A very low frequency magnetoelectric antenna array with multi-field driven positive feedback

Abstract

A multi-field-driven positive feedback very low frequency magnetoelectric antenna array. The magnetoelectric antenna is composed of multiple strong hysteresis voltage magnetic layer / anisotropic high magnetic permeability piezomagnetic thin film / piezoelectric layer unit arrays, a grid-shaped substrate, and a magnetically shielded permanent magnet unit. On the one hand, the elastic standing wave generated by the piezoelectric array in the elastic substrate and the magnetic field convergence effect of the anisotropic high magnetic permeability piezomagnetic thin strip are used to realize the strong elastic field / magnetic field coupling characteristics between array units and drive the magnetic moment oscillation of the piezomagnetic thin strip, achieving the non-linear growth of the emission field strength with the number of units, overcoming the defects of single magnetoelectric antennas and weak magnetic moment energy regulation by a single elastic field, and significantly improving the magnetic field emission efficiency. On the other hand, the positive feedback magnetic field excitation mechanism between the magnetoelectric emission antenna and the magnetically shielded permanent magnet is used to break through the bottleneck of the restriction of the high quality factor on the bandwidth of the magnetoelectric antenna, realizing the functions of wide bandwidth and high emission efficiency.

Description

Technical Field

[0001] The present invention relates to a novel very low frequency antenna in special environments such as underground or underwater, and particularly to a multi-field-driven positive feedback very low frequency magnetoelectric antenna array with high transmission efficiency and large bandwidth. Background Art

[0002] Radio frequency communication technologies (such as Bluetooth and 5G, etc.) are widely used in daily life, but they will have serious path losses in high-conductivity environments such as underground or underwater. In contrast, very low frequency (3 kHz to 30 kHz) communication systems are more suitable for underground or underwater environments due to their larger skin depths. However, in order to achieve a sufficiently large radiation efficiency, traditional very low frequency electric antennas will cause problems of huge antenna size and serious power consumption, which severely limits the miniaturization and portability of the antennas. Compared with traditional electric antennas, mechanical antennas that have emerged in recent years can achieve low-frequency communication with extremely small volumes. Currently, low-frequency mechanical antennas mainly include rotating permanent magnet antennas driven by external motors and magnetoelectric antennas with self-resonant piezoelectric layers. Among them, magnetoelectric antennas mainly utilize the magnetic moment oscillation caused by electromechanical resonance, and compared with conventional electric antennas, the size can be reduced by 5 orders of magnitude, while significantly reducing the power consumption.

[0003] J. Xu from Virginia Polytechnic University in the United States studied a magnetoelectric antenna with a magnetostrictive layer / piezoelectric layer / magnetostrictive layer structure, and the radiation efficiency of this antenna is 4 orders of magnitude higher than that of an electrically small loop antenna. N. Sun from Northeastern University studied a conventional magnetoelectric antenna composed of magnetostrictive thin films and piezoelectric plates, and can achieve a communication distance of 100 meters in air. Y. Niu et al. from Shanghai University of Science and Technology added Rb permanent magnets to a Terfenol-D / PZT magnetoelectric laminate antenna to provide the DC magnetic field bias required for the maximum inverse magnetoelectric effect, and can achieve a communication distance of 2.5 m in air, which is 2.27 times higher than that without DC bias. However, conventional magnetoelectric antennas still have the following problems: First, conventional magnetoelectric antennas usually require an external permanent magnet to provide an optimal bias magnetic field to achieve a strong radiation magnetic field at the transmitting end and high sensitivity at the receiving end, but this significantly increases the volume and noise of the antenna. At the same time, conventional magnetoelectric antennas usually need to operate near the mechanical resonance frequency to significantly improve the inverse magnetoelectric / magnetoelectric effect, but this significantly reduces the bandwidth of the antenna. In addition, the magnetic field emission efficiency of current magnetoelectric antennas is still relatively low, which significantly limits the communication distance.

