A broadband dual circularly polarized antenna element and array

Abstract

The present invention relates to the technical field of antennas, and discloses a broadband dual-circularly polarized antenna element and an array. The antenna includes a first metal patch layer, a first dielectric layer, a second metal patch layer, a first adhesive layer, a second dielectric layer, a first feeder layer, a second adhesive layer, a third dielectric layer, a metal floor layer, a third adhesive layer, a fourth dielectric layer, and a second feeder layer arranged in sequence from top to bottom; the second metal patch layer is connected to the first feeder layer through a first metallized via and connected to the second feeder layer through a second metallized via; the two metallized vias are symmetrically arranged on the second metal patch layer; the first and second feeder layers include first and second microstrip lines connected to the first and second metallized vias; the antenna element has a simple structure and has a relatively wide impedance bandwidth and axial ratio bandwidth. In addition, the array constructed based on the antenna element has a high design flexibility, space utilization rate, and circular polarization purity, and has good dual-circular polarization performance.

Description

Technical Field

[0001] The present invention relates to the technical field of antennas, and particularly to a broadband dual circularly polarized antenna element and array. Background Art

[0002] With the rapid development of information technology and the continuous growth of mobile communication demands, the fifth-generation (5G) mobile communication has become the focus of the global communication field. In 5G communication, the millimeter-wave band is widely recommended for use to provide high data transmission rates and wide spectral resources. Compared with linearly polarized antennas, circularly polarized antennas are more suitable for millimeter-wave communication systems due to advantages such as suppressing multipath effects and reducing polarization mismatch. In addition, using dual circularly polarized antennas can achieve frequency reuse and polarization diversity, which can further improve the capacity and reliability of communication systems.

[0003] Microstrip patch antennas have become one of the most popular antenna types due to their compact structure and size, low cost, and simple fabrication. The most common way to achieve dual circularly polarized radiation through microstrip patch antennas is to use a hybrid coupler to excite the patch antenna. Although this method can achieve the required polarization characteristics, the hybrid coupler will increase the footprint of the feeding network, resulting in a larger antenna size, which is not conducive to the design of arrays.

[0004] In terms of bandwidth, it is quite difficult to achieve a microstrip patch antenna with both wide impedance and wide axial ratio bandwidths without significantly modifying the antenna and feeding structure. To increase the impedance bandwidth, a method of introducing parasitic elements around the main radiation patch can be adopted, but the introduced parasitic elements often lead to an increase in the antenna footprint. To increase the axial ratio bandwidth, many array designs use a sequential rotation feeding network, which can significantly increase the axial ratio bandwidth when the antenna element is expanded into a 2×2 sub-array. However, due to the relatively complex design of dual circularly polarized antenna arrays, previous studies have mainly focused on single circularly polarized antenna arrays. In addition, when the 2×2 array is expanded into a larger array, the axial ratio bandwidth and circular polarization purity designed by most studies hardly increase any more.

[0005] In the prior art, the following technical problems still exist in dual circularly polarized antenna elements and their arrays:

[0006] 1. Complicated structure and inflexible design: The realization of dual circular polarization usually depends on a complicated structure, and the phase and amplitude of each unit of the array need to be precisely controlled, which requires designing feeding networks corresponding to the two polarizations. This usually involves complicated branch and matching network designs. At the same time, the mutual influence between feeding networks and a large number of metallized vias will result in inflexible adjustment of the array.

[0007] 2. Low array space utilization rate: Existing dual circularly polarized antennas have problems with large element sizes and feed networks. When designing an array, it is necessary to increase the element spacing or expand the extra area to arrange the feed network. This results in insufficient compactness of the array and low space utilization rate of the antenna.

[0008] 3. Narrow impedance bandwidth: It is difficult for a microstrip patch antenna to achieve a wide impedance bandwidth without significantly modifying the antenna and feed structure. A narrow bandwidth will cause the antenna to be unable to effectively cover a wide frequency band, limiting the application scenarios in practical applications and reducing the practicality of the system.

[0009] 4. Poor polarization performance: Existing technical solutions do not fully consider the axial ratio bandwidth and circular polarization purity. Therefore, the axial ratio bandwidth of the antenna arrays studied in the past is generally narrow and cannot meet the requirements of broadband communication. At the same time, low circular polarization purity may lead to a decline in signal quality, affecting the overall performance and reliability of the antenna system. Summary of the Invention

[0010] To solve the above technical problems existing in the prior art, the present invention aims to provide an array and an antenna element constituting the array with low structural complexity, high array space utilization rate, wide impedance bandwidth, and excellent circular polarization performance.

[0011] In a first aspect, the present invention provides a broadband dual circularly polarized antenna element, specifically including: a first metal patch layer, a first dielectric layer, a second metal patch layer, a first adhesive layer, a second dielectric layer, a first feeder layer, a second adhesive layer, a third dielectric layer, a metal floor layer, a third adhesive layer, a fourth dielectric layer, and a second feeder layer arranged in sequence from top to bottom;

[0012] The first metal patch layer includes four equal-sized parasitic patches separated by a cross slot, with the same orientation and arranged in a 2×2 array; the shape of the parasitic patch is a hexagon obtained by cutting off a pair of diagonals of a square; among them, the cut-off part is an isosceles right triangle;

[0013] The second metal patch layer includes a main radiation patch, whose orientation and shape are the same as those of the parasitic patch, and the center and the intersection of the two axes of the cross slot are on the same vertical line;

[0014] The second metal patch layer is connected to the first feeder layer through a first metallized via;

[0015] The second metal patch layer is connected to the second feeder layer through a second metallized via; the metal floor layer is provided with a first annular isolation band around the second metallized via;

[0016] The first metallized via and the second metallized via are symmetrically arranged on the second metal patch layer, and the connection line is parallel to the hypotenuse of the isosceles right triangle;

[0017] The first feeder layer includes a first microstrip line connected to a first metallized via; the second feeder layer includes a second microstrip line connected to a second metallized via.

