A conical spiral antenna with good beam stability

Abstract

The present invention discloses a conical spiral antenna with good beam stability, which includes a radiation structure, a feeding balun structure for feeding the radiation structure, and a metal cavity structure filled with absorbing material. The feeding balun structure includes a strip line part, a transition part, and a parallel twin line part. On both sides of the strip line part are metallized vias. The lower part of the strip line part is connected to a coaxial line, and the upper part is connected to the transition part. In the transition part, the two-layer floors of the strip line part are connected through a metallization process, and one of the floors is truncated. The middle strip line is semicircular and bypasses the metallized vias. The lower part of the parallel twin line part is connected to the transition part, and the upper part is connected to the top of the radiation structure. The present invention realizes the conversion from unbalanced to balanced feeding and impedance matching, reduces the influence of electromagnetic energy leakage on the radiation of the spiral line, thereby ensuring that the conical spiral antenna has the performance of a relatively wide axial ratio beam width.

Description

Technical Field

[0001] The present invention belongs to the technical field of antenna engineering, and particularly relates to wireless communication devices for aerospace vehicles, and specifically relates to a conical helix antenna with good beam stability. Background Art

[0002] Circularly polarized antennas can receive or radiate electromagnetic waves of any polarization, and thus are widely used in fields such as positioning, navigation, and communication. Common circularly polarized antennas include helix antennas, microstrip antennas, and cross-shaped symmetric dipole antennas, etc. Among them, helix antennas also belong to traveling wave antennas and can achieve good circular polarization characteristics within a wide frequency band. They are mainly divided into two forms: planar helix antennas and conical helix antennas. Their lowest operating frequency point is limited by the requirements of the maximum antenna size, while the highest operating frequency point is mainly limited by the feed design and processing accuracy. Compared with planar helix antennas, conical helix antennas have electrical properties such as higher radiation efficiency and larger power beam width; however, when the operating frequency band covers the X-band or even the Ku-band, the processing technology requirements and assembly process of conical helix antennas become more complex and difficult. Therefore, exploring a technical solution for conical helix antennas that can cover the Ku-band and ensure excellent radiation performance is crucial for the practical application of conical helix antennas.

[0003] When designing a conical helix antenna under a certain maximum size limit, techniques for optimizing the helix shape are usually adopted, including combining the Archimedes spiral and the equiangular spiral, bending and winding the helix, etc., which can effectively extend the current path and expand the low-frequency bandwidth; at the same time, methods of adding resistive materials are also used, including welding a resistive element at the end of the helix to dissipate the reflected current at the end, and placing an absorbing material 30 under the helix to absorb the electromagnetic energy reflected from the floor, which can improve the axial ratio performance within the entire operating frequency band. Although conical helix antennas have excellent circular polarization performance, there are still some core problems to be solved. On the one hand, since the feed balun of the conical helix antenna will interact with the helix while feeding the helix, it will cause the radiation performance of the antenna to deteriorate, specifically mainly manifested as an asymmetric far-field pattern and a significant reduction in the axial ratio beam width. On the other hand, at the high-frequency end of the operating frequency band, because the distance between the main radiation area of the helix and the floor is much greater than one-quarter of the wavelength, the electromagnetic energy reflected from the floor cancels out the radiated electromagnetic energy in some areas of the far field, so obvious depressions will appear in the far-field pattern in these canceling areas, and the radiation efficiency will also decrease. Therefore, these two main problems must be solved for conical helix antennas to simultaneously possess the performance of a wide frequency band, a large power beam width, a large axial ratio beam width, and high radiation efficiency. Summary of the Invention

[0004] The object of the present invention is to provide a conical spiral antenna with good beam stability, adopting a feeding balun structure that converts a strip line to a parallel two-wire line. This feeding balun structure can not only achieve the conversion from unbalanced feeding to balanced feeding and impedance matching, but more importantly, it has good sealing performance, which can effectively reduce the influence of electromagnetic energy leakage on the radiation of the spiral line, thereby ensuring that the conical spiral antenna has the performance of a relatively wide axial ratio beam width and can cover the X-band and Ku-band.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A conical spiral antenna with good beam stability, comprising a radiation structure 00, a feeding balun structure 10 for feeding the radiation structure 00, and a metal cavity structure 40 filled with an absorbing material 30. The radiation structure is arranged above the metal cavity structure 40; the feeding balun structure 10 is vertically placed above the center of the metal cavity structure 40, and a coaxial line 50 passes through the bottom of the metal cavity structure 40 and is connected to the feeding balun structure, where:

[0007] The feeding balun structure 10 includes a strip line part 13, a transition part 12, and a parallel two-wire part 11; on both sides of the strip line part 13 are metallized vias. The lower part of the strip line part 13 is connected to the coaxial line 50, and the upper part of the strip line part 13 is connected to the transition part 12; in the transition part 12, the two floors of the strip line part are connected through a metallization process, and one of the floors is truncated. The middle strip line is semicircular and bypasses the metallized vias; the lower part of the parallel two-wire part 11 is connected to the transition part 12, and the upper part of the parallel two-wire part 11 is connected to the top end of the radiation structure, that is, the top end of the spiral line.

[0008] Preferably, the radiation structure includes two spiral lines 00, and the two spiral lines 00 are symmetrically wound along the conical surface by rotating 180° around the antenna central axis. The end part of the spiral line is bent in a sine shape, and the degree of bending gradually increases.

[0009] Preferably, both of the two spiral lines are printed on the same dielectric board, and the dielectric board uses a Rogers-5880 material with a thickness of 0.127 mm.

[0010] Preferably, the width of the end part of the spiral line gradually becomes smaller.

[0011] Preferably, the absorbing material 30 filled in the metal cavity structure 40 is cylindrical, the diameter of the absorbing material 30 is equal to the inner diameter of the metal cavity structure 40, and the height is equal to the depth of the metal cavity structure 40; a cuboid is dug out at the middle position of the absorbing material 30, and the feeding balun structure 10 passes through the dug-out position of the absorbing material 30.

[0012] Preferably, a lossy material that can be more accurately represented by material parameters is used to replace the wave-absorbing material 30 to absorb electromagnetic waves.

[0013] Preferably, a metal ring 20 is placed at the center position of the upper surface of the wave-absorbing material 30, and the feeding balun structure 10 passes through the center of the metal ring 20.

[0014] Preferably, the entire feeding balun structure 10 is composed of two layers of Rogers-5880 material PCBs with a thickness of 0.127 mm, and a layer of prepreg material with a thickness of 0.101 mm is bonded in the middle.

[0015] The beneficial effects of the present invention are as follows:

[0016] On the one hand, the present invention uses a feeding balun structure that converts a stripline to a parallel two-wire to feed the radiation structure, which can effectively reduce the mutual influence between the feeding balun and the spiral, so as to maintain a relatively wide axial ratio beamwidth. This feeding balun structure can not only achieve the conversion from unbalanced to balanced feeding and impedance matching, but more importantly, it has good shielding, and can effectively reduce the influence of the leakage of electromagnetic energy on the radiation of the spiral.

[0017] On the other hand, the present invention places a metal ring above the metal cavity structure, which can reflect electromagnetic waves at the high-frequency end of the operating frequency band, can improve the problem of pattern depression in the high-frequency band, and at the same time improve the radiation efficiency in the high-frequency band, while having little impact on the performance in the low-frequency band.

[0018] Therefore, the operating frequency band of the conical spiral antenna provided by the present invention can cover the X-band and the Ku-band, and has good beam stability. Brief Description of the Drawings

[0019] Figure 1 is a three-dimensional structural schematic diagram of the conical spiral antenna.

[0020] Figure 2 is a front view of the three-dimensional structure of the conical spiral antenna.

[0021] Figure 3 is a top view of the three-dimensional structure of the conical spiral antenna.

[0022] Figure 4 is a front view of the three-dimensional structure of the feeding balun structure.

[0023] Figure 5 is a side view of the three-dimensional structure of the feeding balun structure.

[0024] Figure 6 is a front view of the three-dimensional structure of the metal cavity structure.

[0025] Figure 7 Top view of the three-dimensional structure of the metal cavity structure.

[0026] Figure 8 Is the standing wave ratio of the conical helix antenna port.

[0027] Figure 9 Is the radiation efficiency of the conical helix antenna.

[0028] Figure 10 Is the gain pattern of the conical helix antenna in the xoz plane.

[0029] Figure 11 Is the gain pattern of the conical helix antenna in the yoz plane.

