A W-band rotating circularly polarized magnetoelectric dipole antenna array

Abstract

The present invention proposes a W-band rotating circularly polarized magnetoelectric dipole antenna array, which belongs to the field of antenna technology and is used to solve the problems of narrow axial ratio bandwidth and complex structure of antenna arrays in the prior art. The antenna array includes an antenna radiation structure and a feed transmission structure stacked up and down. Four metal patch modules are etched on the antenna radiation structure and are distributed rotationally symmetrically along the central axis, and a vertical metal through-hole is provided below the antenna radiation structure. The feed transmission structure is a metal plate, and four metal waveguides are milled inside the plate and are rotationally fed with an excitation with a phase gradient. A short-circuit path is provided at the upper port, and a coupling gap is opened. The axial ratio bandwidth is effectively expanded by the rotationally symmetrical arrangement of the feed structure and radiation structure. The present invention can be used for millimeter wave antenna communication and high-resolution radar imaging.

Description

Technical Field

[0001] The present invention belongs to the field of antenna technology, and in particular relates to a W-band rotating circularly polarized magnetoelectric dipole antenna array, which can be used for millimeter wave antenna communication and high-resolution radar imaging. Background Art

[0002] With the development of modern wireless technology, communication equipment with wide bandwidth, high transmission rate, miniaturization and multi-functional integration has become a development trend. Since high frequency bands such as millimeter waves can meet the above requirements, they have become a research hotspot in recent years. Millimeter waves refer to electromagnetic waves with frequencies in the range of 30GHz to 300GHz, corresponding to wavelengths of 1mm to 10mm. The W-band antenna involved in the present invention belongs to the millimeter wave antenna. Compared with low frequency bands, millimeter wave antenna equipment has the advantages of wide bandwidth, small structure size, good communication security, and high target recognition resolution. At the same time, the atmospheric attenuation in the frequency band near specific frequencies in the W band is relatively small. Antennas operating at this frequency have important applications in systems such as high-resolution radar, point-to-point data transmission, precision guidance, and high-resolution radar imaging.

[0003] Essentially, a magnetoelectric dipole antenna is a complementary antenna. The electric dipole's E-plane radiation pattern is an "8" shape, while the H-plane's is a "0" shape. The magnetic dipole's E and H-plane radiation patterns are the exact opposite. If the orthogonally positioned electric and magnetic dipole antennas are excited with equal amplitude and in phase, the resulting radiation pattern is a cardioid that is symmetrical in the E and H planes, resulting in symmetrical E and H-plane radiation patterns and extremely low backscatter.

[0004] Antennas can be categorized by polarization characteristics: linear, circular, and elliptical. Linearly polarized antennas are the most widely used. Compared to linearly polarized antennas, circularly polarized antennas offer advantages in interference resistance, rain and fog resistance, and attenuation resistance. Furthermore, they do not require strict directivity between the transmitting and receiving antennas. These advantages have led to significant research interest in circularly polarized antennas.

[0005] In his master's thesis, "Research on W-Band Planar Array Antennas," Peng Liyao proposed a W-band circularly polarized magnetoelectric dipole antenna with a center frequency of 77 GHz. The antenna elements utilize SIW slot feeding, achieving a maximum gain of 8.8 dB, an 18.2% impedance bandwidth, and a 17.6% axial ratio bandwidth. He also implemented an array design, designing a 2x2 circularly polarized antenna array with an increased gain of 14.4 dB and a sidelobe level of -10.8 dB. While this array antenna achieves a W-band circularly polarized magnetoelectric dipole array antenna design, its uniform array configuration only improves gain without considering the axial ratio bandwidth. The large element spacing results in high sidelobe levels. The SIW slot feeding of the antenna elements requires a multi-layer PCB structure, resulting in a complex and costly design that is not suitable for large-scale production. Furthermore, the antenna utilizes a single-port input feed, with a constant feed phase for each element, hindering further phased array design.

[0006] In general, the main shortcomings of the existing technology are as follows:

[0007] First, in the prior art, the antenna unit uses SIW slot excitation feeding, which requires the design of a multi-layer PCB structure and SIW transmission line. At the W-band 94GHz frequency, the manufacturing process is complex and the cost is high, which is not conducive to large-scale mass production.

[0008] Second, conventional antenna arrays are uniform planar arrays, where all antenna elements are identical. This only increases gain but does not improve the axial bandwidth of the antenna array. Furthermore, the large spacing between array elements results in high sidelobe levels.