[0018] Preferably, for the parasitic patch, the side length of the square is 1.585 mm, and the right-angled side length of the isosceles right triangle is 0.7 mm; the width of the cross slot is 0.4 mm;

[0019] For the main radiation patch, the side length of the square is 2.18 mm, and the right-angled side length of the isosceles right triangle is 1.31 mm;

[0020] The thicknesses of the first dielectric layer, the second dielectric layer, and the fourth dielectric layer are 0.762 mm, 0.254 mm, and 0.1 mm respectively, and all are made of RO4350B material with a relative dielectric constant of 3.66 and a loss tangent of 0.0037;

[0021] The thickness of the third dielectric layer is 0.127 mm, and it is made of RO3010 material with a relative dielectric constant of 10.2 and a loss tangent of 0.0022;

[0022] The thicknesses of the first adhesive layer, the second adhesive layer, and the third adhesive layer are all 0.1 mm, and all are made of RO4450F material with a relative dielectric constant of 3.52 and a loss tangent of 0.004;

[0023] Both the first microstrip line and the second microstrip line are microstrip lines with a characteristic impedance of 50 Ω.

[0024] In a second aspect, the present invention provides a broadband dual circularly polarized antenna array, which is composed of broadband dual circularly polarized antenna elements; including,

[0025] 4 sub-arrays arranged on the same board material, arranged in a 2×2 array, with rotation angles of 0°, 90°, 180°, and 270° in sequence;

[0026] Each sub-array includes 4 antenna elements, arranged in a 2×2 array, with rotation angles of 0°, 90°, 180°, and 270° in sequence;

[0027] In each sub-array, the first microstrip lines of adjacent antenna elements are connected through a first T-junction power divider to form two first antenna element groups, and the two first antenna element groups are connected through a second T-junction power divider; adjacent sub-arrays are connected pairwise through a third T-junction power divider to form two first sub-array groups, and the two first sub-array groups are connected through a fourth T-junction power divider; the two first T-junction power dividers are directly connected to the second T-junction power divider, the second T-junction power divider is connected to the third T-junction power divider through a microstrip line, the third T-junction power divider is connected to the fourth T-junction power divider through a microstrip line, and the fourth T-junction power divider is connected to the connector through a microstrip line;

[0028] In each sub-array, the second microstrip lines of adjacent antenna elements are connected through a fifth T-junction power divider to form two groups of second antenna elements, and the two groups of second antenna elements are connected through a sixth T-junction power divider; adjacent sub-arrays are pairwise connected through a seventh T-junction power divider to form two groups of second sub-arrays, and the two groups of second sub-arrays are connected through an eighth T-junction power divider; the two fifth T-junction power dividers are directly connected to the sixth T-junction power divider, the sixth T-junction power divider is connected to the seventh T-junction power divider through a microstrip line, the seventh T-junction power divider is connected to the eighth T-junction power divider through a microstrip line, and the eighth T-junction power divider is connected to the connector through a microstrip line.

[0029] Preferably, the connection of the fourth T-junction power divider to the connector through a microstrip line is specifically as follows:

[0030] The fourth T-junction power divider is connected to the third metallized via through a microstrip line; the third metallized via is connected to the second feeder layer and is connected to the first coplanar waveguide through a microstrip line to connect to the connector;

[0031] A second annular isolation band is provided around the third metallized via in the metal floor layer;

[0032] The connection of the eighth T-junction power divider to the connector through a microstrip line is specifically as follows:

[0033] The eighth T-junction power divider is connected to the second coplanar waveguide through a microstrip line to connect to the connector.

[0034] Preferably, the characteristic impedance of both arms of all T-junction power dividers is 50Ω, and the characteristic impedance of the legs is 35Ω; the characteristic impedance of all microstrip lines is 50Ω.

[0035] Preferably, several fourth metallized vias penetrating the board are provided around the first coplanar waveguide and the second coplanar waveguide.

[0036] Preferably, on the same vertical line,

[0037] At the position corresponding to the first coplanar waveguide, an external metal patch is attached to the upper surface of the first dielectric layer;

[0038] At the position corresponding to the second coplanar waveguide, an external metal patch is attached to the upper surface of the first dielectric layer.

[0039] The broadband dual-circularly polarized antenna element provided by the present invention has a relatively wide impedance bandwidth, and has a relatively high circular polarization purity, and has good dual-circular polarization performance. In addition, the array constructed based on the broadband dual-circularly polarized antenna element has a relatively low structural complexity and a relatively high space utilization rate, and the two-layer feeders are independently adjustable. Further, the relatively high circular polarization purity of the dual-circularly polarized antenna helps to ensure the good state of the signal quality, and is an effective guarantee for the overall performance and reliability of the antenna back-end system. Description of the Drawings

[0040] Figure 1 Exploded view of the unit structure of the dual circularly polarized antenna element in the present invention.

[0041] Figure 2 Schematic plan view of the second metal patch layer of the antenna array in the present invention.

