Three-waveband multifunctional antenna based on coding metasurface

Abstract

The invention discloses a three-band multifunctional antenna based on a coding metasurface, which comprises a feed source and a radiation structure for realizing a reflection function, the feed source is arranged above the radiation structure, the radiation structure comprises a layer of dielectric substrate, the top layer of the dielectric substrate is provided with 30 * 30 metal patch units which are arranged in an array, and the lower part of the dielectric substrate is provided with a metal grounding plate; the metal patch unit is composed of three groups of internal phase delay lines, middle phase delay lines and external phase delay lines which are in symmetrical patterns, and the three groups of internal phase delay lines, middle phase delay lines and external phase delay lines are in central symmetry, work in C, Ku and X wave bands respectively and can be applied to the directions of downlink and high-speed satellite communication and the like. And by adopting a coding metasurface mode, a multi-frequency multimode OAM multiplexing function and a beam regulation and control function are realized, and the method has important potential application value.

Description

Technical Field

[0001] The present invention belongs to the field of antennas in communication systems, and in particular to a three-band multifunctional antenna based on a coded metasurface. Background Art

[0002] Since the coding metamaterial was proposed in 2014, it has formed a very rich application in the digital control of electromagnetic waves, such as reflection, transmission and even full-space electromagnetic control, anisotropic metasurfaces, acoustic coding metasurfaces, etc., and the most noteworthy feature is the information characteristics of digital coding metasurfaces. The information of digital coding metasurfaces is concentrated in their coding patterns, and different coding patterns can produce different scattered electromagnetic fields. Therefore, the information analysis of the coding pattern is linked to the scattering characteristics of the coding metasurface. However, in actual use, the far-field radiation patterns generated by metasurface antennas with different codes are difficult to be fully received in practice, and a large amount of information is hidden in the side lobes and missed. Compared with traditional plane electromagnetic waves, vortex electromagnetic waves carrying orbital angular momentum (OAM) are a unique beam with a spiral phase structure and annular amplitude field. Due to the infinity of OAM modes and the orthogonality between different modes, a new degree of freedom independent of the time domain, frequency domain and polarization domain is provided. OAM waves have great potential in channel expansion and improving spectrum efficiency.

[0003] Although research on multi-band and multi-functional metasurfaces has yielded fruitful results, the combination of traditional beam steering functions and multi-band OAM multiplexing functions is still rare. In addition, the generation of multi-mode OAM beams in multiple bands by metasurfaces often requires a more complex structure, using two or more layers of dielectrics or patches with complex and easily damaged shapes, or using a more complex array than coded metasurfaces. Moreover, the multi-frequency OAM beam generation function of metasurfaces is mostly limited to higher frequency bands such as X, Ku, and Ka. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention provides a three-band multifunctional antenna device based on a coded metasurface, which can generate OAM vortex electromagnetic waves of different modes at 7GHz and 10GHz through a 2-bit coded metasurface unit, and realize beam steering function at 17GHz.

[0005] The technical solution of the present invention is as follows: A reflective metasurface device that generates dual-frequency OAM vortex waves based on coded metasurfaces and realizes high-frequency beam control, including a feed source and a radiation structure that realizes the reflection function. It is characterized in that the feed source is arranged above the radiation structure; the radiation structure includes: a layer of dielectric substrate and M×N metal patch units arranged in an array on the top layer, and a metal ground plane is arranged below the dielectric substrate; the metal patch units are configured as: composed of three groups of internal phase delay lines, middle phase delay lines, and external phase delay lines that are symmetric figures.

[0006] Preferably, the internal phase delay line is in the shape of a "+", with a fixed width of 0.4 mm, operating at 10 GHz, and changing the phase of the reflected electromagnetic wave by adjusting the length.

[0007] Preferably, the middle phase delay line and the internal phase delay line are combined into a "rice" shape, with a fixed width of 0.5 mm, operating at 17 GHz, and changing the phase of the reflected electromagnetic wave by adjusting the length.

