JP2531003B2 - Ceramic resonance type electrostatic sensor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ceramic resonance type electrostatic sensor device for detecting a change in a small electrostatic capacitance of an object to be detected by using a high frequency oscillation signal. .

[Conventional technology]

The electrostatic sensor device that has been generally used in the past changes the oscillation frequency by changing the capacitance used in the tank circuit of the oscillation circuit as the change of the external capacitance, but the sensitivity is low. Therefore, in recent years, a more sensitive RCA type device (a type in which the capacitor capacitance of a resonance circuit having a resonance frequency slightly deviated from the oscillation frequency of the oscillation circuit is changed to obtain an AM modulated wave) is used. Is starting to appear. As shown in FIG. 11, this RCA type electrostatic sensor device includes an oscillation circuit section 1 and a resonance circuit 2
And a detection unit 3 that detects a change in electrostatic capacitance with the detection target,
It comprises a detector 4 and an amplifier circuit 5. The oscillation circuit section 1
And the resonance circuit 2 each include a resonator, and the resonance frequency of the resonator of the resonance circuit 2 is modulated according to a minute change in the electrostatic capacitance generated in the detection unit 3, and is extracted as an output signal from the resonance circuit 2 for detection amplification. Is.

As this type of electrostatic sensor device, a device in which one of the resonator of the oscillation circuit section 1 and the resonator of the resonance circuit 2 is configured by using a strip line is widely used. However, if the resonator is composed of strip lines, the strip line length must be at least 1/4 of the wavelength of the light wave, so the strip line length becomes longer, and the device size is reduced. There is a problem that it becomes difficult.

Recently, in order to reduce the size of the device, Japanese Patent Laid-Open No. 58-85948 discloses a structure in which the resonator of the oscillation circuit unit 1 and the resonator of the resonance circuit 2 are both configured by using a dielectric resonator. Proposed. If the resonator is constructed by using a dielectric material as described above, the length of the resonator can be set to ε ^{−1/2 of} that using the strip line. If this dielectric is made of, for example, ceramic, the permittivity ε of the ceramic is 20 to 40, so that the size of the device can be greatly reduced. Further, if the dielectric is made of ceramic, the Q of ceramic is as high as 200 to 300, and higher sensitivity can be expected as compared with the resonator of the strip line.

[Problems to be Solved by the Invention]

However, in this type of electrostatic sensor device, the operating point of the resonator of the resonance circuit 2 is set to a point deviating from the resonance frequency of the resonator of the oscillating circuit section 1. Therefore, the impedance at this operating point is Normally, when the load is 200 to 500Ω or more and a load having an impedance of less than this is coupled to the resonator of the resonance circuit 2, the resonator is Q-dumped (Q becomes low), and the resonator of the ceramic resonator is There is a problem that the original characteristic (characteristic that Q is large) cannot be exhibited and the detection sensitivity cannot be significantly increased.

The present invention has been made to solve the above conventional problems, and an object of the present invention is to provide an ultra-sensitive ceramic resonance type electrostatic sensor device which is downsized.

[Means for solving the problem]

The present invention is configured as follows to achieve the above object. That is, the first aspect of the present invention tunes by an oscillation circuit section that uses a ceramic resonator, a detection section that detects a capacitance change between a detection target and a small change in the capacitance detected by the detection section. In a ceramic resonance type electrostatic sensor device having a ceramic resonator of a resonance circuit in which points change,
A high impedance circuit is connected between the oscillation circuit section and the ceramic resonator of the resonance circuit, and the second invention is a high impedance conversion between the oscillation circuit section and the resonance circuit. A circuit is interposed, and the resonance voltage of the resonance circuit is detected through a high impedance circuit.
According to the invention of claim 2, a variable capacitance diode is provided in the second invention, and a high impedance AFC circuit in which a reverse bias DC voltage is applied to the variable capacitance diode is connected to the resonance circuit to shift the resonance frequency of the resonance circuit. It is configured by being configured.