[0009] Third, the antenna array in the prior art is single-port fed, and the feeding phase of each wire unit is constant, which is not conducive to the realization of large-scale phased arrays. Summary of the Invention

[0010] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a W-band rotating circularly polarized magneto-electric dipole antenna array, which aims to further expand the axial ratio bandwidth, reduce the sidelobe level of the antenna array, and reduce the complexity of the feed transmission structure, reduce the production cost, and further realize the related design of the phased array on the basis of the W-band circularly polarized magneto-electric dipole antenna.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] A W-band rotating circularly polarized magnetoelectric dipole antenna array includes an antenna radiation structure and a feed transmission structure stacked up and down, wherein:

[0013] The antenna radiation structure is a dielectric substrate with four metal patch modules etched on its upper surface, distributed rotationally symmetrically along the central axis of the dielectric substrate. Each metal patch module is composed of four rectangular metal patches arranged in two rows and two columns, with a pair of diagonally positioned patches connected by a metal strip. A vertical metal through-hole penetrating the dielectric substrate is provided below each rectangular metal patch.

[0014] The feeding transmission structure is a metal plate with four rectangular waveguides milled inside at positions corresponding to the metal patch modules. The rectangular waveguide on one diagonal is a straight waveguide, and the rectangular waveguide on the other diagonal is a torsional waveguide that rotates about a vertical axis. The lower ports of the four rectangular waveguides are evenly distributed, and the upper ports are provided with short-circuit surfaces with coupling slots formed thereon. The upper ports of the rectangular waveguides and the coupling slots are rotationally symmetrically distributed about the central axis of the metal plate.

[0015] In one embodiment, in the metal patch module, a cut angle 1 is set at the four outermost vertices, and a pair of patches in a diagonal position that are not connected by a metal strip are set at a vertex close to the center of the metal patch module. The cut angle 2 is larger than the cut angle 1.

[0016] In one embodiment, in the metal patch module, the metal strips connecting a pair of diagonally positioned patches face the center of the dielectric substrate.

[0017] In one embodiment, the distribution positions of the vertical metal through holes are axisymmetric about two axes of the corresponding metal patch module.

[0018] In one embodiment, the twisted waveguide is a three-layer structure, wherein the lower layer structure is consistent with the straight waveguide, the middle layer is a twisted structure rotated 45° along the vertical center axis of the twisted waveguide, and the upper layer is a rectangular waveguide structure rotated 90° along the vertical center axis of the twisted waveguide and the size is consistent with the lower layer structure.

[0019] In one embodiment, the twisted structure is a bow tie structure, that is, wide at both ends and narrow in the middle, with the length direction being a diagonal direction, and the width increasing in a streamlined manner from the middle to the two ends.

[0020] In one embodiment, the non-diagonal center axis of the metal patch module, the length direction center axis of the coupling gap corresponding to the metal patch module, the length direction center axis of the straight-through waveguide corresponding to the metal patch module, and the length direction center axis of the twisted waveguide corresponding to the metal patch module coincide with each other.

[0021] In one embodiment, the four rectangular waveguides are respectively rotated and fed with equal-amplitude excitation with a phase gradient, and the excitation phases are 0°, 90°, 180°, and 270°, respectively.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention's radiating structure and feed transmission network are both rotationally symmetric. Based on unit circular polarization, this effectively expands the array's circular polarization axial ratio bandwidth, achieving superior circular polarization performance. It also reduces element spacing, lowers the circular polarization axial ratio, and reduces the antenna array's sidelobe level. This invention can be used for millimeter-wave antenna communications and high-resolution radar imaging.

[0024] 2. The present invention consists of a single-layer dielectric substrate (such as a PCB board) located above and a metal plate located below. A radiation structure is etched on the dielectric substrate, and the metal plate is milled to obtain a feed transmission structure. The invention is simple to manufacture, low in cost, and has good structural stability, which is conducive to large-scale mass production.

[0025] 3. The antenna array of the present invention is independently fed for each unit, which can further be used for related designs of large-scale phased arrays. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0027] Figure 2 Schematic diagram of the metal patch module and the corresponding metal through-hole structure of the present invention

[0028] Figure 3 This is a schematic diagram of the feed transmission structure of the present invention, wherein Figure 3 (a) is the overall schematic diagram of the feed transmission structure. Figure 3 (b) is the horizontal cross-section of the lower layer of the feed transmission structure. Figure 3 (c) is the horizontal cross-section of the middle layer of the feed transmission structure. Figure 3 (d) is a horizontal cross-section of the upper layer of the feed transmission structure.

[0029] Figure 4 1 and 2 are the E-plane and H-plane radiation patterns of the antenna array of a specific embodiment of the present invention at 94 GHz.