[0008] Preferably, the external phase delay line and the internal phase delay line are combined into a "field" shape, with a fixed width of 0.5 mm, operating at 7 GHz, and changing the phase of the reflected electromagnetic wave by adjusting the length.

[0009] Preferably, the internal, middle, and external phase delay lines are all centrosymmetric and applicable to all-polarization electromagnetic waves.

[0010] Preferably, when electromagnetic waves are incident on the metasurface, by adjusting the corresponding parameters, the phase change of the reflected electromagnetic wave in the corresponding band can be controlled. When operating at 7 GHz, the lengths of the external phase delay lines are controlled to be 4.5, 5.3, 5.5, and 5.9, and the phase differences are all 90°, forming a 2-bit coded metasurface. Through phase compensation calculation and array arrangement, a first-order OAM beam is generated; when operating at 10 GHz, the lengths of the internal phase delay lines are controlled to be 4.11, 4.36, 4.49, and 4.93, and the phase differences are all 90°, forming a 2-bit coded metasurface. Through phase compensation calculation and array arrangement, a +2-order OAM beam is generated; when operating at 17 GHz, the lengths of the middle phase delay lines are controlled to be 1.8, 2.3, 3.3, and 3.9, and the phase differences are all 90°, forming a 2-bit coded metasurface, realizing the beam control function.

[0011] Preferably, the array shape formed by the arrangement of the metal patch units is square.

[0012] The present invention has the following advantages:

[0013] (1) The reflective metasurface achieves nearly 360° phase coverage in the 7, 10, and 17 frequency bands, and has a high reflection amplitude. The 2-bit coded metasurface is used to build a bridge between information science and physics, making it very convenient to arrange the array and facilitate the realization of functions.

[0014] (2) The reflective metasurface realizes multi-frequency OAM multiplexing, and is not limited to the Ku and Ka bands. It can also realize OAM beam generation in the C and X bands, and can be applied to fields such as satellite communications.

[0015] (3) The design of the reflective metasurface is flexible. It realizes OAM beam generation of l = +1 and l = +2 at 7 and 10 GHz, and beam steering at 17 GHz. The coupling between different bands is small, which can realize multi-band independent phase control of the reflected beam, and ensures that the various functions will not interfere with each other.

[0016] (4) The reflective metasurface has a simple structure, using only a single-layer dielectric substrate and a metal patch. The metal patch has a simple shape and is not easily damaged, making it easy to process and assemble, and has the advantage of a low profile. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a super surface unit of the present invention;

[0018] Figure 2 A schematic diagram of a reflective antenna array constructed according to the present invention;

[0019] Figure 3 It is the reflection phase diagram of the present invention when three parameters change according to 2-bit encoding at 7GHz;

[0020] Figure 4 This is a reflection phase diagram of the present invention when three parameters change according to 2-bit encoding at 10 GHz.

[0021] Figure 5 This is a reflection phase diagram of the present invention when three parameters change according to 2-bit encoding at 17 GHz.

[0022] Figure 6 (a) and (b) are the phase compensation amounts required for the metasurface units at each position to generate OAM beams at 7 and 10 GHz, respectively;

[0023] Figure 7 A schematic diagram of the present invention realizing the beam steering function at 17 GHz;

[0024] Figure 8 (a) and (b) are the far-field patterns of the OAM beams with l=+1 and l=+2 generated by the present invention, respectively;

[0025] Fig. 9 (a) and (b) are respectively the electric field intensity and phase distribution diagrams of the OAM beam with l=+1 generated at 7 GHz by the present invention;

[0026] Fig.10 (a) and (b) are respectively the electric field intensity and phase distribution diagrams of the OAM beam with l=+2 generated at 10 GHz by the present invention; DETAILED DESCRIPTION

[0027] The present invention will be described in further detail below in conjunction with the accompanying drawings.

