CN115524544B - Piezoelectric-driven horizontal resonant micro electric field sensor and working method thereof - Google Patents
Piezoelectric-driven horizontal resonant micro electric field sensor and working method thereof Download PDFInfo
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Abstract
The invention relates to the field of electric field sensors, and particularly discloses a piezoelectric-driven horizontal resonant micro electric field sensor and a working method thereof, wherein an induction electrode is fixedly arranged; the shielding electrode is arranged on one side of the induction electrode in parallel; both sides of the shielding electrode are provided with piezoelectric driving structures; piezoelectric driving structure includes a supporting beam, first piezoelectric driving roof beam and second piezoelectric driving roof beam, it sets up in one side of shielding electrode to prop up fixed the setting of beam, first piezoelectric driving roof beam and second piezoelectric driving roof beam symmetric distribution are in a supporting beam both sides, the one end and the supporting beam of first piezoelectric driving roof beam are connected, the other end and the shielding electrode of first piezoelectric driving roof beam are connected, the one end and the supporting beam of second piezoelectric driving roof beam are connected, the other end and the shielding electrode of second piezoelectric driving roof beam are connected. The sensor is driven in a piezoelectric mode, and the working mode is a horizontal resonance mode, so that the problem that the piezoelectric driving mode in the prior art cannot be used for a horizontal resonance type electric field sensor is solved.
Description
Technical Field
The invention relates to the field of electric field sensors, in particular to a piezoelectric-driven horizontal resonance type miniature electric field sensor and a working method thereof.
Background
MEMS electric field sensors based on the charge sensing principle typically comprise a shielding electrode, a sensing electrode and a driving structure. Under the drive of the driving structure, the shielding electrode periodically shields the induction electrode, so that the induction charge on the induction electrode periodically changes. When the horizontal vibration type electric field sensor works, parallel relative vibration occurs between the shielding electrode and the induction electrode, and compared with a vertical vibration mode, the horizontal vibration type electric field sensor has the advantage of small air damping; the driving signal can be different from the frequency of the induction signal, and the interference of the driving signal to the induction signal is favorably reduced.
The existing horizontal vibration type miniature electric field sensor usually adopts a thermal driving mode or an electrostatic driving mode. The driving structure of the thermal driving is simple, but the response speed is slow; the fast response speed of electrostatic driving, but the high driving voltage (generally higher than 20 Vp-p) are required, and these defects prevent the integration application of the horizontal vibration type micro electric field sensor with the standard CMOS circuit or other electric quantity sensor. Therefore, it is important to develop a horizontal vibration type micro electric field sensor with high response speed, low driving voltage and low power consumption, and to improve the compatibility of the horizontal vibration type micro electric field sensor with a standard cmos integrated circuit and promote the integration and application thereof.
Disclosure of Invention
The present invention is directed to provide a piezoelectric-driven horizontal resonant micro electric field sensor and a method for operating the same, which solve the problem of the prior art that a piezoelectric driving method can be used only for a vertical resonant electric field sensor and not for a horizontal resonant electric field sensor; the micro electric field sensor provided by the invention has the characteristics of small mutual interference between a driving signal and an induction signal, high response speed, low driving voltage and low power consumption.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a piezoelectric-driven horizontal resonance type miniature electric field sensor comprises an induction electrode, a shielding electrode and a piezoelectric driving structure:
the induction electrode is fixedly arranged;
the shielding electrode is arranged on one side of the induction electrode in parallel;
the piezoelectric driving structures are arranged on two sides of the shielding electrode, the piezoelectric driving structures can drive the shielding electrode to vibrate, and the vibration direction of the shielding electrode is parallel to the induction electrode;
piezoelectric actuation structure includes a supporting beam, first piezoelectric actuation roof beam and second piezoelectric actuation roof beam, it sets up in one side of shielding electrode to prop up a supporting beam and fix, first piezoelectric actuation roof beam and second piezoelectric actuation roof beam's structure is the same, first piezoelectric actuation roof beam and second piezoelectric actuation roof beam symmetric distribution are in a supporting beam both sides, first piezoelectric actuation roof beam and second piezoelectric actuation roof beam all perpendicular with shielding electrode's direction of motion, the one end of first piezoelectric actuation roof beam is connected with a supporting beam, the other end of first piezoelectric actuation roof beam is connected with shielding electrode, the one end and the supporting beam of second piezoelectric actuation roof beam are connected, the other end and the shielding electrode of second piezoelectric actuation roof beam are connected.
Preferably, the first piezoelectric driving beam and the second piezoelectric driving beam respectively comprise a driving electrode group layer, a piezoelectric film, a lower driving electrode, an insulating layer and an elastic beam which are sequentially arranged along the thickness direction, the driving electrode group layer is parallel to the vibration plane of the shielding electrode, the driving electrode group layer comprises a first upper driving electrode group and a second upper driving electrode group, the first upper driving electrode group comprises two first upper driving electrodes arranged at the diagonal positions of one group of the piezoelectric film, the second upper driving electrode group comprises two second upper driving electrodes arranged at the other group of diagonal positions of the piezoelectric film, and the first upper driving electrodes and the second upper driving electrodes are the same in shape and are in a strip shape; the first upper driving electrodes of the first piezoelectric driving beams are connected in parallel, and the second upper driving electrodes of the second piezoelectric driving beams are connected in parallel.
