Millimeter-wave circularly polarized tightly coupled array antenna

Abstract

The present invention discloses a 5G millimeter wave circularly polarized balun-fed tightly coupled array antenna. The antenna mainly solves the problem that the working bandwidth of the existing array antenna in 5G millimeter wave radiation of circularly polarized waves is too narrow. The antenna comprises a first matching layer (1), a second matching layer (2), a third matching layer (3), an antenna array plate (4), a metal electric wall array (5), a feed balun array (6), an upper metal reflector (7) and a lower metal reflector (8). The antenna array plate covers the upper surface of the first matching layer, the metal electric wall array is located in the second matching layer, the upper metal reflector is located between the second matching layer and the third matching layer, the lower metal reflector is located in the third matching layer, the feed balun array is located between the upper metal reflector and the lower metal reflector, and passes through the second matching layer to feed the antenna array plate. The antenna of the present invention has a small size and a good circular polarization axis ratio, can realize the radiation of circular polarized waves in the 5G millimeter wave band, and can be used in mobile communications and satellite systems.

Description

Technical Field

[0001] The present invention belongs to the field of antenna technology, and in particular relates to a millimeter wave circularly polarized tightly coupled array antenna, which can be used in communications and satellite systems. Background Art

[0002] With the widespread adoption of 5G technology, 5G antenna technology is rapidly developing. 5G communications require higher speeds, low latency, high reliability, and low-power, massive connectivity. This places even higher demands on 5G antenna performance, including bandwidth, gain, and directivity. Consequently, a single, independent antenna cannot meet these high-gain requirements. Antenna arrays, however, are widely used in wireless communications due to their advantages in high gain, phase scanning, and pattern shaping.

[0003] 5G frequency bands include the low-frequency FR1 band (450MHz to 6000MHz) and the millimeter wave FR2 band (24250MHz to 52600MHz). The FR1 band, also known as the Sub6G band, is the primary 5G frequency band. Frequencies below 3GHz are referred to as Sub3G, and the remaining frequency bands are referred to as the C-band. FR1 offers advantages such as low frequency, strong diffraction resistance, and excellent coverage, making it the primary spectrum for 5G. Domestic operators currently support the FR1 band, but the FR1 band has largely been allocated, making the development of high-frequency millimeter wave bands for 5G essential. The FR2 band, also known as the millimeter wave band, is an extension of 5G and boasts abundant spectrum resources, ultra-large bandwidth, clean spectrum, and minimal interference. Furthermore, due to its abundant spectrum resources, the millimeter wave band has become the primary evolutionary direction for the next generation of mobile communications, 6G.

[0004] Because electromagnetic waves encounter reflection and refraction during propagation, their polarization direction deflects. This results in a polarization mismatch between the polarization of the electromagnetic wave and the antenna at the receiving end of a typical linearly polarized antenna. Circularly polarized waves, on the other hand, can be received by any linearly polarized antenna, and circularly polarized antennas can also receive incoming waves with any polarization direction. Furthermore, the circularly polarized waves radiated by circularly polarized antennas are unaffected by the Faraday effect generated by the Earth's polar magnetic field and have a strong ability to penetrate the ionosphere. Therefore, they have numerous applications in satellite communications and phased array radar.

[0005] Currently, circularly polarized satellite communication ground antennas are mostly parabolic antennas, dielectric lens antennas, and microstrip patch antennas. Among them: parabolic antennas are simple in design and are more commonly used, but they have a high profile, large size, heavy weight, and are difficult to install. When acting on communication systems or radar systems, the operating bandwidth is relatively narrow. Dielectric lens antennas use a feed mechanical scanning method, have good electrical performance, and can achieve multi-beam and multi-band sharing performance, but have high insertion loss and are difficult to implement array control. Compared with parabolic antennas, microstrip patch antennas have a low profile, are miniaturized, have a simple structure, and are easier to integrate into mobile devices. However, the operating bandwidth of microstrip patch antennas is relatively narrow and is not suitable for broadband antenna arrays.

[0006] For example, in 2021, Lei Wenbing, Hu Bin, and others proposed a dual circularly polarized phased array antenna array in patent document CN 202111206792.4. The antenna includes a cross-shaped gradient elliptical dipole array plate, a dual circularly polarized feed network, a capacitive loading unit, and an AMC reflective floor. The array antenna operates in the 6-18 GHz frequency band and has a simple structure and is easy to process. It can be quickly and easily applied to electronic systems such as airborne and missile-borne satellite communications, electronic countermeasures, and data link communications. However, due to its large antenna size and operating frequency outside the 5G communication band, it is not suitable for small 5G communication equipment.

