WO2013060117A1

WO2013060117A1 - Microwave antenna

Info

Publication number: WO2013060117A1
Application number: PCT/CN2012/073707
Authority: WO
Inventors: 刘若鹏; 季春霖; 岳玉涛; 李星昆
Original assignee: 深圳光启高等理工研究院; 深圳光启创新技术有限公司
Priority date: 2011-10-28
Filing date: 2012-04-10
Publication date: 2013-05-02

Abstract

Disclosed is a microwave antenna, which comprises a housing having an opening on one side, and a feed source disposed on another side of the housing, and further comprises a first metamaterial closing the opening of the housing. The feed source is disposed coaxial with the first metamaterial. The first metamaterial is formed by a plurality of metamaterial sheet layers having the same thickness and same refractive index distribution. Each first metamaterial sheet layer comprises a base material and a plurality of first artificial microstructures periodically arranged on the base material. In the present invention, the refractive index distribution on the first metamaterial sheet layers is obtained through an initial phase method. The calculation process is easily programmed and coded. After a code is generated, a user only needs to master the use method of the code, which facilitates large-scale popularization. The microwave antenna becomes thinner and lighter after the metamaterial is added.

Description

Microwave antenna

[Technical Field]

The present invention relates to the field of communications technologies, and in particular, to a microwave antenna. 【Background technique】

Microwave antennas are one of the more common and important antennas in the field of communication technology. They are used for point-to-point communication and typically operate at frequencies from 12 GHz to 15 GHz. The existing microwave antenna usually adopts a horn antenna as a feed source and is parabolic. The electromagnetic waves emitted by the horn antenna are concentrated by a parabolic outer casing and radiated outward.

Existing microwave antennas are limited by the physical limitations of conventional materials, and their thickness, far-field value and directivity cannot exceed the physical limits of conventional antennas. In this case, the microwave antenna is miniaturized, highly gained, and highly directional. There are great difficulties in the process.

[Summary of the Invention]

The technical problem to be solved by the present invention is to provide a microwave antenna, which can make the microwave antenna have better directivity, and the thickness is thinner and the quality is lighter.

In order to solve the above technical problem, the present invention adopts a technical solution to provide a microwave antenna including an outer casing that is open on one side and a feed that is disposed on the other side of the outer casing, and a first metamaterial that closes the opening of the outer casing. The feed source is disposed coaxially with the first meta-material, and the first meta-material is composed of a plurality of super-material sheets having the same thickness and the same refractive index distribution, the super-material sheet layer including the first substrate and the period a plurality of first artificial microstructures arranged on the first substrate, wherein the refractive index distribution of the first metamaterial sheet is obtained by the following steps:

S1: In the case where the microwave antenna is not provided with metamaterial, the metamaterial region is filled with air and the boundary of each metamaterial layer is marked, and the electromagnetic wave radiated by the feed is tested and recorded on the front surface of the i-th layer of the metamaterial layer The initial phase, wherein the initial phase at the center point of the front surface of the i-th layer of the super-material layer is (0) _;

S2: According to the formula Ψ = φ _ί0 (0) - ^∑ '· * 2^ to obtain the phase Ψ of the surface of the metamaterial, Where d is the thickness of each layer of metamaterial sheet, A is the wavelength of the electromagnetic wave radiated by the feed, n _raax is the maximum refractive index of the metamaterial, and M is the layer of metamaterial constituting the metamaterial total floors;

S3: According to the formula _Ψ = φ ί0 (y) - ^Σ refractive index "* 2π points obtained over material Μ (,

A

Where y is the distance from any point on the metamaterial to the central axis of the metamaterial.

Wherein all the first artificial microstructures on the same layer of the first metamaterial have the same geometric shape, and are arranged in a circular shape on the first substrate, and the first artificial microstructure at the center of the circle has the largest geometrical shape. The first artificial microstructures at the same radius have the same geometrical dimensions.

Wherein the first metamaterial sheet further comprises a cover layer, and all of the first artificial microstructures on the same metamaterial sheet are sandwiched between the substrate and the cover layer.

The microwave antenna further includes a second metamaterial closely attached to the aperture surface of the feed, the second metamaterial being disposed coaxially with the feed and the first metamaterial; the second metamaterial includes a second substrate and a plurality of second artificial microstructures periodically arranged on the second substrate, the second metamaterial comprising a circular region and a plurality of annular regions concentric with the circular region, The circular region and the annular region have the same refractive index variation range, and the minimum refractive index from the second metamaterial continuously increases to the maximum refractive index 1 and the same radius as the radius increases. The refractive index is the same.

