the signal of the AC signal source.
Furthermore, in the proximity sensor of the present invention, in addition to the above-described configuration, the resonant element is preferably excited in advance by mechanical coupling based on the signal of the AC signal source.
Furthermore, in the proximity sensor of the present invention, in addition to the above-described configuration, the resonant element preferably includes a vibrator.
Furthermore, in the proximity sensor of the present invention, in addition to the above-described configuration, it is preferable that the AC signal generation source is an oscillator having a vibrator, and the vibrator of the resonant element and the vibrator of the oscillator are integrally formed. .
Furthermore, in the proximity sensor of the present invention, in addition to the above-described configuration, the vibrator is preferably a crystal vibrator, a ceramic vibrator, or a MEMS vibrator.
Furthermore, in the proximity sensor of the present invention, in addition to the configuration described above, the resonant element is preferably configured to include an LC resonant circuit.
Furthermore, the proximity sensor of the present invention preferably includes a differential amplifying unit that differentially amplifies the output from both ends of the resonant element and outputs the signal received by the receiving antenna in addition to the above-described configuration.
Further, the proximity sensor according to the present invention includes, in addition to the above-described configuration, boosting means for boosting the power supply of the circuit of the AC signal generation source between the AC signal generation source and the transmission antenna, and a signal of the AC signal generation source. And amplifying means for amplifying with a power supply system boosted by the boosting means.
Further, in the proximity sensor of the present invention, in addition to the above-described configuration, it is preferable that one of the transmission antenna and the reception antenna is a rod-shaped antenna and the other is a ring-shaped antenna.
Furthermore, in the proximity sensor of the present invention, in addition to the above-described configuration, the ring-shaped antenna preferably has a shape in which a plurality of concentric rings are joined.
Furthermore, in the proximity sensor of the present invention, in addition to the above-described configuration, the ring-shaped antenna preferably has a coiled shape wound a plurality of times.
Furthermore, in the proximity sensor of the present invention, in addition to the configuration described above, it is preferable that the tip portion of the rod-shaped antenna has a coiled shape wound a plurality of times.
Furthermore, the proximity sensor of the present invention preferably includes a transparent substrate in addition to the above-described configuration, and the transmitting antenna and the receiving antenna are preferably formed of transparent electrodes on the transparent substrate.
Further, in the proximity sensor of the present invention, in addition to the above-described configuration, it is preferable that the transmitting antenna and the receiving antenna are formed in a concentric ring shape.
Furthermore, in the proximity sensor of the present invention, in addition to the above-described configuration, it is preferable that the transmission antenna and the reception antenna are formed in concentric circular arcs.
Further, in the proximity sensor of the present invention, in addition to the above-described configuration, the transparent substrate is rectangular, and the transmission antenna and the reception antenna are a quarter circle across two sides at the corner of the transparent electric substrate. It is preferably formed in an arc shape.
Further, in the proximity sensor of the present invention, in addition to the above-described configuration, the transparent substrate has a rectangular shape, and the transmitting antenna and the receiving antenna are formed in a half arc shape on the side of the transparent substrate. preferable.
Furthermore, in the proximity sensor of the present invention, it is preferable that at least one of the transmission antenna and the reception antenna is formed in a double or more pattern in addition to the above-described configuration.
The proximity sensor of the present invention includes a resonant element connected to a receiving antenna, excites the resonant element using a signal received by the receiving antenna, and performs phase detection using a signal stored in the resonant element. This makes it possible to increase the sensitivity, that is, to detect the distance information to the object to be detected with a high S / N, as compared with the conventional technique in which the phase detection is performed using the signal received by the antenna as it is.
In addition, the proximity sensor of the present invention can reduce the signal generated from the AC signal generation source to a low frequency. Therefore, the proximity sensor has a simple circuit configuration and low power compared to the prior art that needs to use a high-frequency signal. It becomes possible to operate.
The radio wave receiving apparatus of the present invention includes a PLL tuning circuit connected to an initial receiving antenna and a resonance circuit having a high Q connected to an antenna that is always used, and the resonance using the signal extracted by the PLL tuning circuit. Pre-excited circuit and receive with high sensitivity. Thereby, compared with the prior art which uses the signal received with the antenna as it is, a sensitivity can be increased and a weak radio wave can be received.
In addition, the radio wave receiver of the present invention can hold the signal stored in the resonance circuit for a short time. As long as pre-excitation is performed by maintaining the PLL circuit using the held reference signal, high-sensitivity reception can be maintained even if initial reception is impossible due to deterioration of the reception environment. it can. That is, once reception is successful, highly sensitive reception can be continued.

FIG. 1 is a circuit diagram showing the configuration of the proximity sensor of the present invention.
FIG. 2 is a diagram showing an example of a tuning fork type crystal resonator used in the proximity sensor 1a of FIG.
FIG. 3 is a diagram showing an example in which the first tuning-fork type crystal resonator 20 and the second tuning-fork type crystal resonator 30 shown in FIG. 2 are applied to the proximity sensor 1a shown in FIG.
FIG. 4 is a circuit diagram showing a configuration of another proximity sensor of the present invention.
FIG. 5 is a circuit diagram showing a configuration of still another proximity sensor of the present invention.
FIG. 6 is a diagram schematically illustrating the composite vibrator.
FIG. 7 is a plan view illustrating a configuration example of the composite vibrator.
FIG. 8 is a diagram showing an example in which the composite vibrating body 40a shown in FIG. 7 is applied to the proximity sensor 1c shown in FIG.
FIG. 9 is a circuit diagram showing a configuration of still another proximity sensor of the present invention.
FIG. 10 is a diagram illustrating a configuration example of a transmission antenna and a reception antenna.
FIG. 11 is a diagram illustrating another configuration example of the transmission antenna and the reception antenna.
FIG. 12 is a diagram illustrating still another configuration example of the transmission antenna and the reception antenna.
FIG. 13 is a diagram illustrating still another configuration example of the transmission antenna and the reception antenna.
FIG. 14 is a diagram illustrating still another configuration example of the transmission antenna and the reception antenna.
FIG. 15 is a diagram illustrating still another configuration example of the transmission antenna and the reception antenna.
FIG. 16 is a diagram illustrating a relationship with the output voltage of the approach distance sensor of the test object.
FIG. 17 is a diagram illustrating a configuration example of a transmission antenna and a reception antenna formed on a transparent substrate.
FIG. 18 is a diagram illustrating another configuration example of the transmission antenna and the reception antenna formed on the transparent substrate.
FIG. 19 is a diagram illustrating still another configuration example of the transmission antenna and the reception antenna formed on the transparent substrate.
FIG. 20 is a diagram illustrating still another configuration example of the transmission antenna and the reception antenna formed on the transparent substrate.
FIG. 21 is a diagram showing still another configuration example of the transmission antenna and the reception antenna formed on the transparent substrate.
FIG. 22 is a circuit diagram showing a configuration example of the receiving apparatus of the present invention.
FIG. 23 is a diagram illustrating a configuration example of a PLL tuning circuit.
FIG. 24 is a circuit diagram showing another configuration example of the receiving apparatus of the present invention.
FIG. 25 is a circuit diagram showing still another configuration example of the receiving apparatus of the present invention.
FIG. 26 is a diagram illustrating a configuration example of a conventional proximity sensor.
FIG. 27 is a diagram illustrating a conventional radio wave receiver.

Hereinafter, a proximity sensor and a radio wave receiver according to the present invention will be described with reference to the drawings. It should be noted that the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and equivalents thereof. Moreover, it is also possible to implement with the form which added the various change in the range which does not deviate from the meaning of this invention.
[Proximity sensor]
FIG. 1 is a circuit diagram showing a configuration of the proximity sensor 1a.
As shown in FIG. 1, the proximity sensor 1 a includes an oscillator 2 and a transmission antenna 3 that radiates an AC signal Ea to a region to be inspected based on a low-frequency signal generated by the oscillator 2.