[0004] Currently, conventional magnetoelectric antennas are mainly composed of a magnetostrictive material and a piezoelectric layer coupled together, and mainly achieve the emission and reception of magnetic fields through the inverse magnetoelectric effect at the transmitting end and the magnetoelectric effect at the receiving end, but there is a lack of corresponding array technology research, and there are defects such as the need for an externally applied bias magnetic field, narrow bandwidth, and weak emission magnetic field, which severely restricts the realization of long-distance and large-bandwidth low-frequency communication. Summary of the Invention

[0005] In view of the problems in the background art, the present invention proposes a multi-field-driven positive feedback very low frequency magnetoelectric antenna array with high emission efficiency and large bandwidth. The magnetoelectric antenna is composed of multiple arrays of strong hysteresis piezomagnetic layers / anomalous high-permeability piezomagnetic thin films / piezoelectric layer units, a grid-shaped substrate, and magnetically shielded permanent magnet units. The remanence and magnetostrictive effect of the strong hysteresis piezomagnetic layer provide a built-in bias magnetic field for the high-permeability thin strip, eliminating the need for an external magnetic field generating device to produce the optimal bias magnetic field. When the transmitting antenna operates, on the one hand, through the elastic standing wave in the grid-shaped substrate by the piezoelectric array and the magnetic field convergence effect of the anomalous high-permeability thin strip, the strong elastic field / magnetic field coupling characteristics between array units are realized and used to drive the magnetic moment oscillation of the piezomagnetic thin strip, achieving non-linear growth of the emission field strength with the number of units, overcoming the defects of single magnetoelectric antennas and weak magnetic moment energy regulation by a single elastic field, and significantly improving the magnetic field emission efficiency; on the other hand, the alternating magnetic field generated by the magnetoelectric emission antenna array is used to regulate the positive feedback magnetic field generated by the magnetically shielded permanent magnet to achieve the magnetic field amplification function within a wide frequency band, breaking through the bottleneck of the restriction of the high quality factor on the bandwidth of the magnetoelectric antenna, increasing the frequency band and magnetic field emission efficiency, and realizing the wireless communication function with large bandwidth and long distance.

[0006] The technical solution of the present invention is as follows:

[0007] A multi-field-driven positive feedback very low frequency magnetoelectric antenna array, characterized by including multiple magnetoelectric units arranged in an array, and multiple permanent magnets wrapped by soft magnetic shielding layers;

[0008] The magnetoelectric unit successively includes a strong hysteresis piezomagnetic layer, an anomalous high-permeability piezomagnetic thin strip, a grid-shaped elastic substrate, and a piezoelectric layer from top to bottom; the grid-shaped elastic substrates of each magnetoelectric unit are connected to each other in pairs, and the input end of the piezoelectric layer is externally connected to an AC high-voltage source.

[0009] Multi-field-driven positive feedback very low frequency magnetoelectric antenna array. An internal magnetic field is established between a strong hysteresis magnetoelastic layer and a special-shaped high-permeability piezomagnetic thin strip, enabling the magnetoelectric antenna to still have optimal performance under zero bias magnetic field. Under the excitation of an alternating voltage, on the one hand, the piezoelectric layer generates an alternating stress that is transmitted to the piezomagnetic layer of this unit, causing magnetic moment oscillation and thus generating an alternating magnetic field; on the other hand, the alternating stress generated by the piezoelectric layer is transmitted to adjacent magnetoelectric units via a grid-shaped elastic substrate, and the emission magnetic field of the magnetoelectric units is enhanced through the elastic field / magnetic field coupling effect of multiple magnetoelectric units. At the same time, the alternating magnetic field generated by the magnetoelectric antenna array regulates the permeability of the soft magnetic shielding layer around the permanent magnet, causing the permanent magnet to generate an alternating magnetic field, and the alternating magnetic field generated by the magnetic shielding permanent magnet acts on the special-shaped high-permeability piezomagnetic thin strip of the magnetoelectric antenna array, further enhancing the alternating magnetic field generated by the magnetoelectric antenna. Here, a wide-band and high-emission-efficiency electromagnetic field radiation function is realized through the positive feedback mechanism between the magnetoelectric antenna and the magnetic shielding permanent magnet, thereby increasing the wireless communication distance and bandwidth.

