JPH0830724B2 - Multiple electrostatic sensor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a multiple electrostatic sensor device in which a plurality of sensor circuits for detecting a change in external capacitance and outputting the detection signal are arranged in series. It is about.

[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. For this reason, in recent years, a more sensitive RCA device (a system for obtaining an AM modulated wave by changing the capacitor capacity of the tuning circuit having a resonance frequency slightly deviated from the oscillation frequency of the oscillation circuit) is used. Is starting to appear. This RCA type electrostatic sensor device has an oscillation circuit 1 and a tuning circuit 2 as shown in FIG.
And a detection unit 3 that detects a change in electrostatic capacitance with the detection target,
It comprises a detection circuit 4 and an amplification circuit 5. The oscillator circuit 1
The tuning circuit 2 and the tuning circuit 2 each include an independent resonator. For example, as shown in FIG. 4, the resonance frequency f ₀ of the tuning circuit 2 is slightly deviated from the fixed oscillation frequency f ₁ of the oscillation circuit 1. The resonance frequency is deviated from f ₀ by Δf in correspondence with the change ΔC of the small electrostatic capacitance detected by the detection unit 3, and the change ΔC of the electrostatic capacitance is changed to the change of the output voltage ΔV. It is converted, detected and amplified, and taken out.

[Problems to be Solved by the Invention]

In recent years, there has been a demand for parallel processing of detection signals of capacitance detected by an electrostatic sensor device in a plurality of different forms, and for further accuracy of analysis of detection signals. In order to achieve the parallel processing of the signals, it is conceivable to arrange a plurality of series of sensor circuits adjacent to each other from the oscillation circuit 1 to the amplifier circuit 5. Further, in order to achieve accurate signal analysis, the It is conceivable to form at least two series of one series of sensor circuits from the circuit 1 to the amplifier circuit 5 and obtain the differential output of the output signal of each series.

However, when a plurality of sensor circuits from the oscillation circuit 1 to the amplification circuit 5 are arranged adjacent to each other, in particular, 1 × 10
-When attempting to detect electrostatic capacitance minutely with a high sensitivity of about ^-5 PF, disturbances other than detection signals and the effects of stray distributed capacitance generated when an electrostatic sensor device is incorporated into the device under test are considered. Therefore, it becomes difficult to match the oscillation frequencies of the sensor circuits of the respective series. If the oscillation frequency of each series deviates even a little, the oscillation frequencies of each series cause mutual interference such as resonance. For example, when one adjacent oscillation frequency is f ₀ and the other oscillation frequency is f ₀ ′, mutual interference causes a beat frequency of f ₀ ′ −f ₀ or f ₀ ′ + f ₀ , which becomes a disturbance. As a result, there arises a problem that accurate signal processing cannot be performed.

The present invention has been made to solve the above problems, and an object thereof is to provide a multiple electrostatic sensor device capable of performing accurate signal processing without causing mutual interference of oscillation frequency signals of each series. To do.

[Means for Solving the Problems] In order to achieve the above object, the present invention is configured as follows. That is, the multiple electrostatic sensor device of the present invention has, firstly, an oscillation circuit that oscillates a frequency signal; and an independent resonator for detection that is separate from the oscillation circuit, and is detected by the detection unit. A tuning circuit that changes the tuning point of the detecting resonator in response to a change in the external capacitance, and outputs signals corresponding to the change in the tuning point as independent detection signals of the change in the external capacitance; A multi-electrostatic sensor device in which a plurality of series of sensor circuits having one series of independent detection capabilities are formed, the plurality of series of sensor circuits share one common oscillation circuit, and the common oscillation circuit The circuit is characterized in that a frequency signal is applied from each circuit to each series of tuning circuits.
An oscillating circuit for oscillating a frequency signal; an oscillating circuit having an independent detecting resonator separate from the oscillating circuit, and a tuning point of the detecting resonator in response to a change in external capacitance detected by the detecting section And a tuning circuit that outputs a signal corresponding to the change of the tuning point as an independent detection signal of the external capacitance change, and a series of sensor circuits having an independent detectability are formed in an even number series, The number of sensor circuits of each series is 1
The common oscillation circuit is shared, and the frequency signal is applied to the tuning circuit of each series from the common oscillation circuit. Further, the sensor circuit of each pair including two series of sensor circuits is used. An output circuit for transmitting the differential output of each pair is connected, and the present invention is thirdly characterized in that at least the resonator of the tuning circuit is composed of a dielectric resonator. It is characterized by being present.

