Reconfigurable broadband magneto-electro-mechanical antenna and array for through-the-earth communication

Abstract

The invention discloses a reconfigurable broadband magneto-electric mechanical antenna and array for through-the-earth communication, the reconfigurable broadband magneto-electric mechanical antenna comprises a radiation source, a permanent magnet, a variable inductor and a signal generator, the radiation source is composed of a magnetostrictive material I, a piezoelectric material, a magnetostrictive material II, a positive electrode and a negative electrode, the piezoelectric material is located between the first magnetostriction material and the second magnetostriction material. The positive electrode and the negative electrode are located on the upper side and the lower side of the piezoelectric material. The permanent magnets are positioned at two ends of the radiation source; the positive electrode and the negative electrode are connected with the signal generator to form a driving circuit; and the variable inductor is connected to the driving circuit, reconstructs the antenna by changing the inductance value of the variable inductor, and is used for expanding the bandwidth. According to the invention, the flat broadband of the magneto-electric mechanical antenna can be realized by adjusting the inductance value of the series variable inductor.

Description

Technical Field

[0001] The invention relates to the technical field of very low frequency wireless through-the-earth communication, and in particular to a reconfigurable very low frequency broadband magneto-electromechanical antenna. Background Art

[0002] With the rapid development of urban construction and modern industry, people's demand for deep resources below the surface is gradually increasing, which puts higher requirements on the communication capabilities between the surface and the underground. At present, the main communication method in the field of through-the-ground communication is wireless communication. Compared with the traditional wired communication method, the transmitting antenna and the receiving antenna do not need to build additional transmission cables. Therefore, wireless through-the-ground communication not only reduces costs, but also avoids the problem of communication interruption caused by damage to the cable laying.

[0003] A good wireless ground-penetrating communication system can not only improve work efficiency, but also serve as an emergency communication means to ensure the safety of workers when natural disasters occur underground. Due to the complexity of the ground medium, when the electromagnetic wave signal is propagating, it will be affected by the ground semiconductor medium and produce reflection and refraction problems at the junction of the rock layer, which will greatly attenuate the electromagnetic wave signal. The working frequency of ground-penetrating communication is in the megahertz range and lower. In order to increase the signal transmission power, large-size antennas are used. However, due to the narrow underground space, it is difficult to place a larger antenna size. Therefore, how to enhance the signal transmission power to further increase the communication distance without increasing the antenna size is also a problem that ground-penetrating communication needs to solve.

[0004] In recent years, with the deepening of the research on through-the-ground communication, more and more new through-the-ground technologies have been proposed, including mechanical antenna technology. Mechanical antenna is a new type of antenna based on the conversion of mechanical energy and electromagnetic energy. Since its radiation theory is different from that of traditional small electric antennas, it is expected to be miniaturized in through-the-ground communication. However, most of the current mechanical antennas are rotating mechanical antennas. The antenna has strong radiation capability, but it is difficult to generate a high modulation rate due to the limitation of motor power consumption. A research report by the United States National Coal Bureau (USBM) shows that for a mine with a depth of less than 300m, if the average conductivity of the upper covering layer is 0.001S / m, the optimal frequency range is 1kHz to 7kHz. The existing research on magneto-electric mechanical antennas is based on the study of resonance points, and the operating frequency is higher than 10kHz, which is not conducive to through-the-ground communication. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a reconfigurable broadband magneto-electromechanical antenna with a small size and an operating frequency range of 1 kHz to 7 kHz.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A reconfigurable broadband magneto-electromechanical antenna for through-the-ground communication comprises a radiation source, a permanent magnet, a variable inductor and a signal generator. The radiation source is composed of a first magnetostrictive material, a piezoelectric material, a second magnetostrictive material, a positive electrode and a negative electrode. The piezoelectric material is located between the first magnetostrictive material and the second magnetostrictive material, and the positive electrode and the negative electrode are located at the upper and lower sides of the piezoelectric material. The permanent magnet is located at both ends of the radiation source. The positive electrode and the negative electrode are connected to the signal generator to form a drive circuit. The variable inductor is connected to the drive circuit. By changing the inductance value of the variable inductor, the antenna is reconfigured to expand the bandwidth.

