Filtering circularly polarized antenna with wide axial ratio bandwidth

Abstract

The invention provides a filtering circularly polarized antenna with a wide axial ratio bandwidth. The filtering circularly polarized antenna comprises a first dielectric plate, a second dielectric plate, a third dielectric plate and a fourth dielectric plate which are sequentially arranged in parallel from bottom to top, a metal reflecting plate is printed on the lower surface of the first dielectric plate; a feed network is printed on the lower surface of the second dielectric plate, a slotted metal ground is printed on the upper surface of the second dielectric plate, a feed port is formed in one side edge of the second dielectric plate, and the feed port is electrically connected with the feed network and the slotted metal ground; a second square patch and an octagonal parasitic microstrip line frame are printed on the upper surface of the third dielectric plate, and the octagonal parasitic microstrip line frame surrounds the outer side of the second square patch; and a first square patch is printed on the lower surface of the fourth dielectric plate. Through an interlayer coupling collaborative design, 2.3-5.0 GHz broadband circular polarization radiation and high gain characteristics are realized, and the antenna also has high out-of-band rejection capability and can effectively filter out-of-band clutter interference.

Description

Technical Field

[0001] This invention relates to the field of communication antennas, and more specifically to a filtered circularly polarized antenna with a wide axial ratio bandwidth. Background Technology

[0002] Modern 5G, satellite communications, and other next-generation communication systems place multiple stringent demands on antenna performance. Specifically, antennas need to cover multiple application frequency bands, such as 2.3-5GHz, to achieve broadband radiation; they also need to have a wide axial ratio bandwidth to ensure stable circular polarization characteristics; they need strong out-of-band suppression capabilities to filter clutter interference; and they also need to meet the structural requirements of miniaturization and integration of equipment.

[0003] However, existing antenna technologies still struggle to meet these requirements. For example, traditional broadband circularly polarized antennas often extend bandwidth through a single radiating structure, resulting in weak out-of-band suppression and susceptibility to external signal interference. Antennas with filtering capabilities, on the other hand, sacrifice axial ratio bandwidth and radiation efficiency to achieve out-of-band suppression due to insufficient coupling design between filtering and radiating structures. Furthermore, some multi-layer antennas suffer from frequency band overlap and reduced polarization purity due to unreasonable interlayer electromagnetic coupling. Other antennas rely on complex feeding or radiating structures for functional integration, increasing manufacturing complexity.

[0004] In summary, existing antennas cannot achieve continuous wide axial ratio bandwidth coverage within the critical 2.3-5GHz frequency band, and their out-of-band interference isolation is poor, making them unsuitable for the high-performance antenna requirements of 5G and satellite communications. Therefore, developing a filtered circularly polarized antenna with wide axial ratio bandwidth, high out-of-band suppression, and excellent radiation performance is crucial to overcoming the current performance bottleneck of communication system antennas. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a filtered circularly polarized antenna with a wide axial ratio bandwidth, which has the advantages of wide axial ratio bandwidth and high gain, while achieving filtering function without the need to introduce an additional filtering network.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a filtered circularly polarized antenna with a wide axial ratio bandwidth. Through interlayer coupling collaborative design, it achieves broadband circularly polarized radiation and high gain characteristics in the range of 2.3-5.0 GHz. At the same time, it also has high out-of-band suppression capability, which can effectively filter out clutter interference outside the frequency band. It can be widely used in communication systems such as 5G and satellite communication that require miniaturized high-performance antennas. Attached Figure Description

[0008] Figure 1 This is an exploded view of the structure of a filtered circularly polarized antenna with a wide axial ratio bandwidth provided in an embodiment of the present invention.

[0009] Figure 2 This is a schematic diagram of the upper surface structure of the second dielectric plate in an embodiment of the present invention.

[0010] Figure 3 This is a schematic diagram of the lower surface structure of the second dielectric plate in an embodiment of the present invention.

[0011] Figure 4 This is a schematic diagram of the upper surface structure of the third dielectric plate in an embodiment of the present invention.

[0012] Figure 5 This is a graph showing the reflection coefficient S11-frequency result under simulation conditions in an embodiment of the present invention.

