Miniaturized broadband antenna based on composite magnetic dielectric ferrite coating

Abstract

The invention relates to the technical field of planar antennas, and particularly discloses a miniaturized broadband antenna based on a composite magnetic dielectric ferrite coating, and the structure of the miniaturized broadband antenna based on the composite magnetic dielectric ferrite coating uses a sine arc-shaped main radiation patch, a linear gradient feed structure and a multi-layer trapezoidal ground plane. And meanwhile, a hypotenuse branch knot is used for widening the working bandwidth, and a low-magnetic dielectric loss composite ferrite material is used as a coating layer part. Through the reasonable application of the technical means, the small-size broadband antenna can be achieved, the radiation efficiency and gain of the antenna can be ensured, and the whole antenna has good performance.

Description

Technical Field

[0001] The invention relates to the technical field of planar antennas, and in particular to a miniaturized broadband antenna based on a composite magnetic dielectric ferrite coating. Background Art

[0002] With the rapid development of mobile communications, the Internet of Things, satellite communications and other fields, not only are the requirements for the size and weight of antennas becoming increasingly stringent, but the requirements for the working bandwidth of antennas are also becoming wider. The demand for miniaturized antennas is becoming increasingly urgent so that they can be better integrated into small devices and improve the portability and flexibility of the system. Broadband antennas can operate in a wider frequency range, meet the needs of different communication standards and frequency bands, and provide higher data transmission rates and better signal coverage capabilities. Miniaturized broadband antennas have always been the focus of current research. In order to achieve high-performance antennas that are both miniaturized and broadband, it is necessary to start from three aspects: theoretical principles, structural design, materials and processing. Among them, exploring new materials with excellent performance and combining them with existing small broadband technologies are very critical to achieving high-performance antennas.

[0003] Traditional dielectric substrate antennas are large in size and difficult to integrate at low frequencies. Magnetic ferrite materials also have magnetic dielectric properties, which provide additional degrees of freedom, allowing the effective wavelength of electromagnetic waves to be significantly reduced during propagation, thereby reducing the physical size of the antenna. They are often used in the design and manufacture of miniaturized antennas, which is very beneficial to the trend of increasing requirements for device size and weight in modern wireless communication applications. Magnetic ferrite materials are no longer limited to a single dielectric property regulation, and can achieve more flexible and efficient antenna design. Therefore, there is an urgent need for a solution that can achieve miniaturization and broadband antenna design while ensuring the antenna gain radiation efficiency. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a miniaturized broadband antenna based on a composite magnetic-dielectric ferrite coating, which adopts a specific composite magnetic-dielectric ferrite material as the coating part and adjusts the period and amplitude of the sinusoidal radiation patch. It can achieve the dual goals of miniaturization and broadband of antenna design while ensuring the antenna gain radiation efficiency, and solves the problems mentioned in the above background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a miniaturized broadband antenna based on a composite magnetic dielectric ferrite coating, comprising an insulating dielectric substrate, a main radiation patch, a bevel branch, a ground plane, a microstrip feeder located on a first layer, and a composite magnetic dielectric ferrite material coating located on a second layer; a microstrip feeder is arranged in the middle of the bottom of the front side of the insulating dielectric substrate, a ground plane is arranged symmetrically on the left and right of the microstrip feeder, there is a distance between the microstrip feeder and the symmetrical ground plane, the front side of the microstrip feeder is connected to the main radiation patch, and two symmetrical bevel branches extending outward are arranged at the connection between the microstrip feeder and the main radiation patch.

[0006] Two symmetrical oblique-edge branches extend outward from the intersection of the feed line and the main radiation patch, generating a new resonance point close to the original resonance point, thereby expanding the antenna bandwidth and ensuring the symmetry of the antenna radiation pattern.

[0007] Preferably, the miniaturized broadband antenna based on the composite magnetic dielectric ferrite coating has an operating frequency band of 1.95-4 GHz, a relative bandwidth of 68.9%, a gain within the operating frequency band of up to 1.9 dBi, and a radiation efficiency higher than 85%.

