WO2011092980A1 - 可変容量装置 - Google Patents
可変容量装置 Download PDFInfo
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- WO2011092980A1 WO2011092980A1 PCT/JP2010/073119 JP2010073119W WO2011092980A1 WO 2011092980 A1 WO2011092980 A1 WO 2011092980A1 JP 2010073119 W JP2010073119 W JP 2010073119W WO 2011092980 A1 WO2011092980 A1 WO 2011092980A1
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- 238000001514 detection method Methods 0.000 claims abstract description 50
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
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- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G5/00—Capacitors in which the capacitance is varied by mechanical means, e.g. by turning a shaft; Processes of their manufacture
- H01G5/16—Capacitors in which the capacitance is varied by mechanical means, e.g. by turning a shaft; Processes of their manufacture using variation of distance between electrodes
- H01G5/18—Capacitors in which the capacitance is varied by mechanical means, e.g. by turning a shaft; Processes of their manufacture using variation of distance between electrodes due to change in inclination, e.g. by flexing, by spiral wrapping
Definitions
- the present invention relates to a variable capacitance device that realizes a variable capacitor using a MEMS driven by electrostatic force.
- varactor diodes are used as variable capacitors.
- a varactor diode is a kind of semiconductor diode. When a reverse voltage is applied, a depletion layer without carriers is formed at the PN junction, and the varactor diode operates as a capacitor having a capacitance according to the thickness of the depletion layer. When the magnitude of the reverse voltage applied to the varactor diode is changed, the thickness of the depletion layer changes and the capacitance changes, so that the varactor diode can be operated as a variable capacitor.
- the varactor diode has a small Q as a capacitor and a large loss, it cannot often be used in a circuit that requires a low-loss capacitor such as a circuit for wireless communication. For this reason, in a circuit for wireless communication or the like, a variable capacitance device that drives an MEMS by electrostatic force may be used as a low-loss variable capacitor (see Patent Documents 1 and 2).
- FIG. 1 is a diagram illustrating a configuration example of a variable capacitance device using a conventional MEMS.
- the variable capacitance device 101 includes a movable plate 102 and a substrate 103.
- the movable plate 102 is manufactured as a MEMS that can be physically moved up and down using a fine processing technique, and is connected to the substrate 103 via a spring structure (not shown).
- Two sets of opposing electrode pairs are formed on the substrate 103 and the movable plate 102, and each electrode pair constitutes a capacitance section 105, 106.
- the electrostatic capacity unit 105 generates a driving capacity by applying a driving voltage, and an electrostatic attraction determined according to the driving voltage attracts the movable plate 102 to the substrate 103, and the electrostatic attraction and the spring force of the spring structure are generated.
- the movable plate 102 stops at the balance position.
- the capacitance unit 106 is inserted into a signal line to which a high frequency signal is applied, and becomes a variable capacitor having a capacitance corresponding to the stop position of the movable plate 102.
- the variable capacitance device 101 having such a configuration can be used as a low-loss variable capacitor by optimizing the overall design using a dielectric material having a low dielectric loss tangent or a low-resistance conductor material.
- variable capacity device is the capacity binary switching type.
- the capacity binary switching type has two stop positions of the movable plate, and the variable capacitor has a large capacity at one stop position, and the variable capacitor has a small capacity at the other stop position.
- a continuously variable capacity type is a type of variable capacity device that can be reduced in size and cost.
- the continuously variable capacitance type the movable plate is continuously displaced according to the driving voltage, and the capacitance of the variable capacitor is also continuously changed.
- the continuous capacitance variable type is advantageous for downsizing and cost reduction, but the variation in the capacitance characteristics of the variable capacitor with respect to the drive voltage remains unchanged, while the variation in processing of the spring structure remains unchanged. The variation in current MEMS processing is sufficient. It is very difficult to make it very small, and it becomes a problem.
- the electrostatic attraction is generated not only by the electrostatic attraction generated by the drive capacity but also by the signal voltage applied to the variable capacitor.
