Circularly polarized folded cassegrain antenna

Abstract

The application provides a circularly polarized folded Cassegrain antenna, and relates to the technical field of antennas.The circularly polarized folded Cassegrain antenna comprises a handedness-selective focusing metasurface, an antenna layer and a polarization flipping metasurface, and the antenna layer is located between the handedness-selective focusing metasurface and the polarization flipping metasurface; the antenna layer is used for radiating right-handed circularly polarized electromagnetic waves and left-handed circularly polarized electromagnetic waves; the polarization flipping metasurface is used for flipping the handedness of the right-handed circularly polarized electromagnetic waves and the left-handed circularly polarized electromagnetic waves; and the handedness-selective focusing metasurface is used for total reflection of the right-handed circularly polarized electromagnetic waves, total transmission of the left-handed circularly polarized electromagnetic waves, and focusing of the left-handed circularly polarized electromagnetic waves; wherein the handedness-selective focusing metasurface is provided with a plurality of metasurface units arranged according to a phase compensation method, and each metasurface unit has a three-layer structure.

Description

Technical Field

[0001] This application relates to the field of antenna technology, and in particular to a circularly polarized folded Cassegrain antenna. Background Technology

[0002] Radar antenna systems have been gradually expanded from military aviation to have a wide range of applications, including navigation, aerospace, geological exploration, space exploration, and communications.

[0003] Reflector antennas, as one of the most commonly used radar antennas, have a relatively simple mechanical structure, are lighter than other horn antennas, possess good electrical performance, and exhibit high gain, high aperture efficiency, and no chromatic aberration. However, traditional reflector antennas suffer from a large focal-to-diameter ratio and occupy a large physical space, which restricts their further development and application. To overcome the problems of high focal-to-diameter ratio and large physical space, folded Cassegrain antennas have been proposed. However, existing folded Cassegrain reflector antennas are generally designed for linear polarization. Even with the existence of some circularly polarized folded Cassegrain antennas, the radiation polarization direction cannot be kept consistent with the excitation source direction, regardless of whether it is a linearly polarized or circularly polarized Cassegrain antenna. Summary of the Invention

[0004] In view of this, the purpose of this application is to propose a circularly polarized folded Cassegrain antenna, which can specifically solve the existing problems.

[0005] Based on the above objectives, in a first aspect, this application proposes a circularly polarized folded Cassegrain antenna, comprising: a rotation-selective focusing metasurface, an antenna layer, and a polarization-reversing metasurface, wherein the antenna layer is located between the rotation-selective focusing metasurface and the polarization-reversing metasurface; the antenna layer is used to radiate right-hand circularly polarized electromagnetic waves and left-hand circularly polarized electromagnetic waves; the polarization-reversing metasurface is used to reverse the rotation direction of the right-hand circularly polarized electromagnetic waves and the left-hand circularly polarized electromagnetic waves; the rotation-selective focusing metasurface is used to perform total reflection of the right-hand circularly polarized electromagnetic waves, total transmission of the left-hand circularly polarized electromagnetic waves, and focusing of the left-hand circularly polarized electromagnetic waves; wherein the rotation-selective focusing metasurface is provided with multiple metasurface units arranged according to the phase compensation method, and each metasurface unit has a three-layer structure.

[0006] Optionally, the three-layer structure of the metasurface unit includes a first patch, an intermediate reflective layer, and a second patch arranged sequentially in a first direction. The first patch, the intermediate reflective layer, and the second patch are all metal layers. A dielectric plate is disposed between the first patch and the intermediate reflective layer, and between the intermediate reflective layer and the second patch. A connecting shaft is disposed at the center of the intermediate reflective layer. The connecting shaft passes through the dielectric plate, and the two ends of the connecting shaft are respectively connected to the first patch and the second patch. The connection point between the connecting shaft and the first patch and the second patch is located at a non-central position of the first patch and the second patch.

[0007] Optionally, the first patch and the second patch can rotate independently relative to the connecting shaft.