Preferably, the induction electrodes comprise a first induction electrode group and a second induction electrode group, the first induction electrode group comprises a plurality of strip-shaped first induction electrodes, the strip-shaped first induction electrodes are connected in parallel, the second induction electrode group comprises a plurality of strip-shaped second induction electrodes, the strip-shaped second induction electrodes are connected in parallel, the first induction electrodes and the second induction electrodes are alternated, and the first induction electrodes and the second induction electrodes are alternated and arranged in parallel;
the shielding electrode comprises a plurality of strip-shaped shielding electrode strips, and a first grid strip and a second grid strip which are parallel to each other, wherein the plurality of strip-shaped shielding electrode strips are parallel to each other and arranged at intervals, two ends of each shielding electrode strip are respectively connected with the first grid strip and the second grid strip, the shielding electrode strips are perpendicular to the first grid strip and the second grid strip, two ends of the first grid strip and the second grid strip are respectively provided with a piezoelectric driving structure, one end of a first piezoelectric driving beam is connected with a supporting beam, the other end of the first piezoelectric driving beam is connected with the first grid strip, one end of a second piezoelectric driving beam is connected with the supporting beam, and the other end of the second piezoelectric driving beam is connected with the second grid strip;
the shielding electrode strip, the first induction electrode is parallel to the second induction electrode, the width of the shielding electrode strip, the width of the first induction electrode is the same as that of the second induction electrode, the length of the shielding electrode strip is not smaller than that of the first induction electrode, the length of the shielding electrode strip is not smaller than that of the second induction electrode, the shielding electrode strip can cover the first induction electrode or the second induction electrode completely, the gap between the adjacent shielding electrode strips is not smaller than the width of the shielding electrode strip, and the number of the shielding electrode strip, the first induction electrode and the second induction electrode is the same.
Preferably, when the piezoelectric-driven horizontal resonance type micro electric field sensor is in a non-working state, the shielding electrode strips are located right above the junction position of the adjacent first sensing electrode and the second sensing electrode.
Preferably, the first sensing electrode group is in a comb-tooth shape, the first sensing electrode group comprises a comb handle part and a comb-tooth part, and the comb handle part comprises a first strip-shaped connecting band; one end of each first induction electrode is connected with the first strip-shaped connecting band, each first induction electrode forms a comb tooth part of each first induction electrode group, and the distance between every two adjacent first induction electrodes is larger than the width of the corresponding second induction electrode.
Preferably, the second sensing electrode group is in a comb-tooth shape, the second sensing electrode group comprises a comb handle part and a comb-tooth part, and the comb handle part comprises a second strip-shaped connecting band; one end of each second induction electrode is connected with the corresponding second strip-shaped connecting band, each second induction electrode forms a comb tooth part of each second induction electrode group, and the distance between every two adjacent second induction electrodes is larger than the width of each first induction electrode.
Preferably, the piezoelectric-driven horizontal resonant miniature electric field sensor further comprises a substrate, the substrate is in a rectangular frame shape, a supporting layer is connected between a group of opposite sides of the substrate, the sensing electrode is arranged on the surface of the supporting layer, and the shielding electrode and the sensing electrode are positioned on the same side of the supporting layer; and the supporting beam of the piezoelectric driving structure is fixedly connected with the substrate.
The invention relates to a working method of a piezoelectric-driven horizontal resonance type micro electric field sensor, which comprises the following steps:
and applying alternating current driving voltage to all the first piezoelectric driving beams and the second piezoelectric driving beams to enable the shielding electrodes and the induction electrodes to generate periodic and parallel relative vibration, so that the charges on the induction electrodes generate periodic changes, and acquiring the electric field intensity of the space to be detected according to the periodic change condition of the charges on the induction electrodes.
Preferably, the first piezoelectric driving beam and the second piezoelectric driving beam respectively comprise a driving electrode group layer, a piezoelectric film, a lower driving electrode, an insulating layer and an elastic beam which are sequentially arranged along the thickness direction, the driving electrode group layer is parallel to the vibration plane of the shielding electrode, the driving electrode group layer comprises a first upper driving electrode group and a second upper driving electrode group, the first upper driving electrode group comprises two first upper driving electrodes arranged at the diagonal positions of one group of piezoelectric film, the second upper driving electrode group comprises two second upper driving electrodes arranged at the other group of diagonal positions of the piezoelectric film, and the first upper driving electrodes and the second upper driving electrodes are same in shape and are both strip-shaped; the first upper driving electrodes of the first piezoelectric driving beams are connected in parallel, and the second upper driving electrodes of the second piezoelectric driving beams are connected in parallel;
when alternating current driving voltage is applied to all the first piezoelectric driving beams and all the second piezoelectric driving beams, the alternating current driving voltage with the same amplitude and opposite polarity is applied to the first upper driving electrode group and the second upper driving electrode group of each of the first piezoelectric driving beams and the second piezoelectric driving beams, so that the first piezoelectric driving beams and the second piezoelectric driving beams are driven by d 31 The mode performs bending vibration parallel to the vibration plane of the shielding electrode to shieldPeriodic, parallel relative vibrations occur between the electrodes and the sensing electrodes.