[0010] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0011] (1) By designing the magnetoelectric antenna array, a strong elastic field / magnetic field coupling effect between multiple antenna units is realized, so that the emission magnetic field intensity of the magnetoelectric antenna array grows non-linearly with the number of units, overcoming the defect of low magnetic field emission efficiency of existing single magnetoelectric antennas and significantly increasing the wireless communication distance;

[0012] (2) At present, the high quality factor of magnetoelectric antennas restricts the volume of the piezomagnetic layer and the magnitude of the magnetic moment as the mechanical load of the piezoelectric resonator on the one hand, and also significantly restricts the antenna bandwidth on the other hand. The low-power positive feedback magnetic field excitation mechanism between the magnetoelectric antenna array and the magnetic shielding permanent magnet proposed in the present invention significantly increases the emission magnetic field within the wide frequency band, breaks the restriction of the gain-bandwidth product of conventional electrically small antennas, and significantly improves the wireless communication bandwidth and distance. Description of the Drawings

[0013] Figure 1 is the multi-field-driven reconfigurable very low frequency magnetoelectric emission antenna array of the present invention.

[0014] Figure 2 is the variable-amplitude double-wedge high-permeability piezomagnetic thin strip of the present invention.

[0015] Figure 3 is the grid-shaped elastic substrate of the present invention.

[0016] In the figure: 1 - strong hysteresis pressure magnetic layer; 2 - special-shaped high-permeability piezomagnetic thin strip; 3 - grid-shaped elastic substrate; 4 - piezoelectric layer; 5 - soft magnetic shielding layer; 6 - permanent magnet; 7 - AC high-voltage source; 8-1 - triangular magnetic convergence region of piezomagnetic thin strip; 8-2 - central target region of piezomagnetic thin strip; 9-1 - lower surface of rectangular node region of grid-shaped elastic substrate; 9-2 - upper surface of rectangular node region of grid-shaped elastic substrate. Detailed implementation mode

[0017] The present invention will be further described below in conjunction with specific embodiments and the accompanying drawings, but the protection scope of the present invention should not be limited thereby.

[0018] Refer to Figure 1 , Figure 1 , which is a multi-field-driven reconfigurable very low-frequency magnetoelectric emission antenna array of the present invention. As can be seen from the figure, the antenna array includes a strong hysteresis pressure magnetic layer 1, a special-shaped high-permeability piezomagnetic thin strip 2, a grid-shaped elastic substrate 3, a piezoelectric layer 4, a soft magnetic shielding layer 5, and a permanent magnet 6. During the antenna emission process, the piezoelectric layer 4 is excited by an AC high-voltage source 7.

[0019] The magnetoelectric antenna is composed of multiple strong hysteresis pressure magnetic layer / special-shaped high-permeability piezomagnetic thin film / piezoelectric layer, grid-shaped substrate, and magnetically shielded permanent magnet units

[0020] Figure 2 This is a variable-amplitude double-wedge high-permeability piezomagnetic thin strip of the present invention. The piezomagnetic thin strip includes four triangular magnetic convergence regions 8-1 and a central target region 8-2. The piezomagnetic thin strip uses the region 8-1 to converge the emission magnetic fields generated by the surrounding magnetoelectric units to the central region 8-2, significantly improving the driving ability of the magnetic field on the antenna.

[0021] Figure 3 This is a grid-shaped elastic substrate, on the lower surface 9-1 of multiple rectangular node regions of which a piezoelectric resonator array is fixed, and on the upper surface 9-2 of which a heterojunction array of special-shaped high-permeability piezomagnetic thin strip / hysteresis pressure magnetic layer is fixed.