[0008] The invention provides a reconfigurable broadband magneto-electromechanical antenna. Alternating current is applied to both sides of the piezoelectric material to achieve resonance of the magneto-electromechanical antenna, causing the magnetic dipole in the magnetostrictive material to resonate, thereby forming a time-varying electromagnetic field. By adjusting the inductance value of the variable inductor, the resonance point of the magneto-electromechanical antenna is changed, thereby achieving the reconfiguration and broadbandization of the magneto-electromechanical antenna. This antenna avoids the practice of traditional electric antennas that load excitation voltage at the feeder port and generate oscillating electromagnetics inside the conductor. At the same time, this solution solves the problem of narrow bandwidth in mechanical antennas of the same type and unevenness within the band of the broadbandization method of magneto-electromechanical antennas with multiple array elements.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] 1. The signal transmission module in the device of the present invention can realize a time-varying electromagnetic field with the same frequency as the applied voltage.

[0011] 2. The magneto-electromechanical antenna in the device of the present invention does not need to consider the impedance matching problem. Amplitude modulation can be achieved by changing the amplitude of the applied voltage, and frequency modulation can be achieved by changing the frequency of the applied voltage; the resonance point of the magneto-electromechanical antenna can be changed by changing the inductance value of the series variable inductor, thus completing the reconfiguration and in-band flat broadband of the magneto-electromechanical antenna.

[0012] 3. The operating frequency of the present invention can achieve a frequency band below 10kHz, meeting the frequency requirements of through-the-ground communication (1-7kHz), and can be applied to through-the-ground communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 It is a schematic diagram of the structure of the magneto-electromechanical antenna of the present invention;

[0015] Figure 2 It is a schematic diagram of the clamp structure of the present invention;

[0016] Figure 3 yes Figure 2 A top view of

[0017] Figure 4 yes Figure 2 Side view of

[0018] Figure 5 This is a diagram of the magneto-electromechanical antenna model.

[0019] Figure 6 It is the magneto-electromechanical antenna admittance curve of the present invention under different antenna lengths.

[0020] Figure 7 This is the simulation result of broadbandization of multi-element magneto-electromechanical antenna.

[0021] Figure 8 This is a simulation result diagram of the reconfigurable broadband magneto-electromechanical antenna of the present invention.

[0022] Reference numerals:

[0023] 101-permanent magnet one; 102-permanent magnet two; 103-variable inductor; 104-magnetostrictive material; 105-piezoelectric material; 106-positive electrode; 107-negative electrode; 11-permanent magnet placement area one; 12-permanent magnet placement area two; 21-magnetomechanical antenna fixing area; 31-magnetomechanical antenna supporting area; 41-magnetostrictive material one; 42-piezoelectric material; 43-magnetostrictive material two; 44-permanent magnet one; 45-permanent magnet two; 46-positive electrode; 47-negative electrode. DETAILED DESCRIPTION

[0024] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0025] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0026] In the description of this application, unless otherwise clearly specified and limited, the terms "electrode", "clamp", "magnetostrictive material", "piezoelectric material", "variable inductor", etc. should be understood in a broad sense. For example, it can be a positive electrode plate or a negative electrode plate. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The present invention proposes a magneto-electromechanical antenna, see Figure 1-Figure 5 ,in Figure 1 and Figure 5 The same description refers to the same object, with an operating frequency range of 1kHz to 7kHz, including magnetostrictive material 1 41, magnetostrictive material 2 43, piezoelectric material 42, permanent magnet 1 44, permanent magnet 2 45, positive electrode 46, negative electrode 47 and a clamp. Magnetostrictive material 1 41 and magnetostrictive material 2 43 are respectively located on the upper and lower sides of piezoelectric material 42. Positive electrode 46 is located on the upper side of piezoelectric material 42, between magnetostrictive material 1 41 and piezoelectric material 42, and negative electrode 47 is located on the lower side of piezoelectric material 42, between magnetostrictive material 2 43 and piezoelectric material 42. Permanent magnet 1 44 and permanent magnet 2 45 are respectively located on the left and right sides of the radiation source, and the magnetization direction of the permanent magnet is consistent with the length direction of the magneto-electromechanical antenna. The clamp is used to fix one end of the mechanical antenna and clamp the magneto-electromechanical antenna.

