Cross dipole broadband antenna

Abstract

The invention discloses a cross dipole broadband antenna, which belongs to the field of wireless communication, has a dual-polarization characteristic and can support two mutually vertical polarization directions at the same time, and the high isolation and the optimized design of the dual-polarization antenna reduce signal attenuation and loss and ensure the reliability and the stability of a communication system. Moreover, the antenna is provided with a balun structure which can effectively cut off the high-frequency current flowing through the sheath of the cable shielding layer from the cross dipole patch, thereby ensuring the correct transmission of signals and good antenna performance. The Balun structure can realize the conversion between different impedances, so that the impedance between the antenna and the transmission line is matched, and the maximum power transmission is ensured; besides, the patch of the antenna adopts a novel fractal structure, namely a quartering circular fractal structure, so that the antenna performance is improved, the broadband characteristic is maintained while the light weight is realized, the frequency bandwidth is improved, and the radiation efficiency is optimized.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communications, and more specifically, relates to a cross-dipole broadband antenna. Background Art

[0002] Compared with other types of antennas, cross-dipole antennas are very popular in modern wireless communication systems and are one of the important choices for broadband antenna design. The reasons are as follows: (1) The cross-dipole antenna design can provide a wider operating bandwidth, which is very important for wireless communication systems that need to cover multiple frequency bands. (2) The cross-dipole antenna design helps to miniaturize the antenna, save space and weight, and reduce costs. (3) The cross-dipole antenna can be designed to be dual-polarized, further improving the signal-to-noise ratio and anti-interference characteristics of the communication system. (4) The cross-dipole antenna has a simple structure and is easy to implement and integrate into the system. At the same time, the feeding method is convenient, which helps to simplify the installation and maintenance of the antenna. (5) The cross-dipole antenna can achieve directional radiation, which is very useful for applications that require signals to be transmitted in a specific direction. (6) The cross-dipole antenna can achieve filtering functions by loading a specific structure, improving the impedance bandwidth and axial ratio bandwidth. However, since the cross-dipole antenna is composed of multiple dipoles, there may be electromagnetic coupling between them. This coupling may cause interference between antennas and performance degradation. In addition, in order to achieve better performance, the cross-dipole antenna may require complex structural design and sophisticated processing technology. For example, for some dual-polarized or multi-polarized cross-dipole antennas, it is necessary to precisely control parameters such as the size, shape, position and direction of each dipole, which places high demands on processing and manufacturing precision, increasing production costs and difficulty. Summary of the invention

[0003] In view of the above defects or improvement needs of the prior art, the present invention provides a cross-dipole broadband antenna, thereby solving the problems of interference between antennas and complex structural design caused by electromagnetic coupling in the existing cross-dipole antenna.

[0004] To achieve the above object, according to a first aspect of the present invention, there is provided a cross-dipole broadband antenna, comprising: a substrate, a balun structure, a cross-dipole patch, a metal reflector and two coaxial cables;

[0005] The cross-dipole patch includes a first dipole patch unit and a second dipole patch unit, and the first dipole patch unit and the second dipole patch unit each include two metal sheets, the two metal sheets of the first dipole patch unit and the second dipole patch unit are respectively connected to each other by a first metal strip and a second metal strip, the first dipole patch unit and the second dipole patch unit are cross-placed on the substrate, and the first metal strip and the second metal strip are perpendicular to each other, so that the first dipole patch unit and the second dipole patch unit are rotationally symmetrically distributed on the substrate; wherein the shape of the metal sheet is a splicing of a three-quarter circle sector composed of two straight line segments and an arc segment and a square, and two adjacent sides of the square completely overlap with the two straight line segments, and the sector area of ​​the metal sheet has three circular hollow openings, which are respectively located in each sub-area after the sector area is divided into three equal parts, with the midpoint of the bisector of each sub-area as the center of the circle and the radius of the three-quarter circle as the diameter;

[0006] The balun structure includes a bottom plate and two conductive columns; wherein the bottom plate is placed above the metal reflector, one end of the two conductive columns is respectively connected to one side of the bottom plate, and the other end is respectively connected to the first and second dipole patch units;

[0007] One end of the two coaxial cables is connected to the bottom plate respectively, and the other end is connected to the first and second dipole patch units respectively.

