Multi-beam switching antenna applied to wind finding radar and working method of multi-beam switching antenna

Abstract

The invention relates to a multi-beam switching antenna applied to a wind finding radar and a working method of the multi-beam switching antenna. The antenna comprises a connecting device, a feed device and a lens device, the connecting device is a subminiature push-in connector, the input end of the connecting device is connected with the wind finding radar, and the output end of the connecting device is connected with the feed device; the feed device comprises a GCPW-SIW conversion structure and a feed source antenna. Wherein the feed source antennas are sixteen antipodal Vivaldi antennas and are used for radiating spherical waves to the lens device; the lens device is a metasurface lens, and the feed device and the lens device are arranged in an offset-focus mode. Therefore, phase compensation is carried out on spherical waves radiated by a feed device located at the focus of the lens, and the spherical waves are converted into plane waves of the emergent surface of the lens. Compared with the prior art, the method has the advantages that the actual application requirement of a wind measurement radar system is met, and accurate wind field measurement and data acquisition are achieved.

Description

Technical Field

[0001] The present invention relates to an antenna, in particular to a multi-beam switching antenna applied to a wind measurement radar and a working method thereof. Background Art

[0002] With the rapid development of science and technology, low-altitude wind measurement radars have demonstrated outstanding performance in the field of meteorological element detection and have gradually gained a foothold in the field of wind measurement. This radar system uses the backscattering effect of atmospheric turbulence on electromagnetic waves to accurately obtain atmospheric information. By transmitting electromagnetic beams in multiple directions to high altitudes (specifically the area above the boundary layer), receiving and processing these signals reflected back due to the uneven vertical structure of the atmosphere, and accurately measuring the Doppler velocity at various distances in different beam directions, and combining the Doppler velocity data at the same altitude under the condition of uniform horizontal distribution of the atmosphere, the wind measurement radar can calculate the three-dimensional wind field information of the atmosphere and achieve accurate detection of low-altitude wind fields.

[0003] Millimeter-wave wind radars offer unique advantages in detecting wind fields at low altitudes (<300m), which is required for wind farms. Antennas play a crucial role in radar systems and are crucial to overall radar performance. Wind radar antenna design must meet the requirements of high precision, high gain, and low sidelobes to ensure dense sampling points within the wind field, enhance detection sensitivity, and reduce clutter interference on echo signals, thereby improving detection accuracy. Therefore, research on multi-beam, high-gain antennas for wind radar applications is of great value.

[0004] In terms of antenna technology, wind measurement radars currently mainly use two types of antennas: phased array antennas and parabolic antennas. Although these two types of antennas can meet the technical requirements of wind measurement radars, the existing antennas have shortcomings such as fewer beams, too high profiles, and complex structures.

[0005] The invention patent with publication number CN112701437A discloses a multi-beam lens antenna system for use in wind measurement radars. The overall structure of the lens antenna includes a Fresnel lens, a corrugated horn feed, and a coaxial waveguide conversion structure. By placing the four corrugated horns at rotationally symmetrical positions around the center of the lens, four beams deflected by ±15° are achieved. This antenna system can only generate four detection beams, and the number of detection beams is limited. As a result, there are only four wind field sampling points within the wind profile at the same altitude, resulting in significantly insufficient density, low wind measurement accuracy, and an inability to achieve a complete characterization of the wind field. Therefore, this existing technology has obvious limitations in meeting the needs of low-altitude high-precision detection, making it difficult to achieve accurate wind field measurement and data collection. Antennas with more beams and high-precision radar wind measurement systems are required.

[0006] In summary, the antenna system currently used in wind measurement radar is difficult to meet the actual application requirements of wind measurement radar system. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a multi-beam switching antenna for wind measurement radar and a working method thereof.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] According to one aspect of the present invention, there is provided a multi-beam switching antenna for use in a wind measurement radar, the antenna comprising: a connecting device, a feeding device, and a lens device;

[0010] The connecting device is an ultra-small push-in connector, the input end of which is connected to the wind measuring radar, and the output end is connected to the feeding device; the connecting device is used to receive the microwave signal transmitted by the wind measuring radar and input the microwave signal into the feeding device;

[0011] The feeding device includes a GCPW-SIW conversion structure and a feed antenna; the feed antenna is sixteen parallel Vivaldi antennas for radiating spherical waves to the lens device;

[0012] The lens device is a metasurface lens, and the feeding device and the lens device are arranged in a defocused manner; thereby performing phase compensation on the spherical wave radiated by the feeding device located at the lens focus and converting it into a plane wave on the lens exit surface.

[0013] As a preferred technical solution, the input end of the GCPW-SIW conversion structure is connected to the connecting device, and the output end is connected to the feed antenna; the GCPW-SIW conversion structure includes a coplanar waveguide, a trapezoidal transition structure and a substrate integrated waveguide; wherein the trapezoidal transition structure is used to realize the quasi-TEM mode of the coplanar waveguide and the quasi-TE mode of the substrate integrated waveguide. 10 Conversion between modes.

[0014] As a preferred technical solution, the radiating arm of the Vivaldi antenna is cut and provided with a choke slot structure. The inner and outer edges of the radiating arm of the Vivaldi antenna both satisfy an exponential gradient curve, and the specific expression is:

[0015] z=ae bx +g

[0016]

[0017]

[0018] Where z is the exponential gradient curve satisfied by the inner and outer edges of the radiating arm of the Vivaldi antenna; a and g are gradient constants; (x1, z1) and (x2, z2) are the starting and ending coordinates of the gradient line, respectively.