[0008] Preferably, the composite magnetic dielectric ferrite material coating is located on top of the main radiation patch and serves as a coating structure; the composite magnetic dielectric ferrite material coating does not completely cover the first layer of the insulating dielectric substrate. The portion covered by the composite magnetic dielectric ferrite material coating is a sinusoidal radiation patch, which not only reduces the amount of ferrite used but also facilitates coplanar waveguide feeding. Full coverage of ferrite will lead to severe impedance mismatch and reduce the overall radiation efficiency of the antenna. In addition, the coating ferrite loading position needs to be appropriate, and the current density of the covered radiation patch should be large, otherwise the size reduction effect will not be good.

[0009] Preferably, the microstrip feed line is a linear gradient microstrip feeding structure; the ground plane is a multi-layer trapezoidal ground plane, and forms a coplanar waveguide feeding structure with the linear gradient microstrip feeding structure located in the same layer.

[0010] Preferably, the insulating dielectric substrate is made of FR4 epoxy resin composite material, whose dielectric constant is 4.4 and dielectric loss is 0.02; and the main radiation patch is a sinusoidal arc radiation patch.

[0011] Preferably, the edge of the sinusoidal arc radiation patch adopts the function y(x)=c*cos(w*(x)), wherein reducing the period of the sinusoidal radiation patch (i.e. increasing the angular frequency w) and increasing the amplitude (i.e. the proportional factor c) can expand the current path, but more bends will lead to a decrease in the effective current path, because of the current offset effect, which will lead to a sharp decrease in the antenna radiation efficiency and damage the overall performance of the antenna. Therefore, it is more appropriate to reasonably select the angular frequency w and the proportional factor c. The present invention selects the proportional factor c=1.5 and the angular frequency w=1.5.

[0012] Preferably, since the composite magnetic dielectric ferrite has both relative magnetic permeability and a high relative dielectric constant, according to the calculation formula of the medium transmission wavelength The use of composite magnetic dielectric ferrite material as the antenna coating can achieve miniaturization of the antenna. The composite magnetic dielectric ferrite material coating is unpolarized, non-magnetically biased (1-x) Mg 0.7 Cd 0.3 The Fe2O4+xBaTiO3 (x=0.09) composite magnetic dielectric ferrite material has a dielectric constant of 7.7 at 1-4G, a magnetic permeability of 1-2, a dielectric loss of less than 0.009, and a magnetic loss of less than 0.06.

[0013] Preferably, the (1-x)Mg 0.7 Cd 0.3 The preparation method of Fe2O4+xBaTiO3 (x=0.09) composite magnetic dielectric ferrite material is as follows:

[0014] S1, stoichiometrically measuring and mixing the raw materials MgO, CdO and Fe2O3 according to the proportion;

[0015] S2, ball milling the mixture in a planetary ball mill at a rotation speed of 200 rpm for 6 hours to achieve complete mixing;

[0016] S3, drying and pre-calcining the mixed material at 1200° C. for 24 hours to initially form a spinel phase;

[0017] S4, BaTiO3 and spinel phase powder are mixed, and ball milled and dried until they become dry powder, thus obtaining (1-x)Mg 0.7 Cd 0.3 Fe2O4+xBaTiO3 (x=0.09) composite magnetic dielectric ferrite material.

[0018] The beneficial effects of the present invention are:

[0019] 1) The main radiation patch of the present invention adopts a sinusoidal arc radiation patch, and the period and amplitude are reasonably adjusted to extend the antenna current flow path, and the low-frequency working frequency of the antenna is further expanded, thereby realizing the miniaturization of the antenna. The antenna adopts coplanar waveguide feeding, which is not only easy to process and integrate discrete components, but also can achieve a wider bandwidth characteristic due to its better dispersion characteristics;

[0020] 2) The present invention uses (1-x)Mg 0.7 Cd 0.3Fe2O4+xBaTiO3 (x=0.09) composite ferrite material is used as the antenna covering part. It has magnetic and dielectric properties. According to the calculation formula of the medium transmission wavelength, the low-frequency point can be moved to a lower frequency. And because the composite ferrite material used has low dielectric loss and magnetic loss in the applied frequency band, the antenna radiation efficiency and gain can be guaranteed while achieving small and broadband antenna. The antenna has good performance as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of a miniaturized broadband antenna in an embodiment of the present invention;