Wherein, the second metamaterial has a center point as a center, and a refractive index distribution at a radius r is:

N(r) + _ ) * sin(2^ * where L represents the length of the second metamaterial, n _rain represents the minimum refractive index value of the second metamaterial, and n _raax represents the second metamaterial The maximum refractive index value, n represents the number of refractive index change periods of the second metamaterial of the L length, and the refractive index of the second metamaterial changes from the minimum refractive index to the maximum refractive index for one period.

The second substrate is made of the same material as the first substrate, and the second substrate and the first substrate are made of a polymer material, a ceramic material, a ferroelectric material, a ferrite material or a ferromagnetic material. production.

Wherein, the second artificial microstructure is the same as the first artificial microstructure material and geometry. Wherein the second artificial microstructure and the first artificial microstructure are metal microstructures having a "gong"-shaped geometry, the metal microstructures including a vertical first metal branch and located at the a metal branch having two ends and perpendicular to the two second metal branches of the first metal branch.

Wherein, the metal microstructure further includes a third metal branch located at each end of each second metal branch and perpendicular to the second metal branch.

Wherein the second artificial microstructure and the first artificial microstructure are metal microstructures having a planar snowflake-shaped geometry, the metal microstructures comprising two first metal branches perpendicular to each other and located at the a metal branch having two ends and perpendicular to the second metal branch of the first metal branch.

The two first metal branches intersect perpendicularly at a midpoint, and the second metal branch midpoint coincides with the first metal branch end point.

Wherein, the feed source is a circular waveguide whose open end faces the center of the metamaterial.

Different from the prior art, the beneficial effects of the present invention are: The refractive index distribution on the first metamaterial sheet of the present invention is obtained by an initial phase method, and the calculation process is easy to realize programmatic and coding, and after forming the code, the user It is only necessary to master the use of the code, which is convenient for large-scale promotion, and the microwave antenna after adding the super material has a thinner thickness and a lighter quality.

[Description of the Drawings]

1 is a schematic perspective view of a basic unit constituting a metamaterial;

2 is a schematic structural view of a microwave antenna of the present invention;

3 is a schematic diagram of calculation of a refractive index distribution of a first metamaterial of the present invention;

4 is another schematic structural view of a microwave antenna of the present invention;

Figure 5 is a schematic view showing a refractive index distribution of a cross section of a second metamaterial of the present invention;

6 is a schematic view showing a longitudinal section refractive index distribution of a second metamaterial of the present invention;

Figure 7 is a far field diagram of the electromagnetic wave radiated by the feed after passing through the second metamaterial;

Figure 8 is a geometric topographical pattern of a man-made metal microstructure of a first preferred embodiment of the present invention which is responsive to electromagnetic waves to alter the refractive index of the base element of the metamaterial;

Figure 9 is a derivative pattern of the artificial metal microstructure geometry topographical pattern of Figure 8;

Figure 10 is a second embodiment of the present invention capable of responding to electromagnetic waves to change the refractive index of the base element of the metamaterial. a geometric topological pattern of the man-made metal microstructure of the preferred embodiment;

Figure 11 is a derivative pattern of the artificial metal microstructure geometry topographical pattern of Figure 10.

【detailed description】

The invention will now be described in detail in conjunction with the drawings and embodiments.

Light, as a kind of electromagnetic wave, when passing through the glass, because the wavelength of the light is much larger than the size of the atom, we can describe the overall parameters of the glass, such as the refractive index, rather than the details of the atoms that make up the glass. The response of the glass to light. Correspondingly, when studying the response of materials to other electromagnetic waves, the response of any structure in the material that is much smaller than the wavelength of the electromagnetic wave to the electromagnetic wave can also be described by the overall parameters of the material, such as the dielectric constant ε and the magnetic permeability μ. By designing the structure of each point of the material, the dielectric constant and magnetic permeability of each point of the material are the same or different, so that the dielectric constant and magnetic permeability of the material are arranged regularly, and the magnetic permeability and the regular arrangement are regularly arranged. The electrical constant allows the material to have a macroscopic response to electromagnetic waves, such as converging electromagnetic waves, diverging electromagnetic waves, and the like. This type of material with regularly arranged magnetic permeability and dielectric constant is called a metamaterial.