[0019] As a preferred technical solution, the Dutu Vivaldi antenna has a double-layer radiation layer structure, including an upper radiation layer and a lower radiation layer, which are isolated and fixed by a dielectric substrate.

[0020] As a preferred technical solution, the cutting process is to cut the radiating arm into a blade shape, so that the straight side length of the radiating arm after cutting is 16.4mm, and the curved side satisfies the exponential equation z=1.15e 5x +1.2; The choke slot structure specifically comprises n choke slots with a depth of 1.3 mm and a width of 1 mm that are evenly arranged on the straight side of the radiation arm.

[0021] As an optimal technical solution, the metasurface lens includes multiple periodically arranged metasurface units, each metasurface unit is composed of five layers of metasurface, including four layers of dielectric plates and five layers of metal patches; the metal patches adopt a U-shaped structure, including a central rectangular patch and an outer metal rectangular wire frame; wherein, the outer metal rectangular wire frame is equivalent to an inductor, and the gap between the outer metal rectangular wire frame and the central rectangular patch is equivalent to a capacitor, and the overall equivalent circuit model is a parallel LC resonator, constituting a bandpass metasurface unit.

[0022] As an optimal technical solution, the defocusing arrangement is specifically as follows: the feed antenna is placed at a position deviated from the focus of the metasurface lens; sixteen parallel Vivaldi antennas are distributed on the focusing surface of the lens, corresponding to different beam deflection angles; the focusing surface of the lens is an arc surface with the center of the lens as the center and the focal length as the radius.

[0023] As a preferred technical solution, the beam deflection angles include ±5°, ±10°, ±15° and ±20°.

[0024] According to another aspect of the present invention, a method for operating a multi-beam switching antenna for a wind measuring radar is provided. The method is applied to the multi-beam switching antenna for a wind measuring radar as described above, and the method comprises the following steps:

[0025] S1, transmit the microwave signal generated by the wind measurement radar to the feeding device through the ultra-small push-in connector;

[0026] In the S2 feeding device, the microwave signal passes through the GCPW-SIW conversion structure to achieve the quasi-TEM mode of the coplanar waveguide and the quasi-TE mode of the substrate integrated waveguide. 10 Conversion between modes to provide feed for the feed antenna;

[0027] S3, sixteen Vivaldi antennas radiate spherical waves toward the metasurface lens, which performs phase compensation on the spherical waves radiated by the feed antennas, converting them into plane waves at the lens exit surface. Multi-beam coverage with different beam deflection angles is achieved through defocusing arrangement.

[0028] S4. The converted plane wave is emitted from the metasurface lens to form a high-gain, low-sidelobe beam, which is used for target detection and wind field measurement by wind radar.

[0029] As a preferred technical solution, the beam deflection angles include ±5°, ±10°, ±15° and ±20°.

[0030] As an optimal technical solution, a beam switching mode is adopted in the multi-beam coverage process. Specifically, a single-pole four-throw RF switch is first set in the RF link, and the deflection angle channel to be detected in the four deflection angle channels is selected, and then the four rotationally symmetric beam direction channels of the same deflection angle are selected in turn, thereby realizing polling detection of a total of sixteen beam directions of the four deflection angles.

[0031] As a preferred technical solution, the specific process of using the metasurface lens to perform phase compensation on the spherical wave radiated by the feed antenna is as follows: the spherical wave is vertically incident, passes through the focus of the metasurface lens, and reaches each metasurface lens unit along different transmission paths. The position of each metasurface lens unit is adjusted to perform phase compensation so that the exit surface of the metasurface lens forms an equal phase surface. The formula for the phase to be compensated for each metasurface lens is:

[0032] Ψ mn =-k(R mn -f)+2tπ

[0033] Among them, mn is the compensation phase of the metasurface lens unit in the mth row and nth column; k = 2π / λ is the free space propagation constant, R mn is the propagation distance from the feed antenna to the metasurface lens unit in the mth row and nth column; f is the focal length of the metasurface lens, and t is a positive integer.

[0034] According to another aspect of the present invention, a wind measurement radar system is provided, the system comprising a signal source, a transceiver module, a signal processor, and a multi-beam switching antenna for use in a wind measurement radar as described above;

[0035] The signal source is used to emit a 24GHz millimeter-wave radio frequency signal, which is then transmitted to the transceiver module for amplification.

[0036] The transceiver module is used to amplify the radio frequency signal and is connected to the feed port of the antenna;

[0037] The signal processor includes a host computer and an FPGA module, and is used to process the received and transmitted radio frequency signals;

[0038] The antenna is used to generate beams that detect different directions to measure wind speed and direction.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The present invention is an antenna applied to a wind measuring radar. By combining the feed antenna and the lens device, the phase compensation of the metasurface lens is precisely designed to achieve precise deflection of the beam; through the defocusing arrangement, effective deflection of the fixed beam is achieved, ensuring that the electromagnetic waves can be accurately radiated into the free space. At the same time, the feed antenna is sixteen parallel Vivaldi antennas. The Vivaldi antenna has a clear phase center, which enables the feed to be accurately placed at the focus of the lens, thereby improving the gain and efficiency of the antenna. Experimental verification shows that the gain of the antenna can reach 30.8dBi, the sidelobe level is lower than -20.1dB, and the half-power beamwidth is 3°. These performance parameters meet the requirements of low-altitude wind measuring radars, so as to achieve accurate wind field measurement and data collection.

