An ultra-low frequency magnetoelectric antenna based on a cantilever beam structure

Abstract

The purpose of this invention is to provide an ultra-low frequency magnetoelectric antenna based on a cantilever beam structure. This antenna innovatively combines a cantilever beam design with the energy conversion of electrical energy to mechanical energy to magnetic energy. Combined with the vibration characteristic of the cantilever beam structure, where the resonant frequency is inversely proportional to the square of its length, the antenna volume can be effectively reduced and the resonant frequency lowered. Simultaneously, by using a permanent magnet to attract the sample end, it is equivalent to adding a mass block and providing an external magnetic field at the end, which further reduces the resonant frequency and increases the magnetoelectric coefficient. The magnetoelectric antenna of this invention can operate at an ultra-low frequency of 61.4 Hz. Furthermore, due to the higher magnetoelectric coupling coefficient and lower wavenumber, the magnetoelectric antenna has a stronger radiation capability for the same distance.

Description

Technical Field

[0001] This invention belongs to the field of magnetoelectric antenna technology, specifically relating to an ultra-low frequency magnetoelectric antenna based on a cantilever beam structure. Background Technology

[0002] With the rapid development of wireless communication systems, the demand for antennas in smartphones, radio frequency identification systems, and radar is increasing. Currently, antennas are mainly divided into traditional high-frequency antennas and low-frequency antennas. However, the high-frequency signals generated by traditional high-frequency antennas have a low skin depth in complex electromagnetic environments such as seawater, soil, and rocks. This increases the attenuation and loss of the signal during transmission, making it unable to meet the communication needs of underwater and underground environments. Low-frequency antennas, on the other hand, have advantages such as low operating frequency, strong penetration, and the ability to propagate over long distances in seawater and underground, and have attracted widespread attention from researchers.

[0003] Traditional small electric antennas are much smaller than the theoretical wavelength, and their radiation efficiency is extremely limited. If you want to radiate signals in the low-frequency range, the size must be about one-tenth of the wavelength, which is too large for practical applications. In order to achieve miniaturization of low-frequency antennas, magneto-mechanical antennas have gradually been developed. Magnetoelectric antennas (Dong C, Wang X, Lin H, et al. A Portable Very Low Frequency (VLF) Communication System Based on Acoustically Actuated Magnetoelectric Antennas[J]. IEEE Antennas and Wireless Propagation Letters, 2020, PP(99):1-1.) use piezoelectric materials and magnetostrictive materials to form a magneto-electric composite material. Its magneto-electric effect can generate radiation. Electrical energy is converted into mechanical energy through the piezoelectric layer, and mechanical energy is converted into magnetic energy through the magnetostrictive layer, thereby realizing the radiation of electromagnetic waves. Magnetoelectric antennas use magnetic dipole moment vibration. The magnetic dipole moment oscillation is generated at their electromechanical resonance, which can eliminate the antenna size limitation related to the wavelength of electromagnetic waves. Very low frequency (VLF) antennas, which utilize magnetoelectric properties, typically have a resonant frequency around 30 kHz, which is insufficient for many applications. Therefore, achieving operation at even lower frequencies has become a new research direction.

[0004] The resonant frequency of a cantilever beam structure (Xing Z, Li JF, D. Viehland, et al. Giant magnetoelectric effect in Pb(Zr,Ti)O3-bimorph / NdFeB laminate device[J]. Applied Physics Letters, 2008) is inversely proportional to the square of the antenna size. Devices with lengths in the centimeter range can achieve resonant frequencies of several hundred hertz. The specific formula is as follows:

[0005]

[0006] Where l is the sample length. The average compliance coefficient. t represents the average mass density of the magnetoelectric heterojunction. P t M β1 represents the thickness of the piezoelectric layer and the magnetostrictive layer, respectively, and β1 represents the first-order transverse bending resonant mode.

