A three-band stacked circularly polarized antenna

Abstract

A three-frequency-band stacked circularly polarized antenna comprises first to third dielectric substrates arranged in a stack, a directional coupler in the form of a strip line, a strip line dielectric layer with upper and lower metal ground plates, and a coaxial feeding structure; the first to third radiation patches are respectively printed on the center positions of the first to third dielectric substrates; two different frequency bands are obtained through a set of feeding networks; the second and third radiation patches can radiate circularly polarized waves through the output ports of the directional coupler with a phase difference of 90°; the first radiation patch is located on the uppermost layer, and the coaxial line is used for feeding at the center point of the patch unit; when the first radiation patch works, the second radiation patch is used as the metal ground plate; a U-shaped slot and a cut corner are formed on the first radiation patch to widen the impedance bandwidth and improve the circular polarization performance; the antenna can be applied to the fields of microwave communication, navigation, electronic warfare, satellite communication, etc.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, and specifically relates to a three-band stacked circularly polarized antenna. Background Technology

[0002] With the rapid development of modern communication technology, spectrum resources are becoming increasingly scarce. Wireless communication systems and terminal devices are developing towards miniaturization and multi-band operation. This means that multiple different antennas must be placed in a limited space, resulting in particularly strong coupling and interference between antennas.

[0003] Microstrip patch antennas offer advantages such as small size, low profile, and ease of conformal design. Stacking multiple antennas can significantly reduce lateral space requirements. A suitable stacking design allows a single antenna to radiate three different frequency bands to achieve different functions, greatly improving antenna utilization. Meanwhile, circularly polarized waves possess advantages such as resistance to multipath fading and strong interference suppression capabilities, providing a stable link between transmitting and receiving antennas. They are now widely used in satellite communications, aerospace, GPS, and radar systems.

[0004] Traditional microstrip patch antennas are typically designed within a single plane. To prevent coupling interference between different antennas, multiple antennas with different frequency bands and functions often require a large space. Furthermore, to ensure circular polarization radiation for all multi-band antennas, a complex feed network is usually required, increasing manufacturing costs. For example, the tri-band microstrip antenna described in CN117832828A, which radiates three frequency bands, is designed within the same plane, resulting in a large planar area and an inability to achieve circular polarization radiation. Summary of the Invention

[0005] To overcome the shortcomings of the existing technology, the present invention aims to provide a three-band stacked circularly polarized antenna. By designing three antennas of different frequency bands in a stacked structure within the same aperture, the lateral size of the antenna is greatly reduced. A coaxial feed is used at the center of the first radiating patch unit, and a U-shaped slot and chamfer are made on the first radiating patch to give the antenna good circular polarization performance and impedance bandwidth. The second and third radiating patches are dual-fed through a directional coupler, and the energy power input at the two feed points is equal with a 90° phase difference, so that the radiating patches of different stacks radiate circularly polarized waves with different rotation directions, effectively broadening the applicability of the antenna.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A three-band stacked circularly polarized antenna includes a first dielectric substrate 4, a second dielectric substrate 5, a third dielectric substrate 6, and a stripline dielectric layer 7 stacked from top to bottom. A first radiating patch 1 is printed on the top of the first dielectric substrate 4, a second radiating patch 2 is printed on the top of the second dielectric substrate 5, and a third radiating patch 3 is printed on the top of the third dielectric substrate 6. A directional coupler 8 is disposed in the middle of the stripline dielectric layer 7. The energy input ports 18 of the directional coupler 8 are located on both sides of the stripline dielectric layer 7, and the energy output ports 17 of the directional coupler 8 are located on the center vertical lines of the mutually perpendicular sides of the stripline dielectric layer 7, and are equidistant from the center point of the stripline dielectric layer 7. The two energy input ports 18 of the directional coupler are fed through a coaxial line 10 and a second coaxial line 11. A coaxial feeding structure 12 passes through the center of the stripline dielectric layer 7, the third dielectric substrate 6, the second dielectric substrate 5, and the first dielectric substrate 4. The inner conductor 16 of the coaxial feeding structure is connected to the first radiating patch 1, and the outer conductor 19 of the coaxial feeding structure is connected to the second radiating patch 2.