[0041] 2. The present invention is an antenna for use in a wind measurement radar. While meeting the requirements of a low-altitude wind measurement radar system, the antenna's cross-sectional height is further reduced by optimizing the stacked structure in the antenna metasurface unit and adopting a thin dielectric substrate and sixteen parallel Vivaldi antenna radiation arm designs. The thin dielectric substrate reduces the size of the antenna in the vertical direction while maintaining good electromagnetic performance. This design enables the antenna to significantly reduce its cross-sectional height while maintaining high gain and low side lobes. The parallel Vivaldi antenna has a double-layer radiation layer structure, which enables the antenna to achieve efficient radiation performance in a limited space. By optimizing the shape and size of the radiation arm, the inner and outer edges of the radiation arm both meet the exponential gradient curve, which can improve the gain and directivity of the antenna without increasing the cross-sectional height, so that it has a low-section characteristic. The lower cross-sectional height not only reduces the reflection of electromagnetic waves in the lens and the dielectric loss, but also makes the lens thin and easy to manufacture, thereby reducing the manufacturing cost and complexity of the antenna.

[0042] 3. In an antenna used in a wind measurement radar, the present invention comprises sixteen parallel Vivaldi antennas as the feed antenna. The sixteen Vivaldi antennas radiate spherical waves toward a metasurface lens, which then performs phase compensation on the spherical waves radiated by the feed antenna, converting them into plane waves at the lens's exit surface. By designing sixteen beams, the present invention can provide more sampling points within a fixed-height horizontal sampling plane compared to conventional antennas with four or fewer beams. These additional sampling points can capture richer wind field information, enabling the antenna to exhibit good echo quality and wind measurement accuracy in multiple wind measurement scenarios, thereby improving the accuracy of wind field detection.

[0043] 4. In an antenna for a wind measurement radar of the present invention, the GCPW-SIW conversion structure includes a coplanar waveguide, a trapezoidal transition structure, and a substrate integrated waveguide; wherein the trapezoidal transition structure is used to realize the quasi-TEM mode of the coplanar waveguide and the quasi-TE mode of the substrate integrated waveguide. 10 Mode conversion: Through the grounded coplanar waveguide-substrate integrated waveguide (GCPW-SIW) conversion structure, the electromagnetic waves fed by the GCPW are efficiently converted into electromagnetic waves propagating in the SIW, thereby reducing feeding losses and improving the overall performance of the antenna.

[0044] 5. In an antenna applied to a wind measuring radar of the present invention, a metasurface lens includes a plurality of metasurface units. Each metasurface unit serves as a phase modulation unit and can independently adjust the phase of an incident electromagnetic wave to achieve the required phase compensation design. Each unit is composed of four layers of dielectric plates and five layers of metal patches, and has a compact and centrally symmetrical structure.

[0045] 6. An antenna for wind radars employs a cutting process and a choke slot design, directing surface current along the perimeter of the slotted lines. This increases the equivalent current path of the antenna surface current, improving current distribution. This approach reduces the antenna's low-frequency operating point without changing its dimensions, reducing unnecessary edge radiation and ultimately increasing antenna gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the structure of a multi-beam switching antenna in the present invention;

[0047] Figure 2 This is a schematic structural diagram of a connecting device and a feeding device in a multi-beam switching antenna of the present invention;

[0048] Figure 3 Schematic diagram of the structure of a lens device in a multi-beam switching antenna of the present invention;

[0049] Figure 4Schematic diagram of the structure of a metasurface lens in a multi-beam switching antenna of the present invention;

[0050] Figure 5 A schematic diagram of the steps of a method for operating a multi-beam switching antenna in the present invention;

[0051] Figure 6 Schematic diagram of an application scenario of a multi-beam switching antenna in this embodiment;

[0052] Figure 7 Schematic diagram of the direction of the multi-beam switching antenna in this embodiment;

[0053] In the figure, 1 is a connecting device and a feeding device; 101 is an ultra-small push-in connector; 102 is a GCPW-SIW conversion structure; 103 is a choke slot structure; 2 is a lens device; 201 is a metal rectangular wire frame; 202 is a five-layer metal patch; and 203 is a four-layer dielectric board. DETAILED DESCRIPTION

[0054] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts should fall within the scope of protection of the present invention.

[0055] With the rapid development of science and technology, low-altitude wind measurement radars have demonstrated outstanding performance in the field of meteorological element detection and have gradually gained a foothold in the field of wind measurement. This radar system uses the backscattering effect of atmospheric turbulence on electromagnetic waves to accurately obtain atmospheric information. By transmitting electromagnetic beams in multiple directions to high altitudes (specifically the area above the boundary layer), receiving and processing these signals reflected back due to the uneven vertical structure of the atmosphere, and accurately measuring the Doppler velocity at various distances in different beam directions, and combining the Doppler velocity data at the same altitude under the condition of uniform horizontal distribution of the atmosphere, the wind measurement radar can calculate the three-dimensional wind field information of the atmosphere and achieve accurate detection of low-altitude wind fields.

[0056] Millimeter-wave wind radars offer unique advantages in detecting wind fields at low altitudes (<300m), which is required for wind farms. Antennas play a crucial role in radar systems and are crucial to overall radar performance. Wind radar antenna design must meet the requirements of high precision, high gain, and low sidelobes to ensure dense sampling points within the wind field, enhance detection sensitivity, and reduce clutter interference on echo signals, thereby improving detection accuracy. Therefore, research on multi-beam, high-gain antennas for wind radar applications is of great value.

[0057] In terms of antenna technology, wind measurement radars currently mainly use two types of antennas: phased array antennas and parabolic antennas. Although these two types of antennas can meet the technical requirements of wind measurement radars, the existing antennas have shortcomings such as fewer beams, too high profiles, and complex structures.