The oscillator 2 is an example of an AC signal generation source, and is configured using, for example, a crystal resonator. The AC signal Ea radiated from the transmitting antenna 3 has high frequency stability because the stability of the frequency and intensity affects the output stability of the proximity sensor, and is stable with respect to temperature, changes with time, etc. It is preferable to use a simple crystal resonator.
As the crystal unit, a tuning fork type crystal unit that can oscillate in the VLF band, which is a low power consumption assumed to be used in a portable device or the like, is used. Further, even in the case of quartz, the oscillation impedance changes by 10% or more over a wide use temperature range such as −40 ° C. to 85 ° C. Therefore, it is preferable to provide an AGC circuit that stabilizes the oscillation amplitude.
Also, instead of the quartz crystal resonator, a piezoelectric element such as a PZT thin film and a ceramic (ceramic vibrator) made of ceramic, a MEMS vibrator made of a piezoelectric element such as a PZT thin film made of MEMS and formed on the surface of the vibrator, The oscillator 2 may be configured using a vibrator using lithium tantalate single crystal, lithium niobate single crystal, or langasite.
The proximity sensor 1a includes a receiving antenna 4 that receives an AC signal Eb from a region to be inspected, and a resonator 5 that is connected to the receiving antenna 4. The other end of the resonator 5 connected to the receiving antenna 4 is clamped to a reference voltage. The resonator 5 is excited by the AC signal Eb received by the receiving antenna 4.
The resonator 5 is preferably configured with as little energy loss as possible. For example, the resonator 5 is configured using a crystal resonator having a resonance frequency close to the frequency of the oscillator 2. Since the quartz crystal resonator has little energy loss during vibration, it can be stored in a long time interval without attenuating minute changes in electromagnetic waves.
Instead of the crystal resonator, similarly to the oscillator 2, a piezoelectric element such as a PZT thin film and a ceramic (ceramic vibrator) made of ceramic, and a piezoelectric element such as a PZT thin film are made of MEMS and formed on the surface of the vibrating body. The resonator 5 may be configured using a MEMS vibrator, a vibrator using lithium tantalate single crystal, lithium niobate single crystal, or langasite.
In addition, instead of the crystal resonator, a resonator in which an ultra-small vibrator is formed using a silicon process and electromechanical coupling is realized using a capacitor, an LC resonance circuit having a resonance frequency close to the frequency of the oscillator 2, The resonator 5 may be configured using a capacitive MEMS vibrator. In particular, the capacitive MEMS vibrator is excellent in terms of downsizing.
The proximity sensor 1 a includes a buffer 6 and a resistor 7 that connect the output of the oscillator 2 and one terminal of the resonator 5. With this configuration, the resonator 5 is excited in advance at the oscillation frequency of the oscillator 2 (hereinafter, such an operation is referred to as “pre-excitation”).
Here, the closer the oscillation frequency of the oscillator 2 and the resonance frequency of the resonator 5 are, the more efficiently the pre-excitation is performed. However, if the difference between the oscillation frequency of the oscillator 2 and the resonance frequency of the resonator 5 (hereinafter referred to as “detuning degree”) is very close or completely coincident, beat or resonance occurs, and after detection, This is not preferable because it affects the output. In order to output a rectified DC voltage, the degree of detuning needs to have at least a frequency higher than a cutoff frequency of a rectifying LPF 10 described later.
The buffer 6 is provided in order to avoid the influence from the subsequent circuit on the oscillator 2. The resistor 7 is a coupling resistance between the oscillator 2 and the resonator 5, and has a resistance value that appropriately couples the resonator 5 to the oscillator 2. If the value of the resistor 7 is too small, the electrical coupling becomes too strong, and the amplitude of the resonator 5 is determined by the output of the buffer 6 so that the signal from the receiving antenna 4 is not reflected. On the other hand, if the value of the resistor 7 is too large, the electrical coupling is too weak and the pre-excitation is not performed sufficiently and the effect of the resonator 5 is lost. For this reason, selection of the resistance value of the resistor 7 is important. When a crystal resonator having a resonance frequency of several tens of kHz is used as the resonator 5, the resistance value of the resistor 7 is appropriately about 0.5 to 1 MΩ.
The proximity sensor 1a smoothes the output of the phase detector 9 and the phase detector 9 that detect the phase of the signal received by the receiving antenna 4 with the amplifier 8 that amplifies the output of the resonator 5 and the output signal of the oscillator 2. An LPF (low-pass filter) 10 and an output terminal 11 are provided.
Next, the operation of the proximity sensor 1a will be described.
The proximity sensor 1 a generates a low-frequency signal by the oscillator 2 and radiates an AC signal Ea to the inspection area by the transmission antenna 3. The AC signal Ea radiated from the transmitting antenna 3 forms an electromagnetic field determined by the atmosphere, dielectric, conductor, etc. existing in this area in the area to be inspected. The receiving antenna 4 receives an AC signal Eb corresponding to an electromagnetic field formed in the inspection area.
At this time, if an object existing in the inspected area does not move at all, the electromagnetic field formed by the AC signal Ea transmitted by the transmitting antenna 3 is in a steady state, and the AC signal Eb received by the receiving antenna 4 has a stable phase. And with amplitude. However, when an inspected object O having an appropriate dielectric constant such as a human finger enters this region, the electromagnetic field changes due to disturbance. As a result, the phase and amplitude of the AC signal Eb received by the receiving antenna 4 change.
When the resonator 5 includes a crystal resonator, for example, the current due to the AC signal Eb captured from the receiving antenna 4 is extremely small, so that the stopped crystal resonator is excited to the specified frequency only by the current due to the AC signal Eb. Difficult to do. For this reason, the proximity sensor 1 a pre-excites the crystal resonator of the resonator 5 at the same frequency as the current taken from the receiving antenna 4.
In a state where the crystal resonator of the resonator 5 is pre-excited, the AC signal Eb received by the receiving antenna 4 is taken into the crystal resonator of the resonator 5 and accumulated in the crystal resonator. In the case of a crystal resonator having a Q value of tens of thousands, information stored in the crystal resonator is integrated into a size several tens of thousands of times.
The vibration of the resonator 5 storing the information from the receiving antenna 4 is electrically amplified by the amplifier 8. The output of the amplifier 8 is phase-detected at the frequency of the oscillator 2 by the phase detector 9, smoothed by the LPF 10, and output as a change in DC voltage from the output terminal 11.
As described above, when an object to be inspected O having an appropriate dielectric constant such as a human finger enters the area to be inspected, the electromagnetic field changes due to disturbance. As a result, the phase and amplitude of the AC signal Eb received by the receiving antenna 4 change, so that the output of the phase detector 9 changes, and the DC output from the smoother 10 that smoothes this changes. The presence and movement of the test object O can be known by the change in the DC output.
It should be noted here that the electromagnetic field in the region to be inspected formed by the transmission antenna 3 varies depending on the arrangement of objects in the region to be inspected, and the region to be inspected as viewed from the transmitting antenna 3 and the receiving antenna 4 If it is interpreted as a range in which electromagnetic waves are formed, in principle, it extends to infinity. Therefore, an area that can be sensed by the proximity sensor 1a without being buried in noise is defined as an inspected area. The output of the proximity sensor 1a in the environment where the transmitting antenna 3 and the receiving antenna 4 are installed is used as the background, and the change due to the disturbance of the electromagnetic wave caused by the inspected object O needs to be understood as the change from the background output.
The proximity sensor 1 a excites the resonator 5 using the AC signal Eb received by the receiving antenna 4, and performs phase detection using the signal stored in the resonator 5. As a result, the sensitivity is increased (that is, with a high S / N) and the distance information to the object to be detected O can be detected with high accuracy as compared with the conventional technique in which the phase detection is performed using the AC signal received by the antenna as it is. It becomes possible.