- variable capacitor brings the movable plate closer to the substrate, and the variable capacitance is set according to the setting. There is also a phenomenon that increases (self-activation), which is a problem. Because of these problems, it is considered that the capacity binary switching type is suitable for practical use in the study of the current variable capacity device.
- an object of the present invention is to provide a variable capacitance device that can realize the capacitance of a variable capacitance with high accuracy even if it is a continuously variable capacitance type that has a small loss and is advantageous for downsizing and cost reduction. .
- the variable capacitance device of the present invention includes a substrate, a movable structure portion, a drive capacitance portion, a variable capacitor portion, and a drive voltage control circuit.
- the movable structure is connected to the substrate via a spring structure.
- the drive capacity unit causes an electrostatic attractive force based on a drive capacity generated by applying a DC voltage to act between the movable structure unit and the substrate.
- the electrostatic capacitance generated when the RF signal is applied changes according to the positional relationship between the movable structure portion and the substrate.
- the drive voltage control circuit detects a detection voltage that changes according to the drive capacity, and controls the DC voltage applied to the drive capacity unit so that the detected voltage approaches a desired value.
- the drive voltage control circuit is provided with a function of grasping the drive capacity of the drive capacitor unit based on the detected voltage, and the DC voltage applied to the drive capacitor unit is controlled so that the detected voltage approaches a desired value.
- the positional relationship between the movable structure portion and the substrate and the setting accuracy of the drive capacity can be increased, and as a result, the capacitance accuracy of the variable capacitor portion can be increased.
- the drive voltage control circuit applies the drive capacity unit to the drive capacitor unit so as to correct the variation and variation even if there is variation in the spring force of each product and the positional relationship between the movable structure and the substrate due to self-activation.
- the DC voltage can be automatically controlled to increase the capacitance accuracy of the variable capacitor unit.
- the drive voltage control circuit preferably includes a direct current source and an alternating current source, and preferably generates a detection voltage based on a converted voltage from an AC current flowing through the drive capacitor unit.
- the direct current source applies a DC voltage to the drive capacitor unit, and the alternating current source superimposes an AC voltage for capacitance detection on the DC voltage.
- the capacitance detection AC voltage output from the AC source since the DC voltage output from the direct current source is controlled, it is difficult to grasp the drive capacity from the DC voltage. Therefore, by outputting the capacitance detection AC voltage output from the AC source as a constant, it is possible to grasp the drive capacitance from the detection voltage based on the AC current flowing in the drive capacitance section.
- the drive voltage control circuit of the present invention further includes a reference capacitor having a known capacitance value and generates a detection voltage based on an AC current flowing through the reference capacitor and an AC current flowing through the drive capacitor unit.
- the series circuit composed of the reference capacitor unit and the resistor and the series circuit composed of the drive capacitor unit and the resistor may be connected in parallel, and the detection voltage may be generated based on the voltage difference at the connection point in each series circuit.
- a reference capacitor and the drive capacitor may be connected in series, and the detection voltage may be generated based on the voltage at the connection point.
- the detection voltage is sampled at a timing at which the voltage drop due to the drive capacitance portion in the detection voltage is maximized.
- the voltage drop due to the capacitive component in the detection voltage is: A phase shift of 90 ° occurs with respect to the phase based on the AC voltage for capacitance detection.
- there is no phase shift in the voltage drop due to the resistance component in the detection voltage if the detected voltage is detected at the timing when the phase with respect to the AC voltage for capacitance detection becomes 0 ° or 180 °, the voltage drop due to the resistance component is canceled and the voltage drop due to the capacitance component is maximized.
- the detection voltage can be sampled at the timing of Thereby, the capacity
- the sampling value of the detection voltage may be increased or decreased as compared with the external input voltage.