[0008] According to a second aspect of the present invention, there is provided a drone system, comprising a drone and the cross-dipole broadband antenna as described in the first aspect.

[0009] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0010] The cross-dipole broadband antenna provided by the present invention has dual-polarization characteristics and can simultaneously support two mutually perpendicular polarization directions. The high isolation and optimized design of the dual-polarization antenna reduce signal attenuation and loss, ensuring the reliability and stability of the communication system; and the cross-dipole antenna designed by the present invention has a balun structure, which can effectively cut off the high-frequency current flowing from the cross-dipole patch through the outer skin of the cable shielding layer, ensuring the correct transmission of the signal and good antenna performance; in addition, the balun structure can realize the conversion between different impedances, so that the impedance between the antenna and the transmission line is matched, thereby ensuring maximum power transmission; in addition, the patch of the present invention adopts a new fractal structure, that is, a quarter-circle fractal structure, which is conducive to improving the antenna performance, achieving lightweight while maintaining broadband characteristics, increasing bandwidth, and optimizing radiation efficiency. Due to the self-similarity of the fractal, the fractal antenna maintains the similarity of electrical properties at different scales, thereby realizing multi-band working characteristics; the fractal structure reduces the size of the antenna, and by introducing the fractal structure, the electrical length of the antenna can be effectively increased without physically increasing the actual size of the antenna. This means that the physical size of the antenna can be significantly reduced while maintaining the same antenna performance; the design of the fractal antenna allows more efficient energy coupling and radiation, helping to improve the overall performance and efficiency of the antenna.

[0011] The cross-dipole broadband antenna provided by the present invention is applied to the working scene of a drone for example for simulation. The simulation results show that the cross-dipole antenna provided by the present invention covers the frequency band of 1.81GHz to 2.81GHz in the -15dB impedance bandwidth, and the port isolation in the frequency band of 1.50GHz to 2.81GHz is greater than 25dB. The antenna 3D radiation pattern shows that the maximum gain is 7.98dB and has good radiation characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is one of the schematic diagrams of a broadband cross-dipole antenna provided in an embodiment of the present invention.

[0013] Figure 2 The second schematic diagram of the broadband cross-dipole antenna provided in the embodiment of the present invention.

[0014] Figure 3 A schematic diagram of a fractal structure of a four-circle partition provided in an embodiment of the present invention.

[0015] Figure 4 A schematic diagram of the patch shape provided by an embodiment of the present invention.

[0016] Figure 5 A schematic diagram comparing the first-order Sierpinski-like fractal structure and the quartered circle fractal structure of the broadband cross-dipole antenna provided in an embodiment of the present invention.

[0017] Figure 6 A diagram of the simulation results of the input reflection coefficient S11 corresponding to the first-order Sierpinski-like fractal structure and the quartered circle fractal structure of the cross-dipole antenna provided in an embodiment of the present invention.

[0018] Figure 7 A diagram of simulation results of the forward transmission coefficient S21 corresponding to the first-order Sierpinski-like fractal structure and the quarter-circle of the cross-dipole antenna provided in an embodiment of the present invention.

[0019] Figure 8 A return loss simulation comparison diagram of a broadband cross dipole antenna with a balun structure and a broadband cross dipole antenna without a balun structure provided in an embodiment of the present invention.

[0020] Fig. 9 A comparison diagram of port isolation simulation between a broadband cross dipole antenna with a balun structure and a broadband cross dipole antenna without a balun structure provided in an embodiment of the present invention.

[0021] Fig.10 This is a diagram of EH plane simulation results when the broadband cross-dipole antenna provided by an embodiment of the present invention is provided with a balun structure.