Further, since the proximity sensor 1a can set the signal generated from the oscillator 2 to a low frequency (for example, VLF band), it has a simple circuit configuration and low power as compared with the prior art that needs to use a high frequency signal. It becomes possible to operate.
Furthermore, in the case where the resonator 5 includes a crystal resonator, the proximity sensor 1a is pre-excited even if the AC signal Eb received by the receiving antenna 4 is weak because the crystal resonator is pre-excited. Thus, it becomes possible to detect the distance information to the test object O with high accuracy.
FIG. 2 is a diagram showing an example of a tuning fork type crystal resonator used in the proximity sensor 1a of FIG.
The first tuning-fork type crystal resonator 20 is used for the oscillator 2 and is connected to the first leg 21, the second leg 22, the first leg 21, and the second leg 22. 23 and so on. The second tuning-fork type crystal resonator 30 is used for the resonator 5 and is connected to the first leg 31, the second leg 32, the first leg 31, and the second leg 32. It is composed of a base 33 and the like.
The first tuning fork type crystal resonator 20 and the second tuning fork type crystal resonator 30 are both processed by a wet etching operation from a Z cut crystal of about 100 μm to 200 μm.
FIG. 3 is a diagram showing an example in which the first tuning-fork type crystal resonator 20 and the second tuning-fork type crystal resonator 30 shown in FIG. 2 are applied to the proximity sensor 1a shown in FIG.
In FIG. 3, the same components as those in FIG. In FIG. 3, the cross section of the first tuning fork type crystal resonator 20 shows the AA ′ cross section in FIG. 2, and the cross section of the second tuning fork type crystal resonator 30 shows the BB ′ in FIG. A cross section is shown.
Both sides of the first leg 21 of the first tuning fork type crystal resonator 20 perpendicular to the optical axis direction of the crystal and the second leg 22 of the first tuning fork type crystal resonator 20 perpendicular to the electric axis direction of the crystal. Electrodes J1 were formed on both side surfaces, and the electrodes J1 were connected to each other. Further, both sides of the first leg 21 of the first tuning-fork type crystal unit 20 perpendicular to the electric axis direction of the crystal and the optical axis direction of the crystal of the second leg 22 of the first tuning-fork type crystal unit 20 are used. Electrodes J2 were formed on both side surfaces perpendicular to the electrodes, and the electrodes J2 were connected to each other. When alternating current is applied between the electrodes J1 and J2 of the first tuning-fork type crystal resonator 20, the first leg 21 and the second leg 22 perform tuning-fork type bending vibration in the direction of arrow D in FIG. . The oscillator 2 outputs a signal having a frequency corresponding to the natural frequency of the bending vibration.
Furthermore, both sides of the first leg 31 of the second tuning-fork type crystal resonator 30 perpendicular to the optical axis direction of the crystal and the electric axis direction of the crystal of the second leg 32 of the second tuning-fork type crystal resonator 30. Electrodes J3 are formed on both side surfaces perpendicular to each other, and the electrodes J3 are connected to each other and connected to the receiving antenna 4. Further, both sides of the first leg 31 of the second tuning-fork type crystal resonator 30 perpendicular to the electric axis direction of the crystal and the optical axis direction of the crystal of the second leg 32 of the second tuning-fork type crystal resonator 30 are also shown. Electrodes J4 were formed on both side surfaces perpendicular to the electrodes, and the electrodes J4 were connected to each other. The electrode J4 is clamped to a reference voltage (for example, GND). By applying an alternating current between the electrodes J3 and J4 of the second tuning fork type crystal resonator 30, the first leg 31 and the second leg 32 perform tuning fork type bending vibration in the direction of arrow E in FIG. .
In the proximity sensor 1a, the signal from the oscillator 2 is applied between the electrodes J3 and J4 of the second tuning-fork type crystal resonator 30 via the coupling resistor 7, so that the second tuning-fork type crystal resonator 30 is The signal is pre-excited and maintained in a state where the signal received from the receiving antenna 4 can be accumulated. That is, in the example of FIG. 3, the second tuning-fork type crystal resonator 30 is configured to be electrically coupled to the oscillator 2 and pre-excited.
FIG. 4 is a circuit diagram showing a configuration of another proximity sensor 1b.
In FIG. 4, the same components as those of the proximity sensor 1a shown in FIG. The proximity sensor 1b shown in FIG. 4 is further connected to the amplifier 8 connected to the receiving antenna 4 side terminal of the resonator 5 and the other terminal of the resonator 5 with respect to the proximity sensor 1a shown in FIG. An inverting amplifier 12, an inductor 200 connected between the resonator 5 and GND, and a differential amplifier 13 that differentially amplifies the outputs of the amplifier 8 and the inverting amplifier 12 are provided. Here, the inductor 200 is preferably used when the frequency of the oscillator 2 and the resonator 5 are separated from each other, and a capacitor is preferably used when the frequency of the oscillator 2 and the resonator 5 is close.
When a signal having a frequency away from the resonance frequency is input to the resonator 5, a signal having a phase substantially inverted from the input signal is output from the other terminal. Accordingly, an approximately in-phase AC signal is output from the amplifier 8 and the inverting amplifier 12.
From the amplifier 8, the signal received by the receiving antenna 4 is superimposed on the signal corresponding to the pre-excitation and output. In contrast, the inverting amplifier 12 outputs a signal corresponding to pre-excitation that is not affected by the signal received by the receiving antenna 4. Therefore, the differential amplifier 13 that takes the difference between the outputs of the amplifier 8 and the inverting amplifier 12 does not include the amplitude due to the pre-excitation, and outputs only the signal received by the receiving antenna 4.
In general, if the voltage amplitude in the AC state before detection is set large, noise generated during detection due to phase noise between the reference signal for detection and the detected signal is suppressed to a low level. High detection is possible. In the proximity sensor 1a shown in FIG. 1, since a signal resulting from pre-excitation with a much larger amplitude than the detection signal is superimposed on the output of the amplifier 8, there is a problem that the pre-detection gain cannot be increased. is there.
On the other hand, in the proximity sensor 1b shown in FIG. 4, since the signal due to the pre-excitation is removed by the differential amplifier 13, the amplitude of the output signal from the differential amplifier 13 is input from the receiving antenna 4 and resonant. It is only the signal integrated by the device 5, and the amplitude is not raised by pre-excitation.
Therefore, the detection signal can be amplified in the subsequent stage without worrying about saturation of the amplitude of the pre-excitation, and in principle, the amplification factor before detection can be maximized. As a result, a proximity sensor having a higher S / N can be configured.
FIG. 4 shows an example in which the inverting amplifier 12 is used to generate a reference signal to be input to the differential amplifier 13. However, when the oscillation frequency of the oscillator 2 and the resonance frequency of the resonator 5 are close to each other (that is, when the degree of detuning is small), the phase difference between outputs from both ends of the resonator 5 depends on the nature of the resonator 5 and the like. It will not be 180 degrees. In this case, it is necessary to use a phase shifter instead of the inverting amplifier 12 so that the output of the amplifier 8 and the phase of the phase shifter are substantially matched.
The operation of detecting the distance of the test object O in the proximity sensor 1b is the same as that of the proximity sensor 1a described above. That is, the proximity sensor 1b, like the proximity sensor 1a, excites the resonator 5 using the AC signal Eb received by the receiving antenna 4, and performs phase detection using the signal stored in the resonator 5. The distance information to the test object O is detected with high accuracy. In addition, since the signal generated from the oscillator 2 can be set to a low frequency, it is possible to operate with a simple circuit configuration and low power.
FIG. 5 is a circuit diagram showing a configuration of still another proximity sensor 1b.
In FIG. 5, the same components as those of the proximity sensor 1a shown in FIG. The difference between the proximity sensor 1c and the proximity sensors 1a and 1b is that the resonator 5 is pre-excited mechanically. In FIG. 5, the mechanical coupling between the oscillator 2 and the resonator 5 is schematically replaced with a circuit 14.
