A circularly polarized antenna element

Abstract

The application discloses a circularly polarized antenna unit, belonging to the technical field of antennas; the integrated equivalent shielding cavity comprises a circular equivalent shielding structure and four groups of signal holes in coaxial structure. The circularly polarized antenna unit comprises a radiation patch, a feed patch, an antenna bottom plate, a feed network and other components. The equivalent shielding cavity is a physical structure formed by arranging a plurality of metallized through holes / blind holes according to certain rules. In the unit design of the circularly polarized antenna, the radiation patch is located on the uppermost layer of a multilayer laminated PCB board, the four groups of feed patches are located between the radiation patch and the antenna bottom plate, are symmetrically distributed along the center of the antenna unit, and are spaced by 90 degrees each other, and the feed network is located below the antenna bottom plate and is connected with the feed patches and the signal holes in coaxial structure respectively. The application combines the equivalent shielding cavity design with the integrated signal hole and the multi-point feed antenna technology, significantly improves the axial ratio index characteristics of the circularly polarized antenna in the frequency band of 24.25-27.5 GHz, and has relatively high radiation efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of antennas, in particular to a circularly polarized antenna unit; the equivalent shielding cavity of the antenna unit integrates the function of the signal hole while improving the mutual coupling effect between the antenna units in the array. BACKGROUND

[0002] When the development of mobile communication enters the 5 / 6G stage, millimeter wave antennas are widely used due to their rich spectrum resources and become one of the important evolution directions. In the millimeter wave antenna system based on the AiP / AoB architecture, a multi-channel radio frequency chip provides the power amplitude and phase required for synthesizing beam scanning for each antenna unit in the millimeter wave phased array. At the same time, in order to reduce the connection loss between the antenna unit excitation port and the channel of the radio frequency chip, a coaxial structure equivalent to a metalized via is usually used for vertical dimension interconnection connection.

[0003] In the design of the millimeter wave phased array antenna system based on the AiP / AoB architecture, a multi-layer press-fit PCB board manufacturing process is usually used, and the antenna unit is located in the upper half of the multi-layer board, and the multi-channel radio frequency chip is welded on the back of the multi-layer board. The antenna unit and the radio frequency chip are interconnected and connected through a coaxial structure made of a metalized via. The metalized via structure in the multi-layer board can be reasonably arranged to form equivalent shielding cavities of different shapes, which are used to block the electromagnetic energy coupling between the units in the array antenna, and can also be combined into a coaxial structure to realize the vertical dimension transmission of radio frequency signals between the layers of the multi-layer PCB board.

[0004] In the design of circularly polarized antennas, the axial ratio index is crucial, and a radiation unit with excellent axial ratio index and large bandwidth can significantly improve the synthesized beam scanning characteristics of the array antenna. However, in the design process of millimeter wave circularly polarized antennas based on the multi-layer press-fit PCB board manufacturing process, the existence of the coaxial structure destroys the symmetry of the boundary conditions of the circularly polarized antenna unit, which restricts the improvement of the synthesized beam axial ratio index of the circularly polarized phased array antenna. SUMMARY

[0005] Therefore, the present application provides a circularly polarized antenna unit. The equivalent shielding cavity of the antenna unit integrates the signal via function to improve the influence of the signal hole on the antenna axial ratio index in the design of the millimeter wave circularly polarized antenna.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] A circularly polarized antenna unit, comprising an equivalent shielding cavity and a radiation patch layer, a feed patch layer and a feed network layer stacked in sequence; the radiation patch layer, the feed patch layer and the feed network layer all use a multi-layer press-fit PCB board as a substrate;

[0008] The radiation patch layer comprises a first dielectric substrate; the upper surface of the first dielectric substrate is provided with a circular radiation patch;

[0009] The feeding patch layer comprises a second dielectric substrate; the upper surface of the second dielectric substrate is provided with four feeding patches; the feeding patches are symmetrically distributed at an interval of 90 degrees, and the center of symmetry is located directly below the center of the radiation patch; the lower surface of the second dielectric substrate is provided with an antenna bottom plate;