[0022] Fig.11 This is a diagram of EH plane simulation results of the broadband cross-dipole antenna provided by an embodiment of the present invention without a balun structure.

[0023] Fig.12 A diagram showing the simulation results of a broadband cross-dipole 3D pattern with a balun structure provided in an embodiment of the present invention.

[0024] Fig.13 A diagram showing the simulation results of a broadband cross-dipole 3D pattern without a balun structure provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] An embodiment of the present invention provides a cross-dipole broadband antenna, such as Figure 1-2 As shown, it includes: a substrate 1, a balun structure 2, a cross-dipole patch 3, a metal reflector 4 and two coaxial cables 51, 52;

[0027] The cross-dipole patch includes a first dipole patch unit and a second dipole patch unit, and the first and second dipole patch units each include two metal sheets of exactly the same shape and size, the two specific metal sheets of the first dipole patch unit are connected to each other through a first metal strip, and the two specific metal sheets of the second dipole patch unit are connected to each other through a second metal strip, the first and second dipole patch units are cross-placed on the substrate, the intersection coincides with the center point of the substrate, and the first and second metal strips are perpendicular to each other, so that the first and second dipole patch units are rotationally symmetrically distributed on the substrate; wherein the shape of the metal sheet is a three-quarter circle sector composed of two straight line segments and an arc segment spliced ​​with a square, and the two adjacent sides of the square completely coincide with the two straight line segments, that is, as Figure 4 As shown, the side length r1 of the square is equal to the length d1 / 2 of the straight line segment; the fan-shaped area of ​​the metal sheet has three circular hollow openings, which are respectively located in each sub-area after the fan-shaped area is divided into three equal parts, and the average dividing line of each sub-area (such as Figure 4 As shown, the dividing line is a line that divides the sub-area into two areas equally, with the midpoint of the radius of three quarters of the circle as the center and the radius of three quarters of the circle as the diameter, that is, d2 = d1 / 2;

[0028] The balun structure includes a base plate and two conductive columns; wherein the base plate is placed above the metal reflector, one end of the two conductive columns is respectively connected to one side of the base plate, and the other end is respectively connected to the first and second dipole patch units;

[0029] One end of the two coaxial cables is connected to the bottom plate respectively, and the other end is connected to the first and second dipole patch units respectively.

[0030] like Figure 3 As shown in (a) and (b) in the figure, the fractal structure of the patch proposed in the example of the present invention is a four-divided circular fractal structure. On the basis of the original circular antenna patch, two mutually perpendicular diameters are made, and the two diameters are divided into four equal parts. The centers of the four small circles are located at the one-quarter and three-quarter points of the two diameters. The diameter of the small circle is one-fourth of the large circle. The four small circles on each patch are dug out to form a four-divided circular fractal structure. Due to the influence of the position of the ideal conductor and the balun, each oscillator (i.e., patch) will only dug out the three small circles that are farther away from the center point of the substrate.

[0031] Preferably, the connection portions between one end of the two conductive pillars and one side of the bottom plate are both rounded.

[0032] Preferably, the two coaxial cables each include an inner conductor and an outer conductor, which are respectively connected to the two metal sheets of the first and second dipole patch units in a one-to-one correspondence.

[0033] The antenna provided by an embodiment of the present invention is fed by two coaxial cables, each coaxial cable is connected to a pair of dipoles (i.e., the first dipole patch unit or the second dipole patch unit), wherein the inner conductor and the outer conductor are each connected to a dipole, that is, the inner conductor and the outer conductor are respectively connected to a pair of dipoles in a one-to-one correspondence.

[0034] Preferably, the lengths of the two conductive pillars are each one-quarter of the length of the transmission line.

[0035] Preferably, vertical metal plates are arranged around the metal reflective plate.

[0036] The metal reflector can effectively reflect the signal emitted by the vibrator, enhance the radiation intensity of the antenna in a specific direction, and improve the signal's directivity and coverage.

