Millimeter wave circularly polarized antenna for coplanar waveguide coupled feeding

Abstract

The invention discloses a coplanar waveguide coupled feed millimeter wave circularly polarized antenna. The millimeter wave circularly polarized antenna comprises a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, a radiation structure, a coplanar waveguide structure, a grounding plate and a feed circuit, the first dielectric substrate, the second dielectric substrate and the third dielectric substrate are sequentially arranged from top to bottom in the vertical direction; the radiation structure is arranged on the upper surface of the first dielectric substrate; the coplanar waveguide structure is arranged between the first dielectric substrate and the second dielectric substrate; the coplanar waveguide structure comprises four coplanar waveguide lines and a first ground plane, every two coplanar waveguide lines are arranged at an interval of 90 degrees, one ends of the four coplanar waveguide lines are in short-circuit connection with the first ground plane, and matching branches are arranged on the coplanar waveguide lines; the grounding plate is arranged between the second dielectric substrate and the third dielectric substrate; and the feed circuit is arranged on the lower surface of the third dielectric substrate and is connected with the other ends of the four coplanar waveguide wires through metal via holes. The compact structure of the circularly polarized antenna is maintained, and the wide impedance bandwidth and the 3dB axial ratio bandwidth are achieved at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of millimeter wave antennas, and in particular to a coplanar waveguide coupled-fed millimeter wave circularly polarized antenna. Background Art

[0002] Due to its abundant spectrum resources, the millimeter wave band is gradually becoming the operating band of choice for next-generation wireless communication systems. As a crucial component of millimeter wave wireless communication systems, the performance of millimeter wave antennas has a significant impact on the overall system. Compared to linearly polarized antennas, circularly polarized antennas do not require polarization alignment, allowing for more flexible transmit and receive configurations. They also offer strong immunity to multipath interference, effectively reducing distortion caused by signal reflections. Furthermore, circularly polarized antennas can suppress the Faraday rotation effect in the ionosphere, ensuring signal transmission quality. These advantages have led to their widespread use in millimeter wave communication scenarios, including satellite communications and 5G / 6G communications.

[0003] However, common millimeter-wave circularly polarized antennas often have defects such as high profile, complex structure, and narrow operating bandwidth, which cannot well meet the growing demand for millimeter-wave communications.

[0004] Coplanar waveguide structures have become the preferred solution for millimeter-wave antenna feeding in recent years due to their advantages such as stable modes, low transmission loss, low physical profile, and ease of fabrication. However, existing circularly polarized antennas fed by coplanar waveguides still suffer from bandwidth limitations. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention aims to provide a millimeter-wave circularly polarized antenna fed by coplanar waveguide coupling to solve the problem of insufficient bandwidth of coplanar waveguide-fed circularly polarized antennas.

[0006] The present application proposes a millimeter-wave circularly polarized antenna with coplanar waveguide coupling and feeding, which includes a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, a radiating structure, a coplanar waveguide structure, a ground plane and a feeding line; the first dielectric substrate, the second dielectric substrate and the third dielectric substrate are arranged in sequence from top to bottom in a vertical direction; the radiating structure is arranged on the upper surface of the first dielectric substrate; the coplanar waveguide structure is arranged between the first dielectric substrate and the second dielectric substrate; the coplanar waveguide structure includes four coplanar waveguide lines and a first ground plane, the four coplanar waveguide lines are arranged at 90° intervals in pairs, and one end of the four coplanar waveguide lines is short-circuited to the first ground plane, and matching branches are provided on the coplanar waveguide lines; the ground plane is arranged between the second dielectric substrate and the third dielectric substrate; the feeding line is arranged on the lower surface of the third dielectric substrate and connected to the other ends of the four coplanar waveguide lines.

[0007] According to the millimeter-wave circularly polarized antenna of the present application, a coplanar waveguide line with a short terminal is used to couple and excite the top radiating structure, thereby achieving a wider operating bandwidth while maintaining the compact structure of the circularly polarized antenna; matching branches are set on the coplanar waveguide line, and a resonance point is introduced within the operating frequency band through simulation optimization, thereby expanding the impedance bandwidth of the antenna.

[0008] According to some embodiments of the present application, the matching branch is provided near one end of the coplanar waveguide line where the short circuit connection is made.

[0009] According to some embodiments of the present application, each coplanar waveguide line is provided with two matching branches, and the two matching branches are arranged perpendicular to the coplanar waveguide line.

[0010] According to some embodiments of the present application, the radiation structure includes four radiation patches, and the four radiation patches are arranged in a 2×2 array.

