A broadband dual-circularly polarized phased array antenna loaded with hybrid decoupling structure

Abstract

This invention discloses a broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure, relating to the field of antenna technology. The antenna includes a first metal layer comprising a star-shaped metal strip and four pairs of concave metal strips. The first metal layer is disposed on the upper surface of a top dielectric substrate, and a second metal layer is disposed on the lower surface of the top dielectric substrate. The star-shaped metal strips are connected to the second metal layer via grounded metal pillars. A third metal layer is disposed on the upper surface of a bottom dielectric substrate, and a metal base plate is disposed on the lower surface of the bottom dielectric substrate. The second metal layer and the metal base plate are connected via insulating metal pillars that pass through an intermediate prepreg adhesive sheet and the bottom dielectric substrate. The third metal layer and the metal base plate are connected via metal probes. The third metal layer and the second metal layer are bonded together via the intermediate prepreg adhesive sheet. This invention provides a high-performance, low-cost, and easily integrated decoupling solution.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and in particular to a broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure. Background Technology

[0002] Millimeter-wave broadband dual-circularly polarized phased array antennas are core components of modern vehicle-mounted satellite communications and high-precision radar systems. They are widely used in high-end electronic devices due to their combination of broadband transmission, dual-polarization anti-interference capabilities, and flexible beam scanning. However, the inherent short wavelength of the millimeter-wave band, coupled with the compact arrangement of array elements at intervals less than half a wavelength, significantly enhances electromagnetic coupling between elements, severely limiting the overall antenna performance. Although various decoupling schemes exist to suppress mutual coupling, most struggle to balance broadband coverage and dual-polarization adaptability, or require sacrificing the antenna's low-profile characteristics, increasing manufacturing costs and integration complexity. Therefore, seeking a low-cost, low-profile decoupling design method that adapts to broadband dual-polarization requirements is particularly important.

[0003] The main drawbacks of existing decoupling schemes are as follows:

[0004] First, the adaptability of dual circular polarization is insufficient: Most existing decoupling schemes are mainly designed for linear polarization or single circular polarization. While some linear polarization decoupling schemes can suppress coupling between array elements, they affect the circular polarization performance of the elements. Furthermore, some single circular polarization decoupling schemes cannot achieve consistent decoupling effects for both polarizations simultaneously. This design limitation prevents the schemes from completely blocking electromagnetic coupling interference between dual circular polarization array elements, leading to problems such as insufficient reduction in inter-element isolation (unit: dB) and axial ratio distortion. This severely affects the polarization purity and anti-interference capability of the antenna, limiting its application in dual circular polarization communication and detection systems.

[0005] Second, the lack of broadband adaptability: Most existing decoupling solutions can only achieve effective coupling suppression in a narrow band, which cannot meet the application requirements of millimeter-wave systems for wide bandwidth (relative bandwidth ≥10%). This limitation leads to a sharp decline in the coupling suppression effect in the broadband range, which not only reduces power transmission efficiency but also affects the stability of the antenna when operating in the broadband band, thus restricting its adaptability in modern broadband communication and radar systems.

[0006] Third, the antennas are structurally complex and have increased profile: Most existing decoupling solutions rely on loading metasurfaces, vertical structures, or complex feeding networks, which not only increases the structural complexity and manufacturing cost of the antenna but also leads to an increased antenna profile. This problem makes the antennas difficult to adapt to space-constrained applications such as vehicle-mounted and airborne applications, while also increasing assembly difficulty and subsequent maintenance costs.

[0007] Fourth, insufficient adaptability of phased arrays: Most existing decoupling schemes are only designed for ordinary array antennas and do not consider the scanning phase difference and active impedance variation characteristics of phased array antennas at wide scanning angles. This design flaw makes it impossible for the scheme to stabilize the active input impedance of the phased array elements. During wide scanning, the active VSWR is prone to deterioration, leading to problems such as damage to active devices by backfeed power, beam pointing deviation, and gain reduction. It cannot meet the core requirement of flexible beam scanning of phased array antennas.

[0008] Therefore, a broadband dual-circularly polarized phased array antenna with a hybrid decoupling structure was developed to solve the above problems. Summary of the Invention

[0009] This invention proposes a broadband dual-circular polarization phased array antenna with a loaded hybrid decoupling structure to solve the problems of insufficient dual-circular polarization adaptability, lack of broadband adaptability, complex structure and increased profile, and insufficient phased array adaptability of existing antennas.

[0010] The present invention achieves the above objectives through the following technical solutions:

[0011] This invention discloses a broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure, comprising a first metal layer, a top dielectric substrate, a second metal layer, an intermediate prepreg adhesive sheet, a third metal layer, a bottom dielectric substrate, and a metal base plate, wherein:

[0012] The first metal layer includes a star-shaped metal strip and four pairs of concave metal strips. Each pair of concave metal strips includes two parallel and symmetrical concave metal strips. The four pairs of concave metal strips are located above, below, left, and right of the star-shaped metal strip, respectively, with their concave surfaces facing the star-shaped metal strip.