[0007] To address the impact of coupling between antenna arrays on the radiation performance of the array antenna itself, researchers proposed the tight coupling theory, which has led to the recent development of the tightly coupled array antenna. This theory utilizes capacitive coupling between elements to form an equivalent capacitance between closely spaced elements, thereby expanding the antenna's bandwidth. This compact unit form facilitates array formation and wide-angle scanning, facilitating low-profile, broadband, and miniaturized designs. Furthermore, through a rational feed structure design, a stable 90° phase difference can be achieved, radiating circularly polarized waves and enabling wide-bandwidth circularly polarized scanning of the array.

[0008] In 2021, Wang Shiwei, Li Yin and others proposed a compact ultra-wideband circularly polarized array antenna in patent document CN202120635599.1. It consists of a first substrate, a support structure, a second substrate, a feeding network, a coaxial feeding unit and multiple cross-dipole units. By utilizing the tight coupling between the units, it can meet the radiation characteristics of a reflection coefficient of less than or equal to 10dB, an impedance bandwidth of 104.4%, and an AR bandwidth of 111.8% in the 1.96GHz to 6.24GHz frequency band. However, this array antenna mainly operates in the C band and is not suitable for 5G millimeter wave band communications.

[0009] Domestic operators' 5G millimeter wave bands are within the FR2 band, covering 24.75 GHz to 27.5 GHz and 37 GHz to 43.5 GHz. Currently, circularly polarized antennas operating within the FR2 band include waveguide antennas, substrate-integrated waveguide (SIW) antennas, magnetoelectric dipole array antennas, and microstrip patch antennas. However, for 5G millimeter wave mobile communication devices, waveguide antennas and substrate-integrated waveguide antennas present difficulties in feed design, miniaturization, and integration. The elements in a magnetoelectric dipole array require large spacing, which can lead to grating lobes during beam scanning, resulting in loss of antenna gain and impacting antenna radiation performance. Microstrip patch antennas have a low profile, but their relatively narrow bandwidth prevents them from achieving the widest possible coverage of the main 5G millimeter wave mobile communication bands while maintaining miniaturization. Summary of the Invention

[0010] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and propose an ultra-wideband tightly coupled circularly polarized array antenna to broaden the bandwidth of antenna radiation, achieve coverage of the 5G millimeter wave mobile communication frequency band, suppress the generation of grating lobes, improve the antenna radiation performance, reduce the antenna volume, and improve the integration.

[0011] To achieve the above object, the technical solution of the present invention is implemented as follows:

[0012] A 5G millimeter-wave circularly polarized balun-fed tightly coupled array antenna includes a matching layer, an antenna array plate 4, a feed balun array 6, and a metal reflector. The antenna array plate 4 is provided with a plurality of dipole radiation periodic units, each periodic unit including a y-polarized dipole arm 41 and an x-polarized dipole arm 42. The invention is characterized in that:

[0013] The matching layer is configured as three layers stacked one above the other, namely, a first matching layer 1, a second matching layer 2, and a third matching layer 3;

[0014] The metal reflector is provided in two layers, namely an upper metal reflector 7 and a lower metal reflector 8;

[0015] The second matching layer 2 has a metal electric wall array 5 fixed therein to enhance the coupling within and between antenna units and expand the bandwidth of the antenna array;

[0016] The antenna array plate 4 covers the upper surface of the first matching layer 1, and the y-polarized dipole arm 41 and the x-polarized dipole arm 42 thereof both adopt a metal pentagonal structure with a cross-shaped hollow center and a stepped bottom edge. This extends the current path of the radiation current in the antenna patch, lengthens the electrical length of the radiating unit, and improves the radiation characteristics of the antenna.

[0017] The metal electric wall array 5 is located in the second matching layer 2;

[0018] The upper metal reflector 7 is located between the second matching layer 2 and the third matching layer 3;

[0019] The lower metal reflector 8 is located in the third matching layer 3;

[0020] The feed balun array 6 includes eight feed balun structural units, each of which includes an unbalanced stripline coupler 61, two stripline balun structures 62 and 63, and a group of four combined metal conductive column structures 64, which are located between the upper metal reflector plate 7 and the lower metal reflector plate 8, and pass through the second matching layer 2 through its metal feed conductive column to feed the antenna array plate 4.