[0008] The strip-shaped dielectric layer 7 is provided with an upper metal floor 14 and a lower metal floor 15 on its upper and lower sides, respectively. The upper metal floor 14 is the radiation floor of the second radiation patch 2 and the third radiation patch 3.

[0009] The first radiating patch 1, the second radiating patch 2, and the third radiating patch 3 are located at the center of the first dielectric substrate 4, the second dielectric substrate 5, the third dielectric substrate 6, and the stripline dielectric layer 7, respectively.

[0010] The directional coupler 8 leads a power supply probe 13 upward from the energy output port 17. The power supply probe 13 passes through the third dielectric substrate 6, the third radiating patch 3, the second dielectric substrate 5 and connects to the second radiating patch 2 in sequence.

[0011] The diameter of the hole through which the power supply probe 13 passes is greater than the cross-sectional diameter of the power supply probe 13, ensuring that the power supply probe 13 does not contact the third radiation patch 3 and preventing the power supply probe 13 from being short-circuited by the third radiation patch 3.

[0012] The directional coupler 8 is surrounded by a plurality of metallized vias 9, which connect the upper metal floor 14 and the lower metal floor 15 of the stripline dielectric layer 7.

[0013] The second radiating patch 2 and the third radiating patch 3 are both square; the first radiating patch 1 has a U-shaped gap 20 in the middle, and the two opposite corners of the first radiating patch 1 are chamfered.

[0014] The size of the third radiating patch 3 is larger than the size of the second radiating patch 2, and the size of the second radiating patch 2 is larger than the size of the first radiating patch 1.

[0015] The directional coupler 8 is a 3dB directional coupler in the form of a stripline.

[0016] The inner conductor 21 of the coaxial line is connected to the energy input port 18 of the directional coupler 8, and the outer conductor 22 of the coaxial line is connected to the lower metal ground plane 15 of the stripline dielectric layer 7.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. This invention uses a stacked structure to design the antenna and adopts a dielectric substrate with a relatively high permittivity. By stacking the antennas of three frequency bands in the same plane aperture, and placing the third and second radiating patches of lower frequency bands below the overall antenna structure, the size of the antenna is greatly reduced in the horizontal direction, thus expanding the applicability of the antenna.

[0019] 2. This invention uses a 3dB directional coupler in the form of a wire as the feeding network for a dual-band antenna. By using a dual-feed method to feed the antenna, and utilizing the power and phase characteristics of the input and output ports of the 3dB directional coupler, good and stable circular polarization performance can be achieved, which is beneficial for the antenna to achieve better anti-interference effect and improve communication quality.

[0020] 3. This invention utilizes an inter-antenna coupling feeding method. For the second and third radiating patches, only the second radiating patch 1 is double-fed. Through the coupling between the second radiating patch 1 and the third radiating patch 2, it can radiate circularly polarized electromagnetic waves with different rotation directions in two frequency bands, reducing the complexity of the feeding network design and lowering the cost of the antenna.

[0021] 4. The present invention utilizes the U-shaped slot 20 and the chamfer design. The capacitive reactance brought by the U-shaped slot 20 enables the first radiating patch 1 to have a good matching effect when center-fed. The micro-perturbation brought by the chamfer enables the antenna to have good circular polarization performance and ensures the relative symmetry between the first radiating patch 1 and the ground.

[0022] In summary, the antenna of this invention has good circular polarization performance and impedance bandwidth, effectively broadening the application range of the antenna. Attached Figure Description

[0023] Figure 1 This is a cross-sectional view of the structure of the present invention.

[0024] Figure 2 This is a schematic diagram of the overall structure of the present invention.

[0025] Figure 3 This is a schematic diagram of the planar structure of the 3dB directional coupler in this invention.