[0013] Figure 6 This is a graph showing the shaft ratio-frequency results in a simulation state according to an embodiment of the present invention.

[0014] Figure 7 This is a gain-frequency result diagram of an embodiment of the present invention under simulation conditions.

[0015] Figure 8 This is an efficiency-frequency result graph of the embodiment of the present invention under simulation conditions.

[0016] Figure 9 This is the XOZ plane pattern of an embodiment of the present invention at a frequency of 3.7 GHz.

[0017] Figure 10 This is the YOZ plane radiation pattern of an embodiment of the present invention at a frequency of 3.7 GHz. Detailed Implementation

[0018] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] like Figure 1 As shown, an embodiment of the present invention provides a filtered circularly polarized antenna with a wide axial ratio bandwidth, comprising a first dielectric substrate 11, a second dielectric substrate 12, a third dielectric substrate 13 and a fourth dielectric substrate 14 arranged in parallel from bottom to top;

[0020] The lower surface of the first dielectric substrate 11 is printed with a metal reflector 2; the lower surface of the second dielectric substrate 12 is printed with a power supply network 3, the upper surface of the second dielectric substrate 12 is printed with a slotted metal ground 4, and a power supply port 5 is provided on one side of the second dielectric substrate 12. The power supply port 5 is electrically connected to the power supply network 3 and the slotted metal ground 4 and is used to supply power to the power supply network 3 and the slotted metal ground 4; the upper surface of the third dielectric substrate 13 is printed with a second square patch 62 and an octagonal parasitic microstrip wireframe 7, and the octagonal parasitic microstrip wireframe 7 surrounds the outside of the second square patch 62; the lower surface of the fourth dielectric substrate 14 is printed with a first square patch 61.

[0021] Combination Figure 2 As shown, the slotted metal ground 4 is a copper plate that completely covers the upper surface of the second dielectric plate. The slotted metal ground 4 has a slot pattern with a centrally symmetrical shape. The slot pattern includes interconnected square slot units 40, main shaft slot units 41, first branch slot units 421, second branch slot units 422, third branch slot units 423, fourth branch slot units 424, fifth branch slot units 425, sixth branch slot units 426, first bent slot units 431 and second bent slot units 432.

[0022] The square slot unit 40 is located in the center of the slotted metal base 4, and the center of the square slot unit 40 is the center of the entire slot pattern. The main axis slot unit 41 is arranged along the central axis of the square slot unit 40, with the midpoint of the main axis slot unit 40 coinciding with the center of the square slot unit 41. The two ends of the main axis slot unit 41 extend to the outside of the square slot unit 40 after perpendicularly intersecting the opposite sides of the square slot unit 40. One end of the first branch slot unit 421 is perpendicularly connected to one-third of the main axis slot unit 41, and the other end of the first branch slot unit 421 extends to the outside of the square slot unit 40 after perpendicularly intersecting the side of the square slot unit 40. The second branch slot unit 421 extends to the outside of the square slot unit 40. The second branch slot unit 422 is disposed outside the square slot unit 40 and parallel to the main shaft slot unit 41. The middle part of the second branch slot unit 422 is perpendicularly connected to the other end of the first branch slot unit 421. The third branch slot unit 423 is parallel to the main shaft slot unit 41 and perpendicularly intersects the first branch slot unit 421. One end of the third branch slot unit 423 perpendicularly intersects the side of the square slot unit 40 and extends to the outside of the square slot unit 40. The other end of the third branch slot unit 423 is located inside the square slot unit 40 and is connected to one end of the first bent slot unit 431. The first bent slot unit 431 and the third branch slot unit 423 are connected at a 135° angle.

[0023] The fourth branch slot unit 424 is arranged 180° rotationally symmetrically with the first branch slot unit 421, the fifth branch slot unit 425 is arranged 180° rotationally symmetrically with the second branch slot unit 422, the sixth branch slot unit 426 is arranged 180° rotationally symmetrically with the third branch slot unit 423, and the second bending slot unit 432 is arranged 180° rotationally symmetrically with the first bending slot unit 431; the center of rotational symmetry is the center of the square slot unit 40.