[0058] In summary, the antenna systems currently used in wind measurement radars are unable to meet the actual application requirements of wind measurement radar systems. To address this issue, the metasurface lens of this application uses metasurface units to control the propagation of electromagnetic waves, which is conducive to achieving sixteen-beam characteristics. The lower profile height not only reduces the reflection of electromagnetic waves and dielectric loss in the lens, but also makes the lens thinner and easier to manufacture. In addition, the wind measurement radar system equipped with a multi-beam switching antenna has more sampling points on each layer of the wind profile, thereby achieving its high-precision characteristics.

[0059] Example 1

[0060] In this embodiment, a multi-beam switching antenna is used, which includes: a connecting device, a feeding device and a lens device;

[0061] The connecting device is an ultra-small push-in connector, the input end of which is connected to the wind measuring radar, and the output end is connected to the feeding device; the connecting device is used to receive the microwave signal transmitted by the wind measuring radar and input the microwave signal into the feeding device;

[0062] The feeding device includes a GCPW-SIW conversion structure and a feed antenna; the feed antenna is a set of sixteen parallel Vivaldi antennas, which are fed by the SIW structure and radiate spherical waves to the lens device, and finally radiate electromagnetic waves into free space through the lens device;

[0063] The lens device is a metasurface lens, and the feeding device and the lens device adopt a defocusing arrangement; effective deflection of the fixed beam is achieved, ensuring that the electromagnetic wave can be accurately radiated into free space.

[0064] Thus, the spherical wave radiated by the feeding device located at the focus of the lens is phase compensated and converted into a plane wave at the output surface of the lens.

[0065] In this solution, the phase compensation characteristics of the metasurface lens are used to achieve beam deflection and gain enhancement. The beam deflection angles are different combinations of 5°, 10°, 15°, and 20° to cover a wide detection area.

[0066] In this solution, a Gilbert Push-On (GPO) connector is connected to the coaxial cable in the unified wind measurement radar to input the microwave signal output by the radar system's transmitting module into the antenna's feed structure.

[0067] In this scheme, the GCPW-SIW (grounded coplanar waveguide-substrate integrated waveguide) conversion structure is used to efficiently convert the electromagnetic waves fed by the coplanar waveguide into electromagnetic waves propagated by the substrate integrated waveguide, so as to reduce the feeding loss and improve the overall performance of the antenna system. The input end of the GCPW-SIW conversion structure is connected to the connection device, and the output end is connected to the feed antenna; the GCPW-SIW conversion structure includes a coplanar waveguide, a trapezoidal transition structure and a substrate integrated waveguide; wherein the trapezoidal transition structure is used to realize the quasi-TEM mode of the coplanar waveguide and the quasi-TE mode of the substrate integrated waveguide. 10 The radiating arm of the Vivaldi antenna is cut and provided with a choke slot structure. The inner and outer edges of the radiating arm of the Vivaldi antenna both satisfy the exponential gradient curve, and its specific expression is:

[0068] z=ae bx +g

[0069]

[0070] Where z is the exponential gradient curve satisfied by the inner and outer edges of the radiating arm of the Vivaldi antenna; a and g are gradient constants; (x1, z1) and (z2, z2) are the starting and ending coordinates of the gradient line, respectively.

[0071] The radiating arm of the Vivaldi antenna is cut into a blade-shaped radiating arm with a straight side length of 16.4 mm and a curve that satisfies the exponential equation z = 1.15e 5x +1.2, and a row of choke slot structures with a depth of 1.3mm and a width of 1mm are neatly added to the edge of the retained radiation arm of the antenna.

[0072] In this solution, the radiating layer of the parallel Vivaldi antenna is a double-layer radiating layer structure, including an upper radiating layer and a lower radiating layer, which are isolated and fixed by a dielectric substrate. The metasurface lens includes multiple periodically arranged metasurface units, each of which is composed of five metasurface layers, including four dielectric plates and five metal patches. The metal patches adopt a U-shaped structure, including a central rectangular patch and an outer metal rectangular wire frame. The outer metal rectangular wire frame is equivalent to an inductor, and the gap between the outer metal rectangular wire frame and the central rectangular patch is equivalent to a capacitor. The overall equivalent circuit model is a parallel LC resonator, forming a bandpass metasurface unit. The defocus arrangement is specifically as follows: the feed antenna is placed at a position deviated from the focus of the metasurface lens; sixteen parallel Vivaldi antennas are distributed on the focusing surface of the lens, corresponding to beam deflection angles of ±5°, ±10°, ±15°, and ±20°, respectively; the focusing surface of the lens is an arc surface with the center of the lens as the center and the focal length as the radius.

[0073] In this scheme, the metasurface lens phase modulates the electromagnetic waves from the feed antenna. Through a precisely designed phase gradient distribution, the electromagnetic waves are deflected and focused in a predetermined direction, thereby forming multiple independent and controllable detection beams. The metasurface unit on the lens uses five layers of metasurface to achieve 360° coverage; it is composed of four layers of dielectric plates and five layers of metal patches, with a compact and centrally symmetrical structure. The metasurface unit structure consists of multiple phase modulation units arranged periodically, each of which can independently adjust the phase of the incident electromagnetic wave to achieve the required phase compensation design.

[0074] The antenna has a beam switching mode. That is, this solution uses a single-pole four-throw RF switch (SP4T) in the RF link to select the deflection angle channel to be detected among the four deflection angle channels, and then selects the four rotationally symmetric beam direction channels of the same deflection angle in turn. In this way, polling detection of a total of sixteen beam directions at four deflection angles can be achieved.