[0042] Figure 3 Schematic plan view of the first metal patch layer of the antenna array in the present invention.

[0043] Figure 4 Schematic plan view of the first feeder layer of the antenna array in the present invention.

[0044] Figure 5 Schematic plan view of the second feeder layer of the antenna array in the present invention.

[0045] Figure 6 Graph of the S-parameters and gain of the antenna element in the present invention varying with frequency.

[0046] Figure 7 Graph of the axial ratio and radiation efficiency of the antenna element in the present invention varying with frequency.

[0047] Figure 8 Graph of the S-parameters and gain of the antenna array in the present invention varying with frequency.

[0048] Figure 9 Graph of the axial ratio and radiation efficiency of the antenna array in the present invention varying with frequency.

[0049] Figure 10 Normalized radiation pattern at 27 GHz when the left-handed circularly polarized radiation port of the antenna array in the present invention is excited.

[0050] Figure 11 Normalized radiation pattern at 27 GHz when the right-handed circularly polarized radiation port of the antenna array in the present invention is excited.

[0051] Figure 12 Graph of the axial ratio of the left-handed circularly polarized antenna element, sub-array and array in the present invention varying with frequency.

[0052] Figure 13 Graph of the axial ratio of the right-handed circularly polarized antenna element, sub-array and array in the present invention varying with frequency.

[0053] The meanings of the labels in the figure are as follows: the first metal patch layer - 1; the second metal patch layer - 2; the metal pad ring - 3; the first annular isolation belt - 4; the metal floor layer - 5; the second feeder layer - 6; the first dielectric layer - 7; the first adhesive layer - 8; the second dielectric layer - 9; the second adhesive layer - 10; the third dielectric layer - 11; the third adhesive layer - 12; the fourth dielectric layer - 13; the first metallized via - 14; the first feeder layer - 15; the second metallized via - 16; the connector fixing hole - 17; the fourth metallized via - 18; the third metallized via - 19; the fourth T - junction power divider - 20; the third T - junction power divider - 21; the second T - junction power divider - 22; the first T - junction power divider - 23; the eighth T - junction power divider - 24; the seventh T - junction power divider - 25; the sixth T - junction power divider - 26; the fifth T - junction power divider - 27; the coplanar waveguide - 28. Detailed implementation manners

[0054] The technical solutions provided by the present invention will be further elaborated in detail below in combination with embodiments.

[0055] Term explanations:

[0056] (1) Left - Hand Circularly Polarized (LHCP): It is a form of electromagnetic wave polarization. In this polarization state, make a fist with the right hand, with the thumb pointing in the direction of wave propagation, and the rotation direction of the electric vector is opposite to that of the four fingers.

[0057] (2) Right - Hand Circularly Polarized (RHCP): It is a form of electromagnetic wave polarization. In this polarization state, make a fist with the right hand, with the thumb pointing in the direction of wave propagation, and the rotation direction of the electric vector is the same as that of the four fingers.

[0058] (3) Impedance Bandwidth (IBW): It is the frequency range of an electronic device (such as an antenna, amplifier, etc.) when its input or output impedance matches the nominal impedance. For the impedance bandwidth of dual - circular polarization, it is required that the reflection coefficients of both ports are less than - 10 dB and the port isolation is greater than 10 dB.

[0059] (4) Axial Ratio (AR): It represents the degree of uniformity of polarization characteristics in different directions. It is defined as the amplitude ratio between two orthogonal electric field components (usually the horizontal component and the vertical component) of the antenna. A circularly polarized antenna usually needs to satisfy an axial ratio less than 3 dB.

[0060] (5) Circular polarization purity: It is an index used to quantify and describe the quality of circularly polarized signals. Ideally, for perfect circular polarization, the axial ratio should be 1 (also known as 0 dB), indicating that the amplitudes of the two components are equal.

[0061] (6) Multipath effect: It is the situation where a signal reaches the receiver through multiple paths during transmission. These paths may be caused by reflection, diffraction, and scattering, etc.

[0062] (7) Polarization mismatch: It is the situation in a wireless communication system where the polarization state of the electromagnetic wave of the transmitted signal is inconsistent with the polarization state of the receiving antenna.

[0063] (8) Frequency reuse: It is a wireless communication technology aimed at improving the utilization rate of spectrum resources by transmitting multiple signals at the same or similar frequencies.

[0064] (9) Polarization diversity: It is a technology used in wireless communication systems, aiming to improve the transmission performance and anti-interference ability of signals by utilizing different polarization states of electromagnetic waves. This technology is especially suitable for multipath propagation environments and can reduce problems caused by signal fading and interference.

[0065] (10) Hybrid coupler: It is an important component used in antenna design and RF circuits. It can distribute the input signal to multiple output channels while maintaining a specific relationship of phase and amplitude.

[0066] (11) Parasitic patch: In antenna design, parasitic patches can be additional elements in the antenna structure. They are not directly powered but affect the radiation characteristics of the main antenna through electromagnetic coupling. When the size, shape, and position of these parasitic patches are reasonably configured with the main antenna, parameters such as the gain, directivity, or bandwidth of the antenna can be improved.

[0067] (12) Sequential rotation technique: It is a unit arrangement scheme often adopted in the design of circularly polarized antenna arrays. The sequential rotation technique requires the antenna elements to rotate a certain angle around their geometric centers. At the same time, the feeding phase and the rotation angle need to satisfy a certain relationship, and the rotation angles and feeding phase distributions of each element must be sequential.