In the following description, an example in which the oscillator 2 and the resonator 5 are integrally formed as a crystal resonator will be described as a configuration in which the resonator 2 is mechanically pre-excited by the oscillator 2.
FIG. 6 is an electrical symbol diagram schematically showing a composite vibrating body 40 in which the oscillator 2 and the resonator 5 are mechanically coupled and integrally formed as a crystal resonator. As shown in FIG. 6, in the composite vibrating body 40, a vibrator 41 constituting the oscillator 2 and a vibrator 42 constituting the resonator 5 are coupled by a mechanical coupling 43. The mechanical coupling 43 in FIG. 6 is a concept equivalent to the circuit 14 in FIG. A composite vibrator 40 shown in FIG. 6 is a four-terminal element, and electrodes J5 and J6 are formed on the vibrator 41, and electrodes J7 and J8 are formed on the vibrator.
FIG. 7 is a diagram illustrating an example of a specific example 40a of the composite vibrator.
The composite vibrating body 40a is processed by a wet etching operation from a Z-cut quartz plate having a thickness of about 100 μm to 200 μm, for example.
As shown in FIG. 7, the composite vibrating body 40a includes a first leg 41aL and a second leg 41aR, and a first leg 41aL and a second leg 41aR that are slightly different in shape such as width and cross-sectional shape. It has a central leg 42a located between them. The center leg 42a is designed with a width different from that of the first leg 41aL and the second leg 41aR. The first leg 41aL, the second leg 42aR, and the central leg 42a are joined to the base 44 at one end, and the composite vibrating body 40 is an alphabet E when viewed from the direction of the optical axis of the crystal, that is, the Z axis. It has a shape like
FIG. 8 is a diagram showing an example in which the composite vibrating body 40a shown in FIG. 7 is applied to the proximity sensor 1c shown in FIG.
In FIG. 8, the same components as those in FIG. As shown in FIG. 8, electrodes J5 are formed on both side surfaces perpendicular to the optical axis direction of the first leg 41aL and both side surfaces perpendicular to the electric axis direction of the second leg 41aR. Electrodes J6 are formed on both side surfaces perpendicular to the electric axis direction of the first leg 41aL and both side surfaces perpendicular to the optical axis direction of the second leg 41aR. Here, the first leg 41aL and the second leg 41aR constitute the vibrator 41 shown in FIG. Further, an electrode J7 is formed on both side surfaces perpendicular to the electric axis direction of the central leg 42a, and an electrode J8 is formed on both side surfaces perpendicular to the optical axis direction of the central leg 42a. Here, the central leg 42a constitutes the vibrator 42 shown in FIG.
The crystal resonator cut out by the Z cut expands and contracts in the mechanical axis direction when an electric field is applied in the electric axis direction, and generates an electric field in the electric axis direction when the leg is expanded and contracted in the mechanical axis direction. Therefore, when an alternating current is applied between the electrode J5 and the electrode J6, the composite vibrating body 40a causes the first leg 41aL and the second leg 41aR to perform tuning-fork type bending vibration as indicated by an arrow F in FIG. The natural frequency of this bending vibration is approximately determined by the width and length of the first leg 41aL and the second leg 41aR. Further, when the first leg 41aL and the second leg 41aR perform tuning-fork type bending vibration, an alternating current is generated between the electrode J5 and the electrode J6.
When the first leg 41aL and the second leg 41aR perform tuning fork-type bending vibration, the first leg 41aL and the second leg 41aR are slightly different in shape from each other, so that they do not balance, and the composite vibrator 40a is entirely Perform slight vibration. Due to the influence of the vibration of the entire composite vibrating body 40a, the central leg 42a slightly vibrates in a direction orthogonal to the extending direction of the legs in a plane including all the legs as shown by an arrow G in FIG. .
The slight vibration of the central leg 42a is the vibration caused by the mechanical coupling 14 or 23 described above. When the center leg 42a vibrates slightly, a weak current is generated between the electrode J7 and the electrode J8 at the oscillation frequency of the first leg 41aL and the second leg 41aR. This is pre-excitation. That is, in the composite vibrating body 40a, the first leg 41aL and the second leg 41aR on both sides constitute the vibrator 41, and this vibration excites another vibrating body 42 (center leg 42a) by weak mechanical coupling. . The width of the first leg 41aL and the second leg 41aR and the width of the central leg 42a are designed so that the degree of detuning, which is the difference between the natural frequencies, is several hundred Hz, for example.
In the above description, the first leg 41aL and the second leg 41aR are slightly different in shape, but the first leg 41aL and the second leg 41aR are designed to have the same length and thickness. However, since the working accuracy of the quartz tuning fork shape is limited, the shapes of the first leg 41aL and the second leg 41aR are slightly different from each other. For this reason, as described above, the vibrations of the first leg 41aL and the second leg 41aR are not balanced with each other, the entire composite vibrating body 40a vibrates, and the central leg 42a vibrates due to the influence of this vibration.
Note that when the composite vibrating body 40a is rotated in the optical axis direction while the vibrator 41 (the first leg 41aL and the second leg 41aR) is oscillating, excitation proportional to the rotational speed is caused by the Coriolis force. The output of the proximity sensor is erroneous because it is superimposed on the vibration of the (center leg 42a). In order to avoid this, the base 44 is constructed by reducing the distance between the legs (the first leg 41aL, the second leg 41aR, and the central leg 42a) so that the moment in the direction of rotation of the optical axis is reduced. It is preferable to fix firmly.
The operation of detecting the distance of the object O to be detected by the proximity sensor 1c is the same as that of the proximity sensor 1a described above. That is, similarly to the proximity sensor 1a, the proximity sensor 1c excites the resonator 5 using the AC signal Eb received by the receiving antenna 4, and performs phase detection using the signal stored in the resonator 5. Thus, it becomes possible to detect the distance information to the test object O with high accuracy. In addition, since the signal generated from the oscillator 2 can be set to a low frequency, it is possible to operate with a simple circuit configuration and low power.
Further, as described above, the proximity sensor 1c is configured to mechanically perform pre-excitation of the resonator 5, and the receiving antenna 4 and the oscillator 2 are not electrically coupled. Therefore, compared with the proximity sensors 1a and 1b in which the receiving antenna 4 and the oscillator 2 are electrically coupled, the AC signal Eb received by the receiving antenna 4 is not hindered by the output signal of the oscillator 2, It becomes possible to detect the distance information to the test object O with high sensitivity.
Further, in the proximity sensor 1c, the vibrator 41 constituting the oscillator 2 and the vibrator 42 constituting the resonator 5 are integrally configured as the composite vibrator 40, so that the apparatus can be further miniaturized. Become.
FIGS. 5 to 8 show examples in which the oscillator 2 and the resonator 5 are each configured using a crystal resonator, and the crystal resonators of the oscillator 2 and the resonator 5 are integrally formed as a composite vibrator 40. It was. However, the present invention is not limited to this, and the oscillator 2 and the resonator 5 are each configured to include a resonator other than a crystal resonator such as a ceramic resonator and a MEMS resonator, and the oscillator 2 and the resonator 5 are provided. These vibrators may be integrally formed as a composite vibrator.
FIG. 9 is a circuit diagram showing a configuration of still another proximity sensor of the present invention.
9, the same number is attached | subjected to the structure same as the proximity sensor 1c shown in FIG. 5, and the description is abbreviate | omitted. The difference between the proximity sensor 1 d and the proximity sensor 1 c is that an AC signal is generated between the oscillator 2 and the transmission antenna 3 by a booster circuit 50 that boosts the power supply of the circuit of the oscillator 2 and a power supply system boosted by the booster circuit 50. And an amplifier circuit 51 that amplifies the source signal. The booster circuit 50 is an example of a booster, and the amplifier circuit 51 is an example of an amplifier.