[0011] According to some embodiments of the present application, a first ground plane is arranged around four coplanar waveguide lines and is connected to one end of the four coplanar waveguide lines; the coplanar waveguide structure also includes a second ground plane, which is arranged in the enclosed area of the first ground plane and has a gap with the coplanar waveguide lines; the second ground plane is connected to the ground plate.

[0012] According to some embodiments of the present application, the feeding circuit includes four feeding microstrip lines connected to the coplanar waveguide lines in a one-to-one correspondence, and the other end of the coplanar waveguide line is connected to the feeding microstrip line through a first metal via.

[0013] According to some embodiments of the present application, the second ground plane is provided with a hollow area, and the other end of the coplanar waveguide line is provided in the hollow area, and a gap exists between the other end of the coplanar waveguide line and the forming surface of the hollow area.

[0014] According to some embodiments of the present application, the second ground plane is connected to the ground plate through a second metal via.

[0015] According to some embodiments of the present application, the second metal via is structured in multiple numbers, and the multiple second metal vias are arranged around the first metal via.

[0016] According to some embodiments of the present application, the ground plate is formed with an avoidance hole suitable for the first metal via to pass through.

[0017] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0019] Figure 1 is a schematic structural diagram of a millimeter wave circularly polarized antenna according to some embodiments of the present application;

[0020] Figure 2 is a schematic diagram of a layered structure of a millimeter-wave circularly polarized antenna according to some embodiments of the present application;

[0021] Figure 3 is a structural side view of a millimeter-wave circularly polarized antenna according to some embodiments of the present application;

[0022] Figure 4 is a schematic structural diagram of a coplanar waveguide structure according to some embodiments of the present application;

[0023] Figure 5 is a graph showing the reflection coefficient simulation results of a millimeter-wave circularly polarized antenna according to some embodiments of the present application;

[0024] Figure 6 1 is a diagram showing the simulation results of port isolation of a millimeter-wave circularly polarized antenna according to some embodiments of the present application;

[0025] Figure 7 is the far-field radiation pattern of the millimeter-wave circularly polarized antenna with phi = 0° (E plane) according to some embodiments of the present application;

[0026] Figure 8 is the far-field radiation pattern of the millimeter-wave circularly polarized antenna with phi=90° (H-plane) according to some embodiments of the present application;

[0027] Figure 9 is a diagram showing simulation results of a curve showing gain variation with frequency in the main radiation direction of a millimeter-wave circularly polarized antenna according to some embodiments of the present application;

[0028] Figure 10 This is a diagram showing simulation results of the axial ratio of a millimeter-wave circularly polarized antenna according to some embodiments of the present application.

[0029] Reference numerals:

[0030] Radiating structure 10; first dielectric substrate 20; coplanar waveguide structure 30; second dielectric substrate 40; ground plate 50; third dielectric substrate 60; feeding line 70; first metal via 80; second metal via 90;

[0031] Radiating patch 11 ; coplanar waveguide 31 ; first ground plane 32 ; second ground plane 33 ; first matching branch 34 ; second matching branch 35 ; avoidance hole 51 . DETAILED DESCRIPTION

[0032] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0033] Reference below Figures 1-4 A millimeter-wave circularly polarized antenna using coplanar waveguide coupling and feeding according to an embodiment of the present invention is described.

[0034] The present application proposes a millimeter-wave circularly polarized antenna with coplanar waveguide coupling feeding, which includes a first dielectric substrate 20, a second dielectric substrate 40, a third dielectric substrate 60, a radiating structure 10, a coplanar waveguide structure 30, a ground plate 50 and a feeding line 70; the first dielectric substrate 20, the second dielectric substrate 40 and the third dielectric substrate 60 are arranged in sequence from top to bottom in a vertical direction; the radiating structure 10 is arranged on the upper surface of the first dielectric substrate 20; the coplanar waveguide structure 30 is arranged on the first dielectric substrate 20 and the second dielectric substrate 40; the coplanar waveguide structure 30 includes four coplanar waveguide lines 31 and a first ground plane 32. The four coplanar waveguide lines 31 are arranged at 90° intervals in pairs, and one end of the four coplanar waveguide lines 31 is short-circuited to the first ground plane 32. Matching branches are provided on the coplanar waveguide lines 31; the ground plane 50 is arranged between the second dielectric substrate 40 and the third dielectric substrate 60; the feeding line 70 is arranged on the lower surface of the third dielectric substrate 60 and connected to the other ends of the four coplanar waveguide lines 31.