[0068] (13) Radiation pattern: The radiation pattern of an antenna refers to the curve of the relative field strength (normalized modulus value) of the radiation field changing with direction at a certain distance from the antenna. It is usually represented by two mutually perpendicular plane patterns passing through the maximum radiation direction of the antenna.

[0069] (14) Port isolation: It is the degree of mutual interference between ports in a multi-port antenna system. The higher the port isolation, the less interference between ports and the better the signal independence.

[0070] (15) Characteristic impedance: In a transmission line, it is the ratio of voltage to current, representing the impedance characteristics of the transmission line to signals. Characteristic impedance is usually denoted by the letter Z 0 and its unit is ohm (Ω).

[0071] (16) Spurious radiation: It is the electromagnetic wave radiated by an electronic device or system at an unintended frequency. These waves are usually not signals generated by the normal operation of the device. Spurious radiation may interfere with the normal operation of other devices or affect the performance of the entire wireless communication environment.

[0072] (17) Degenerate mode: In antennas and other electromagnetic structures, it refers to different propagation modes (such as different electromagnetic wave modes) having the same frequency or the same characteristics.

[0073] (18) TM 10 wave: It is a specific type of transverse electromagnetic wave. Here, "1" indicates the existence of an electric field fluctuation in one direction, and "0" indicates no rapid change in the other direction (usually the width direction).

[0074] (19) Surface wave: It is an electromagnetic wave that propagates along the surface of an object, usually involving the propagation of electromagnetic waves at the interface of a conductor or a medium.

[0075] (20) Reflection coefficient S 11 : It is the ratio of the incident wave power to the reflected wave power. The unit is dB, and its value depends on the reflection condition reflected to the input port after the joint action of the transmission system and the load. The smaller the S 11 value, the better the matching of the incident signal at the port, the less the reflection, and the corresponding less energy loss.

[0076] (21) Gain: Under the condition of the same input power, it is the ratio of the signal power density generated by an actual antenna and an ideal radiation unit at the same point in space. It quantifies the ability of the antenna to concentrate and radiate the input power. Gain is closely related to the radiation pattern of the antenna. The narrower the main lobe and the smaller the side lobes, the higher the gain.

[0077] (22) Radiation efficiency: It is the ratio of the antenna radiation power to the input power, referring to the ability of the antenna to effectively convert the input power into radiation power, usually expressed as a percentage.

[0078] (23) Half-power beamwidth: It is a physical quantity that measures the sharpness of the maximum radiation area of an antenna. It takes the width between two half-power points of the main lobe of the radiation pattern. In the field strength radiation pattern, it is equal to the width between two points of the maximum field strength between two points.

[0079] (24)Sidelobe level: It is the level of the first sidelobe that is closest to and has the highest level among all sidelobes, generally expressed in dB. The sidelobe region of the radiation pattern is the area where radiation is not required, so its level should be as low as possible.

[0080] (25)Cross-polarization level: It is the ratio of the power of the cross-polarization component (the polarization component perpendicular to the required polarization direction) to the power of the co-polarization component (i.e., the specified circular polarization direction, such as left-handed or right-handed). Similar to the cross-polarization level of a linearly polarized antenna, it is used to evaluate the polarization characteristics and interference situation of the antenna when transmitting or receiving signals.

[0081] As Figure 1 shown, the unit structure of the dual circularly polarized antenna unit provided by the present invention is a stacked structure, that is, each antenna unit from top to bottom is successively a first metal patch layer 1, a first dielectric layer 7, a second metal patch layer 2, a first adhesive layer 8, a second dielectric layer 9, a first feeder layer 15, a second adhesive layer 10, a third dielectric layer 11, a metal floor layer 5, a third adhesive layer 12, a fourth dielectric layer 13 and a second feeder layer 6, as well as a first metallized via 14 and a second metallized via 16 for electrical connection. The radiation part of the dual circularly polarized antenna unit includes the first metal patch layer 1 and the second metal patch layer 2. The first metal patch layer 1 is four parasitic patches, which are formed by diagonally cutting four square patches. The second metal patch layer 2 is the main radiation patch, which is formed by diagonally cutting a square patch. The geometric shapes of the various parts of the main radiation patch and the parasitic patches are similar, only the sizes are different. Stacked patches expand the impedance bandwidth of the antenna, while diagonal cutting can achieve better circular polarization performance. The first feeder layer 15 is located between the second dielectric layer 9 and the second adhesive layer 10 and includes a vertically arranged microstrip line. The second feeder layer 6 is located below the fourth dielectric layer 13 and includes a vertically arranged microstrip line, which is connected to the main radiation patch layer (the second metal patch layer 2) through the second metallized via 16. Among them, when the excitation is at different ports of the two feeder layers, the antenna will radiate electromagnetic waves of different polarizations.

