Broadband dual circularly polarized antenna unit and array

Abstract

The invention relates to the technical field of antennas, and discloses a broadband dual circularly polarized antenna unit and array. The antenna comprises a first metal patch layer, a first dielectric layer, a second metal patch layer, a first bonding layer, a second dielectric layer, a first feeder line layer, a second bonding layer, a third dielectric layer, a metal floor layer, a third bonding layer, a fourth dielectric layer and a second feeder line layer which are sequentially arranged from top to bottom, the second metal patch layer is connected to the first feeder line layer through a first metalized via hole and is connected to the second feeder line layer through a second metalized via hole; the two metalized via holes are symmetrically arranged on the second metal patch layer; the first feeder layer and the second feeder layer comprise a first microstrip line and a second microstrip line which are connected to the first metalized via hole and the second metalized via hole; the antenna unit is simple in structure and has wide impedance bandwidth and axial ratio bandwidth. In addition, an array constructed based on the antenna unit has relatively 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 field of antenna technology, and in particular to a broadband dual circular polarization antenna unit and an array. Background Art

[0002] With the rapid development of information technology and the growing demand for mobile communications, the fifth generation (5G) mobile communications have become the focus of the global communications field. In 5G communications, the millimeter wave frequency band is widely recommended to provide high data transmission rates and wide spectrum resources. Compared with linear polarization antennas, circularly polarized antennas are more suitable for millimeter wave communication systems because of their advantages such as suppressing multipath effects and reducing polarization mismatch. In addition, the use of 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 are one of the most popular types of antennas due to their compact structure and size, low cost, and simple manufacturing. The most common way to achieve dual circular polarization radiation through microstrip patch antennas is to use a hybrid coupler to excite the patch antenna. Although this method can achieve the desired polarization characteristics, the hybrid coupler increases the footprint of the feed network, resulting in a larger antenna size, which is not conducive to the design of the array.

[0004] In terms of bandwidth, it is quite difficult to realize a microstrip patch antenna with both wide impedance and wide axial ratio bandwidth without significantly modifying the antenna and feeding structure. To improve the impedance bandwidth, the method of introducing parasitic elements around the main radiating patch can be adopted, but the introduction of parasitic elements often leads to an increase in the antenna footprint. To improve the axial ratio bandwidth, many array designs use sequential rotation feeding networks, which can significantly improve the axial ratio bandwidth when the antenna unit is expanded to a 2×2 subarray. However, due to the complexity of the design of dual circularly polarized antenna arrays, previous studies have only tended to focus on single circularly polarized antenna arrays. In addition, when the 2×2 array is expanded to a larger array, the axial ratio bandwidth and circular polarization purity of most research designs are hardly improved.

[0005] In the prior art, dual circular polarization antenna units and arrays thereof still have the following technical problems: 1. Complex structure and inflexible design: The realization of dual circular polarization usually relies on complex structure, and the phase and amplitude of each unit of the array need to be precisely controlled, which requires the design of two polarization corresponding feeding networks. This usually involves complex branch and matching network design. At the same time, the mutual influence between the feeding networks and a large number of metallized vias will make the adjustment of the array inflexible.

[0006] 2. Low array space utilization: Existing dual circular polarization antennas have problems with large unit size and feed network. When designing the array, the unit spacing must be enlarged or additional area must be added to arrange the feed network. This results in insufficient compactness of the array and low space utilization of the antenna.

[0007] 3. Narrow impedance bandwidth: It is difficult to achieve a wide impedance bandwidth for microstrip patch antennas without significant modification of the antenna and feed structure. The narrow bandwidth will result in the antenna being unable to effectively cover a wide frequency band, limiting the application scenarios in actual applications and reducing the practicality of the system.

[0008] 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 antenna arrays studied in the past is generally narrow and cannot meet the needs of broadband communication; at the same time, low circular polarization purity may lead to a decrease in signal quality, affecting the overall performance and reliability of the antenna system. Summary of the invention

[0009] In order to solve the above technical problems existing in the prior art, the present invention aims to provide an array with low structural complexity, high array space utilization, wide impedance bandwidth and excellent circular polarization performance, and antenna units constituting the array.