[0021] Furthermore, the metal electric wall array 5 includes multiple metal electric wall units, each of which includes a rectangular metal patch 51 and two metal semi-cylinders 52 with a distance of 0.8 mm. The rectangular metal patch 51 is divided into an x-polarization direction patch and a y-polarization direction patch, wherein the aspect ratio of the x-polarization direction patch is in the range of 1.5 to 2.5, and the aspect ratio of the y-polarization direction patch is in the range of 1.5 to 2.5. The height of the metal semi-cylinder 52 is the same as the thickness of the second matching layer 2.

[0022] Furthermore, the antenna array plate 4 includes eight dipole radiation periodic units symmetrically distributed about the center of the antenna dielectric plate, each dipole radiation periodic unit consisting of a y-polarized dipole arm 41, an x-polarized dipole arm 42 and two corresponding interdigital coupling metal patches 43 and 44, respectively. The y-polarized dipole arm 41 is coupled to its corresponding first interdigital coupling metal patch 43, and the x-polarized dipole arm 41 is coupled to its corresponding second interdigital coupling metal patch 44.

[0023] Furthermore, the unbalanced stripline coupler 61 is a four-port coupler composed of two striplines stacked up and down, which is provided with two input ports 611, 612, an output port 613 and a coupling port 614; the two stripline balun structures 62, 63 are stacked up and down, and are respectively connected to the output port 613 and the coupling output port 614 of the unbalanced stripline coupler; the four combined metal conductive column structures 64 are composed of two conductive metal columns 641, 642 in the x-polarization direction and two conductive metal columns 643, 644 in the y-polarization direction and corresponding metal pads, the two conductive metal columns 641, 642 in the x-polarization direction are respectively connected to the two ports of the first stripline balun 62, and the two conductive metal columns 643, 644 in the y-polarization direction are respectively connected to the two ports of the second stripline balun 63.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. By adding a metal electric wall array to the dielectric layer, the present invention can produce a coupling effect between the antenna array plate and the metal electric wall array, thereby increasing the equivalent capacitance in the antenna array to offset the inductance generated by the reflector in the antenna array, thereby widening the antenna's operating bandwidth and improving the antenna's radiation characteristics.

[0026] 2. The dipole arm apex in the antenna array plate of the present invention adopts a pentagonal structure with a cross-shaped hollow, and its bottom edge adopts a stepped interdigital coupling structure, which extends the current path of the radiation current in the antenna patch, broadens the working bandwidth of the antenna, and improves the axial ratio of the antenna.

[0027] 3. The feeding balun unit in the antenna array of the present invention adopts an unbalanced stripline coupler, two stripline balun structures and a group of four combined metal conductive column structures, and the external feed is connected to the unbalanced stripline coupler. Through the transmission of the stripline balun structure, the combined metal conductive column structure directly feeds the antenna array board, which can realize the radiation of circularly polarized electromagnetic waves, improve the radiation performance of the antenna array, reduce the cross-section of the feeding structure, reduce the height of the antenna array, and contribute to the promotion of miniaturization of the antenna.

[0028] 4. The present invention adopts a double reflector structure to isolate the main structure of the antenna feed from the antenna array plate, thereby avoiding the influence of the feed current on the antenna radiation and improving the antenna radiation characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0030] Figure 2 Schematic diagram of the array unit structure in the present invention;

[0031] Figure 3 1 is a schematic diagram of the top view of the antenna unit in the present invention;

[0032] Figure 4 Schematic diagram of the feed balun structure in the present invention;

[0033] Figure 5 Schematic diagram of a top view of the feed balun line structure in the present invention;

[0034] Figure 6 Schematic diagram of the metal conductive column structure in the feed balun structural unit of the present invention;

[0035] Figure 7 is a standing wave ratio diagram of the input port of the antenna unit in the present invention;

[0036] Figure 8 is a diagram of the axial ratio of the circularly polarized radiation of the antenna unit in the present invention;

[0037] Figure 9is the E-plane radiation pattern of the antenna unit in the present invention at 26 GHz when the scanning angle is 0°;

[0038] Figure 10 is the E-plane radiation pattern of the antenna unit in the present invention at a scanning angle of 0° at 38 GHz;

[0039] Figure 11 is the E-plane radiation pattern of the antenna unit in the present invention at 43 GHz when the scanning angle is 0°;

