Rotary resonant three-dimensional electric field sensor

A rotary resonant three-dimensional electric field sensor is disclosed. The rotary resonant three-dimensional electric field sensor includes: a substrate (1); an X-direction electric field measurement unit (4), a Y-direction electric field measurement unit (5), and a Z-direction electric field measurement unit (6), set on the substrate (1), each of which including: a sensing electrode (8, 10, 13) fixed on the substrate (1), and a shielding electrode (7, 9, 12) vibrating relatively to the sensing electrode (8, 10, 13); and at least one set of driving mechanical structures (11, 18), is configured to generate a driving force so as to cause the shielding electrode (7, 9) to vibrate relatively to a corresponding sensing electrode (8, 10, 13), and the vibration is transferred to the shielding is electrodes (7, 9, 12) of the other two electric field measurement units (4, 5, 6).

TECHNICAL FIELD

The present invention relates to sensor technology in the electronics industry, and more particularly, to a rotary resonant three-dimensional electric field sensor integrated on a single chip capable of measuring magnitudes of three components of an electric field intensity vector in an environment.

BACKGROUND

Measuring the electric field intensity can be applied in various industries, such as meteorology, aerospace, intelligent power grid, resource prospecting, industrial production, etc. Therefore, electric field sensors with low manufacturing costs and outstanding performance are desired.

Conventionally, an electric field sensor which employs a traditional mechanical structure is able to perform a three-dimensional measurement on electric field intensity. The manufacture of such a sensor has been developed and is of high accuracy. However, its bulky size makes it disadvantageous in application. In “A Small Three-Dimensional Electric Field Sensor” (Journal of Instrumentations and Meters,2006, 27(11): 1433-1436, Xing ZHANG, et al.), as a typical example of traditional mechanical sensors, a small three-dimensional electric field sensor is disclosed, which is 5 cm×3.2 cm in size, and weights 80 g.

As the micro-manufacturing technology develops, a micro-manufacturing based micro electric field sensor has been raised. It has a small volume, and is eligible for massive production, and hence, is a potential replacement of the electric field sensor having a traditional mechanical structure. Existing micro electric field sensor is able to perform one-dimensional electric field intensity measurement, and has already got high sensitivity. In “A High Sensitivity SOI Electric field Sensor with Novel Comb-Shaped Microelectrodes”(Transducers'11, Beijing, 2011, 1034-1037, Pengfei YANG, et al.), as a typical example of such micro electric field sensors, a micro electric field sensor is disclosed, which is 5 mm×5 mm in size, and has a resolution of 40 V/m.

However, during the process of implementing the present invention, the applicant discovers that: in some cases, it is not assured that a direction of electric field intensity is vertical to a surface of sensor, because the direction of the electric field intensity is unknown. And when the direction of the electric field intensity to be measured is not vertical to the surface of the sensor, significant measurement error will arise if the conventional micro electric field sensor is used.

SUMMARY OF THE INVENTION

a. Problems to be Solved

The present embodiment provides a rotary resonant three-dimensional electric field sensor, so as to simultaneously measure the magnitudes of the three components of the electric field vector.

b. Technical Solution

According to an aspect of the invention, a rotary resonant three-dimensional electric field sensor is provided. The rotary resonant three-dimensional electric field sensor includes: a substrate; an X-direction electric field measurement unit, a Y-direction electric field measurement unit, and a Z-direction electric field measurement unit provided on the substrate, each of which including: a sensing electrode fixed on the substrate, and a shielding electrode which is able to vibrate relative to the sensing electrode, wherein: the shielding electrode of the Z-direction electric field measurement unit is positioned above its corresponding sensing electrode, and configured to rotationally resonates relative to the corresponding sensing electrode; each of the shielding electrodes of the X-direction electric field measurement unit and the Y-direction electric field measurement unit is connected to the shielding electrode of the Z-direction electric field measurement unit by one terminal respectively, so as to rotationally resonate relative to their corresponding sensing electrodes; wherein the shielding electrode of at least one of the X-direction electric field measurement unit, the Y-direction electric field measurement unit, and the Z-direction electric field measurement unit is connected to an anchor point fixed on the substrate via a beam structure; and at least one set of driving mechanical structures, configured to generate a driving force along a rotary resonating direction for the shielding electrode of one of the X-direction electric field measurement unit and the Y-direction electric field measurement unit, so as to cause the shielding electrode vibrate relative to its corresponding sensing electrode, and cause vibration be transferred to the shielding electrodes of the other two electric field measurement units.