[0010] In a first aspect, the present invention provides a broadband dual circular polarization antenna unit, specifically comprising: 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 first metal patch layer includes 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 part is an isosceles right triangle; The second metal patch layer includes a main radiation patch, the orientation and shape of which are consistent with the parasitic patch, and the center and the intersection of the two axes of the cross slot are located on the same vertical line; The second metal patch layer is connected to the first feeder layer via the first metallized via; The second metal patch layer is connected to the second feeder layer via a second metallized via hole; the metal floor layer is provided with a first annular isolation zone around the second metallized via hole; The first metallized via and the second metallized via are symmetrically arranged on the second metal patch layer, and the connecting line is parallel to the hypotenuse of the isosceles right triangle; The first feed line layer includes a first microstrip line connected to a first metallized via hole; the second feed line layer includes a second microstrip line connected to a second metallized via hole.

[0011] Preferably, the parasitic patch has a square side length of 1.585 mm, an isosceles right triangle side length of 0.7 mm, and a cross slot width of 0.4 mm; 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, the second dielectric layer and the fourth dielectric layer are 0.762mm, 0.254mm and 0.1mm respectively, and all are made of RO4350B material with a relative dielectric constant of 3.66 and a loss tangent of 0.0037; The thickness of the third dielectric layer is 0.127mm, and it is made of RO3010 material with a relative dielectric constant of 10.2 and a loss tangent of 0.0022; The thickness of the first adhesive layer, the second adhesive layer and the third adhesive layer are all 0.1mm, and all are 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.

[0012] In a second aspect, the present invention provides a broadband dual circular polarization antenna array, which is composed of broadband dual circular polarization antenna units; including: 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°; 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 to form two first antenna unit groups, and the two first antenna unit groups are connected via a second T-junction power divider; adjacent subarrays are connected in pairs via a third T-junction power divider to form two first subarray groups, and the two first subarray groups are connected via 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 via a microstrip line, the third T-junction power divider is connected to the fourth T-junction power divider via a microstrip line, and the fourth T-junction power divider is connected to the 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 to form two second antenna unit groups, and the two second antenna unit groups are connected via a sixth T-junction power divider; adjacent subarrays are connected in pairs via a seventh T-junction power divider to form two second subarray groups, and the two second subarray groups are connected via 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 via a microstrip line, the seventh T-junction power divider is connected to the eighth T-junction power divider via a microstrip line, and the eighth T-junction power divider is connected to the connector via a microstrip line.

[0013] Preferably, the fourth T-junction power divider is connected to the connector via a microstrip line as follows: The fourth T-junction power divider is connected to the third metallized via via a microstrip line; the third metallized via is connected to the second feeder layer, and is connected to the first coplanar waveguide via a microstrip line to connect to the connector; The metal floor layer is provided with a second annular isolation zone around the third metallized via hole; The eighth T-junction power divider is connected to the connector via a microstrip line as follows: The eighth T-junction power divider is connected to the second coplanar waveguide via a microstrip line to connect to the connector.

[0014] 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.

[0015] Preferably, a plurality of fourth metallized vias penetrating the plate are provided around the first coplanar waveguide and the second coplanar waveguide.

[0016] Preferably, on the same vertical line, An external metal patch is attached to the upper surface of the first dielectric layer corresponding to the position of the first coplanar waveguide; Corresponding to the position of the second coplanar waveguide, an external metal patch is attached to the upper surface of the first dielectric layer.

[0017] The broadband dual circularly polarized antenna unit provided by the present invention has a wide impedance bandwidth, high circular polarization purity, and good dual circular polarization performance. In addition, the array constructed based on the broadband dual circularly polarized antenna unit has low structural complexity and high space utilization, and the two layers of feed lines are independently adjustable. Furthermore, the high circular polarization purity of the dual circularly polarized antenna helps to ensure the good state of signal quality, which is an effective guarantee for the overall performance and reliability of the antenna back-end system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is an exploded diagram of the unit structure of the dual circular polarization antenna unit in the present invention.