[0026] Figure 4 This is a diagram showing the antenna S-parameters and axial ratio of the present invention, wherein, Figure 4(a) is the S of the first radiation frequency band of the antenna. 11 Parameter curves Figure 4 (b) is the axial ratio curve of the first radiation band of the antenna.

[0027] Figure 5 This is a diagram showing the antenna S-parameters and axial ratio of the present invention, wherein, Figure 5 (a) is the S of the second radiation band of the antenna. 11 Parameter curves Figure 5 (b) is the axial ratio curve of the second radiation band of the antenna.

[0028] Figure 6 This is a diagram showing the antenna S-parameters and axial ratio of the present invention, wherein, Figure 6 (a) is the S of the third radiation band of the antenna. 11 Parameter curves Figure 6 (b) is the axial ratio curve of the third radiation band of the antenna.

[0029] Figure 7 This is the antenna gain diagram of the present invention, wherein, Figure 7 (a) shows the antenna's normal gain curve at 2.491 GHz. Figure 7 (b) shows the antenna's normal gain curve at 1.615 GHz. Figure 7 (c) shows the antenna's normal gain curve at 1.207 GHz.

[0030] In the figure: 1. First radiating patch; 2. Second radiating patch; 3. Third radiating patch; 4. First dielectric substrate; 5. Second dielectric substrate; 6. Third dielectric substrate; 7. Stripline dielectric layer; 8. Directional coupler; 9. Metallized via; 10. First coaxial line; 11. Second coaxial line; 12. Coaxial feed structure; 13. Feed probe; 14. Upper metal ground plane; 15. Lower metal ground plane; 16. Inner conductor of coaxial feed structure; 17. Energy output port; 17-1. First energy output port; 17-2. Second energy output port; 18. Energy input port; 18-1. First energy input port; 18-2. Second energy input port; 19. Outer conductor of coaxial feed structure; 20. U-shaped gap; 21. Inner conductor of coaxial line; 22. Outer conductor of coaxial line. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings.

[0032] like Figure 1 , Figure 2 , Figure 3As shown, the microstrip antenna provided by the present invention includes a first radiating patch 1 with a U-shaped slot and chamfer, a square second radiating patch 2 and a third radiating patch 3, a stacked three-layer dielectric substrate, a stripline dielectric layer 7, a 3dB directional coupler 8, and a coaxial feed structure 12.

[0033] The first radiating patch 1, the second radiating patch 2, and the third radiating patch 3 are respectively printed on the center positions above the first dielectric substrate 4, the second dielectric substrate 5, and the third dielectric substrate 6. A coaxial power supply structure 12 passes through the stripline dielectric layer 7, the second dielectric substrate 5, the third dielectric substrate 6, and the third radiating patch 3 from the center position of the dielectric substrate to supply power to the first radiating patch 1. The inner conductor 16 of the coaxial power supply structure is connected to the center of the first radiating patch 1, and the outer conductor 19 of the coaxial power supply structure is connected to the second radiating patch 2. The second radiating patch 2 serves as the metal ground plane for the first radiating patch 1 and the coaxial line.

[0034] The two opposite corners of the first radiating patch 1 are chamfered to obtain two orthogonal degenerate modes for circular polarization. A U-shaped slot 20 is made on both sides of its central symmetrical position to ensure good matching effect of the antenna when fed at the center point. After simulation optimization, the size of the first radiating patch 1 is 19.6mm × 19.4mm. The U-shaped slot 20 is located at the center of the first radiating patch 1, with a length of 11mm and a width of 1.2mm. The gap between the two arms of the U-shaped slot is 7mm, and the chamfer size is 4mm.

[0035] The stripline dielectric layer 7 is located directly below the third dielectric substrate 6, with metal ground planes printed on its top and bottom. The metal ground plane 14 on top will be used as the metal ground plane for the second radiating patch 2 and the third radiating patch 3. The dimensions of the stripline dielectric layer 7, the first dielectric substrate 4, the second dielectric substrate 5, and the third dielectric substrate 6 are all 60mm × 60mm. The thickness of the stripline dielectric layer 7 is 1.504mm, and the thickness of the first dielectric substrate 4, the second dielectric substrate 5, and the third dielectric substrate 6 is 5mm.