[0008] Optionally, the first patch and the second patch are circular metal sheets with openings, and the intermediate reflective layer is a square metal sheet, wherein the side length of the intermediate reflective layer is greater than the diameter of the first patch and the second patch.

[0009] Optionally, the first patch and the second patch are the same size, and the openings of the first patch and the second patch include a first opening and a third opening arranged symmetrically, and a second opening and a fourth opening arranged symmetrically; wherein the opening depths of the first opening and the third opening are the same, the opening depths of the second opening and the fourth opening are the same, and the opening depths of the first opening and the third opening are greater than the opening depths of the second opening and the fourth opening.

[0010] Optionally, the rotational selective focusing metasurface is provided with a plurality of metasurface units arranged according to the phase compensation method, including: calculating the compensation phase required at different positions of the rotational selective focusing metasurface according to the phase compensation formula; and placing a metasurface unit with the same compensation phase required at each position of the rotational selective focusing metasurface.

[0011] Optionally, the antenna layer includes: a circularly polarized initial excitation antenna and an impedance matching layer corresponding to the circularly polarized initial excitation antenna; the circularly polarized initial excitation antenna includes a ring microstrip line and four antenna patches connected to the ring microstrip line; the impedance matching layer includes four impedance arrays corresponding one-to-one with the four antenna patches.

[0012] Optionally, the distance between the rotation direction selection focusing metasurface and the polarization reversal metasurface is obtained according to the radiation angle of the right-hand circularly polarized electromagnetic wave or the left-hand circularly polarized electromagnetic wave.

[0013] In summary, the advantages of this application and the user experience it brings are as follows:

[0014] This embodiment provides a circularly polarized folded Cassegrain antenna, comprising a rotation-selective focusing metasurface, an antenna layer, and a polarization-reversing metasurface. The antenna layer is located between the rotation-selective focusing metasurface and the polarization-reversing metasurface. The antenna layer radiates right-hand circularly polarized electromagnetic waves and left-hand circularly polarized electromagnetic waves. The polarization-reversing metasurface reverses the rotation direction of the right-hand and left-hand circularly polarized electromagnetic waves. The rotation-selective focusing metasurface performs total reflection of the right-hand circularly polarized electromagnetic waves, total transmission of the left-hand circularly polarized electromagnetic waves, and focusing of the left-hand circularly polarized electromagnetic waves. The rotation-selective focusing metasurface is provided with multiple metasurface units arranged according to the phase compensation method. Each metasurface unit has a three-layer structure, which can achieve transmission and reflection adjustment of the excitation source, focus the left-hand circularly polarized electromagnetic waves, increase the equivalent aperture of the antenna, achieve high antenna gain, and maintain the radiation polarization rotation direction consistent with the excitation source rotation direction. Attached Figure Description

[0015] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0016] Figure 1 This diagram shows the structure of the circularly polarized folded Cassegrain antenna of this application;

[0017] Figure 2 A schematic diagram of a metasurface unit structure of a rotation-selective focusing metasurface according to an embodiment of this application is shown.

[0018] Figure 3 This diagram illustrates the structure of an antenna layer according to an embodiment of this application.

[0019] Figure 4 This diagram illustrates the principle of a folded Cassegrain antenna with circular polarization rotational retention according to an embodiment of this application.

[0020] Figure 5 The diagram shows the compensated phase distribution and the actual structure of the spin-selective focusing metasurface according to an embodiment of this application.

[0021] Figure 6 Antenna S-parameter curves, VSWR curves, and radiation pattern curves provided for embodiments of the present invention;

[0022] Figure 7 The S-parameter curves and phase curves of the rotation-selective focusing metasurface unit structure provided in the embodiments of the present invention;

[0023] Figure 8The S-parameter curves, VSWR curves, and radiation pattern curves of the circularly polarized, rotationally maintained folded Cassegrain antenna provided in this embodiment of the invention. Detailed Implementation

[0024] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] Figure 1 This diagram illustrates the structure of a circularly polarized folded Cassegrain antenna according to this application.