[0022] Figure 2 The comparison diagram of the simulated S11 curve of the antenna with no branches added and with bevel branches added;

[0023] Figure 3 It is a comparison diagram of the simulated S11 curves of the antenna without composite magnetic dielectric ferrite loading and the antenna loaded with composite magnetic dielectric ferrite material as the covering part;

[0024] Figure 4 It is a comparison diagram of the simulated S11 curves of the antenna loaded with composite magnetic dielectric ferrite materials of different lengths as the covering layer in the embodiment of the present invention;

[0025] Figure 5 A comparison diagram of simulated gain and efficiency curves of antennas loaded with composite magnetic dielectric ferrite materials of different lengths as a covering layer in an embodiment of the present invention;

[0026] Figure 6 The simulated radiation efficiency and far-field gain curve of the antenna loaded with composite magnetic dielectric ferrite material in the embodiment of the present invention;

[0027] In the figure, 1 is an insulating dielectric substrate; 2 is a main radiation patch; 3 is a beveled branch; 4 is a ground plane; 5 is a microstrip feed line; and 6 is a composite magnetic dielectric ferrite material coating. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that the embodiments and features of the embodiments of the present invention can be combined with each other without conflict. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0030] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use, or the positions or positional relationships commonly understood by those skilled in the art, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] The present invention provides a technical solution: a miniaturized broadband antenna based on a composite magnetic dielectric ferrite coating, such as Figure 1 As shown, the xy plane in the figure is the plane of the antenna, wherein the x direction is the length and the y direction is the width. The miniaturized broadband antenna comprises an insulating dielectric substrate 1 located on the first layer, a main radiation patch 2, a bevel branch 3, a ground plane 4, a microstrip feed line 5, and a composite magnetic dielectric ferrite material coating 6 located on the second layer.

[0033] The composite magnetic dielectric ferrite material coating 6 is located in the second layer as a coating structure, which does not completely cover the lower insulating dielectric substrate 1. The ground plane 4 is a multi-layer trapezoidal ground plane. In addition, the microstrip feed line adopts a linear gradient microstrip feeding structure, which together with the multi-layer trapezoidal ground plane constitutes a coplanar waveguide feeding structure, which helps to achieve a wider bandwidth.

[0034] Furthermore, the insulating dielectric substrate 1 adopts FR4 epoxy resin composite material with excellent mechanical properties, electrical insulation properties and chemical corrosion resistance, and its length, width and height are 30mm×30mm×0.8mm respectively. The dielectric constant of the FR4 is 4.4 and the dielectric loss is 0.02.

[0035] Furthermore, the edge of the sinusoidal arc radiation patch adopts the function y(x)=c*cos(w*(x)), the proportional factor c=1.5, and the angular frequency w=1.5; the edge curve distance of the sinusoidal arc main radiation patch is d=9.5mm, and the width of the sinusoidal arc main radiation patch ww=30mm.

[0036] Furthermore, the ground plane is located on the same layer as the main radiation patch, and is g = 0.15 mm away from the bottom of the microstrip feeder. The ground plane is a multi-layer trapezoidal ground plane with a lateral width wt = 11.85 mm and a longitudinal width lt = 14 mm. The lateral trapezoidal width is lq1 = 3.5 mm, and the longitudinal trapezoidal length is lq2 = 3.5 mm.

[0037] The hypotenuse branch extends outward from the intersection of the feed line and the main radiation patch, with a line width of www = 1.5mm and a length of ll = 14.8mm. The bottom line width of the linear gradient microstrip feed line is wb = 2.7mm, the top line width is wt = 0.8mm, and the feed length is lf = 20mm. Figure 2 The figure shows the comparison of the simulated S11 curves of the antenna without adding branches and with adding bevel branches. After adding branches, the antenna has a new resonance point, and the working frequency band is greatly broadened after combining with the original antenna, with a working bandwidth of 1.95-4G and a relative working bandwidth of 68.9%.

[0038] The present invention uses a composite magnetic dielectric ferrite material as the cladding part to achieve miniaturization of the antenna. The specific principle can be explained according to the calculation formula of the medium transmission wavelength:

[0039]

[0040] Where c is the speed of light, ε r is the relative dielectric constant, μ r is the relative magnetic permeability, f is the operating frequency, and λ is the operating wavelength. The composite magnetic dielectric ferrite coating is covered on the top of the sinusoidal radiation patch, with a length of le = 13mm, a width of we = 30mm, and a height of he = 1.2mm.