[0030] Figure 5 FIG. 4 is a graph showing how the axial ratio of the antenna unit to the array varies with frequency according to a specific embodiment of the present invention.

[0031] Figure 6 FIG. 4 is a graph showing how the standing wave ratio of the antenna array varies with frequency according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0032] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0033] Reference Figure 1The present invention provides a W-band rotating circularly polarized magnetoelectric dipole antenna array, comprising an antenna radiation structure 1 and a feed transmission structure 2 stacked up and down.

[0034] Antenna radiating structure 1 comprises a dielectric substrate. In this embodiment of the present invention, the dielectric substrate is Rogers 5880, with a relative dielectric constant of 2.2, a thickness of 0.508 mm, and lateral dimensions of 5 mm x 5 mm. Four metal patch modules 11 are etched on the top surface of the dielectric substrate, rotationally symmetrically distributed along the central axis of the dielectric substrate. In this embodiment of the present invention, the etched metal is 0.02 mm thick, and the lateral and vertical spacing between the metal patch modules 11 is 2.3 mm.

[0035] Reference Figure 2 Each metal patch module 11 is composed of four rectangular metal patches arranged in two rows and two columns, wherein a pair of patches at a diagonal position are connected by a metal strip. In an embodiment of the present invention, a cut corner 1 is provided at the four outermost vertices, and a pair of patches at a diagonal position that are not connected by a metal strip is provided with a cut corner 2 at a vertex close to the center of the metal patch module 11. A vertical metal through hole 12 that passes through the dielectric substrate is provided below each rectangular metal patch, and in an embodiment of the present invention, the distribution position of the vertical metal through hole 12 is symmetrical about the two axes of the metal patch module 11 (i.e., the row axis and the column axis of the four rectangular metal patches). For example, the length direction of the connecting metal strip is toward the center of the dielectric substrate.

[0036] Each metal patch module 11 and the four vertical metal through-holes 12 arranged below it together constitute a circularly polarized magnetoelectric dipole antenna unit. In an embodiment of the present invention, the second cut angle is greater than the first cut angle. For example, the length L1 of the rectangular metal patch is 0.7mm, the width W1 is 0.58mm, the length T1 of the outermost cut angle is 0.1mm, the horizontal spacing S1 of the rectangular metal patch is 0.08mm, the vertical spacing S2 is 0.06mm, the width M1 of the connecting metal strip is 0.34mm, the distances between the vertical metal through-hole 12 and the two symmetry axes are C1=0.44mm and C2=0.4mm respectively, and the diameter D of the vertical metal through-hole 12 is 0.27mm. It is worth noting that the "horizontal" and "vertical" here are both horizontal directions, which are comparable to the X and Y directions in the XYZ coordinate system. In the present invention, "vertical" refers to the vertical direction, which is comparable to the Z direction in the XYZ coordinate system.

[0037] Reference Figure 3The feed transmission structure 2 of the present invention is a metal plate. In the embodiment of the present invention, the lateral dimensions of the metal plate are the same as those of the upper dielectric substrate, both of which are 5mm×5mm, and the height of the metal plate is 3.5mm. Four rectangular waveguides are milled inside the metal plate, and these four rectangular waveguides correspond to the four metal patch modules 11 in the vertical direction. The two rectangular waveguides on one diagonal line are straight waveguides 22, and the rectangular waveguide on the other diagonal line is a twisted waveguide 23, as shown in FIG. Figure 3 As shown in (a), the twisted waveguide 23 is twisted 90° along the vertical axis from the lower layer to the upper layer.

[0038] Specifically, the twisted waveguide 23 can be divided into a three-layer structure, the lower layer structure of which is consistent with the straight waveguide 22, and the four rectangular waveguides are axially symmetrically distributed, such as Figure 3 The middle layer is a twisted structure rotated 45° along the vertical center axis of the twist waveguide 23. Specifically, the two rectangular waveguides on one diagonal line remain consistent with the lower layer, while the two rectangular waveguides on the other diagonal line rotate 45° counterclockwise relative to the lower layer, presenting a twisted structure, as shown in FIG. Figure 3 As shown in (c), the upper layer is a rectangular waveguide structure that is rotated 90° along the vertical center axis of the twisted waveguide 23 and has the same size as the lower layer structure. Specifically, the two rectangular waveguides on one diagonal line are consistent with the lower layer, and the two rectangular waveguides on the other diagonal line are twisted 90° compared to the lower layer, as shown in FIG. Figure 3 As shown in (d), the lower ports of the four rectangular waveguides are evenly distributed, while the upper ports are provided with short-circuit boards and coupling slots 21. The upper ports of the rectangular waveguides and the coupling slots 21 are rotationally symmetrical about the central axis of the metal plate.

