A high-gain, multi-beam holographic metasurface antenna

Abstract

This invention discloses a high-gain, multi-beam holographic metasurface antenna, belonging to the field of antenna technology. The antenna includes a feed antenna array, a scalar holographic impedance modulation surface, a phase correction surface, and an external feed switching circuit. The feed antenna array is a novel octet top-hat monopole Yagi antenna array, containing four feeds to provide directional surface wave excitation to the scalar holographic impedance modulation surface in four directions. Above the scalar holographic impedance modulation surface, the phase correction surface elements are arranged accordingly to correct the near-field aperture phase of the beam, thereby further improving the beam gain and its directivity. This antenna has four independently adjustable and switchable high-gain beams. By adding an external feed switching circuit, single-beam switching and single-beam-to-multi-beam switching can be flexibly achieved. Each beam has a corresponding input (output) channel, which can meet the needs of the rapid growth in satellite communication capacity and the development of multi-target area communication in modern times.

Description

Technical Field

[0001] This invention relates to the field of antenna engineering technology, and specifically to a high-gain, multi-beam holographic metasurface antenna. Background Technology

[0002] Novel artificial electromagnetic materials, also known as electromagnetic metamaterials, are an emerging technology that uses periodically arranged sub-unit structures to control electromagnetic waves. Metasurfaces, as two-dimensional planar electromagnetic metamaterials, have found wide application due to their extremely low profile and ease of fabrication. Furthermore, with the introduction of the generalized Snell's law, the ability to arbitrarily control beams using phase discontinuities has become more practical, bringing new methods and ideas to the design of electromagnetic microwave devices.

[0003] Multi-beam antennas can significantly extend the coverage area of ​​a beam and provide service to multiple users simultaneously. Compared to digital or hybrid multi-beam technologies, passive multi-beam antennas offer advantages such as lower manufacturing costs and lower power consumption. While passive multi-beam antennas based on lenses, transmission arrays, reflected rays, and beamforming circuits exist, holographic modulated metasurfaces, due to their very low profile and ease of fabrication, are a promising candidate material for passive multi-beam antennas. By altering the surface impedance distribution based on the principles of optical holography, they can achieve multi-beam, multi-polarization, and electromagnetic stealth capabilities. However, to date, although holographic modulated metasurface antennas can achieve high gain and relatively free beam control, their fixed structure limits performance improvements to optimizing feed positions and holographic patterns—a complex process that has limited the potential for significant performance breakthroughs.

[0004] Near-field phase correction technology provides a practical solution for further improving the performance of holographic modulated metasurface antennas. By rationally arranging the transmission phase of the metasurface elements, the electric field phase of any plane in the near field can be designed and corrected. By adding a metasurface layer, significant improvements in antenna gain, aperture efficiency, directivity, and beamforming are achieved with only a slight increase in antenna profile. In summary, the high-gain, multi-beam holographic structure metasurface antenna with improved performance through the addition of a phase correction surface is simple in structure, easy to manufacture, and has a low profile. It provides a new method for improving the performance of traditional holographic modulated metasurface antennas and has great engineering practical significance. Summary of the Invention

[0005] Objective of the Invention: To overcome the shortcomings of existing technologies, this invention provides a high-gain, multi-beam holographic metasurface antenna. The addition of a phase correction surface aims to provide a new method for improving the performance of traditional holographic modulation metasurface antennas, solving the problem that the performance of existing traditional holographic modulation metasurface antennas is greatly limited by their own structure.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a high-gain, multi-beam holographic metasurface antenna, comprising: a feed antenna array, a scalar holographic impedance modulation surface, a phase correction surface, and an external feed switching circuit.

[0007] The feed antenna array of the present invention is an octet top-cap monopole Yagi antenna array set at the center of the scalar holographic impedance modulation surface. It includes four feed sources and uses SMA to feed the top-cap folded monopole to provide directional surface wave excitation in four directions for the scalar holographic impedance modulation surface.