[0082] As Figure 2As shown, through the array design of the second metal patch layer 2, it can be seen that the array design adopts the sequential rotation technique. First, the antenna elements are arranged into a 2×2 sub-array on the same board. Among them, the board is equivalent to seamless splicing of multiple antenna elements, so its stacked structure is the same as that of the antenna elements. The center-to-center spacing of adjacent elements is 0.7 times the wavelength, that is, 7.8 mm. To meet the excitation phases and amplitudes of the four elements, a microstrip line is used to design the feeding network. Rotating in the clockwise direction, a progressive phase difference of ±90° is achieved between adjacent elements, that is, left-handed circular polarization radiation +90° and right-handed circular polarization radiation -90°. To further improve the gain, axial ratio bandwidth, and circular polarization purity of the antenna, 4 2×2 sub-arrays are further combined into an array at the 2×2 sub-array level. Two-stage sequential rotation alignment is provided on the four sub-arrays. Rotating in the clockwise direction, the feeding phases between adjacent sub-arrays are successively -90° for left-handed circular polarization radiation and successively +90° for right-handed circular polarization radiation. The one-stage sequential rotation feeding network of the sub-array and the two-stage feeding network are connected together to form a second-order sequential rotation feeding network. The feeding network of this array design can simplify the complexity, control the array area, increase the design flexibility, and improve the port isolation.

[0083] Specifically, the antenna elements are fed in the orthogonal direction to achieve circular polarization radiation of different rotation directions. That is, the second metal patch layer 2 is connected to the first feeder layer 15 by the first metallized via 14, and the second metal patch layer 2 is connected to the second feeder layer 6 by the second metallized via 16. The second metal patch layer 2 is connected to the first feeder layer 15 through the first metallized via 14 that successively passes through the first adhesive layer 8 and the second dielectric layer 9; the second metal patch layer 2 is connected to the second feeder layer 6 through the second metallized via 16 that successively passes through the first adhesive layer 8, the second dielectric layer 9, the second adhesive layer 10, the third dielectric layer 11, the metal floor layer 5, the third adhesive layer 12, and the fourth dielectric layer 13; the two metallized vias are symmetrically arranged on the second metal patch layer 2, and the connection line is parallel to the hypotenuse obtained by cutting off a pair of diagonals.

[0084] To achieve good electrical isolation between the second metallized via 16 and the metal floor layer 5, an isolation ring is added with the center of the second metallized via 16 as the center, that is, the first annular isolation band 4 is arranged around the second metallized via 16. At the same time, a metal pad ring 3 with a radius smaller than the isolation ring is added with the center of the second metallized via 16 as the center. Adjusting the sizes of the isolation ring and the metal pad ring 3 can adjust the impedance matching of the port and increase the design flexibility. It should be noted that the isolation ring is essentially an annular isolation band formed by cutting off a part of the metal floor layer 5. The metal pad ring 3 replaces the cut-off part of the metal floor layer 5 and serves as a lining to support the metallization of the second metallized via 16 to achieve the up-and-down interconnection of the second metallized via 16.

[0085] In the antenna element, the antenna impedance bandwidth is expanded by stacking multiple metal patches. The main radiation patch and the parasitic patch are both initially square patches, stacked vertically, and their centers are on the same vertical line. To achieve circularly polarized radiation, the square main radiation patch with a side length of 2.78 mm is diagonally cut off, and the cut-off area is two isosceles right triangles with right-angled sides of 1.31 mm. By cutting the corners of the main radiation patch, the degenerate modes can be separated from each other and have a 90° phase difference, thus meeting the generation conditions of circular polarization. The planar structure of the first metal patch layer 1 is as shown in Figure 3 shown. To improve the gain flatness in the target frequency band, a cross slot with a width of 0.4 mm is loaded on the square parasitic patch with a side length of 3.57 mm. The cross slot divides the parasitic patch into four small metal patches of the same size. To improve the axial ratio bandwidth of the antenna, the four parts of the split parasitic patch are diagonally cut off in the same orientation as the main radiation patch, and the cut-off part is an isosceles right triangle with a right-angled side of 0.7 mm. Finally, it becomes the appearance of the patches of the first metal patch layer 1 and the second metal patch layer 2.

[0086] Among them, the first dielectric layer 7, the second dielectric layer 9, and the fourth dielectric layer 13 are made of Rogers RO4350B board, with a relative dielectric constant of 3.66 and a loss tangent of 0.0037. The thicknesses of the three dielectric layers are 0.762 mm, 0.254 mm, and 0.1 mm in sequence. The third dielectric layer 11 is made of Rogers RO3010 board, with a relative dielectric constant of 10.2 and a loss tangent of 0.0022, and the thickness is 0.127 mm. The first adhesive layer 8, the second adhesive layer 10, and the third adhesive layer 12 are made of Rogers RO4450F board, with a relative dielectric constant of 3.52 and a loss tangent of 0.004, and the thickness of each is 0.1 mm.

[0087] The array contains 16 circularly polarized radiation units, which can be regarded as composed of 4 2×2 sub-arrays. In a single 2×2 sub-array, the rotation angles of the 4 units are 0°, 90°, 180°, and 270° in sequence. In the design of the feeding network of the 2×2 sub-array, along the clockwise direction, a progressive phase difference of ±90° is achieved between adjacent units, that is, the left-handed circular polarization radiation is +90° and the right-handed circular polarization radiation is -90°, forming a first-stage sequential rotation feeding network. When forming a large array, along the clockwise direction, the feeding phase delay between adjacent sub-arrays is -90° for left-handed circular polarization radiation and +90° for right-handed circular polarization radiation. The first-stage sequential rotation feeding network of the sub-array is connected to the second-stage feeding network to form a second-order sequential rotation feeding network, thereby achieving wide axial ratio and high polarization purity performance.

[0088] To more intuitively observe the feeding phase distribution of each unit, Table 1 gives the ideal feeding phase values of each unit, that is, for left-handed circular polarization radiation, the feeding phase of each unit is For right - hand circularly polarized radiation, the feeding phase of each unit is .