[Action]

In the present invention, a high frequency signal is applied to the tuning circuit of each series of sensor circuits from one common oscillator circuit.
Then, each sensor circuit changes the tuning point with the frequency signal in response to the change of the external capacitance detected by the detection unit, and the detection signal corresponding to the change of the external capacitance is output from the tuning circuit of each series. To be done. The detection signal output from the tuning circuit is detected and amplified, and then output from the output circuit. This output circuit is configured to correspond to the intended signal processing form. For example, when the signals of each series are processed independently and in parallel, the signals of each series are amplified and output, and a pair When it is desired to obtain the differential output of the signals of the series, the signals of the series of pairs are output through the differential amplifier.

〔Example〕

An embodiment of a multiple electrostatic sensor device according to the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit diagram of a first embodiment of a multiple electrostatic sensor device according to the present invention.
The device of this embodiment includes an oscillation circuit 1 and a single tuning circuit 2.
, A detection circuit 4, an amplification circuit 5, and an AFC circuit 8 having a series of independent detection capabilities that share the oscillation circuit 1 and have an even number of columns. In the present embodiment, 13a and 13b have two lines. The output signals of the sensor circuits of each series are arranged so as to be adjacent to each other and are differentially output by the differential amplifier 7 as an output circuit.

Figure 2 shows the details of a series of sensor circuits.
The oscillator circuit 1 uses a ceramic resonator 10 as a dielectric resonator that oscillates a super high frequency, in this embodiment, a fixed and constant oscillation frequency within the range of 0.5 GHz to 5 GHz.
The oscillation circuit 1 oscillates the high-frequency oscillation signal, which is distributed from the output side of the high impedance converter 6 to the distribution resistor 9a.
Through the tuning circuit 2. The tuning circuit 2 is composed of a ceramic resonator 12 as a dielectric resonator, which is independent of the dielectric resonator 10 of the oscillation circuit 1, and has a capacitance of a capacitance with a detection object (not shown) in the detection unit 11. Electrode plates for detecting changes, detection needles, etc. are provided.

The detection circuit 4 is connected to the ceramic resonator 12 via a coupling capacitor 25, and the detection circuit 4 is composed of an inductance element 21, a diode 22, a capacitor 23, and a resistor 24. Resonator
The output signal from 12 is applied to the detection circuit 4 via the coupling capacitor 25. The diode 22
, The capacitor 23, and the resistor 24 constitute a detection unit of the detection circuit. In this embodiment, the operating point of the diode 22 is 0.
The bias point is set deep enough to the negative side of the voltage. The detecting section is for performing envelope detection of an output signal of ultrahigh frequency output from the ceramic resonator 12 and converting it into a signal in the signal band of the object to be detected. As described above, the detector detects the ultra-high frequency signal from the ceramic resonator 12. At this time, considering the characteristic impedance of the diode 22, the forward impedance of the diode 22 has a great effect on the ceramic resonator 12. 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 to prevent the Q from decreasing.

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 circuit 4 and supplies it to the output circuit, and at the same time, the AF circuit
Add to C circuit 8.