[0035] It should be noted that the radiating structure 10, first dielectric substrate 20, coplanar waveguide structure 30, second dielectric substrate 40, ground plane 50, third dielectric substrate 60, and feeder circuit 70 of the present application are closely bonded. The millimeter-wave circularly polarized antenna of the present application is constructed as a simple stacked structure, which is compact and can be realized using common printed circuit board (PCB) processes. It has low processing difficulty and low processing cost, making it suitable for large-scale production applications.

[0036] According to the millimeter-wave circularly polarized antenna of the present application, one end of the feed line 70 is connected to the feed port, and the other end is connected to the coplanar waveguide structure 30 to realize layer-changing transmission of the signal; the ground plate 50 serves as the reference ground for the coplanar waveguide structure 30 and the bottom layer feed line 70 to isolate the signals transmitted by the two layers; in the coplanar waveguide structure 30, the matching branch is used to couple and excite the top layer radiation structure 10. The size of the matching branch can enhance the coupling between the coplanar waveguide line 31 and the radiation structure 10 through simulation design, effectively broadening the working bandwidth of the millimeter-wave circularly polarized antenna; the coplanar waveguide line 31 is short-circuited through the first ground plane 32, so that the energy not used for coupling excitation can be grounded, reducing the return loss, and facilitating the broadening of the impedance matching bandwidth of the antenna.

[0037] According to the millimeter-wave circularly polarized antenna of the present application, a coplanar waveguide line 31 with a short terminal is used to couple and excite the top radiating structure 10, thereby achieving a wider operating bandwidth while maintaining the compact structure of the circularly polarized antenna; matching branches are set on the coplanar waveguide line 31, and a resonance point is introduced within the operating frequency band through simulation optimization, thereby expanding the impedance bandwidth of the antenna.

[0038] According to some embodiments of the present application, the millimeter-wave circularly polarized antenna is constructed as a centrosymmetric structure, uses sequential rotation feeding to achieve circular polarization, and has good circular polarization performance.

[0039] According to some embodiments of the present application, the matching branch is arranged near the short-circuited end of the coplanar waveguide line 31; each coplanar waveguide line 31 is provided with two matching branches, and the two matching branches are arranged perpendicular to the coplanar waveguide line 31. Figure 3 、 4 As shown, in this embodiment, two matching branches are provided, namely a first matching branch 34 and a second matching branch 35. The two matching branches are of the same or different lengths. Depending on the size relationship between the branches and the wavelength, they correspond to two resonant points in the operating bandwidth. Through simulation optimization, the introduction of two resonant points within the operating frequency band can further expand the impedance bandwidth of the antenna. Furthermore, it should be noted that if the matching branch is far from the short-circuit connection end, most of the RF signal energy will be transmitted along the main line of the short-circuit connection, reducing the proportion of energy fed into the matching branch and lowering the radiation efficiency. Therefore, adding a matching branch to the short-circuit end of the coplanar waveguide line 31 can improve the radiation efficiency.

[0040] According to some embodiments of the present application, the radiating structure 10 includes four radiating patches 11 arranged in a 2×2 array. In this embodiment, the radiating structure 10 is constructed with four radiating patches 11 spaced apart from each other. Simulation and optimization of the size and spacing of the radiating patches 11 can ultimately achieve a stable gain curve within the operating frequency band, an ideal far-field radiation pattern, and ideal radiation characteristics. In some embodiments, the radiating patches 11 are rectangular.

[0041] Furthermore, the positional relationship between the matching branch and the radiation patch, as well as the size of the matching branch, were optimized through simulation to obtain optimal values.

[0042] According to some embodiments of the present application, the first ground plane 32 is arranged around the four coplanar waveguide lines 31 and is connected to one end of the four coplanar waveguide lines 31; the coplanar waveguide structure 30 further includes a second ground plane 33, which is arranged in the area surrounded by the first ground plane 32 and has a gap with the coplanar waveguide lines 31; the second ground plane 33 is connected to the ground plate 50. In this embodiment, Figure 3 、 4As shown, the first ground plane 32 connects the four coplanar waveguide lines 31 to achieve a short-circuit connection between the coplanar waveguide lines 31. When the RF signal is transmitted to the end of the coplanar waveguide line, it will be divided into three paths, which are respectively fed into the matching branches on both sides or continue to be transmitted along the main path, so that this part of the energy not used for coupling excitation is grounded, reducing the return loss and improving the radiation efficiency; the second ground plane 33 serves as the reference ground of the coplanar waveguide line 31 and is connected to the ground plane 50, which can improve the isolation between the four feeding paths, namely the coplanar waveguide lines 31, and can improve the transmission stability and reduce the radiation loss.