According to a further aspect of the invention, a rotary resonant three-dimensional electric field sensor is provided. The rotary resonant three-dimensional electric field sensor includes: a substrate; an X-direction electric field measurement unit and a Y-direction electric field measurement unit provided on the substrate, each of which including: a sensing electrode fixed on the substrate, and a shielding electrode which is able to vibrate relative to the sensing electrode, wherein: inside terminals of each the shielding electrodes of the X-direction electric field measurement unit and the Y-direction electric field measurement unit are connected together so as to rotationally resonate relative to their respective corresponding sensing electrodes, respectively; an outside terminal of the shielding electrode of at least one of the X-direction electric field measurement unit and the Y-direction electric field measurement unit is connected to an anchor point fixed on the substrate via a beam structure; and at least one set of driving mechanical structures, configured to generate a driving force along the rotary resonating direction for the shielding electrode of one of the X-direction electric field measurement unit and the Y-direction electric field measurement unit, so as to cause the shielding electrode vibrate relative to its corresponding sensing electrode, and cause vibration be transferred to the shielding electrode of the other electric field measurement unit.

c. Beneficial Effects

With the above solutions, the rotary resonant three-dimensional electric field sensor of the present embodiment at least has the advantages as follows.

1) The rotary resonant three-dimensional electric field sensor of the present embodiment integrates electric field measurement units in three directions, thus has a high integration level. Comparing with existing micro one-dimensional electric field sensors, when the electric field to be measured is not vertical to the sensor surface, the sensor of the present embodiment is able to achieve accurate measurement by measuring the magnitudes of the three components of the electric field vector simultaneously.
2) The rotary resonant three-dimensional electric field sensor of the present embodiment requires only one set of stimulating signals to drive the vibration of the electrodes of electric field measurement units in the three directions, which leads to less stimulating signals and less interferences to the electric field which is to be measured. The shielding electrodes of the respective electric field measurement units are connected together to ensure each shielding electrode vibrates uniformly, and hence each sensing electrode output signal has the same resonant frequency.
3) The X-direction, Y-direction electric field measurement unit of the rotary resonant three-dimensional electric field sensor of the present embodiment is respectively arranged in pairs, thus a differential structure is formed to reduce the interferences to the measurement and thereby improve measurement accuracy.
4) The Z-direction electric field measurement unit of the rotary resonant three-dimensional electric field sensor of the present embodiment is configured to rotationally resonate under the driving of other electric field measurement units, which leads to less driving electrodes, lower power consumption and smaller volume.
5) The rotary resonant three-dimensional electric field sensor of the present embodiment is manufactured by utilizing micro manufacturing technology, which is compatible with matured IC technology, and thereby facilitates massive, low cost production. Comparing with traditional three-dimensional electric field sensor, the rotary resonant three-dimensional electric field sensor is preferred for its smaller volume and lower power consumption, and applicable to portable devices.

THE DESCRIPTION OF EMBODIMENTS

In order to clarify the object, solution, and advantages of the present embodiment, the present embodiment is further described below in detail, by way of examples, with reference to the drawings.

It is understood that, in the drawings and following description, similar or like parts are referred to with like numbers. In the drawings, the shape and thickness of the embodiments is enlargeable, and could be identified with simplicity and convenience. Moreover, elements and embodiments not depicted or described in the drawings is of forms known by a skilled person in the art. Additionally, although this description may provide examples of parameters with specific values, it should be appreciated that, the parameters may be within acceptable error allowances or design limits, with their values similar to corresponding values, rather than being exactly equal to corresponding values.