[0013] The first metal layer is disposed on the upper surface of the top dielectric substrate, and the second metal layer is disposed on the lower surface of the top dielectric substrate. The cross-shaped metal strip is connected to the second metal layer by a grounding metal post, which passes through the top dielectric substrate.

[0014] The third metal layer is disposed on the upper surface of the bottom dielectric substrate, and the metal base plate is disposed on the lower surface of the bottom dielectric substrate. The second metal layer and the metal base plate are connected by an isolation metal pillar, which passes through the intermediate layer prepreg adhesive sheet and the bottom dielectric substrate. The third metal layer and the metal base plate are connected by a metal probe, which passes through the bottom dielectric substrate.

[0015] The third metal layer is bonded to the second metal layer by an intermediate prepreg adhesive sheet.

[0016] Furthermore, the first metal layer also includes four metal patches, which are formed by stacking cross-shaped and square metal patches. A square groove is etched in the center of each metal patch. The four metal patches are symmetrically arranged about the central axis of the first metal layer. Each pair of U-shaped metal strips is located between two metal patches, and the star-shaped metal strip is located at the center surrounded by the four metal patches.

[0017] Furthermore, four slots are etched on the second metal layer. The top, bottom, left, and right ends of the cross-shaped metal strip are connected to the second metal layer through grounding metal posts. The center of the four slots corresponds one-to-one with the center of the four metal patches. The four slots are symmetrically distributed with the central axis of the second metal layer as the reference.

[0018] Furthermore, the slot is a star-shaped slot with missing corners.

[0019] Furthermore, the notched star-shaped slot includes eight slot arms, with the lower right slot arm being the shortest. The other slot arms are symmetrical in pairs and have the same length. The lower left and upper right slot arms are longer than the other slot arms.

[0020] Furthermore, the third metal layer includes four Ω-shaped feed lines and eight disks. The four Ω-shaped feed lines are symmetrical about the central axis. Each Ω-shaped feed line is connected to a disk at both ends. Two isolation metal pillars are provided between the two disks of each Ω-shaped feed line. The two isolation metal pillars are arranged diagonally. Each metal disk is connected to a metal probe.

[0021] Furthermore, eight circular holes are etched on the metal base plate, and the center point of each hole corresponds one-to-one with the center point of the metal probe and the center point of the disk. The end of the metal probe that passes through the metal base plate is connected to a power supply port.

[0022] Furthermore, the Ω-shaped feeder includes two bent narrow feeders and one bent wide feeder. The two bent narrow feeders are arranged symmetrically, and the two bent narrow feeders and one bent wide feeder are all chamfered at the bends.

[0023] Furthermore, the second metal layer is connected to the metal base plate by metal pillars, with 32 metal pillars forming a square that surrounds each Ω-shaped feeder, for a total of 128 metal pillars.

[0024] Furthermore, both the top and bottom dielectric substrates are made of RO4350B material, and the intermediate prepreg adhesive sheet is made of RO4450F material.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention proposes a broadband dual-circular polarization phased array antenna with a hybrid decoupling structure. This antenna can adapt to the dual-circular polarization operating characteristics under broadband operating conditions, improve the isolation between array elements, ensure polarization purity and anti-interference capability, and effectively improve the active VSWR and axial ratio during array scanning. At the same time, it maintains low profile characteristics, is compatible with conventional manufacturing processes, and reduces structural complexity and manufacturing costs. Ultimately, it provides a high-performance, low-cost, and easily integrated decoupling solution for millimeter-wave broadband dual-circular polarization phased array antennas. Attached Figure Description

[0027] Figure 1 This is a cross-sectional schematic diagram of a broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure according to this application;

[0028] Figure 2 This is an exploded view of the structure of a broadband dual-circularly polarized phased array antenna with a hybrid decoupling structure according to this application.

[0029] Figure 3 This is a top view of the first metal layer of a broadband dual-circularly polarized phased array antenna with a hybrid decoupling structure according to this application;

[0030] Figure 4 This is a top view of the second metal layer of a broadband dual-circularly polarized phased array antenna with a hybrid decoupling structure according to this application;

[0031] Figure 5 This is a top view of the third metal layer of a broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure according to this application;

[0032] Figure 6 This is a top view of the metal substrate of a broadband dual-circularly polarized phased array antenna with a hybrid decoupling structure according to this application;

[0033] Figure 7 This is a graph showing the S-parameters of the broadband dual-circularly polarized phased array antenna element of this application as a function of frequency.

[0034] Figure 8 This is a graph showing the axial ratio of the broadband dual-circularly polarized phased array antenna element of this application as a function of frequency.

[0035] Figure 9 The active VSWR curve of the phased array antenna when not scanning is shown when the hybrid decoupling structure is loaded for this application.

[0036] Figure 10 This is a curve showing the isolation between adjacent elements of the phased array antenna when only the open-circuit concave decoupling structure is loaded in this application;

[0037] Figure 11 This is a graph showing the isolation between adjacent elements of the phased array antenna when only the star-shaped decoupling structure is loaded in this application.