[0027] refer to Figure 1 The circularly polarized folded Cassegrain antenna includes: a rotation-selective focusing metasurface 101, an antenna layer 102, and a polarization-reversing metasurface 103. The antenna layer 102 is located between the rotation-selective focusing metasurface 101 and the polarization-reversing metasurface 103. The antenna layer 102 radiates right-hand circularly polarized electromagnetic waves and left-hand circularly polarized electromagnetic waves. The polarization-reversing metasurface 103 reverses the rotation directions of the right-hand and left-hand circularly polarized electromagnetic waves. The rotation-selective focusing metasurface 101 performs total reflection of right-hand circularly polarized electromagnetic waves and total transmission of left-hand circularly polarized electromagnetic waves, thereby achieving transmission and reflection adjustment of the excitation source, increasing the equivalent aperture of the antenna, achieving high antenna gain, and maintaining consistency between the radiation polarization direction and the excitation source rotation direction. Furthermore, the rotation-selective focusing metasurface 101 can also focus left-hand circularly polarized electromagnetic waves.

[0028] In this embodiment, reference Figure 2 The rotation-selective focusing metasurface 101 is provided with multiple metasurface units 200 arranged according to the phase compensation method, and each metasurface unit 200 has a three-layer structure.

[0029] For example, a rotation-selective metasurface has m*n metasurface elements 200, where m and n are the number of metasurface elements 200 along the x and y directions, respectively, and the period of the metasurface element 200 is Pt, that is, the side length of the metasurface element 200 is Pt.

[0030] Figure 2 (a) shows a schematic diagram of the overall structure of the metasurface unit in this embodiment; Figure 2 (b) shows a schematic diagram of the exploded structure of the metasurface unit in this embodiment.

[0031] refer to Figure 2 (a) and Figure 2 (b) In this embodiment, each metasurface unit 200 has a three-layer structure including a first patch 201, an intermediate reflective layer 202, and a second patch 203 arranged sequentially in a first direction. The first patch 201, the intermediate reflective layer 202, and the second patch 203 are all metal layers, which can achieve total reflection of right-hand circularly polarized electromagnetic waves. A dielectric plate 204 is provided between the first patch 201 and the intermediate reflective layer 202, and between the intermediate reflective layer 202 and the second patch 203. A connecting shaft 205 is provided at the center of the intermediate reflective layer 202. The connecting shaft 205 passes through the dielectric plate, and the two ends of the connecting shaft 205 are respectively connected to the first patch 201 and the second patch 203, thereby realizing the rotation of the first patch 201 and the second patch 203. The connection point between the connecting shaft 205 and the first patch 201 and the second patch 203 is located at a non-central position of the first patch 201 and the second patch 203.

[0032] In this embodiment, the first patch 201 and the second patch 203 can rotate independently relative to the connecting shaft 205. The rotation angles can be represented by β and α, respectively. By adjusting the values ​​of β and α, the phase of the reflected right-hand circularly polarized electromagnetic wave and the transmitted left-hand circularly polarized electromagnetic wave can be independently controlled by 360 degrees within a preset range.

[0033] That is, in this embodiment, the reflection phase of the right-hand circularly polarized electromagnetic wave and the transmission phase of the left-hand circularly polarized electromagnetic wave are independently controlled by the rotation angles β and α of the first patch 201 and the second patch 203, respectively. (Refer to...) Figure 7 (b) and (d) respectively show the reflection phase of a circularly polarized electromagnetic wave and the transmission phase of a left-handed circularly polarized electromagnetic wave when only the β angle is rotated. Figure 7 The cases are given for β as 0°, 30°, and 60°. Figure 7 (a) The horizontal axis represents frequency, and the vertical axis represents reflection coefficient. Figure 7 (b) The horizontal axis represents frequency, and the vertical axis represents phase. Figure 7 (c) The horizontal axis represents frequency, and the vertical axis represents transmission coefficient. Figure 7 (d) The horizontal axis represents frequency, and the vertical axis represents phase. Figure 7 (b) shows that if only the β angle is rotated, the right-hand circularly polarized electromagnetic wave remains in phase with the same polarized reflected electromagnetic wave. Figure 7 (d) shows that by rotating the circular patch on the upper surface by an angle β, the transmission phase of the left-hand circularly polarized electromagnetic wave can be controlled by the angle β. Similarly, the metasurface unit 200 of this embodiment can achieve 360° phase modulation in the range of 8.4-9.8 GHz.