As shown in FIG. 1, FIG. 1 is a schematic perspective view of a basic unit constituting a metamaterial. The basic unit of the metamaterial includes the artificial microstructure 1 and the substrate 2 to which the artificial microstructure is attached. In the present invention, the artificial microstructure is an artificial metal microstructure, and the artificial metal microstructure has a planar or stereo topology capable of responding to an incident electromagnetic wave electric field and/or a magnetic field, and changes the artificial metal microstructure on each metamaterial basic unit. The pattern and/or size can change the response of each metamaterial base unit to incident electromagnetic waves. The arrangement of a plurality of metamaterial basic units in a regular pattern enables the metamaterial to have a macroscopic response to electromagnetic waves. Since the supermaterial as a whole needs to have a macroscopic electromagnetic response to the incident electromagnetic wave, the response of each metamaterial basic unit to the incident electromagnetic wave needs to form a continuous response, which requires that the size of each metamaterial basic unit is one tenth to five fifths of the incident electromagnetic wave. First, it is preferably one tenth of the incident electromagnetic wave. In the description of this paragraph, we artificially divide the supermaterial into a plurality of basic units of metamaterials, but it should be understood that this method of division is only convenient for description, and should not be regarded as supermaterial being spliced or assembled by multiple metamaterial basic units. In the actual application, the super material is formed by arranging the artificial metal microstructure period on the substrate, and the process is simple and the cost is low. Week The term arrangement refers to the man-made metal microstructure on the basic unit of each metamaterial divided by our above, which can produce continuous electromagnetic response to incident electromagnetic waves. In the present invention, the substrate may be selected from a polymer material, a ceramic material, a ferroelectric material, a ferrite material or a ferromagnetic material, and the polymer material is preferably FR-4 or F4B. The artificial metal microstructure can be arranged on the substrate by etching, electroplating, drilling, photolithography, electron engraving or ion etching, wherein the etching is a superior process, the step of covering the metal sheet on the substrate, The chemical solvent is then used to remove metals other than the preset artificial metal pattern.

In the present invention, the refractive index distribution of the overall material of the super material is designed by using the above-mentioned principle of metamaterial, and then the artificial metal microstructure is periodically arranged on the substrate according to the refractive index distribution to change the electromagnetic response of the incident electromagnetic wave to realize the required function. .

As shown in FIG. 2, FIG. 2 is a schematic structural view of a microwave antenna of the present invention. In Fig. 2, the microwave antenna includes a feed 10, an outer casing 20 that is open on one side, and a first metamaterial 30 that is open to the closed casing. The feed 10 is disposed coaxially with the first metamaterial 30. In the present invention, the feed 10 employs a circular waveguide having an open end facing the center of the first metamaterial. The outer casing is made of a metal reflector that reflects electromagnetic waves emitted from the feed to the super material; the metamaterial converts electromagnetic waves into planar electromagnetic waves to improve the directivity of the microwave antenna.

For refractive index design on metamaterials, the conventional design method is the formula method, which uses the principle of equal optical path approximation to obtain the corresponding refractive index values at each point of the metamaterial. The refractive index distribution of the metamaterial obtained by the formula method can be applied to the simpler system simulation design. However, due to the fact that the electromagnetic wave distribution is not perfectly consistent with the distribution of electromagnetic waves in the software simulation, the complex method is obtained by the formula method. There is a large error in the refractive index distribution of the metamaterial.

The present invention utilizes an initial phase method to obtain a refractive index profile at each point of the first metamaterial such that the first metamaterial achieves the purpose of converting electromagnetic waves into planar electromagnetic waves. In the present invention, the first metamaterial is composed of a plurality of super-material sheets laminated, each of the super-material sheets comprising a first substrate and a first artificial metal microstructure periodically arranged on the first substrate, each meta-material The sheets are of equal thickness and the same refractive index profile. In this embodiment, all of the first artificial microstructures on the same layer of the first metamaterial have the same geometric shape, and are arranged in a circular shape on the first substrate, and the first artificial microstructure at the center of the circle has the largest geometrical size. The first artificial microstructure at the same radius has the same geometrical size; the first metamaterial sheet further includes a cover layer to encapsulate the first person A metal microstructure is formed, and a cover layer is disposed on the plurality of first artificial metal microstructures.