[0075] The antenna in this solution is a wind measurement radar system with sixteen beams, providing sixteen sampling points on each horizontal sampling plane. These sampling points are uniformly spaced across the entire three-dimensional space. Compared to a four-beam antenna, this sixteen-beam antenna has 180 more sampling points, providing richer wind field information and further improving wind measurement accuracy. The metasurface lens antenna used in this solution not only achieves sixteen beams, but also achieves a gain of 30.8dBi and a sidelobe level below -20.1dB, providing more beams, higher gain, and reduced sidelobe levels.

[0076] The antenna structure diagram in this scheme is as follows Figure 1 As shown, it includes a connecting device and a feeding device 1 and a lens device 2, wherein the specific schematic diagram of a single connecting device and a feeding device 1 is as follows Figure 2 As shown, it includes an ultra-small push-in (GPO) connector 101, a GCPW-SIW conversion structure 102, and a choke slot structure 103. The radiating layer of the Vivaldi antenna shown in the figure is double-layered, and the stacked structure is divided into an upper radiating layer, a dielectric substrate, and a lower radiating layer. It has good dimensional stability in the millimeter wave frequency band and can effectively reduce the loss caused by coupled feeding. The designed antenna is connected to the coaxial cable through an ultra-small push-in connector 101, and a SIW-GCPW converter 102 is designed. The conversion structure is composed of GCPW, a trapezoidal transition structure, and SIW. The trapezoidal transition structure is used to realize the coplanar waveguide quasi-TEM mode and the substrate integrated waveguide quasi-TE 10 To convert between modes, a rectangular choke slot structure 103 is loaded on the edge of the antenna radiation arm and the radiation arm is cut, which can effectively reduce unnecessary edge radiation and thus improve performance.

[0077] For the radiating arm structure in the antenna, the exponential curve expressions of its inner and outer contours are:

[0078] z=0.26e 15x -0.26

[0079] z=1.15e 5x +1.2

[0080] The antenna's reflection coefficient is less than -10dB across the entire operating band. A single Vivaldi antenna has a gain of 15.3dBi, a sidelobe level less than -12.5dB, an E-plane half-power beamwidth of 24°, and an H-plane half-power beamwidth of 31°. The entire Vivaldi antenna is compatible with metasurface lens feeds, and multiple antennas can be deployed to achieve multi-beam characteristics.

[0081] A single metasurface unit in a metasurface lens is Figure 3 As shown, the metasurface is composed of four layers of dielectric plates 203 and five layers of metal patches 202, adopting a U-shaped metasurface unit design. A metal rectangular wireframe 201 is placed on the outside. The outer metal rectangular wireframe portion can be equivalent to an inductor, while the gap between the wireframe and the central rectangular patch can be equivalent to a capacitor. The overall equivalent circuit model is a parallel LC resonator, forming a bandpass metasurface unit. The dielectric plate is a 0.76mm thick PTFE copper-clad ZYF255DA laminate with a dielectric constant and loss tangent of 2.55 and 0.0018, respectively. The metal layer consists of rectangular patches and edge wireframes. This structure is compact and centrally symmetrical, with a thickness of 0.035mm.

[0082] According to the one-to-one correspondence between the transmission phase shift value of the metasurface unit and the length a of the rectangular patch, the geometric size of each unit can be obtained by calculating the vertical incidence compensation phase distribution obtained by the phase compensation formula. Figure 4 As shown in the figure, each square represents a metasurface unit, and the size of the rectangular patch corresponds to the phase value that needs to be compensated at the center of the unit. The entire lens is composed of 61 metasurface units, with an overall size of 220mm × 220mm × 3.2mm and a focal length of 260mm. The metasurface lens has a total of 3721 metasurface units.

[0083] Based on the above design of feed antenna and metasurface lens, the overall structure of sixteen-beam metasurface lens antenna is as follows: Figure 1 The Vivaldi feeds are placed at rotationally symmetrical positions along the center of the lens. The distance from the phase center of each feed to the center of the lens is f, which is the beam deflection angle corresponding to each feed. The sixteen Vivaldi feeds correspond to detection beam directions with deflection angles of ±20°, ±15°, ±10°, and ±5°, respectively. There are four rotationally symmetrically placed feeds in each deflection angle direction.

[0084] In this embodiment, when the wind measurement radar is working, the deflection angle channel to be detected in the four deflection angle channels is first selected through the single-pole four-throw radio frequency switch (SP4T) in the radio frequency link, and the beam switching control circuit is used to switch and control the excitation state of different feed sources to achieve beam switching. In this solution, the beam switching control circuit uses a signal processor as the control center, and switches the excitation state of different feed sources by controlling the on-off state of the switch array. When it is necessary to switch the beam, the signal processor sends a control signal to the switch array to excite the corresponding feed source, thereby generating the required beam. Then, the four rotationally symmetric beam direction channels of the same deflection angle are selected in turn, so that polling detection of a total of sixteen beam directions of the four deflection angles can be achieved.

[0085] Each Vivaldi antenna generates a linearly polarized wave. Since the feed antennas with the same deflection angle are rotationally symmetric about the central axis of the lens, the far-field pattern simulation results of the XOZ plane and the YOZ plane are exactly the same, and the beams with the same deflection angle are symmetric about the central axis. The feed positions numbered 1 to 4, 6 to 8, 9 to 12, and 13 to 16 correspond to beam deflection angles of ±5°, ±10°, ±15°, and ±20°, respectively. The simulation results of the far-field pattern are shown in Figure 2. Figure 7 As shown in the figure, the directional patterns of beams 1, 3, 5, 7, 9, 11, 13, and 15 are shown respectively, where pink is beam 1, orange is beam 3, yellow is beam 5, light green is beam 7, dark green is beam 9, light blue is beam 11, dark blue is beam 13, and purple is beam 15. It can be seen from the figure that this scheme achieves a gain of 30.8dBi, a sidelobe level lower than -21dB, and a half-power beamwidth of 3°, which can well meet the antenna performance requirements of the wind measurement radar.