[0034] In this embodiment, as Figure 2As shown, since the center points of the first patch 201 and the second patch 203 do not coincide with the center point (the axis of the connecting shaft) of the metasurface unit 200, this metasurface unit 200 has different electromagnetic responses to electromagnetic waves with different circular polarizations. When the incident electromagnetic wave is a right-hand circularly polarized electromagnetic wave, it exhibits reflection; when the incident electromagnetic wave is a left-hand circularly polarized electromagnetic wave, it exhibits transmission.

[0035] Figure 4 This diagram illustrates the principle of a folded Cassegrain antenna with circular polarization rotational retention according to an embodiment of this application. Figure 4 The electromagnetic properties of the metasurface unit are described when a circularly polarized electromagnetic wave is incident along the +z direction. The radiation wave emitted by the equivalent excitation source is incident from the focal point between the rotation-selective focusing metasurface and the polarization-reversing metasurface, and the propagation path is O→A→B→C before radiating outwards.

[0036] To ensure that the electromagnetic waves radiated by the antenna are highly directional circularly polarized radiation, the distance between the rotational direction-selective focusing metasurface 101 and the polarization-reversing metasurface 103 is obtained based on the radiation angle of the right-hand circularly polarized electromagnetic wave or the left-hand circularly polarized electromagnetic wave. Specifically, it is obtained according to the formula H = OA * sin(θ), where H is the distance between the rotational direction-selective focusing metasurface 101 and the polarization-reversing metasurface 103, OA is the transmission path length of the electromagnetic wave between the rotational direction-selective focusing metasurface 101 and the polarization-reversing metasurface 103, and θ is the angle of the radiation wave emitted by the equivalent excitation source, that is, the radiation angle of the right-hand circularly polarized electromagnetic wave or the left-hand circularly polarized electromagnetic wave. Preferably, in this embodiment, the distance between the rotational direction-selective focusing metasurface 101 and the polarization-reversing metasurface 103 is one-third of the focal length.

[0037] Figure 7 (a) represents the same-polarization reflection coefficient when a right-hand circularly polarized electromagnetic wave is incident. Its reflection coefficient is greater than -3dB in the frequency range of 8.6-9.8GHz, and at 9.1GHz, its reflection coefficient is 0dB, indicating that it exhibits total internal reflection of right-hand circularly polarized electromagnetic waves. Conversely, Figure 7 (c) represents the transmission coefficient when a left-hand circularly polarized electromagnetic wave is incident. Within the 8.6-9.8 GHz frequency band, its cross-polarization transmission coefficient is greater than -3 dB, and at the same frequency point of 9.1 GHz, it achieves almost 0 dB transmission, meaning that the left-hand circularly polarized wave is almost completely transmitted. Therefore, the metasurface unit 200 structure of this embodiment can effectively reflect right-hand circularly polarized waves and transmit left-hand circularly polarized waves, achieving cross-polarization transmission.

[0038] Figure 2(c) shows a planar structural schematic diagram of some devices of the metasurface unit in this embodiment. In this embodiment, the first patch 201 and the second patch 203 are circular metal sheets with openings, and the middle reflective layer 202 is a square metal sheet. The side length of the middle reflective layer 202 is greater than the diameter of the first patch 201 and the second patch 203.