[0037] Preferably, the substrate is made of glass_PTFEreinf material.

[0038] The thickness and dielectric constant of the substrate are set according to the working frequency band of the antenna and can be obtained using the simulation software HFSS.

[0039] Balun is the abbreviation of Balanced-to-Unbalanced Converter, which is an electronic device used to convert a balanced signal (such as a differential signal) into an unbalanced signal (such as a single-ended signal). The application of balun in antenna design is extremely important. It not only solves the conversion problem between balanced and unbalanced signals, but also improves the performance of the antenna and the stability of the wireless communication system through impedance matching, common mode suppression and other functions.

[0040] The cross-dipole broadband antenna provided in the embodiment of the present invention can effectively cut off the high-frequency current flowing from the cross-dipole patch through the outer skin of the cable shielding layer through the balun structure, ensuring the correct transmission of the signal and good antenna performance; the patch fractal structure adopted can effectively increase the electrical length of the antenna without physically increasing the actual size of the antenna. This means that the physical size of the antenna can be significantly reduced while keeping the antenna performance unchanged; the designed antenna has the characteristics of dual polarization and miniaturization, and is suitable for a variety of communication scenarios, especially communication scenarios that require lightweight and miniaturized antennas, such as drones. Based on this, an embodiment of the present invention provides a drone system, including a drone and a cross-dipole broadband antenna as described in any of the above embodiments.

[0041] The following is a comparative analysis of the performance of the cross-dipole broadband antenna provided in the embodiment of the present invention and the antenna after the antenna patch is optimized using a first-order Sierpinski-like fractal structure.

[0042] like Figure 5 As shown in (a) and (b) in FIG. 1 , the classic Sierpinski carpet is a square. The square is divided into 9 equal parts, and the middle part is dug out to obtain a first-order Sierpinski fractal structure. Similarly, a similar operation is performed on the circular patch in the example of the present invention, and the circle in the center of the patch is dug out to obtain a first-order Sierpinski fractal structure, such as Figure 5 As shown in (a); the schematic diagram of the application of the four-circle fractal structure proposed in the example of the present invention to the antenna patch is shown in Figure 5 As shown in (b); it can be understood that in order to facilitate the connection between the two patches of the first dipole patch unit / the second dipole patch unit, the square edge area of ​​the patch can be cut off. The cross-dipole broadband antenna provided in the embodiment of the present invention uses a glass_PTFEreinf material with a thickness of 1 mm and a relative dielectric constant of 2.5.

[0043] S parameters, the full name of which is scattering parameters, are complex values ​​that describe the reflection and transmission characteristics of electromagnetic waves in RF devices such as antennas at specific frequencies. They are one of the criteria for judging the performance of antennas and are extremely important in RF and microwave engineering. These parameters can not only provide detailed information about the reflection and transmission characteristics of antennas, but also help engineers design and optimize antenna structures to achieve the best communication effect.

[0044] For antennas, S parameters mainly include S11 (input reflection coefficient), S21 (forward transmission coefficient), S12 (reverse transmission coefficient) and S22 (output reflection coefficient). Since the positions of the two ports in the example of the present invention are symmetrical, only S11 and S21 are considered in the S parameters to characterize the antenna performance.

[0045] The S11 parameter reflects the antenna's return loss, that is, how much energy is reflected by the antenna instead of being effectively radiated. Ideally, the S11 value should be as low as possible, indicating that most of the energy is successfully radiated rather than reflected back.

[0046] Define return loss RL and input reflection coefficient S 11 , where Γ is the port reflection coefficient

[0047] S11=20lgΓ

[0048] RL=-S11

[0049] The S21 parameter describes the gain or loss of a signal when it passes through an antenna, which is crucial in determining the transmission efficiency of the antenna.

[0050] When the antenna has two or more feeding ports, the mutual coupling between the ports needs to be considered, which is generally characterized by port isolation (Iso). It can be calculated using S parameters:

[0051] Iso=-20log|S21|

[0052] The general requirement for antenna port isolation is at least greater than 25dB.