[Action]

According to the present invention, the high impedance conversion circuit is provided between the ceramic resonator of the oscillation circuit section and the ceramic resonator of the resonance circuit, so that a decrease in Q of the ceramic resonator forming the resonance circuit is suppressed. Has been. Further, if the detection circuit is configured to detect the resonance voltage of the ceramic resonator of the resonance circuit through the high impedance circuit, the impedance around the resonance circuit becomes high and the Q of the ceramic resonator is surely lowered. Therefore, the change in the minute electrostatic capacitance of the detection unit is detected with ultra-high sensitivity.

Then, by coupling a high impedance AFC circuit in which a reverse bias DC voltage is applied to the variable capacitance diode to the resonator of the resonance circuit, the resonance frequency of the ceramic resonator is displaced, and the resonance frequency of the oscillation frequency of the oscillation circuit The gap is optimized.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a circuit diagram of an embodiment of a ceramic resonance type electrostatic sensor device according to the present invention. The device of this embodiment includes an oscillation circuit unit 1, a high impedance conversion circuit 6, and
Resonance circuit 7, detector 4, amplifier circuit 5, AFC circuit 8
Consists of The head of the symbol ∇ in the circuit of FIG. 1 indicates a grounding point.

The oscillation circuit unit 1 is a well-known circuit, and a ceramic resonator 10 that oscillates a super high frequency, in this embodiment, a fixed constant oscillation frequency within a range of 1 GHz to 10 GHz is used. The oscillation circuit unit 1 oscillates the high-frequency oscillation signal and applies it to the resonance circuit 7 via the high impedance conversion circuit 6. The resonance circuit 7 is composed of a ceramic resonator 12, and an electrode plate (not shown), a needle or the like for detecting a change in electrostatic capacitance with a detected object is connected to the detection unit 11.

The ceramic resonator 12 has a frequency characteristic as shown in FIG. 2, and the resonance frequency f ₀ of this ceramic resonator 12 is _0.
On the other hand, the oscillation frequency f ₁ of the oscillation circuit unit 1 is set at a position slightly shifted. This oscillation frequency f ₁ is set by setting the oscillation frequency to the resonance frequency f _{0 of the} ceramic resonator 12.
There is a so-called up-porch method that is set at the position of the frequency f ₂ on the right side of the above and a back porch method that is set at the position of the frequency f _{1 on} the left side of the resonance frequency f ₀ , and any of these methods may be used in this embodiment. , Oscillation frequency back porch f ₁
It is fixed in the position. The resonance frequency f ₀ of the ceramic resonator 12 is displaced according to the change of the electrostatic capacitance with the detected object detected by the detection unit 11, and, for example, the electrostatic capacitance C is + ΔC.
The resonance frequency f ₀ is displaced to f '. In this way, the ceramic resonator 12 changes the resonance frequency according to the change in the electrostatic capacitance with the detection object. At this time, since the oscillation frequency of the oscillation circuit unit 1 is fixed at f ₁ , the output voltage of V ₀ is sent from the ceramic resonator 12 when there is no capacitance change, but the capacitance change is + ΔC. Then, the ceramic resonator 12 outputs the output voltage of V ₁ . In this way, the resonance frequency of the ceramic resonator 12 is displaced according to the change in the capacitance of the detected object, and with this,
The output voltage V corresponding to the change in capacitance is transmitted from the ceramic resonator 12. In this embodiment, the capacitance change detection range is set from 0 to + ΔC, that is, the output voltage setting operation range is set to V _{0 to} V ₁ . Then, the position of the oscillation frequency f ₁ with respect to the resonance frequency f ₀ is determined so that the section from the output voltage V ₂ to V ₁ on the frequency characteristic curve of the ceramic resonator 12 falls within the range of the linear inclination region of the same characteristic. The detection sensitivity is increased. That is, the set operating range V _{0 to} V ₁
Is set by selecting a portion having high impedance in the linear slope region.