[0038] Figure 12 The diagram shows the isolation curve between adjacent elements of the phased array antenna when the hybrid decoupling structure is loaded in this application.

[0039] Figure 13 The radiation pattern of the phased array antenna when it is scanned to -40° at 25 GHz when the hybrid decoupling structure is loaded for this application;

[0040] Figure 14 A graph showing the axial ratio of the phased array antenna when it scans to -40° at 25 GHz with the hybrid decoupling structure applied in this application.

[0041] Figure 15 The active VSWR curve of the phased array antenna when scanning to -40° is shown when the hybrid decoupling structure is loaded in this application.

[0042] Figure 16 This is a surface current distribution diagram of the first metal layer 1 when only element 1 of the phased array antenna is excited, based on the hybrid decoupling structure applied in this application. Figure 16 In the diagram, (a) shows the surface current distribution of the antenna at phase t=0, (b) shows the surface current distribution of the antenna at phase t=3×T / 4, (c) shows the surface current distribution of the antenna at phase t=T / 4, and (d) shows the surface current distribution of the antenna at phase t=2×T / 4.

[0043] In the diagram: First metal layer - 1; Metal patch - 101; Square groove - 102; U-shaped metal strip - 103; Star-shaped metal strip - 104; Top dielectric substrate - 2; Second metal layer - 3; Corner-cut star-shaped slot - 301; Intermediate layer prepreg adhesive sheet - 4; Third metal layer - 5; Ω-shaped feed line - 501; Disk - 502; Bent narrow feed line - 503; Bent wide feed line - 504; Bottom dielectric substrate - 6; Metal base plate - 7; Circular hole - 701; Grounding metal post - 8; Isolation metal post - 9; Metal post - 10; Metal probe - 11. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0045] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0046] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0047] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0048] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0049] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0050] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0051] like Figure 1 As shown, a broadband dual-circularly polarized phased array antenna with a hybrid decoupling structure includes: a first metal layer 1, a top dielectric substrate 2, a second metal layer 3, an intermediate prepreg adhesive sheet 4, a third metal layer 5, a bottom dielectric substrate 6, a metal base plate 7, four grounding metal pillars 8, eight isolation metal pillars 9, one hundred and twenty-eight metal pillars 10, and eight metal probes 11.

[0052] The first metal layer 1 is located on the upper surface of the top dielectric substrate 2, the second metal layer 3 is located on the lower surface of the top dielectric substrate 2, the third metal layer 5 is located on the upper surface of the bottom dielectric substrate 6, and the metal base plate 7 is located on the lower surface of the bottom dielectric substrate 6. The top dielectric substrate 2 and the bottom dielectric substrate 6 are bonded together by the intermediate layer prepreg adhesive sheet 4.

[0053] In this embodiment, the top dielectric substrate 2 and the bottom dielectric substrate 6 are made of RO4350B material. The thickness of the top dielectric substrate 2 is 0.09λ0 (λ0 is the free space wavelength at 27GHz), the thickness of the bottom dielectric substrate 6 is 0.02λ0, the middle layer prepreg adhesive sheet 4 is made of RO4450F material, the thickness is 0.018λ0, the overall antenna size is 0.9λ0×0.9λ0, and the cross-sectional height is 0.14λ0.

[0054] like Figure 2 As shown, the upper surface of the top dielectric substrate 2 includes four cross-shaped and square-shaped metal patches 101 with etched square grooves 102, a star-shaped metal strip 104, and four pairs of U-shaped metal strips 103. The cross-shaped and square-shaped metal patches 101 are formed by stacking cross-shaped and square metal patches to create a shape extending outwards from the center of the four edges of the square structure, thereby extending the current path and reducing the size of the metal patches 101. Furthermore, square grooves 102 are etched at the center of the cross-shaped and square-shaped metal patches 101 to broaden the impedance bandwidth. The four cross-shaped and square-shaped metal patches 101 with etched square grooves 102 are symmetrical about the central axis, with a center-to-center spacing of 0.41λ0 between adjacent patches. The star-shaped metal strip 104 can be seen as a combination of a cross-shaped metal strip and a diagonal cross-shaped metal strip rotated 45° around the center of the cross-shaped metal strip. The cross-shaped metal strip and the diagonal cross-shaped metal strip rotated 45° are the same size. The eight arms of the star-shaped metal strip 104 are of the same length, approximately 0.14λ0 in length and approximately 0.027λ0 in width, and are located at the center of the four metal patches 101 with cross-shaped and square grooves 102 etched on them. The concave metal strip 103 can be seen as a pair of double parallel rectangular metal strips, with a small rectangular strip cut out on the symmetrical plane of each of the two parallel rectangular metal strips to form a groove. This groove is used to reduce the length and adjust its own impedance characteristics, so that the coupled energy is reflected and absorbed within the structure. The rectangular strip has a length of approximately 0.14λ0 and a width of approximately 0.018λ0. The groove has a length of approximately 0.099λ0 and a width of approximately 0.005λ0. The four pairs of U-shaped metal strips 103 are located in the middle of the cross-shaped and square metal patches 101 that are etched with square grooves 102, and are perpendicular to the cross axis of the top dielectric substrate 2.