The invention has the following beneficial effects:
in the piezoelectrically-driven horizontal resonance type micro electric field sensor, the two sides of the shielding electrode in the moving direction are respectively provided with the piezoelectric driving structure, the first piezoelectric driving beam and the second piezoelectric driving beam of the piezoelectric driving structure are of a cantilever structure, so that the shielding electrode and the sensing electrode can be driven to generate parallel relative vibration through the first piezoelectric driving beam and the second piezoelectric driving beam of the piezoelectric driving structure, and the piezoelectrically-driven horizontal resonance type micro electric field sensor has the characteristics of high response speed, small mutual interference between a driving signal and a sensing signal, low driving voltage (which can be as low as 1 Vp-p) and low power consumption due to piezoelectric driving.
The invention is described in further detail below with reference to the drawings and the detailed description.
Drawings
Fig. 1 is a schematic top view of a piezoelectric-driven horizontal resonant micro electric field sensor according to the present invention.
Fig. 2 is a schematic plan view of a shield electrode used in the embodiment of the present invention.
Fig. 3 is a schematic plan view of the first sensing electrode set, the second sensing electrode set and the supporting layer according to the embodiment of the invention.
Fig. 4 is a schematic diagram of a cross-sectional structure and driving signals along a line a-B in fig. 1, and ac voltages having the same amplitude and opposite polarities are applied to the first upper driving electrode group and the second upper driving electrode group.
Fig. 5 is a schematic diagram of a distributed excitation area of a piezoelectric drive beam in an embodiment of the invention.
Fig. 6 is a schematic cross-sectional structure and operation principle of fig. 1 along C-D when the shielding electrode is at the initial position according to the embodiment of the present invention.
Fig. 7 is a schematic diagram of the flexural vibration of the piezoelectric driving beam along the negative x-axis direction when the driving signal shown in fig. 4 is applied according to the embodiment of the present invention.
FIG. 8 is a schematic cross-sectional view taken along the line C-D in FIG. 1 and illustrating the operation of the shield electrode when vibrating along the negative x-axis direction in an embodiment of the present invention.
The main component structural symbols of the disclosed embodiment of the invention in the drawings are as follows:
1-a substrate; 2-1-a first support beam, 2-2-a second support beam; 3-1-a first piezoelectric driving beam, 3-2-a second piezoelectric driving beam; 4-a support layer; 5-shielding electrode, 5-1-shielding electrode bar, 5-2-1-first grid bar, 5-2-2-second grid bar; 6-a first induction electrode group, 6-1-a first induction electrode, and 6-2-a first strip-shaped connecting band; 7-a second induction electrode group, 7-1-a second induction electrode and 7-2-a second strip-shaped connecting band; 8-a first upper drive electrode group, 8-1-a first upper drive electrode; 9-a second upper drive electrode group, 9-1-a second upper drive electrode; 10-a piezoelectric film; 11-lower drive electrode; 12-an insulating layer; 13-a resilient beam; 14-a pre-amplifier circuit; 15-differential amplifier circuit.
The positive directions of the x axis, the y axis and the z axis marked in the drawing accord with the right-hand rule to form a space rectangular coordinate system which is only used for marking the relative space position and the vibration direction of each structure in the piezoelectric-driven horizontal resonance type micro electric field sensor disclosed by the invention.
In the description of the present specification, the terms "horizontal resonance", "horizontal vibration", "horizontal direction", "left", "right", and the like are used to refer to the piezoelectric driving beam or the shielding electrode vibrating in the positive or negative direction of the x-axis in the drawings; the terms "upper surface", "upper side", "directly above", and the like are used to refer to the positive z-axis direction in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention easier to understand, the present invention will be further described with reference to the accompanying drawings and the following embodiments.