In general, a ceramic dielectric has a high Q (large), and a high detection speed can be expected by configuring the resonator of the circuit with the ceramic resonators 10 and 12. Directly connect
Since the impedance of the oscillation circuit unit 1 is lower than the impedance of the ceramic resonator 12 at the operating point, the Q of the ceramic resonator 12 is lowered, and the output voltage at the resonance point is lowered, so that the ceramic resonator 12 is originally designed. However, there is a problem in that the performance (1) (performance with high Q) cannot be sufficiently exhibited. In order to solve such a problem, in this embodiment, the high impedance conversion circuit 6 is provided between the oscillation circuit section 1 and the resonance circuit 7. The high impedance conversion circuit 6 is configured as a high impedance circuit by connecting a transistor 13 and circuit elements such as a resistor and a capacitor, and the transistor 13 adds a high impedance to the ceramic resonator 12 by an emitter follower connection. Mutual interference between the oscillation circuit section 1 on the ceramic resonator 10 side and the resonance circuit 7 on the ceramic resonator 12 side is blocked.

By the way, if the oscillation frequency of the oscillation circuit unit 1 is increased,
Although the device (ceramic resonator) can be miniaturized by that much, if the oscillation frequency of the oscillation circuit unit 1 is set to the ultrahigh frequency as described above, the impedance is further increased, and the Q of the ceramic resonator 12 is kept high, There is a problem that mutual interference easily occurs between adjacent circuits. In addition, if stray distributed capacitance is added to the transistor 13 portion of the high impedance conversion circuit 6 or if the power supply line forms an equivalent inductance 9 as shown in FIG. 3, parasitic oscillation occurs, and as shown in FIG. There is a problem of abnormal oscillation. In the present embodiment, the transistor 13 prevents mutual interference between the oscillation circuit unit 1 and the ceramic resonator 12, but in addition, abnormal oscillation due to the interference of the electric fields of the ceramic resonators 10 and 12 and the power supply line are equivalent. In order to prevent abnormal oscillation due to the formation of a general inductance, the following measures have been taken.

First, in order to avoid mutual interference between the two ceramic resonators 10 and 12, as shown in FIG.
One ceramic resonator (for example, ceramic resonator 10) is arranged on the copper foil on the front surface side of, and the other ceramic resonator (for example, ceramic resonator 12) is arranged on the copper foil on the back surface side of the substrate 14. The ceramic resonator 10 side is arranged so that the electric field on the ceramic resonator 10 side does not reach the ceramic resonator 12 side, or, as shown in FIG. Resonator 10 orientation and ceramic resonator
12 resonators are arranged in a direction orthogonal to each other, and both resonators 1
The electric fields of 0 and 12 are orthogonal to each other so that the electric field on the ceramic resonator 10 side does not reach the ceramic resonator 12 side.

When the + side line (+ V _CC line) 15 and the signal line 16 of the power source are provided on the front surface side of the ceramic substrate 14 and the signal ground lines 17a and 17b are provided on the back surface side of the ceramic substrate 14, for example, The + side line 15 of the power supply is opposed to the ground line 17a, the signal line 16 is opposed to the ground line 17b side to confine the electric field, and the signal ground lines 17a and 17b are connected by the inductance 18. Separated and each ground line 17a, 17b
From one side of power supply + line 15 to bypass capacitor 20
Insert a and 20b to eliminate mutual interference between the circuits. In this embodiment, in order to eliminate the mutual interference of the various modes described above, the circuits are electrically separated from each other as shown in the block diagram of FIG. 6, and the mutual interference between the circuits is reliably eliminated.