[0007] How to design a magneto-electro-mechanical antenna based on a cantilever beam structure, so as to further reduce the antenna's operating frequency and improve its radiation capability, has become an urgent problem to be solved. Summary of the Invention

[0008] In view of the problems existing in the background technology, the purpose of this invention is to provide an ultra-low frequency magnetoelectric antenna based on a cantilever beam structure. This antenna innovatively combines a cantilever beam design with a magnetoelectric antenna, enabling the magnetoelectric antenna of this invention to operate at an ultra-low operating frequency of 61.4Hz, while also having stronger radiation capability.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] An ultra-low frequency magnetoelectric antenna based on a cantilever beam structure includes a piezoelectric material layer, a magnetostrictive material layer, a permanent magnet, and a clamping part;

[0011] An upper electrode is disposed on the upper surface of the piezoelectric material layer, and the upper electrode is flush with one side of the piezoelectric material. A lower electrode is disposed on the lower surface, and the lower electrode layer extends from the other side of the piezoelectric material to the upper surface. The lower electrode and the upper electrode do not contact each other.

[0012] A magnetostrictive material layer is disposed on the surface of the lower electrode, and the length of the magnetostrictive material layer is greater than that of the piezoelectric material layer. The magnetostrictive material layer and the piezoelectric material layer are aligned on the side of the upper material that is flush with the piezoelectric material.

[0013] The clamping part is used to clamp only the portion of the magnetostrictive material layer that is longer than the piezoelectric material layer; a permanent magnet is provided on the aligned side of the magnetostrictive material layer and the piezoelectric material layer. The permanent magnet includes two permanent magnet units, one of which is disposed on the surface of the upper electrode and the other of which is disposed on the lower surface of the magnetostrictive material layer.

[0014] Furthermore, the length of the magnetostrictive material layer is 0.5-5 mm longer than the length of the piezoelectric material layer.

[0015] Furthermore, on the upper surface of the piezoelectric material layer, the distance between the upper electrode and the lower electrode is 2-10 mm; the length of the lower electrode extending out of the other side of the piezoelectric material is 2-10 mm.

[0016] Furthermore, the thickness of the magnetostrictive layer is 2-10 mm, and the length of the magnetostrictive layer is 20-60 mm.

[0017] Furthermore, the thickness of the piezoelectric material layer is 2-10 mm.

[0018] Furthermore, the material of the piezoelectric material layer is a piezoelectric ceramic material or a piezoelectric single crystal material. The piezoelectric ceramic material is one of PZT-43, PZT-5H, and PZT-8, and the piezoelectric single crystal material is one of PZNPT or PMNPT.

[0019] Furthermore, the magnetostrictive layer material is one of Metglas2605, Terfenol-D, NiFe2O4, and FeGa alloy.

[0020] Furthermore, the permanent magnet material layer is made of either ferrite or neodymium iron boron.

[0021] Furthermore, when an alternating magnetic field is applied, the ultra-low frequency magnetoelectric antenna functions as a receiving antenna; when an external power supply is applied through the upper and lower electrodes, the ultra-low frequency magnetoelectric antenna functions as a transmitting antenna.

[0022] The mechanism of this invention is as follows: Traditional low-frequency antennas suffer from large size, high resonant frequency, and low radiation efficiency. This invention's magneto-electric composite structure utilizes the energy conversion from electrical energy to mechanical energy to magnetic energy, combined with the vibration characteristic of a cantilever beam structure where the resonant frequency is inversely proportional to the square of its length. This effectively reduces the antenna size and lowers the resonant frequency. Simultaneously, by using a permanent magnet to attract the sample end, it is equivalent to adding a mass block and providing an external magnetic field at the end, further reducing the resonant frequency and increasing the magnetoelectric coefficient. Moreover, because the antenna operates at a lower frequency (wavenumber), the magneto-electric mechanical antenna has a stronger radiation capability for the same distance.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0024] The ultra-low frequency magnetoelectric antenna based on a cantilever beam structure designed in this invention has a positive magnetoelectric voltage coupling coefficient α. DME Its resistance is 73.5 V / (cm·Oe), its resonant frequency is 62.6 Hz, and its inverse magnetoelectric coupling coefficient α cme The magnetic flux density is 3.31E-07s / m, the resonant frequency is 61.4Hz, and a higher excitation voltage can be added to the piezoelectric layer. The magnetic flux density of the ultra-low frequency antenna increases with the increase of the excitation voltage. When the voltage is 20V, the magnetic flux density at 1000m can be fitted to be 6.13E-18T. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the ultra-low frequency magnetoelectric antenna based on a cantilever beam structure according to the present invention.