[0010] The feeding network layer comprises a third dielectric substrate; the lower surface of the third dielectric substrate is provided with a feeding network; the end ports of the feeding network are connected to the circular part of the feeding patch at the top through corresponding feeding columns; the feeding columns are not in contact with the antenna bottom plate; the lower surface of the feeding network is further provided with a lower metal ground plate,

[0011] The lower surface of the fourth dielectric substrate is provided with a lower metal ground plate; the lower surface of the fifth dielectric substrate is provided with a surface microstrip line;

[0012] The equivalent shielding cavity comprises four coaxial structure signal holes, and the spacing between adjacent coaxial structure signal holes is the same; the coaxial structure signal holes are distributed around the center of the radiation patch; the coaxial structure signal holes comprise edge through holes and center through holes; the edge through holes are evenly distributed around the corresponding center through holes;

[0013] The edge through holes and the center through holes sequentially penetrate the first dielectric substrate, the second dielectric substrate, the third dielectric substrate, the fourth dielectric substrate and the fifth dielectric substrate from top to bottom; the lower surface of the third dielectric substrate is further provided with a first solder pad 23, and the center through hole is connected to the total feeding port of the feeding network through the first solder pad; the lower surface of the fifth dielectric substrate is further provided with a second solder pad 24; the center through hole is connected to the surface microstrip line through the second solder pad.

[0014] Further, the feeding network is a one-to-four power divider network formed by cascading two one-to-two Wilkinson power dividers.

[0015] Further, the feeding patch comprises a circular part, a rectangular part; the circular part and the rectangular part are connected through a strip part, and the central axes of the three parts coincide; the rectangular part is provided with wing parts on both sides of the end, and the included angle between the two wing parts is 90°; the two wing parts are symmetric about the central axis of the rectangular part.

[0016] Further, the four edge through holes form a square shape, and the corresponding center through hole is located at the center of the square shape.

[0017] Furthermore, multiple circular equivalent shielding structures are provided between adjacent coaxial signal holes; the circular equivalent shielding structures penetrate the first dielectric substrate, the second dielectric substrate, and the third dielectric substrate.

[0018] Furthermore, a printed resistor 12 is integrated between the output ports of the three 1-to-2 power dividers of the power supply network.

[0019] The beneficial effects of the above-mentioned technical solution adopted by the present invention are as follows:

[0020] 1. Based on the integrated structure of equivalent shielding cavity and signal aperture, this invention effectively reduces the impact of signal vias used in the design of PCB antennas to achieve the vertical cascading function of signals on the radiation performance of antenna elements, and improves the axial ratio of circularly polarized antennas.

[0021] 2. Based on the integrated structure of the equivalent shielding cavity and the signal hole, this invention reduces the processing difficulty of multilayer laminated PCB antennas and reduces the "back drilling" process used to remove the end branches of the signal hole.

[0022] 3. This invention is based on an integrated structure of an equivalent shielding cavity and a signal aperture. Compared to the traditional design that places the signal aperture outside the antenna element shielding cavity, this reduces the overall size of the antenna element, with an overall size ≤ 0.5λ. ╳ 0.5λ, which meets the requirements for wide-angle scanning phased array antennas.

[0023] 4. The "umbrella"-shaped probe feed structure in this invention satisfies the physical length required for probe resonance, thereby expanding the operating bandwidth of the circularly polarized antenna. Simultaneously, the "umbrella"-shaped structure design compresses the lateral dimensions of the feed structure, enabling miniaturization and providing feasibility for multi-point (four-point) fed circularly polarized antenna schemes.

[0024] 5. This invention combines the equivalent shielded cavity design of the integrated signal aperture with multi-point (four-point) fed antenna technology, which significantly improves the axial ratio performance of the circularly polarized antenna in the 24.25-27.5GHz frequency band. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention.