The detection unit 4 is connected to the ceramic resonator 12 via a coupling capacitor 25. The detection unit 4 includes an inductance element 21, a diode 22, a capacitor 23, and a resistor.
24 and the ceramic resonator 12
The output signal from is applied to the detection section 4 via the coupling capacitor 25. The diode 22, the capacitor 23, and the resistor 24 form a detection circuit. In the present embodiment, the operating point of the diode 22 is set at a bias point deep enough to the negative side of the zero voltage. The detection circuit performs envelope detection of an output signal (image signal) of super high frequency output from the ceramic resonator 12 and converts it into a signal in the signal band of the object to be detected. In this way, the detection circuit detects the super high frequency signal from the ceramic resonator 12, but at this time, considering the characteristic impedance of the diode 22, the forward impedance of the diode 22 has a great influence on the ceramic resonator 12. Give this diode 22
Is directly connected to the resonator 12, there is a disadvantage that the Q of the resonator 12 is reduced. To prevent this inconvenience, the inductance element 21 is connected to the anode side of the diode 22. That is, the capacitor 25 and the inductance element 21 function as a high impedance circuit.

FIG. 7 shows the ceramic resonator 12 and the coupling capacitor 25.
And a circuit part of the inductance element 21 is extracted and shown.However, in this type of circuit, in general, a stray capacitance C ₀₁ , between the ground line and the signal line and between the anode and the cathode of the diode 22 is shown by a chain line. Although it has C ₀₂ , the inductance element 21 has these stray capacitances C ₀₁ , C
Effectively remove ₀₂ . The inductance element 21 is combined with the coupling capacitor 25 to form an LC resonance circuit. In this case, the resonance point of the LC resonance circuit is set within the detected frequency band and the oscillation frequency band, and a high impedance for the super high frequency component is obtained. It is necessary to

The amplifier circuit 5 is configured by using elements such as a transistor 27 and a resistor. The amplifier circuit 5 amplifies the signal applied from the detection unit 4 and supplies it to a signal processing circuit (not shown), and at the same time, to the AFC circuit 8. Add.

This AFC circuit 8 includes an operational amplifier 28 and capacitors 29, 30.
, Variable resistor 31, resistor 32, variable capacitance diode
33 and the coupling capacitor 34 are configured by the main circuit elements. One terminal of the operational amplifier 28 is an amplifier circuit 5
Of the operational amplifier 28, and the + terminal of the operational amplifier 28 is connected to the sliding terminal of the variable resistor 31. Also, connect a capacitor 29 between one terminal of the operational amplifier and the output terminal.
Is connected to the output terminal of the operational amplifier. One end of the capacitor 30 is connected to the output terminal of the operational amplifier, and the other end of the capacitor 30 is connected to the ground. Further, the output terminal of the operational amplifier is connected to the output terminal side of the ceramic resonator 12 via the resistors 32 and 35 and the coupling capacitor 34. The cathode side of the variable capacitance diode 33 is connected to the connecting portion between the coupling capacitor 34 and the resistor 35.
The anode side of 33 is grounded.

The AFC circuit 8 amplifies the signal applied from the amplifier circuit 5 by the operational amplifier 28. When the signal is amplified, the operational amplifier 28 is smoothed by the smoothing action of the capacitors 29 and 30.
The output signal from is a direct current signal with a low frequency.
Further, the output signal from the operational amplifier 28 passes through an integrating circuit composed of the capacitor 30 and the resistor 32,
A very low signal component is applied to the variable capacitance diode 33 while being amplified to a required level.

The variable capacitance diode 33 is used in a reverse bias state. In this embodiment, when the power supply voltage is 12V, a reverse bias voltage of 6V or more is applied to the variable capacitance diode 33, and the operating point of the diode 33 is changed from 0 voltage. It is set to a deep bias point on the negative side. The position of the operating point of the variable capacitance diode 33 can be adjusted at the DC level by changing the resistance value of the variable resistor 31. In other words, the central operating point of the AFC circuit can be variably set. The variable capacitance diode 33 changes its capacitance according to the voltage applied from the integration circuit, transmits this capacitance change to the ceramic resonator 12 via the coupling capacitor 34, and changes the resonance frequency of the resonator 12. That is, if the resonance frequency of the resonator 12 deviates to the right of f ″ in FIG. 2 for some reason, the output from the resonator 12 is
There is an inconvenience that it becomes V ₀ or less, and it goes out of the set region of V _{0 to} V ₁ . In such a case, the AFC signal is sent to the resonator 1
By adding to 2, the oscillation frequency f ₁ is automatically shifted to the right side so that the output from the resonator 12 does not deviate from the set range of V _{0 to} V _1.
The AFC circuit also functions as a kind of AGC circuit.