[0039] In the present invention, the twisted structure of the middle layer of the twisted waveguide 23 is referred to as a "bow tie" structure, meaning that its cross-section resembles a bow tie, with wide ends and a narrow center. Its length is diagonal, and its width increases in a streamlined manner from the center toward the ends.

[0040] The central axes of the metal patch module 11, its corresponding coupling slot 21, and the rectangular metal waveguide 22 or 23 all coincide. Specifically, the non-diagonal central axis of the metal patch module 11, the longitudinal central axis of the coupling slot 21 corresponding to the metal patch module 11, the longitudinal central axis of the straight waveguide 22 corresponding to the metal patch module 11, and the longitudinal central axis of the twist waveguide 23 corresponding to the metal patch module 11 coincide with each other. In an embodiment of the present invention, the rectangular waveguide has a length L2 of 2 mm and a width W2 of 1 mm. The horizontal and vertical spacing between the rectangular waveguides is P1 = 2.3 mm. Here, the horizontal and vertical spacing refers to the center-to-center spacing between adjacent rectangular waveguides. The middle layer's twist structure has a length L3 = 2.7 mm, an outer width W3 = 1.35 mm, and an inner width W4 = 1.05 mm. To reduce the area occupied by the bowtie twist structure and facilitate processing, the four outer edges of the bowtie twist structure are rounded with a radius of 0.4 mm. The length L5 of the coupling gap is 1.65mm, and the width W5 is 0.29mm. The four coupling gaps are rotated about the central axis. Figure 3 As shown in (b), (c) and (d).

[0041] The working principle of the present invention is as follows: the antenna array is fed through a rectangular waveguide, and the rotary feeding function is realized through the feeding transmission structure of the lower layer, and the equal-amplitude excitation with a phase gradient is rotated and fed into the four waveguides in sequence, and the excitation phases are 0°, 90°, 180°, and 270° respectively. The slot-coupled feeding is performed on the antenna radiation structure of the upper layer through the coupling slot 21 set at the terminal of the rectangular waveguide, and the circularly polarized magnetoelectric dipole antenna unit composed of the metal patch module and the vertical metal through-hole set thereunder is radiated. The central rotationally symmetrical design of the radiation structure and the rotary feeding can effectively reduce the axial ratio of the antenna array.

[0042] Therefore, this invention further simplifies the structure of the traditional circularly polarized magnetoelectric dipole antenna, improving the antenna's impedance bandwidth and axial ratio bandwidth. Furthermore, through the rotational placement of the elements and independent differential feeding, the axial ratio bandwidth is further expanded. This invention can be used for millimeter-wave antenna communications and high-resolution radar imaging.

[0043] The following simulation experiments are used to further illustrate the technical effects of the present invention:

[0044] 1. Simulation software

[0045] The above embodiment is simulated using the commercial simulation software HFSS_2020R1.

[0046] 2. Simulation content and result analysis

[0047] Simulation 1: The E-plane and H-plane radiation patterns of the antenna array in the specific embodiment at 94GHz are simulated, and the results are as follows: Figure 4 shown.

[0048] Simulation 2 simulates the curve of the axial ratio of the antenna unit and the array of the specific embodiment with frequency, and the results are as follows: Figure 5 shown.

[0049] Simulation 3 simulates the curve of standing wave ratio of antenna array of specific embodiment with frequency variation, and the result is as follows: Figure 6 shown.

[0050] As a high-frequency band of millimeter waves, the W band has the advantages of wide bandwidth, small structure size, good communication security, and high target recognition resolution compared to low-frequency bands. At the same time, the antenna array in this embodiment is at a frequency of 94GHz, which is one of the atmospheric windows of the millimeter wave band. Electromagnetic waves at this frequency can pass through the earth's atmosphere with high efficiency and low loss, and have great application prospects in satellite communications. Figure 4 According to the simulation, its maximum gain is 13.8dB, the half-power beam width is 35 degrees, the sidelobe level is -15.7dB, and the E and H plane radiation patterns are well symmetrical; this shows that the antenna array gain of this embodiment is high, and the characteristics of the symmetrical E and H plane radiation patterns of the magnetoelectric dipole antenna are realized, and the sidelobe level is low.

[0051] Reference Figure 5 In this embodiment, the axial ratio of the antenna array is less than 3dB in the range of 77.8 to 123.2GHz, and the axial ratio is 0.11dB at the center frequency of 94GHz; this shows that the circular polarization performance of the antenna array is good, and compared with the unit axial ratio, the axial ratio bandwidth is greatly expanded by designing the radiation structure and feeding transmission network with rotational symmetry.