[0030] Figure 12 Is the axial ratio of the conical helix antenna in the axial direction (θ = 0°).

[0031] Figure 13 Is the axial ratio of the conical helix antenna in the φ plane at θ = 30°.

[0032] Figure 14 Is the axial ratio of the conical helix antenna in the φ plane at θ = 50°.

[0033] In the figure: 00 is the helix, 10 is the feeding balun structure, 11 is the parallel two-wire part, 12 is the transition part, 13 is the strip line part, 20 is the metal ring, 30 is the absorbing material, 40 is the metal cavity structure, and 50 is the coaxial cable. Specific implementation manner

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] A conical helix antenna with good beam stability shown in this embodiment has a working frequency band of 3 octaves, a diameter of 1.5λh, and a profile height of 0.9λh. λh is the wavelength corresponding to the highest frequency point in vacuum. Its three-dimensional structure schematic diagram, front view and top view are respectively as Figures 1 - 3 shown, and can be regarded as consisting of three parts: one is the radiation structure, that is, two rotationally symmetric sinusoidally bent helices 00 coiled along the conical surface; the second is the feeding balun structure 10, which uses a strip line to convert to parallel two-wires to feed the radiation structure; the third is the metal cavity structure 40 filled with the absorbing material 30. The radiation structure is arranged above the metal cavity structure 40; the feeding balun structure 10 is vertically placed above the center of the metal cavity structure 40, and the coaxial cable 50 passes through the bottom of the metal cavity structure 40 and is connected to the feeding balun structure.

[0036] The front view and side view of the feeding balun structure 10 are respectively as Figures 4 - 5As shown in the figure, the feeding balun structure for converting a stripline to a parallel twin line includes three parts: a stripline part 13, a transition part 12, and a parallel twin line part 11. On both sides of the stripline part 13 are metallized vias. The lower part of the stripline part 13 is connected to the coaxial line 50, and the upper part of the stripline part 13 is connected to the transition part 12. In the transition part 12, the two-layer ground planes of the stripline part are connected through a metallization process, and one of the ground planes is truncated. The middle strip line is semicircular and bypasses the metallized via. The lower part of the parallel twin line part 11 is connected to the transition part 12, and the upper part of the parallel twin line part 11 is connected to the top end of the radiation structure, that is, the top end of the helix. In this embodiment, the feeding balun structure 10 as a whole is composed of two layers of Rogers-5880 material PCBs with a thickness of 0.127 mm, and a semi-cured sheet material with a thickness of 0.101 mm is bonded in the middle to jointly form the balun.

[0037] The radiation structure includes two helical lines 00. The two helical lines 00 are symmetrically wound along the conical surface by rotating 180° about the antenna central axis. The two helical lines are printed on the same dielectric board. In this embodiment, the dielectric board uses a Rogers-5880 material with a thickness of 0.127 mm. The end part of the helical line is bent in a sine shape, and the degree of bending gradually increases. The width of the end part of the helical line gradually decreases.

[0038] The metal cavity structure 40 is placed at the bottom of the helical line. The front view and top view of the metal cavity structure 40 are respectively as Figures 6 - 7 shown. It can be seen that an absorbing material 30 is filled in the metal cavity. The absorbing material 30 is cylindrical. The diameter of the absorbing material 30 is equal to the inner diameter of the metal cavity structure 40, and the height is equal to the depth of the metal cavity structure 40. A cuboid is dug out at the middle position of the absorbing material 30, and the feeding balun structure 10 passes through the dug-out position of the absorbing material 30. Because it is difficult to accurately represent the absorbing material 30 used in the actual processing and assembly process with material parameters, resulting in a certain difference between the processed physical object and the simulated model, this difference will cause the performance of the conical spiral antenna to deteriorate in most cases. Therefore, using other lossy materials that can be more accurately represented by material parameters, including but not limited to resistive plates, to replace the absorbing material 30 to absorb electromagnetic waves may improve this problem.

[0039] Optionally, a metal ring 20 is placed at the center position of the upper surface of the absorbing material 30, and the feeding balun structure 10 passes through the center of the metal ring 20. The metal ring 20 can play a role in reflecting electromagnetic waves at the high-frequency part of the working frequency band.