In the proximity sensor 1d, the signal output from the oscillator 2 is voltage-amplified by the booster circuit 50 and the amplifier circuit 51, and a strong electromagnetic wave alternating current is transmitted by the transmitting antenna 3 based on the signal amplified in comparison with the power supply voltage used by this apparatus. A signal Ea is emitted to the region to be inspected. Therefore, in the proximity sensor 1d, even if the power supply voltage used is a low power supply voltage such as 3 V and 5 V, for example, the distance of the object O to be detected can be detected in a wider inspection area compared to the proximity sensor 1 c. It becomes possible.
In the proximity sensor 1d shown in FIG. 9, the booster circuit 50 is provided in the configuration of the proximity sensor 1c. However, the booster circuit 50 may be provided between the oscillator 2 and the transmission antenna 3 in the configuration of the proximity sensor 1a or the proximity sensor 1b.
[Transmitting and receiving antennas]
Hereinafter, a transmission antenna and a reception antenna that can be used in the proximity sensor of the present invention will be described.
FIG. 10 is a diagram showing an example using a planar antenna, and FIG. 11 is a diagram showing an example using a rod-shaped antenna.
In the proximity sensor, some arrangement is required for the arrangement of the transmission antenna 3 and the reception antenna 4. Considering the efficiency of the antenna, it is preferable to arrange the planar transmission antenna 3a and reception antenna 4a as shown in FIG. 10 or the rod-like transmission antenna 3b and reception antenna 4b as shown in FIG. 11 in parallel. The configuration in which the antennas are arranged as shown in FIG. 10 or FIG. 11 and the approach of the object to be detected approaches the space region between the antennas has the largest change in the way of propagation of electromagnetic waves, and the sensitivity as a sensor is large. . Note that shields 15 and 16 are preferably provided in the wiring portion in order to suppress the influence on the reception and transmission of signals in the wiring portion.
However, in the antenna configurations shown in FIGS. 10 and 11, even if the distance between the test object and the antenna is the same, if the movement direction of the test object with respect to the antenna is different, the output of the proximity sensor will be different. End up. Therefore, an antenna configuration in which the output of the proximity sensor does not depend on the moving direction of the test object with respect to the antenna but depends on the distance between the antenna and the test object will be described below.
FIG. 12 is an explanatory diagram illustrating still another configuration example of the transmission antenna and the reception antenna.
The antenna configuration example shown in FIG. 12 is a ring-shaped reception antenna 3c and a ring-shaped reception antenna disposed at an equal distance from the rod-shaped transmission antenna 3c in a plane perpendicular to the direction in which the rod-shaped transmission antenna 3c extends. And an antenna 4c. The rod-shaped transmitting antenna 3c is provided with a shield 15 at a portion excluding a minute portion at the tip, and the ring-shaped receiving antenna 4c is provided with a shield 16 at a portion excluding a ring portion.
In the configuration example of the antenna shown in FIG. 12, the electromagnetic wave transmitted from the transmission antenna 3c is symmetric about the rod-shaped portion of the transmission antenna 3c. Furthermore, in the antenna configuration example shown in FIG. 12, when the ring diameter of the receiving antenna 4c is reduced, the electromagnetic field formed on the receiving antenna 4c from the transmitting antenna 3c is considered to be centrally symmetric from a position separated by a predetermined distance. be able to. Therefore, in the configuration example of the antenna shown in FIG. 12, the output of the proximity sensor does not depend on the moving direction of the test object with respect to the antenna but can depend on the distance between the antenna and the test object.
FIG. 13 to FIG. 15 are explanatory diagrams showing still other configuration examples of the transmission antenna and the reception antenna.
The antenna configuration example shown in FIG. 13 includes a receiving antenna 4d in which a plurality of concentric rings are joined. The antenna configuration example shown in FIG. 14 includes a coil-shaped receiving antenna 4e wound a plurality of times. The reception sensitivity of the antenna can be improved by using the configuration of the reception antenna as shown in FIGS. The reception sensitivity of the antenna increases with the number of rings.
The antenna having the configuration shown in FIG. 15 is the same as the antenna shown in FIG. 14 except that the transmission antenna is a transmission antenna 3d having a coiled tip that is wound a plurality of times. With this configuration, it is possible to increase the area functioning as a transmission antenna and improve the output of the transmission antenna. 12 and 13, the transmission antenna 3d shown in FIG. 15 may be used instead of the transmission antenna 3c.
FIG. 16 is a diagram showing the relationship between the test object and the output voltage in the proximity sensor 1c having the antenna shown in FIG.
In FIG. 16, the horizontal axis (X axis) indicates the distance from the center of the antenna to the object to be detected, and the vertical axis (Y axis) indicates the output voltage of the sensor. A solid line 60 shown in FIG. 16 indicates the output of the sensor, and a broken line 61 indicates a line approximated by Y = 3000 / X-50. When an experiment for detecting the output voltage shown in FIG. 16 is performed, a human finger is used as the test object.
The output of the proximity sensor used in this experiment is a direct current. In FIG. 16, the output voltage is shown as a difference value from the output value when the test object is sufficiently away from the proximity sensor. The output of the proximity sensor used in this experiment has a noise of about 2 mVrms. As shown in FIG. 16, the output is buried in the noise at a distance exceeding 5 cm, and measurement becomes impossible.
Further, as shown in FIG. 16, it can be confirmed that the output of the proximity sensor used in this experiment is almost inversely proportional to the distance from the center of the antenna of the test object. Thus, the fact that the output is inversely proportional to the distance of the object to be tested confirms that the distance detection operation by the proximity sensor is caused by electromagnetic waves rather than electrostatic fields.
It was also confirmed that the proximity sensor used in this experiment was able to detect an object to be detected within a distance of about 5 cm with sufficient S / N when the output of the oscillator 2 was a voltage amplitude of 5V. When the proximity sensor according to the present invention sets the output of the oscillator 2 to a voltage amplitude of 100 V, it is possible to detect a test object within a distance of about 1 m with sufficient S / N.
Although FIGS. 12 to 15 show examples in which the rod-shaped transmission antenna 3 and the ring-shaped reception antenna 4 are provided, the transmission antenna 3 may be ring-shaped and the reception antenna 4 may be rod-shaped. Note that the transmission antenna 3 and the reception antenna 4 described with reference to FIGS. 10 to 15 have antenna configurations optimized for sensitivity when there is not much restriction on the installation environment.
[Transmitting and receiving antennas formed on a transparent substrate]
Hereinafter, a transmission antenna and a reception antenna formed on a transparent substrate that can be used in the proximity sensor of the present invention will be described.
Recently, there is an increasing need for an input device linked with video information drawn on a display, that is, an input device called a touch panel. If the transmitting antenna and the receiving antenna of the proximity sensor of the present invention are arranged on the display, the position of the test object located in the three-dimensional region on the display is detected, and according to the three-dimensional position information of the test object. An input device can be configured by controlling input to the device.
Below, in order to comprise such an input device, the transmission antenna 3 and the reception antenna 4 which were formed using transparent electrodes, such as ITO, on a transparent substrate are demonstrated.
FIG. 17 is a diagram illustrating a configuration example of a transmission antenna and a reception antenna formed using a transparent electrode on a transparent substrate.
The antenna configuration shown in FIG. 17 includes a transmitting antenna 3f and a receiving antenna 4f formed in a ring shape by transparent wiring using a transparent electrode such as ITO on a transparent substrate 70 such as glass or resin. The pattern of the receiving antenna 4f is formed concentrically around the pattern of the transmitting antenna 3f. Thus, by forming the transmitting antenna and the receiving antenna in a concentric ring shape, the antenna and the test object are independent of the moving direction of the test object with respect to the antenna, similarly to the antenna configurations shown in FIGS. The output of the proximity sensor depending on the distance can be obtained.
In addition, it is necessary to perform wiring for connecting the transmitting antenna 3f and the receiving antenna 4f to a circuit unit (not shown) that constitutes the proximity sensor, but in order to suppress the influence on the reception and transmission of the signal of the wiring unit, , Shields 15 and 16 are provided.