The initial phase in the initial phase method is defined as follows: As shown in FIG. 3, the first metamaterial region is filled with air in the initial stage of design, and the first metamaterial shares the M layer, and only the supermaterial sheets in the first metamaterial region are marked. The boundary of the layer. At this time, the internal refractive index of the first metamaterial region is 1, and the front surface of the i-th layer is selected and the initial phase of the front surface is recorded (where the initial phase at the center point of the front surface of the i-th layer is ( 0) Herein, the front surface refers to a surface close to the feed, and the rear surface refers to a surface away from the feed opposite the front surface.

In the present invention, the first metamaterial needs to cause the electromagnetic wave to radiate in the form of a plane wave and the metamaterial to be in the form of a flat plate. Therefore, it is necessary to make the phase of the first supermaterial back surface, the phase distribution, etc., that is, the phase of the back surface of the first metamaterial does not follow the y value. The change is a change, which is a fixed value Ψ, which is the phase at the center point of the back surface of the first metamaterial. The refractive index on the first metamaterial is an artificial design, so at the time of design, the maximum refractive index value 1 of the first metamaterial and the minimum refractive index value _nrain are fixed values due to technical limitations. In the present invention, the refractive index of each layer of the super material sheet on the central axis of the first metamaterial is the maximum refractive index n _raax , according to the formula:

Depreciation can be obtained. Where d is the thickness of each layer of metamaterial sheet, and A is the wavelength of the electromagnetic wave radiated by the feed. Then according to the formula:

n(y)d gives the refractive index at each point of the first metamaterial.

In the present invention, a plurality of sets of data can be obtained by taking values on a plurality of metamaterial sheets to filter out the optimal data to determine the distribution.

The initial phase method is used to obtain the refractive index distribution of the first metamaterial. When the electromagnetic wave source is complicated, it is difficult to determine the coefficient by the conventional formula method. When the satisfactory result is not obtained or even the formula method cannot be used, the initial phase method can be easily obtained. As a result, the optimal result is better than the optimal result obtained by the conventional formula method, and it is excellent in all aspects; and the initial phase method calculation process is easy to implement programmatic and coded. After the code is formed, the user only You need to master the use of the code, which is convenient for large-scale promotion.

As shown in FIG. 4, FIG. 4 is another schematic structural diagram of a microwave antenna according to the present invention. Figure 4, microwave The antenna includes a housing 20 that is open on one side and a feed 10 disposed on the other side of the housing 20, a second metamaterial 40 that abuts the aperture of the feed 10, and a first metamaterial 30 that closes the opening of the housing. The feed 10 is disposed coaxially with the second metamaterial 40 and the first metamaterial 30. In the present invention, the feed 10 employs a circular waveguide. The second metamaterial 40 separates the electromagnetic waves radiated by the feed 10 into two electromagnetic waves to expand the radiation range of the feed, increase the overall gain of the microwave antenna, and thin the thickness of the microwave antenna; the outer casing is made of a metal reflector, which will feed The emitted electromagnetic wave is reflected to the metamaterial; the first metamaterial 30 converts electromagnetic waves radiated into the surface of the first metamaterial 30 into the cavity to be radiated into the plane electromagnetic wave to improve the directivity of the microwave antenna.

The second metamaterial 40 includes a second substrate and a plurality of second man-made metal microstructures periodically arranged on the second substrate, and the refractive index distribution of the second metamaterial 40 is calculated by a formula. Please refer to FIG. 5 and FIG. 6 , which are schematic diagrams of refractive index distributions of the second metamaterial 40 in cross section and longitudinal section, respectively. In FIG. 5, the second metamaterial 40 includes a circular region and a plurality of annular regions concentric with the circular region, and the circular region and the annular region have the same range of refractive index variation, both of which increase with the radius. The minimum refractive index n _{min of the} two metamaterials continuously increases to the maximum refractive index n _max and the refractive index at the same radius is the same.

Further, on the second metamaterial, the center of the second metamaterial is centered, and the refractive index distribution at a radius r is:

N(r) + _ ) * sin(2^ * where L represents the length of the second metamaterial, n represents the number of refractive index change periods of the second metamaterial of the L length, and the refractive index of the second metamaterial is minimized The refractive index changes to a maximum refractive index of one cycle.