[0024] Combination Figure 3 As shown, the power supply network 3 includes a transmission microstrip line 31, a U-shaped microstrip line 32, a rectangular microstrip frame 33, and four diagonal microstrip lines 34. The rectangular microstrip frame 33 is disposed in the middle of the lower surface of the second dielectric substrate 12, and the center of the rectangular microstrip frame 33 is aligned with the center of the square slot unit 40 in the slotted metal ground 4. Each of the four inner corners of the rectangular microstrip frame 33 is connected to a diagonal microstrip line 34, and one end of each diagonal microstrip line 34 is connected to the side of the rectangular microstrip frame 33 at a 45° angle. The other end of the corner microstrip line 34 is respectively set towards the center of the rectangular microstrip frame 33; the transmission microstrip line 31 is generally L-shaped, including a main body segment and a bending segment connected vertically. The main body segment is set along the central axis of the rectangular microstrip frame 33 and is perpendicular to the main shaft slot unit 41 in the slotted metal ground 4. One end of the main body segment is set at one side edge of the second dielectric plate 12 and connected to the feed port 5 on the side of the second dielectric plate 12. The other end of the main body segment passes through the entire rectangular microstrip frame 33 and is perpendicularly connected to the bending segment.

[0025] The U-shaped microstrip line 32 is located near the side of the power supply port 5 and includes a bottom segment and two parallel segments. The bottom segment is perpendicularly connected to the main body segment of the transmission microstrip line 31. The two parallel segments are respectively located on both sides of the main body segment of the transmission microstrip line 31 and are perpendicularly connected to the two ends of the bottom segment. The ends of the two parallel segments extend to the side of the power supply port 5.

[0026] Combination Figure 4 As shown, the second square patch 62 is disposed at the center of the third dielectric substrate 13, and the octagonal parasitic microstrip frame 7 surrounds the second square patch 62, with the centers of the two coinciding.

[0027] Furthermore, the centers of the first square patch 61, the second square patch 62, and the octagonal parasitic microstrip frame 7 are all aligned with the center of the square slot unit 40 on the slotted metal ground 4, and the side length of the second square patch 62 is greater than the side length of the first square patch 61.

[0028] In this embodiment, the dielectric constant of the first dielectric plate 11, the second dielectric plate 12, the third dielectric plate 13, and the fourth dielectric plate 14 is 2.6, and the thickness is 1.524 mm. The first dielectric plate 11, the second dielectric plate 12, the third dielectric plate 13, and the fourth dielectric plate 14 are all square, wherein the side length of the first dielectric plate 11 is 130 mm, the side length of the second dielectric plate 12 is 45.4 mm, and the side lengths of the third dielectric plate 13 and the fourth dielectric plate 14 are both 84 mm. The slotted metal ground 4 completely covers the upper surface of the second dielectric plate 12, and its side length is equal to that of the second dielectric plate 12. The metal reflector 2 completely covers the lower surface of the first dielectric plate 11, and its side length is equal to that of the first dielectric plate 11.

[0029] In operation, the feed signal is input from the feed port 5 on the side of the second dielectric substrate 12, and excites the slotted metal ground 4 to generate initial radiation through the transmission microstrip line 31. Simultaneously, the rectangular microstrip frame 33, the diagonal microstrip line 34, and the U-shaped microstrip line 32 constitute an integrated filter network, achieving matching within the passband and generating transmission zeros outside the passband, thus realizing broadband circular polarization filtering. Specifically, the bent section of the transmission microstrip line 31 is used for impedance matching and feed point positioning; the rectangular microstrip frame 33 serves as a resonator, generating transmission zeros and improving the antenna's out-of-band suppression performance; the diagonal microstrip line 34 is used to further improve the antenna's out-of-band suppression performance; and the U-shaped microstrip line 32, as another resonant unit, works in conjunction with the rectangular microstrip frame 33 to further shape the filtering response.