Referring to fig. 1 to 8, the piezoelectric-driven horizontal resonance type micro electric field sensor of the present invention includes a substrate 1, the substrate 1 is shaped as a rectangular frame, the rectangular frame may be rectangular or square, for example, the orientation shown in fig. 1 is taken as an example, a support layer 4 is connected between the upper and lower pairs of opposite sides of the substrate 1, a first sensing electrode group 6 and a second sensing electrode group 7 are disposed on the support layer 4, the first sensing electrode group 6 includes a plurality of strip-shaped first sensing electrodes 6-1 connected in parallel, the second sensing electrode group 7 includes a plurality of strip-shaped second sensing electrodes 7-1 connected in parallel, as shown in fig. 3 in detail, the number of the first sensing electrodes 6-1 and the number of the second sensing electrodes 7-1 are both 12, the 12 first sensing electrodes 6-1 and the 12 second sensing electrodes 7-1 are alternately disposed in parallel on the surface of the support layer 4, and the first sensing electrodes 6-1 and the second sensing electrodes 7-1 are both parallel to the other pair of opposite sides (i.e., the left and right sides) of the substrate 1; specifically, referring to fig. 1 and 3, taking the orientation shown in fig. 3 as an example, the first and second sensing electrode groups 6 and 7 of the present invention are both in the shape of comb teeth, the first and second sensing electrode groups 6 and 7 both include comb handle portions and comb tooth portions, and the comb tooth portions of the first and second sensing electrode groups 6 and 7 are sequentially staggered in a plane and are not connected to each other. 12 strip-shaped first induction electrodes 6-1 are arranged at intervals, the upper ends of the first induction electrodes are connected with the first strip-shaped connecting band 6-2, the 12 first induction electrodes 6-1 form a comb tooth part of the first induction electrode group 6, and the distance between every two adjacent first induction electrodes 6-1 is larger than the width of the second induction electrode 7-1; the comb handle part of the second induction electrode group 7 comprises a second strip-shaped connecting belt 7-2; the 12 strip-shaped second induction electrodes 7-1 are arranged at intervals, the lower ends of the 12 strip-shaped second induction electrodes 7-1 are connected with the second strip-shaped connecting bands 7-2, the 12 second induction electrodes 7-1 form comb tooth parts of the second induction electrode groups 7, and the distance between every two adjacent second induction electrodes 7-1 is larger than the width of the first induction electrodes 6-1. The first induction electrode group 6 and the second induction electrode group 7 have the same shape and the same number of comb teeth, and can be completely overlapped after translation and rotation operations.
Referring to fig. 1 and 2, with reference to fig. 6 and 8, a shielding electrode 5 is arranged on the support layer 4 above the first sensing electrode group 6 and the second sensing electrode group 7, the shielding electrode 5 is suspended above the first sensing electrode group 6 and the second sensing electrode group 7, the shielding electrode 5 adopts a ladder-shaped grid structure and comprises a plurality of strip-shaped and mutually parallel shielding electrode bars 5-1 arranged at intervals, and a first grid bar 5-2-1 and a second grid bar 5-2-2 arranged at the upper end and the lower end (for example, the orientation shown in fig. 2) of the plurality of strip-shaped and mutually parallel shielding electrode bars 5-1, and the upper end and the lower end of the shielding electrode bar 5-1 are respectively and vertically connected with the first grid bar 5-2-1 and the second grid bar 5-2-2; the length of the shielding electrode strip 5-1 is not less than the length of the first sensing electrode 6-1 and the second sensing electrode 7-1, the shielding electrode strip 5-1 can be fully covered right above the first sensing electrode 6-1 or the second sensing electrode 7-1, the gap between the adjacent shielding electrode strips 5-1 is not less than the width of the shielding electrode strip 5-1, and the number of the shielding electrode strips 5-1, the number of the first sensing electrode 6-1 and the number of the second sensing electrode 7-1 are the same. Referring to fig. 1, the first and second bars 5-2-1 and 5-2-2 of the shielding electrode 5 are just covered directly above the first and second strip-shaped connection strips 6-2 and 7-2 of the first and second sensing electrode groups 6 and 7, respectively.