[0039] In this embodiment, the first patch 201 and the second patch 203 are the same size, and the openings of the first patch 201 and the second patch 203 include a symmetrically arranged first opening and a third opening, as well as a symmetrically arranged second opening and a fourth opening; wherein the opening depths of the first opening and the third opening are the same, the opening depths of the second opening and the fourth opening are the same, and the opening depths of the first opening and the third opening are greater than the opening depths of the second opening and the fourth opening. Through the optimization of the first, second, third, and fourth openings, the reflectivity of right-hand circularly polarized electromagnetic waves and the transmittance of left-hand circularly polarized electromagnetic waves are simultaneously optimized within the same frequency band.

[0040] In this embodiment, the rotational selection focusing metasurface 101 is provided with multiple metasurface units 200 arranged according to the phase compensation method, which can realize the focusing function.

[0041] Specifically, this includes calculating the required compensation phase at different positions of the rotational selective focusing metasurface 101 according to the phase compensation formula, and placing a metasurface unit 200 with the same compensation phase required at each position of the rotational selective focusing metasurface 101.

[0042] In this embodiment, the phase compensation formula φ(x,y) is:

[0043]

[0044] Where φ(x,y) represents the compensation phase required to achieve electromagnetic wave focusing, (x,y) represents the relative position of the metasurface unit 200, λ0 is the wavelength at the operating frequency f0, and O i O r The focal length is given, and the phase φ(x,y) that needs to be compensated is closely related to the operating frequency f0.

[0045] The required compensation phase at different positions of the rotation-selective focusing metasurface 101 is calculated according to formula (1). Metasurface units 200 with the same transmission phase at the corresponding positions are then arranged to achieve the arrangement of the metasurface units 200 of the rotation-selective focusing metasurface 101. For example, the following is obtained: Figure 5 (b) shows a metasurface unit 200 consisting of a 20×20 layer. Figure 5 The required phase compensation distribution for a focusing metasurface under left-handed circularly polarized wave incidence is presented. From Figure 5As we can clearly see in (a), the rotation-selective focusing metasurface 101 can achieve focusing when a left-handed circularly polarized wave is incident perpendicularly.

[0046] Figure 3 (a) shows a schematic diagram of the overall structure of the antenna layer in this embodiment; Figure 3 (b) shows an exploded structural diagram of the antenna layer in this embodiment; Figure 3 (c) A planar schematic diagram of the impedance matching layer in this embodiment is shown; Figure 3 (d) shows a schematic diagram of the structure of the circularly polarized initial excitation antenna in this embodiment.

[0047] The antenna layer 102 in this embodiment includes: a circularly polarized initial excitation antenna 302 and an impedance matching layer 301 corresponding to the circularly polarized initial excitation antenna 302; the patch of the circularly polarized initial excitation antenna 302 includes a ring microstrip line 304 and four antenna patches 303 connected to the ring microstrip line, and the impedance matching layer 301 includes four impedance arrays corresponding to the four antenna patches.

[0048] In one example, the impedance array may include several square, circular, or triangular metal sheets, etc. Taking a square metal sheet as an example, the periodic impedance period of the square metal sheet is p = 4.9 mm, the side length of the square metal sheet is a = 4.5 mm, and the periodic impedance layer has a gap of 5 mm between the four patch arrays.

[0049] Figure 6 The parameters of antenna layer 102 are S11, VSWR, and radiation pattern curves. Figure 6 In (a), the horizontal axis represents frequency, and the vertical axis represents antenna radiation efficiency. Figure 6 As can be seen from the S11 parameter in (a), S11 is less than -12dB in the 8.4-9.8GHz range, indicating that the antenna has high radiation efficiency; Figure 6 In (b), the horizontal axis represents frequency, and the vertical axis represents standing wave ratio. Figure 6 As can be seen from (b), the standing wave ratio is less than 2dB in the range of 8.4-9.8GHz, indicating that the antenna has a good standing wave ratio. Figure 6 In (c), the horizontal axis represents the radiation angle, and the vertical axis represents the antenna gain. Figure 6 As can be seen in (c), the antenna has good radiation characteristics at the 9.4 GHz frequency point, with a gain of 13 dB at 9.4 GHz.