[0019] Figure 2 It is a schematic diagram of the planar structure of the second metal patch layer of the antenna array in the present invention.

[0020] Figure 3 It is a schematic diagram of the planar structure of the first metal patch layer of the antenna array in the present invention.

[0021] Figure 4 It is a schematic diagram of the planar structure of the first feeder layer of the antenna array in the present invention.

[0022] Figure 5 It is a schematic diagram of the planar structure of the second feeder layer of the antenna array in the present invention.

[0023] Figure 6 It is a curve diagram showing the S parameters and gain of the antenna unit in the present invention changing with frequency.

[0024] Figure 7 It is a curve diagram showing the axial ratio and radiation efficiency of the antenna unit in the present invention as a function of frequency.

[0025] Figure 8 It is a curve diagram showing the S parameters and gain of the antenna array in the present invention changing with frequency.

[0026] Fig. 9 It is a curve diagram showing the axial ratio and radiation efficiency of the antenna array in the present invention changing with frequency.

[0027] Fig.10 It is the normalized radiation pattern of the antenna array at 27 GHz when the left-hand circularly polarized radiation port is excited in the present invention.

[0028] Fig.11 It is the normalized radiation pattern of the antenna array at 27 GHz when the right-hand circularly polarized radiation port is excited in the present invention.

[0029] Fig.12 A graph showing the axial ratio of the left-hand circularly polarized antenna unit, subarray and array in the present invention as a function of frequency.

[0030] Fig.13 A graph showing the axial ratio of the right-hand circularly polarized antenna unit, subarray and array in the present invention as a function of frequency.

[0031] The meanings of the numbers in the figure are: first metal patch layer-1; second metal patch layer-2; metal gasket-3; first annular isolation belt-4; metal floor layer-5; second feeder layer-6; first dielectric layer-7; first bonding layer-8; second dielectric layer-9; second bonding layer-10; third dielectric layer-11; third bonding layer-12; fourth dielectric layer-13; first metallized via-14; first feeder layer-15; second metallized via-16; connector fixing hole-17; fourth metallized via-18; third metallized via-19; fourth T-junction power divider-20; third T-junction power divider-21; second T-junction power divider-22; first T-junction power divider-23; eighth T-junction power divider-24; seventh T-junction power divider-25; sixth T-junction power divider-26; fifth T-junction power divider-27; coplanar waveguide-28. DETAILED DESCRIPTION

[0032] The technical solution provided by the present invention will be further elaborated in detail below in conjunction with embodiments.

[0033] Terminology explanation: (1) Left-Hand Circularly Polarized (LHCP): This is a form of electromagnetic wave polarization. In this polarization state, when the right hand is clenched into a fist, the thumb points in the direction of wave propagation, and the direction of rotation of the electric vector is opposite to that of the four fingers.

[0034] (2) Right-Hand Circularly Polarized (RHCP): This is a form of electromagnetic wave polarization. In this polarization state, when the right hand is clenched into a fist, the thumb points in the direction of wave propagation, and the direction of rotation of the electric vector is the same as that of the four fingers.

[0035] (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 necessary to simultaneously meet the requirements that the reflection coefficient of the two ports is less than -10 dB and the port isolation is greater than 10 dB.

[0036] (4) Axial Ratio (AR): Indicates the uniformity of polarization characteristics in different directions. It is defined as the amplitude ratio between the two orthogonal electric field components (usually the horizontal component and the vertical component) of the antenna. Circularly polarized antennas usually need to meet the axial ratio of less than 3 dB.

[0037] (5) Circular polarization purity: It is an indicator 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.

[0038] (6) Multipath effect: It is the situation that a signal reaches the receiver through multiple paths during transmission. These paths may be caused by reflection, diffraction and scattering.

[0039] (7) Polarization mismatch: In a wireless communication system, the polarization state of the electromagnetic wave of the transmitting signal is inconsistent with the polarization state of the receiving antenna.

[0040] (8) Frequency reuse: It is a wireless communication technology that aims to improve the utilization of spectrum resources by transmitting multiple signals on the same or similar frequencies.