[0008] As a further description of the present invention, the above-described octet cap monopole Yagi antenna array consists of four " The array consists of a "U"-shaped short-circuited top-cap monopole and four "T"-shaped top-cap folded monopoles. The four short-circuited top-cap monopoles are located at the apex of the "U" shape, and the top-cap folded monopoles are located on one side of the four short-circuited top-cap monopoles. They are rotated 90° to form an octet top-cap monopole Yagi antenna array. The four short-circuited top-cap monopoles are coupled to any one of the top-cap folded monopoles to form a quintet top-cap monopole Yagi antenna. The top-cap folded monopoles are fed using SMA (Surface Mount Multi-Aspect Ratio) to radiate cylindrical waves in a specified direction, providing a reference surface wave excitation for a quarter-scalar holographic impedance modulation surface.

[0009] The advantages of using the aforementioned octet top-cap monopole Yagi antenna array are that it allows for the selection of directional surface wave radiation in different directions by choosing different excitation feed antennas, which is beneficial for multi-beam radiation switching. Furthermore, the aforementioned pentetet top-cap monopole Yagi antenna has a lower profile compared to traditional monopole antennas, which is conducive to achieving a low profile overall structure.

[0010] The scalar holographic impedance modulation surface of the present invention is realized by arranging scalar holographic impedance modulation surface units according to a calculated holographic pattern.

[0011] As a further description of the present invention, the above-mentioned scalar holographic impedance modulation surface unit is composed of a square metal patch and a metal ground plane. By changing the geometric parameters of the square metal patch, its corresponding scalar surface impedance is obtained, and then the mapping relationship between the scalar surface impedance and the geometric parameters of the square metal patch is calculated.

[0012] Furthermore, a suitable surface impedance distribution function is constructed to obtain the required surface impedance value at each point on the scalar holographic impedance modulation surface.

[0013] Furthermore, based on the mapping relationship between surface impedance and the geometric parameters of the square metal patch, the arrangement of the metal patch on the entire scalar holographic impedance modulation surface is obtained.

[0014] The phase correction surface unit of this invention consists of three layers, each composed of square metal patches. The upper and lower patches are the same size. By adjusting the dimensions of the middle patch and the upper and lower patches, fifteen basic unit structures are obtained, corresponding to fifteen transmission phases: 69 degrees, 91.5 degrees, 114 degrees, 136.5 degrees, 159 degrees, -178.5 degrees, -156 degrees, -133.5 degrees, -111 degrees, -88.5 degrees, -66 degrees, -21 degrees, 1.5 degrees, 24 degrees, and 46.5 degrees. The transmission amplitude of each of the fifteen basic unit structures must be maintained above 0.9.

[0015] Furthermore, based on the extracted aperture field near-field phase of the scalar holographic impedance modulation surface, the required compensation near-field phase is calculated, and the arrangement of the corresponding phase correction surface structure is obtained.

[0016] In the external feed switching circuit of the present invention, the switching circuit is connected to the feed antenna array, and the excitation of the feed antenna array is controlled by the switching circuit. The switching circuit controls the antenna to switch between different single beams and switch between single beam and multi beam.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0018] 1. The feed antenna array section of this invention features a feed structure with a lower profile and smaller size, with a profile only 0.102 times the wavelength in vacuum. Traditional horn antennas and Vivaldi antennas result in large overall profiles and sizes; the height of traditional monopole feeds is typically a quarter wavelength. Compared to existing multi-beam holographic antenna feeds, the feed antenna array section of this invention has a more flexible control structure and a lower profile.

[0019] 2. The present invention relates to a double-layer dielectric phase correction surface in which there is no gap between the dielectric substrates, making the phase correction surface more compact. At the same time, due to the low profile of the feed antenna array, the gap between the holographic surface and the phase correction surface is smaller, so that the multi-beam holographic structure metasurface antenna after loading the phase correction surface still has a low profile.

[0020] 3. This invention features a high-gain, independently adjustable beam and a stable radiation pattern.

[0021] 4. The overall structure of this invention is simple, and all structures are composed of square patches. It can be manufactured using conventional printed circuit board technology in the microwave frequency band.