[0089] Table 1 Ideal values of feeding phases

[0090] .

[0091] In the present invention, the feeders of the antenna element and the array are distributed on different layers. This dual - feeder layer design has the following advantages:

[0092] 1. It can achieve a lower structural complexity compared with the traditional dual - circularly polarized feeding network, simplifying the design. At the same time, the two feeding layers with different polarizations can be independently designed and adjusted, enabling a more flexible routing arrangement.

[0093] 2. Ensure that the antenna feeding network can be constrained within the footprint of the array without adding other extra areas. Thus, it guarantees the compact design of the array and high space utilization.

[0094] 3. The two feeding network layers are separated by the metal floor layer 5, which can obtain better isolation and improve the performance of the unit and the array.

[0095] Since there is no metal floor layer separating the right - hand circularly polarized radiation feeding network and the second metal patch layer, the right - hand circularly polarized radiation feeding network will affect the radiation characteristics of the array. To reduce its influence, the third dielectric layer 11 uses Rogers RO3010 board material, and its dielectric constant as high as 10.2 can well confine the guided wave propagated by the right - hand circularly polarized radiation feeding network within the substrate, with only weak stray radiation, which can be basically ignored.

[0096] The schematic plan view of the first feeder layer 15 of the right - hand circularly polarized feeding network is as Figure 4 shown. It consists of a cascaded T - junction power divider and microstrip lines. The signal enters the feeding network from the third metallized via 19, and after passing through the fourth T - junction power divider 20 and the third T - junction power divider 21, the signal is divided into four paths and enters the sub - array feeding network. After the signal enters the sub - array feeding network, it is divided into four paths again after passing through the second T - junction power divider 22 and the first T - junction power divider 23, thus forming a one - to - sixteen feeding network.

[0097] Similarly, the schematic plan view of the second feeder layer 6 of the left - hand circularly polarized feeding network is as Figure 5As shown, the signal enters the feeding network from the coplanar waveguide 28. After passing through the eighth T-junction power divider 24 and the seventh T-junction power divider 25, the signal is divided into four paths and enters the sub-array feeding network. After passing through the sixth T-junction power divider 26 and the fifth T-junction power divider 27, the signal is further divided into four paths. The input ends of all T-junction power dividers in the feeding network are microstrip lines with a characteristic impedance of 35 Ω and a quarter-wavelength length, and the two arms are microstrip lines with a characteristic impedance of 50 Ω. The 50-Ω microstrip lines are used for connection at different stages.

[0098] Among them, the third metallized via 19 is connected to the second feeder layer 6, and on the second feeder layer 6, it is connected to another coplanar waveguide (not the coplanar waveguide 28) through a microstrip line. Connector fixing holes 17 penetrating the entire board (i.e., penetrating from the first metal patch layer to the second feeder layer) are provided on both coplanar waveguides for fixing external connectors. Around the connector fixing holes 17, several fourth metallized vias 18 penetrating the board are provided. The structure where the third metallized via 19 passes through the metal floor layer 5 is the same as the structure where the second metallized via 16 passes through the metal floor layer 5.

[0099] Among them, there are two rows of fourth metallized vias 18 between the two connector fixing holes 17 and perpendicular to the connection line between them. As Figure 5 shown, the microstrip line connecting the eighth T-junction power divider 24 extends into the space between the two rows of fourth metallized vias 18 at the edge of the board. The extending part, together with the two rows of fourth metallized vias 18 and two first external metal patches, constitutes the coplanar waveguide 28. Among them, the first external metal patches are pasted within two rectangular areas formed by several fourth metallized vias 18 surrounding the connector fixing holes 17.

[0100] On the other side, the microstrip line connecting the third metallized via 19 extends into the space between the two rows of fourth metallized vias 18. The extending part, together with the two rows of fourth metallized vias 18 and two other first external metal patches, constitutes another coplanar waveguide for connecting the connector.

[0101] As Figure 3 shown, corresponding to the positions of two pairs of connector fixing holes 17, two second external metal patches are also pasted on the upper surface of the first dielectric layer 7. Different from that one first external metal patch only covers one connector fixing hole 17, one second external metal patch covers two connector fixing holes 17, that is, on the upper surface of the first dielectric layer 7, one second external metal patch is pasted corresponding to the position of one coplanar waveguide. It can be seen that in the same antenna array, a total of 6 external metallized patches are provided to ensure good grounding continuity when the connectors are connected.

[0102] As Figure 6As shown, the curves of the S-parameters and gain of the antenna element varying with frequency. In the frequency band of 20.2 GHz to 30.5 GHz, the reflection coefficients S 11 and S 22 of the left-handed circular polarization port and the right-handed circular polarization port are both lower than -10 dB. In the frequency band of 23 GHz to 34 GHz, the port isolation is greater than 10 dB. The antenna element has a relatively wide impedance bandwidth. The gains at the center frequency of 27 GHz are both about 5.6 dBic, and the gain responses are flat on both sides of the center frequency.

[0103] As Figure 7 shown, the curves of the axial ratio and radiation efficiency of the antenna element varying with frequency. The 3-dB axial ratio bandwidth of the left-handed circular polarization beam of the antenna element is 23% (23.7 GHz to 29.9 GHz), and the 3-dB axial ratio bandwidth of the right-handed circular polarization beam is greater than 30.7% (>20 GHz to 28.3 GHz), with good circular polarization performance and a relatively wide axial ratio bandwidth. The difference in the axial ratio bandwidth between the two ports is mainly caused by the different layer distributions of the feed lines, which will be improved in the array. In the shown frequency band, the radiation efficiency is greater than 95.6%.