[0030] The rotationally symmetrical slit pattern on the upper surface of the second dielectric plate 12 and the asymmetric feeding network layout on the lower surface of the second dielectric plate 12 disrupt the symmetry of the radiation structure, thereby exciting two orthogonal modes with equal amplitude and a 90° phase difference, thus generating a circularly polarized wave and contributing to the broadband characteristics.

[0031] Furthermore, the second square patch 62 on the upper surface of the third dielectric substrate 13 resonates and participates in radiation through near-field coupling excitation via the slotted metal ground 4, serving as the primary driving radiating patch; the octagonal parasitic microstrip wireframe 7 is used to introduce a resonant point in the low-frequency band of gain, achieving out-of-band suppression in the low-frequency band. The first square patch 61 on the lower surface of the fourth dielectric substrate 14 serves as an upper-layer parasitic radiator, further optimizing impedance matching and radiation pattern through electromagnetic coupling with the lower-layer second square patch 62, and contributing to high-frequency radiation. The metal reflector 2 on the lower surface of the first dielectric substrate 11 is used to shield the antenna's back radiation, improving forward gain and front-to-back ratio, while the resonant cavity effect formed by it and the upper-layer radiating structure helps to extend the bandwidth.

[0032] Specifically, the dimensional design of this embodiment of the invention is as follows:

[0033] In the slot pattern of the slotted metal ground 4, the main shaft slot unit 41 has a length of 22.3 mm and a width of 0.76 mm; the square slot unit 40 has a side length of 18.9 mm and a width of 0.3 mm; the first branch slot unit 421 and the fourth branch slot unit 424 have a length of 13.4 mm and a width of 0.76 mm; the second branch slot unit 422 and the fifth branch slot unit 425 have a length of 14.8 mm and a width of 0.76 mm; the third branch slot unit 423 and the sixth branch slot unit 426 have a length of 16.9 mm and a width of 0.76 mm; the first bent slot unit 431 and the second bent slot unit 432 have a length of 2 mm and a width of 0.76 mm.

[0034] In the power supply network 3, the main body segment of the transmission microstrip line 31 has a length of 29.2 mm and a width of 4.5 mm; the bent segment of the transmission microstrip line 31 has a length of 9 mm and a width of 2.6 mm; the side length of the rectangular microstrip frame 33 is 10.8 mm; the length of the diagonal microstrip line 34 is 3 mm and the width is 0.8 mm; the bottom segment of the U-shaped microstrip line 32 has a length of 7 mm, the parallel segment has a length of 4 mm, and the width of each segment is 1 mm.

[0035] Furthermore, the second dielectric substrate 12 is disposed 11.2 mm above the first dielectric substrate 11, the third dielectric substrate 13 is disposed 5.5 mm above the second dielectric substrate 12, and the fourth dielectric substrate 14 is disposed 10.1 mm above the third dielectric substrate 13. The height of the air layer (or the filling material with low dielectric constant) between the dielectric substrates is a key parameter for adjusting the coupling strength between the multilayer structures, directly affecting the antenna's operating bandwidth, axial ratio performance, and filtering characteristics.

[0036] Based on the above size design, the embodiments of the present invention can achieve excellent performance in the 2.3-5GHz frequency band.

[0037] Figure 5 The figure shows the reflection coefficient S11-frequency result of the embodiment of the present invention under simulation. As can be seen from the figure, when the power supply is applied, the working bandwidth of S11<-10dB in the embodiment of the present invention is 2.01-5.45GHz, and the relative bandwidth is 89.8%, which can achieve a relatively wide bandwidth.

[0038] Figure 6 The figure shows the shaft ratio-frequency results of the embodiment of the present invention under simulation. As can be seen from the figure, the working bandwidth of the embodiment of the present invention with a shaft ratio AR < 3dB is 2.3-5.0GHz, and the relative bandwidth is 74.1%. This working frequency band overlaps with the working bandwidth of S11 < -10dB, that is, circular polarization radiation is achieved in the range of 2.3-5.0GHz.

[0039] Figure 7This is a gain-frequency result diagram of the embodiment of the present invention under simulation. As can be seen from the diagram, the peak gain of the embodiment of the present invention is 9.45 dBi, while the low-frequency out-of-band rejection is greater than 21 dB and the high-frequency out-of-band rejection is greater than 16 dB. That is, without adding an additional filter, a good filtering function can be achieved, reducing the complexity of the antenna.