The present embodiment provides a rotary resonant three-dimensional electric field sensor with electric field measurement units of three different dimensions integrated on a single chip. The rotary resonant three-dimensional electric field sensor may drive the vibration of the electrodes in the three electric field measurement units by loading only one set of stimulating signals, and three components of the electric field vector in the environment are measured by the three electric field measurement units sensing variations of an amount of electric charge. First, in order to facilitate understanding, elements of the rotary resonant three-dimensional electric field sensor according to the embodiment are listed below:1substrate2beam structure3,14anchor point4X-direction electric field measurement unit5Y-direction electric field measurement unit6Z-direction electric field measurement unit7,9,12shielding electrode8,10,13sensing electrode11,18driving electrode15anchor point16shielding electrode17V-shaped beam structure

In an exemplary embodiment, a rotary resonant three-dimensional electric field sensor is provided.FIG. 1is a structural diagram of a rotary resonant three-dimensional electric field sensor according to an embodiment of the present invention. As shown inFIG. 1, the rotary resonant three-dimensional electric field sensor according to the present embodiment may include: a substrate1, an X-direction electric field measurement units4, a Y-direction electric field measurement units5, a Z-direction electric field measurement unit6, and at least one set of driving mechanical structures. The X-direction electric field measurement units4, the Y-direction electric field measurement units5, and the Z-direction electric field measurement unit6are provided on the substrate1, for measuring X-direction, Y-direction and Z-direction components of an electric field vector respectively. Each of the driving mechanical structures is used to generate a driving force along the rotary resonating direction for the shielding electrodes of either the X-direction electric field measurement units or the Y-direction electric field measurement units. The shielding electrode of at least one of the X-direction electric field measurement units, the Y-direction electric field measurement units, and the Z-direction electric field measurement unit is connected to an anchor point fixed on the substrate via a beam structure.

Respectively described below in detail are various elements of the rotary resonant three-dimensional electric field sensor according to the present embodiment.

In the embodiment, the substrate1is, but not limited to, made of silicon wafer. Alternatively, the substrate1may be made of other materials, which possess a certain level of rigidity, and are not prone to deformation.

Referring toFIG. 1, the Z-direction electric field measurement unit6is positioned at the center (i.e. origin of coordinates) of the substrate1. The X-direction electric field measurement units and the Y-direction electric field measurement units are provided surrounding the Z-direction electric field measurement unit6, and are symmetrical with Z-axis. The X-direction electric field measurement units4are arranged along Y-axis, and the Y-direction electric field measurement units5are arranged along X-axis on substrate1.

Because the coordinate axes can be set as desired, an angular requirement is deemed to be satisfied as long as the symmetry axis of the X-direction electric field measurement units4and the Y-direction electric field measurement units5are spaced by 90 degree. Additionally, the X-direction electric field measurement units4and the Y-direction electric field measurement units5are interchangeable. For a pair of the X-direction electric field measurement units4or the Y-direction electric field measurement units5, which are symmetrically arranged with Z-axis, both of the electric field measurement units may output measurement signals simultaneously, and form a differential structure. This differential structure of electric field measurement units may reduce the impact of outside interference to the measurement, and improve the measurement accuracy.

Skilled persons in the art should appreciate that, a single X-direction electric field measurement unit4or a single Y-direction electric field measurement unit5may be used. Although the structural strength and measurement accuracy may be reduced in this case, the effect of simultaneously measuring three components of an electric field vector can be realized.

In the embodiment, each electric field measurement unit may include a shielding electrode, and a sensing electrode fixed on the substrate1. The shielding electrode of the Z-direction electric field measurement unit6is positioned above its corresponding sensing electrode. Each of the shielding electrodes of the X-direction electric field measurement units4and the Y-direction electric field measurement units5is connected to the shielding electrode7of the Z-direction electric field measurement unit6by one terminal and connected to an anchor point3fixed on the substrate1via a beam structure2by the other terminal.

Each of the driving mechanical structures is configured to generate a driving force along the rotary resonating direction for the shielding electrode of one of the X-direction electric field measurement units4and the Y-direction electric field measurement units5. Under the stimulation, the driving mechanical structures generate a periodical driving force for the shielding electrodes of their corresponding electric field measuring unit, enabling the shielding electrode to vibrate periodically relative to corresponding sensing electrode, and the periodical vibration of the shielding electrode is transferred to the Z-direction electric field measurement unit6connected and the shielding electrodes of other measurement units.