Referring to fig. 1, a supporting beam is arranged on a substrate 1 at a position opposite to the middle of the left end and the right end of a shielding electrode 5, and piezoelectric driving beams are symmetrically connected to the supporting beams, wherein the supporting beams on the left side and the right side are respectively marked as a first supporting beam 2-1 and a second supporting beam 2-2, the first piezoelectric driving beam 3-1 and a second piezoelectric driving beam 3-2 are symmetrically connected to the upper side and the lower side of the first supporting beam 2-1, the lower end of the first piezoelectric driving beam 3-1 is connected to the first supporting beam 2-1, the upper end of the first piezoelectric driving beam 3-1 is connected to the left end of a first grid 5-2-1, the upper end of the second piezoelectric driving beam 3-2 is connected to the first supporting beam 2-1, and the lower end of the second piezoelectric driving beam 3-2 is connected to the left end of a second grid 5-2-2;
the upper side and the lower side of the second supporting beam 2-2 are symmetrically connected with a first piezoelectric driving beam 3-1 and a second piezoelectric driving beam 3-2, the lower end of the first piezoelectric driving beam 3-1 is connected with the second supporting beam 2-2, and the upper end of the first piezoelectric driving beam 3-1 is connected with the right end of the first grid 5-2-1; the upper end of the second piezoelectric driving beam 3-2 is connected with the second supporting beam 2-2, and the lower end of the second piezoelectric driving beam 3-2 is connected with the right end of the second grid 5-2-2;
the first piezoelectric driving beam 3-1 and the second piezoelectric driving beam 3-2 are identical in structure and are parallel to the shielding electrode strip 5-1; referring to fig. 4, 5 and 7, the first and second piezoelectric driving beams 3-1 and 3-2 include, in the thickness direction thereof, a driving electrode group layer parallel to the plane of the shielding electrode 5, a piezoelectric film 10, a lower driving electrode 11, an insulating layer 12 and an elastic beam 13, which are sequentially disposed, and the driving electrode group layer includes a first upper driving electrode group 8 and a second upper driving electrode group 9, the first upper driving electrode group 8 and the second upper driving electrode group 9 are made of the same material, and a conductive material such as metal or heavily doped silicon may be used. Referring to fig. 5 and 7, the first upper driving electrode group 8 includes two first upper driving electrodes 8-1 disposed at one set of diagonal positions of the piezoelectric film 10, the second upper driving electrode group 9 includes two second upper driving electrodes 9-1 disposed at the other set of diagonal positions of the piezoelectric film 10, and the first upper driving electrodes 8-1 and the second upper driving electrodes 9-1 have the same shape and are both strip-shaped; all the first upper driving electrodes 8-1 are connected in parallel, all the second upper driving electrodes 9-1 are connected in parallel, and the first upper driving electrodes 8-1 and the second upper driving electrodes 9-1 are not connected with each other; taking the orientation shown in fig. 1 as an example, the first piezoelectric driving beam 3-1 and the second piezoelectric driving beam 3-2 are vertically symmetrical with respect to the first support beam 2-1, the two first piezoelectric driving beams 3-1 are laterally symmetrical, and the two second piezoelectric driving beams 3-2 are laterally symmetrical. Referring to fig. 7, the first upper driving electrode group 8, the second upper driving electrode group 9, and the lower driving electrode 11 apply driving signals to the second piezo-driven beam 3-2; the lower driving electrode 11 is grounded, and alternating current driving voltages with equal amplitude and opposite polarity are respectively applied to the first upper driving electrode group 8 and the second upper driving electrode group 9, so that the piezoelectric driving beam formed by the first piezoelectric driving beam 3-1 and the second piezoelectric driving beam 3-2 on the same side generates bending vibration in the horizontal direction.
Therefore, the first piezoelectric driving beam 3-1 and the second piezoelectric driving beam 3-2 generate bending vibration in the horizontal direction under the action of the alternating current driving signal, so as to drive the shielding electrode 5 to perform periodic reciprocating motion in the horizontal direction, so that induced currents related to the electric field intensity to be measured are generated on the first induction electrode group 6 and the second induction electrode group 7 respectively, and are output in a differential mode. Therefore, the first and second piezoelectric driving beams 3-1 and 3-2 can drive the shielding electrode 5 to vibrate along a plane parallel to the first and second sensing electrode groups 6 and 7, and the vibration direction is a direction perpendicular to the first and second sensing electrodes 6-1 and 7-1 (i.e., the left-right direction shown in fig. 1).
Referring to fig. 1, 6 and 8, in the above-mentioned solution of the present invention, the number of the shielding electrode strips 5-1, the first sensing electrodes 6-1 and the second sensing electrodes 7-1 is the same, and one shielding electrode strip 5-1 is disposed above each adjacent first sensing electrode 6-1 and second sensing electrode 7-1. Referring to fig. 8, when the piezoelectric-driven horizontal resonance type micro electric field sensor is in a non-operating state (i.e., when no driving signal is applied), the shielding electrode bar 5-1 corresponding to the upper side of the adjacent first sensing electrode 6-1 and second sensing electrode 7-1 is located right above the junction position of the adjacent first sensing electrode 6-1 and second sensing electrode 7-1, so as to perform an equivalent shielding effect on the first sensing electrode group 6 and second sensing electrode group 7, and the current output in the differential form is zero.
The driving mode of the piezoelectric-driven horizontal resonance type micro electric field sensor is piezoelectric driving, and the working mode is a horizontal resonance mode.