This AFC circuit 8 includes an operational amplifier 28 and capacitors 29, 30.
, A variable resistor 31, resistors 32 and 35, a variable capacitance diode 33, and a coupling capacitor 34 as main circuit elements. The negative terminal of the operational amplifier 28 is connected to the output terminal of the amplifier circuit 5, and the positive terminal of the operational amplifier 28 is connected to the sliding terminal of the variable resistor 31.
Also, connect a capacitor between the negative terminal of the operational amplifier and the output terminal.
29 is connected, one end of a capacitor 30 is connected to the output end 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, and the anode side of the variable capacitance diode 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 12 V, a reverse bias voltage of 6 V or more is applied to this variable capacitance diode 33,
The operating point of the diode 33 is set to a deep bias point on the negative side from 0 voltage. In addition, this variable capacitance diode 33
The position of the operating point 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, for some reason, the resonance frequency of the resonator 12 is, for example, as shown in FIG.
When it is shifted to the right of f _0, the output from the resonator 12 is V ₀
The following occurs, which causes a problem that the resonance frequency characteristic curve deviates from the setting region of V _{0 to} V ₁ defined within the high impedance range in the linear region. In such a case, by adding an AFC circuit to the resonator 12, the oscillation frequency f ₁ is automatically shifted to the right, and the output from the resonator 12 is
It is to prevent it from falling out of the design range of V _{0 to} V ₁ ,
In this sense, this AFC circuit also functions as a kind of AGC circuit. In addition, the head of the symbol in the circuit of FIG. 2 indicates the ground point.

In the first embodiment, one series of sensor circuits configured as described above are provided in two series by sharing the oscillation circuit 1 with 13a and 13b. A signal is applied to the tuning circuit 2 of each series via the distribution resistors 9a and 9b. The signal sent from the amplifier circuit 5 of each series of sensor circuits 13a and 13b is added to the differential amplifier 7 as an output circuit.

The first embodiment is configured as described above, and its operation will be described below. Regarding this operation description, the second circuit corresponding to the first series sensor circuit 13a is used.
Numbers are attached to the circuit portions of the sensor circuit 13 of the series to distinguish them from each other.

As shown in FIG. 4, the oscillation frequency f _{1 of the} oscillation circuit 1 is different from the resonance frequency (tuning frequency) f ₀ of the ceramic resonator 12.
When is set to a position that is slightly displaced,
For example, when the detected body 14 moves, the detection needles 17 of the detection units 11 and 11 ′,
A small change in the capacitance with the object to be detected 14 detected by 17 'occurs, and the resonance points of the tuning circuits 2 and 2'change by Δf ₁ and Δf ₁ '. That is, in FIG. 4, the tuning points A, A'for the oscillation frequency f ₁ of the tuning circuits 2, 2'change to B, B ', and ΔV,
A voltage change of ΔV 'occurs. Change component Delta] f ₁ of the resonance frequency in the tuning circuit 2 and 2 'in the oscillation frequency f ₁ tuning circuit 2, 2', multiplication of a Delta] f ₁ 'is performed. That is, in the first series sensor circuit 13a, the frequency signal of the oscillation frequency f ₁ is multiplied by the change component Δf ₁ of the resonance point, and
In the second series sensor circuit 13b, the frequency signal of the oscillation frequency f ₁ is multiplied by the change component Δf ₁ ′ of the resonance point to obtain the so-called voltage change ΔV, ΔV ′ AM modulation. In this embodiment, if the oscillation frequency is an ultra-high frequency, for example, 1 GHz, the modulated signal of each series is centered at 1 GHz and becomes an ultra-high frequency signal having a bandwidth corresponding to the movement of the detected body 14,
This ultra high frequency signal is applied to the corresponding detection circuit 4, 4 '. The detection circuits 4 and 4'perform envelope detection on this ultra-high frequency signal and convert it into the signal band of the detected object 14 (3 MHz signal in this embodiment). This band-converted signal is amplified
Amplified by 5, 5 ', a part of the output signal is sent to the differential amplifier 7 as an output circuit, and the other part of the signal is branched and supplied to the corresponding AFC circuit 8, 8'. In the AFC circuits 8 and 8 ', the input signal is reduced to 400 mHz, which is almost DC, by the smoothing action of the capacitors 29 and 30, and further amplified by a integrating circuit to a required level and 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 optimally adjusted by this capacitance change.