- the movable structure of the present invention may be a conductor or an insulator. If the movable structure portion is a conductor, it is not necessary to form another electrode (conductor film) on the movable structure portion, so that the manufacturing is easy. If the movable structure portion is an insulator, it is necessary to form an electrode on the movable structure portion again, which makes the manufacturing complicated. However, the variable capacitor portion and the drive capacitance portion can be electrically separated, so that the variable structure portion is variable. The design of the peripheral electric circuit connected to the capacitor is facilitated.
- single crystal low-resistance silicon doped with a high concentration of impurities and having a volume resistivity of 0.01 ⁇ cm or less is preferable because loss can be reduced.
- an insulator it is preferable that single crystal silicon has a volume resistivity of 10 k ⁇ cm or more because the electric separation between the variable capacitor portion and the drive capacitor portion can be enhanced. Since single crystal silicon can be used for high-precision fine processing such as RIE or anisotropic etching using an alkaline solution, production with reduced variation becomes possible. Further, if the substrate is made of glass, the silicon movable structure can be bonded using highly reliable anodic bonding, which is more preferable.
- the drive capacitor unit of the present invention has a configuration in which a DC voltage is applied to an electrode pair, and the variable capacitor unit has a configuration in which a plurality of electrode pairs are connected in series and an AC voltage is applied to both ends thereof.
- the drive voltage control circuit is provided with a function of grasping the drive capacity of the drive capacitor unit based on the detected voltage, and controls the DC voltage applied to the drive capacitor unit so that the detected voltage approaches a desired value. .
- the positional relationship between the movable structure portion and the substrate and the setting accuracy of the drive capacity can be increased, and as a result, the capacitance accuracy of the variable capacitor portion can be increased.
- the drive voltage control circuit applies the drive capacity unit to the drive capacitor unit so as to correct the variation and variation even if there is variation in the spring force of each product and the variation in the positional relationship between the movable structure and the substrate due to self-activation.
- the DC voltage can be automatically controlled to increase the capacitance accuracy of the variable capacitor unit.
- FIG. 3 is a diagram illustrating a drive voltage control circuit of the variable capacitance device in FIG. 2. It is a figure explaining the drive voltage control circuit of the variable capacitance apparatus which concerns on the 2nd Embodiment of this invention. It is a figure explaining the structural example of the variable capacitance apparatus which concerns on the 3rd Embodiment of this invention.
- FIG. 2A is a plan view of the variable capacitance device 1.
- FIG. 2B is a side sectional view of the variable capacitance device 1.
- the variable capacitance device 1 includes a substrate 2, lower drive electrodes 3A, 3B, 4, a dielectric film 5, a beam portion 6, pad electrodes 7, 8A, 8B, 9A, 9B, resistance patterns 9C, 9D, and a drive voltage control circuit 11. Is provided.
- the substrate 2 is made of a rectangular glass substrate.
- the beam portion 6 has a rectangular flat plate shape in a plan view and an L shape in a side view, and the right end portion in the drawing serves as a support portion joined to the substrate 2, and the main portion is separated from the substrate 2. It is a movable structure part of the cantilever structure (spring structure) supported in a state.
- the beam portion 6 is made of a low resistance Si substrate (conductive material) having a resistivity of 0.01 ⁇ cm or less, and P (phosphorus), As (arsenic), B (boron) or the like is used as a dopant.
- the lower drive electrodes 3A and 3B are each L-shaped and formed on the upper surface of the substrate 2, and have long line-shaped end portions along the axial direction (lateral direction in the drawing) of the beam portion 6.
- the lower drive electrode 4 is formed in a U-shape on the upper surface of the substrate 2, and both the lower drive electrodes 3 ⁇ / b> A and 3 ⁇ / b> B are formed at both ends of the long line shape along the axial direction (lateral direction in the drawing) of the beam portion 6. Arrange the sides.
- the dielectric film 5 is made of tantalum pentoxide having a rectangular shape and a thickness of about 200 nm, and is laminated on the substrate 2 so as to cover the ends of the lower drive electrodes 3A and 3B and the both ends of the lower drive electrode 4.