[0040] Figure 12 is the axial ratio image of the circularly polarized waves radiated by the array antenna of the present invention;

[0041] Figure 13 It is the maximum radiation pattern of the array antenna of the present invention that changes with frequency when the scanning angle is 0°;

[0042] Figure 14 It is the maximum circular polarization radiation pattern of the array antenna of the present invention that varies with the angle when the scanning angle is 0° at 26 GHz;

[0043] Figure 15 It is the maximum circular polarization radiation pattern of the array antenna of the present invention when the scanning angle is 0° at 38GHz;

[0044] Figure 16 This is the maximum circular polarization radiation pattern of the array antenna of the present invention that changes with the angle when the scanning angle is 0° at 43 GHz.

[0045] Figure 17 It is the maximum circular polarization radiation pattern of the array antenna of the present invention that changes with the angle when the scanning angle is 60° at 26GHz;

[0046] Figure 18 It is the maximum circular polarization radiation pattern of the array antenna of the present invention that changes with the angle when the scanning angle is 60° at 38GHz;

[0047] Figure 19 This is the maximum circular polarization radiation pattern of the array antenna of the present invention that changes with the angle when the scanning angle is 60° at 43 GHz. DETAILED DESCRIPTION

[0048] The embodiments and effects of the present invention are further described below with reference to the accompanying drawings:

[0049] Reference Figure 1This embodiment includes a first matching layer 1, a second matching layer 2, a third matching layer 3, an antenna array plate 4, a metal electric wall array 5, a feed balun array 6, an upper metal reflector 7, and a lower metal reflector 8. The antenna array plate 4 covers the upper surface of the first matching layer 1, the metal electric wall array 5 is located in the second matching layer 2, the upper metal reflector 7 is located between the second matching layer 2 and the third matching layer 3, and the lower metal reflector 8 is located within the third matching layer 3. The feed balun array 6, whose main structure is located between the upper metal reflector 7 and the lower metal reflector 8, feeds the antenna array plate 4 via its metal conductive columns, which extend upward through the metal reflector 7, the second matching layer 2, and the first matching layer 1. The upper metal reflector 7 and the second metal reflector 8 serve as isolation for the feed balun array 6. Each unit of the metal electric wall array 5, together with each unit of the antenna array plate 4 above it and each unit of the balun array 6 below it, along with its reflectors and matching layers, constitutes an antenna unit.

[0050] Reference Figure 2 The metal electric wall array 5 includes multiple metal electric wall units, each of which includes a coupling metal patch 51 and two metal cylinders 52. The coupling metal patch 51 and the two metal cylinders 52 form a gate-shaped structure. The coupling metal patch 51 is located between the first matching layer 1 and the second matching layer 2 and is embedded in the first matching layer. The metal cylinders are located in the second matching layer and penetrate the second matching layer 2, connecting to the coupling metal patch 51.

[0051] Reference Figure 3 The antenna array plate 4 is located above the metal electric wall array 5 and includes eight array plate units. Each array plate unit is also called a dipole radiation unit, which includes a y-polarization direction dipole arm 41, a y-polarization direction interdigital coupling metal patch 43, an x-polarization dipole arm 42, and an x-polarization direction interdigital coupling metal patch 44. The y-polarization dipole arm 41 is in the shape of a pentagon, the vertices of the pentagon are arc-shaped, the center is a cross-shaped hollow structure, and its bottom edge adopts a stepped interdigital coupling structure and is coupled with the interdigital coupling metal patch 43. The x-polarization dipole arm 42 has the same shape and structure as the y-polarization dipole arm 41 and is coupled with the interdigital coupling metal patch 44. The cross-shaped hollow structure and stepped interdigital coupling structure adopted by these two dipole arms can extend the current path of the radiation current in the antenna patch, lengthen the electrical length of the radiation unit, and improve the radiation characteristics of the antenna.

[0052] Reference Figure 4 、 Figure 5 and Figure 6 The coupled feed balun structure unit 6 includes: an unbalanced stripline coupler 61, two stripline balun structures 62, 63 and a group of four combined metal conductive column structures 64, wherein:

[0053] The unbalanced stripline coupler 61 is a four-port coupler consisting of two striplines stacked one above the other, namely, an input port 611 , an isolation port 612 , an output port 613 , and a coupled output port 614 .