[0041] (9) Polarization diversity: This is a technology used in wireless communication systems that aims to improve signal transmission performance and anti-interference capabilities by utilizing the different polarization states of electromagnetic waves. This technology is particularly suitable for multipath propagation environments and can reduce problems caused by signal fading and interference.

[0042] (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 between phase and amplitude.

[0043] (11) Parasitic patches: In antenna design, parasitic patches can be additional elements in the antenna structure that do not directly provide power but affect the radiation characteristics of the main antenna through electromagnetic coupling. When the size, shape and position of these parasitic patches are properly configured with the main antenna, the antenna parameters such as gain, directivity or bandwidth can be improved.

[0044] (12) Sequential rotation technology: It is a unit arrangement scheme often used in circular polarization antenna array design. Sequential rotation technology requires that the antenna unit rotates a certain angle around its own geometric center. At the same time, the feeding phase and the rotation angle must satisfy a certain relationship, and the rotation angle and feeding phase distribution of each unit must be in sequence.

[0045] (13) Radiation pattern: The radiation pattern of an antenna refers to a curve graph showing how the relative field strength (normalized modulus) of the radiation field varies with direction at a certain distance from the antenna. It is usually represented by two mutually perpendicular plane patterns passing through the direction of maximum radiation of the antenna.

[0046] (14) Port isolation: refers to 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.

[0047] (15) Characteristic impedance: It is the ratio of voltage to current in a transmission line, which indicates the impedance characteristics of the transmission line to signals. Characteristic impedance is usually represented by the letter Z0, and its unit is ohm (Ω).

[0048] (16) Spurious radiation: Electromagnetic waves radiated by electronic devices or systems at unintended frequencies. 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.

[0049] (17) Degenerate mode: In antennas and other electromagnetic structures, it refers to different propagation modes (such as different electromagnetic wave modes) with the same frequency or the same characteristics.

[0050] (18) TM 10 Wave: A specific type of transverse electromagnetic wave in which a "1" indicates the presence of an electric field fluctuation in one direction and a "0" indicates the absence of a rapid change in the other direction (usually the width).

[0051] (19) Surface wave: 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 dielectric.

[0052] (20) Reflection coefficient S 11 : It is the ratio of incident wave power to reflected wave power. The unit is dB, and its size depends on the reflection condition reflected at the input port after the transmission system and the load work together. S 11 The smaller the value, the better the matching of the incident signal at the port, the less reflection, and the less energy loss.

[0053] (21) Gain: The ratio of the signal power density generated by an actual antenna and an ideal radiating unit at the same point in space under the same input power conditions. It quantifies the antenna's ability to radiate input power in a concentrated manner. The gain is closely related to the antenna's radiation pattern. The narrower the main lobe and the smaller the side lobe, the higher the gain.

[0054] (22) Radiation efficiency: It is the ratio of the antenna radiation power to the input power. It refers to the antenna's ability to effectively convert input power into radiation power and is usually expressed as a percentage.

[0055] (23) Half-power beamwidth: It is a physical quantity that measures the sharpness of the maximum radiation area of ​​an antenna. It is the width between the two half-power points of the main lobe of the radiation pattern. In the field intensity pattern, it is equal to the maximum field intensity. The width between two points.

[0056] (24) Sidelobe level: It is the level of the first sidelobe closest to the main lobe and with the highest level, generally expressed in dB. The sidelobe area of ​​the radiation pattern is the area where radiation is not required, so its level should be as low as possible.

[0057] (25) Cross-polarization level: It is the ratio of the power of the cross-polarization component (the polarization component perpendicular to the desired polarization direction) to the power of the main polarization component (i.e. the specified circular polarization direction, such as left-hand or right-hand). Similar to the cross-polarization level of a linearly polarized antenna, it is used to evaluate the polarization characteristics and interference of an antenna when sending or receiving signals.

