KR102127200B1 - Metasurface having different beam shaping characteristic depending on polarization of incident wave and method for manufacturing the same - Google Patents

Abstract

The meta surface according to the embodiment of the present invention is composed of a plurality of spatial filters designed to have different phase delay characteristics with respect to polarization of the incident wave. Specifically, the design parameters of each spatial filter constituting the meta surface, for example, the x-axis length and/or y-axis length of the metal patch, the x-axis width and/or y-axis width of the metal grid are asymmetrical. By designing as, it is possible to implement a meta surface having different beam forming characteristics and functions according to the polarization of the incident wave, unlike the conventional meta surface composed of a spatial filter having a square structure.

Description

Meta surface having different beam forming characteristics according to the polarization of the incident wave and a manufacturing method thereof{METASURFACE HAVING DIFFERENT BEAM SHAPING CHARACTERISTIC DEPENDING ON POLARIZATION OF INCIDENT WAVE AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a meta-surface, and more particularly, to a meta-surface that is configured to implement different functions with different beamforming characteristics according to polarization of an incident wave and a manufacturing method thereof.

An array antenna is an antenna configured to form a main beam by arranging a plurality of antenna elements to adjust the phase of the excitation current of each element and make the antenna the same phase as a specific direction. When the antenna elements are configured in an array as described above, it is possible to adjust the maximum radiation in a specific direction or the minimum radiation in an unnecessary direction. The maximum gain that can be achieved with an antenna is determined by the device's performance and arrangement, so additional components are needed to improve the gain beyond that.

Conventionally, in order to improve the gain of the incident wave emitted from the antenna, a convex lens-type dielectric lens is installed on the front surface of the antenna, but recently, an ultra-thin type meta combining a plurality of spatial filters having different phase delay characteristics. A meta-surface is being used.

The meta surface generally means a planar structure made to perform a beam shaping function using a metal pattern having a two-dimensional periodic structure. The meta surface utilized in the antenna technology field is composed of a plurality of unit cells arranged in two dimensions, and each unit cell functions as a spatial filter capable of delaying the beam emitted from the antenna by a desired phase. do. The square wave passing through the meta surface is transformed into a plane wave by compensating the phase at each point, and as a result, the gain can be improved.

1 shows an exemplary configuration of a spatial filter. Referring to FIG. 1, each spatial filter 10 constituting the meta surface 10 includes a first metal patch 11, a first insulating layer 12, a metal grid 13, and a second insulating layer ( 14), the second metal patch 15 may be configured in a stacked structure. However, this configuration is only an example and may include or exclude additional device layers according to the purpose and needs of the device. For example, each spatial filter may include five or more metal layers or may be configured to exclude metal grids.

FIG. 2 is a model of the configuration of the spatial filter of FIG. 1 using an electric circuit. Here, each metal patch (11, 15) is a capacitor having a capacitance C _patch , and the metal grid (13) is modeled as an inductor having an inductance L _grid , coupled with the inductance L _substrate of the insulating layer (12, 14) substrate It operates as a bandpass filter network. The designer can implement a desired phase delay characteristic by adjusting the thickness, length, width, and composition of the metal layer and/or the insulating layer constituting each spatial filter. By arranging a plurality of spatial filters configured to have a desired phase delay characteristic according to the phase profile of the antenna, a meta surface that converts a square wave into a plane wave or improves gain can be made.

On the other hand, in the technical field using multiple polarization while requiring high gain such as a base station antenna for 5th generation mobile communication, an antenna for radar, etc., a meta surface capable of performing different functions according to polarization is required. Since the focus is on transforming the polarization characteristics of the incident wave, the response to the polarization of the incident wave is the same. Therefore, there is a need for a new type of metasurface that can have different beamforming characteristics depending on the polarization of the incident wave.

Republic of Korea Patent Publication No. 10-2010-0118889 Republic of Korea Patent Publication No. 10-2017-0083296

C. Pfeiffer and A. Grbic, "Millimeter-Wave Transmitarrays for Wavefront and Polarization Control," in IEEE Transactions on Microwave Theory and Techniques, vol. 61, no. 12, pp. 4407-4417, Dec. 2013.

Accordingly, an object of the present invention is to provide a meta-surface configured to implement different beam shaping characteristics and functions according to polarization of an incident wave and a method of manufacturing the same.