On the other hand, the differential amplifier 7 obtains the difference between the signal added from the first series amplifier circuit 5 and the signal added from the second series amplifier circuit 5'and amplifies the difference to obtain a single differential detection signal. The signal is added to a signal processing circuit (not shown) or the like.

As described above, in the first embodiment, since the two series of sensor circuits 13a and 13b share the single oscillation circuit 1, the oscillation frequencies of each series cause resonance to generate the beat frequency. The problem of mutual interference does not occur at all, and highly accurate and reliable signal processing can be performed in areas where high sensitivity detection such as condenser microphones, human body detection sensors, and rotary encoders is desired. .

Further, as described above, since one oscillator circuit may be provided for a plurality of series of sensor circuits, the size and weight of the device can be significantly reduced as compared with the case where an oscillator circuit is provided for each series. It becomes possible to do.

In the first embodiment, two series of sensor circuits 13a,
Although the device is formed by 13b, it is also possible to form the sensor circuit by a plurality of even columns and configure two series as one pair and obtain the differential output for each pair. Further, in the above example, the differential output between the detection information of the sensor circuit 13a and the detection information of the sensor circuit 13b is obtained, but the sensor circuit on one side is used for compensation and the differential between the detection signal and the compensation signal is used. You can also ask for the output.

FIG. 3 shows a second embodiment of the multiple electrostatic sensor device according to the present invention. This second embodiment has 1
A plurality of sensor circuits 13a, 13 sharing one oscillator circuit 1
b, 13c are arranged adjacent to each other, and operational amplifiers 15, 15 ', 15 "are provided on the output side of the amplifier circuits 5, 5', 5" of the sensor circuits 13a, 13b, 13c of each series.
The operational amplifiers 15, 15 ', 15 "are connected to each other, and the output signals from the sensor circuits 13a, 13b, 13c of the respective series are amplified independently and individually, and the target signal processing circuits 16, 16', 16" are obtained. The other configurations are the same as those in the first embodiment.

In the second embodiment, each series of sensor circuits 13a, 13b,
The detection signal of the small capacitance detected by 13c is amplified by the operational amplifiers 15, 15 ', 15 ", and then processed in parallel by the corresponding signal processing circuits 16, 16', 16".

It should be noted that the present invention is not limited to the above-mentioned embodiments, and various modes of implementation can be adopted. For example, in each of the above embodiments, the resonator 10 of the oscillation circuit 1 and the tuning circuits 2, 2 ', 2 "
Both the resonator 12 of and the resonator 12 are composed of a dielectric resonator.
Any of these can be configured by a strip line, and the resonator of the oscillation circuit 1 can be configured by a strip line, and the tuning circuits 2, 2 ', of the sensor circuits 13a, 13b, 13c,
It is also possible to configure the 2 ″ resonator 12 by a dielectric resonator. In this case, both the resonator of the oscillation circuit 1 and the tuning circuit or the tuning circuit side resonator is made of a dielectric resonator. If it is configured, the device can be miniaturized, that is, if the resonator is composed of strip lines, the strip line length must be at least 1/4 of the oscillation frequency wavelength. On the other hand, when the resonator is made of a dielectric material as in the above embodiments, if the dielectric constant of the dielectric resonator is ε, , Compared with the one using a strip line, the length of the resonator is ε
It can be ^halved . If the dielectric resonator is composed of a ceramic resonator, the dielectric constant ε of the ceramic is 40 ~
Since it is 90, the size of the device can be greatly reduced. The inventor compared the case where the resonator of the oscillation circuit and the tuning circuit is formed with a strip line and the case where the resonator is formed with a ceramic resonator, and if formed with a ceramic resonator, the shape can be downsized to 1/6, We were able to confirm that the weight could be reduced to 1/10. Also, the ceramic Q is
It is as high as 200 to 300, which means that higher sensitivity can be expected compared to stripline resonators.

Further, as an embodiment of the present invention, one oscillator circuit 1 is commonly used to form a plurality of series of sensor circuits, and one group of the sensor circuits obtains a differential output for each pair, and sensors of the other groups are formed. It is also possible for the circuits to independently perform parallel processing of signals.