[0026] Figure 2 yes Figure 1 Top view.

[0027] Figure 3 yes Figure 1 Side view.

[0028] Figure 4 This is a top view of the equivalent shielded cavity integrating the signal hole function in an embodiment of the present invention.

[0029] Figure 5 This is a schematic diagram of the structure of the radiating unit and the feed plate in an embodiment of the present invention.

[0030] Figure 6 This is a side view of the structure of the radiating unit and the feed plate in an embodiment of the present invention.

[0031] Figure 7 This is a schematic diagram of the power supply network according to an embodiment of the present invention.

[0032] Figure 8 This is a simulated standing wave ratio curve according to an embodiment of the present invention.

[0033] Figure 9 This is a simulation axis ratio curve direction diagram of an embodiment of the present invention. Detailed Implementation

[0034] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] An equivalent shielding cavity and a circularly polarized antenna element suitable for integrating signal aperture functions in the millimeter-wave band are disclosed. The integrated equivalent shielding cavity is composed of several metallized through holes, including a shielding structure of the antenna element arranged in a circle and a coaxial signal aperture structure located at the four vertices. The circularly polarized antenna element includes a radiating patch, four sets of feed structures symmetrically distributed at 90 degrees, an antenna base plate, and a power distribution network.

[0037] To meet the large-angle scanning requirements of synthesized beams in the horizontal and vertical directions of large-scale phased array antennas, the element size of phased array antennas typically needs to be smaller than half a wavelength. The integrated equivalent shielding cavity consists of two structural parts, with an overall square structure and an overall size ≤0.5λ. × 0.5λ; The first part is a circular shielding structure composed of several metallized vias, which isolates the electromagnetic signals radiated by the circularly polarized antenna element placed in its center, preventing the plane waves generated in the multilayer dielectric substrate from propagating to surrounding antenna elements, while also being unaffected by the electromagnetic signals radiated by adjacent elements. The second part consists of four sets of coaxial-like structures placed at the four vertices of the square. The coaxial-like structures are composed of several metallized vias, including a signal hole in the center and shielding holes around the perimeter. Electromagnetic signals are transmitted between the signal hole and the shielding holes, producing a transmission effect similar to that in a coaxial line.

[0038] The integrated equivalent shielding cavity shares some metallized vias between its first part (circular equivalent shielding structure) and its second part (coaxial-like structure). Specifically, the metallized vias located at 45° / 135° / 225° / 315° in the circular equivalent shielding structure also function as signal shielding vias in the second part (coaxial-like structure), thus reducing the overall size of the integrated equivalent shielding cavity.

[0039] The integrated equivalent shielding cavity has a second part with a coaxial structure located outside the first part of the circular equivalent shielding cavity. Specifically, the circularly polarized antenna element is placed in the inner space of the circular equivalent shielding cavity, while four sets of coaxial structures are placed in the outer space. The antenna element and the four sets of coaxial structures are completely isolated by the circular shielding cavity. Simultaneously, the circular shielding cavity is a completely symmetrical structure, ensuring the symmetry of the radiation boundary of the internal circularly polarized antenna element. This design of structural integration and functional separation between the circular equivalent shielding cavity and the coaxial structure effectively reduces the impact of the signal aperture structure on the axial ratio of the circularly polarized antenna while achieving vertical interconnection of the antenna element and the multi-channel RF chip electrical signals in the AiP / AoB system architecture.

[0040] The circularly polarized antenna element placed inside the integrated equivalent shielding cavity is a probe-type four-point fed patch circularly polarized antenna. It is designed and formed into a spatial three-dimensional structure based on multi-layer PCB fabrication technology. The circular patch is located on the top layer of the multi-layer PCB, and the four probe-type feeding structures are located between the circular radiating patch and the antenna base plate. The power divider feeding network is a stripline structure located below the antenna base plate layer. This multi-point (four-point) feeding excitation method helps balance the surface current of the patch antenna, improving the axial ratio of the circularly polarized antenna element.