[0053] Comparison of the input reflection coefficient S11 simulation results of the cross-dipole broadband antenna provided by the embodiment of the present invention and the first-order Sierpinski fractal structure Figure 6 As shown, the two curves show a high degree of consistency in overall trend and direction, with only slight differences between the two curves. The S11 value of the first-order Sierpinski-like fractal structure reaches its lowest point at 1.92GHz, and the S11 value of the quarter-circle fractal structure reaches its lowest point at 1.94GHz. The resonance point of the quarter-circle fractal structure is closer to the preset antenna operating frequency of 2GHz. In addition, the overall S11 value of the quarter-circle fractal structure is lower than that of the first-order Sierpinski-like fractal structure, which shows that the use of the quarter-circle fractal structure improves the antenna impedance matching state, more energy is radiated by the antenna instead of reflected, and the radiation efficiency of the antenna is improved.

[0054] The simulation results of the forward transmission coefficient S21 of the cross-dipole broadband antenna provided by the embodiment of the present invention and the first-order Sierpinski fractal structure are as follows: Figure 7 As shown, the S21 curve change trend and concavity of the quarter-circle fractal structure and the first-order S-fractal structure mentioned in the present invention are almost the same, and the numerical values ​​also have obvious homogeneity. The two curves first decrease and then increase, and the two-port isolation of the two fractal structures is greater than 25dB in the 1.5GHz~2.80GHz frequency band, and the influence of mutual coupling between ports is weak. However, in the 1.93GHz-2.64GHz frequency band, the S21 curve value under the quarter-circle fractal structure is slightly lower than that of the first-order S-fractal structure, showing the slight superiority of the quarter-circle in the indicator of port isolation.

[0055] In order to explore the influence of balun on antenna performance, the broadband cross-dipole antenna with balun structure and the broadband cross-dipole antenna without balun structure were simulated respectively.

[0056] As a balanced-to-unbalanced converter, balun is mainly used to convert and match between balanced and unbalanced circuits, because it ensures that the signal amplitudes at the two feeding points of the antenna are equal and the phases are opposite, thereby optimizing the performance of the antenna. Through the design of balun, the impedance ratio between the unbalanced end and the balanced end can be adjusted to maximize the output power of the signal source transmitted to the antenna, thereby improving the overall efficiency of the system.

[0057] Balun can effectively improve the performance of the antenna. Balun can eliminate the adverse effects of unbalanced feeding on antenna radiation. By eliminating imbalance, it can reduce radiation loss, improve the directivity pattern, and correct the maximum radiation direction. Balun can solve the problem of mismatch between antenna input impedance and feeder characteristic impedance.

[0058] A comparison of return loss simulations of a broadband cross dipole antenna with a balun structure and a broadband cross dipole antenna without a balun structure provided by an embodiment of the present invention is shown in FIG. Figure 8 As shown in the figure, the -15dB impedance bandwidth of the cross-dipole antenna without a balun structure covers 1.77GHz to 2.80GHz, and the lowest point of the return loss is around -24dB; the -15dB impedance bandwidth of the cross-dipole antenna with a balun structure covers 1.81GHz to 2.80GHz, and the lowest point of the return loss is around -44dB; there is no obvious change in the impedance bandwidth of the two; the S11 curve shows an overall downward trend after adding the balun structure, and the return loss values ​​of the first resonance point and the second resonance point both decrease, which means that the balun improves the impedance matching between the antenna and the feeder, that is, the energy reflected back to the source end is reduced, the energy lost by the antenna system is reduced, and the energy transmission efficiency is high, which meets the requirements of wide beam communication of drone antennas.