[0026] Figure 2 This is a schematic diagram of the piezoelectric material layer in the ultra-low frequency magnetoelectric antenna of the present invention.

[0027] Figure 3 This is a schematic diagram illustrating the working principle of the inverse magnetoelectric effect of the ultra-low frequency magnetoelectric antenna of this invention.

[0028] Figure 4 This is a diagram showing the positive magnetoelectric coupling coefficient of the ultra-low frequency magnetoelectric antenna of this invention.

[0029] Figure 5 This is a diagram showing the inverse magnetoelectric coupling coefficient of the ultra-low frequency magnetoelectric antenna of the present invention.

[0030] Figure 6 This is a diagram showing the radiated magnetic induction intensity of the ultra-low frequency magnetoelectric antenna of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0032] A schematic diagram of an ultra-low frequency magnetoelectric antenna based on a cantilever beam structure is shown below. Figure 1 As shown, it includes a piezoelectric material layer, a magnetostrictive material layer, a permanent magnet, and a clamping part;

[0033] A schematic diagram of the structure of the piezoelectric material layer is shown below. Figure 2 As shown, an upper electrode is provided on the upper surface, which is flush with one side of the piezoelectric material. A lower electrode is provided on the lower surface, and the lower electrode layer extends from the other side of the piezoelectric material to the upper surface. The lower electrode and the upper electrode do not contact each other.

[0034] A magnetostrictive material layer is disposed on the surface of the lower electrode, and the length of the magnetostrictive material layer is greater than that of the piezoelectric material layer. The magnetostrictive material layer and the piezoelectric material layer are aligned on the side of the upper material that is flush with the piezoelectric material.

[0035] The clamping part is used to clamp only the portion of the magnetostrictive material layer that is longer than the piezoelectric material layer; a permanent magnet is provided on the aligned side of the magnetostrictive material layer and the piezoelectric material layer. The permanent magnet includes two permanent magnet units, one of which is disposed on the surface of the upper electrode and the other of which is disposed on the lower surface of the magnetostrictive material layer.

[0036] The cantilever beam structure requires clamping on both the left and right sides, and clamping the piezoelectric layer can easily cause it to break. Therefore, this invention designs the magnetostrictive material layer to be longer than the piezoelectric material layer, so that the clamping part only clamps one side of the magnetostrictive material layer. This can effectively protect the piezoelectric layer, prevent it from breaking under pressure, and effectively improve the sample life. At the same time, it avoids the problem that the welded wires of the flanged electrode formed when the lower electrode extends to the upper surface of the piezoelectric material layer will protrude and cannot be clamped. The other side is clamped by the adsorption of two permanent magnet units.

[0037] In the positive magnetoelectric voltage effect, the permanent magnet cantilever beam magnetoelectric antenna generates voltage in two ways: one is that under an applied alternating magnetic field, the magnetostrictive layer vibrates due to the magnetostrictive effect, and through interface coupling, the piezoelectric layer vibrates and generates an induced voltage through the piezoelectric effect; the other is that when the permanent magnet is subjected to an alternating magnetic field generated by a Helmholtz coil, it will vibrate, which will drive the piezoelectric layer to vibrate. The piezoelectric layer generates induced charges due to the piezoelectric effect, thereby generating a voltage. The combination of these two methods makes the positive magnetoelectric voltage coefficient of this structure relatively large, which can receive electromagnetic wave signals to a greater extent.

[0038] In the inverse magnetoelectric effect, the permanent magnet cantilever beam magnetoelectric antenna generates a magnetic field in two ways: Firstly, under an applied voltage, the piezoelectric layer vibrates due to the inverse piezoelectric effect, and through interface coupling, the magnetostrictive layer vibrates and generates an induced magnetic field through the inverse magnetostrictive effect. Secondly, the permanent magnet is adsorbed onto the magnetoelectric heterojunction and vibrates along with both the magnetoelectric and piezoelectric layers. Its magnetization direction is consistent with that of the magnetostrictive layer, both along the thickness direction. When vibration occurs, the magnetic field direction of the permanent magnet forms a certain angle with the length direction of the clamping end, generating a thickness-direction magnetic field component that increases the overall magnetic field, thereby improving the inverse piezoelectric coupling coefficient. Its working principle is as follows: Figure 3 As shown. Therefore, the magnetoelectric coefficient of the magnetoelectric antenna can be increased by vibrating the permanent magnet, thereby improving the antenna's radiation efficiency.