The electromagnetic wave responded by the second metamaterial is only the electromagnetic wave radiated by the feed source. Therefore, the refractive index distribution formula N(r) of the second metamaterial can be obtained by using the principle that the optical path is approximately equal, and the experimental simulation result of the formula N(r) It is not much different from the actual test results. As shown in Fig. 7, Fig. 7 is a far field diagram of the electromagnetic wave radiated by the feed after passing through the second metamaterial. In Figure 7, it can be seen that in the range of radiation angles 0 ° to -50 ° and 0 ° to 50 °, the far field value has a distinct peak, that is, the spherical electromagnetic wave of the feed radiation is separated after passing through the second metamaterial. Two electromagnetic waves symmetrically symmetrical with respect to the central axis of the second metamaterial, the two electromagnetic waves deviating from the central axis of the beam splitting element by an angle of 50 °

Several artificial metal microstructures satisfying the refractive index distribution requirements of the first metamaterial and the second metamaterial described above There are many shapes, but they are all geometric shapes that respond to incident electromagnetic waves. The most typical is the "work" shaped artificial metal microstructure. Several man-made metal microstructure geometries are described in detail below. The size of the artificial metal microstructure corresponding to the refractive index of each point on the first metamaterial and the second metamaterial can be obtained by computer simulation or manually. In the present invention, in order to facilitate mass production, the first substrate and the second substrate of the first metamaterial and the second metamaterial are made of the same material, and the first metal microstructure and the second metal microstructure have the same geometry; The material of the material and the second substrate is made of a polymer material, a ceramic material, a ferroelectric material, a ferrite material or a ferromagnetic material, or other materials satisfying the requirements of the substrate.

As shown in Fig. 8, Fig. 8 is a geometric topographical pattern of a man-made metal microstructure of a first preferred embodiment capable of responding to electromagnetic waves to change the refractive index of the base element of the metamaterial. In FIG. 8, the man-made metal microstructure has a "work" shape, including a vertical first metal branch 1021 and a second metal branch 1022 that is perpendicular to the first metal branch 1021 and located at opposite ends of the first metal branch, FIG. 9 is a diagram A derivative pattern of the man-made metal microstructure geometry topographic pattern of 8 includes not only the first metal branch 1021 and the second metal branch 1022, and a third metal branch 1023 is vertically disposed at each end of each of the second metal branches.

Figure 10 is a geometric topographical pattern of a man-made metal microstructure of a second preferred embodiment capable of responding to electromagnetic waves to alter the refractive index of the meta-material base unit. In FIG. 10, the artificial metal microstructure is a flat snowflake type, including a first metal branch 102Γ perpendicular to each other and a second metal branch 1022′ disposed at both ends of the first metal branch 102Γ; FIG. 11 is FIG. A derivative pattern of the artificial metal microstructure geometry topology pattern includes not only two first metal branches 1021 ', four second metal branches 1022, but also a third metal branch 1023 disposed at two ends of the four second metal branches. Preferably, the first metal branches 102 长度 are equal in length and intersect perpendicular to the midpoint, the second metal branches 1022 ′ are of equal length and the midpoint is at the end of the first metal branch, the third metal branch 1023 is of equal length and the midpoint is at the second metal The end points of the branches; the arrangement of the above metal branches makes the artificial metal microstructures is isotropic, that is, the artificial metal microstructures rotated 90° in any direction in the plane of the artificial metal microstructures can coincide with the original artificial metal microstructures. The use of isotropic man-made metal microstructures simplifies design and reduces interference.

The present invention utilizes the above method to design the first metamaterial and the second metamaterial and test the radiation parameters thereof, wherein the first metamaterial and the second metamaterial have the same maximum refractive index value and minimum refractive index value, and maximum refraction. The first material level is 0. 01 meters, the first material level is 0. 01 meters, the first material thickness is 0. The thickness of the second super material is 0.1 m, and the electromagnetic wave frequency of the feed vehicle is 13 GHz. The test results are as follows:

Far field maximum: 53. 72db, half power beamwidth: 2. 2 °, side lobes: 45. 35db.

It can be seen from the above test results that the thickness of the metamaterial is thin, and the thickness of the microwave antenna is not increased, and the far field value of the microwave antenna is increased, and the directivity is remarkably enhanced.

The above is only the embodiment of the present invention, and is not intended to limit the scope of the invention, and the equivalent structure or equivalent process transformation of the specification and the drawings of the present invention may be directly or indirectly used in other related The technical field is equally included in the scope of patent protection of the present invention.