The meta surface according to an embodiment configured to have different beam forming characteristics according to the polarization of the incident wave, the meta surface is composed of a plurality of spatial filters having respective phase delay characteristics, and each spatial filter comprises: 1 metal patch; A first insulating layer located on the first metal patch; A metal grid located on the first insulating layer; A second insulating layer located on the metal grid; And a second metal patch located on the second insulating layer, wherein the phase delay characteristic of the spatial filter varies depending on design variables, and the design variable performs different functions according to the polarization of the incident wave. Can be determined.

In one embodiment, the design parameters of the spatial filter include: the x-axis length and y-axis length of the spatial filter, the x-axis length and y-axis length of the first metal patch, and the x of the second metal patch. It may include at least one of an axial length and a y-axis length, and an x-axis width and a y-axis width of the metal grid.

In one embodiment, the design parameter of the spatial filter has the characteristic that the meta surface improves the antenna gain for the x-axis polarization of the incident wave, and the antenna gain is within a certain range for the y-axis polarization of the incident wave. It can be determined to have retaining properties.

A method of manufacturing a meta surface according to an embodiment of the present invention includes capturing a phase profile for a predetermined distance from an antenna source; Determining design variables of the spatial filter such that each spatial filter has a different phase delay characteristic according to polarization of an incident wave, based on the captured phase profile; And designing and arranging each spatial filter according to the determined design variable.

In one embodiment, designing and arranging each of the spatial filters comprises: disposing a first metal patch; Disposing a first insulating layer on the first metal patch; Disposing a metal grid on the first insulating layer; Disposing a second insulating layer on the metal grid; And disposing a second metal patch on the second insulating layer, wherein the length and width of the metal patches and the metal grid are based on the determined design parameters.

According to an embodiment of the present invention, it is possible to implement a meta surface having different beam forming characteristics according to polarization of an incident wave. To this end, the design parameters are adjusted so that each spatial filter constituting the meta surface is asymmetrically two-dimensionally so as to have different phase delay characteristics according to polarization of the incident wave.

Since the meta surface according to the embodiment provides different coverage according to polarization, various application fields using multiple polarization, in particular, a wireless communication system or radar field using dual polarization for multiple input multiple output (MIMO) or diversity Can be widely applied to In addition, in the case of a radar that divides and uses the polarization mode, the distance and the FOV can be used differently depending on the polarization. For example, if a meta surface according to an embodiment is applied to an antenna for a dual polarization radar having the same specifications, the horizontal polarization is a short-range radar As such, vertical polarization can be implemented to operate as a long-range radar.

1 shows an exemplary structure of a spatial filter constituting a meta surface.
FIG. 2 shows a circuit modeling the components of the spatial filter of FIG. 1.
3A and 3B show the structure of a spatial filter according to the prior art.
4 shows the structure of a spatial filter according to an embodiment of the present invention.
5 and 6 show the structure of a spatial filter according to another embodiment.
7 is a flowchart illustrating a method for manufacturing a meta surface according to an embodiment of the present invention.
8 shows a simulation process for designing a meta surface according to an embodiment of the present invention.
9 shows the overall appearance of the meta surface designed through the process of FIG. 8.
10 shows simulation conditions of a meta surface designed according to an embodiment.
FIG. 11 is a view showing a beam pattern analysis result according to the simulation conditions of FIG. 10.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings and the contents described in the accompanying drawings, but the scope to be claimed is not limited or limited by the embodiments.

The terminology used in the present specification has been selected as a general terminology that is currently widely used while considering functions, but this may be changed according to intentions or customs of technicians in the field or the appearance of new technologies. In addition, in certain cases, some terms are arbitrarily selected by the applicant, and in this case, the meaning will be described in the description of the corresponding specification. Therefore, the terms used in the present specification are intended to clarify that the terms should be interpreted based on the actual meaning of the terms and the contents of the present specification rather than simply the names of the terms.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

3A and 3B show the structure of a spatial filter according to the prior art. As shown in FIG. 3A, the spatial filter 30 includes a first metal patch 31, a first insulating layer 32, a metal grid 33, a second insulating layer 34 and a second metal patch 35 Is a laminated structure.

As described above, the rectangular metal patches 31 and 35 are implemented as capacitors, and the band-shaped metal grid 34 in which the inside of the rectangle is opened is implemented as an inductor. The capacitance of the metal patch and the inductance of the metal grid are determined according to the respective geometrical parameters, that is, the values of the design variables D, s, and w . The capacitance C and the inductance L according to the variable values D, s, and w can be expressed by the following equation.

Here, D denotes the length and width of the square spatial filter 30, s denotes the length from the edge of the metal patches 31 and 35 to the edge of the spatial filter 30, and w denotes the length of the metal grid 33. It is twice the width (i.e., w/2, the length from the edge of the outer rectangle to the edge of the inner rectangle).