Although FIG. 17 shows an example in which the transmission antenna and the reception antenna are formed with a single ring-shaped pattern, one or both of the transmission antenna and the reception antenna may be formed with a double or more ring-shaped pattern. good. The reception sensitivity of the antenna can be improved by increasing the number of rings of each antenna.
Usually, the display area is rectangular. When an object located in the three-dimensional space on the rectangular area is detected by, for example, four proximity sensors, it is reasonable to arrange the antennas of the proximity sensors at the corners of the rectangular area.
Here, as described above, since the output of the proximity sensor of the present invention is inversely proportional to the distance between the object to be measured and the center of the antenna, the output of the sensor becomes too large near the center of the ring of the antenna. Further, the vicinity of the center of the ring of the antenna is also a singular region where the situation where the sensitivity is inversely proportional to the distance is distorted. Therefore, the vicinity of the center of the ring is not suitable for detection.
However, when the antenna having the configuration shown in FIG. 17 is arranged at the corner of the rectangular region, the vicinity of the center of the ring of the antenna is located inside from the corner. Further, when the antenna is formed with a large ring in order to increase sensitivity, the vicinity of the center of the ring of the antenna is positioned further inside. That is, even if the antenna having the configuration shown in FIG. 17 is arranged at the corner of the rectangular area, the vicinity of the center of the ring, which is not suitable for detection, is located on the inner side from the corner of the rectangular area. There is a problem that an object located in space cannot be detected correctly.
FIG. 18 is a diagram illustrating another configuration example of a transmission antenna and a reception antenna formed using a transparent electrode on a transparent substrate.
The configuration example of the antenna shown in FIG. 18 is a configuration for solving the above problem. In the configuration of the antenna shown in FIG. 18, a 1/4 arc-shaped transmitting antenna 3 g 1 and receiving antenna 4 g 1 are connected to the transparent substrate 70 by transparent wiring using transparent electrodes such as ITO at the corners of the transparent substrate 70. It is formed across two sides. The pattern of the receiving antenna 4g1 is formed in a concentric circular arc shape surrounding the pattern of the transmitting antenna 3g1.
Wiring for connecting the transmission antenna 3g1 and the reception antenna 4g1 to a circuit unit (not shown) constituting the proximity sensor is performed via the connection terminals 71 and 72, respectively. In order to suppress the influence on the reception and transmission of signals of the wiring part, shields 15 and 16 are provided in the wiring part.
Similarly, the transmission antennas 3g2-3g4 and the reception antennas 4g2-4g4 are formed in the other corners of the transparent substrate 70 in a quarter arc pattern. The pattern of the receiving antennas 4g2-4g4 is formed in a concentric circular arc shape surrounding the pattern of the transmitting antennas 3g2-3g4. Here, the transmitting antenna 3g2 and the receiving antenna 4g2, the transmitting antenna 3g3 and the receiving antenna 4g3, and the transmitting antenna 3g4 and the receiving antenna 4g4 are respectively connected to circuit units constituting separate proximity sensors. In FIG. 18, only the wiring from the transmitting antenna 3g1 and the receiving antenna 4g1 is shown.
In the configuration example shown in FIG. 18, by forming the transmitting antenna and the receiving antenna in a quarter arc shape, the vicinity of the center of the ring unsuitable for detection can be positioned at the corner of the rectangular area. This makes it possible to correctly detect an object located in the three-dimensional space on the display area.
In the configuration example shown in FIG. 18, the transmitting antenna and the receiving antenna are formed in concentric circular arcs, so that the inner side of the rectangular area does not depend on the moving direction of the object to be examined with respect to the antenna, The output of the proximity sensor depending on the distance of the test object can be obtained.
FIG. 19 is a diagram illustrating still another configuration example of a transmission antenna and a reception antenna formed using a transparent electrode on a transparent substrate.
In the configuration example of the antenna shown in FIG. 19, arc-shaped transmission antennas 3h1-3h4 and reception antennas 4h1-4h4 are formed on a transparent substrate 70 by transparent wiring using a transparent electrode such as ITO. The pattern of the reception antennas 4h1-4h4 surrounds the pattern of the transmission antennas 3h1-3h4, and is formed in a concentric circular arc shape across two sides at the corner of the transparent substrate 70.
The transmission antenna 3h1 and the reception antenna 4h1, the transmission antenna 3h2 and the reception antenna 4h2, the transmission antenna 3h3 and the reception antenna 4h3, and the transmission antenna 3h4 and the reception antenna 4h4 are respectively connected to circuit units constituting separate proximity sensors. In FIG. 19, only the wiring from the transmitting antenna 3h1 and the receiving antenna 4h1 is shown.
In FIG. 19, the boundary of the display portion of the display is indicated by H. The boundary H of the display unit is located inward from the end of the transparent substrate 70 by a predetermined length. Further, the center C1-C4 of the arcs of the transmitting antennas 3h1-3h4 and the receiving antennas 4h1-4h4 are respectively located at the corners of the display unit. The transmitting antennas 3h1-3h4 and the receiving antennas 4h1-4h4 are arcs larger than ¼, and are formed beyond the boundary B of the display unit to the end of the transparent substrate 70.
Accordingly, in the antenna having the configuration shown in FIG. 19, the distortion of the sensitivity with respect to the area of the display unit is suppressed and the position of the test object can be accurately determined as compared with the antenna formed by the quarter arc shown in FIG. It becomes possible to detect.
FIG. 20 is a diagram illustrating still another configuration example of a transmission antenna and a reception antenna formed using a transparent electrode on a transparent substrate.
In the configuration example of the antenna shown in FIG. 20, the transmitting antenna 3 i 1-3 i 4 and the receiving antenna 4 i 1-4 i 4 are each doubled 1/4 by transparent wiring using a transparent electrode such as ITO on the transparent substrate 70. The arc-shaped pattern is formed. The pattern of the receiving antennas 4g1-4g4 surrounds the pattern of the transmitting antennas 3g1-3g4, and is formed in a concentric circular arc shape at the corner of the boundary B of the display unit.
The transmitting antenna 3i1 and the receiving antenna 4i1, the transmitting antenna 3i2 and the receiving antenna 4i2, the transmitting antenna 3i3 and the receiving antenna 4i3, and the transmitting antenna 3i4 and the receiving antenna 4i4 are respectively connected to circuit units constituting separate proximity sensors. In FIG. 20, only the wiring from the transmitting antenna 3i1 and the receiving antenna 4i1 is shown.
In the antenna having the configuration shown in FIG. 20, the transmission antennas 3i1-3i4 and the reception antennas 4i1-4i4 are each formed in a double 1/4 arc-shaped pattern, so that the reception sensitivity of the antenna can be improved. It becomes. The reception sensitivity of the antenna can be improved by increasing the number of arc-shaped pattern rings of each antenna.
Although FIG. 20 shows an example in which both the transmitting antenna and the receiving antenna are formed with a double arc pattern, only one of the antennas may be formed with a double arc pattern. Further, one or both of the transmission antenna and the reception antenna may be formed in a triple or more arc pattern.
FIG. 21 is a diagram showing still another configuration example of a transmission antenna and a reception antenna formed using a transparent electrode on a transparent substrate.
In the configuration example of the antenna shown in FIG. 21, similarly to FIG. 20, the transmission antenna 3j1-3j4 and the reception antenna 4j1-4j4 are formed by transparent wiring using transparent electrodes such as ITO at the corners of the transparent substrate 70. Each is formed with a double quarter arc pattern.
The transmitting antenna 3j1 and the receiving antenna 4j1, the transmitting antenna 3j2 and the receiving antenna 4j2, the transmitting antenna 3j3 and the receiving antenna 4j3, and the transmitting antenna 3j4 and the receiving antenna 4j4 are respectively connected to circuit units constituting separate proximity sensors. In FIG. 21, only the wiring from the transmitting antenna 3j1 and the receiving antenna 4j1 is shown.