[0054] The two stripline balun structures 62 and 63 are stacked one above the other, with the first stripline-fed balun 62 located at the bottom. It includes a hook-shaped stripline 621, a lower circular stripline transmission line 622, and two lower balun output ports 623 and 624. These two lower balun output ports 623 and 624 are connected by a lower semicircular stripline transmission line 622. The lower circular stripline transmission line 622 has a phase difference of 180°. The hook-shaped stripline 621 is composed of a rectangular stripline and a quarter lower circular stripline. The second stripline-fed balun 63 is located above the second stripline-fed balun 62 and includes a quarter upper circular stripline 631, an upper circular stripline transmission line 632, and two upper balun output ports 633 and 634. The upper semicircular stripline transmission line 632 has a phase difference of 180° and is used to connect the two upper balun output ports 633 and 634.

[0055] The metal through-hole structure 64 includes four metal conductive pillars 641, 642, 643 and 644, wherein the first metal conductive pillar 641 and the second metal conductive pillar 642 have the same structure, both consisting of four sections of metal conductive pillars and corresponding metal pads in the first matching layer 1, one section of metal conductive pillar and corresponding metal pads in the second matching layer, and two sections of metal conductive pillars and corresponding metal pads in the third matching layer 3; the third metal conductive pillar 643 and the fourth metal conductive pillar 644 have the same structure, both consisting of four sections of metal conductive pillars and corresponding metal pads in the first matching layer 1, one section of metal conductive pillar and corresponding metal pads in the second matching layer, and one section of metal conductive pillar and corresponding metal pads in the third matching layer 3.

[0056] The feeding current is input from input port 611, and two currents of equal amplitude and 90° phase difference are output from output port 613 and coupling port 614. The current output from output port 613 is fed to hook-shaped stripline 621, with a portion transmitted to first metal conductive post 641 through first output port 623 of the upper balun, and another portion fed to second metal conductive post 642 through second output port 624 of the upper balun, and then simultaneously fed to the left and right arms of dipole arm 41. The current output from coupling port 614 is fed to quarter-circular upper ring stripline 631, with a portion transmitted to third metal conductive post 643 through first output port 633 of the lower balun, and another portion transmitted to fourth metal conductive post 644 through second output port 634, and then simultaneously fed to the upper and lower arms of dipole arm 42, ultimately achieving circularly polarized wave radiation from the dipole antenna.

[0057] The first matching layer 1 and the third matching layer 3 are the same, both made of four layers of dielectric plates with a relative dielectric constant of 3.29 and a tangent loss angle of 0.006. The second matching layer 2 is made of a dielectric plate with a relative dielectric constant of 3.31 and a tangent loss angle of 0.0033.

[0058] The first matching layer 1, the second matching layer 2, the third matching layer 3 and the antenna array plate 4 have the same dimensions, and the length W of their short sides is 0.496 times the wavelength corresponding to the highest operating frequency. The total thickness H of the four is 0.182 times the wavelength corresponding to the highest operating frequency. In this example, W is assumed to be, but not limited to, 3.5 mm and H is assumed to be 1.287 mm. The thickness of the first matching layer 1 of the antenna dielectric layer is h1 = 0.326 mm, the thickness of the second matching layer 2 is h2 = 0.635 mm, and the thickness of the third matching layer 3 is h3 = 0.326 mm.

[0059] In the rectangular metal patch 51 , the aspect ratio of the patch in the x-polarization direction is in the range of 1.5 to 2.5, and the aspect ratio of the patch in the y-polarization direction is in the range of 1.5 to 2.5. The distance between the two metal cylinders 52 is in the range of 0.6 to 0.1 mm, the diameter of the metal cylinder 52 is in the range of 0.2 to 0.3 mm, and the height of the metal cylinder is 0.653 mm, which is the same as the thickness of the second matching layer 2.

[0060] In this example, it is assumed but not limited to that the x-polarization patch is 1.4 mm long and 0.62 mm wide, the y-polarization patch is 1.4 mm long and 0.7 mm wide, the distance between the two metal cylinders 52 is 0.8 mm, and the diameter of the metal cylinder 52 is 0.25 mm.

[0061] The aspect ratio of the square stripline in the hook-shaped stripline 621 in the first feed balun is in the range of 1.5 to 2, the ratio of the inner and outer diameters of the lower semicircular ring-shaped stripline transmission line 622 in the first feed balun is in the range of 0.6 to 0.9, and the ratio of the inner and outer diameters of the upper quarter circular ring-shaped stripline 631 in the second feed balun is in the range of 0.2 to 0.4.