The designer determines the phase delay characteristics of the spatial filter to be disposed at each point based on the phase profile captured from the antenna source , and adjusts geometrical parameters D, s, and w to design each spatial filter to have desired phase delay characteristics. Bandpass filter can be implemented. The designed spatial filter compensates the phase of the antenna beam at each point, converts a square wave into a plane wave, and consequently improves the antenna gain.

As can be seen in Figure 3b, the spatial filter 30, the metal patches 31, 35, and the metal grid 33 in the existing meta surface are designed in a square shape having the same horizontal and vertical lengths, so each x-axis and y The length in the axial direction (here, the x-axis and the y-axis are the axes perpendicular to each other in a two-dimensional plane horizontal to the metasurface) was the same. Due to this, it shows the same capacitance and inductance values for the x-axis polarization and the y-axis polarization of the incident wave, that is, it has no choice but to have the same function for polarization, so it is less useful in the technical field using multiple polarization. There was.

Accordingly, an embodiment of the present invention proposes a meta-surface technology designed to implement different beam forming characteristics and functions according to polarization of an incident wave. In order to realize a meta surface having different characteristics according to polarization, first, a spatial filter, which is a unit cell constituting the meta surface, must be designed to have different phase delay characteristics according to polarization.

4 is a view showing the design of a spatial filter according to an embodiment of the present invention. 4, the length and width of the metal patches (41, 45) and the metal grid (43) constituting the spatial filter (40) are s _x , s _y , and w _x variables that are variables with respect to the x and y axes. , w _y . Therefore, the spatial filter of the embodiment has different capacitance values and reactance values according to the polarization of the incident wave, unlike the conventional spatial filters designed with the same s and w values for polarization, and as a result, the meta filter performs different functions according to the polarization. Make it possible.

5 and 6 show the design of a spatial filter according to another embodiment of the present invention.

If necessary, the length D of the spatial filter can also be designed by dividing it into D _x and D _y along the x-axis and y-axis. Referring to Equation 1, 2 there can be seen that the D compared to the design parameters s and w has a greater effect on the capacitance and inductance values of the space filter, the incident wave by adjusting the design parameters D _x, D _y based on this A larger response difference between the x-axis polarization and the y-axis polarization can be induced.

For example, when the spatial filter of FIG. 5 is compared with the spatial filter of FIG. 4, the D _x value is the same, while the D _y value is half, which causes the same capacitance response to the x-axis polarization but the y-axis polarization. The capacitance response is halved. Alternatively, as shown in FIG. 6, the length of the metal patch in the y-axis direction D _y is designed to be half of the total length D of the spatial filter, and the metal grid is designed to have the same size as the spatial filter to obtain different results from the embodiment of FIG. have. In this way, the x-axis length and y-axis length of the spatial filter are configured differently to increase the degree of freedom of design.

Table 1 shows the results obtained by adjusting the design variables in the spatial filter according to the embodiment of FIG. 6. Specifically, it shows the phase shift characteristics of 10 spatial filters (UC 1 to UC 10) designed using the separate parameters s _x , s _y , w _x , and w _y for the _x and y axes.

UC# 1st metal layer Metal grid Second metal layer y-pol insertion loss
(dB) x-pol insertion loss
(dB) y-pol
Phase shift (°) x-pol
Phase shift (°) s _x
(mm) s _y
(mm) w _x
(mm) w _y
(mm) s _x
(mm) s _y
(mm) One 0.9 0.4 0.4 0.6 0.9 0.4 0.097 0.938 -18.09 -3.037 2 0.9 0.4 0.4 0.5 One 0.4 0.082 0.125 -19.00 -20.15 3 One 0.4 0.4 0.4 0.9 0.4 0.077 0.405 -20.17 -40.90 4 0.6 0.3 0.5 0.8 0.6 0.3 0.06 0.81 -20.40 -64.97 5 0.6 0.3 0.5 0.8 0.5 0.3 0.132 0.820 -20.88 -81.32 6 0.5 0.3 0.5 0.8 0.5 0.3 0.147 0.535 -19.72 -99.14 7 0.5 0.3 0.5 0.8 0.4 0.3 0.199 0.676 -18.04 -116.04 8 0.4 0.3 0.5 0.8 0.4 0.3 0.182 0.454 -18.58 -147.47 9 0.4 0.3 0.5 0.1 0.4 0.3 0.093 0.225 -28.18 -157.44 10 0.3 0.5 0.3 0.1 0.3 0.5 0.056 0.503 -20.41 -173.28

The meta surface presented in this experimental example is 28 GHz as the operating frequency band, and a λ/2 dipole antenna is used as the antenna source. The meta surface contains three metal layers (two metal patches and one metal grid). Rogers 6010 (t = 0.254 mm, εr = 10.2, tanδ = 0.0023) was used as the substrate, and Rogers 2929 (t = 0.04 mm, εr = 2.94, tanδ = 0.003) was used as the adhesive layer between the substrates.