The beam structure2inFIG. 2Ais a snake-shaped beam. The shielding electrode of the X-direction electric field measurement unit4is connected to an anchor point3fixed on the substrate1via the snake-shaped beam, and the axis direction of the symmetry axis of beam structure2is perpendicularly arranged to the X-axis. The shielding electrode of the Y-direction electric field measurement unit5is connected to an anchor point3fixed on the substrate1via a beam structure2, and the axis direction of the symmetry axis of beam structure2is parallel with the X-axis. There are four beam structures4in total, and the end points3of the four beam structures2form the four vertexes of a square which is centered at the origin of coordinates.

Additionally, the shielding electrode7of Z-direction electric field measurement unit6may also connect to an anchor point3fixed on the substrate1via the beam structure2. In this case, the axis direction of the symmetry axis of beam structure2is 45 degree or other angle with respective to the X-axis, as shown inFIG. 2B. That is, the shielding electrode of at least one of the X-direction electric field measurement unit4, the Y-direction electric field measurement unit5, and the Z-direction electric field measurement unit6is connected to an anchor point3fixed on the substrate1via a beam structure2.

The beam structure2is elastic along the vibration direction of the shielding electrode of the electric field measurement unit connected to the beam structure2, with an equivalent rigidity determining an operation mode of the three dimensional electric field sensor, and the like. In addition to the snake-shaped beam, the beam structure2may be straight line-shaped, wave-shaped, zigzag-shaped, etc., and its material could be silicon, metal, alloy and the like.

FIG. 3is a structural diagram of a Z-direction electric field measurement unit6in the rotary resonant three-dimensional electric field sensor as illustrated inFIG. 1. Referring toFIG. 1andFIG. 3, the Z-direction electric field measurement unit6may include: a shielding electrode7and a sensing electrode8. The sensing electrode8is fixed on substrate1, and its top surface is parallel to the surface of substrate1. On the body part of the sensing electrode8, several openings are formed. This sensing electrode8is connected to a signal measurement circuit.

The shielding electrode7is located above the sensing electrode8. The top and bottom surfaces shielding electrode7are parallel to the surface of substrate1, and the axis direction is perpendicular to the surface of substrate1, There are also several openings formed on the body part of shielding electrode7, and these openings are arranged alternately with the openings on the sensing electrode8to be shielded from each other. An outside frame of the shielding electrode7is connected to the shielding electrodes of the X-direction electric field measurement units4and the Y-direction electric field measurement units5. The openings on the sensing electrode8and the shielding electrode7may be circle, square, fan-shaped, triangle, oval and the like.

Regarding the Z-direction electric field measurement unit6as illustrated inFIG. 3, its operation principle may be described in detail. When the three-dimensional electric field sensor is active, the shielding electrode7vibrates rotationally under the driving of a periodical force. With the relative position of the shielding electrode7and the sensing electrode8shown asFIG. 4A, the amount of sensing charges on the sensing electrode8is larger; and with the relative position of shielding electrode7and sensing electrode8shown asFIG. 4B, the amount of sensing charges on the sensing electrode8is smaller. The periodical vibration of the shielding electrode7relative to the sensing electrode8leads to a periodical variation of the amount of the sensing charges on the surface of the sensing electrode8, and thereby forms an alternating current. Ideally, the three-dimensional electric field sensor is operated at a linear area, and the current is proportional to the Z-direction component of the electric field to be measured. Thus the magnitude of the current may reflect the Z-direction component of the electric field to be measured, and the current is measurable using an appropriate measuring circuit.