[0058] like Figure 1 As shown, the unit structure of the dual circular polarization antenna unit provided by the present invention is a laminated structure, that is, each antenna unit is sequentially bonded from top to bottom with 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 circular polarization antenna unit includes a first metal patch layer 1 and a second metal patch layer 2. The first metal patch layer 1 is four parasitic patches, which are formed by diagonally cutting off four square patches. The second metal patch layer 2 is a main radiation patch, which is formed by diagonally cutting off a square patch. The main radiation patch and the parasitic patch have similar geometric shapes, but different sizes. Stacking patches expands the impedance bandwidth of the antenna, and diagonal cutting can achieve better circular polarization performance. The first feed line layer 15 is located between the second dielectric layer 9 and the second adhesive layer 10, and includes a vertically placed microstrip line. The second feed line layer 6 is located below the fourth dielectric layer 13, and includes a vertically placed microstrip line, which is connected to the main radiation patch layer (the second metal patch layer 2) through the second metallized via 16. When the excitation is located at different ports of the two feed line layers, the antenna will radiate electromagnetic waves of different polarizations.

[0059] like Figure 2As shown, it can be seen from the array design of the second metal patch layer 2 that the array design adopts sequential rotation technology. First, the antenna units are arranged into 2×2 subarrays on the same plate. Among them, the plate is equivalent to seamless splicing of multiple antenna units, so its stacked structure is consistent with the antenna unit. The center spacing between adjacent units is 0.7 times the wavelength, that is, 7.8mm. In order to meet the excitation phase and excitation amplitude of the four units, 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 units, that is, left-hand circular polarization radiation +90° and right-hand circular polarization radiation -90°. In order to further improve the gain, axial ratio bandwidth and circular polarization purity of the antenna, the four 2×2 subarrays are further combined into an array of 2×2 subarray level. A two-stage sequential rotation alignment is provided on the four subarrays. Rotating in the clockwise direction, the feeding phase between adjacent subarrays is successively -90° for left-hand circular polarization radiation and +90° for right-hand circular polarization radiation. The first-stage sequential rotation feeding network of the subarray is connected with the second-stage feeding network to form a second-order sequential rotation feeding network. The feeding network designed for this array can simplify the complexity, control the array area, increase the design flexibility and improve the port isolation.

[0060] Specifically, the antenna unit is fed in an orthogonal direction to realize circular polarization radiation of different rotation directions, that is, the second metal patch layer 2 is connected to the first feed line layer 15 by using the first metallized via 14, and the second metallized via 16 is used to connect the second metal patch layer 2 to the second feed line layer 6. The second metal patch layer 2 is connected to the first feed line layer 15 via the first metallized via 14 that passes through the first adhesive layer 8 and the second dielectric layer 9 in sequence; the second metal patch layer 2 is connected to the second feed line layer 6 via the second metallized via 16 that 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 in sequence; the two metallized vias are symmetrically arranged on the second metal patch layer 2, and the connecting line is parallel to the hypotenuse obtained by cutting off a pair of diagonals.

[0061] In order to electrically isolate the second metallized via 16 from the metal floor layer 5, an isolation ring is added with the center of the second metallized via 16 as the center of the circle, that is, a first annular isolation zone 4 is set around the second metallized via 16. At the same time, a metal gasket 3 with a radius smaller than the isolation ring is added with the center of the second metallized via 16 as the center of the circle. Adjusting the size of the isolation ring and the metal gasket 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 zone formed by cutting off part of the metal floor layer 5. The metal gasket 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 upper and lower interconnection of the second metallized via 16.

[0062] In the antenna unit, the antenna impedance bandwidth is expanded by stacking multiple metal patches. The main radiating patch and the parasitic patch were originally square patches, stacked up and down, with their centers on the same vertical line. In order to achieve circularly polarized radiation, the square main radiating patch with a side length of 2.78 mm was diagonally cut off, and the cut-off area was two isosceles right triangles with right-angle sides of 1.31 mm. By truncating the main radiating patch, the degenerate modes can be separated from each other and have a 90° phase difference, thereby satisfying the conditions for the generation of circular polarization. The planar structure of the first metal patch layer 1 is shown in FIG. Figure 3 As shown, in order to improve the gain flatness within the target frequency band, a cross slot with a width of 0.4mm is loaded on a square parasitic patch with a side length of 3.57mm. The cross slot separates the parasitic patch into four small metal patches of the same size. In order to improve the axial ratio bandwidth of the antenna, the four parts of the split parasitic patch are cut off diagonally in the same direction as the main radiation patch, and the cut-off part is an isosceles right triangle with a right angle side length of 0.7mm. Finally, it becomes the patch of the first metal patch layer 1 and the second metal patch layer 2.