[0022] 5. The method proposed in this invention for improving the performance of traditional holographic modulation metasurface antennas is simple and ingenious in design. The integrated design of the feed antenna array and the scalar holographic impedance modulation surface provides the antenna with the ability to flexibly switch beams. This structure avoids the problem that multi-beam holographic metasurfaces manufactured by the traditional holographic interference superposition method cannot further extract and compensate the phase of the generated beam.

[0023] 6. The feed port of the feed antenna of the present invention is compactly designed. By adding an external feed switching circuit, different single-beam switching and single-beam-multi-beam switching can be flexibly realized, and the beams have a high degree of separation. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0025] Figure 1 This is a schematic diagram of the overall structure of the antenna part in an embodiment of the present invention, which includes three parts: a feed antenna array, a scalar holographic impedance modulation surface, and a phase correction surface.

[0026] Figure 2 This is a ray optical model diagram of a multi-beam holographic metasurface antenna with a loaded phase correction surface according to an embodiment of the present invention, wherein the electromagnetic wave distribution on the left and the electromagnetic wave transmission on the right are symmetrical structures.

[0027] Figure 3 This is a schematic diagram of the three-dimensional structure of the feed antenna array according to an embodiment of the present invention.

[0028] Figure 4 This is a top view of the feed antenna array according to an embodiment of the present invention.

[0029] Figure 5 This is a side view of the feed antenna array according to an embodiment of the present invention.

[0030] Figure 6 This is a schematic diagram of the scalar holographic impedance modulation surface unit structure according to an embodiment of the present invention.

[0031] Figure 7 This is a top view of the scalar holographic impedance modulation surface according to an embodiment of the present invention.

[0032] Figure 8 This is a schematic diagram of the phase correction surface unit structure according to an embodiment of the present invention.

[0033] Figure 9 This is a top view of the phase correction surface according to an embodiment of the present invention.

[0034] Figure 10 This is a schematic diagram of the external feed switching circuit according to an embodiment of the present invention.

[0035] Figure 11 The S-parameter curves of the feed antenna array and the multi-beam holographic metasurface antenna with / without a loaded phase correction surface, according to the embodiments of the present invention, are shown in HFSS simulation.

[0036] Figure 12 The XOZ plane pattern of the multi-beam holographic structure metasurface antenna with / without a loaded phase correction surface in this embodiment of the invention is shown in HFSS simulation at 12 GHz when excited by feed 1.

[0037] Figure 13 The XOZ plane pattern of the multi-beam holographic structure metasurface antenna with / without a loaded phase correction surface in this embodiment of the invention is shown in HFSS simulation at 12 GHz when simultaneously excited by feeds 1, 2, 3, and 4.

[0038] Figure 14 This is a basic step-by-step flowchart for designing a high-gain, multi-beam holographic metasurface antenna according to an embodiment of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0040] The antenna section of the embodiment is basically as follows Figure 1 As shown, this invention provides a high-gain, multi-beam holographic metasurface antenna, which includes two printed circuit boards with an air distance of approximately 0.4 wavelengths between them.

[0041] The printed circuit board at the bottom mainly consists of two parts: a feed antenna array and a scalar holographic impedance modulation surface. The feed antenna array is an octet top-cap monopole Yagi antenna array, and its overall structure is as follows: Figure 3 As shown, it consists of four short-circuited top-cap monopoles 6 as parasitic elements and four top-cap folded monopoles 7 as driving elements. The four short-circuited top-cap monopoles are located at the apex of the "mouth" shape, and the top-cap folded monopoles are located on one side of the four short-circuited top-cap monopoles. They are rotated 90° to form an octagonal top-cap monopole Yagi antenna array, arranged as shown in the diagram. Figure 4 As shown in the figure. Four short-circuited top-cap monopoles are coupled to any one of the top-cap folded monopoles to form a five-element top-cap monopole Yagi antenna. A side view of the five-element top-cap monopole Yagi antenna is shown below. Figure 5As shown, four short-circuited top-cap monopoles form feed 1 with the top-cap folded monopoles along the positive x-axis; feed 2 with the top-cap folded monopoles along the positive y-axis; feed 3 with the top-cap folded monopoles along the negative x-axis; and feed 4 with the top-cap folded monopoles along the negative y-axis. The top-cap folded monopoles are fed using SMAs through vias in the metal ground 4, enabling them to radiate cylindrical surface waves in a specified direction, providing a reference surface wave excitation for the quarter-scalar holographic impedance modulation surface.