[0055] like Figure 4 As shown, the second metal layer 3 is etched with four symmetrical, notched, star-shaped slots 301 about the central axis. These notched star-shaped slots 301 are aligned with the center points of the four metal patches 101 with square slots 102 etched in a cross shape and a square shape. The notched star-shaped slot 301 can be decomposed into eight slot arms. The lengths of adjacent slot arms are inconsistent, and the included angle is 45°. Except for one pair of slot arms with an included angle of 180° that are parallel to the upper left to lower right diagonal of the second metal layer 3, the lengths of the other two slot arms with an included angle of 180° are the same. The lengths of the two left and right slot arms are approximately 0.117λ0, the lengths of the two top and bottom slot arms are approximately 0.114λ0, the lengths of the two slot arms parallel to the upper right to lower left diagonal of the second metal layer 3 are approximately 0.123λ0, and the lengths of the two slot arms parallel to the upper left to lower right diagonal of the second metal layer 3 are 0.148λ0 and 0.106λ0, respectively. The width of all eight slot arms is 0.018λ0.

[0056] like Figure 5 As shown, the upper surface of the bottom dielectric substrate 6 has four Ω-shaped feed lines 501, each with two disks 502, arranged symmetrically about the central axis. The two disks 502, two bent narrow feed lines 503, and one bent wide feed line 504 together constitute the Ω-shaped feed line 501. This Ω-shaped feed line 501 is a stripline, which has a smaller size than a microstrip line and provides better electromagnetic shielding. The Ω-shaped feeder 501 has two disks 502 connected to its two ends. Starting from one of the disks 502, it passes through a first bent narrow feeder 503 with a width of approximately 0.02λ0 and a characteristic impedance of approximately 50Ω, matching the 50Ω impedance of the feed port. Then it passes through a bent wide feeder 504 with a width of approximately 0.06λ0. Since the impedance on both sides of the notched star-shaped slot 301 is lower than that at the center, the bent wide feeder 504 is widened to reduce the impedance, thereby improving the impedance matching between the bent wide feeder 504 and the sides of the notched star-shaped slot 301. Then it passes through a second bent narrow feeder 503 that is completely symmetrical to the first bent narrow feeder 503. Both of these are called bent narrow feeders 503. Finally, it ends at the other disk 502. Both bent narrow feeders 503 and one bent wide feeder 504 have chamfered corners at the bends to smooth the impedance.

[0057] like Figure 6 As shown, the metal base plate 7 is the ground plane of the entire antenna, and eight circular holes 701 are etched on it, which are aligned with the center points of the eight disks 502 on the four Ω-shaped feed lines 501. These eight circular holes 701 are mainly to avoid radio frequency signals to prevent short circuits.

[0058] The top, bottom, left, and right ends of the star-shaped metal strip 104 are connected to the second metal layer 3 via grounding metal posts 8. These grounding metal posts 8 pass through the top dielectric substrate 2. The four metal arms connected to the grounding metal posts 8 can be called short-circuit arms, while the other four metal arms not connected to the grounding metal posts 8 can be called diagonally open-circuit arms. Eight isolating metal posts 9 connect the second metal layer 3 and the metal base plate 7, arranged in pairs along a diagonal pattern, placed between the two disks 502 of the Ω-shaped feeder 501. This reduces electromagnetic interference between the two metal probes 11 and improves polarization purity. One hundred and twenty-eight metal posts 10 are used to connect the second... Metal layer 3 and metal base plate 7 are grounded together. Thirty-two metal pillars 10 are used in each unit to form a square, with eight metal pillars 10 on each side. In order to minimize the spacing between array elements, the side length of the square is only 0.31λ0. While ensuring the processing technology, the spacing between adjacent metal pillars 10 is minimized as much as possible, thus being equivalent to a metal cavity to reduce electromagnetic coupling between the four units. Eight metal probes 11 pass through the metal base plate 7 and the bottom dielectric substrate 6, connecting the feed port and eight disks 502 on the four Ω-shaped feed lines 501 for the transmission of radio frequency signals.

[0059] Based on this antenna element, a 2×2 phased array antenna is formed, and a hybrid decoupling structure is loaded on its first metal layer 1. The upper, lower, left, and right ends of its star-shaped metal strip 104 are connected to the second metal layer 3 through grounding metal posts 8, respectively. The eight metal arms of the star-shaped metal strip 104 are divided into short-circuit arms and oblique open-circuit arms. The star-shaped metal strip 104 connected to the grounding metal posts 8 can be called a star-shaped decoupling structure, which can reduce the mutual coupling between antenna elements. The concave metal strip 103 can be called an open-circuit concave decoupling structure. The combination of the two decoupling structures with different operating characteristics of open circuit and short circuit is a hybrid decoupling structure.