[0041] The feeding structure of the circularly polarized antenna consists of four sets of probe-type feed plates and a feeding network located below a metal substrate. The four sets of probe-type feed plates are located below the radiating plates of the antenna element, symmetrically distributed along the center of the antenna element, and spaced 90 degrees apart from each other. The probe-type feed plate structure is designed in an "umbrella" shape, which meets the physical length required for probe resonance and correspondingly expands the operating bandwidth of the circularly polarized antenna. At the same time, the "umbrella" structure design compresses the lateral dimensions of the feed plate structure, meets the miniaturization requirements of the feed plate structure, and provides feasibility for a multi-point (four-point) fed circularly polarized antenna scheme.

[0042] The feeding structure of the circularly polarized antenna comprises four sets of probe-type feed plates, including four sets of "umbrella"-shaped metal plates and four sets of feed pillars passing through a metal base plate. The upper and lower ends of each feed pillar are connected to the feed plate and the feed network, respectively, enabling the transmission of electrical signals from the feed network below the antenna base plate to the feed plate. The "umbrella"-shaped metal plates are formed by etching a metal layer on a PCB board, and the feed pillars are formed by through-hole / blind-hole structures in a multi-layer PCB board. The four sets of "umbrella"-shaped feed plates are placed parallel to the plane of the radiating patch, and the feed pillars are perpendicular to this plane. Each set of "umbrella"-shaped feed plates includes a transmission line segment extending along a ±45° direction and two end-loaded stubs at a 90-degree angle, collectively forming an "umbrella" shape. The coupling between the feed pillars and the antenna base plate generates an equivalent inductance, and the coupling between the "umbrella"-shaped metal plates and the antenna base plate and radiating patch generates an induced capacitance, thus forming a simple LC resonant circuit.

[0043] The circularly polarized antenna adopts a multi-point feeding structure, with its feeding network located below the antenna base plate and forming a stripline structure. The feeding network is a 1-to-4 power divider network formed by cascading two 1-to-2 Wilkins power dividers. The four output ports complete the signal excitation of the four sets of feed plates, realizing output signals with equal amplitude and phase distribution of 0° / 90° / 180° / 270° (or 0° / -90° / -180° / -270°), thereby generating left-hand / right-hand circularly polarized antennas.

[0044] The overall design of the four-point fed probe type circularly polarized antenna is based on the processing technology of multilayer laminated PCB board; the upper half of the multilayer board in the overall design is the circularly polarized antenna body, and a multi-channel RF chip is soldered on the lower surface of the multilayer PCB board. The circularly polarized antenna and the RF chip are electrically connected in the vertical direction by the through-hole / blind hole structure inside the multilayer board.

[0045] Referring to the attached diagram, the following is a more detailed explanation:

[0046] like Figures 1-7As shown in the figure, this embodiment is an equivalent shielding cavity integrating signal aperture function, and a multi-point fed circularly polarized antenna unit adapted thereto. The integrated equivalent shielding cavity includes a circular equivalent shielding structure 1 and four sets of coaxial structure through-layer signal apertures 2. The multi-point fed circularly polarized antenna unit includes components such as a radiating patch 3, a feed piece 4, an antenna base plate 5, and a feed network 6. The four sets of coaxial structure signal apertures 2 are located in the external space of the circular equivalent shielding structure 1 and are symmetrically distributed at 90-degree intervals. The circularly polarized antenna unit is placed in the internal space of the circular equivalent shielding structure 1. In the unit design of the circularly polarized antenna, the radiating patch 3 is located on the top layer of the multilayer laminated PCB board, the four sets of feed pieces 4 are located between the radiating patch 3 and the antenna base plate 5, symmetrically distributed along the center of the antenna unit and spaced 90 degrees apart from each other, and the feed network 6 is located below the antenna base plate 5 and is connected to the feed piece 4 and the coaxial structure through-layer signal apertures 2 respectively.