[0050] In one example, the specific parameters of the circularly polarized folded Cassegrain antenna of this embodiment include:

[0051] The metasurface unit 200 has a number of 20*20 (m*n=20*20), a period of Pt=15mm, a dielectric substrate thickness of dt=1.524mm, a radius Rc=4.45mm for the first patch 201 and the second patch 203, and opening dimensions of the first patch 201 and the second patch 203 are la=2.3mm, lb=1mm, and w=0.5mm, respectively. The diameter of the connecting shaft is D=0.7mm, the impedance layer period is p=4.9mm, the side length of the square metal sheet is a=4.5mm, and the gap between the four patch arrays of the impedance layer is gap=5mm.

[0052] Figure 8 The S-parameter curves, VSWR curves, and radiation pattern curves of the circularly polarized, rotationally maintained folded Cassegrain antenna provided in this embodiment of the invention are shown.

[0053] Figure 8 (a) The S11 parameters of the Cassegrain antenna are less than -10dB in the azimuth range of 8.4-9.8GHz. Figure 8 (b) The VSWR (Average Standing Wave Ratio) of the Cassegrain antenna is less than 3 dB in the azimuth range of 8.4-9.8 GHz, indicating that the radiated electromagnetic wave spin is well maintained. Figure 8 (c) The antenna layout at the 9.4 GHz frequency point was selected, and through... Figure 8 (c) It can be clearly seen that the circularly polarized folded Cassegrain antenna of this embodiment can radiate a highly directional right-hand circularly polarized wave under the excitation of a right-hand circularly polarized wave, and has good radiation characteristics at f0, with a gain of 23dB.

[0054] This embodiment provides a circularly polarized folded Cassegrain antenna, comprising a rotation-selective focusing metasurface 101, an antenna layer 102, and a polarization-reversing metasurface 103. The antenna layer 102 is located between the rotation-selective focusing metasurface 101 and the polarization-reversing metasurface 103. The antenna layer 102 radiates right-hand circularly polarized electromagnetic waves and left-hand circularly polarized electromagnetic waves. The polarization-reversing metasurface 103 reverses the rotation direction of the right-hand circularly polarized electromagnetic waves and the left-hand circularly polarized electromagnetic waves. The rotation-selective focusing metasurface 101 is used for... The antenna is capable of total reflection of right-hand circularly polarized electromagnetic waves, total transmission of left-hand circularly polarized electromagnetic waves, and focusing of left-hand circularly polarized electromagnetic waves. The rotation direction selection and focusing metasurface 101 is provided with multiple metasurface units 200 arranged according to the phase compensation method. Each metasurface unit 200 has a three-layer structure, which can achieve transmission and reflection adjustment of the excitation source, focus of left-hand circularly polarized electromagnetic waves, increase the equivalent aperture of the antenna, achieve high antenna gain, and maintain the radiation polarization rotation direction consistent with the excitation source rotation direction.

[0055] It should be noted that:

[0056] The algorithms and displays provided herein are not inherently related to any particular computer, virtual system, or other device. Various general-purpose systems can also be used in conjunction with the teachings herein. The required structure for constructing such systems is apparent from the above description. Furthermore, this application is not directed to any particular programming language. It should be understood that the content of this application described herein can be implemented using various programming languages, and the above description of specific languages ​​is for the purpose of disclosing the best mode of implementation of this application.

[0057] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0058] Similarly, it should be understood that, in order to simplify this application and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of this application, various features of this application are sometimes grouped together into a single embodiment, figure, or description thereof. However, this method of disclosure should not be construed as reflecting an intention that the claimed application requires more features than are expressly recited in each claim. Rather, as reflected in the following claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of this application.

[0059] Those skilled in the art will understand that modules in the device of the embodiments can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiments can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components. Except where at least some of such features and / or processes or units are mutually exclusive, any combination can be used to combine all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or units of any method or device so disclosed. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose.