As shown inFIG. 3,FIG. 4AandFIG. 4B, in the present embodiment, the number of Z-direction electric field measurement unit6is one, and a shielding electrode7and a sensing electrode8are included. The shielding electrode7has several fan-shaped openings which are evenly distributed along the circle, and the sensing electrode8also has several fan-shaped openings which are evenly distributed along the circle. A fan-shaped area called shielding structure is formed between two neighboring openings on the body of shielding electrode7, and a fan-shaped area called sensing structure is formed between two neighboring openings on the body of sensing electrode8. Accordingly, the shielding structure and the sensing structure are alternately arranged to be shielded from each other. In other preferred embodiments of the present invention, the number of Z-direction electric field measurement unit6is more than one, e.g. two. In this case, all shielding structures are divided into two groups, and each group is still evenly distributed along the circle. All sensing structures can be similarly divided into two groups, and each group is combined with a corresponding shielding structure according to the pattern as shown inFIG. 4AandFIG. 4B, thereby forming a complete Z-direction electric field measurement unit6. The configuration of the two Z-direction electric field measurement units6may form a differential structure, which could improve the measuring accuracy.

In addition to the above-mentioned structure of Z-direction electric field measurement unit6, the present embodiment provides other structure of Z-direction electric field measurement unit6.FIG. 5is a structural diagram of a second type of Z-direction electric field measurement unit in the rotary resonant three-dimensional electric field sensor according to an embodiment of the present invention. Referring toFIG. 5, Z-direction electric field measurement unit6may include a shielding electrode9and a sensing electrode10. The sensing electrode10is fixed on substrate1, and its top surface is parallel to the surface of substrate1. This sensing electrode10is electrically connected to an electrical input of a signal measuring circuit.

The sensing electrode10may include one or more spokes centered at the center of the sensor and extending along the radius direction; and comb-shaped structures, each of which is arranged along the angular direction on a spoke. The shape of the combs is a series of co-centered circular arcs, with a co-center coinciding with the origin of coordinates of the rotary resonant three-dimensional electric field sensor according to the embodiment.

The top and bottom surfaces of the shielding electrode9are parallel to the surface of substrate1, and the axis direction of the shielding electrode9is perpendicular to the surface of substrate1. The outside frame of the shielding electrode9is connected to the shielding electrodes of the X-direction electric field measurement units4and the Y-direction electric field measurement units5. One or more spokes is arranged radially on the inside of the circular frame of shielding electrode9. A comb-shaped structure is arranged on each spoke along the angular direction. The shape of the combs is a series of co-centered circular arcs, with a co-center coinciding with the origin of coordinates of the rotary resonant three-dimensional electric field sensor according to the embodiment. The comb-shaped structure of shielding electrode9and the comb-shaped structure of the above sensing electrode10are arranged alternately with each other.

Regarding the Z-direction electric field measurement unit6in the three-dimensional electric field sensor according to the embodiment of the present invention as illustrated inFIG. 5, when the three-dimensional electric field sensor is active, the shielding electrode9vibrates rotationally under the driving of a periodical force, and the relative position of the shielding electrode9and the sensing electrode10varies periodically, thereby the amount of the charges on the surface of the sensing electrode10varies periodically to form a alternating current. Ideally, the three-dimensional electric field sensor operates at the linear area, and the current is proportional to the Z-direction component of the electric field to be measured. Then the magnitude of the current may reflect the Z-direction component of the electric field to be measured, and the current is measurable using the appropriate signal measuring means.

In the present embodiment, the driving mechanical structures may be driven by electrostatic forces. Electric field measuring units connected to the electrostatically driving mechanical structures are described below. In the embodiment, the shielding electrodes of both X-direction electric field measurement units4and Y-direction electric field measurement units5are simultaneously driven by the electrostatic forces. It is noted that, although the X-direction electric field measurement units4and Y-direction electric field measurement units5are separately positioned, they are identical in structure. Therefore, only the Y-direction electric field measurement units5are described below for clarity.

FIG. 6is a structural diagram of a Y-direction electric field measurement unit5and a mechanical structure in the rotary resonant three-dimensional electric field sensor as illustrated inFIG. 1. As shown inFIG. 6, a Y-direction electric field measurement unit5may include a shielding electrode12and a sensing electrode13.