[0039] Example 1

[0040] A method for fabricating an ultra-low frequency magnetoelectric antenna based on a cantilever beam structure, specifically including the following steps:

[0041] Step 1. Fix the magnetostrictive FeGa alloy material on the sample loading stage of the cutting machine, load the corundum sheet, start the cutting machine, set the speed to 80, hold the mechanical handle to make the FeGa and corundum sheet make intermittent contact to prevent the shaft from getting stuck and the blade from being damaged. Cut to 42mm in length. After cutting, turn off the instrument and remove the sample.

[0042] Step 2. Grind the machined layer on the surface of the cut FeGa alloy sheet with 400#, 1000#, 1200# and 3000# sandpaper in sequence; after grinding, clean it with alcohol and deionized water in a high-power ultrasonic cleaner for 10 minutes each.

[0043] Step 3. Polish the magnetostrictive material using a UNIPOL-802 automatic precision grinding and polishing machine. During polishing, FeGa is attached to the carrier plate with double-sided tape. Then, the polishing pad is moistened, and the carrier plate is placed on the polishing pad. The polishing pad used is a black frosted leather polishing pad with a diameter of Φ200mm. Turn on the polishing machine and set the speed to 240. Polish for 6-8 hours. During the polishing process, add an appropriate amount of 80nm particle size SiO2 polishing slurry. After polishing is completed, remove the sample.

[0044] Step 4. Place the FeGa and alcohol solution in the same beaker, and then place the beaker in a cleaning tank. Place an ultrasonic generator at the bottom of the tank, select an oscillation frequency of 30KHz, and an oscillation time of 5 minutes. Then, ultrasonically clean with deionized water and dry with nitrogen gas after cleaning.

[0045] Step 5. Prepare epoxy resin adhesive: The epoxy resin curing agents used are West System 105 (liquid A) and 206 (liquid B). Use a dropper to draw 5ml of liquid A, wipe off any excess adhesive from the dropper head, and then draw 1ml of liquid B. Mix liquid A and liquid B at a volume ratio of 5:1. After mixing evenly, let it stand for 10 minutes.

[0046] Step 6. Select a PZT material with dimensions of 40mm in length, 6mm in width, and 0.5mm in height as the piezoelectric material layer, and deposit the upper and lower silver electrodes on its surface by sputtering.

[0047] Step 7. Bond the piezoelectric material layer to the magnetostrictive material FeGa with dimensions of 42mm in length, 6mm in width, and 0.5mm in height using epoxy resin. Apply the mixed epoxy resin evenly to the polished FeGa and bond it to PZT. Press the sample firmly during bonding and remove excess epoxy resin with a clean toothpick. In the experiment, care should be taken to keep the epoxy resin layer as thin as possible.

[0048] Step 8. Place the bonded sample from Step 7 into a vacuum chamber and allow it to cure at room temperature for 48 hours to minimize air bubbles in the epoxy resin during bonding, thereby improving stress transfer between the two materials.

[0049] Step 9. After curing is complete, weld the 0.2mm copper wire to the pre-reserved flange electrode of the piezoelectric layer;

[0050] Step 10. Use a clamp to fix the magnetostrictive layer. The clamping part should only clamp the extra 2mm on the left side of the magnetostrictive layer. When clamping, it should be tightened as much as possible to avoid shaking of the sample. Then, a permanent magnet is adsorbed on the right side of the magnetostrictive layer. The permanent magnet unit is a cylinder with a radius of 5mm and a height of 5mm. The required very low frequency magnetoelectric antenna can be prepared.

[0051] Since the magnetoelectric effect is generated by the interaction between the piezoelectric layer and the magnetostrictive layer, the extra part of the magnetostrictive layer cannot couple with the piezoelectric layer. In order to ensure as much coupling as possible and keep the piezoelectric material layer and the magnetostrictive layer of the same length as possible, the extra length of the magnetostrictive layer in this invention is relatively short, at 2mm, so that the magnetostrictive layer can be magnetically-mechanically-electrically coupled with the piezoelectric layer to a greater extent.