[0022] The principle of the low-frequency dual-driven magnetoelectric antenna of the present invention is as follows: The transmitting antenna array is composed of a hysteretic piezomagnetic layer / anisotropic high-permeability piezomagnetic thin strip / an elastic substrate / a piezoelectric layer, and a permanent magnet unit wrapped by a soft magnetic thin strip. First, the heterojunction of the hysteretic piezomagnetic layer / anisotropic high-permeability piezomagnetic thin strip in the antenna unit provides a built-in bias magnetic field and prestress through the non-volatile magnetostatic energy and magnetoelastic energy of the hysteretic piezomagnetic layer, which can reduce the device volume and increase the piezomagnetic performance of the high-permeability piezomagnetic thin strip. When the magnetoelectric antenna works, on the one hand, multiple elastic waves generated by the piezoelectric resonator array with a specific spacing on the lower surface in the elastic substrate are superimposed at each unit to form an antinode of a standing wave, thereby realizing the elastic field coupling effect between multiple units and significantly enhancing the magnetoelastic energy that drives the magnetic moment resonance of the piezomagnetic thin strip; on the other hand, the variable-amplitude double-wedge high-permeability piezomagnetic thin strip is used to converge the magnetic fields generated by the inverse magnetoelectric effect of adjacent magnetoelectric units, realizing the strong magnetic field coupling effect between multiple units. In order to further realize the magnetic field amplification function within a wide frequency band, this project plans to use a piezoelectric material with a large piezoelectric coefficient but a moderate Q value (such as a piezoelectric single crystal) to drive the alternating magnetic field generated by the magnetoelectric transmitting antenna array to regulate the magnetic permeability and magnetic resistance of the soft magnetic shielding layer around the permanent magnet. By periodically controlling the opening and closing of the magnetic flux circuit, the magnetostatic energy of the permanent magnet is modulated into an alternating magnetic field and emitted into the air. At this time, the alternating magnetic field generated by the permanent magnet will further intensify the magnetic moment oscillation of the piezomagnetic layer in the magnetoelectric unit, thereby increasing the transmitting magnetic field generated by the magnetoelectric antenna array. This positive feedback process continues until the magnetic moments of the two magnetic sources reach an equilibrium state, thereby amplifying the transmitting magnetic field without additional power consumption of the magnetoelectric antenna and realizing a wide frequency band and high magnetic field emission efficiency.

Claims

1. A multi-field-driven positive-feedback very low-frequency magnetoelectric antenna array, characterized in that, it includes a plurality of magnetoelectric units distributed in an array, and a plurality of permanent magnets wrapped by soft magnetic shielding layers; The magnetoelectric unit successively includes a strong hysteresis back-pressure magnetic layer, a special-shaped high-permeability piezomagnetic thin strip, a grid-shaped elastic substrate, and a piezoelectric layer from top to bottom; the grid-shaped elastic substrates of each magnetoelectric unit are connected to each other in pairs, and the input end of the piezoelectric layer is externally connected to an AC high-voltage source. Under the excitation of the AC voltage, the piezoelectric layer generates an AC stress and transmits it to the strong hysteresis back-pressure magnetic layer of the current magnetoelectric unit, causing magnetic moment oscillation and thus generating an AC magnetic field; at the same time, the AC stress generated by the piezoelectric layer is transmitted to the adjacent magnetoelectric unit through the grid-shaped elastic substrate, and the emission magnetic field of the magnetoelectric unit is enhanced through the elastic and magnetic field coupling effects of multiple magnetoelectric units; The AC magnetic field generated by the magnetoelectric antenna array regulates the magnetic permeability of the soft magnetic shielding layer around each permanent magnet, so that the permanent magnet generates an AC magnetic field, and the AC magnetic field acts in a feedback manner on the special-shaped high-permeability piezomagnetic thin strip of the magnetoelectric antenna array, enhancing the AC magnetic field generated by the magnetoelectric antenna array; The special-shaped high-permeability piezomagnetic thin strip includes four triangular magnetic convergence regions and a central target region surrounded by the four triangular magnetic convergence regions; the triangular magnetic convergence regions converge the emission magnetic fields generated by each magnetoelectric unit around to the central target region.

2. The multi-field-driven positive-feedback very low-frequency magnetoelectric antenna array according to claim 1, characterized in that, a built-in magnetic field is formed between the strong hysteresis back-pressure magnetic layer and the special-shaped high-permeability piezomagnetic thin strip.

3. The multi-field-driven positive-feedback very low-frequency magnetoelectric antenna array according to claim 1, characterized in that, the grid-shaped elastic substrate is arranged in a grid pattern of horizontal and vertical intersections, and the lower surface of the horizontal and vertical intersections fixes the upper surface of the piezoelectric layer, and the heterojunction array of the special-shaped high-permeability piezomagnetic thin strip and the strong hysteresis back-pressure magnetic layer is fixed.

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