The present invention is configured as described above, and
The operation will be described.

As shown in FIG. 8, the oscillation frequency of the oscillating circuit section 1 with respect to the resonance frequency (tuning frequency) f ₀ of the ceramic resonator 12
If the capacitance is not changed from the object to be detected detected by the detector in the state where it is set to a position slightly deviating from f ₁ , the ceramic resonator 12 outputs a constant voltage V _0. It On the other hand, when a person approaches the electrode unit of the detection unit or the surface irregularities such as a VHD disk pass near the electrode of the detection unit, the capacitance detected by the detection unit changes by ΔC. , Ceramic resonator
The resonance frequency of 12 shifts from f ₀ to f ₀₁ . At this time, the oscillation frequency f ₁ is kept at a constant value, the output voltage is taken out from the ceramic resonator 12 is taken out as a voltage of V ₀ + [Delta] V which is added to V ₀ by [Delta] V.

Generally, as shown in FIG. 9, a certain response f
When the signal f (x) is passed through the circuit having (G), the output signal f
It is known that a signal of f (out) = f (G) f (x) can be obtained as (out), and if this is applied to this embodiment, f
If (x) is fixed at a single frequency of jωt ₁ , that is, the oscillation frequency, and f (G) is given by an image signal or a P _x signal corresponding to the movement of a person, f (out) = jωt ₁ It becomes ± P _x , and the amplitude-modulated output is extracted. In this embodiment, if the oscillation frequency is an ultra high frequency, for example, 1 GHz, f (out) becomes an ultra high frequency signal having a bandwidth of ± P _x centered at 1 GHz, and this ultra high frequency signal is Added to the detection circuit. The detection circuit performs envelope detection of this ultra-high frequency signal to convert it into the signal band of the object to be detected (3 MHz signal in this embodiment). The band-converted signal is amplified by the amplifier circuit of the next transistor 27, a part of its output signal is sent to a signal processing circuit (not shown), and the other part of the signal is branched and supplied to the AFC circuit 8. It In the AFC circuit 8, this input signal is almost DC due to the smoothing action of the capacitors 29 and 30.
Then, the signal is amplified to a required level by an integrating circuit and then added to the variable capacitance diode 33. The variable-capacitance diode 33 changes the capacitance according to the applied signal, and the resonance frequency f ₀ of the ceramic resonator 12 is changed by this capacitance change.
To be adjusted optimally.

According to the present embodiment, since the resonator of the oscillation circuit unit 1 and the resonator of the resonance circuit are both configured by the ceramic resonators 10 and 12, Q can be set to a large value.
Moreover, the circuit around the ceramic resonator 12, that is,
Since the impedance conversion circuit 6, the resonance circuit of the inductance element 21 and the capacitor 25, and the AFC circuit 8 are configured by a high impedance circuit, Q dump is not generated during the operation of the ceramic resonator, and high sensitivity is achieved. It is possible to detect a small change in the capacitance.

Further, mutual interference is blocked by the transistor 13 between the oscillation circuit unit 1 and the ceramic resonator 12,
Also, because mutual interference is prevented by the electric field between the ceramic resonators 10 and 12, and the electric field between the ground lines 17a and 17b and the + side line of the power supply is confined, it occurs when handling the super high frequency signal. Mutual interference between the respective circuits, which is easy to perform, can be surely prevented, and thereby a high S / N ratio of the device can be achieved.

Further, since the resonator is composed of the ceramic resonators 10 and 12 without using the strip line, the device can be made extremely small, and in this embodiment, it is 20 mm in length × 20 mm in width × 20 mm in height.
That was an extremely small device.