[0060] like Figure 3 and Figure 5As shown, this antenna is a 2×2 phased array antenna with an element spacing of 0.41λ0. It has eight feed ports, Port1 to Port8, referred to as Port 1 to Port 8. When Port1, Port4, Port6, and Port8 are excited, Port2, Port3, Port5, and Port7 are connected to matched loads, and the antenna radiates with left-hand circular polarization; conversely, the antenna radiates with right-hand circular polarization. Specifically, when one of the feed ports of the antenna element is excited, energy is fed clockwise or counterclockwise along the metal probe 11 to the Ω-shaped feed line 501. At this time, the energy on the Ω-shaped feed line 501 is in a traveling wave state. Furthermore, most of the energy on the Ω-shaped feed line 501 is coupled to the notched star-shaped slot 301, while the metal patch 101, which combines a cross shape and a square shape and has a square slot 102 etched on it, is excited by the notched star-shaped slot 301. By exciting different feed ports, left-hand and right-hand circular polarization characteristics are achieved.

[0061] The working principle of this technical solution is as follows:

[0062] 1. Working principle of a dual-circularly polarized phased array antenna element that achieves wide bandwidth and wide axial ratio:

[0063] (1) First, for any antenna, circular polarization radiation needs to satisfy "equal amplitude orthogonal electric field and 90° phase difference", while dual circular polarization radiation needs to be able to switch the phase difference to "90° or -90°" at any time.

[0064] (2) This invention utilizes an Ω-shaped feeder 501 as the feeding structure. When the radio frequency signal propagates through the Ω-shaped feeder 501, the continuous accumulation of phase is achieved by utilizing the traveling wave characteristics. In the design, by optimizing the width and transmission path length of the two bent narrow feeders 503 and one bent wide feeder 504 in the Ω-shaped feeder 501, as well as the length and width of the eight slot arms of the corner-cut cross-shaped slot 301, the excitation phase difference of adjacent slot arms is precisely controlled to 45° when the radio frequency signal passes through the corner-cut cross-shaped slot 301 in sequence. Every three adjacent slot arms accumulate to form a 90° phase gradient, laying the foundation for the synthesis of orthogonal electric fields with equal amplitude and 90° phase difference. Two metal probes 11 are connected to two disks 502 on the Ω-shaped feed line 501, and a power supply port is connected to one end of the two metal probes 11 that passes through the metal base plate 7. By exciting different power supply ports, the radio frequency signal will propagate clockwise or counterclockwise on the Ω-shaped feed line 501 and couple the energy to the eight slot arms of the notched star-shaped slot 301, thereby forming a 90° or -90° phase difference to achieve left-hand circular polarization or right-hand circular polarization. Furthermore, the slot arm at the lower right of the notched star-shaped slot 301 is only 0.106λ0. This is because the radiation intensity of the RF signal is very weak when it passes through the lower right slot arm as it propagates on the Ω-shaped feed line 501. Therefore, the length of this slot arm is shortened to form the notched star-shaped slot 301. Along the diagonal of this slot arm, two insulating metal pillars 9 are placed between the two disks 502 of the Ω-shaped feed line 501 to reduce electromagnetic coupling of the RF signal as it propagates through the two metal probes 11, thereby improving port isolation and axial ratio performance. Further, the radiating structure uses a cross-shaped and square-shaped metal patch 101 with etched square slots 102. By extending the current path on the patch edge surface, the patch size is reduced to only 0.16λ0. The cross-shaped and square metal patch 101 serves as a radiation enhancement layer, receiving and efficiently radiating the energy coupled from the notched star-shaped slot 301. Simultaneously, a square slot 102 is etched at the center of the cross-shaped and square metal patch 101 to improve impedance matching over a wide bandwidth, ultimately achieving an impedance bandwidth of 26.9% (23.99GHz-31.46GHz) and an axial ratio bandwidth of 63.3% (16.14GHz-31.11GHz).

[0065] 2. Decoupling working principle of a broadband dual-circularly polarized phased array antenna with a hybrid decoupling structure:

[0066] (1) In this invention, the hybrid decoupling structure is divided into a star-shaped decoupling structure and an open-circuit concave-shaped decoupling structure, and the two decoupling structures work together. When the open-circuit concave-shaped decoupling structure is loaded only between adjacent units, the structure and size parameters of the concave-shaped metal strip 103 are optimized to control its own impedance characteristics, guide the coupling energy to change the propagation direction, and generate reflection and absorption at the open end, thereby reducing the coupling energy to the adjacent array elements and having less interference with the antenna radiation characteristics; when the star-shaped decoupling structure is loaded only at the center of the four antenna units, the incident coupling field of the radiating unit excites induced current on each metal arm, and forms a stable standing wave after reflection at the terminal boundary. Since the length of each metal arm is designed to be about one-quarter of the dielectric wavelength at the corresponding center frequency, based on the round-trip phase delay characteristics of the one-quarter wavelength transmission line, the secondary radiation field generated therein and the original incident coupling field achieve coherent cancellation at adjacent and diagonal units, thereby suppressing mutual coupling between units, improving the wide-angle scanning axis ratio and active standing wave characteristics, and alleviating gain drop. Furthermore, the incident coupling field of the radiating unit is characterized as E k C The secondary radiation field generated by the decoupling structure is represented by E. k D This can be characterized by the fact that the incident coupled field and the secondary radiation field can cancel each other out when the following conditions are met:

[0067] (1)

[0068] (2)

[0069] (3)

[0070] (4)

[0071] in, Let A represent the incident coupling field generated by the excitation element at the k-th passive element, where A is the excitation amplitude of the excitation element. The coupling coefficient between antenna elements is a complex number that can be divided into amplitude coefficients. and phase That is, equation (1), where is a complex phase factor, where j is the imaginary unit commonly used in engineering. It is based on Euler's formula to represent a unit complex number with a constant magnitude of 1. Its sole function is to carry all phase information generated during the electromagnetic coupling process between antenna elements without changing the signal amplitude. This is represented as the secondary radiation field generated by the excitation element at the k-th passive element. The coupling coefficient between the antenna element and the decoupling structure is a complex number that can be divided into amplitude... and phase That is, equation (2), where For complex phase factor, j is the imaginary unit commonly used in engineering, which is based on Euler's formula to represent a unit complex number with a constant magnitude of 1. Similarly, without changing the signal amplitude, it carries all the phase information generated during the electromagnetic coupling process between the antenna element and the decoupling structure. When the coupling coefficient between the antenna elements and the coupling coefficient between the antenna element and the decoupling structure are opposites, that is, when the amplitude satisfies equation (3) and amplitude Equal phase, and satisfying equation (4) and phase difference That is, at 180°, the incident coupling field of the radiating unit and the secondary radiation field of the decoupled structure are superimposed on each other. Since they are opposite numbers, they will cancel each other out, which satisfies the current superposition effect of "equal amplitude and opposite phase", thereby canceling the coupling and achieving the decoupling effect.

[0072] The technical effects of this invention will be explained in detail below with reference to simulation results:

[0073] Figure 7 The curves showing the S-parameters of the antenna element as a function of frequency are displayed. The dashed line represents the -10dB reference threshold for the S-parameters; the frequency range below this line represents the operating frequency band of the antenna element. S11 is the reflection coefficient of port 1, S22 is the reflection coefficient of port 2, both in dB, and S12 is the reverse transmission coefficient from port 2 to port 1 (S12=S21 in a reciprocal network), representing the isolation between the two ports. Since this antenna uses traveling-wave feeding, its characteristic is that the radio frequency signal propagates through the Ω-shaped feed line 501, sequentially exciting the notched star-shaped slot 301, radiating electromagnetic waves. The energy gradually weakens until it is completely absorbed by the other feed port. Therefore, S12 below -10dB indicates the frequency band in which the antenna can operate, and how much energy is coupled out through the Ω-shaped feed line 501. S11 or S22 only indicates that there is no reflection at the feed port within this frequency band. Therefore, the -10dB impedance bandwidth of this antenna element is 26.9% (23.99-31.46GHz), achieving a relatively wide impedance bandwidth.

[0074] Figure 8 The curves showing the axial ratio of the antenna element as a function of frequency are displayed. The dashed line represents the 3dB reference threshold of the axial ratio, and below this dashed line is the 3dB axial ratio bandwidth of the antenna element, which is 63.3% (16.14GHz-31.11GHz).

[0075] Figure 9This paper presents a comparison of the active VSWR (active standing wave ratio) of a dual circularly polarized phased array antenna without and with a hybrid decoupling structure, before scanning. The dashed line represents a reference threshold of 2 for the active VSWR. Both the unloaded and loaded dual circularly polarized phased array antennas operate below this dashed line, exhibiting good performance. Due to the antenna's symmetry and reciprocity, only the active VSWR for excitation ports 2, 3, 5, and 7 are shown. It is evident that loading the hybrid decoupling structure slightly improves the active VSWR, achieving an active VSWR less than 1.5 across the entire operating frequency band (23.99–30 GHz) compared to the unloaded phased array antenna, demonstrating better performance.

[0076] Figure 10 This demonstrates the isolation between adjacent elements of a phased array antenna when only the U-shaped decoupling structure is applied. (S32 represents the isolation between two adjacent antenna elements of excitation Port2 and excitation Port3). Within the operating frequency band, before decoupling, the isolation between adjacent elements is within 15dB to 20dB. After decoupling, the isolation between adjacent elements reaches around 25dB in the high-frequency band (27-31GHz), with the isolation decreasing by at least 5dB. However, the decoupling effect is weaker in the low-frequency band (24-27GHz), decreasing by only about 2dB.

[0077] Figure 11 This demonstrates the isolation between adjacent elements of a phased array antenna when only a star-shaped decoupling structure is applied. Within the operating frequency band, before decoupling, the isolation between adjacent elements was within 15dB to 20dB; after decoupling, the isolation between adjacent elements reached over 22dB across the entire operating frequency band, representing a minimum reduction of 5dB in isolation. Compared to applying only a U-shaped decoupling structure, applying only a star-shaped decoupling structure provides a wider effective decoupling frequency band.