[0059] The comparison of port isolation simulation when the broadband cross dipole antenna provided by the embodiment of the present invention is provided with a balun structure and the broadband cross dipole antenna is provided without a balun structure. Fig. 9 As shown in the figure, the bandwidth of the two-port isolation S21 less than -25dB without the balun structure covers the frequency band of 1.71GHz to 2.80GHz, with the lowest point at -27.4dB. After adding the balun structure, the two-port isolation coverage bandwidth is expanded and the lowest point is at -32.4dB, which means that the balun structure reduces the interference between ports 1 and 2, and the mutual coupling between ports 1 and 2 is further reduced. In addition, the energy loss transmitted from port 1 to port 2 is reduced, indicating that the balun structure has improved the transmission efficiency.

[0060] The antenna pattern is a three-dimensional image that describes the field or power (proportional to the square of the field) as a function of the spherical coordinates θ and φ, which can represent the antenna's ability to receive and transmit electromagnetic waves in space. It can be represented by a cross-sectional view of the axis containing the main lobe. The main beam (main lobe) of the pattern radiates along the z-axis, which is the direction of maximum radiation; the other lobes are side lobes (side lobes or back lobes). The smaller the side lobe, the more concentrated the antenna radiation power. The larger the side lobe, the greater the antenna's backward radiation, which weakens the radiation in the direction of the antenna's main lobe and causes antenna gain loss.

[0061] Half-power beamwidth, also known as 3dB beamwidth, is the angle between two points with half-power level values ​​in the power pattern when the power is half of the maximum value. The formula is:

[0062] HPBW=|θ left -θ right |θ left ;

[0063] Represents the angle of the left point at 0.5 in the power pattern. right Represents the angle of the right point at 0.5 in the normalized power pattern

[0064] HPBW is used to reflect the directivity of the antenna and is of great significance. The smaller the HPBW value, the more concentrated the antenna energy is.

[0065] The antenna radiation pattern is divided into E-plane radiation pattern and H-plane radiation pattern. The basis for the division is that the plane where the electric lines are located is the E-plane, and the plane where the magnetic lines are located is the H-plane. The EH-plane radiation pattern shows the radiation characteristics and radiation pattern of the antenna.

[0066] The EH surface simulation results of the broadband cross dipole antenna provided by the embodiment of the present invention with a balun structure are as follows: Fig.10 As shown, the antenna radiation pattern with the balun structure shows good symmetry; the half-power beamwidth of the E-plane and H-plane at the center frequency of 2GHz are both 72°, and the radiation range is wide.

[0067] The EH plane simulation results of the broadband cross dipole antenna provided by the embodiment of the present invention without a balun structure are as follows: Fig.11 As shown in the figure, the half-power beamwidth of the E-plane and H-plane at the center frequency of 2GHz is 68°, and the radiation range is reduced compared to the broadband cross-dipole antenna with a balun structure. The side lobe of the antenna pattern without a balun structure shifts to the left, and a new side lobe appears at theta equals 120°.

[0068] 3D patterns graphically show how strongly an antenna radiates at different spatial angles. Such patterns are usually based on a spherical coordinate system, where the antenna is at the center and the sphere around it represents the radiation intensity at different angles. 3D patterns are essential for evaluating and optimizing antenna performance because they provide a comprehensive view of how the antenna radiates energy in all directions.

[0069] The directivity pattern is used to qualitatively describe the directivity of the antenna. It is a rough description. There is another indicator to quantitatively and accurately describe the antenna. This indicator is the directivity coefficient and gain. Through the directivity coefficient and gain, the energy concentration of different antennas can be easily compared.

[0070] The directivity coefficient is defined as: the ratio of the maximum radiated power density of the antenna to the average value of the radiated power density of the entire antenna at a solid angle of 4π. The resulting value is the directivity coefficient. The formula is as follows:

[0071]

[0072] Where S max is the maximum radiation power density, P r is the total radiated power of the antenna.

[0073] If the antennas have the same input power, then the ratio of the target antenna in the maximum radiation direction to the isotropic antenna is the multiple of the power increase, which is the directivity coefficient. The directivity coefficient of an omnidirectional antenna is 1, which means it has no directivity. However, general antennas are directional, and their directivity coefficients are generally greater than 1.