[0043] According to some embodiments of the present application, the feed line 70 includes four feed microstrip lines connected one-to-one with the coplanar waveguide line, and the other end of the coplanar waveguide line 31 is connected to the feed microstrip line through a first metal via 80. In this embodiment, the feed line 70 is constructed as four feed microstrip lines and connected to the coplanar waveguide line 31 to achieve signal transmission. The feed line 70 of this embodiment achieves circularly polarized radiation through sequential rotation feeding. Furthermore, this embodiment uses a first metal via 80 with a quasi-coaxial structure to connect the bottom feed line 70 and the coplanar waveguide line 31, reducing the impact of the feed line 70 on the antenna radiation characteristics.

[0044] According to some embodiments of the present application, the second ground plane 33 is provided with a hollowed-out region, and the other end of the coplanar waveguide 31 is disposed in the hollowed-out region, with a gap between the hollowed-out region and the surface formed by the hollowed-out region. The second ground plane 33 is connected to the ground plate 50 via a second metal via 90. Multiple second metal vias 90 are provided, and the plurality of second metal vias 90 are disposed around the first metal via 80. In this embodiment, the second metal vias 90 disposed around the first metal via 80 can achieve signal isolation between different ports and improve impedance matching during signal layer switching.

[0045] According to some embodiments of the present application, the ground plate 50 is formed with an avoidance hole 51 suitable for the first metal via 80 to pass through. Figure 3 As shown, in this embodiment, the avoidance hole 51 can be constructed as an anti-pad opening, and the diameter of the avoidance hole 51 can be optimized through simulation to achieve impedance matching during signal layer switching transmission.

[0046] The millimeter wave circular polarization antenna with coplanar waveguide coupling feeding of the present application is simulated and tested, and the test results are as follows: Figure 5-8 shown.

[0047] Figure 5 The figure shows the reflection coefficient simulation results of the millimeter wave circularly polarized antenna of the present application, which are obtained by simulating the bottom feed port using the three-dimensional high-frequency electromagnetic field simulation software Ansys HFSS. Figure 5As shown in Figure 1, due to the rotational symmetry of the millimeter-wave circularly polarized antenna structure, the transmission characteristics of the four ports are the same. Taking any one of the ports as an example, the -10dB operating bandwidth of the antenna unit is 21.1GHz-35.1GHz, with a relative bandwidth of 46%.

[0048] Figure 6 The following figure shows the port isolation simulation results of the millimeter wave circularly polarized antenna of this application. Figure 6 As shown in the figure, the symmetrical port isolation is better than that of the adjacent port, and the port isolation exceeds 10dB within the working frequency band.

[0049] Figure 7 and Figure 8 The far-field radiation patterns for a millimeter-wave circularly polarized antenna operating at 30 GHz, using sequential rotational feeding, with phi = 0° (E-plane) and phi = 90° (H-plane) are shown. The antenna unit has a peak gain of 7.4 dBi, symmetrical E-plane and H-plane patterns, and a 3 dB beamwidth of ±37°.

[0050] Figure 9 This graph shows the gain in the main radiation direction of the millimeter-wave circularly polarized antenna in this application as a function of frequency in the sequential rotation feeding mode. It shows that the millimeter-wave circularly polarized antenna has relatively stable gain within the operating frequency band and good radiation performance, making it suitable for millimeter-wave communication systems.

[0051] Figure 10 This figure shows the simulation results of the axial ratio of the millimeter-wave circularly polarized antenna of this application. The antenna has a 3dB axial ratio bandwidth of 21.2GHz-34.4GHz, demonstrating good circular polarization performance within the operating frequency band.

[0052] According to the above test results, the coplanar waveguide coupled-fed millimeter-wave circularly polarized antenna proposed in this application can achieve an operating bandwidth of 21.1GHz-35.1GHz (46%), a 3dB axial ratio bandwidth of 21.2GHz-34.4GHz, a symmetrical radiation pattern and a stable gain curve within the band, which can well meet the performance requirements of the millimeter-wave communication system for the transceiver front end, and provide a new solution for the RF front end of the millimeter-wave communication system.