[0063] Among them, the first dielectric layer 7, the second dielectric layer 9 and the fourth dielectric layer 13 are made of Rogers RO4350B sheet, with a relative dielectric constant of 3.66, a loss tangent of 0.0037, and the thickness of the three dielectric layers is 0.762mm, 0.254mm and 0.1mm respectively. The third dielectric layer 11 is made of Rogers RO3010 sheet, with a relative dielectric constant of 10.2, a loss tangent of 0.0022, and a thickness of 0.127mm. The first adhesive layer 8, the second adhesive layer 10 and the third adhesive layer 12 are made of Rogers RO4450F sheet, with a relative dielectric constant of 3.52, a loss tangent of 0.004, and a thickness of 0.1mm.

[0064] The array contains 16 circularly polarized radiating elements, which can be regarded as composed of 4 2×2 subarrays. In a single 2×2 subarray, the rotation angles of the 4 elements are 0°, 90°, 180° and 270° respectively. In the design of the feeding network of the 2×2 subarray, a progressive phase difference of ±90° is achieved between adjacent elements in the clockwise direction, that is, +90° for left-hand circular polarization radiation and -90° for right-hand circular polarization radiation, forming a one-stage sequential rotation feeding network. When forming a large array, the feeding phase delay between adjacent subarrays in the clockwise direction is -90° for left-hand circular polarization radiation and +90° for right-hand circular polarization radiation. The one-stage sequential rotation feeding network of the subarray is connected with the two-stage feeding network to form a second-order sequential rotation feeding network, thereby achieving wide axial ratio and high polarization purity performance.

[0065] In order to observe the feeding phase distribution of each unit more intuitively, Table 1 gives the ideal feeding phase value of each unit, that is, for left-hand circularly polarized radiation, the feeding phase of each unit is For right-hand circularly polarized radiation, the feeding phase of each unit is .

[0066] Table 1 Ideal value of feeding phase .

[0067] In the present invention, the antenna unit and the array feeder are distributed in different layers. This dual feeder layer design has the following advantages: 1. Compared with the traditional dual circular polarization feeding network, the structural complexity can be lowered, which simplifies the design. At the same time, the two layers of feeding with two different polarizations can be designed and adjusted independently, and the routing can be set more flexibly.

[0068] 2. Ensure that the antenna feed network can be constrained within the footprint of the array without adding any additional area, thus ensuring the compact design and high space utilization of the array.

[0069] 3. The two feed network layers are separated by a metal floor layer 5, which can achieve better isolation and improve the performance of the unit and the array.

[0070] Since there is no metal floor layer between the right-hand circular polarization radiation feed network and the second metal patch layer, the right-hand circular polarization radiation feed network will affect the radiation characteristics of the array. To reduce its influence, the third dielectric layer 11 uses Rogers RO3010 board, whose dielectric constant of up to 10.2 can well confine the guided waves propagated by the right-hand circular polarization radiation feed network in the substrate, with only weak stray radiation, which can be basically ignored.

[0071] The schematic diagram of the planar structure of the first feeder layer 15 of the right-hand circular polarization feeding network is as follows: Figure 4 As shown. It consists of a cascaded T-junction power splitter and a microstrip line. The signal enters the feed network from the third metallized via 19, and after passing through the fourth T-junction power splitter 20 and the third T-junction power splitter 21, the signal is divided into four paths and enters the subarray feed network. After the signal enters the subarray feed network, it passes through the second T-junction power splitter 22 and the first T-junction power splitter 23, and the signal is further divided into four paths, thereby forming a one-to-sixteen feed network.