- the lower drive electrode 3A is connected to an RF signal input terminal (or output terminal) via a pad electrode 8A
- the lower drive electrode 3B is connected to an RF signal output terminal (or input terminal) via a pad electrode 8B.
- the lower drive electrode 4 is connected to the DC voltage input terminal via the pad electrode 9A and the resistance pattern 9C.
- the beam portion 6 is connected to the ground via the pad electrodes 7 and 9B and the resistance pattern 9D.
- the resistance patterns 9C and 9D are designed to have a resistance of about 200 k ⁇ with a titanium oxide thin film having a thickness of about 5 nm.
- Both end portions of the lower drive electrode 4 are opposed to the beam portion 6 via the dielectric film 5 to constitute the drive capacitor portion (C1) of the present invention.
- a drive capacitor C ⁇ b> 1 is generated between both ends of the lower drive electrode 4 and the beam unit 6.
- the drive capacitor C1 deforms the beam portion 6 by electrostatic attraction and brings the beam portion 6 into contact with the dielectric film 5 from the tip. The higher the DC voltage, the greater the contact area.
- the lower drive electrodes 3A and 3B are opposed to the beam portion 6 via the dielectric film 5 to constitute the variable capacitor portion (C2) of the present invention.
- the variable capacitor unit is used in a circuit that handles radio frequencies of several hundred MHz to several GHz, and generates a variable capacitance C2 that varies depending on the contact area between the beam unit 6 and the dielectric film 5. Since there is a possibility that a high frequency signal leaks from the variable capacitor portion to the drive voltage control circuit 11 and the ground via the beam portion 6, the resistance patterns 9C and 9D are formed here for the purpose of blocking the leaked high frequency signal. .
- the structure of the drive capacitor section (C1) is a structure in which a signal (voltage) is directly applied between the electrode pair (the lower drive electrode 4 and the beam section 6) (hereinafter, this structure is referred to as an MIM structure). And).
- the variable capacitor portion (C2) has a structure in which two pairs of electrodes (lower drive electrode 3A and beam portion 6, lower drive electrode 3B and beam portion 6) are connected in series, and a signal (voltage) is applied. This is a structure (hereinafter, this structure is referred to as a MIMIM structure).
- the MIMIM structure has an electrostatic attraction per area as small as about 1/4 compared with the MIM structure, and is advantageous for suppressing deformation of the beam portion 6 due to self-actuation.
- the MIM structure has a larger electrostatic attraction per area than the MIMIM structure, which is advantageous in reducing the electrode area. Therefore, it is preferable to employ the MIM structure for the drive capacitor portion (C1) that requires a large electrostatic attraction and the MIMIM structure for the variable capacitor portion (C2) that needs to suppress the electrostatic attraction. Note that each of the drive capacitor unit (C1) and the variable capacitor unit (C2) may adopt either the MIM structure or the MIMIM structure.
- FIG. 3 is a diagram for explaining the circuit configuration of the drive voltage control circuit 11.
- the drive voltage control circuit 11 includes a drive voltage generation circuit 12, a capacitance detection AC signal source 13, an amplifier circuit 14, a rectifier circuit 15, and a comparator 16.
- the drive voltage generation circuit 12 is a direct current source of the present invention, and outputs a DC voltage to an alternating current interruption resistor R1 (about 100 k ⁇ ).
- the capacitance detection AC signal source 13 is an AC source according to the present invention, and outputs a capacitance detection AC signal of about 10 MHz to a DC cutoff capacitor C3 (about 100 pF).
- the output terminal of the capacitor C3 is connected to the output terminal of the resistor R1, and the capacitance detection AC signal is superimposed on the DC voltage.
- This superimposed signal is input to a parallel circuit composed of a DC bypass resistor R2 and a reference capacitor C4.
- a drive capacitor C1 of the variable capacitance device 1 is connected to the output terminal of the parallel circuit, and a capacitor circuit including a resistor R2, a reference capacitor C4, and a drive capacitor C1 is configured.
- the DC component of the superimposed signal is applied to the drive capacitor C1 via the DC bypass resistor R2, and deforms the beam portion 6 in the variable capacitance device 1 by electrostatic attraction.