The antenna configuration shown in FIG. 21 further includes a transmission antenna 3j5-3j6 and a reception antenna 4j5-4j6 formed in a double half arc pattern on the side of the transparent substrate 70. The pattern of the receiving antennas 4j5-4j6 surrounds the pattern of the transmitting antennas 3j5-3j6 and is formed in a concentric circular arc shape at the corner of the boundary H of the display unit. The transmission antenna 3j5 and the reception antenna 4j5, and the transmission antenna 3j6 and the reception antenna 4j6 are respectively connected to circuit units constituting separate proximity sensors.
With the configuration as shown in FIG. 21, it is possible to detect an object in a wider inspection area as compared with the configurations of FIGS. 18 to 20 in which the antenna is arranged only at the corner of the transparent substrate. Become.
Although FIG. 21 shows an example in which both the transmission antenna and the reception antenna are formed with a double arc pattern, one or both antennas may be formed with one arc pattern.
Although FIGS. 17 to 21 show an example in which the reception antenna 4 is formed surrounding the transmission antenna 3, the transmission antenna 3 may be formed surrounding the reception antenna 4.
In the proximity sensors 1a to 1d described above, a transmission antenna and a reception antenna formed of a transparent electrode on a transparent substrate as shown in FIGS. 17 to 21 can be used. By disposing a transmitting antenna and a receiving antenna formed of transparent electrodes on a transparent substrate on a display, the position of a test object located in a three-dimensional region on the display is detected, and the three-dimensional of the test object is detected. An input device that controls input to the device according to the position information can be configured.
[Radio wave receiver]
Hereinafter, a radio wave receiving apparatus to which a configuration that can detect a weak received radio wave used in the proximity sensor described above with high accuracy using a resonator will be described. In other words, the reception antenna, the resonator that accumulates the weak signal received from the reception antenna, and the means for pre-exciting the resonator are used in the radio wave receiver.
FIG. 22 is a circuit diagram showing a configuration example of the radio wave receiver 80a of the present invention, and FIG. 23 is a diagram showing an example of a PLL tuning circuit 82 provided in the radio wave receiver.
As shown in FIG. 22, the radio wave receiver 80 a includes a first receiving antenna 83 and a PLL tuning circuit 82 that tunes to the initial radio wave Ea received by the first receiving antenna 83.
The PLL tuning circuit is an example of a filter, and is configured using, for example, a crystal resonator as a reference oscillator. As shown in FIG. 23, the PLL tuning circuit 82 includes a Colpitts oscillator 94 whose frequency is variable using a crystal resonator 96, a varicap 95, and the like whose oscillation frequency is different from the radio wave Ea by several hundred PPM. I have. In the PLL tuning circuit 82, the phase shift amount between the radio wave Ea received from the first receiving antenna 83 and the transmission is extracted by the phase comparator 93, smoothed by the smoothing circuit 97, and the smoothed voltage is controlled by the control voltage. As a result, oscillation is performed at exactly the same frequency and phase as the received radio wave Ea.
Further, as shown in FIG. 22, the radio wave receiver 80a has a second receiving antenna 84 in the sense of being distinguished from the first receiving antenna 3 for operating the initial PLL tuning circuit 82. The second receiving antenna 84 is connected to one end of the resonator 85, and the other end of the resonator 85 is clamped to a reference voltage. The resonator 85 is excited by the radio wave Eb received by the second receiving antenna 84.
The resonator 85 is configured by using a crystal element having as little energy loss as possible, for example, a crystal resonator having a resonance frequency close to the frequency of the PLL tuning circuit 82. Since the quartz crystal resonator has little energy loss during vibration, it can be stored in a long time interval without attenuating minute changes in electromagnetic waves.
The resonator 85 includes a piezoelectric element such as a PZT thin film and a ceramic (ceramic vibrator) made of ceramic, a MEMS vibrator formed on the surface of a vibrating body made of a piezoelectric element such as a PZT thin film, and tantalum acid. It can also be constituted by a vibrator using lithium single crystal, lithium niobate single crystal, or langasite.
Furthermore, the resonator 85 includes an ultra-small vibrator configured using a silicon process, a vibrator that realizes electromechanical coupling using a capacitor, an LC resonance circuit having a resonance frequency close to the frequency of the PLL tuning circuit 82, Alternatively, it can be constituted by a capacitive MEMS vibrator or the like. The capacitive MEMS vibrator is particularly excellent in terms of miniaturization.
As shown in FIG. 22, the radio wave receiver 80 a includes a buffer 86 and a coupling resistor 87 that connect the output of the PLL tuning circuit 82 and one terminal of the resonator 85. With this configuration, the resonator 85 is excited in advance at the oscillation frequency of the PLL tuning circuit 82 (hereinafter, this vibration is referred to as “pre-excitation”).
Here, the closer the oscillation frequency of the PLL tuning circuit 82 and the resonance frequency of the resonator 85 are, the more efficiently the pre-excitation is performed. The difference between the oscillation frequency of the PLL tuning circuit 82 and the resonance frequency of the resonator 85 is referred to as “detuning degree”. However, if the degree of detuning is very close or exactly the same, beat or resonance occurs, which affects the output after detection, which is not desirable. In order to rectify and output a DC voltage, it is necessary to keep the degree of detuning higher than at least a cutoff frequency of a rectifying LPF (low-pass filter) 90 described later.
The buffer 88 is provided in order to prevent the PLL tuning circuit 82 from being affected by the subsequent circuit. The resistor 87 is a coupling resistance between the PLL tuning circuit 82 and the resonator 85, and a resistor having a resistance value that appropriately couples the resonator 85 to the output of the PLL tuning circuit 82 is used. If the value of the resistor 87 is too small, the electrical coupling becomes too strong, and the amplitude of the resonator 85 is determined by the output of the buffer 86, and the signal from the second receiving antenna 84 is not reflected. On the other hand, if the value of the resistor 87 is too large, the electrical coupling is too weak and the pre-excitation is not performed sufficiently and the effect of the resonator 85 is lost. For this reason, selection of the resistance value of the resistor 87 is important. In this case, a quartz resonator having a resonance frequency of several tens of kHz is used as the resonator 85, and the resistance value of the resistor 87 is suitably about 0.5 to 1 MΩ.
Furthermore, the radio wave receiver 80a includes an amplifier 88 that amplifies the output of the resonator 85, and a phase detector 89 that detects the phase of the signal received by the second receiving antenna 84 as an output signal of the PLL tuning circuit 82. Furthermore, the radio wave receiver 80 a includes an LPF 90 that smoothes the output of the phase detector 89 and an output terminal 91.
Further, the output boosted by the resonator 85 is mixed by the mixer 92 to the first antenna (initial antenna) 83 to reinforce the reference signal of the PLL tuning circuit 82.
By the way, the radio wave receiver 80a can be configured by using two tuning fork type crystal resonators as shown in FIG. 2, similarly to the proximity sensor 1a shown in FIG. That is, the first tuning fork type crystal resonator is used as the crystal resonator 96 used in the PLL tuning circuit 82, and the second tuning fork type crystal resonator is used as the crystal resonator used in the resonator 85. it can. With such a configuration, the second tuning-fork type crystal resonator used for the resonator 85 is electrically coupled to the PLL tuning circuit 82 via the coupling resistor 87 and pre-excited.
Next, the operation of the radio wave receiver 80a will be described.
First, when the radio wave is strong and the reception environment is excellent, the radio wave Ea is captured from the first reception antenna 83, and the radio wave Ea from the first reception antenna 83 is initially extracted by the PLL tuning circuit 82. Pool. In other words, the PLL tuning circuit 82 oscillates at a frequency tuned to the frequency of the radio wave Ea received from the antenna 83, and generates oscillation in the circuit at the same frequency as the tuned frequency. Thereafter, the second reception antenna 84 receives the radio wave Eb under all conditions with different reception environments.