[0041] From the calculation formula of the medium transmission wavelength, it can be obtained that the magnetic dielectric composite ferrite material used has both magnetic dielectric properties, which can reduce the transmission wavelength and thus reduce the size of the antenna. In addition, the composite magnetic dielectric ferrite material used still maintains low dielectric loss and magnetic loss in the GHz frequency band. Its application frequency range for antennas is wider, and it has good application prospects in antennas working in the GHz frequency band.

[0042] Furthermore, (1-x)Mg 0.7 Cd 0.3 The preparation method of Fe2O4+xBaTiO3 (x=0.09) composite magnetic dielectric ferrite material is as follows:

[0043] S1, stoichiometrically measuring the raw materials MgO, CdO and Fe2O3 according to the proportions in the synthesized target composite material;

[0044] S2, ball milling the mixture in a planetary ball mill at a rotation speed of 200 rpm for 6 hours to achieve complete mixing;

[0045] S3, drying and pre-calcining the mixed material at 1200° C. for 24 hours to initially form a spinel phase;

[0046] S4, BaTiO3 and spinel phase powder are mixed, and the same ball milling and drying process is carried out until they become dry powder, that is, (1-x)Mg 0.7 Cd 0.3 Fe2O4+xBaTiO3 (x=0.09) composite magnetic dielectric ferrite material.

[0047] like Figure 3 As shown, it is a comparison diagram of the simulated S11 curves of the antenna without composite magnetic dielectric ferrite loading and the antenna with composite magnetic dielectric ferrite material as the covering part. Figure 3 It can be seen that after loading the magnetic-dielectric composite ferrite material as the covering part, the low frequency of the antenna is extended, the size of the antenna is reduced, and the antenna still maintains a wide working bandwidth.

[0048] like Figure 4 As shown in the figure, it is a comparison of the simulated S11 curves of the antenna with different lengths of composite magnetic dielectric ferrite materials as the covering layer in the embodiment of the present invention. When the magnetic dielectric composite ferrite material covering layer is close to the lower edge of the main radiation patch, that is, the part with strong current density, the antenna has a more obvious effect of extending to low frequencies. However, when covering the feed line, it will cause impedance mismatch and affect the antenna performance.

[0049] like Figure 5As shown in the figure, it is a comparison diagram of the simulated gain of the antenna loaded with different lengths of composite magnetic dielectric ferrite materials as the covering part in the embodiment of the present invention. Due to the low magnetic dielectric loss of the magnetic dielectric composite ferrite material, the antenna still maintains a relatively good gain. However, when covering the feed line, it will cause impedance mismatch and thus affect the antenna working performance.

[0050] like Figure 6 As shown in the figure, it is a simulated radiation efficiency and far-field gain curve of the antenna loaded with composite magnetic dielectric ferrite material in the embodiment of the present invention. Due to the low magnetic dielectric loss of the magnetic dielectric composite ferrite material, the antenna still maintains relatively good gain and radiation efficiency. The gain in the working frequency band can reach up to 1.9dBi, and the radiation efficiency is higher than 85%.

[0051] From the above simulation results, it can be seen that the present invention selects ferrite as the coating part based on its magnetic permeability and dielectric constant to reduce the transmission wavelength, and the sinusoidal main radiation patch is used to extend the current length to reduce the size of the antenna. The planar antenna based on the composite magnetic dielectric ferrite material coating proposed by the present invention has a wider impedance bandwidth and smaller size, and the maximum gain in the working frequency band is higher than 1.9dBi, and the gain gradually increases with the increase of frequency, which can be explained by the following formula:

[0052]

[0053] Where: G is the gain, A is e is the effective area of ​​the antenna, and λ is the operating wavelength. This relationship shows that the effective electrical area of ​​the antenna The larger it is, the higher the antenna gain is. Within the operating frequency band, the low-frequency gain is smaller than the high-frequency gain because the wavelength of the low-frequency point is longer when the antenna radiation effective area is the same, so the gain gradually increases with the increase of frequency.