As can be seen from the results in Table 1, for the x-axis polarization, the phase shift width of the incident wave increases by about 20° from 3 to 173°, whereas for the y-axis polarization, the phase shift within a certain range is about 18 to 20°. Have a value As a result, when the meta-surface composed of the spatial filters is applied to the antenna, the gain of the antenna can be improved by functioning as a lens having an adjustable range of about 170° for the x-axis polarization of the incident wave. For this, it functions as a permeable medium that passes through without affecting the phase.

By designing each variable of the spatial filter asymmetrically with respect to the x-axis and the y-axis, a meta surface having different phase delay characteristics and beam forming characteristics according to polarization of the incident wave can be realized.

Hereinafter, a method of manufacturing a meta surface having different beam forming characteristics according to polarization of an incident wave will be described with reference to the drawings. 7 is a flowchart illustrating a method for manufacturing a meta surface according to an embodiment of the present invention.

First, a step of capturing a phase profile for a predetermined distance from the antenna source is performed (S10). Since the phase of the incident wave reaching each point of the meta surface varies depending on the distance between the meta surface and the antenna, first, the distance at which the meta surface will be located is specified, and then the phase profile of the incident wave with respect to the distance is captured.

Next, a step of determining a phase delay characteristic of each spatial filter is performed based on the captured phase profile (S20). As described above, each spatial filter has a structure in which a first metal patch, a first insulating layer, a metal grid, a second insulating layer and a second metal patch are sequentially stacked, and each metal layer functions as a capacitor and an inductor. It operates as a band pass filter and changes the phase of the incident wave. Since each phase of the meta-surface has a different phase shift characteristic that the spatial filter must have, the phase delay characteristic of each spatial filter is determined based on the phase profile captured in step S10.

Next, a step of determining the design parameters of the spatial filter is performed such that the meta surface performs a different function according to the polarization of the incident wave (S30). The spatial filter constituting the existing meta surface includes design parameters for the x-axis and y-axis directions (x-axis length and y-axis length of the spatial filter, x-axis length and y-axis length of the first metal patch, and 2 The length of the metal patch in the x-axis direction and the length of the y-axis, the width of the metal grid in the x-axis direction and the y-axis direction, etc.) were set to have the same inductance and capacitance values for polarization in each direction.

According to an embodiment of the present invention, by setting the design variables D, s, and w of the spatial filter differently with respect to the x-axis and y-axis, the meta-surface can perform different functions for polarization in each direction. Table 1 shows the design variable values and the results.

Finally, a step of designing and arranging each spatial filter based on the determined design variable is performed (S40). The meta surface thus manufactured may have, for example, a characteristic of improving antenna gain for the x-axis polarization, and a characteristic of maintaining the antenna gain within a certain range for the y-axis polarization of the incident wave.

8 shows a simulation process for designing a meta surface according to an embodiment of the present invention. Since the λ/2 dipole antenna used in the experiment has an omni-directional beam pattern, only the first quadrant is shown. 8(a) shows the phase profile captured at a distance selected for the design of the meta surface, and (b) shows the phase delay characteristics of the spatial filter according to the variables s and w (the same as Table 1 above). FIG. 3(c) shows the number selected by selecting a spatial filter having a phase delay characteristic corresponding to the phase profile among the spatial filters in Table 1. Fig. 8(d) shows the structure of the meta surface to which the spatial filter of each number is actually applied.

9 shows the overall appearance of the meta surface designed through the process of FIG. 8. As shown, each spatial filter constituting the meta surface is designed to have an asymmetric length and width with respect to the x-axis and the y-axis, and thus, unlike the conventional symmetrical spatial filter, it is possible to implement different beam forming characteristics according to polarization.

10 shows simulation conditions of a meta surface designed according to an embodiment. For the meta-surface operation, a λ/2 dipole antenna for testing was used as a quasi-square wave source, and the meta-surface was placed at a distance of 20 mm from the antenna. In order to enter the x-axis polarization and the y-axis polarization, the meta-surface was fixed, and then the λ/2 dipole antenna was rotated 90° to simulate two cases.