[0072] Similarly, the planar structure diagram of the second feeder layer 6 of the left-hand circular polarization feeding network is as follows: Figure 5As shown. The signal enters the feeding network from the coplanar waveguide 28, and is divided into four paths after passing through the eighth T-junction power divider 24 and the seventh T-junction power divider 25, and enters the subarray feeding network, and is further divided into four paths after passing through the sixth T-junction power divider 26 and the fifth T-junction power divider 27. The input end of all T-junction power dividers of the feeding network is a microstrip line with a characteristic impedance of 35Ω and a quarter wavelength length, and the two arms are microstrip lines with a characteristic impedance of 50Ω. The 50Ω microstrip lines used in different stages are connected.

[0073] Among them, the third metallized via 19 is connected to the second feeder layer 6, and is connected to another coplanar waveguide (non-coplanar waveguide 28) through a microstrip line on the second feeder layer 6. Both coplanar waveguides are provided with a connector fixing hole 17 that runs through the entire board (i.e., penetrates the first metal patch layer to the second feeder layer) for fixing an external connector. Around the connector fixing hole 17, a plurality of fourth metallized vias 18 that run through the board are provided. The structure of the third metallized via 19 passing through the metal floor layer 5 is consistent with the structure of the second metallized via 16 passing through the metal floor layer 5.

[0074] There are two rows of fourth metallized vias 18 located between two connector fixing holes 17 and perpendicular to the line connecting the two. Figure 5 As shown, the microstrip line connecting the eighth T-junction power divider 24 extends between the two rows of fourth metallized vias 18 at the edge of the plate, and the extending portion, the two rows of fourth metallized vias 18, and two first external metal patches together form a coplanar waveguide 28. Among them, the first external metal patch is attached to the two rectangular areas formed by a plurality of fourth metallized vias 18 surrounding the connector fixing hole 17.

[0075] On the other side, the microstrip line connected to the third metallized vias 19 extends between the two rows of fourth metallized vias 18, and the extending portion, the two rows of fourth metallized vias 18, and the other two first external metal patches together form another coplanar waveguide for connecting the connector.

[0076] like Figure 3 As shown, two second external metal patches are also attached to the upper surface of the first dielectric layer 7 corresponding to the positions of the two pairs of connector fixing holes 17. Unlike a first external metal patch that only covers one connector fixing hole 17, a second external metal patch covers two connector fixing holes 17, that is, a second external metal patch is attached to the position corresponding to one coplanar waveguide on the upper surface of the first dielectric layer 7. It can be seen that in the same antenna array, a total of 6 external metal patches are provided to ensure that the connector has good grounding continuity when connected.

[0077] like Figure 6As shown in the figure, the S parameter and gain curve of the antenna unit vary with frequency. In the 20.2GHz~30.5GHz band, the reflection coefficient S of the left-hand circular polarization port and the right-hand circular polarization port 11 , S 22 The gain is lower than -10 dB. In the 23GHz~34GHz frequency band, the port isolation is greater than 10dB. The antenna unit has a wide impedance bandwidth. The gain at the center frequency of 27GHz is about 5.6dBic, and the gain response is flat on both sides of the center frequency.

[0078] like Figure 7 As shown in the figure, the curves of the axial ratio and radiation efficiency of the antenna unit vary with frequency. The 3dB axial ratio bandwidth of the left-hand circularly polarized beam of the antenna unit is 23% (23.7GHz~ 29.9GHz), and the 3dB axial ratio bandwidth of the right-hand circularly polarized beam is greater than 30.7% (>20GHz~ 28.3GHz), with good circular polarization performance and a wide axial ratio bandwidth. The difference in axial ratio bandwidth between the two ports is mainly caused by the different layer distribution of the feed line, which will be improved in the array. In the displayed frequency band, the radiation efficiency is greater than 95.6%.