Referring to fig. 6, the widths of the comb teeth of the shielding electrode 5 (i.e., the shielding electrode strip 5-1), the comb teeth of the first sensing electrode group 6 (i.e., the first sensing electrode 6-1), and the comb teeth of the second sensing electrode group 7 (i.e., the second sensing electrode 7-1) are equal to each other and are w; the distance between adjacent comb teeth of the shielding electrode 5 (i.e. the distance between adjacent shielding electrode strips 5-1) is d 1 (ii) a The distance between the comb teeth of the adjacent first induction electrode group 6 and the heat release comb teeth of the second induction electrode group 7 is d 2 . Wherein, the above dimensional parameters conform to the following relations: d is a radical of 1 =w+2d 2 。
Referring to fig. 6 to 8, the piezoelectric driving micro electric field sensor of the present embodiment operates as follows:
in a non-working state, the first piezoelectric driving beam 3-1 and the second piezoelectric driving beam 3-2 are not bent, the shielding electrode 5 is located at an initial position shown in fig. 6, that is, the shielding electrode strip 5-1 is located right above the joint of the first sensing electrode 6-1 and the second sensing electrode 7-1, and each shielding electrode strip 5-1 plays an equivalent shielding role for the first sensing electrode 6-1 and the second sensing electrode 7-1 below the shielding electrode strip, as shown in fig. 6. Ideally, the amount of induced charge on the first and second sensing electrode groups 6 and 7 is equal.
Under the working state, alternating current driving voltages with the same amplitude and opposite polarities are applied to the first upper driving electrode group 8 and the second upper driving electrode group 9 on the first piezoelectric driving beam 3-1 and the second piezoelectric driving beam 3-2, piezoelectric films in different areas respectively extend or shorten along the y-axis direction due to the inverse piezoelectric effect, and then the piezoelectric driving beam formed by the first piezoelectric driving beam 3-1 and the second piezoelectric driving beam 3-2 on the same side is driven to rotate by the driving force d 31 The mode performs bending vibration in the horizontal direction (as shown in fig. 7), and carries the shielding electrode 5 to perform periodic horizontal vibration.
In one mode of operation of the electric field sensor of the present embodiment, the amplitude of the shield electrode 5 is (w) 2 +d 2 )/2. As shown in fig. 8, when the shielding electrode 5 moves leftward from the initial position, the shielding area of the first sensing electrode 6-1 increases, and the amount of induced charge on the first sensing electrode group 6 decreases until the vibration displacement becomes (w) 2 +d 2 ) At time/2, the amount of induced charge on the first set of sensing electrodes 6 is minimized; the shielding area for the second sensing electrode 7-1 is reduced so that the amount of the induced charge on the second sensing electrode group 7 is increased until the vibration displacement is (w) 2 +d 2 ) At this time, the amount of induced charge on the second sensing electrode group 7 reaches the maximum. On the contrary, when the shielding electrode 5 moves rightwards from the initial position, the shielding area of the first induction electrode 6-1 is reduced, and the induction charge quantity on the first induction electrode group 6 is increased; the shielding area for the second sensing electrode 7-2 is increased and the amount of the induced charge on the second sensing electrode group 7 is decreased. Along with the periodic horizontal vibration of the shielding electrode 5, the charges on the first induction electrode group 6 and the second induction electrode group 7 generate periodic change, the induced currents of the first induction electrode group 6 and the second induction electrode group 7 are output in a differential mode, and the electric field intensity of the space to be detected can be detected by detecting the magnitude of the output current. In this mode of operation, the output signal has the same frequency as the drive signal.
In another operation mode of the electric field sensor of the present embodiment, the amplitude of the shielding electrode 5 is (w) 2 +d 2 ) N times/2 (n is a positive integer), in this operating mode,the frequency of the induction signal is n times of that of the driving signal, so that the interference of the driving signal to the output signal can be reduced. For example: when n is 2, the shield electrode 5 is moved leftward from the initial position, and the vibration displacement is smaller than (w) 2 +d 2 ) When the voltage is more than 2, the amount of the induced charge on the first induced electrode group 6 is reduced, and the amount of the induced charge on the second induced electrode group 7 is increased; vibration displacement greater than (w) 2 +d 2 ) A/2 and less than (w) 2 +d 2 ) And then, the induction charge amount on the first induction electrode group 6 is increased, the induction charge amount on the second induction electrode group 7 is reduced, the frequency of the induction signal is 2 times of that of the driving signal, the output signal is filtered, and a signal with the same frequency as the driving signal is filtered, so that the interference of the driving signal on the output signal can be effectively reduced.
The piezoelectric driving horizontal resonance type miniature electric field sensor has the following characteristics:
(1) By arranging the distributed drive, the invention realizes the horizontal bending vibration of the piezoelectric drive beam and drives the shielding electrode 5 to horizontally vibrate, thereby solving the problem that the medium-voltage drive mode in the prior art cannot be used for a horizontal resonant electric field sensor; the piezoelectric drive is used as a driving mode of the horizontal resonance type electric field sensor, and the horizontal resonance type electric field sensor has the advantages of high response speed, good stability, low driving voltage (which can be as low as 1 Vp-p), low power consumption and the like.
(2) The shielding electrode 5 adopts a horizontal resonance working mode, the driving signal can be different from the frequency of the induction signal, and the interference of the driving signal on the induction signal can be reduced.
(3) The invention has compact structure and fully utilizes the area of the device by arranging two groups of sensitive structures, namely the first induction electrode group 6 and the second induction electrode group 7; the sensing signals of the two groups of sensing electrodes, namely the first sensing electrode group 6 and the second sensing electrode group 7, are output in a differential mode, so that the signal-to-noise ratio of the output signals is improved.