[0104] As Figure 8 shown, the curves of the S-parameters and gain of the antenna array varying with frequency. In the frequency band of 20 GHz to 32.9 GHz, the reflection coefficients S 11 and S 22 of the left-handed circular polarization port and the right-handed circular polarization port are both lower than -10 dB, and the port isolation is greater than 10 dB. The peak gains of the left-handed circular polarization beam and the right-handed circular polarization beam are 17 dBic and 16 dBic respectively, and the 3-dB gain bandwidth is 36.3% (20.7 GHz to 30.5 GHz).

[0105] As Figure 9 shown, the curves of the axial ratio and radiation efficiency of the antenna array varying with frequency. In the frequency band, the average radiation efficiency of the left-handed circular polarization and right-handed circular polarization beams is 67%. The 3-dB axial ratio bandwidth of the left-handed circular polarization beam is greater than 51.9% (>20 GHz to 34 GHz), and the 3-dB axial ratio bandwidth of the right-handed circular polarization beam is greater than 49.6% (20.6 GHz to 34 GHz).

[0106] As Figure 10 shown, the normalized radiation pattern of the antenna array at 27 GHz when the left-handed circular polarization radiation port is excited. The half-power beamwidth is about 17.6°, the peak sidelobe level is lower than -10 dB, and the axial cross-polarization levels are all less than -25 dB.

[0107] As Figure 11As shown, the normalized radiation pattern at 27 GHz when the antenna array is excited at the right - hand circular polarization radiation port. Approximately, the half - power beamwidth is about 18°, the peak sidelobe level is below - 10 dB, and the axial cross - polarization levels are all less than - 25 dB. The radiations of both polarizations have approximately excellent performance. At the same time, the high similarity between the left - hand circular polarization and right - hand circular polarization results also indicates that the stray radiation of the right - hand circular polarization feeding network has little influence on the radiation characteristics of the array.

[0108] As Figure 12 shown, the curves of the axial ratio of the left - hand circular polarization antenna element, sub - array and array varying with frequency. As Figure 13 shown, the curves of the axial ratio of the right - hand circular polarization antenna element, sub - array and array varying with frequency. When expanded into an array, both the axial ratio bandwidth and the circular polarization purity are further improved.

[0109] The technical solutions provided by the present invention have the following advantages:

[0110] 1. Simple element design: The antenna element adopts a stacked patch design. By adding a parasitic patch above the main radiation patch, the impedance bandwidth is improved. At the same time, the main radiation patch and the parasitic patch are subjected to similar diagonal cuts to achieve a relatively wide axial ratio bandwidth. Furthermore, two metallized vias are used for direct feeding in orthogonal directions.

[0111] 2. Separating the feeding networks of the two polarizations above and below the metal ground plane: The present invention reduces the complexity of the antenna array, restricts the floor area of the feeding network, obtains good isolation and increases the design flexibility. At the same time, to reduce the influence of the feeding circuit on the upper side of the metal ground plane on the radiation characteristics of the array, a layer of high - dielectric - constant material is added between them.

[0112] 3. Using a second - order sequential rotation feeding design for the array: To improve the axial ratio bandwidth, many array designs adopt a sequential rotation feeding network. However, most of them are only single - circular - polarization antenna arrays. And when a 2×2 array is expanded into a larger array, the axial ratio bandwidth and circular polarization purity of most designs hardly improve any more. The present invention uses a sequential rotation feeding strategy to expand the proposed dual - circular - polarization antenna element into a 2×2 sub - array. When expanded to 4×4 (for the antenna element), the four sub - arrays are then sequentially rotated and distributed at 90°, providing a second - stage sequential rotation alignment at the sub - array level. Further improving the broadband performance and polarization purity of the dual - circular - polarization radiation.

[0113] In summary, the broadband dual-circularly polarized antenna element provided by the present invention has a simple structure, a relatively wide impedance bandwidth and axial ratio bandwidth. In addition, the array constructed based on the broadband dual-circularly polarized antenna element not only has a relatively wide impedance bandwidth and axial ratio bandwidth, but also has a high design flexibility, space utilization rate and circular polarization purity, and has good dual-circular polarization performance. Further, the high circular polarization purity of the dual-circularly polarized antenna array helps to ensure the good state of the signal quality, which is an effective guarantee for the overall performance and reliability of the antenna system.

[0114] Further, on the basis of achieving the above beneficial effects, each preferred solution has also achieved the following beneficial effects: The specific dimensions and material settings of the antenna element can ensure the circular polarization purity; the setting of the double coplanar waveguide and the connector fixing hole can realize efficient signal transmission between the antenna array and the connector; the fourth metallized via and the external metal patch can ensure good grounding continuity when the connector is connected.