- the AC component of the superimposed signal is voltage-distributed by the reference capacitor C4 and the drive capacitor C1, and is output to the DC blocking capacitor C5 from the connection point between the reference capacitor C4 and the drive capacitor C1 as an amplitude corresponding to the capacitance ratio between them. To do.
- An amplifying circuit 14 is connected to the output terminal of the DC blocking capacitor C5, and the amplifying circuit 14 amplifies the voltage level of the AC output from the voltage distribution point in the capacitor circuit to obtain the detection voltage of the present invention.
- a voltage follower having a very high input impedance is provided at the input portion of the amplifier circuit 14, and the AC output of the capacitor circuit is simply voltage-distributed by the reference capacitor C4 and the drive capacitor C1.
- the voltage level is The detection voltage amplified by the amplifier circuit 14 is rectified by the rectifier circuit 15.
- the DC voltage output from the rectifier circuit 15 is a voltage level that uniquely reflects the capacitance of the drive capacitor C1.
- the voltage level decreases as the drive capacity C1 increases.
- the comparator 16 receives an external input voltage for instructing a set value of the drive capacity, and also receives an output from the rectifier circuit 15.
- the comparator 16 compares the voltage levels of the two and outputs the low level or the high level. Output voltage.
- the detection voltage is at a voltage level larger than the external input voltage, that is, when the drive capacity C1 is smaller than the set value, the output of the comparator 16 becomes HIGH level, and conversely, the drive capacity C1 is greater than the set value. Is larger, the output of the comparator 16 becomes LOW level.
- the drive voltage generation circuit 12 increases or decreases the DC voltage output according to the output voltage of the comparator 16.
- the drive voltage control circuit 11 adjusts the drive capacitance C1 to the set value instructed by the external input voltage. By making the drive capacitance C1 equal to the set value, the deformation of the beam portion 6 in the variable capacitance device 1 is adjusted to be equal to a desired state, and the variable capacitance C2 is adjusted to the desired value.
- variable capacitance device of the present embodiment has the same structure as that of the first embodiment, and only the circuit configuration of the drive voltage control circuit is different.
- FIG. 4 is a diagram for explaining the circuit configuration of the drive voltage control circuit 21 of the variable capacitance device according to the present embodiment.
- symbol is attached
- the drive voltage control circuit 21 includes a drive voltage generation circuit 22, a capacitance detection AC signal source 13, an AC component operation amplification circuit 24, a switched capacitor detection circuit 25, and a comparator 16.
- the drive voltage generation circuit 22 includes a switched capacitor LPF circuit 22B and a charge pump circuit 22A, and outputs a DC voltage to the AC blocking resistor R1.
- the capacitance detection AC signal source 13 outputs a capacitance detection AC signal to the DC cutoff capacitor C3.
- the output terminal of the capacitor C3 is connected to the output terminal of the resistor R1, and the capacitance detection AC signal is superimposed on the DC voltage.
- This superimposed signal is output to a bridge circuit (capacitor circuit) including resistors R21 and R22, a reference capacitor C24 (about 10 pF), and a drive capacitor C1.
- Resistors R21 and R22 are connected in parallel to the input end of the superimposed signal in the bridge circuit.
- a driving capacitor C1 is connected to the resistor R21, and a reference capacitor C24 is connected to the resistor R22.
- the resistors R21 and R22 have the same resistance value.
- the voltage applied to the path of the resistor R21 and the driving capacitor C1 by the superimposed signal is voltage-distributed to the resistor R21 and the driving capacitor C1, and the voltage level at the connection point is an AC component operation amplifier circuit via the DC blocking capacitance C26. 24.
- the voltage applied to the path of the resistor R22 and the reference capacitor C24 by the superimposed signal is voltage-distributed to the resistor R22 and the reference capacitor C24, and the voltage level at the connection point is an AC component operation amplification circuit via the DC blocking capacitance C25. 24.