[0036] The stripline dielectric layer 7, the first dielectric substrate 4, and the second dielectric substrate 5 all use Rogers 6006 with a relative permittivity of 6.15, while the third dielectric substrate 6 uses Rogers 6010 with a relative permittivity of 10.2. Using a material with a higher relative permittivity than the second dielectric substrate 5 for the third dielectric substrate 6 allows the size of the third radiating patch 3 to be reduced to a size similar to that of the second radiating patch 2, resulting in better coupling between the two antennas. Specifically, the second radiating patch 2 has a size of 31.2mm × 31.2mm, and the third radiating patch 3 has a size of 31.9mm × 31.9mm, giving them similar dimensions.

[0037] The 3dB directional coupler 8 is designed as a dual-branch directional coupler in the form of a stripline within the stripline dielectric layer 7. To ensure its operation in stripline mode, the stripline trace is routed as far away from the edge of the stripline dielectric layer 7 as possible. Figure 2 As shown, the 3dB directional coupler 8 consists of two parallel main transmission lines, two coupling branch lines, and input and output striplines. The main transmission lines are quarter-wavelength striplines with a characteristic impedance of 35.4Ω, the coupling branch lines are quarter-wavelength striplines with a characteristic impedance of 50Ω, and the input and output striplines are both striplines of a certain length with a characteristic impedance of 50 ohms. Using a stripline calculation tool, it can be determined that the main transmission lines use striplines with a length of 21.6mm and a width of 0.95mm, and the coupling branch lines use striplines with a length of 21.6mm and a width of 0.43mm.

[0038] To prevent the 3dB directional coupler 8 from exhibiting a planar mode, such as Figure 1 As shown, as many metallized vias 9 as possible are made near the 3dB directional coupler 8 to connect the upper metal ground plane 14 and the lower metal ground plane 15 of the stripline dielectric layer 7. The radius of the metallized vias 9 is 0.225mm.

[0039] The input port of the 3dB directional coupler 8 is extended to both sides of the coupler. Its energy output ports 17 are located equidistant from the center on the midline of adjacent sides. Two 0.45mm diameter metal feed probes 13 are connected to two feed points on the second radiating patch 2. These feed points are located 6mm from the center on the midline of adjacent sides of the second radiating patch 2. The 3dB directional coupler 8 ensures that the patch receives equal amounts of energy from the two feed points with a 90° phase difference, thus achieving circular polarization. It is important to note that when the metal feed probe 13 passes through the metal ground plane 14 on the stripline dielectric layer and the third radiating patch 3, a 0.76mm diameter via (slightly larger than the metal probe size) is made at the feed probe 13 location to allow it to pass smoothly.

[0040] The working principle of this invention is:

[0041] The three radiating patches are designed in the same aperture using a stacked structure. The first radiating patch 1 has the highest operating frequency and the smallest size. It is printed on the top layer of the antenna unit. The second radiating patch 2 and the third radiating patch 3 are printed below it in a stacked structure and are used as the metal ground plane when the first radiating patch 1 is working.

[0042] The first radiating patch 1 is fed at its center using a coaxial cable, and is chamfered and has a U-shaped slot 20 to introduce perturbations so that it has a better impedance matching effect and radiates circularly polarized waves.

[0043] The second radiating patch 2 is fed upwards by two feeding probes 13 through the two output ports of the 3dB directional coupler 8. By utilizing the coupling between the second radiating patch 2 and the third radiating patch 3, the second radiating patch 2 and the third radiating patch 3 can radiate dual-band dual circularly polarized waves.