[0040] Figure 8 The figure shows the efficiency-frequency results of the embodiment of the present invention under simulation. As can be seen from the figure, the efficiency of the embodiment of the present invention is above 91% within the working frequency band, and the efficiency outside the working frequency band is suppressed, thus achieving good filtering function.

[0041] Figure 9 and Figure 10 These are the normalized radiation patterns of the XOZ and YOZ planes of the embodiment of the present invention at a frequency of 3.7 GHz. As can be seen from the figures, the antenna of the embodiment of the present invention exhibits excellent directional radiation characteristics in both the XOZ and YOZ planes at a frequency of 3.7 GHz, and has good right-hand circular polarization purity in the main radiation region, with outstanding cross-polarization suppression capability.

[0042] In summary, the present invention provides a filtered circularly polarized antenna with a wide axial ratio bandwidth. Through interlayer coupling collaborative design, it achieves broadband circularly polarized radiation and high gain characteristics in the range of 2.3-5.0 GHz. At the same time, it also has high out-of-band suppression capability, which can effectively filter out clutter interference outside the frequency band. It can be widely used in communication systems such as 5G and satellite communication that require miniaturized high-performance antennas.

[0043] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A filtered circularly polarized antenna with a wide axial ratio bandwidth, characterized in that, It includes a first dielectric plate, a second dielectric plate, a third dielectric plate, and a fourth dielectric plate arranged in parallel from bottom to top; The lower surface of the first dielectric substrate is printed with a metal reflector; the lower surface of the second dielectric substrate is printed with a feed network, the upper surface of the second dielectric substrate is printed with a slotted metal ground, and a feed port is provided on one side of the second dielectric substrate. The feed port is electrically connected to the feed network and the slotted metal ground for feeding power to the feed network and the slotted metal ground; the upper surface of the third dielectric substrate is printed with a second square patch and an octagonal parasitic microstrip wireframe, the octagonal parasitic microstrip wireframe surrounding the outer side of the second square patch; the lower surface of the fourth dielectric substrate is printed with a first square patch. The slotted metal ground is a copper plate that completely covers the upper surface of the second dielectric plate. The slotted metal ground has a slot pattern in a centrally symmetrical shape. The slot pattern includes interconnected square slot units, main axis slot units, first branch slot units, second branch slot units, third branch slot units, fourth branch slot units, fifth branch slot units, sixth branch slot units, first bending slot units, and second bending slot units. The square slot unit is located in the middle of the slotted metal base, and the center of the square slot unit is the center of the entire slot pattern. The main axis slot unit is located along the central axis of the square slot unit, and the midpoint of the main axis slot unit coincides with the center of the square slot unit. The two ends of the main axis slot unit intersect perpendicularly with the opposite two sides of the square slot unit and extend to the outside of the square slot unit. One end of the first branch slot unit is perpendicularly connected to one-third of the main axis slot unit, and the other end of the first branch slot unit intersects perpendicularly with the side of the square slot unit and extends to the outside of the square slot unit. The second branch slot unit is disposed outside the square slot unit and parallel to the main axis slot unit, and the middle part of the second branch slot unit is perpendicularly connected to the other end of the first branch slot unit; the third branch slot unit is parallel to the main axis slot unit and perpendicularly intersects the first branch slot unit, one end of the third branch slot unit perpendicularly intersects the side of the square slot unit and extends to the outside of the square slot unit, and the other end of the third branch slot unit is located inside the square slot unit and connected to one end of the first bent slot unit; the first bent slot unit and the third branch slot unit are connected at a 135° angle; The fourth branch slot unit is arranged 180° rotationally symmetrically with the first branch slot unit, the fifth branch slot unit is arranged 180° rotationally symmetrically with the second branch slot unit, the sixth branch slot unit is arranged 180° rotationally symmetrically with the third branch slot unit, and the second bent slot unit is arranged 180° rotationally symmetrically with the first bent slot unit; the center of rotational symmetry is the center of the square slot unit. The power supply network includes a transmission microstrip line, a U-shaped microstrip line, a rectangular microstrip frame, and four diagonal microstrip lines. The rectangular microstrip frame is located in the middle of the lower surface of the second dielectric substrate, and its center is aligned with the center of the square slot cell in the slotted metal ground. Each of the four inner corners of the rectangular microstrip frame is connected to a diagonal microstrip line, one end of which is connected to the side of the rectangular microstrip frame at a 45° angle, and the other end of which is directed toward the center of the rectangular microstrip frame. The transmission microstrip line is L-shaped and includes a vertically connected main body segment and a bending segment. The main body segment is located along the central axis of the rectangular microstrip frame and is perpendicular to the main shaft slot cell in the slotted metal ground. One end of the main body segment is located at one edge of the second dielectric substrate and is connected to the power supply port on the side of the second dielectric substrate. The other end of the main body segment passes through the entire rectangular microstrip frame and is perpendicularly connected to the bending segment. The U-shaped microstrip line is located near the side of the power supply port and includes a bottom segment and two parallel segments. The bottom segment is perpendicularly connected to the main body segment of the transmission microstrip line. The two parallel segments are respectively located on both sides of the main body segment of the transmission microstrip line and are perpendicularly connected to the two ends of the bottom segment. The ends of the two parallel segments extend to the side where the power supply port is located.