[0060] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0061] The various component embodiments of this application can be implemented in hardware, or as software modules running on one or more processors, or a combination thereof. Those skilled in the art will understand that microprocessors or digital signal processors (DSPs) can be used in practice to implement some or all of the functions of some or all of the components in the virtual machine creation system according to the embodiments of this application. This application can also be implemented as a device or system program (e.g., a computer program and computer program product) for performing part or all of the methods described herein. Such an implementation of this application can be stored on a computer-readable medium, or can be in the form of one or more signals. Such signals can be downloaded from an Internet website, provided on a carrier signal, or provided in any other form.

[0062] It should be noted that the above embodiments are illustrative of this application and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. This application can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several systems, several of these systems may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0063] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this application, and these should all be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A circularly polarized folded Cassegrain antenna, characterized in that, The circularly polarized folded Cassegrain antenna includes: a rotation-selective focusing metasurface, an antenna layer, and a polarization-reversing metasurface, wherein the antenna layer is located between the rotation-selective focusing metasurface and the polarization-reversing metasurface. The antenna layer is used to radiate right-hand circularly polarized electromagnetic waves and left-hand circularly polarized electromagnetic waves. The polarization-reversing metasurface is used to reverse the rotation direction of the right-hand circularly polarized electromagnetic wave and the left-hand circularly polarized electromagnetic wave. The rotation-selective focusing metasurface is used for total reflection of the right-hand circularly polarized electromagnetic wave, total transmission of the left-hand circularly polarized electromagnetic wave, and focusing of the left-hand circularly polarized electromagnetic wave; wherein, the rotation-selective focusing metasurface is provided with multiple metasurface units arranged according to the phase compensation method, and each metasurface unit has a three-layer structure. The three-layer structure of the metasurface unit includes a first patch, an intermediate reflective layer and a second patch arranged sequentially in a first direction. The first patch and the second patch are the same size, and the openings of the first patch and the second patch include a first opening and a third opening arranged symmetrically, as well as a second opening and a fourth opening arranged symmetrically. The first and third openings have the same opening depth, the second and fourth openings have the same opening depth, and the opening depth of the first and third openings is greater than the opening depth of the second and fourth openings.

2. The circularly polarized folded Cassegrain antenna according to claim 1, characterized in that, The first patch, the intermediate reflective layer, and the second patch are all metal layers; A dielectric plate is disposed between the first patch and the intermediate reflective layer, and between the intermediate reflective layer and the second patch. A connecting shaft is disposed at the center of the intermediate reflective layer. The connecting shaft passes through the dielectric plate, and the two ends of the connecting shaft are respectively connected to the first patch and the second patch. The connection point between the connecting shaft and the first patch and the second patch is located at a non-central position of the first patch and the second patch.

3. The circularly polarized folded Cassegrain antenna according to claim 2, characterized in that, The first patch and the second patch can rotate independently relative to the connecting shaft.

4. The circularly polarized folded Cassegrain antenna according to claim 2, characterized in that, The first patch and the second patch are circular metal sheets with openings, and the intermediate reflective layer is a square metal sheet with a side length greater than the diameter of the first patch and the second patch.

5. The circularly polarized folded Cassegrain antenna according to claim 1, characterized in that, The rotation-selective focusing metasurface is provided with multiple metasurface units arranged according to the phase compensation method, including: The required compensation phase at different positions of the rotation-selective focusing metasurface is calculated based on the phase compensation formula. At each position of the rotation-selective focusing metasurface, place a metasurface unit with the same compensation phase required for that position.

6. The circularly polarized folded Cassegrain antenna according to claim 1, characterized in that, The antenna layer includes: a circularly polarized initial excitation antenna and an impedance matching layer corresponding to the circularly polarized initial excitation antenna; The circularly polarized initial excitation antenna includes a loop microstrip line and four antenna patches connected to the loop microstrip line. The impedance matching layer includes four impedance arrays that correspond one-to-one with the four antenna patches.

7. The circularly polarized folded Cassegrain antenna according to claim 1, characterized in that, The distance between the rotation-selective focusing metasurface and the polarization-reversing metasurface is obtained based on the radiation angle of the right-hand circularly polarized electromagnetic wave or the left-hand circularly polarized electromagnetic wave.

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