(4) The electric field sensor of the invention can be compatible with standard COMS integrated circuits and is easy to produce in batches.
In conclusion, the invention provides a feasible piezoelectric driving mode, and solves the problem that the piezoelectric driving mode in the prior art cannot be used for a horizontal resonance type electric field sensor; the method has the advantages of small mutual interference between the driving signals and the sensing signals, high response speed, good stability, low driving voltage, low power consumption and the like, can be compatible with a standard COMS integrated circuit, and is easy for batch production.
Claims (7)
1. A piezoelectric-driven horizontal resonance type miniature electric field sensor is characterized by comprising an induction electrode, a shielding electrode (5) and a piezoelectric driving structure:
the induction electrode is fixedly arranged;
the shielding electrode (5) is arranged on one side of the induction electrode in parallel;
the piezoelectric driving structures are arranged on two sides of the shielding electrode (5), the piezoelectric driving structures can drive the shielding electrode (5) to vibrate, and the vibration direction of the shielding electrode (5) is parallel to the induction electrode;
the piezoelectric driving structure comprises a supporting beam, a first piezoelectric driving beam (3-1) and a second piezoelectric driving beam (3-2), the supporting beam is fixedly arranged on one side of the shielding electrode (5), the first piezoelectric driving beam (3-1) and the second piezoelectric driving beam (3-2) are identical in structure, the first piezoelectric driving beam (3-1) and the second piezoelectric driving beam (3-2) are symmetrically distributed on two sides of the supporting beam, the first piezoelectric driving beam (3-1) and the second piezoelectric driving beam (3-2) are perpendicular to the moving direction of the shielding electrode (5), one end of the first piezoelectric driving beam (3-1) is connected with the supporting beam, the other end of the first piezoelectric driving beam (3-1) is connected with the shielding electrode (5), one end of the second piezoelectric driving beam (3-2) is connected with the supporting beam, and the other end of the second piezoelectric driving beam (3-2) is connected with the shielding electrode (5);
the first piezoelectric driving beam (3-1) and the second piezoelectric driving beam (3-2) respectively comprise a driving electrode group layer, a piezoelectric film (10), a lower driving electrode (11), an insulating layer (12) and an elastic beam (13) which are sequentially arranged along the thickness direction, the driving electrode group layer is parallel to the vibration plane of the shielding electrode (5), the driving electrode group layer comprises a first upper driving electrode group (8) and a second upper driving electrode group (9), the first upper driving electrode group (8) comprises two first upper driving electrodes (8-1) arranged at one group of diagonal positions of the piezoelectric film (10), the second upper driving electrode group (9) comprises two second upper driving electrodes (9-1) arranged at the other group of diagonal positions of the piezoelectric film (10), and the first upper driving electrode (8-1) and the second upper driving electrode (9-1) are identical in shape and are strip-shaped; the first upper driving electrodes (8-1) of the first piezoelectric driving beams (3-1) are connected in parallel, and the second upper driving electrodes (9-1) of the second piezoelectric driving beams (3-2) are connected in parallel;
the induction electrodes comprise a first induction electrode group (6) and a second induction electrode group (7), the first induction electrode group (6) comprises a plurality of strip-shaped first induction electrodes (6-1), the strip-shaped first induction electrodes (6-1) are connected in parallel, the second induction electrode group (7) comprises a plurality of strip-shaped second induction electrodes (7-1), the strip-shaped second induction electrodes (7-1) are connected in parallel, the first induction electrodes (6-1) and the second induction electrodes (7-1) are alternated, and the first induction electrodes (6-1) and the second induction electrodes (7-1) are arranged alternately and in parallel;
the shielding electrode (5) comprises a plurality of strip-shaped shielding electrode strips (5-1), a first grid strip (5-2-1) and a second grid strip (5-2-2) which are parallel to each other, the plurality of strip-shaped shielding electrode strips (5-1) are arranged in parallel and at intervals, two ends of each shielding electrode strip (5-1) are respectively connected with the first grid strip (5-2-1) and the second grid strip (5-2-2), the shielding electrode strips (5-1) are perpendicular to the first grid strip (5-2-1) and the second grid strip (5-2-2), two ends of the first grid strip (5-2-1) and the second grid strip (5-2-2) are respectively provided with a piezoelectric driving structure, one end of the first piezoelectric driving beam (3-1) is connected with the supporting beam, the other end of the first piezoelectric driving beam (3-1) is connected with the first grid strip (5-2-1), one end of the second piezoelectric driving beam (3-2) is connected with the supporting beam (3-2), and the other end of the second piezoelectric driving beam (3-2) is connected with the second grid strip (2-2);
the shielding electrode strip (5-1), the first induction electrode (6-1) and the second induction electrode (7-1) are parallel, the width of the shielding electrode strip (5-1), the width of the first induction electrode (6-1) and the width of the second induction electrode (7-1) are the same, the length of the shielding electrode strip (5-1) is not less than the length of the first induction electrode (6-1), the length of the shielding electrode strip (5-1) is not less than the length of the second induction electrode (7-1), the shielding electrode strip (5-1) can be fully covered right above the first induction electrode (6-1) or the second induction electrode (7-1), the gap between the adjacent shielding electrode strips (5-1) is not less than the width of the shielding electrode strip (5-1), and the number of the shielding electrode strip (5-1), the width of the first induction electrode (6-1) and the number of the second induction electrode (7-1) are the same.