[0079] like Figure 8 As shown in the figure, the S parameters and gain curves of the antenna array vary with frequency. In the 20GHz~32.9GHz band, the reflection coefficient S of the left-hand circular polarization port and the right-hand circular polarization port 11 , S 22 Both are lower than -10dB, and the port isolation is greater than 10dB. The peak gains of the left-hand circularly polarized beam and the right-hand circularly polarized beam are 17dBic and 16dBic respectively, and the 3dB gain bandwidth is 36.3% (20.7GHz~30.5GHz).

[0080] like Fig. 9 The curves of the axial ratio and radiation efficiency of the antenna array as a function of frequency are shown in Figure 2. Within the frequency band, the radiation efficiency of the left-hand circularly polarized and right-hand circularly polarized beams is 67% on average. The 3 dB axial ratio bandwidth of the left-hand circularly polarized beam is greater than 51.9% (>20GHz ~ 34GHz), and the 3dB axial ratio bandwidth of the right-hand circularly polarized beam is greater than 49.6% (20.6GHz ~ 34GHz).

[0081] like Fig.10 Figure 2 shows the normalized radiation pattern of the antenna array at 27 GHz when the left-hand circularly polarized radiation port is excited. The half-power beamwidth is about 17.6°, the peak sidelobe level is less than -10 dB, and the axial cross-polarization level is less than -25 dB.

[0082] like Fig.11As shown in the figure, the normalized radiation pattern of the antenna array at 27 GHz when the right-hand circularly polarized radiation port is excited. Approximately, the half-power beamwidth is about 18°, the peak sidelobe level is less than -10 dB, and the axial cross-polarization level is less than -25 dB. The radiation of the two directions has similar excellent performance. At the same time, the high similarity between the results of left-hand circular polarization and right-hand circular polarization also shows that the stray radiation of the right-hand circularly polarized feeding network has little effect on the radiation characteristics of the array.

[0083] like Fig.12 As shown in Figure 1, the axial ratio of the left-hand circularly polarized antenna unit, subarray and array varies with frequency. Fig.13 As shown in Figure 1, the axial ratio of the right-hand circularly polarized antenna unit, subarray and array varies with frequency. When expanded to an array, the axial ratio bandwidth and circular polarization purity are further improved.

[0084] The technical solution provided by the present invention has the following advantages: 1. Simple unit design: The antenna unit adopts a stacked patch design, which increases the impedance bandwidth by adding a parasitic patch above the main radiating patch. At the same time, the main radiating patch and the parasitic patch are similarly cut off diagonally to achieve a wider axial ratio bandwidth. In addition, two metallized vias are used for direct feeding in orthogonal directions.

[0085] 2. Divide the two polarization feeding networks to the upper and lower sides of the metal ground plane: The present invention reduces the complexity of the antenna array, constrains the footprint of the feeding network, obtains good isolation and increases the flexibility of the design. At the same time, in order 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 the two.

[0086] 3. Design arrays with second-order sequential rotation feeding: To improve the axial ratio bandwidth, many array designs use sequential rotation feeding networks. However, most are only single circularly polarized antenna arrays. Moreover, when a 2×2 array is expanded to 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 circularly polarized antenna unit into a 2×2 subarray. When expanded to 4×4 (for antenna units), the four subarrays are then allocated in a 90° sequential rotation, providing a second stage of sequential rotation alignment at the subarray level. Further improve the broadband performance and polarization purity of dual circularly polarized radiation.

[0087] In summary, the broadband dual circularly polarized antenna unit provided by the present invention has a simple structure, a wide impedance bandwidth and an axial ratio bandwidth. In addition, the array constructed based on the broadband dual circularly polarized antenna unit has not only a wide impedance bandwidth and an axial ratio bandwidth, but also a high design flexibility, space utilization and circular polarization purity, and has good dual circular polarization performance. Furthermore, the high circular polarization purity of the dual circularly polarized antenna array helps to ensure a good state of signal quality, which is an effective guarantee for the overall performance and reliability of the antenna system.

[0088] Furthermore, on the basis of achieving the above-mentioned beneficial effects, each preferred scheme has also achieved the following beneficial effects: the specific size and material setting of the antenna unit can ensure the purity of circular polarization; the setting of the dual 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°; 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).

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