[0053] To sum up, compared with the existing technology, the present application has the following technical effects: 1. The terminal short-circuited coplanar waveguide line is used to couple and excite the top radiation structure, thereby achieving a wider operating bandwidth while maintaining the compact structure of the antenna; 2. Two matching branches are set at the short-circuited end of the coplanar waveguide line, and two resonance points are introduced within the operating frequency band through simulation optimization, further expanding the impedance bandwidth of the antenna; 3. The size and spacing of the top radiation patch are simulated and optimized, which can ultimately achieve a stable gain curve within the operating frequency band; 4. Metal vias with a quasi-coaxial structure are used to connect the bottom feeding line and the coplanar waveguide line, reducing the impact of the feeding line on the antenna radiation characteristics; 5. The simple stacked structure can be achieved through common PCB technology, which effectively reduces processing costs and provides convenience for large-scale production and application.

[0054] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0055] In the description of the present invention, "first feature" and "second feature" may include one or more of the features.

[0056] In the description of the present invention, "plurality" means two or more.

[0057] In the description of the present invention, a first feature being “on” or “under” a second feature may include the first and second features being in direct contact with each other, or the first and second features not being in direct contact with each other but being in contact with each other via another feature therebetween.

[0058] In the description of the present invention, “on”, “above” and “above” a first feature of a second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature.

[0059] Throughout this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "example," "specific example," or "some examples" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, illustrative uses of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0060] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A millimeter-wave circularly polarized antenna with coplanar waveguide coupling feeding, characterized in that: include: A first dielectric substrate, a second dielectric substrate, and a third dielectric substrate, wherein the first dielectric substrate, the second dielectric substrate, and the third dielectric substrate are arranged in sequence from top to bottom along a vertical direction; a radiation structure, the radiation structure being arranged on the upper surface of the first dielectric substrate; A coplanar waveguide structure, the coplanar waveguide structure being disposed between the first dielectric substrate and the second dielectric substrate; the coplanar waveguide structure comprising four coplanar waveguide lines and a first ground plane, the four coplanar waveguide lines being disposed 90° apart in pairs, one end of the four coplanar waveguide lines being short-circuited to the first ground plane, and the coplanar waveguide lines being provided with matching branches; a ground plate, the ground plate being disposed between the second dielectric substrate and the third dielectric substrate; A feeder line is provided on the lower surface of the third dielectric substrate and is connected to the other ends of the four coplanar waveguide lines.

2. The millimeter-wave circularly polarized antenna with coplanar waveguide coupling feeding according to claim 1, characterized in that: The matching branch is arranged close to one end of the coplanar waveguide wire that is short-circuited.

3. The millimeter-wave circularly polarized antenna with coplanar waveguide coupling feeding according to claim 2, characterized in that: Each of the coplanar waveguide lines is provided with two matching branches, and the two matching branches are arranged perpendicular to the coplanar waveguide line.

4. The millimeter-wave circularly polarized antenna with coplanar waveguide coupling feeding according to claim 1, characterized in that: The radiation structure includes four radiation patches, and the four radiation patches are arranged in a 2×2 array.

5. The millimeter-wave circularly polarized antenna with coplanar waveguide coupling feeding according to claim 1, characterized in that: The first ground plane is arranged around the four coplanar waveguide lines and is connected to one end of the four coplanar waveguide lines; The coplanar waveguide structure further includes: a second ground plane, which is arranged in the enclosed area of the first ground plane and has a gap with the coplanar waveguide line; the second ground plane is connected to the ground plate.

6. The coplanar waveguide coupled and fed millimeter wave circularly polarized antenna according to claim 5, characterized in that: The feeding circuit includes four feeding microstrip lines connected to the coplanar waveguide lines in a one-to-one correspondence, and the other end of the coplanar waveguide line is connected to the feeding microstrip line through a first metal via.

7. The coplanar waveguide coupled and fed millimeter wave circularly polarized antenna according to claim 6, characterized in that: The second ground plane is provided with a hollow area, and the other end of the coplanar waveguide is provided in the hollow area, with a gap between the other end and the forming surface of the hollow area.

8. The coplanar waveguide coupled and fed millimeter wave circularly polarized antenna according to claim 7, characterized in that: The second ground plane is connected to the ground plate through a second metal via.

9. The coplanar waveguide coupled-fed millimeter-wave circularly polarized antenna according to claim 8, characterized in that: There are multiple second metal vias, and the multiple second metal vias are arranged around the first metal via.

10. The coplanar waveguide coupled and fed millimeter wave circularly polarized antenna according to claim 6, characterized in that: The ground plate is formed with an avoidance hole suitable for the first metal via to pass through.

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