The shielding electrode12is a mirror-symmetrical comb-shaped structure, in which the shape of the comb is a series of co-centered circular arcs, with a corresponding co-center coinciding with the center of the sensor. One terminal of the shielding electrode12is connected to the shielding electrode7of Z-direction electric field measurement unit6, and the other terminal is connected to the beam structure2. According to the embodiment, in the shielding electrode12, a comb-shaped part in a near end along the radial direction to the center of Z-direction electric field measurement unit6is called the first part, and the comb-shaped part in a far end is called the second part.

The sensing electrode13fixed on the substrate1via an anchor point14, is a comb-shaped structure, and the length of its comb-shaped structure is shorter than the length of the comb-shaped structure of the shielding structure12. The shape of the comb is a series of co-centered circular arcs, with a corresponding co-center coinciding with the center of the sensor. The comb-shaped structure of the sensing electrode13and the first part of the comb-shaped structure of the shielding electrode12are arranged alternately, with a constant interval between the neighboring combs. A pair of sensing electrodes13is symmetrically arranged on both sides of the shielding electrode12, and electrically connects to the signal measuring circuit respectively. The top surfaces of both the shielding electrode12and the sensing electrode13are parallel to the surface of substrate1.

Additionally, in other embodiments of the present invention, a single sensing electrode13may provided at only one side of the shielding electrode12. In this case, the shielding electrode12only keeps the comb-shaped structure on the side where the single sensing electrode13is provided.

FIG. 7is a partial enlargement diagram of the Y-direction electric field measurement unit5and the mechanical structures as illustrated inFIG. 6. Referring toFIG. 7, the driving mechanical structures may include two sets of separate driving electrodes11which are symmetrically arranged on both sides of the shielding electrode12. The driving electrodes11are fixed on the substrate1via an anchor point15. The sensing electrode13is a comb-shaped structure, and the shape of the comb is a series of co-centered circular arcs, with a corresponding co-center coinciding with the center of the sensor. The driving electrodes11and the second part of the comb-shaped structure of the shielding electrode12are arranged alternately, with the consistent interval between the neighboring combs.

The operation principle of the Y-direction electric field measurement unit5and the driving electrodes11shown inFIG. 7is described below. When the sensor is active, the driving electrodes on both sides introduce two stimulating signals respectively. The signals have the same magnitudes and frequencies, but their phases differ by 180 degree. The stimulating signals generate a combined force along the angular direction for the shielding electrode12so that the shielding electrode12vibrates rotationally and periodically under the driving of this electrostatic force. When the relative position relationship of the shielding electrode12and the sensing electrode13is shown asFIG. 8A, the Y-direction electric field measurement unit5is in a first operation state: on a positive value side of the Y-axis, the amount of charges on the surface of the sensing electrode is larger, and on a negative value side of the Y-axis, the amount of charges on the surface of the sensing electrode is smaller. When the relative position relationship of the shielding electrode12and the sensing electrode13is shown asFIG. 8B, the Y-direction electric field measurement unit5is in a second operation state: on the positive value side of the Y-axis, the amount of charges on the surface of the sensing electrode is smaller, and on the negative value side of the Y-axis, the amount of charges on the surface of the sensing electrode is larger. The relative position relationship between the shielding electrode12and the sensing electrode13varies periodically, leading to a periodical variation of the amount of the charges on the surface of the sensing electrode13, and thereby forms a current. Ideally, the three-dimensional electric field sensor operates at the linear area, and the current is proportional to the Y-direction component of the electric field to be measured. The current is measurable using the appropriate signal measuring circuit. The operation principle of the X-direction electric field measurement unit4is the same as that of the Y-direction electric field measurement unit5, hence are not be repeated here for clarity.

Referring toFIG. 6, in the embodiment, the driving electrodes11are arranged on the outside of the sensing electrode13along the radial direction, and are symmetrically distributed in pairs on both sides of the shielding electrode12to enhance the driving force and the driving torque. However, in other embodiments of the present invention, the driving electrodes11may interchange their positions with the sensing electrodes13, and the driving electrodes11may be not arranged in pairs on both sides of the shielding electrode12, but rather on only one side of the shielding electrode12, as long as the effect of driving the shielding electrode can be realized.