[0052] Figure 4 and Figure 5 The figures show the positive and negative magnetoelectric coupling coefficients of the ultra-low frequency magnetoelectric antenna according to Embodiment 1 of the present invention. As can be seen from the figures, the positive magnetoelectric voltage coupling coefficient α of the ultra-low frequency magnetoelectric antenna... DME Its voltage is 73.5 V / (cm·Oe), and its resonant frequency is 62.6 Hz; its inverse magnetoelectric coupling coefficient α cme The value is 3.31E-07s / m, and the resonant frequency is 61.4Hz.

[0053] The ultra-low frequency magnetoelectric antenna was tested under excitation voltages of 5V, 10V, and 20V. The variation of its experimental magnetic flux density with distance was measured, and the long-distance magnetic flux density was fitted based on the experimental results. Figure 6 As shown in the figure, the magnetic flux density of the ultra-low frequency antenna increases with the increase of the excitation voltage. When the voltage is 20V, the magnetic flux density at 1000m can be fitted as 6.13E-18T.

[0054] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. An ultra-low frequency magnetoelectric antenna based on a cantilever beam structure, characterized in that, It includes a piezoelectric material layer, a magnetostrictive material layer, a permanent magnet, and a clamping part; An upper electrode is disposed on the upper surface of the piezoelectric material layer, and the upper electrode is flush with one side of the piezoelectric material. A lower electrode is disposed on the lower surface, and the lower electrode layer extends from the other side of the piezoelectric material to the upper surface. The lower electrode and the upper electrode do not contact each other. A magnetostrictive material layer is disposed on the surface of the lower electrode, and the length of the magnetostrictive material layer is greater than that of the piezoelectric material layer. The magnetostrictive material layer and the piezoelectric material layer are aligned on the side of the upper material that is flush with the piezoelectric material. The clamping part is used to clamp only the portion of the magnetostrictive material layer that is longer than the piezoelectric material layer; a permanent magnet is provided on the aligned side of the magnetostrictive material layer and the piezoelectric material layer. The permanent magnet includes two permanent magnet units, one permanent magnet unit is provided on the surface of the upper electrode, and the other permanent magnet unit is provided on the lower surface of the magnetostrictive material layer. When an alternating magnetic field is applied, the ultra-low frequency magnetoelectric antenna acts as a receiving antenna; when an external power supply is applied through the upper and lower electrodes, the ultra-low frequency magnetoelectric antenna acts as a transmitting antenna.

2. The ultra-low frequency magnetoelectric antenna based on a cantilever beam structure as described in claim 1, characterized in that, The length of the magnetostrictive material layer is 0.5-5 mm longer than that of the piezoelectric material layer.

3. The ultra-low frequency magnetoelectric antenna based on a cantilever beam structure as described in claim 1, characterized in that, On the upper surface of the piezoelectric material layer, the distance between the upper electrode and the lower electrode is 2-10 mm; the lower electrode extends 2-10 mm beyond the other side of the piezoelectric material.

4. The ultra-low frequency magnetoelectric antenna based on a cantilever beam structure as described in claim 1, characterized in that, The thickness of the magnetostrictive layer is 2-10 mm, and the length of the magnetostrictive layer is 20-60 mm.

5. The ultra-low frequency magnetoelectric antenna based on a cantilever beam structure as described in claim 1, characterized in that, The thickness of the piezoelectric material layer is 2-10 mm.

6. The ultra-low frequency magnetoelectric antenna based on a cantilever beam structure as described in claim 1, characterized in that, The piezoelectric material layer is made of either piezoelectric ceramic material or piezoelectric single crystal material.

7. The ultra-low frequency magnetoelectric antenna based on a cantilever beam structure as described in claim 6, characterized in that, The piezoelectric ceramic material is one of PZT-43, PZT-5H, and PZT-8, and the piezoelectric single crystal material is one of PZNPT or PMNPT.

8. The ultra-low frequency magnetoelectric antenna based on a cantilever beam structure as described in claim 1, characterized in that, The magnetostrictive layer material is one of Metglas2605, Terfenol-D, NiFe2O4, and FeGa alloy.

9. The ultra-low frequency magnetoelectric antenna based on a cantilever beam structure as described in claim 1, characterized in that, The permanent magnet material layer is made of either ferrite or neodymium iron boron.

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