[0042] Depend on Figure 6 The scalar holographic impedance modulation surface unit shown consists of a square metal patch and a metal ground plane. By changing the geometric parameters of the square metal patch, its corresponding scalar surface impedance is obtained, and then the mapping relationship between the scalar surface impedance and the geometric parameters of the square metal patch is calculated.

[0043] After clarifying the antenna's design specifications, including its operating frequency, polarization, main radiation direction, and antenna size, a reasonable holographic surface impedance modulation formula is constructed. Based on the required antenna size, gain, and other specifications, the scalar surface impedance is modulated to obtain the surface impedance distribution within the scalar holographic impedance modulation surface. Then, according to the mapping relationship between the surface impedance and the geometric parameters of the square metal patch, the arrangement of the metal patches on the entire scalar holographic impedance modulation surface is obtained. In this embodiment, the antenna operates at a frequency of 12 GHz, with linear polarization, and the main radiation directions (θ, φ) of the four beams are (30°, 0°), (30°, 90°), (30°, 180°), and (30°, 270°).

[0044] The holographic surface impedance modulation formula is as follows:

[0045]

[0046] Where, φ ref Represents the reference wave, φ obj Representing the target wave, Z s Let X represent the reactance at any point on the holographic surface, X represent the average reactance of the entire holographic surface, and M represent the modulation coefficient. Assuming the impedance-modulated surface lies in the XOY plane and the reference wave source is located at (x0, y0), we use a top-hat monopole Yagi antenna as the reference wave source to excite the holographic impedance-modulated surface. The reference wave can be expressed as:

[0047]

[0048] In the above formula, k0 represents the wave number in free space, n represents the effective refractive index of the modulation surface, and r represents the distance between any point on the holographic surface and the wave source point.

[0049] The target's emitted wave can be represented as:

[0050]

[0051] Substituting the expressions for the reference wave and the target emitted wave into the holographic surface impedance modulation formula, and based on the main radiation directions set by the four beams, the impedance information at any position on the corresponding holographic surface can be calculated. Through reasonable impedance modulation surface design, the complete impedance distribution characteristics can be constructed, and its element distribution is as follows: Figure 7 As shown.

[0052] Figure 2 This diagram illustrates the ray optical model of a multi-beam holographic metasurface antenna with a phase correction surface added, according to an embodiment of the present invention. It serves to explain in detail the near-field phase correction theory proposed in this embodiment. The scalar holographic impedance modulation surface generates leakage radiation after being excited by surface waves from the feed antenna. At a sufficiently close distance, each radiating patch on the scalar holographic impedance modulation surface can be considered as a sub-wave source, and its near-field aperture field phase distribution φ can be extracted at a distance h from the scalar holographic impedance modulation surface. in (x i , y i Essentially, this involves extracting the incident wave phase from each sub-wave source to the phase correction surface. If the beam direction emanating from the phase correction surface is (θ, φ), then the emitted phase is:

[0053]

[0054] according to Figure 2 It can be seen that if the transmission phase shift of the phase correction surface is φ PCS (x i , y i If the incident wave phase, the emitted wave phase, and the transmission phase shift of the phase correction surface are considered, then the relationship between them can be expressed as:

[0055]