Additionally, other driving manner may be employed in addition to the above-mentioned electrostatic driving manner, such as, thermally driving, electro-magnetic driving, piezoelectric driving, or shape memory alloy and the like. Regardless the driving electrodes employed, a general functionality shall be implemented so that the driving electrodes may provide the driving forces to drive the corresponding shielding electrodes in motion.

FIG. 9is diagram of a thermally driving mechanical structure in the rotary resonant three-dimensional electric field sensor according to an embodiment of the present invention. As shown inFIG. 9, two separated sets of thermally driving mechanical structures are symmetrically arranged on both sides of a shielding electrode16. Each set may include: two driving electrodes18, which are electrically connected to two inputs for inputting the driving signals respectively, and a V-shaped beam structure17, which is connected between the two driving electrodes18and the shielding electrode16and is made of thermal inflatable material. The driving electrodes18are fixed on substrate1, and are connected to the V-shape beam structure17, which in turn is connected to the shielding electrode16. The principle for driving the shielding electrode with the above-mentioned thermally driving mechanical structures is described as below. The driving mechanical structures on both sides of the shielding electrode16respectively load AC voltage signals, which are of the same magnitude and frequency but separated in phase by 180 degree. Under the alternating signals, the V-shaped beam structure17thermally inflates and contracts periodically so that thermal stress may drive the shielding electrode16to move back and forth.

The relative position of the shielding electrode16and the sensing electrode varies periodically, and thereby the amount of the charges on the surface of the sensing electrode varies periodically to form an alternating current. This current may reflect the intensity of Y-direction component of the electric field to be measured, and the current is measurable using appropriate signal measuring circuit. Preferably, two sets of driving mechanical structures are arranged on both sides of the shielding electrode16to enhance the driving force. It should be understood that, the present embodiment may also be implemented if there is only one set of driving mechanical structures or a plurality of sets of driving mechanical structures are arranged on the same side of shielding electrode16.

Additionally, it is noted that, in the present embodiment (referring also toFIG. 1), there is only one Z-direction electric field measurement unit6, and a pair of X-direction electric field measurement units4and a pair of Y-direction electric field measurement units5are symmetrically distributed on both sides of the Z-axis respectively. In other preferred embodiments of the invention, there may be two or more alternately positioned Z-direction electric field measurement units6, with their axial direction coinciding with Z-axis. A plurality of pairs of X-direction electric field measurement units4and a plurality of pairs of Y-direction electric field measurement units5may be symmetrically distributed on both sides of the Z-axis respectively, and each pair forms a differential structure. In these embodiments, within the half plane on the positive axis side of the X-axis, the X-direction electric field measurement units4are axisymmetrically arranged with the positive axis of the X-axis as a symmetry axis, and within the half plane on the negative axis side of the X-axis, the X-direction electric field measurement units4are axisymmetrically arranged with the negative axis of the X-axis as a symmetry axis. Within the half plane on the positive axis side of the Y-axis, the Y-direction electric field measurement units5are axisymmetrically arranged with the positive axis of the Y-axis as a symmetry axis, and within the half plane on the negative axis side of the Y-axis, the Y-direction electric field measurement units5are axisymmetrically arranged with the negative axis of the Y-axis as a symmetry axis.

Persons skilled in the art should understand that, X-direction electric field measurement units4, Y-direction electric field measurement units5and Z-direction electric field measurement units6may be made of materials which are chosen from silicon, metal, and alloys, etc. The manufacturing process of such measurement units could be electroplating, electroforming, silicon-surface manufacture technology, EFAB technology, and PolyMUMPs and MetalMUMPs technologies of MEMSCAP Company, etc. The relevant technologies are well known to the persons skilled in the art and will not be repeated herein.

The rotary resonant three-dimensional electric field sensor according to the present embodiment has been described in detail with reference to the drawings.