[0028] The operating frequency of the magneto-electromechanical antenna of the present invention is near 5.6kHz, and the antenna size is 80mm×20mm×15mm. By applying an alternating voltage to the positive electrode and the negative electrode, the electric material generates deformation to drive the magnetostrictive material 1 and the magnetostrictive material 2. Due to the inverse magnetoelectric effect, the magneto-electromechanical antenna generates a time-varying electromagnetic field in space. By increasing the length of the magneto-electromechanical antenna, the operating frequency can be shifted to a lower direction.

[0029] like Figure 5 The figure shows the model diagram of the magneto-electromechanical antenna provided by the present invention, which includes a permanent magnet, a magnetostrictive material, a piezoelectric material and a variable inductor. The piezoelectric term and the magnetostrictive term in the magneto-electromechanical antenna satisfy the linear constitutive equation relationship shown in equations (1) and (2).

[0030]

[0031] in, and represents the stress and strain tensors; c H and c E are the mechanical stiffness tensors of the M phase and the P phase respectively; e H and e E are the stress constants of the M phase and the P phase, respectively. The superscript T indicates the transpose of the matrix; μ S is the strain-free permeability of the M phase; ε S is the strain-free dielectric constant of the P phase; H and E are the magnetic field and electric field intensity vectors; and are the magnetic flux density vector and the magnetic flux density vector.

[0032] The resonant frequency of the magneto-electromechanical antenna is:

[0033] fr =v a / (2L) (3)

[0034] Among them, v a The average acoustic velocity of the composite material; L is the length of the magneto-electromechanical antenna.

[0035] It can be seen from formula (3) that the resonant frequency of the magnetomechanical antenna is mainly affected by the volume ratio of the magnetostrictive phase and the piezoelectric phase and the antenna length. Therefore, we simulate and analyze the influence of the volume ratio of the magnetostrictive phase and the piezoelectric phase and the antenna length on the resonant frequency. By controlling the volume ratio of the magnetostrictive phase and the piezoelectric phase to 2:1 and changing the antenna length (50mm to 150mm), the magnetomechanical antenna admittance curve is as follows: Figure 6 The dimensions of the magneto-electromechanical antenna unit are: 120 mm long, 20 mm wide, and 15 mm thick. The resonant frequency is 5.6 kHz, which meets the 1-7 kHz frequency requirement for through-the-ground communication.

[0036] According to the above analysis, once the antenna structure is fixed, its working resonant frequency will also be fixed. Figure 6 It can be seen that the unique working mechanism of the MEMA antenna makes its bandwidth extremely narrow, which makes the MEMA antenna very unfavorable for through-the-ground communication under high transmission rate conditions. In order to broaden the working frequency band of MEMA, existing literature mainly expands the overall bandwidth by connecting unit structures with different resonant frequencies in parallel. The results are shown in Figure 2. Figure 7 However, this method leads to serious unevenness in the band. In order to solve the problem caused by the broadbandization of multiple array elements, the present invention proposes the following Figure 5 The magneto-electromechanical antenna structure shown in the figure, the series resonance point in the magneto-electromechanical antenna equivalent circuit model can be expressed as Where L m is the equivalent inductance, C m is an equivalent capacitor, so the present invention realizes the reconfiguration of the magneto-electromechanical antenna by connecting a variable inductor in series, thereby expanding the bandwidth.

[0037] Figure 5 The permanent magnet module shown is placed in Figure 2 The two permanent magnet placement areas shown in the figure require a suitable bias magnetic field to achieve optimal performance due to the magnetostrictive loop of the magnetostrictive material. Figure 2 The middle permanent magnet placement area is located on the movable part and can move left and right along the fixed part. The size of the time-varying bias magnetic field is changed by changing the distance between the permanent magnet and the magneto-electromechanical antenna.

[0038] It should be noted that the placement of the permanent magnet requires that the magnetization direction be consistent with the length direction of the magneto-electromechanical antenna.