[0062] In this example, it is assumed but not limited to that the width of the square strip line in the hook-shaped strip line 621 is 0.5 mm and the length is 0.775 m, the inner diameter of the lower semicircular ring strip line transmission line 622 is 0.8 mm, the outer diameter is 1.0 mm, and the width is 0.2 mm; the inner diameter of the upper quarter circular ring strip line 631 is 0.25 mm, the outer diameter is 0.75 mm, and the width is 0.5 mm.

[0063] The diameter of the conductive pillars in the metal conductive pillar structure 64 is in the range of 0.1 to 0.3 mm, and the diameter of the corresponding metal pads is in the range of 0.2 to 0.4 mm.

[0064] Due to the different matching layer media, the diameter required for processing the metal conductive column structure 64 is also different. In this example, it is assumed but not limited to that in the first matching layer 1, the radius of the metal conductive column is 0.125 mm, and the corresponding metal pad radius is 0.225 mm. In the second matching layer 2, the radius of the metal conductive column is 0.05 mm, and the corresponding metal pad radius is 0.1125 mm.

[0065] The effects of the present invention can be further illustrated by the following simulation experiments:

[0066] 1. Simulation experiment conditions:

[0067] Commercial simulation software Ansoft HFSS_20.0,

[0068] Scanning frequency bandwidth 20GHz~45GHz, scanning frequency interval 1GHz,

[0069] The scanning space pitch angle theta ranges from 0° to 180°, the spatial azimuth angle phi ranges from 0° to 360°, and data are collected at 1° intervals.

[0070] 2. Simulation experiment content

[0071] Simulation 1: Under the above conditions, the antenna unit port standing wave ratio of the embodiment of the present invention is simulated and calculated in the range of 20GHz to 45GHz. The results are as follows: Figure 7 shown.

[0072] from Figure 7 It can be concluded that the frequency band in which the circular polarization standing wave ratio of the antenna unit port is less than 3 is 20 GHz to 45 GHz; this frequency band covers the 5G millimeter wave operating frequency bands of 24.75 GHz to 27.5 GHz and 37 GHz to 43.5 GHz.

[0073] Simulation 2: Under the above conditions, the axial ratio parameters of the antenna unit of the embodiment of the present invention are simulated in the range of 20GHz to 45GHz. The results are as follows: Figure 8 shown.

[0074] from Figure 8 It can be concluded that the frequency band in which the axial ratio of the antenna unit is less than 3 is 21.94 GHz to 44.10 GHz; and good circularly polarized wave radiation can be achieved in the 5G millimeter wave operating frequency bands of 24.75 GHz to 27.5 GHz and 37 GHz to 43.5 GHz.

[0075] Simulation 3: Under the above conditions, the E-plane radiation patterns of the antenna unit of the embodiment of the present invention at 26 GHz, 38 GHz and 43 GHz are simulated. The results are as follows: Figure 9 、 Figure 10 and Figure 11shown.

[0076] from Figure 9 It can be concluded that the antenna unit can achieve maximum gain at an azimuth angle of Theta = 0° in the E-plane radiation pattern at an operating frequency of 26 GHz.

[0077] from Figure 10 It can be concluded that the antenna unit can achieve maximum gain at an azimuth angle Theta = 0° in the E-plane radiation pattern at an operating frequency of 38 GHz.

[0078] from Figure 11 It can be concluded that the antenna unit can achieve maximum gain at an azimuth angle of Theta = 0° in the E-plane radiation pattern at an operating frequency of 43 GHz.

[0079] comprehensive Figure 9 、 Figure 10 and Figure 11 It can be concluded that the antenna unit has a wide-band radiation circularly polarized beam characteristic within the operating frequency band.

[0080] Simulation 4: Under the above conditions, the axial ratio parameters of the antenna array of the embodiment of the present invention are simulated in the range of 20GHz to 45GHz. The results are as follows: Figure 12 shown.

[0081] from Figure 12 It can be concluded that the frequency band range in which the axial ratio of the antenna array in this example is less than 3 is 23.88 GHz to 27.84 GHz and 34.58 GHz to 44.53 GHz, and it can radiate circularly polarized waves well in the 5G millimeter wave operating frequency bands of 24.75 GHz to 27.5 GHz and 37 GHz to 43.5 GHz.

[0082] Simulation 5: Under the above conditions, the maximum radiation directional gain of the antenna array of the embodiment of the present invention is simulated and calculated in the range of 20GHz to 45GHz. The results are as follows: Figure 13 shown.