Claims

1. A broadband dual circular polarization antenna unit, characterized in that: The invention comprises, arranged in order from top to bottom, a first metal patch layer (1), a first dielectric layer (7), a second metal patch layer (2), a first adhesive layer (8), a second dielectric layer (9), a first feeder layer (15), a second adhesive layer (10), a third dielectric layer (11), a metal floor layer (5), a third adhesive layer (12), a fourth dielectric layer (13) and a second feeder layer (6); The first metal patch layer (1) comprises four parasitic patches of equal size separated by a cross groove, oriented in the same direction, and arranged in a 2×2 array; the shape of the parasitic patch is a hexagon obtained by cutting off a pair of diagonals of a square; wherein the cut-off portion is an isosceles right triangle; The second metal patch layer (2) includes a main radiation patch, the orientation and shape of which are consistent with those of the parasitic patch, and the center of which is located on the same vertical line as the intersection of the two axes of the cross slot; The second metal patch layer (2) is connected to the first feeder layer (15) via a first metallized via (14); The second metal patch layer (2) is connected to the second feeder layer (6) via a second metallized via hole (16); the metal floor layer (5) is provided with a first annular isolation zone (4) around the second metallized via hole (16); The first metallized via (14) and the second metallized via (16) are symmetrically arranged on the second metal patch layer (2), and the connecting line is parallel to the hypotenuse of the isosceles right triangle; The first feed line layer (15) comprises a first microstrip line connected to a first metallized via hole (14); and the second feed line layer (6) comprises a second microstrip line connected to a second metallized via hole (16).

2. A broadband dual circular polarization antenna unit as claimed in claim 1, characterized in that: Parasitic patch, the side length of the square is 1.585mm, the right angle length of the isosceles right triangle is 0.7mm; the width of the cross slot is 0.4mm; The main radiation patch has a square side length of 2.18 mm and an isosceles right triangle side length of 1.31 mm; The thicknesses of the first dielectric layer (7), the second dielectric layer (9) and the fourth dielectric layer (13) are 0.762 mm, 0.254 mm and 0.1 mm respectively, and all are made of RO4350B material with a relative dielectric constant of 3.66 and a loss tangent of 0.0037; The third dielectric layer (11) has a thickness of 0.127 mm and is made of RO3010 material with a relative dielectric constant of 10.2 and a loss tangent of 0.0022; The first adhesive layer (8), the second adhesive layer (10) and the third adhesive layer (12) are all 0.1 mm thick and are all made of RO4450F material with a relative dielectric constant of 3.52 and a loss tangent of 0.004; The first microstrip line and the second microstrip line are both microstrip lines with a characteristic impedance of 50Ω.

3. A broadband dual circular polarization antenna array, characterized in that: Composed of the broadband dual circularly polarized antenna unit as claimed in claim 1; include, The four sub-arrays set on the same plate are arranged in a 2×2 array, with rotation angles of 0°, 90°, 180°, and 270° respectively; Each subarray consists of 4 antenna elements arranged in a 2×2 array, with rotation angles of 0°, 90°, 180°, and 270°; In each subarray, the first microstrip lines of adjacent antenna units are connected via a first T-junction power divider (23) to form two first antenna unit groups, and the two first antenna unit groups are connected via a second T-junction power divider (22); adjacent subarrays are connected in pairs via a third T-junction power divider (21) to form two first subarray groups, and the two first subarray groups are connected via a fourth T-junction power divider (20); the two first T-junction power dividers (23) are directly connected to the second T-junction power divider (22), the second T-junction power divider (22) is connected to the third T-junction power divider (21) via a microstrip line, the third T-junction power divider (21) is connected to the fourth T-junction power divider (20) via a microstrip line, and the fourth T-junction power divider (20) is connected to a connector via a microstrip line; In each subarray, the second microstrip lines of adjacent antenna units are connected via a fifth T-junction power divider (27) to form two second antenna unit groups, and the two second antenna unit groups are connected via a sixth T-junction power divider (26); adjacent subarrays are connected in pairs via a seventh T-junction power divider (25) to form two second subarray groups, and the two second subarray groups are connected via an eighth T-junction power divider (24); the two fifth T-junction power dividers (27) are directly connected to the sixth T-junction power divider (26), the sixth T-junction power divider (26) is connected to the seventh T-junction power divider (25) via a microstrip line, the seventh T-junction power divider (25) is connected to the eighth T-junction power divider (24) via a microstrip line, and the eighth T-junction power divider (24) is connected to a connector via a microstrip line.

4. A broadband dual circular polarization antenna array as claimed in claim 3, characterized in that: The fourth T-junction power divider (20) is connected to the connector via a microstrip line as follows: The fourth T-junction power divider (20) is connected to the third metallized via (19) via a microstrip line; the third metallized via (19) is connected to the second feeder layer (6), and is connected to the first coplanar waveguide via the microstrip line to connect to the connector; The metal floor layer (5) is provided with a second annular isolation zone around the third metallized via hole (19); The eighth T-junction power divider (24) is connected to the connector via a microstrip line as follows: The eighth T-junction power divider (24) is connected to the second coplanar waveguide via a microstrip line to connect to the connector.

5. A broadband dual circular polarization antenna array as claimed in any one of claims 3 or 4, characterized in that: The characteristic impedance of both arms of all T-junction power dividers is 50Ω, and the characteristic impedance of the legs is 35Ω; the characteristic impedance of all microstrip lines is 50Ω.

6. A broadband dual circular polarization antenna array as claimed in claim 4, characterized in that: A plurality of fourth metallized via holes (18) penetrating the plate are arranged around the first coplanar waveguide and the second coplanar waveguide.

7. A broadband dual circular polarization antenna array as claimed in claim 4, characterized in that: On the same vertical line, corresponding to the position of the first coplanar waveguide, an external metal patch is attached to the upper surface of the first dielectric layer (7); corresponding to the position of the second coplanar waveguide, an external metal patch is attached to the upper surface of the first dielectric layer (7).

Images