Further, according to the apparatus of this embodiment, 1 × 10 ⁻³ to 1 × 10 ⁻⁵ PF
It is possible to detect the minute electrostatic capacitance of the device with high sensitivity. Therefore, the device of the present embodiment can detect the electrostatic capacitance change between the video disc and the stylus, which is a conventional general application. Not only as an apparatus, but also for applications that can be made possible only by highly sensitive detection of a minute volume, for example, a human body volume sensor (person's indoor intrusion sensor), a high temperature installation sensor (eg, position sensor in a high temperature furnace), a high resolution rotary encoder, Micro component detection element (for example, detection element such as chip capacitor on carrier tape), gas sensor (gas identification sensor that utilizes difference in capacitance depending on gas type), pulse sensor (iron content in blood) Pulse detection sensor that uses changes in the amount of passage of the liquid phase), phase transition point detection sensor (solid, liquid, gas phase diagram of liquid phase and solid phase) To provide a highly sensitive and reliable microminiature electrostatic sensor device that has a completely new function such as a sensor for detecting a change in the dielectric constant at the transition point between the body phase and the solid phase, and has a purpose. Is possible.

Further, in the present embodiment, the operating point of the diode 22 is set at a position sufficiently distant from the 0 voltage, and compared with the case where this operating point is set to a negative voltage close to the 0 voltage, the following adverse effects are produced. It can be prevented. That is, when the operating point of the diode 22 is set to a position close to 0 voltage, the variable capacitance diode 33 is turned on when the amplitude of the signal exceeds the voltage of 0 and becomes a positive voltage. It reduces the impedance of 33, which causes the Q of the ceramic resonator 12 to
However, by setting the operating point of the diode 22 at a position sufficiently distant in the negative direction from the 0 voltage as in the present embodiment, the diode 22 conducts with the amplitude component of the signal. Therefore, the impedance of the variable capacitance diode 33 can be always maintained at a high value, and the Q dump of the ceramic resonator 12 can be prevented.

The present invention is not limited to the above embodiment,
Various embodiments can be adopted. For example, in the above embodiment, the high impedance conversion circuit 6 is configured by a circuit that is a combination of the transistor 13 and a resistor, but it may be configured by a circuit that is only a transistor.
Alternatively, it may be configured by another circuit element such as an operational amplifier. When selecting these circuit elements, those that match the oscillation frequency of the oscillation circuit section 1 are selected.

Further, in the above embodiment, the inductance element 21 is
Although the ceramic resonator 12 is connected in parallel as shown in the figure, it may be connected in series as shown in FIG.

〔The invention's effect〕

In the present invention, the resonator of the oscillation circuit section and the resonator of the resonance circuit are both configured by a ceramic resonator, and a high impedance conversion circuit is provided between the ceramic resonators.
It is possible to prevent the load on the oscillator circuit side, which is the low impedance side, from reaching the ceramic resonator side of the resonance circuit, which prevents the Q dump of the ceramic resonator of the resonance circuit, and it is possible to achieve a very low static level with high sensitivity. It is possible to detect the change in the capacitance.

In addition, high impedance is achieved not only between the peripheral part of the resonance circuit, that is, between the ceramic resonator of the resonance circuit and the oscillation circuit part, but also between the detection circuit that is the signal output side of the resonance circuit. In addition, the Q of the ceramic resonator of the resonance circuit can be maintained high, and the Q dump of the ceramic resonator of the resonance circuit can be prevented more effectively. That is, the high Q performance originally possessed by the ceramic resonator can be fully exhibited, and a minute capacitance change can be detected with high sensitivity.

Further, as described above, since the resonator of the oscillation circuit section and the resonator of the resonance circuit are both configured by the ceramic resonator, the device can be drastically compared with the conventional stripline configuration. It is possible to reduce the size and weight.