[0083] from Figure 13 It can be concluded that when the scanning angle of the array antenna in this example is 0°, the gain in the maximum radiation direction varies with frequency. The maximum gain achievable in the 5G frequency bands of 24.75 GHz to 27.5 GHz and 37 GHz to 43.5 GHz is 10.2 dB and 11.27 dB, respectively, indicating that the antenna array has good radiation characteristics.

[0084] Simulation 6: Under the above conditions, the antenna array of the embodiment of the present invention is simulated and calculated at 26 GHz in the low frequency band, 38 GHz in the high frequency band, and 43 GHz in the high frequency band, and the radiation pattern of the gain varying with the azimuth angle Theta when phi = 0° is obtained. The results are as follows: Figure 14 、 Figure 15 and Figure 16 shown.

[0085] from Figure 14 It can be concluded that when the scanning angle is phi = 90°, the array antenna can achieve a maximum gain of 10.10 dB at an azimuth angle of 0°.

[0086] from Figure 15 It can be concluded that when the scanning angle is phi = 90°, the maximum achievable gain of the array antenna at an azimuth angle of 0° is 11.27 dB.

[0087] from Figure 16 It can be concluded that when the scanning angle is phi = 90°, the maximum achievable gain of the array antenna at an azimuth angle of 0° is 9.94 dB.

[0088] comprehensive Figure 14 、 Figure 15 and Figure 16 It can be concluded that the array antenna in this example not only has stable circularly polarized radiation beam characteristics in the entire wide frequency band, but also has good radiation gain performance.

[0089] Simulation 7: Under the above conditions, the antenna array of the embodiment of the present invention is simulated and calculated at 26 GHz in the low frequency band, 38 GHz in the high frequency band, and 43 GHz in the high frequency band, and the radiation pattern of the gain varying with the azimuth angle Theta when the scanning angle is 60° is obtained. The results are as follows: Figure 17 、 Figure 18 and Figure 19 shown.

[0090] from Figure 17 It can be concluded that when the scanning angle is phi = 90°, the array antenna can achieve a maximum gain of 10.10 dB at an azimuth angle of 60°.

[0091] from Figure 18 It can be concluded that when the scanning angle is phi = 90°, the maximum achievable gain of the array antenna at an azimuth angle of 60° is 8.54 dB.

[0092] from Figure 19 It can be concluded that when the scanning angle is phi = 90°, the maximum achievable gain of the array antenna at an azimuth angle of 60° is 6.79 dB.

[0093] comprehensive Figure 17 、 Figure 18 and Figure 19 It can be concluded that the array antenna in this example not only has stable wide-angle circularly polarized beam characteristics in the entire wide frequency band, but also has good radiation gain performance.

Claims

1. A 5G millimeter wave circularly polarized tightly coupled array antenna, comprising a matching layer, an antenna array plate (4), a feed balun array (6), and a metal reflector, wherein the antenna array plate (4) is provided with a plurality of dipole radiation periodic units, each periodic unit comprising a y-polarized dipole arm (41) and an x-polarized dipole arm (42), characterized in that: The matching layer is configured as three layers stacked one above the other, namely a first matching layer (1), a second matching layer (2) and a third matching layer (3); The metal reflective plate is provided as two layers, namely an upper metal reflective plate (7) and a lower metal reflective plate (8); The second matching layer (2) has a metal electric wall array (5) fixed therein to enhance coupling within and between antenna units and expand the bandwidth of the antenna array; The antenna array plate (4) is covered on the upper surface of the first matching layer (1), and the y-polarized dipole arm (41) and the x-polarized dipole arm (42) therein both adopt a metal pentagonal structure with a cross-shaped hollow center and a stepped interdigitated bottom edge, so as to extend the current path of the radiation current in the antenna patch, lengthen the electrical length of the radiation unit, and improve the radiation characteristics of the antenna; the antenna array plate (4) includes eight dipole radiation periodic units symmetrically distributed about the center of the antenna dielectric plate, each dipole radiation periodic unit is composed of a y-polarized dipole arm (41), an x-polarized dipole arm (42) and two interdigitated coupled metal patches (43, 44) corresponding thereto, the y-polarized dipole arm (41) is coupled to its corresponding first interdigitated coupled metal patch (43), and the x-polarized dipole arm (42) is coupled to its corresponding second interdigitated coupled metal patch (44); The upper metal reflector (7) is located between the second matching layer (2) and the third matching layer (3); The lower metal reflector (8) is located within the third matching layer (3); The feeding balun array (6) comprises a plurality of feeding balun structural units, each feeding balun structural unit comprising an unbalanced stripline coupler (61), two stripline balun structures (62, 63) and a group of four combined metal conductive column structures (64), which are located between an upper metal reflector (7) and a lower metal reflector (8), and penetrate the second matching layer (2) through their metal conductive columns to feed the antenna array plate (4).