- the voltage levels of the two systems have amplitude ratios corresponding to the capacity ratio between the drive capacitor C1 and the reference capacitor C24, respectively.
- the AC component operation amplification circuit 24 amplifies and outputs the two differential voltage level signals. Therefore, the signal amplified by the AC component operation amplification circuit 24 becomes a detection voltage having an amplitude corresponding to the drive capacitor C1.
- the detected voltage amplified by the AC component operation amplification circuit 24 is phase-detected by the switched capacitor detection circuit 25.
- the switched capacitor detection circuit 25 uses the capacitance detection AC.
- the detection voltage amplified by the AC component operation amplifier circuit 24 is sampled by a timing pulse synchronized with the phase 0 ° of the signal source 13 or a timing pulse synchronized with the phase 180 °.
- the switched capacitor detection circuit 25 accumulates charges in the internal capacitor based on the sampled voltage and outputs an AC output corresponding to the amount of charges.
- the detected voltage amplified by the AC component operation amplification circuit 24 is detected by the above timing pulse because the voltage drop due to the resistance component in the bridge circuit and the voltage drop due to the capacitance component fluctuate with a 90 ° phase shift.
- the comparator 16 receives an external input voltage that indicates the set value of the drive capacity, and also receives the output of the switched capacitor detection circuit 25, and outputs an output voltage that switches between the LOW level and the HIGH level by comparing the two.
- the AC output of the switched capacitor detection circuit 25 is larger than the external input voltage, that is, when the drive capacity is smaller than the set value, the output of the comparator 16 becomes HIGH level, and conversely, the drive capacity is set.
- the output of the comparator 16 becomes LOW level.
- the charge pump circuit 22A of the drive voltage generation circuit 22 increases or decreases the amount of power stored in the internal capacitor according to the output level of the comparator 16, and increases or decreases the output voltage level.
- the switched capacitor LPF circuit 22B of the drive voltage generation circuit 22 outputs a DC voltage obtained by removing a certain frequency component from the output voltage level of the charge pump circuit 22A. Therefore, if the output voltage level of the comparator 16 is HIGH level, the DC voltage rises and adjustment is made to increase the drive capacity C1, and if the output voltage level of the comparator 16 is LOW level, the DC voltage And the adjustment is made in the direction of decreasing the driving capacity C1.
- the drive voltage control circuit 21 adjusts the drive capacitance C1 to the set value indicated by the external input voltage. By making the drive capacitance C1 equal to the set value, the deformation of the beam portion in the variable capacitance device is adjusted equally to a desired state, and the variable capacitance C2 is adjusted to the desired value.
- FIG. 5A is a plan view of the variable capacitance device 31.
- FIG. 5B is a side sectional view of the variable capacitance device 31.
- FIG. 5C is a front sectional view of the variable capacitance device 31.
- the variable capacitance device 1 includes a substrate 2, lower drive electrodes 3A, 3B, 4, upper drive electrodes 33, 34A, 34B, a dielectric film 5, a beam portion 36, pad electrodes 7, 8A, 8B, 9A, 9B, and a resistance pattern 9C. , 9D and a drive voltage control circuit 11.
- the beam portion 36 is made of a high resistance Si substrate (insulating material) having a resistivity of 10 k ⁇ cm or more.
- the upper drive electrodes 34A and 34B are provided opposite to both ends of the lower drive electrode 4, and are connected to the ground via the pad electrodes 7 and 9B and the resistance pattern 9D.
- the upper drive electrode 33 is spaced apart from the upper drive electrodes 34A and 34B.
- Both end portions of the lower drive electrode 4 are opposed to the upper drive electrodes 34A and 34B via the dielectric film 5 to constitute the drive capacitor portion (C1) of the present invention.
- the lower drive electrodes 3A and 3B are opposed to the upper drive electrode 33 via the dielectric film 5 to constitute the variable capacitor portion (C2) of the present invention.