[0028] Example

[0029] like Figure 1 , Figure 2 As shown, the present invention discloses a three-band multifunctional antenna based on a coded metasurface, including a feed source and a radiation structure for realizing a reflection function, wherein the feed source is arranged above the radiation structure, and the radiation structure includes a dielectric substrate, wherein M×N metal patch units arranged in an array are arranged on the top layer of the dielectric substrate, and a metal ground plane is arranged below, and the metal patch unit is composed of three groups of symmetrical figures of an internal phase delay line, a middle phase delay line, and an external phase delay line, which are all symmetrical about the center.

[0030] The three groups of phase delay lines work at different frequencies respectively. The internal phase delay line is in a "+" shape, and the width w1 is fixed at 0.4mm. When it works at 10GHz and the length l1 is 4.5, 5.3, 5.5, and 5.9, the phase difference is 90°, forming a 2-bit coded metasurface; the middle phase delay line is combined with the internal phase delay line to form a "Rice" shape, with a width w2 fixed at 0.5mm. When it works at 17GHz and the length l2 is 4.11, 4.36, 4.49, and 4.93, the phase difference is 90°, forming a 2-bit coded metasurface; the external phase delay line is combined with the internal phase delay line to form a "Field" shape, with a width w3 fixed at 0.5mm. When it works at 7GHz and the length l3 is 1.8, 2.3, 3.3, and 3.9, the phase difference is 90°, forming a 2-bit coded metasurface. The metal patch unit is printed on a TF-2 (εr=14) dielectric substrate with a thickness of h1=1.5mm and a period of 12mm. At 7GHz, the feed source is incident on the metasurface at θ=0, ψ=25° at a distance of 300mm from the center of the metasurface reflective array at its phase center, where θ and ψ represent the size of the pitch angle and azimuth angle, respectively. At 10GHz, the feed source is incident on the metasurface at θ=0, ψ=25° at a distance of 300mm from the center of the metasurface reflective array at its phase center, and at 17GHz, the feed source is placed vertically at a distance of 350mm from the metasurface reflective array at its phase center, and the incident metasurface is vertical. The length and width of the metasurface array are both 360mm.

[0031] The feed source can be a linearly polarized antenna type such as a microstrip antenna with low side lobe and low back lobe or a horn antenna.

[0032] The phase compensation amount required by the radiation unit is related to the position of the radiation unit on the upper surface of the dielectric substrate, and different phase compensations are calculated according to the generation of different modes of OAM vortex waves. The reflective super-surface OAM antenna of the present invention takes the center of the array as the coordinate origin, and the principle of generating OAM electromagnetic waves can be explained by the formula:

[0033] Where λ is the wavelength of the incident wave, d mn is the distance from the center of the array to the equivalent phase center of the feed source, and l is the mode number of the OAM vortex wave.

[0034] In this example, 30×30 radiation units are arranged periodically to form a multifunctional reflective metasurface, and the size of the metasurface is 360mm×360mm. First, the phase compensation required for the feed source incident on the metasurface with θ=0, ψ=25° at 7GHz and a phase center 300mm away from the center of the metasurface reflective array is calculated, and then the phase compensation required to generate the l=1 mode OAM beam is added, as follows: Figure 6 The same method can be used to calculate the phase compensation required to generate the l = +2 mode OAM beam at 10 GHz, as shown in (a). Figure 6 Finally, the internal structure, the middle structure and the external structure are arranged and combined to form a three-frequency multifunctional reflective metasurface, as shown in Figure 2 At 17GHz, the feed source is incident vertically, so we only need to calculate the phase compensation when θ=0, ψ=0, and then use the formula Where λ is the wavelength of the incident wave, Г is the period of the coding metasurface, and the phase compensation required to deflect the beam direction is added to obtain the desired beam steering result. At 7GHz, 10GHz, and 17GHz, the calculated phase compensation results are substituted into the algorithm code of the MATLAB software, and the corresponding 2-bit unit arrangement array is selected for simulation. Figure 8 (a) Figure 8 (b) The three-dimensional radiation pattern at the operating frequencies of 7 GHz and 10 GHz. It can be seen from the three-dimensional radiation pattern that the OAM vortex beams generated at 7 GHz and 10 GHz have obvious hollow features, that is, a zero intensity center caused by a phase singularity is generated. The maximum gains of l = +1 mode at 7 GHz and l = +2 mode at 10 GHz are 16.6 dBi and 19.8 dBi, respectively. Fig. 9 (a) and Fig. 9 (b) The electric field intensity and phase distribution of the vortex wave generated at 7 GHz. Fig. 9 (a) shows that the electric field exhibits a hollow characteristic. Fig. 9 In (b), it can be seen that the phase presents a counterclockwise spiral distribution, that is, a beam of l = +1 mode OAM vortex waves is generated. Fig.10 (a) Fig.10 (b) The electric field intensity and phase distribution of the vortex wave generated at 10 GHz, that is, an OAM vortex wave of l=+2 mode is generated at 10 GHz. Figure 7 The beam steering function of the metasurface at 17 GHz is demonstrated. The beam steering result is as follows: Figure 7 As shown in (a) and (b), the deflection angle is 10°, the wavelength is 17.6 mm, and the period Г is 96 mm. At the same time, the dual beam generation function is realized, such as Figure 7 As shown in (c) and (d), the deflection angles of the two beams are equal. Therefore, the designed reflective metasurface can simultaneously realize various functions in three frequency bands, realize multi-mode OAM multiplexing under multi-frequency and control beam pointing.