[0086] Example 2

[0087] In this embodiment, a multi-beam switching antenna operation method is applied, and the steps of the method are as follows: Figure 5 As shown, specifically including:

[0088] S1, transmit the microwave signal generated by the wind measurement radar to the feeding device through the ultra-small push-in connector;

[0089] S2. In the feeding device, the microwave signal passes through the GCPW-SIW conversion structure to achieve the quasi-TEM mode of the coplanar waveguide and the quasi-TE mode of the substrate integrated waveguide. 10 Conversion between modes to provide feed for the feed antenna;

[0090] S3. Sixteen Vivaldi antennas radiate spherical waves toward the metasurface lens, which performs phase compensation on the spherical waves radiated by the feed antenna and converts them into plane waves at the lens exit surface. Through the defocus arrangement, multi-beam coverage with beam deflection angles of ±5°, ±10°, ±15°, and ±20° is achieved.

[0091] S4. The converted plane wave is emitted from the metasurface lens to form a high-gain, low-sidelobe beam, which is used for target detection and wind field measurement by wind radar.

[0092] A beam switching mode is adopted during the multi-beam coverage process. Specifically, a single-pole four-throw RF switch is first set in the RF link, and the deflection angle channel to be detected among the four deflection angle channels is selected. Then, the four rotationally symmetric beam direction channels of the same deflection angle are selected in turn, thereby realizing polling detection of a total of sixteen beam directions of the four deflection angles.

[0093] This working method is applied to the multi-beam switching antenna proposed in this application. The antenna structure integrates an ultra-small push-in connector, a GCPW-SIW conversion structure, a feed source, and a metasurface lens. The RF signal is transmitted to 16 Vivaldi antennas arranged in different positions via the GPO connector and the conversion structure. The 16 feed sources are then combined with the metasurface lens to achieve the radiation of multiple deflection direction beams of ±5°, ±10°, ±15°, and ±20°.

[0094] The multi-beam switching antenna connects to a coaxial cable via an ultra-small Gilbert Push-On (GPO) connector. The microwave signal is fed into a grounded coplanar waveguide (GCPW) before being fed into a substrate integrated waveguide (SIW) through a GCPW-to-SIW conversion structure. This feed structure provides excellent isolation, effectively reducing mutual interference between RF systems and further minimizing losses in the feed. The SIW feed structure is equivalent to a traditional rectangular waveguide, facilitating analysis of its transmission characteristics.

[0095] In order to connect with GPO interface, a SIW-GCPW converter is designed in this scheme. The conversion structure consists of GCPW, trapezoidal transition structure and SIW. The trapezoidal transition structure is used to realize the quasi-TEM mode of coplanar waveguide and the quasi-TE mode of substrate integrated waveguide. 10 Conversion between modes.

[0096] The inner and outer edges of the radiating arm of the Vivaldi antenna designed in this scheme are both exponential gradient curves, and the expression is:

[0097] z=ae bx+g

[0098] Where b is the gradient rate of the exponential line gradient absorption, a and g are constants determined by the following two equations:

[0099]

[0100] Where (x1, z1) and (x2, z2) are the starting and ending coordinates of the gradient line respectively.

[0101] The multi-beam characteristics of the lens antenna can be achieved through beam defocusing. The function of the metasurface lens is to phase compensate the spherical wave radiated by the feed source at the lens focus F and convert it into a plane wave at the lens output surface.

[0102] When the electromagnetic wave radiated by the vertically incident feed source leaves the lens focus F and reaches each lens unit along different transmission paths, in order to form an equiphase surface on the lens exit surface, the phase that needs to be compensated for each metasurface unit can be calculated by the following formula:

[0103] Ψ mn =-k(R mn -f)+2tπ

[0104] Among them, mn is the compensation phase of the m-th row and n-th column unit, k = 2π / λ is the free space propagation constant, is the propagation distance from the feed source to the m-th row and n-th column unit, f is the focal length of the lens, and t is a positive integer.

[0105] For the unit in the mth row and nth column of the metasurface lens, the focus of the lens is at point F, the offset feed position is F', R mn is the distance from the lens focus to the unit in the mth row and nth column, R′ mn is the distance from the defocused feed to the unit in the mth row and nth column, the distance from the normal incident feed to the center of the lens is the focal length of the lens f, and the spatial phase from the defocused feed to the unit in the mth row and nth column of the metasurface lens is Pr mn ; The compensation phase of the unit designed in the mth row and nth column is Pc mn ; The final phase of the unit in the mth row and nth column is Po mn . Then we have the following formula:

[0106] Pr mn =kR′ mn

[0107] PC mn =-k(R mn -f)+2tπ

[0108] Po mn =Pr mn +Pc mn

[0109] Where k = 2π / λ is the free space propagation constant. When placed at a point off-focus, the final phase of the metasurface unit is:

[0110] Po mn =Pr mn +Pc mn =kR′ mn +-k(R mn -f)+2tπ

[0111] Taking the center of the lens as the origin, the coordinates of the unit in the mth row and nth column are (x mn ,y mn , 0), then the phase difference between the unit and the origin is:

[0112]

[0113] From this we can get the emission direction (θ, )’s far-zone electric field amplitude is:

[0114]

[0115] Where M is the total number of rows of units constituting the metasurface lens, N is the total number of columns, and E0 is the electric field amplitude at the phase center of the feed antenna.