[0044] The 3dB directional coupler 8 is designed using a stripline configuration. Its two energy input ports 18 function as two antenna ports, while the energy output port 17 feeds the antenna. When energy is input through the first energy input port 18-1, the energy at the first energy output port 17-1 is equal in magnitude and 90° phase-leading with the energy at the second energy output port 17-2, allowing the antenna to radiate lower-frequency left-hand circularly polarized waves. When energy is input through the second energy input port 18-2, the energy at the first energy output port 17-1 is equal in magnitude and 90° phase-laging with the energy at the second energy output port 17-2, allowing the antenna to radiate mid-frequency right-hand circularly polarized waves. The high isolation of the 3dB directional coupler 8 provides good isolation between the antenna ports.

[0045] The technical effects of the present invention are illustrated below through simulation experiments:

[0046] 1. Simulation conditions and content:

[0047] The present invention was simulated using Ansys Electronics Desktop 2022R1 simulation software. Simulation graphs are shown below. Figure 2 In the model, the feed port of the first radiating patch 1 is named Port 1 (i.e., the coaxial feed structure at the center of the antenna element), and the feed ports of the second radiating patch 2 and the third radiating patch 3 are named Port 2 and Port 3 respectively (i.e., the two input ports of the 3dB directional coupler 8).

[0048] 2. Simulation Result Analysis:

[0049] like Figure 4 (a) and Figure 4 As shown in (b), the horizontal axis represents frequency, and the vertical axis represents S-parameters and axial ratio. This radiation frequency band is generated by the first radiating patch 1, within the 2.47GHz-2.52GHz frequency band. 11 Less than -11dB and axial ratio less than 3dB, indicating that the first radiating patch 1 has good impedance matching and circularly polarized radiation within the designed frequency band. Figure 7 As shown in (a), the horizontal axis represents the antenna radiation elevation angle, and the vertical axis represents the antenna radiation gain. At 2.491 GHz, the antenna gain is ≥-1 dB within ±60° and it radiates a right-hand circularly polarized wave.

[0050] like Figure 5 (a) and Figure 5As shown in (b), the horizontal axis represents frequency, and the vertical axis represents S-parameters and axial ratio. This radiation frequency band is generated jointly by the second radiating patch 2 and the third radiating patch 3, within the 1.5GHz-1.66GHz frequency band. 22 Less than -11dB and an axial ratio less than 3dB indicate that the antenna has good impedance matching and circularly polarized radiation in this frequency band. Figure 7 As shown in (b), the horizontal axis represents the antenna radiation elevation angle, and the vertical axis represents the antenna radiation gain. At 1.615 GHz, the antenna gain is ≥-1 dB within ±60° and it radiates a right-hand circularly polarized wave.

[0051] like Figure 6 (a) and Figure 6 As shown in (b), the horizontal axis represents frequency, and the vertical axis represents S-parameters and axial ratio. This radiation frequency band is generated jointly by the second radiating patch 2 and the third radiating patch 3, within the 1.18GHz-1.23GHz frequency band. 33 Less than -11dB and an axial ratio less than 3dB indicate that the antenna has good impedance matching and circularly polarized radiation in this frequency band. Figure 7 As shown in (c), the horizontal axis represents the antenna radiation elevation angle, and the vertical axis represents the antenna radiation gain. At 1.207 GHz, the antenna gain is ≥-1 dB within ±60° and it radiates a left-hand circularly polarized wave.

[0052] The results show that the antenna has good impedance matching in all three designed frequency bands and can achieve circular polarization wave radiation with different rotation directions, making it suitable for circular polarization communication requirements under different conditions.

[0053] Compared to traditional single-layer microstrip patches, the stacked microstrip antenna designed in this invention utilizes the small size and low profile of microstrip patch antennas to stack the patch antennas, enabling the antenna to radiate three different frequency bands of circularly polarized waves, which greatly reduces the size of the antenna in the lateral direction.

[0054] The designed 3dB directional coupler 8 feeding method and the first radiating patch 1 corner cutting operation make the electromagnetic wave axis ratio radiated by the antenna less than 3dB in all three frequency bands, and have good circular polarization performance.