[0047] The integrated equivalent shielding cavity is designed as a square, with four sets of coaxial structures located at the four vertices of the square. The circular shielding structure in the integrated equivalent shielding cavity is composed of several metallized vias arranged in a rotating pattern around the center of the antenna element, with a rotation diameter of 0.5λ. To share the metallized vias with the shielding pillars of the coaxial structures at the four vertices of the square, the number of metallized vias is chosen to be 4×n, where n≥1. Considering the process capability of the multilayer laminated PCB and the electromagnetic signal shielding effect, 16 metallized vias are chosen for the 26GHz band.

[0048] The coaxial-like signal aperture in the integrated equivalent shielding cavity consists of a central through-hole 21 located in the center and four edge through-holes 22 evenly distributed around it to achieve a shielding effect. The radio frequency signal is transmitted between the central through-hole 21 and the edge through-holes 22, achieving a transmission effect similar to a coaxial line. The four edge through-holes 22 form a square shape, with the central through-hole 21 located at its center. The central through-hole 21 terminates at the first pad 23 and is electrically connected to the feed network 6 on the layer containing the feed network. On the bottom layer of the multilayer PCB, it terminates at the second pad 24 and is connected to the surface microstrip line 7. The surface microstrip line 7 is connected to the pin pads of the multi-channel RF chip. Through the coaxial-like structure, the radio frequency signal is transmitted from the multi-channel RF chip soldered on the lower surface of the multilayer PCB to the circularly polarized antenna unit feed network 6 on the inner layer of the multilayer PCB, realizing the cascading of the RF chip and the antenna unit.

[0049] The equivalent shielding cavity and its antenna design with integrated signal aperture function are based on multilayer PCB board technology. The multilayer board is composed of components such as dielectric substrate 8, same layer 9 and prepreg 10. The functional components of the shielding cavity and antenna unit are designed in specific layers and form a spatial three-dimensional structure as a whole.

[0050] The circularly polarized antenna unit consists of a radiating patch 3, a feed plate 4, an antenna base plate 5, and a feed network 6. The feed network 6 is a cascaded 1-to-4 power divider formed by two Wilkins power dividers, which generates excitation signals with equal amplitude and phases distributed sequentially at 0° / 90° / 180° / 270° (or 0° / -90° / -180° / -270°), and outputs them to four sets of probe-type feed plates symmetrically arranged at 90-degree intervals. The probe-type feed plates couple energy to the circular radiating patch, thereby forming electromagnetic energy radiation into space.

[0051] The radiating plate of the circularly polarized antenna element is circular in shape and located on the top layer of a multilayer PCB laminate. It is a metal pattern created by etching the copper layer on the substrate surface. In this antenna design, the radiating plate of the circularly polarized antenna element can also be a square, rhombus, or other variations, or a combination of multiple small shapes. Furthermore, to meet the requirement of a larger operating bandwidth, parasitic patches of different shapes can be added to the radiating plate to introduce new resonant points, thereby expanding the operating bandwidth of the antenna element.

[0052] The feed plate of the circularly polarized antenna element includes a feed post 41 passing through the antenna base plate 5 and an "umbrella" shaped metal sheet. The "umbrella" shaped metal sheet includes a pad portion 42 connected to the end of the feed post, a transmission line segment 43 extending in the ±45° direction, and an end loading stub 44 at a 90-degree angle. The two segments 43 and 44 together form an "umbrella" shape.

[0053] The feed network 6 of the circularly polarized antenna element is a stripline structure. The antenna metal base plate 5 serves as the upper metal ground plane of the stripline structure, and the lower metal ground plane is the copper-clad layer of the substrate. The middle transmission line of the stripline structure is a metal pattern generated by etching the copper-clad layer on the surface of the dielectric substrate. The feed network 6 of the circularly polarized antenna consists of two stages of Wilkinson power dividers 61, 62, and 63. The four ports output excitation signals with equal power amplitude and phase distribution of 0° / 90° / 180° / 270° (or 0° / -90° / -180° / -270°) to excite the four sets of feed plates, realizing left-hand / right-hand circularly polarized antennas. Printed resistors 12 are integrated between the output ports of the three power dividers 61, 62, and 63 to improve the isolation between the output ports and to improve the phase distortion of the feed network output ports caused by impedance mismatch between the output ports of the feed network and the input ports of the antenna element.