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Abstract
Description
可変容量装置101は可動板102と基板103とを備える。可動板102は微細加工技術を用いて物理的に上下に動くことができるMEMSとして作製し、図示しないバネ構造を介して基板103に接続する。基板103と可動板102とには対向する電極対が二組形成され、各電極対は静電容量部105,106を構成する。静電容量部105は、駆動電圧を印加することで駆動容量が発生し、駆動電圧に応じて定まる静電引力が可動板102を基板103に引きつけ、静電引力とバネ構造のバネ力とがつりあう位置で可動板102は停止する。静電容量部106は、高周波信号が印加される信号ラインに挿入され、可動板102の停止位置に応じた静電容量の可変キャパシタとなる。このような構成の可変容量装置101は、誘電正接の小さい誘電体材料や低抵抗の導体材料を使用して全体設計を最適化することで、低損失の可変キャパシタとして利用できる。
この構成では、駆動電圧制御回路に、検出電圧に基づいて駆動容量部の駆動容量を把握する機能を設け、検出電圧が所望値に近づくように駆動容量部に印加するDC電圧を制御する。これにより、可動構造部と基板との位置関係および駆動容量の設定精度を高め、ひいては可変キャパシタ部の容量精度を高められる。すなわち、製品毎のバネ力のバラツキや、セルフアクチエーションによる可動構造部と基板との位置関係の変動があっても、バラツキや変動を補正するように駆動電圧制御回路が駆動容量部に印加するDC電圧を自動的に制御し、可変キャパシタ部の容量精度を高められる。
この構成では、直流源の出力するDC電圧を制御するため、DC電圧から駆動容量を把握することは困難である。そこで、交流源の出力する容量検出用のAC電圧を一定として出力することで、駆動容量部に流れるAC電流に基づく検出電圧から、駆動容量を把握することが可能になる。
本発明の第1の実施形態に係る可変容量装置の構成例について説明する。
次に、本発明の第2の実施形態に係る可変容量装置の構成例について説明する。なお、本実施形態の可変容量装置は第1の実施形態と同様の構造であり、駆動電圧制御回路の回路構成のみが相違する。
次に、本発明の第3の実施形態に係る可変容量装置の構成例について説明する。なお、本実施形態の駆動電圧制御回路の回路構成は第1の実施形態と同様であり、駆動容量部および可変キャパシタ部の構成のみが相違する。なお、上述の構成と同様な構成には同符号を付して説明を省く。
2…基板
3A,3B,4…下駆動電極
5…誘電体膜
6,36…梁部
7,8A,8B,9A,9B…パッド電極
9C,9D…抵抗パターン
11,21…駆動電圧制御回路
12,22…駆動電圧発生回路
13…容量検出用交流信号源
14,24…増幅回路
15…整流回路
16…比較器
C1…駆動容量
C2…可変キャパシタンス
C4,C24…参照容量
22A…チャージポンプ回路
22B…スイッチトキャパシタLPF回路
25…スイッチトキャパシタ検波回路
33,34A,34B…上駆動電極
Claims (10)
- 基板と、
バネ構造を介して前記基板に接続される可動構造部と、
DC電圧が印加されて生じる駆動容量に基づく静電引力を、前記可動構造部と前記基板との間に作用させる駆動容量部と、
RF信号が印加されて生じる静電容量が、前記可動構造部と前記基板との位置関係に応じて変化する可変キャパシタ部と、
前記駆動容量に応じて変化する検出電圧を検出し、その検出電圧が所望値に近づくように前記駆動容量部に印加するDC電圧を制御する駆動電圧制御回路と、を備える可変容量装置。 - 前記駆動電圧制御回路は、
前記駆動容量部にDC電圧を印加する直流源と、前記DC電圧に容量検出用のAC電圧を重畳する交流源と、を備え、
前記駆動容量部に流れるAC電流からの変換電圧に基づいて前記検出電圧を生成する、請求項1に記載の可変容量装置。 - 前記駆動電圧制御回路は、
既知の容量値の参照容量をさらに備え、
前記参照容量に流れるAC電流からの変換電圧と前記駆動容量部に流れるAC電流からの変換電圧とに基づいて前記検出電圧を生成する、請求項2に記載の可変容量装置。 - 前記駆動電圧制御回路は、前記参照容量および抵抗からなる直列回路と前記駆動容量部および抵抗からなる直列回路とを並列に接続し、各直列回路における接続点の電圧差分に基づいて前記検出電圧を生成する、請求項3に記載の可変容量装置。
- 前記駆動電圧制御回路は、前記参照容量と前記駆動容量部とを直列に接続し、接続点の電圧に基づいて前記検出電圧を生成する、請求項3に記載の可変容量装置。
- 前記駆動電圧制御回路は、前記検出電圧における前記駆動容量部による電圧降下分が最大となるタイミングで前記検出電圧をサンプリングする、請求項1~5のいずれかに記載の可変容量装置。
- 前記駆動電圧制御回路は、前記検出電圧のサンプリング値を外部入力電圧と比較して前記直流源の出力するDC電圧を増減させる請求項6に記載の可変容量装置。