[0055] A U-shaped slot 20 is opened on the first radiating patch 1 to ensure that the return loss of the antenna is less than -11dB in the radiation frequency band. The antenna has a good impedance matching effect and the power supply energy is fully utilized.

[0056] The designed antenna has a gain of no less than -1dB in all three frequency bands within a normal range of ±60°, and the antenna's radiation performance is not significantly affected by the stacked design.

Claims

1. A three-band stacked circularly polarized antenna, comprising a first dielectric substrate (4), a second dielectric substrate (5), a third dielectric substrate (6), and a stripline dielectric layer (7) stacked from top to bottom, characterized in that: A first radiating patch (1) is printed on the top of the first dielectric substrate (4), a second radiating patch (2) is printed on the top of the second dielectric substrate (5), and a third radiating patch (3) is printed on the top of the third dielectric substrate (6); a directional coupler (8) is disposed in the middle of the stripline dielectric layer (7); the energy input port (18) of the directional coupler (8) is located on both sides of the stripline dielectric layer (7), and the energy output port (17) of the directional coupler (8) is located on the center vertical lines of the mutually perpendicular sides of the stripline dielectric layer (7). The two energy input ports (18) of the directional coupler (8) are fed through the first coaxial line (10) and the second coaxial line (11); the coaxial feeding structure (12) passes through the center of the stripline dielectric layer (7), the third dielectric substrate (6), the second dielectric substrate (5) and the first dielectric substrate (4), the inner conductor (16) of the coaxial feeding structure is connected to the first radiating patch (1), and the outer conductor (19) of the coaxial feeding structure is connected to the second radiating patch (2); The first radiating patch (1), the second radiating patch (2) and the third radiating patch (3) are located at the center of the first dielectric substrate (4), the second dielectric substrate (5), the third dielectric substrate (6) and the stripline dielectric layer (7), respectively. The directional coupler (8) leads a power supply probe (13) upward from the energy output port (17). The power supply probe (13) passes through the third dielectric substrate (6), the third radiating patch (3), the second dielectric substrate (5), and is connected to the second radiating patch (2) in sequence. The inner conductor (21) of the coaxial line is connected to the energy input port (18) of the directional coupler (8), and the outer conductor (22) of the coaxial line is connected to the lower metal ground plane (15) of the stripline dielectric layer (7).

2. The three-band stacked circularly polarized antenna according to claim 1, characterized in that: The strip-shaped dielectric layer (7) is provided with an upper metal floor (14) and a lower metal floor (15) on its upper and lower sides, respectively, wherein the upper metal floor (14) is the radiation floor of the second radiation patch (2) and the third radiation patch (3).

3. The three-band stacked circularly polarized antenna according to claim 1, characterized in that: The diameter of the hole through which the power supply probe (13) passes is greater than the cross-sectional diameter of the power supply probe (13), ensuring that the power supply probe (13) does not contact the third radiation patch (3) and preventing the power supply probe (13) from being short-circuited by the third radiation patch (3).

4. The three-band stacked circularly polarized antenna according to claim 1, characterized in that: The directional coupler (8) is surrounded by a number of metallized vias (9), which are connected to the upper metal floor (14) and the lower metal floor (15) of the stripline dielectric layer (7).

5. The three-band stacked circularly polarized antenna according to claim 1, characterized in that: The second radiation patch (2) and the third radiation patch (3) are both square; the first radiation patch (1) has a U-shaped gap (20) in the middle, and the two opposite corners of the first radiation patch (1) are chamfered.

6. The three-band stacked circularly polarized antenna according to claim 1, characterized in that: The size of the third radiating patch (3) is larger than the size of the second radiating patch (2), and the size of the second radiating patch (2) is larger than the size of the first radiating patch (1).

7. The three-band stacked circularly polarized antenna according to claim 1, characterized in that: The directional coupler (8) is a 3dB directional coupler in the form of a stripline.

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