[0116] The feed is placed at a position offset from the focal point of the metasurface lens. The lens's focal plane is an arc centered at the lens center and with a radius equal to the focal length f. Feed antennas are placed at different locations on the focal plane to generate beams with different output directions. Sixteen feed positions are distributed on the lens's focal plane, corresponding to beam deflection angles of ±5°, ±10°, ±15°, and ±20°, respectively.

[0117] The metasurface unit in this scheme uses five layers of metasurface to achieve 360° coverage. It is composed of four layers of dielectric plates and five layers of metal patches. The metal rectangular wireframe part on the outside of the U-shaped metasurface unit can be equivalent to an inductor, and the gap between the wireframe and the central rectangular patch can be equivalent to a capacitor. The overall equivalent circuit model is a parallel LC (capacitor-inductor) resonator, forming a bandpass metasurface unit. The metal layer consists of rectangular patches and edge wireframes. This structure is compact and centrally symmetrical.

[0118] Based on the one-to-one correspondence between the transmission phase shift value of a metasurface unit and the length of the rectangular patch, the calculated normal-incidence compensation phase distribution can be used to determine the geometric dimensions of each unit. Each square represents a metasurface unit. Periodic master / slave boundaries and sequential excitation in ANSYS HFSS software are used to simulate antenna elements to determine the relationship between size and compensation phase. The phase shift of 0° is used as the reference phase point when a = 0.6 mm. As the rectangular patch length a increases from 0.6 mm to 2.5 mm, the transmission phase shift angle range covers the entire 360° period, and the phase shift angle changes approximately linearly. The size of the rectangular patch corresponds to the phase value to be compensated at the center of the unit. The lens is composed of 61 metasurface units, with an overall size of 220 mm × 220 mm × 3.2 mm and a focal length of 260 mm. The metasurface lens contains a total of 3721 metasurface units.

[0119] Example 3

[0120] In this embodiment, a wind measurement radar system is used. The application scenario of the system is as follows: Figure 6 As shown, the millimeter-wave wind measurement radar is located in a wind farm. The system includes a signal source, a transceiver module, a signal processor, and a multi-beam switching antenna applied to the wind measurement radar.

[0121] The signal source is used to emit a 24GHz millimeter-wave radio frequency signal, which is then transmitted to the transceiver module for amplification.

[0122] The transceiver module is used to amplify the radio frequency signal and is connected to the feed port of the antenna;

[0123] The signal processor includes a host computer and an FPGA module, and is used to process the received and transmitted radio frequency signals;

[0124] The antenna is used to generate beams that detect different directions to measure wind speed and direction.

[0125] The signal source provides a 24G millimeter-wave wind measurement radar signal and transmits it to the transceiver module. The transceiver module further amplifies it and feeds it to the antenna in this solution. The antenna is used to transmit and receive beams, and the processor is used to process the received antenna signal, including signal processing such as ranging and speed measurement.

[0126] In this embodiment, the multi-beam switching antenna structure used in the system for wind measurement radar is the same as that in Example 1, and its operating method is the same as that in Example 2. The multi-beam switching antenna uses a 16-beam metasurface lens antenna, and this 16-beam metasurface lens antenna is applied to a millimeter-wave wind measurement radar system to conduct wind measurement experiments.

[0127] The green bracket connecting the feed antenna is made of 8266 photocurable resin material, and the connecting joints and rectangular base are made of ABS engineering plastic (Acrylonitrile-Butadiene-Styrene, acrylonitrile-butadiene-styrene copolymer). Nylon hexagonal studs are used to connect the lens and the fixings. The lens consists of metasurface units printed on four layers of 0.76mm PTFE sheet (polytetrafluoroethylene sheet). Holes are punched around the dielectric substrate and locked with polyethylene screws. The PTFE sheet material is relatively hard, and the flatness of the lens surface is high, ensuring the good performance of the processed object. The RF connection line is connected to the feed antenna from the bottom of the lens, and the lens antenna is fixed as a whole on the white nylon bracket.

[0128] During the field wind measurement experiment, the plastic base of the metasurface lens antenna was fixed to the ground-based millimeter-wave wind radar housing using hexagonal copper posts. The antenna feed port was connected to the internal RF link via a coaxial cable passing through the housing. The aluminum plate on the upper surface of the housing was thickened to ensure the relative stability of the receiving and transmitting antennas. The test site was selected on an open lawn. The auxiliary power supply and laptop computer running the host computer program were placed 15 meters away from the wind radar to avoid interference from electromagnetic equipment, vehicles, and pedestrians. The temperature on the test day ranged from 15 to 23°C, with sunny to cloudy weather.

[0129] After the wind radar has been operating for a period of time, real-time wind data is obtained. Mathematical statistics show that 96.8% of the echoes have a signal-to-noise ratio greater than 5.1dB, indicating excellent echo quality. Sixteen wind field sampling points are located within the horizontal plane at fixed altitude levels, and fifteen range layers are sampled, for a total of 240 sampling points within the three-dimensional space.

[0130] Compared to traditional four-beam wind radars, sixteen-beam wind radars provide more sampling points for wind field detection, improving wind field detection accuracy. By combining wind speed and direction information measured at different deflection angles, more accurate wind field information can be obtained.

[0131] In summary, the antenna can generate detection beams in sixteen different directions, which can cover the horizontal plane at a fixed height to a greater extent, thereby meeting the practical application requirements of the wind measurement radar system and improving the detection accuracy of wind field data.