[0035] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0036] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A three-band multifunctional antenna based on a coded metasurface, characterized in that: The feed source is arranged above the radiation structure; the radiation structure includes: a dielectric substrate and M×N metal patch units arranged in an array on its top layer, and a metal grounding plate is arranged below the dielectric substrate; the metal patch unit is configured as: consisting of three groups of internal phase delay lines, middle phase delay lines, and external phase delay lines in symmetrical patterns.

2. The multifunctional metasurface antenna according to claim 1, characterized in that: The three groups of phase delay lines work at different frequencies. The internal phase delay line is "+" shaped, and the width w1 is fixed at 0.4mm. When working at 10GHz and the length l1 is 4.5, 5.3, 5.5, and 5.9, the phase difference is 90°, forming a 2-bit coding metasurface.

3. The multifunctional metasurface antenna according to claim 1, characterized in that: The middle phase delay line and the internal phase delay line are combined into a "rice" shape, with a width w2 fixed at 0.5 mm. When operating at 17 GHz and the length l2 is 4.11, 4.36, 4.49, and 4.93, the phase difference is 90°, forming a 2-bit coded metasurface.

4. The multifunctional metasurface antenna according to claim 1, characterized in that: The external phase delay line and the internal phase delay line are combined into a "field" shape, with a width w3 fixed at 0.5 mm, operating at 7 GHz, and lengths l3 of 1.8, 2.3, 3.3, and 3.

9. The phase difference is 90°, forming a 2-bit coded metasurface.

5. The multifunctional metasurface antenna according to claim 1, characterized in that: At 7GHz, the feed source is incident on the metasurface at θ=0, ψ=25° at a distance of 300mm from the center of the metasurface reflective array at its phase center, where θ and ψ represent the size of the pitch angle and azimuth angle, respectively. At 10GHz, the feed source is incident on the metasurface at θ=0, ψ=25° at a distance of 300mm from the center of the metasurface reflective array at its phase center, and at 17GHz, the feed source is placed vertically at a distance of 350mm from the metasurface reflective array at its phase center, and the metasurface is vertically incident. The length and width of the metasurface array are both 360mm.

6. The multifunctional metasurface antenna according to claim 1, characterized in that: When incident waves of different frequencies are incident at corresponding angles, the phase compensation required to achieve the desired function is first calculated, and then the lengths of the internal, middle, and external phase delay lines are adjusted. Using a 2-bit coded metasurface component array, the metasurface antenna generates OAM beams of l=+1 and l=+2 modes at 7 and 10 GHz, and realizes beam steering function at 17 GHz.

7. The multifunctional metasurface antenna according to claim 1, characterized in that: The array shape formed by arranging the metal patch units is square.

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