[0039] Figure 5 The magnetostrictive material, piezoelectric material and electrodes in the magneto-electromechanical antenna are assembled and placed on the left side. Figure 3The magnetomechanical antenna fixing area shown is a mounting cavity with a rectangular shape and a right end hanging in the air. To improve the safety of the magnetomechanical antenna, the following is added at the bottom of the magnetomechanical antenna: Figure 3 Support block shown.

[0040] like Figure 8 As shown in the figure, it is a simulation result diagram of the present invention under different inductance conditions. For the magneto-electromechanical antenna designed in this article, after the inductance is connected in series, the bandwidth changes from 21Hz (0 millihenry (mH) without inductance) to 85Hz (1.5 millihenry (mH)), which is increased by 4.05 times. And the resonance point also changes with the different inductance values. Therefore, the present invention can obtain an antenna unit with small frequency difference and multiple resonance points without changing the antenna structure by connecting a variable inductor in series, thereby obtaining a broadband magneto-electromechanical antenna with good flatness.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not cause the corresponding technical solutions to essentially deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A reconfigurable broadband magneto-electromechanical antenna for through-the-earth communication, characterized in that: The invention comprises a radiation source, a permanent magnet, a variable inductor and a signal generator. The radiation source is composed of a first magnetostrictive material, a piezoelectric material, a second magnetostrictive material, a positive electrode and a negative electrode. The piezoelectric material is located between the first magnetostrictive material and the second magnetostrictive material, and the positive electrode and the negative electrode are located at the upper and lower sides of the piezoelectric material. The permanent magnet is located at both ends of the radiation source. The positive electrode and the negative electrode are connected to the signal generator to form a drive circuit. The variable inductor is connected to the drive circuit. By changing the inductance value of the variable inductor, the antenna is reconstructed to expand the bandwidth.

2. The reconfigurable broadband magneto-electromechanical antenna for through-the-earth communication according to claim 1, characterized in that: The positive electrode and the negative electrode are located on both sides of the piezoelectric material in a high-low direction, and the positive electrode and the negative electrode are fixed on the piezoelectric material by epoxy resin glue.

3. The reconfigurable broadband magneto-electromechanical antenna for through-the-earth communication according to claim 1, characterized in that: The first magnetostrictive material is fixed to the positive electrode by epoxy resin glue, and the second magnetostrictive material is fixed to the negative electrode by epoxy resin glue.

4. The reconfigurable broadband magneto-electromechanical antenna for through-the-earth communication according to claim 1, characterized in that: It also includes a fixture; the radiation source and the permanent magnet are fixed on the fixture.

5. The reconfigurable broadband magneto-electromechanical antenna for through-the-earth communication according to claim 4, characterized in that: The fixture includes a permanent magnet placement area 1, a permanent magnet placement area 2, a magneto-electromechanical antenna fixing area and a magneto-electromechanical antenna supporting area; the permanent magnets at both ends are respectively located on the permanent magnet placement area 1 and the permanent magnet placement area 2, and the permanent magnet placement area can be moved left and right to adjust the size of the bias magnetic field; the radiation source is fixed on the magneto-electromechanical antenna fixing area and supported by the magneto-electromechanical antenna supporting area.

6. The reconfigurable broadband magneto-electromechanical antenna for through-the-earth communication according to claim 5, characterized in that: A supporting block is arranged in the supporting area of ​​the magneto-electromechanical antenna.

7. The reconfigurable broadband magneto-electromechanical antenna for through-the-earth communication according to claim 5, characterized in that: The magneto-electromechanical antenna fixing area is a mounting cavity.

8. The reconfigurable broadband magneto-electromechanical antenna for through-the-earth communication according to claim 5, characterized in that: The clamp comprises a fixed part and a movable part, wherein the movable part is arranged on both sides of the fixed part and can move along the length direction of the fixed part; the permanent magnet placement area 1 and the permanent magnet placement area 2 are respectively located on one movable part.

9. The reconfigurable broadband magneto-electromechanical antenna for through-the-earth communication according to claim 8, characterized in that: A guide groove is arranged on the fixed part, and the movable part is connected in the guide groove and can move along the guide groove.

10. A reconfigurable broadband magneto-electromechanical antenna array for through-the-earth communication, characterized in that: The array unit is a reconfigurable broadband magneto-electromechanical antenna for through-the-earth communication as described in any one of claims 1-9.

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