[0056] Therefore, the above theory provides a new method to improve the performance of traditional holographic modulation metasurface antennas, but it imposes two requirements on the phase correction surface element: first, the transmission amplitude of all elements must be above 0.9; second, the transmission phase must be adjustable within 360°. The phase correction surface element in this embodiment utilizes... Figure 8The transmissive metasurface unit shown is used to achieve this. The upper and lower patches are the same size. By adjusting the size of the middle patch and the upper and lower patches, fifteen basic unit structures are obtained, corresponding to fifteen transmission phases of 69 degrees, 91.5 degrees, 114 degrees, 136.5 degrees, 159 degrees, -178.5 degrees, -156 degrees, -133.5 degrees, -111 degrees, -88.5 degrees, -66 degrees, -21 degrees, 1.5 degrees, 24 degrees, and 46.5 degrees, covering a discrete transmission phase control range of 340°. The transmission amplitude of all fifteen basic unit structures remains above 0.9. The phase shift φ transmitted from the phase correction surface is calculated. PCS (x i , y i Arrange the units to obtain the following: Figure 9 The phase correction surface is shown.

[0057] Figure 10 This is a schematic diagram of the external feed switching circuit according to an embodiment of the present invention. The switching circuit is connected to the feed antenna array, and the excitation of the feed antenna array is controlled by the switching circuit. Specifically, adjacent feeds are controlled by different switches. One end of a switching circuit is connected to the previous stage control circuit, and the other end controls different feed antennas. By controlling the switching of branch switches, one or more of the four feeds can be flexibly selected to be in the working state, while the remaining feeds are in the stopped state. Each branch switch is ultimately connected to the RF front end by a combiner switch, and the switching of the combiner switch controls the overall antenna's operating state. The switching of the switching circuit is controlled by an RF switching chip. To achieve interconnection between the switching circuit and the feed structure, a corresponding transition structure is required for conversion. The switching circuit is fabricated using substrate integration technology.

[0058] Figure 11 The figures show the S-parameter curves of the feed antenna array, the multi-beam holographic metasurface antenna, and the multi-beam holographic metasurface antenna with a phase correction surface, respectively, under HFSS simulation according to embodiments of the present invention. The operating bandwidth of the feed antenna array is observed to be 11.43-12.38 GHz (8%), the operating bandwidth of the multi-beam holographic metasurface antenna without a phase correction surface is 11.24-12.44 GHz (10.1%), and the operating bandwidth of the multi-beam holographic metasurface antenna with a phase correction surface is 11.21-12.71 GHz (12.5%).

[0059] Since, in the embodiments of the present invention, when feeders 1, 2, 3, and 4 are fed respectively, the resulting beams only change in the radiation direction, therefore... Figure 12The diagram shows only the XOZ plane radiation pattern of the multi-beam holographic metasurface antenna with and without a phase correction surface in an HFSS simulation at 12 GHz, using feed 1 for excitation according to an embodiment of the present invention. It can be observed that the main polarization direction is the set 30° direction. Without the phase correction surface, the main polarization gain in the 30° direction is 17.36 dBi, while with the phase correction surface, the main polarization gain is 19.43 dBi, an increase of 2.07 dBi, and the cross-polarization level is extremely low.

[0060] Figure 13 This is an example of the XOZ plane radiation pattern of a multi-beam holographic metasurface antenna with and without a phase correction surface in an HFSS simulation at 12 GHz, when simultaneously excited by feeds 1, 2, 3, and 4. It can be observed that the main polarization direction is the set 30° direction. Without the phase correction surface, the main polarization gain in the 30° direction is 14.36 dBi, while with the phase correction surface, the main polarization gain is 15.55 dBi, an increase of 1.2 dBi. The phase correction surface has a significant beamforming effect.

[0061] Figure 14 This is a basic step-by-step flowchart for designing a high-gain, multi-beam holographic metasurface antenna according to an embodiment of the present invention.