[0074] From the perspective of describing the degree of antenna energy concentration, the antenna gain and antenna directivity are the same property. However, there is a slight difference between the two. The comparison benchmark of gain is the total input energy of the antenna.

[0075] So the gain factor of the antenna is: compare the maximum radiated power density of the antenna with the average value of the input power of the entire antenna at a solid angle of 4π, and the value obtained is the gain factor. So for the directivity coefficient and gain, they need to be multiplied by a radiation efficiency η. If the antenna can achieve 100% radiation efficiency, that is, all net input energy is radiated, then the gain of the antenna is equal to the directivity coefficient. If the radiation efficiency of the antenna cannot reach 100%, then the gain will be less than the directivity coefficient.

[0076] The radiation efficiency η is the radiated power of the antenna divided by the net input power of the antenna. In the following formula, Pin is the net input power received by the antenna from the RF front end.

[0077]

[0078] So the gain of the antenna is

[0079]

[0080] The gain reflects that for the antenna, not all the net input energy received from the front end is radiated, but some energy is lost in the antenna.

[0081] The simulation results of the broadband cross-dipole 3D pattern with a balun structure provided by the embodiment of the present invention are as follows: Fig.12 As shown, the simulation results of the broadband cross-dipole 3D pattern without balun structure provided by the embodiment of the present invention are as follows Fig.13 , Fig.12 and Fig.13 By comparison, it can be seen that the balun structure will not have a significant impact on the radiation and gain of the antenna. Without the balun structure, the gain of the broadband cross dipole only drops from 7.98dB to 7.93dB.

[0082] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A cross-dipole broadband antenna, characterized in that: include: Substrate, balun structure, crossed dipole patch, metal reflector and two coaxial cables; The cross-dipole patch includes a first dipole patch unit and a second dipole patch unit, and the first dipole patch unit and the second dipole patch unit each include two metal sheets, the two metal sheets of the first dipole patch unit and the second dipole patch unit are respectively connected to each other by a first metal strip and a second metal strip, the first dipole patch unit and the second dipole patch unit are cross-placed on the substrate, and the first metal strip and the second metal strip are perpendicular to each other, so that the first dipole patch unit and the second dipole patch unit are rotationally symmetrically distributed on the substrate; wherein the shape of the metal sheet is a splicing of a three-quarter circle sector composed of two straight line segments and an arc segment and a square, and two adjacent sides of the square completely overlap with the two straight line segments, and the sector area of ​​the metal sheet has three circular hollow openings, which are respectively located in each sub-area after the sector area is divided into three equal parts, with the midpoint of the bisector of each sub-area as the center of the circle and the radius of the three-quarter circle as the diameter; The balun structure includes a bottom plate and two conductive columns; wherein the bottom plate is placed above the metal reflector, one end of the two conductive columns is respectively connected to one side of the bottom plate, and the other end is respectively connected to the first and second dipole patch units; One end of the two coaxial cables is connected to the bottom plate respectively, and the other end is connected to the first and second dipole patch units respectively.

2. The cross-dipole broadband antenna according to claim 1, characterized in that: The connection parts between one end of the two conductive pillars and one side of the bottom plate are both rounded.

3. The cross-dipole broadband antenna according to claim 1, characterized in that: The two coaxial cables each include an inner conductor and an outer conductor, which are respectively connected to the two metal sheets of the first and second dipole patch units in a one-to-one correspondence.

4. The cross-dipole broadband antenna according to claim 1, characterized in that: The lengths of the two conductive pillars are both one-quarter of the length of the transmission line.

5. The cross-dipole broadband antenna according to claim 1, characterized in that: Vertical metal plates are arranged around the metal reflector.

6. The cross-dipole broadband antenna according to claim 1, characterized in that: The substrate is made of glass_PTFEreinf material.

7. An unmanned aerial vehicle system, characterized in that: It comprises a drone and a cross-dipole broadband antenna as described in any one of claims 1 to 6.

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