[0052] Reference Figure 6 In this embodiment, the antenna array has a standing wave ratio of less than 2 in the frequency range of 84.2 to 110.3 GHz, and a standing wave ratio of 1.45 at the center frequency of 94 GHz. This antenna array has good standing wave characteristics.

[0053] In summary, the present invention realizes a W-band rotating circularly polarized magnetoelectric dipole antenna array. This antenna array greatly expands the circular polarization axial ratio bandwidth and maintains a low sidelobe level by designing the radiation structure and feeding transmission network with rotational symmetry. The antenna array is composed of only a single-layer dielectric substrate and a metal plate underneath, which is simple to manufacture, low in cost, and has good structural stability, which is conducive to large-scale mass production. The antenna array is independently fed for each unit, which can further be used for related designs of large-scale phased arrays.

[0054] It should be noted that the above description is only a preferred embodiment of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A W-band rotating circularly polarized magnetoelectric dipole antenna array, characterized in that: The invention comprises an antenna radiation structure (1) and a feed transmission structure (2) stacked up and down, wherein: The antenna radiation structure (1) is a dielectric substrate, and four metal patch modules (11) are etched on its upper surface and are distributed rotationally symmetrically along the central axis of the dielectric substrate. Each metal patch module (11) is composed of four rectangular metal patches arranged in two rows and two columns, wherein a pair of patches at diagonal positions are connected by a metal strip, and a vertical metal through hole (12) penetrating the dielectric substrate is provided below each rectangular metal patch. The feed transmission structure (2) is a metal plate, and four rectangular waveguides are milled at positions corresponding to the metal patch modules (11) inside the metal plate, wherein the rectangular waveguide on one diagonal line is a straight waveguide (22), and the rectangular waveguide on the other diagonal line is a torsional waveguide (23) that rotates with the vertical axis as the axis; the lower ports of the four rectangular waveguides are evenly distributed, and the upper ports are provided with a short-circuit surface, and the short-circuit surface is provided with a coupling slot (21); the upper ports of the rectangular waveguides and the coupling slot (21) are rotationally symmetrically distributed about the central axis of the metal plate.

2. The W-band rotating circularly polarized magnetoelectric dipole antenna array according to claim 1, characterized in that: In the metal patch module (11), a first cut angle is provided at the four outermost vertices, and a pair of diagonally positioned patches that are not connected by metal strips are provided with a second cut angle at a vertex close to the center of the metal patch module (11), and the second cut angle is larger than the first cut angle.

3. The W-band rotating circularly polarized magnetoelectric dipole antenna array according to claim 1, characterized in that: In the metal patch module (11), the metal strips connecting a pair of diagonally positioned patches face the center of the dielectric substrate.

4. The W-band rotating circularly polarized magnetoelectric dipole antenna array according to claim 1, characterized in that: The distribution positions of the vertical metal through holes (12) are axisymmetric about the two axes of the corresponding metal patch module (11).

5. The W-band rotating circularly polarized magnetoelectric dipole antenna array according to claim 1, characterized in that: The twisted waveguide (23) is a three-layer structure, wherein the lower layer structure is consistent with the straight waveguide (22), the middle layer is a twisted structure rotated 45° along the vertical center axis of the twisted waveguide (23), and the upper layer is a rectangular waveguide structure rotated 90° along the vertical center axis of the twisted waveguide (23) and the size is consistent with the lower layer structure.

6. The W-band rotating circularly polarized magnetoelectric dipole antenna array according to claim 5, characterized in that: The twisted structure is a bow tie structure, that is, wide at both ends and narrow in the middle, with the length direction being a diagonal direction, and the width increasing in a streamlined manner from the middle to the two ends.

7. The W-band rotating circularly polarized magnetoelectric dipole antenna array according to claim 1, characterized in that: The non-diagonal central axis of the metal patch module (11), the longitudinal central axis of the coupling slot (21) corresponding to the metal patch module (11), the longitudinal central axis of the straight-through waveguide (22) corresponding to the metal patch module (11), and the longitudinal central axis of the twisted waveguide (23) corresponding to the metal patch module (11) coincide with each other.

8. The W-band rotating circularly polarized magnetoelectric dipole antenna array according to claim 1, characterized in that: The four rectangular waveguides are respectively rotated and fed with equal-amplitude excitation with a phase gradient, and the excitation phases are 0°, 90°, 180°, and 270° respectively.

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