[0132] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A multi-beam switching antenna for wind measurement radar, characterized in that: The antenna comprises: a connecting device, a feeding device and a lens device; The connecting device is an ultra-small push-in connector, the input end of which is connected to the wind measuring radar, and the output end is connected to the feeding device; the connecting device is used to receive the microwave signal transmitted by the wind measuring radar and input the microwave signal into the feeding device; The feeding device includes a GCPW-SIW conversion structure and a feed antenna; the feed antenna is sixteen parallel Vivaldi antennas for radiating spherical waves to the lens device; The lens device is a metasurface lens, and the feeding device and the lens device are arranged in a defocused manner; thereby performing phase compensation on the spherical wave radiated by the feeding device located at the lens focus and converting it into a plane wave at the lens exit surface.

2. The multi-beam switching antenna for wind measurement radar according to claim 1, characterized in that: The input end of the GCPW-SIW conversion structure is connected to the connecting device, and the output end is connected to the feed antenna; the GCPW-SIW conversion structure includes a coplanar waveguide, a trapezoidal transition structure and a substrate integrated waveguide; wherein the trapezoidal transition structure is used to realize the quasi-TEM mode of the coplanar waveguide and the quasi-TE mode of the substrate integrated waveguide 10 Conversion between modes.

3. The multi-beam switching antenna for wind measurement radar according to claim 1, characterized in that: The radiating arm of the Vivaldi antenna is cut and provided with a choke slot structure. The inner and outer edges of the radiating arm of the Vivaldi antenna both satisfy an exponential gradient curve, and the specific expression thereof is: z=ae bx +g Where z is the exponential gradient curve satisfied by the inner and outer edges of the radiating arm of the Vivaldi antenna; a and g are gradient constants; (x1, z1) and (x2, z2) are the starting and ending coordinates of the gradient line, respectively.

4. The multi-beam switching antenna for wind measurement radar according to claim 3, characterized in that: The Vivaldi antenna has a double-layer radiation layer structure, including an upper radiation layer and a lower radiation layer, which are isolated and fixed by a dielectric substrate.

5. The multi-beam switching antenna for wind measurement radar according to claim 3, characterized in that: The cutting process is to cut the radiating arm into a blade shape, so that the straight side length of the radiating arm after cutting is 16.4 mm, and the curved side satisfies the exponential equation z=1.15e 5x +1.2; the choke slot structure is specifically n evenly arranged choke slots with a depth of 1.3 mm and a width of 1 mm on the straight side of the radiation arm.

6. The multi-beam switching antenna for wind measurement radar according to claim 1, characterized in that: The metasurface lens includes multiple periodically arranged metasurface units, each of which is composed of five layers of metasurface, including four layers of dielectric plates and five layers of metal patches; the metal patches adopt a U-shaped structure, including a central rectangular patch and an outer metal rectangular wire frame; wherein the outer metal rectangular wire frame is equivalent to an inductor, and the gap between the outer metal rectangular wire frame and the central rectangular patch is equivalent to a capacitor. The overall equivalent circuit model is a parallel LC resonator, forming a bandpass metasurface unit.

7. The multi-beam switching antenna for wind measurement radar according to claim 1, characterized in that: The defocus arrangement is specifically as follows: the feed antenna is placed at a position deviated from the focus of the metasurface lens; sixteen parallel Vivaldi antennas are distributed on the focusing surface of the lens, corresponding to different beam deflection angles; the focusing surface of the lens is an arc surface with the center of the lens as the center and the focal length as the radius.

8. A method for operating a multi-beam switching antenna for a wind measurement radar, characterized in that: The method is applied to the operation of a multi-beam switching antenna for a wind measurement radar as described in any one of claims 1 to 7, and the method comprises the following steps: S1, transmit the microwave signal generated by the wind measurement radar to the feeding device through the ultra-small push-in connector; S2. In the feeding device, the microwave signal passes through the GCPW-SIW conversion structure to achieve the quasi-TEM mode of the coplanar waveguide and the quasi-TE mode of the substrate integrated waveguide. 10 Conversion between modes to provide feed for the feed antenna; S3, sixteen Vivaldi antennas radiate spherical waves toward the metasurface lens, which performs phase compensation on the spherical waves radiated by the feed antennas, converting them into plane waves at the lens exit surface. Multi-beam coverage with different beam deflection angles is achieved through defocusing arrangement. S4. The converted plane wave is emitted from the metasurface lens to form a high-gain, low-sidelobe beam, which is used for target detection and wind field measurement by wind radar.

9. The method for operating a multi-beam switching antenna for a wind measurement radar according to claim 8, characterized in that: A beam switching mode is adopted in the multi-beam coverage process, specifically: first, a single-pole four-throw radio frequency switch is set in the radio frequency link, and the deflection angle channel to be detected in the four deflection angle channels is selected, and then the four rotationally symmetric beam direction channels of the same deflection angle are selected in turn, thereby realizing polling detection of a total of sixteen beam directions of the four deflection angles.

10. A wind measurement radar system, characterized in that: The system comprises a signal source, a transceiver module, a signal processor and a multi-beam switching antenna for a wind measurement radar as claimed in any one of claims 1 to 7; The signal source is used to emit a 24GHz millimeter wave radio frequency signal to be transmitted to the transceiver module for amplification; The transceiver module is used to amplify radio frequency signals and is connected to the feed port of the antenna; The signal processor includes a host computer and an FPGA module, and is used to process the radio frequency signals received and sent; The antenna is used to generate beams for detecting different directions to achieve measurement of wind speed and wind direction.

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