When the resonator 85 is configured to include, for example, a crystal resonator, the AC signal current generated by the radio wave Eb received by the first receiving antenna 84 is extremely small. Therefore, the stopped crystal resonator is specified only by the AC signal current. It is difficult to excite at the selected frequency. Therefore, in the radio wave receiving device 80a, the crystal resonator of the resonator 85 is pre-excited at the same frequency as the AC signal current taken from the second receiving antenna 84.
Here, the resonance frequency of the vibrator used in the PLL tuning circuit 82 described above needs to substantially match (very close to) the frequency of the received radio wave Ea, but in the case of the vibrator used in the resonator 85, The resonance frequency needs to be slightly away (with an appropriate degree of detuning) from the frequency of the received radio wave Ea. If the resonance frequency of the vibrator used in the resonator 85 and the frequency of the received radio wave Ea are close or completely coincident with each other, beat or resonance occurs, which affects the output after detection, which is not desirable.
In a state where the crystal resonator of the resonator 85 is pre-excited, the AC signal current generated by the radio wave Eb received by the second receiving antenna 84 is taken into the crystal resonator of the resonator 85 and accumulated in the crystal resonator. In the case of a crystal resonator having a Q value of tens of thousands, information stored in the crystal resonator is integrated into a size several tens of thousands of times.
The vibration of the resonator 85 that accumulates information from the second receiving antenna 84 is electrically amplified by the amplifier 88. The output of the amplifier 88 is phase-detected at the frequency of the PLL tuning circuit 82 by the phase detector 89, smoothed by the LPF 90, and output as a change in DC voltage from the output terminal 91.
The radio wave receiver 80a excites the resonator 85 using the AC signal current generated by the radio wave Eb received by the second receiving antenna 84, and performs phase detection using the signal stored in the resonator 85. This makes it possible to increase sensitivity, that is, to receive radio waves with a high S / N, as compared with the conventional technique in which phase detection is performed using the AC signal Ea received by the first receiving antenna 83 as it is.
Further, the radio wave receiver 80a can be operated with a simple circuit configuration and low power.
Further, the radio wave receiver 80a is configured to include a resonator 85, for example, a crystal resonator, and the radio wave Eb received by the second receiving antenna 84 is weak because the crystal resonator is pre-excited. It is also possible to receive radio waves.
FIG. 24 is a circuit diagram showing a configuration of another radio wave receiver 80b.
24, the same components as those of the radio wave receiver 80a shown in FIG. 22 are denoted by the same reference numerals, and the description thereof is omitted. The radio wave receiving device 80 b has an oscillator 182 including a crystal resonator 96 instead of the PLL tuning circuit 82, the first receiving antenna 83, and the mixer 92. If the resonance frequency of the vibrator used in the resonator 85 is very close to the frequency of the received radio wave, a PLL tuning circuit is not necessarily required. Therefore, a similar vibrator is used instead of the PLL tuning circuit 82 and the like. The usual oscillator 182 that has been used can be used.
FIG. 25 is a circuit diagram showing a configuration of still another radio wave receiver 80c.
In FIG. 25, the same components as those of the radio wave receiver 80a shown in FIG. The difference between the radio wave receiver 80a and the radio wave receiver 80c is that the resonator 85 is mechanically pre-excited. In FIG. 25, the mechanical coupling between the PLL tuning circuit 82 and the resonator 85 is schematically replaced with a circuit 98. The operation of the radio wave receiving device 80c is the same as that of the above-described radio wave receiving device 80a, and thus the description thereof is omitted.
Similarly to the proximity sensor 1c shown in FIG. 8, the radio wave receiver 80c is configured by using a single crystal resonator having a first leg, a second leg, and a central leg as shown in FIG. ing. That is, the first leg and the second leg can be used as the crystal oscillator 96 used for the PLL tuning circuit 82, and the center leg can be used as the crystal oscillator used for the resonator 85. With such a configuration, the central leg is pre-excited by mechanical coupling by the vibration of the first leg and the second leg. In other words, the circuit 98 schematically shown in FIG. 25 illustrates the mechanical coupling of the first and second legs and the central leg.
The radio wave receiver 80c shown in FIG. 25 can be operated with a simple circuit configuration and low power, similarly to the radio wave receiver 80a, and the radio wave Eb received by the second receiving antenna 84 is weak. It is also possible to receive radio waves.
By the way, the radio timepiece cannot use a receiving circuit having a complicated and large configuration in nature. Also, in a receiving circuit used for a radio timepiece, it is necessary to keep power consumption extremely low. Therefore, the radio wave receivers 80a, 80b, and 80c are suitable for use in a receiving circuit that receives a standard radio wave including time information of a radio clock. In that case, the signal output from the output terminal 91 of the radio wave receivers 80a, 80b, and 80c is a signal 99 in which time information is superimposed in a certain format, as shown in FIGS.

Claims (20)

1. A receiving antenna for receiving radio waves,
   A resonant element connected to the receiving antenna;
   Excitation means for exciting the resonant element at a predetermined frequency;
   Proximity sensor characterized by having.
2. An AC signal source;
   A transmission antenna that transmits radio waves based on a signal from the AC signal generation source;
   The proximity sensor according to claim 1, further comprising phase detection means for detecting a phase of a signal received by the reception antenna.
3. The proximity sensor according to claim 2, wherein the excitation means is a signal of the AC signal source.
4. The proximity sensor according to claim 2, wherein the excitation means is a vibrator included in the AC signal source.
5. The proximity sensor according to claim 1, wherein the resonance element includes a vibrator.
6. The AC signal generation source is an oscillator having a vibrator,
   The proximity sensor according to claim 5, wherein the resonator of the resonance element and the resonator of the oscillator are integrally formed.
7. The proximity sensor according to claim 5, wherein the vibrator is a crystal vibrator, a ceramic vibrator, or a MEMS vibrator.
8. The proximity sensor according to claim 1, wherein the resonant element includes an LC resonant circuit.
9. The proximity sensor according to claim 1, further comprising differential amplifying means for differentially amplifying outputs from both ends of the resonant element and outputting the signals received by the receiving antenna.
10. Between the AC signal generation source and the transmitting antenna, a boosting unit that boosts the power supply of the circuit of the AC signal generation source, and an amplification that amplifies the signal of the AC signal generation source by a power supply system boosted by the boosting unit The proximity sensor according to claim 1, further comprising means.
11. The proximity sensor according to claim 1, wherein one of the transmission antenna and the reception antenna is a rod-shaped antenna and the other is a ring-shaped antenna.
12. The proximity sensor according to claim 11, wherein the ring-shaped antenna has a shape in which a plurality of concentric rings are joined or a coil shape that is wound a plurality of times.
13. The proximity sensor according to claim 11, wherein a tip end portion of the rod-shaped antenna has a coiled shape wound a plurality of times.
14. The proximity sensor according to claim 1, wherein the transmission antenna and the reception antenna are formed of a transparent electrode on a transparent substrate.
15. The proximity sensor according to claim 14, wherein the transmission antenna and the reception antenna are formed in a concentric ring shape or a concentric circular arc shape.
16. The transparent substrate has a rectangular shape,
    The transmitting antenna and the receiving antenna are formed in a ¼ arc shape across two sides at a corner of the transparent substrate or a ½ arc shape on a side of the transparent substrate. The proximity sensor according to claim 14.
17. The proximity sensor according to claim 14, wherein at least one of the transmission antenna and the reception antenna is formed in a double or more pattern.
18. A receiving antenna for receiving radio waves,
    A resonant element connected to the receiving antenna;
    Excitation means for exciting the resonant element at a predetermined frequency;
    A radio wave receiver characterized by comprising:
19. The radio wave receiver according to claim 18, wherein the resonant element is a vibrator.
20. The radio wave receiver according to claim 19, wherein the vibrator is a crystal vibrator, a ceramic vibrator, or a MEMS vibrator.

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