2. The array antenna according to claim 1, wherein: The metal electric wall array (5) includes a plurality of metal electric wall units, each of which includes a rectangular metal patch (51) and two metal semi-circular cylinders (52) with a distance of 0.8 mm. The rectangular metal patch (51) is divided into an x-polarization direction patch and a y-polarization direction patch, wherein the x-polarization direction patch has an aspect ratio within the range of 1.5 to 2.5, and the y-polarization direction patch has an aspect ratio within the range of 1.5 to 2.5; The height of the metal semi-cylinder (52) is the same as the thickness of the second matching layer (2).

3. The array antenna according to claim 1, wherein: The unbalanced stripline coupler (61) is a four-port coupler formed by two striplines stacked one above the other, and is provided with two input ports (611, 612), an output port (613) and a coupling port (614); The two stripline balun structures (62, 63) are stacked up and down, and are respectively connected to the output port (613) and the coupling port (614) of the unbalanced stripline coupler; The four combined metal conductive column structures (64) are composed of two metal conductive columns (641, 642) in the x-polarization direction and two metal conductive columns (643, 644) in the y-polarization direction and corresponding metal pads. The two metal conductive columns (641, 642) in the x-polarization direction are respectively connected to the two ports of the first stripline balun (62), and the two metal conductive columns (643, 644) in the y-polarization direction are respectively connected to the two ports of the second stripline balun (63).

4. The array antenna according to claim 3, wherein: The two metal conductive columns (641, 642) in the x-polarization direction have the same structure, and both include: four sections of metal conductive columns and their corresponding metal pads placed vertically in the first matching layer (1); one section of metal conductive column and its corresponding metal pad placed vertically in the second matching layer (2); two sections of metal conductive columns and their corresponding metal pads placed vertically in the third matching layer (3); the three sections of metal conductive columns and metal pads are stacked up and down, with their central axes located on the same vertical line, and the uppermost metal conductive column reaches the surface of the x-polarized dipole arm (42).

5. The array antenna according to claim 3, wherein: The two metal conductive columns (643, 644) in the y-polarization direction have the same structure, and both comprise: four sections of metal conductive columns and corresponding metal pads placed vertically in the first matching layer (1); one section of metal conductive column and corresponding metal pad placed vertically in the second matching layer (2); and one section of metal conductive column and corresponding metal pad placed vertically in the third matching layer (3); the three sections of metal conductive columns and metal pads are stacked up and down, with their central axes located on the same vertical line, and the uppermost metal conductive column feeds the surface of the y-polarized dipole arm (41).

6. The array antenna according to claim 3, wherein: The first stripline balun (62) comprises: a hook-shaped stripline (621), two balun output ports (623, 624), and an upper circular ring-shaped stripline transmission line (622) connecting the two balun output ports (623, 624), wherein the phase difference of the upper circular ring-shaped stripline transmission line (622) is 180°; the hook-shaped stripline (621) is composed of a rectangular stripline and a quarter-circular ring-shaped stripline.

7. The array antenna according to claim 3, wherein: The second stripline balun (63) comprises: a quarter-circular annular stripline (631), two balun output ports (633, 634), and a lower annular stripline transmission line (632) connecting the two output ports, wherein the phase difference of the lower annular stripline transmission line (632) is 180°.

8. The antenna array according to claim 1, wherein: The first matching layer (1) is formed by stacking four layers of square plate dielectric plates with the same thickness, a relative dielectric constant of 3.29, and a tangent loss angle of 0.006; The second matching layer (2) is a square dielectric plate with a relative dielectric constant of 3.31 and a tangent loss angle of 0.0033; The third matching layer (3) has the same structure and material as the first matching layer (1); The first matching layer (1), the second matching layer (2), the third matching layer (3) and the antenna array plate (4) have the same size, and the length of their short sides is 0.496 times the wavelength corresponding to the highest operating frequency. The total thickness of the four is 0.182 times the wavelength corresponding to the highest operating frequency.

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