Claims

Rights request

A microwave antenna comprising an outer casing open on one side and a feed disposed on the other side of the outer casing, further comprising: a first metamaterial enclosing the opening of the outer casing, the feed and the first metamaterial Coaxially disposed, the first metamaterial is composed of a plurality of super-material sheets having the same thickness and the same refractive index distribution, the first meta-material sheet layer comprises a first substrate and is periodically arranged on the first substrate The plurality of first artificial microstructures, the refractive index distribution of the first metamaterial sheet is obtained by the following steps:

S1: in the case where the microwave antenna is not provided with the first metamaterial, fill the first metamaterial region with air and mark the boundary of each first metamaterial layer, and test and record the electromagnetic wave radiated by the feed in the i-th layer An initial phase o of the front surface of the first metamaterial sheet, wherein an initial phase at a center point of the front surface of the first metamaterial sheet of the i-th layer is ^(0);

S2 : According to the formula Ψ = * 2 τ, the phase of the surface of the first metamaterial is obtained,

Where d is the thickness of the first metamaterial sheet of each layer, A is the wavelength of the electromagnetic wave radiated by the feed, n _raax is the maximum refractive index value of the first metamaterial, and M is the first metamaterial The total number of layers of the super material sheet;

S3: According to the formula Ψ = φ _ί0 (y) - ^∑ " * 2π obtains the refractive index of each point of the first metamaterial ^,

A

Where y is the distance of any point on the first metamaterial from the central axis of the first metamaterial.

The microwave antenna according to claim 1, wherein: all first artificial microstructures on the same layer of the first metamaterial have the same geometry, and have a circular row on the first substrate. In the cloth, the first artificial microstructure at the center of the circle has the largest geometrical size, and the first artificial microstructure at the same radius has the same geometrical size.

The microwave antenna according to claim 1, wherein: the first metamaterial sheet further comprises a cover layer, and all first artificial microstructures on the same metamaterial sheet are clamped on the substrate and covered. Between the layers.

The microwave antenna according to claim 1, wherein the first substrate is made of a polymer material, a ceramic material, a ferroelectric material, a ferrite material, or a ferromagnetic material.

The microwave antenna according to claim 1, wherein: the first artificial microstructure is a metal microstructure having a "work"-shaped geometry, the metal microstructure including a vertical first metal branch and Two second metal branches located at both ends of the first metal branch and perpendicular to the first metal branch.

The microwave antenna according to claim 5, wherein the metal microstructure further comprises a third metal branch located at each end of each of the second metal branches and perpendicular to the second metal branch.

The microwave antenna according to claim 1, wherein: the first artificial microstructure is a metal microstructure having a planar snowflake shape, and the metal microstructure comprises two first metals perpendicular to each other And a second metal branch located at both ends of the first metal branch and perpendicular to the first metal branch.

The microwave antenna according to claim 7, wherein: the two first metal branches intersect perpendicularly at a midpoint, and the second metal branch midpoint coincides with the first metal branch end.

The microwave antenna according to claim 1, wherein: the microwave antenna further comprises a second metamaterial closely attached to the aperture surface of the feed, the second metamaterial and the feed source and a metamaterial is disposed coaxially; the second metamaterial includes a second substrate and a plurality of second artificial microstructures periodically arranged on the second substrate, the second metamaterial comprising a circular region and a plurality of annular regions concentric in the circular region, wherein the circular region and the annular region have the same refractive index variation range, and the minimum refractive index of the second metamaterial is increased as the radius increases. n _{min is} continuously increased to the maximum refractive index n _max and the refractive indices at the same radius are the same.

The microwave antenna according to claim 9, wherein: the second metamaterial has a center point as a center, and a refractive index distribution at a radius r is:

N(r) + _ ) * sin(2^ * where L represents the length of the second metamaterial, n _min represents the minimum refractive index value of the second metamaterial, and n _max represents the second metamaterial The maximum refractive index value, n represents the number of refractive index change periods of the second metamaterial of the L length, and the refractive index of the second metamaterial changes from the minimum refractive index to the maximum refractive index for one period.

The microwave antenna according to claim 9, wherein the second substrate is made of the same material as the first substrate.

The microwave antenna according to claim 9, wherein: the second artificial microstructure is the same as the first artificial microstructure material and geometry.

The microwave antenna according to claim 1, wherein the feed source is a circular waveguide whose open end faces the center of the metamaterial.