[0054] The simulated standing wave curve and radiation pattern of the circularly polarized antenna embodiment are as follows: Figures 8-9As shown, this antenna element can cover a bandwidth of 24.25-27.5 GHz and has excellent impedance matching and radiation characteristics. Thanks to the equivalent shielded cavity design that integrates signal apertures, the circularly polarized antenna element adapted to it has excellent standing wave ratio and axial ratio in the entire operating bandwidth, with a VSWR < 1.2, an axial ratio < 1 dB, and an average radiation efficiency ≥ 80% in the entire operating bandwidth. This antenna element scheme can be regarded as an ideal choice for wide bandwidth angle scanning circularly polarized phased array antenna arrays.

Claims

1. A circularly polarized antenna element, comprising an equivalent shielding cavity and a radiating patch layer, a feeding patch layer, and a feeding network layer stacked sequentially; characterized in that, The radiating patch layer, the power feeding patch layer, and the power feeding network layer are all based on a multilayer laminated PCB board. The radiating patch layer includes a first dielectric substrate; a circular radiating patch is provided on the upper surface of the first dielectric substrate. The feed patch layer includes a second dielectric substrate; four feed patches are provided on the upper surface of the second dielectric substrate; the feed patches are symmetrically distributed at 90-degree intervals, and their center of symmetry is located directly below the center of the radiating patch; an antenna base plate is provided on the lower surface of the second dielectric substrate. The feed network layer includes a third dielectric substrate; a feed network is provided on the lower surface of the third dielectric substrate; the end ports of the feed network are all connected to the circular portion of the feed plate on top of the feed network through corresponding feed posts; the feed posts are not in contact with the antenna base plate; a lower metal ground plane is also provided below the feed network. Below the power supply network layer, a fourth dielectric substrate and a fifth dielectric substrate are sequentially disposed; the lower surface of the fourth dielectric substrate is provided with a lower metal ground plane; the lower surface of the fifth dielectric substrate has a surface microstrip line. The equivalent shielding cavity includes four coaxial signal holes with equal spacing between adjacent holes. The coaxial signal holes are distributed around the center of the radiating patch. Each coaxial signal hole includes edge through holes and a center through hole. There are four edge through holes, which are evenly distributed around the corresponding center through holes. The edge vias and center vias pass through the first dielectric substrate, the second dielectric substrate, the third dielectric substrate, the fourth dielectric substrate, and the fifth dielectric substrate sequentially from top to bottom; the lower surface of the third dielectric substrate is also provided with a first pad (23), and the center via is connected to the main feed port of the feed network through the first pad; the lower surface of the fifth dielectric substrate is also provided with a second pad (24); the center via is connected to the surface microstrip line through the second pad; The feed plate includes a circular portion and a rectangular portion; the circular portion and the rectangular portion are connected by a strip-shaped portion, and the central axes of the three portions coincide; the rectangular portion has wings on both sides of its end, and the included angle between the two wings is 90°; the two wings are symmetrical about the central axis of the rectangular portion. Four edge through holes form a square shape, and the corresponding center through hole is located at the center of the square shape; Multiple circular shielding structures are provided between adjacent coaxial signal holes; the circular shielding structures penetrate the first dielectric substrate, the second dielectric substrate and the third dielectric substrate.

2. The circularly polarized antenna element according to claim 1, characterized in that, The power supply network is a cascaded one-to-two Wilkinson power divider network forming a one-to-four power divider network.

3. A circularly polarized antenna element according to claim 2, characterized in that, Printed resistors (12) are integrated between the output ports of the three 1-to-2 power dividers of the power supply network.

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