[0040] Figure 8is the voltage standing wave ratio of the conical spiral antenna port, which is less than 2 within the entire operating frequency band. Figure 9 is the radiation efficiency of the conical spiral antenna, which is greater than 50% within the entire operating frequency band. Figure 10 and 11 are the gain patterns of the conical spiral antenna in the xoz plane and the yoz plane respectively. It can be seen that the gain is basically greater than 0 dBi within the spatial range of θ = ±50°. Figure 12 is the axial ratio of the conical spiral antenna at the axis (θ = 0°), which is less than 3 dB within the entire operating frequency band. Figure 13 is the axial ratio of the φ plane when θ = 30°, and the axial ratio is basically less than 3 dB within the entire φ plane. Figure 14 is the axial ratio of the φ plane when θ = 50°, and the axial ratio is basically less than 4 dB within the entire φ plane.

[0041] In summary, a feeding balun structure that converts a stripline to a parallel two-wire line is used to feed the helix, which can effectively reduce the mutual influence between the feeding balun and the helix, thereby maintaining a relatively wide axial ratio beam width; in addition, placing a metal ring 20 above the metal cavity structure can improve the problem of pattern depression at high frequencies and increase the radiation efficiency in the high-frequency band.

[0042] It can be understood that for those of ordinary skill in the art, equivalent substitutions or changes can be made according to the technical solutions and inventive concepts of the present invention, and all such changes or substitutions should fall within the protection scope of the claims appended to the present invention.

Claims

1. A conical spiral antenna with good beam stability, comprising a radiation structure (00), a feeding balun structure (10) for feeding the radiation structure (00), and a metal cavity structure (40) filled with an absorbing material (30). The radiation structure is arranged above the metal cavity structure (40); the feeding balun structure (10) is vertically placed above the center of the metal cavity structure (40), and a coaxial cable (50) passes through the bottom of the metal cavity structure (40) and is connected to the feeding balun structure. It is characterized in that: The feeding balun structure (10) includes a strip line part (13), a transition part (12), and a parallel twin line part (11); on both sides of the strip line part (13) are metallized vias. The lower part of the strip line part (13) is connected to the coaxial cable (50), and the upper part of the strip line part (13) is connected to the transition part (12); in the transition part (12), the two layers of the floor of the strip line part are connected through a metallization process, and one layer of the floor is truncated. The middle strip line is semicircular and bypasses the metallized via; the lower part of the parallel twin line part (11) is connected to the transition part (12), and the upper part of the parallel twin line part (11) is connected to the top end of the radiation structure, i.e., the top end of the spiral.

2. The conical spiral antenna with good beam stability according to claim 1, characterized in that The radiation structure includes two spiral lines (00). The two spiral lines (00) are symmetrically wound along a conical surface by rotating 180° about the antenna central axis. The end part of the spiral is bent in a sine shape, and the degree of bending gradually increases.

3. The conical helical antenna with good beam stability according to claim 2, characterized in that The two spiral lines (00) are both printed on the same dielectric board, and the dielectric board uses a Rogers - 5880 material with a thickness of 0.127 mm.

4. A conical spiral antenna with good beam stability according to claim 2, characterized in that The width of the end part of the spiral line (00) gradually decreases.

5. A conical spiral antenna with good beam stability according to claim 1, characterized in that The absorbing material (30) filled in the metal cavity structure (40) is cylindrical. The diameter of the absorbing material (30) is equal to the inner diameter of the metal cavity structure (40), and the height is equal to the depth of the metal cavity structure (40); a cuboid is dug out at the middle position of the absorbing material (30), and the feeding balun structure (10) passes through the dug - out position of the absorbing material (30).

6. The conical spiral antenna with good beam stability according to claim 1, characterized in that Use a lossy material that can be more accurately represented by material parameters to replace the absorbing material (30) to absorb electromagnetic waves.

7. A conical spiral antenna with good beam stability according to claim 1, characterized in that A metal ring (20) is placed at the center position of the upper surface of the absorbing material (30), and the feeding balun structure (10) passes through the center of the metal ring (20).

8. A conical helical antenna with good beam stability according to claim 1, characterized in that The whole feeding balun structure (10) is composed of two - layer Rogers - 5880 material PCBs with a thickness of 0.127 mm, and a semi - cured sheet material with a thickness of 0.101 mm is bonded in the middle.

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