[0078] Figure 12 The simulation demonstrates the isolation between adjacent elements of a phased array antenna when a hybrid decoupling structure is applied. Within the operating frequency band, before decoupling, the isolation between adjacent elements was between 15dB and 20dB. After decoupling, the isolation between adjacent elements reached over 25dB across the entire operating frequency band, with a minimum reduction of 7dB and a maximum reduction of 25dB. The simulation results further indicate that the synergistic effect of the star-shaped and concave-shaped decoupling structures provides two coupling paths for the coupling energy between array elements: one for the concave-shaped structure and the other for the star-shaped structure. Compared to applying only the star-shaped decoupling structure, the isolation across the entire operating frequency band is further reduced, with a significant effect at high frequencies, averaging a reduction of 20dB. This is mainly because the metal arms of the star-shaped decoupling structure are closer to a quarter of the dielectric wavelength at high frequencies, resulting in better decoupling at high frequencies and offsetting more coupling energy.

[0079] Figure 13The radiation pattern of the proposed dual-circularly polarized phased array antenna when scanning to -40° at 25 GHz is shown. Here, RHCP represents right-hand circular polarization, and LHCP represents left-hand circular polarization. When Port2, Port3, Port5, and Port7 are excited, the main polarization is right-hand circular polarization, and the cross-polarization is left-hand circular polarization. It can be seen that loading the hybrid decoupling structure has little effect on the normal radiation pattern. However, when the phased array antenna is scanning, the cross-polarization when the hybrid decoupling structure is loaded at the maximum angle of -40° is lower than the cross-polarization without the hybrid decoupling structure, decreasing from approximately -10 dB to -18 dB.

[0080] Figure 14 The axial ratio of the proposed dual-circularly polarized phased array antenna when scanned to -40° at 25 GHz is shown. It can be seen that loading the hybrid decoupling structure can effectively improve the axial ratio performance of the antenna after scanning, from 2.4 dB to 0.9 dB.

[0081] Figure 15 The diagram shows a comparison of the active VSWR of the proposed dual-circularly polarized phased array antenna when scanning to -40°. The dashed line represents the reference threshold of an active VSWR of 2. After loading the hybrid decoupling structure, the active VSWR during antenna scanning is significantly improved and remains below the dashed line, while the active VSWR without the hybrid decoupling structure is above the dashed line, indicating a sharp deterioration in performance.

[0082] Figure 16 The surface current distribution of the first metal layer 1 at four time points is shown for the proposed dual-circularly polarized phased array antenna when only element 1 is excited. The surface current distribution on the first metal layer 1 mainly appears in red, orange, yellow, green and blue, with the current density decreasing in that order. Red represents the strongest current density and blue represents the weakest current density. Figure 16 In Figure (a), the surface current distribution of the antenna at phase t=0 is shown. Figure 16 In Figure (b), the surface current distribution of the antenna at phase t = T / 4 is shown. Figure 16 In the diagram (c), the surface current distribution of the antenna at the phase time t = 2 × T / 4 is shown. Figure 16 In the figure (d), the surface current distribution of the antenna at the phase time t = 3 × T / 4 is shown. Figure 16 It fully demonstrates one cycle of current flow on the antenna surface. Figure 16 The purple arrows indicate the direction of surface current flow in the radiating patch of element 1, the black arrows indicate the direction of surface current flow in the short-circuited arm of the star-shaped decoupling structure, and the pink arrows indicate the direction of surface current flow in the oblique open arm of the star-shaped decoupling structure. When only element 1 is excited, the coupling components in its radiation field propagate to the other elements and the hybrid decoupling structure, including spatial near-field coupling of the main polarization and cross-polarization. Figure 16 The surface current distribution shows that at phase t=0, unit 1 acts as the excitation source, with its main current direction downwards. The currents in the four short-circuited arms (vertical upper arm, vertical lower arm, horizontal right arm, and horizontal left arm) of the hybrid decoupling structure all point towards the center node of the structure. The current direction indicates that the induced current propagates from each short-circuited end towards the center. Among the four oblique open-circuited arms, the current in the upper left oblique arm points towards the center, while the currents in the upper right, lower left, and lower right oblique arms move away from the center. This indicates that the induced current in the upper left oblique arm, which faces the excitation source, propagates towards the center, while the currents in the other three oblique arms propagate from the center towards the open-circuited end. At phase t=2×T / 4, the current in unit 1 reverses to upwards, and the currents in the eight arms of the hybrid decoupling structure synchronously reverse direction: the four short-circuited arms move away from the center, and the four oblique open-circuited arms reverse direction, proving that standing wave currents are formed on each arm and are stably locked in phase with the excitation source. Based on the round-trip phase delay characteristic of a quarter-wavelength transmission line, the short-circuit arm, due to its terminal short-circuit reflection coefficient of +1 and a round-trip path of half wavelength, introduces a 180° net phase change in its reflected current relative to the incident current; the oblique open-circuit arm, due to its terminal open-circuit reflection coefficient of -1, introduces a 360° net phase change. The secondary radiation field excited by the superposition of the reflected currents of each arm at the central node, when propagating to adjacent and diagonally opposite passive units, forms a coherent superposition with the original coupling field with the same amplitude but opposite phase, thereby achieving mutual coupling suppression. It should be noted that the grounding metal post 8 at the end of the short-circuit arm is not an energy dissipation channel; its current propagating back and forth on the arm indicates that the grounding end participates in standing wave formation as a reflection boundary.