11 shows beam pattern analysis results according to conditions in the simulation of FIG. 10. 11(a) shows the beam pattern of the test λ/2 dipole antenna, that is, a pattern when the meta surface is not passed, and (b) shows the beam pattern after the y-axis polarized incident wave passes through the meta surface. (C) shows the beam pattern after the x-axis polarized incident wave passes through the meta surface.

As shown, the meta-surface according to the embodiment exhibits a shape and gain similar to the beam pattern of the test λ/2 dipole antenna for the y-axis polarization of the incident wave, and thus has the characteristics of passing through a transparent medium. For the x-axis polarization, the gain is improved by about 13 dB, and it has the characteristics of passing through a convex lens.

As described above, by designing each of the spatial filter constituting the meta-surface to be asymmetric in two dimensions by adjusting design variables, meta-surfaces having different phase delay characteristics and beam forming characteristics according to polarization of the incident wave are provided. Conventional meta-surface related technologies mostly focus on modifying the polarization characteristics of the incident wave, but the meta-surface according to the embodiment provides various coverage according to the polarization, and thus can be widely applied in various applications using multiple polarization. will be.

In addition, the meta-surface of the present invention has a large difference in function and characteristics from the meta-surface of the prior art, but since the hardware configuration such as the standard is similar, it can be easily applied to an antenna platform using the existing polarization characteristics, so it is very economical. can see.

Although described above with reference to embodiments, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand.

The present invention can be applied to various fields such as a communication field (eg, a base station repeater antenna), a military field (eg, a military radar), and an automotive engineering field (vehicle radar).

Claims (7)

Meta surface having different beam forming characteristics according to the polarization of the incident wave,
The meta surface is composed of a plurality of spatial filters, and each spatial filter has a phase delay characteristic that changes the phase of the incident wave,
Each spatial filter includes: a first metal patch; A first insulating layer located on the first metal patch; A metal grid located on the first insulating layer; A second insulating layer located on the metal grid; And a second metal patch located on the second insulating layer,
The phase delay characteristic of the spatial filter depends on the design parameter related to the geometrical parameters of the spatial filter and the components included therein, and the design variable is such that the meta surface has different antenna gain characteristics according to polarization of the incident wave. Meta surface, characterized in that to be determined.
According to claim 1,
The design parameters of the spatial filter include: the x-axis length and y-axis length of the spatial filter, the x-axis length and y-axis length of the first metal patch, and the x-axis length and y of the second metal patch. Axial length, characterized in that it comprises at least one of the x-axis width and y-axis width of the metal grid, meta surface.
According to claim 2,
The design parameter of the spatial filter is such that the meta surface has a property of improving antenna gain for the x-axis polarization of the incident wave, and a property of maintaining the antenna gain within a certain range for the y-axis polarization of the incident wave. Meta surface, characterized in that to be determined.
As a method of manufacturing a meta surface having different beam forming characteristics according to polarization of an incident wave, the meta surface is composed of a plurality of spatial filters having respective phase delay characteristics,
The manufacturing method,
Capturing a phase profile for a predetermined distance from the antenna source;
Determining design variables related to geometric parameters of the spatial filter such that each spatial filter has a different phase delay characteristic according to polarization of an incident wave based on the captured phase profile; And
And designing and arranging each spatial filter according to the determined design variable,
A method of manufacturing a meta surface, characterized in that the meta surface composed of spatial filters designed and arranged according to the determined design variable has different antenna gain characteristics according to polarization of the incident wave.
According to claim 4,
The step of designing and arranging each of the spatial filters,
Disposing a first metal patch;
Disposing a first insulating layer on the first metal patch;
Disposing a metal grid on the first insulating layer;
Disposing a second insulating layer on the metal grid; And
Disposing a second metal patch on the second insulating layer,
Method of manufacturing a meta surface, characterized in that the length and width of the metal patches and the metal grid is based on the determined design parameters.
The method of claim 5,
The design parameters of the spatial filter include: the x-axis length and y-axis length of the spatial filter, the x-axis length and y-axis length of the first metal patch, and the x-axis length and y of the second metal patch. A method for manufacturing a meta surface, characterized in that it comprises at least one of an axial length and an x-axis width and a y-axis width of the metal grid.
The method of claim 6,
The design parameter of the spatial filter is such that the meta surface has a property of improving antenna gain for the x-axis polarization of the incident wave, and a property of maintaining the antenna gain within a certain range for the y-axis polarization of the incident wave. The method of manufacturing a meta surface, characterized in that to be determined.

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