2. The filtered circularly polarized antenna with a wide axial ratio bandwidth according to claim 1, characterized in that, The centers of the first square patch, the second square patch, and the octagonal parasitic microstrip wireframe are all aligned with the center of the square slot cell, and the side length of the second square patch is greater than the side length of the first square patch.

3. The filtered circularly polarized antenna with a wide axial ratio bandwidth according to claim 1, characterized in that, The second dielectric plate is disposed 11.2 mm above the first dielectric plate, the third dielectric plate is disposed 5.5 mm above the second dielectric plate, and the fourth dielectric plate is disposed 10.1 mm above the third dielectric plate.

4. The filtered circularly polarized antenna with a wide axial ratio bandwidth according to claim 3, characterized in that, The dielectric constant of the first dielectric substrate, the second dielectric substrate, the third dielectric substrate, and the fourth dielectric substrate is 2.6, and the thickness is 1.524 mm.

5. The filtered circularly polarized antenna with a wide axial ratio bandwidth according to claim 1, characterized in that, The first, second, third, and fourth dielectric plates are all square, with the first dielectric plate having a side length of 130 mm, the second dielectric plate having a side length of 45.4 mm, and the third and fourth dielectric plates each having a side length of 84 mm. The slotted metal ground completely covers the upper surface of the second dielectric plate, and its side length is equal to that of the second dielectric plate. The metal reflector completely covers the lower surface of the first dielectric plate, and its side length is equal to that of the first dielectric plate.

6. The filtered circularly polarized antenna with a wide axial ratio bandwidth according to claim 1, characterized in that, In the slot pattern of the slotted metal base, the main axis slot unit has a length of 22.3 mm and a width of 0.76 mm; the square slot unit has a side length of 18.9 mm and a width of 0.3 mm; the first branch slot unit and the fourth branch slot unit have a length of 13.4 mm and a width of 0.76 mm; the second branch slot unit and the fifth branch slot unit have a length of 14.8 mm and a width of 0.76 mm; the third branch slot unit and the sixth branch slot unit have a length of 16.9 mm and a width of 0.76 mm; and the first bend slot unit and the second bend slot unit have a length of 2 mm and a width of 0.76 mm.

7. The filtered circularly polarized antenna with a wide axial ratio bandwidth according to claim 6, characterized in that, In the power supply network, the main body segment of the transmission microstrip line is 29.2 mm long and 4.5 mm wide; the bent segment of the transmission microstrip line is 9 mm long and 2.6 mm wide; the side length of the rectangular microstrip frame is 10.8 mm; the length of the diagonal microstrip line is 3 mm and the width is 0.8 mm; the bottom segment of the U-shaped microstrip line is 7 mm long, the parallel segment is 4 mm long, and the width of each segment is 1 mm.

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