[0083] Compared with existing technical solutions, the present invention has the following advantages and beneficial effects:

[0084] (1) This invention utilizes a hybrid decoupling structure, namely, the synergistic effect of two decoupling structures with different operating characteristics, namely open-circuit and short-circuit, to effectively reduce the mutual coupling between array elements under wide operating bandwidth and dual circular polarization conditions, without increasing the structural complexity and profile height of the antenna. In addition, this invention places the star-shaped decoupling structure at the center of the four antenna elements, which solves the problem that conventional decoupling structures occupy too much space and are only suitable for linear arrays or one-dimensional area arrays. Furthermore, the structural features of the open-circuit decoupling structure are optimized to be concave, which has the advantage of miniaturization compared to conventional rectangular strips, making it easier to arrange array elements with a compact spacing.

[0085] (2) The hybrid decoupling structure used in this invention is not only applicable to dual circularly polarized array antennas, but also effectively improves the active standing wave ratio and axial ratio of dual circularly polarized phased array antennas during beam scanning, and is suitable for expansion into large two-dimensional scanning phased arrays.

[0086] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure, characterized in that, It includes a first metal layer, a top dielectric substrate, a second metal layer, an intermediate prepreg adhesive sheet, a third metal layer, a bottom dielectric substrate, and a metal base plate, wherein: The first metal layer includes a star-shaped metal strip and four pairs of concave metal strips. Each pair of concave metal strips includes two parallel and symmetrical concave metal strips. The four pairs of concave metal strips are located above, below, left, and right of the star-shaped metal strip, respectively, with their concave surfaces facing the star-shaped metal strip. The first metal layer is disposed on the upper surface of the top dielectric substrate, and the second metal layer is disposed on the lower surface of the top dielectric substrate. The cross-shaped metal strip is connected to the second metal layer by a grounding metal post, which passes through the top dielectric substrate. The third metal layer is disposed on the upper surface of the bottom dielectric substrate, and the metal base plate is disposed on the lower surface of the bottom dielectric substrate. The second metal layer and the metal base plate are connected by an isolation metal pillar, which passes through the intermediate layer prepreg adhesive sheet and the bottom dielectric substrate. The third metal layer and the metal base plate are connected by a metal probe, which passes through the bottom dielectric substrate. The third metal layer is bonded to the second metal layer by an intermediate prepreg adhesive sheet.

2. The broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure according to claim 1, characterized in that, The first metal layer also includes four metal patches, which are formed by stacking cross-shaped and square metal patches. A square groove is etched in the center of each metal patch. The four metal patches are symmetrically arranged about the central axis of the first metal layer. Each pair of U-shaped metal strips is located between two metal patches, and the star-shaped metal strip is located at the center surrounded by the four metal patches.

3. A broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure according to claim 2, characterized in that, Four slots are etched on the second metal layer. The top, bottom, left and right ends of the cross-shaped metal strip are connected to the second metal layer through grounding metal posts. The center of the four slots corresponds to the center of the four metal patches. The four slots are symmetrically distributed with the central axis of the second metal layer as the reference.

4. A broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure according to claim 3, characterized in that, The slot is a star-shaped slot with missing corners.

5. A broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure according to claim 4, characterized in that, The notched star-shaped slot includes eight slot arms, with the lower right slot arm being the shortest. The other slot arms are symmetrical in pairs and have the same length. The lower left and upper right slot arms are longer than the other slot arms.

6. A broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure according to claim 3, characterized in that, The third metal layer includes four Ω-shaped feed lines and eight disks. The four Ω-shaped feed lines are symmetrical about the central axis. Each Ω-shaped feed line is connected to a disk at both ends. There are two isolation metal pillars between the two disks of each Ω-shaped feed line. The two isolation metal pillars are arranged diagonally. Each metal disk is connected to a metal probe.

7. A broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure according to claim 6, characterized in that, Eight circular holes are etched on the metal base plate. The center point of each hole corresponds to the center point of the metal probe and the center point of the disk. The end of the metal probe that passes through the metal base plate is connected to a power supply port.

8. A broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure according to claim 6, characterized in that, The Ω-type feeder includes two narrow bent feeders and one wide bent feeder. The two narrow bent feeders are arranged symmetrically, and all two narrow bent feeders and one wide bent feeder are chamfered at the bends.

9. A broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure according to claim 2, characterized in that, The second metal layer is connected to the metal base plate by metal pillars. 32 metal pillars surround each Ω-shaped feeder in a square, for a total of 128 metal pillars.

10. A broadband dual-circularly polarized phased array antenna with a loaded hybrid decoupling structure according to claim 1, characterized in that, Both the top and bottom dielectric substrates are made of RO4350B material, and the intermediate prepreg adhesive sheet is made of RO4450F material.

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