- 前記可動構造部は導電性材料からなり、前記駆動容量部には信号カット用の抵抗を接続してなる、請求項1~7のいずれかに記載の可変容量装置。
- 前記可動構造部は絶縁性材料からなり、前記駆動容量部または前記可変キャパシタ部となる電極が表面に形成されてなる、請求項1~7のいずれかに記載の可変容量装置。
- 前記駆動容量部は電極対にDC電圧が印加される構成であり、
前記可変キャパシタ部は、複数の電極対を直列接続してその両端にAC電圧を印加する構成である、請求項1~9のいずれかに記載の可変容量装置。
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CN201080062592.XA CN102725808B (zh) | 2010-01-28 | 2010-12-22 | 可变电容装置 |
JP2011551711A JP5418607B2 (ja) | 2010-01-28 | 2010-12-22 | 可変容量装置 |
US13/547,252 US20120274141A1 (en) | 2010-01-28 | 2012-07-12 | Variable capacitance device |
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US9081264B2 (en) | 2012-12-31 | 2015-07-14 | Digitaloptics Corporation | Auto-focus camera module with MEMS capacitance estimator |
US9097748B2 (en) * | 2013-03-14 | 2015-08-04 | DigitalOptics Corporation MEMS | Continuous capacitance measurement for MEMS-actuated movement of an optical component within an auto-focus camera module |
US20140292354A1 (en) * | 2013-03-27 | 2014-10-02 | Texas Instruments Incorporated | Capacitive sensor |
JP6426164B2 (ja) | 2013-06-28 | 2018-11-21 | キャベンディッシュ・キネティックス・インコーポレイテッドCavendish Kinetics, Inc. | Memsデジタル可変キャパシタ(dvc)の処理中の応力制御 |
CN104776868B (zh) * | 2015-02-16 | 2017-04-12 | 纳米新能源(唐山)有限责任公司 | 自供能传感器 |
US10119998B2 (en) * | 2016-11-07 | 2018-11-06 | Fluke Corporation | Variable capacitance non-contact AC voltage measurement system |
US10352967B2 (en) | 2016-11-11 | 2019-07-16 | Fluke Corporation | Non-contact electrical parameter measurement systems |
EP3575262B1 (en) * | 2018-05-22 | 2021-04-14 | Murata Manufacturing Co., Ltd. | Reducing crosstalk in a mixed-signal multi-chip mems device package |
JP7183664B2 (ja) * | 2018-09-26 | 2022-12-06 | Tdk株式会社 | 電子部品 |
US11961684B1 (en) | 2023-08-02 | 2024-04-16 | King Faisal University | Energy storage in a minimized variable capacitance system using capacitor with distance-movable plates |
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US20120274141A1 (en) | 2012-11-01 |
CN102725808A (zh) | 2012-10-10 |
JPWO2011092980A1 (ja) | 2013-05-30 |
CN102725808B (zh) | 2016-01-20 |
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