[0062] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. After reading the above content, various modifications and substitutions of the present invention will be obvious to those skilled in the art. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-gain, multi-beam holographic metasurface antenna, characterized in that, include: The device includes a feed antenna array, a scalar holographic impedance modulation surface, a phase correction surface, and an external feed switching circuit; it comprises two circular printed circuit boards, which are, from bottom to top, the first printed circuit board and the second printed circuit board; the first printed circuit board is a double-layer printed circuit board, comprising a dielectric substrate (1) and two metal layers, the dielectric substrate (1) of the first printed circuit board has a dielectric constant of 6.15, a loss tangent of 0.0025, and a dielectric thickness of 1.27mm, the dielectric substrate of the first printed circuit board is in the shape of a concentric ring, and the bottom surface is fully copper-clad (4). The first printed circuit board is a metal ground plane, the radius of which is the same as the outer ring radius of the dielectric substrate (1) of the first printed circuit board. The upper metal patch (3) of the first printed circuit board constitutes a scalar holographic impedance modulation surface, the overall arrangement of which is determined by the surface impedance of all impedance modulation surface units based on the holographic principle of the interferogram distribution. The reference wave corresponding to the interferogram distribution based on the holographic principle is the cylindrical surface wave generated by the feed antenna, and the target wave is the linearly polarized beam of directional radiation generated by the scalar holographic impedance modulation surface. The reference wave equation and the target wave equation are interferometrically calculated to obtain the interferogram distribution of the scalar holographic impedance modulation surface, which corresponds to the distribution of all impedance modulation surface units. The second printed circuit board is provided with the phase correction surface. The second printed circuit board is a three-layer printed circuit board, including two dielectric substrates (2) and three metal layers. The two dielectric substrates (2) have the same structural parameters, the dielectric constant is 2.2, the loss tangent is 0.0025, the dielectric thickness is 1.575mm, the metal is copper, and the size of the dielectric substrate is the same as the size of the dielectric substrate of the first printed circuit board. Consistent; the phase correction surface is composed of phase correction units, the uppermost metal structure is consistent with the lowermost metal structure, and changes simultaneously with the middle metal structure. The arrangement of the units is determined by the near-field discrete phase of the aperture field; the arrangement of the phase correction surface units is as follows: based on the near-field phase of the aperture field of the scalar holographic impedance modulation surface extracted by the field calculator, calculate the near-field aperture field phase that needs to be compensated to the target phase gradient if the aperture surface phase is compensated, and then discretize and quantize the near-field aperture field compensation phase to obtain the corresponding unit arrangement of the phase correction surface.

2. The high-gain, multi-beam holographic metasurface antenna according to claim 1, characterized in that: The feed antenna array consists of four "π-shaped" top-cap folded monopoles (7) and four "T-shaped" short-circuited top-cap monopoles (6), wherein the top-cap folded monopoles (7) serve as driving elements and the short-circuited top-cap monopoles (6) serve as parasitic elements, forming a novel octagonal top-cap monopole Yagi antenna array.

3. The high-gain, multi-beam holographic metasurface antenna according to claim 2, characterized in that: The eight-eight top-cap monopole Yagi antenna array is located within the concentric inner ring of the dielectric substrate of the first printed circuit board. The short-circuit pins of the four short-circuit top-cap monopoles (6) and the four top-cap folded monopoles (7) are soldered to the lower metal ground of the first printed circuit board. Holes are opened at the metal ground position below the feed pins of the four top-cap folded monopoles (7) to feed them.

4. A high-gain, multi-beam holographic metasurface antenna according to claim 3, characterized in that: The radius of the metal ground through hole below the feed pin of the top cap folded monopole (7) is slightly larger than the radius of the SMA inner core. The outer diameter of the SMA is welded to the metal ground, and the inner core passes through the metal ground through hole and is welded to the feed pin of the top cap folded monopole.

5. A high-gain, multi-beam holographic metasurface antenna according to claim 1, characterized in that: The aperture field near-field phase is essentially the leakage radiation generated when the scalar holographic impedance modulation surface is excited by the surface wave produced by the feed antenna. At a sufficiently close distance, each radiating patch on the scalar holographic impedance modulation surface can be regarded as a sub-wave source. The incident wave phase from each sub-wave source to the phase correction surface can be extracted using a field calculator at a distance h from the scalar holographic impedance modulation surface, where h is less than half the wavelength in vacuum, which is the aperture field near-field phase.

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