2. A piezoelectric driven horizontal resonance type miniature electric field sensor according to claim 1, wherein when said piezoelectric driven horizontal resonance type miniature electric field sensor is in a non-operation state, the shielding electrode bar (5-1) is located right above the junction position of the adjacent first sensing electrode (6-1) and second sensing electrode (7-1).
3. The piezoelectric driving horizontal resonance type micro electric field sensor according to claim 1, wherein the shape of the first sensing electrode group (6) is comb-shaped, the first sensing electrode group (6) comprises a comb-handle part and a comb-tooth part, and the comb-handle part comprises a first strip-shaped connecting band (6-2); one end of each first induction electrode (6-1) is connected with the first strip-shaped connecting band (6-2), all the first induction electrodes (6-1) form comb tooth parts of the first induction electrode group (6), and the distance between every two adjacent first induction electrodes (6-1) is larger than the width of the second induction electrodes (7-1).
4. The piezoelectric driving horizontal resonance type micro electric field sensor according to claim 1, wherein the shape of the second sensing electrode group (7) is comb-shaped, the second sensing electrode group (7) comprises a comb-handle portion and a comb-tooth portion, and the comb-handle portion comprises a second strip-shaped connecting band (7-2); one end of each second induction electrode (7-1) is connected with the corresponding second strip-shaped connecting band (7-2), all the second induction electrodes (7-2) form comb tooth parts of the second induction electrode groups (7), and the distance between every two adjacent second induction electrodes (7-1) is larger than the width of the corresponding first induction electrode (6-1).
5. The piezoelectric driving horizontal resonance type micro electric field sensor according to any one of claims 1 to 4, further comprising a substrate (1), wherein the substrate (1) is a rectangular frame, a supporting layer (4) is connected between a set of opposite sides of the substrate (1), the sensing electrodes are disposed on the surface of the supporting layer (4), and the shielding electrodes (5) and the sensing electrodes are disposed on the same side of the supporting layer (4); the supporting beam of the piezoelectric driving structure is fixedly connected with the substrate (1).
6. The operating method of a piezoelectric-driven horizontal resonance type miniature electric field sensor according to claim 1, characterized by comprising the following steps:
and applying alternating current driving voltage to all the first piezoelectric driving beam (3-1) and the second piezoelectric driving beam (3-2) to enable the shielding electrode (5) and the induction electrode to generate periodic and parallel relative vibration, so that the electric charge on the induction electrode generates periodic change, and the electric field intensity of the space to be detected is acquired according to the periodic change condition of the electric charge on the induction electrode.
7. A method of operating a piezo-electrically driven horizontal resonance micro electric field sensor according to claim 6, wherein the first piezo-electrically driven beam (3-1) and the second piezo-electrically driven beam (3-2) each comprise, in the thickness direction, a layer of drive electrode set, which is parallel to the vibration plane of the shield electrode (5), a piezoelectric film (10), a lower drive electrode (11), an insulating layer (12) and an elastic beam (13), which are arranged in sequence, the layer of drive electrode set comprising a first upper drive electrode set (8) and a second upper drive electrode set (9), the first upper drive electrode set (8) comprising two first upper drive electrodes (8-1) arranged at one set of diagonal positions of the piezoelectric film (10), the second upper drive electrode set (9) comprising two second upper drive electrodes (9-1) arranged at the other set of diagonal positions of the piezoelectric film (10), the first upper drive electrodes (8-1) and the second upper drive electrodes (9-1) being of the same shape and being strip-like; the first upper driving electrodes (8-1) of the first piezoelectric driving beams (3-1) are connected in parallel, and the second upper driving electrodes (9-1) of the second piezoelectric driving beams (3-2) are connected in parallel;
when alternating current driving voltages are applied to all the first piezoelectric driving beams (3-1) and the second piezoelectric driving beams (3-2), alternating current driving voltages with the same amplitude and opposite polarities are applied to the first upper driving electrode group (8) and the second upper driving electrode group (9) of each of the first piezoelectric driving beam (3-1) and the second piezoelectric driving beam (3-2), so that the first piezoelectric driving beam (3-1) and the second piezoelectric driving beam (3-2) are driven by d 31 The mode performs bending vibration parallel to the vibration plane of the shield electrode (5), and causes periodic, parallel relative vibration between the shield electrode (5) and the induction electrode.
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