Further, in each of the above-described embodiments, the detection circuit is configured by the envelope detection circuit, but it may be configured by the peak detection circuit.

〔The invention's effect〕

Since the present invention forms a plurality of series of sensor circuits by sharing one oscillation circuit, there is no mutual interference between the oscillation frequencies of the series of sensor circuits. It is possible to perform desired signal processing of the sensor circuit with high accuracy.

Further, since it is sufficient to prepare one oscillation circuit for a plurality of sensor circuits, the device configuration can be simplified and the device can be downsized in comparison with the system in which an oscillation circuit is provided for each series of sensor circuits. It is possible to significantly reduce the weight.

Furthermore, if both the resonator of the oscillation circuit and the resonator of the tuning circuit independent of this oscillation circuit or the resonator of the tuning circuit is composed of a dielectric resonator, the device can be made even smaller and lighter. It is possible to improve the detection sensitivity of the device.

Further, as described above, since the oscillation frequencies of the sensor circuits of each series do not cause mutual interference at all, the sensor circuits can be arranged in close proximity to each other, and the packaging density of the circuits can be increased.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of a multiple electrostatic sensor device according to the present invention, FIG. 2 is a detailed circuit diagram of a sensor circuit constituting the same embodiment, and FIG. FIG. 4 is a circuit diagram showing a second embodiment of a continuous electrostatic sensor device, FIG. 4 is an explanatory view of an example of detecting a small electrostatic capacitance in the electrostatic sensor device, and FIG. 5 is a block diagram showing a conventional electrostatic sensor device. Is. 1 ... Oscillation circuit, 2,2 ', 2 "... Tuning circuit, 3 ... Detection part, 4,4', 4" ... Detection circuit, 5,5 ', 5 "... Amplification circuit,
6 ... High impedance converter, 7 ... Differential amplifier, 8
...... AFC circuit, 9a, 9b, 9c …… Distribution resistor, 10 …… Ceramic resonator, 11 …… Detector, 12 …… Ceramic resonator,
13a, 13b, 13c …… Sensor circuit, 14 …… Detected object, 15,1
5 ′, 15 ″ …… Op Amp, 16,16 ′, 16 ″ …… Signal processing circuit, 17,17 ′, 17 ″ …… Detection needle, 21 …… Inductance element, 22 …… Diode, 23 …… Capacitor, 24 …… resistor, 25 …… coupling capacitor, 27 …… transistor, 28…
… Op Amp, 29,30 …… Capacitor, 31 …… Variable resistor, 32 …… Resistor, 33 …… Variable capacitance diode, 34 ……
Coupling capacitor, 35 ... Resistor.

Claims (3)

[Claims] 1. An oscillating circuit for oscillating a frequency signal; and an oscillating circuit, which has an independent detecting resonator separate from the oscillating circuit, for detecting a change in external capacitance detected by a detecting section. A tuning circuit that changes the tuning point of the resonator and outputs a signal corresponding to the change of the tuning point as an independent detection signal of the external capacitance change; Is a multiple electrostatic sensor device in which a plurality of series are formed, the plurality of series of sensor circuits share one common oscillation circuit, and a frequency signal is supplied from the common oscillation circuit to each series of tuning circuits. Multiple electrostatic sensor devices added. 2. An oscillating circuit for oscillating a frequency signal; and an oscillating circuit which is independent of the oscillating circuit and is provided for detection independently of the oscillating circuit. A tuning circuit that changes the tuning point of the resonator and outputs a signal corresponding to the change of the tuning point as an independent detection signal of the external capacitance change; Are formed in even series, the sensor circuits of each series share one common oscillation circuit, and a frequency signal is applied to the tuning circuit of each series from the common oscillation circuit. A multiple electrostatic sensor device in which an output circuit that sends out a differential output of each pair is connected to each pair of sensor circuits. 3. The resonator according to claim 1, wherein at least the resonator of the tuning circuit is formed of a dielectric resonator.
The multiple electrostatic sensor device according to the item.