Furthermore, since the device configuration is simple, it is possible to obtain the excellent effect that the device of the present invention having excellent performance can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a ceramic resonance type electrostatic sensor device according to the present invention, and FIG. 2 is an explanation showing a relationship between an oscillation frequency of an oscillation circuit section and a resonance frequency of a ceramic resonator of a resonance circuit. 3 and 4 are explanatory diagrams of a faulty state in which the power supply line constitutes an equivalent inductance when handling an ultra-high frequency signal, and FIG. 4 is an explanatory diagram of abnormal oscillation caused by stray distributed capacitance and parasitic vibration. FIG. 5 shows an example of blocking mutual interference, and FIGS. 5 (a) and 5 (b) are explanatory views of an example of preventing mutual interference due to an electric field between the ceramic resonator of the oscillation circuit section and the ceramic resonator of the resonance circuit. FIG. 5 (c) is an explanatory view showing an example of preventing mutual interference due to electric field containment between the signal ground line and the power source + line, and FIG. 6 is a state in which each circuit is connected separately from the mutual interference. 7 is a block diagram of FIG. Is a detailed explanatory view showing an example of connection of an impedance element provided between the ceramic resonator of the oscillation circuit and the detection circuit, and FIG. 8 is a diagram of this embodiment in which a minute electrostatic capacitance is detected by tuning displacement of the ceramic resonator. Operation explanatory diagram, FIG. 9 is an explanatory diagram showing an example of response conversion of a signal, FIG.
FIG. 10 is an explanatory view showing another connection example of the impedance element 21 connected between the ceramic resonator of the resonance circuit and the detection circuit, and FIG. 11 is a block diagram of a conventional RCA type electrostatic sensor device. . 1 ... Oscillation circuit part, 2 ... Resonance circuit, 3 ... Detection part, 4
...... Detection unit, 5 ... Amplification circuit, 6 ... High impedance conversion circuit, 7 ... Resonance circuit, 8 ... AFC circuit, 9 ... Inductance, 10 ... Ceramic resonator, 11 ... Detection unit, 12 ...... Ceramic resonator, 13 ...... Transistor, 14
…… Ceramic board, 15 …… + side of power supply, 16 ……
Signal line, 17a, 17b …… Ground line, 18 …… Inductance, 20a, 20b …… Bypass capacitor, 21 ……
Inductance element, 22 ... diode, 23 ... capacitor, 24 ... resistor, 25 ... coupling capacitor, 26 ... variable resistor, 27 ... transistor, 28 ... operational amplifier, 2
9,30 ... Capacitor, 31 ... Variable resistor, 32 ... Resistor, 33 ... Variable capacitance diode, 34 ... Coupling capacitor, 35 ... Resistor.

Claims (3)

(57) [Claims] 1. An oscillation circuit section using a ceramic resonator,
Ceramic resonance type electrostatic sensor having a detection part for detecting a change in electrostatic capacitance with an object to be detected and a ceramic resonator of a resonance circuit in which a tuning point is changed by a slight change in electrostatic capacitance detected by the detection part In the device, a ceramic resonance type electrostatic sensor device is characterized in that a high impedance circuit is connected between the oscillation circuit section and the ceramic resonator of the resonance circuit. 2. An oscillation circuit section using a ceramic resonator,
Ceramic resonance type electrostatic sensor having a detection part for detecting a change in electrostatic capacitance with an object to be detected and a ceramic resonator of a resonance circuit in which a tuning point is changed by a slight change in electrostatic capacitance detected by the detection part In the device, a high-impedance conversion circuit is interposed between the oscillation circuit section and the resonance circuit, and the resonance voltage of the resonance circuit is detected through the high-impedance circuit. 3. A variable-capacitance diode is provided, and a high-impedance AFC circuit in which a reverse bias DC voltage is applied to the variable-capacitance diode is connected to the resonance circuit to shift the resonance frequency of the resonance circuit. A ceramic resonance type electrostatic sensor device according to the second term of the range.