According to boundary conditions of Maxwell Equations, electric field vectors bend at the surface of the electric sensor. In practice, the X-direction electric field measurement unit4may simultaneously sense X-component, Y-component and Z-component of an electric field to be measured. That is, an output signal of the X-direction electric field measurement unit4may contain responses to the X-component, Y-component and Z-component of the electric field to be measured, and a certain quantitative relationship is presented among these three components to form the output signal of the X-direction electric field measurement unit4. Similar situation occurs for the Y-direction electric field measurement unit5. Therefore, the output of X-direction and Y-direction electric field measurement unit both contain a response to the Z-component of the electric field to be measured. The magnitude of the Z-component could be computed based on the quantitative relationship of these three parts of responses. In this case, the Z-direction electric field measurement unit may be omitted.

Based on the above theory, in another exemplary embodiment of the present invention, another rotary resonant three-dimensional electric field sensor is provided. As shown inFIG. 10, the rotary resonant three-dimensional electric field sensor according to the present embodiment may include: a substrate1, X-direction electric field measurement units4, Y-direction electric field measurement units5, and at least one set of driving mechanical structures. The X-direction electric field measurement units4and the Y-direction electric field measurement units5are positioned on the substrate, and each of them may include: a sensing electrode fixed on the substrate, and a shielding electrode which is able to vibrate relative to the sensing electrode. The inside terminals of the shielding electrodes of the X-direction electric field measurement units4and the Y-direction electric field measurement units5are connected together, and the shielding electrodes may rotationally resonate relative to their respective corresponding sensing electrodes, respectively. An outside terminal of the shielding electrode of at least one of the X-direction electric field measurement units4and the Y-direction electric field measurement units5is connected to an anchor point fixed on the substrate via a beam structure. At least one set of driving mechanical structures generates a driving force along the rotary resonating direction for the shielding electrode of one of the X-direction electric field measurement units4and the Y-direction electric field measurement units5, causing the shielding electrode vibrates relative to its corresponding sensing electrode, and causing the vibration be transferred to the shielding electrode of the other electric field measurement unit.

The rotary resonant three-dimensional electric field sensor according to the present embodiment may include one or more pairs of X-direction electric field measurement units4and one or more pairs of Y-direction electric field measurement units5, each pair of X-direction electric field measurement units4form a differential structure, and each pair of Y-direction electric field measurement units5form a differential structure.

Other structural features of the present embodiment is similar to relevant description of the above embodiment, thus will not be repeated. According to the above two embodiments, persons skilled in the art should clearly understand the rotary resonant three-dimensional electric field sensor according to the present embodiment.

Additionally, the definitions of the above elements are not limited to the specific structures or shapes mentioned in the embodiments, and persons skilled in the art may easily and familiarly replace them, for example:

(1) Anchor points3,14,15may be a structure of any shape used to fix and support effectively, and the anchor points may be made of materials which are conductive and no easily deformed, such as silicon, metal, alloy and the like. The anchor point15may be positioned right below driving electrode11or laterally to the driving electrode11, as long as it connects the comb of the driving electrode11and fix it to substrate1.
(2) The outside frames of the shielding electrodes7,8,9may be rectangular, circle, fan-shaped, oval and the like, and are not limited to the circle shape in the above embodiments.
(3) Tips of the comb-shaped structure of the shielding electrodes9,12, the sensing electrodes10,13and the driving electrode11may be rectangular, circle, T-shaped, stair-shaped and the like.
(4) The shape of the driving electrode18in the thermally driving mechanical structures could be rectangular, circle and the like.

From above, the present embodiment provides a rotary resonant three-dimensional electric field sensor, which may be manufactured utilizing micro-manufacturing technologies and is able to realize a three dimensional an measurement of an electric field. Even if the electric field to be measured is not vertical to the sensor surface, the sensor of the present embodiment is able to achieve accurate measurement of the electric field. Therefore, the present embodiment is widely applicable in various industries, such as meteorology, intelligent power grid, resource prospecting, etc.

The above embodiments further explain the object, technical solutions and benefits of the present embodiment. It should be understood that these contents are merely specific embodiments of the invention, thus are not to limit the invention. Any modification, equivalent substitution, or improvement to the contents should be included in the protection scope of the invention, as long as they do not depart from the spirits and principles of the invention.