[0054] In summary, the present invention provides a miniaturized broadband antenna based on a composite magnetic dielectric ferrite coating, with an operating frequency band of 1.95-4 GHz and a relative bandwidth of 68.9%. It can have the advantages of small size and good performance while ensuring wide bandwidth characteristics. Its operating frequency band covers the S band and has broad application prospects.

[0055] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A miniaturized broadband antenna based on a composite magnetic dielectric ferrite coating, characterized in that: The invention comprises an insulating dielectric substrate (1) located on a first layer, a main radiation patch (2), a beveled branch (3), a ground plane (4), a microstrip feed line (5), and a composite magnetic dielectric ferrite material coating (6) located on a second layer; a microstrip feed line (5) is arranged in the middle of the bottom of the front side of the insulating dielectric substrate (1); a ground plane (4) is arranged symmetrically on the left and right of the microstrip feed line (5); a distance exists between the microstrip feed line (5) and the symmetrical ground plane (4); the front side of the microstrip feed line (5) is connected to the main radiation patch (2); and two symmetrical beveled branches (3) extending outward are arranged at the connection between the microstrip feed line (5) and the main radiation patch.

2. The miniaturized broadband antenna based on composite magnetic dielectric ferrite coating according to claim 1, characterized in that: The working frequency band of the miniaturized broadband antenna based on the composite magnetic dielectric ferrite coating is 1.95-4 GHz, the relative bandwidth is 68.9%, the gain in the working frequency band can reach 1.9 dBi, and the radiation efficiency is higher than 85%.

3. The miniaturized broadband antenna based on composite magnetic dielectric ferrite coating according to claim 1, characterized in that: The composite magnetic dielectric ferrite material coating (6) is located on the top of the main radiation patch and serves as a coating structure; the composite magnetic dielectric ferrite material coating (6) does not completely cover the first layer of the insulating dielectric substrate (1).

4. The miniaturized broadband antenna based on composite magnetic dielectric ferrite coating according to claim 1, characterized in that: The microstrip feed line (5) is a linear gradient microstrip feeding structure; the ground plane (4) is a multi-layer trapezoidal ground plane, and forms a coplanar waveguide feeding structure with the linear gradient microstrip feeding structure located on the same layer.

5. The miniaturized broadband antenna based on composite magnetic dielectric ferrite coating according to claim 1, characterized in that: The insulating dielectric substrate (1) is made of FR4 epoxy resin composite material, with a dielectric constant of 4.4 and a dielectric loss of 0.02; the main radiation patch (2) is a sinusoidal arc radiation patch.

6. The miniaturized broadband antenna based on composite magnetic dielectric ferrite coating according to claim 5, characterized in that: The edge of the sinusoidal arc radiation patch adopts the function y(x)=c*cos(w*(x)), wherein the proportional factor c=1.5 and the angular frequency w=1.

5.

7. The miniaturized broadband antenna based on composite magnetic dielectric ferrite coating according to claim 1, characterized in that: The composite magnetic dielectric ferrite material coating (6) is (1-x)Mg 0.7 Cd 0.3 The Fe2O4+xBaTiO3 (x=0.09) composite magnetic dielectric ferrite material has a dielectric constant of 7.7 at 1-4G, a magnetic permeability of 1-2, a dielectric loss of less than 0.009, and a magnetic loss of less than 0.

06.

8. The miniaturized broadband antenna based on composite magnetic dielectric ferrite coating according to claim 7, characterized in that: The (1-x)Mg 0.7 Cd 0.3 The preparation method of Fe2O4+xBaTiO3 (x=0.09) composite magnetic dielectric ferrite material is as follows: S1, stoichiometrically measuring and mixing the raw materials MgO, CdO and Fe2O3 according to the proportion; S2, ball milling the mixture in a planetary ball mill at a rotation speed of 200 rpm for 6 hours to achieve complete mixing; S3, drying and pre-calcining the mixed material at 1200° C. for 24 hours to initially form a spinel phase; S4, BaTiO3 and spinel phase powder are mixed, and ball milled and dried until they become dry powder, thus obtaining (1-x)Mg 0.7 Cd 0.3 Fe2O4+xBaTiO3 (x=0.09) composite magnetic dielectric ferrite material.

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