A surface wave suppression antenna based on space Kramers-Kronig medium

Abstract

This invention discloses a surface wave suppression antenna based on a spatial Kramers-Kronig medium. The surface wave suppression antenna includes at least one antenna element, each antenna element comprising an antenna substrate and a spatial Kramers-Kronig medium layer. The spatial Kramers-Kronig medium layer is laid on the upper surface of the antenna substrate and includes at least one KK medium layer, which is composed of several KK medium blocks of the same shape and size arranged periodically. Each KK medium block includes a dielectric layer, metal pillars, and two metal circuit layers. The two metal circuit layers are respectively disposed on the top and bottom surfaces of the dielectric layer, and the metal pillars are arranged inside the dielectric layer, with their two ends connected to the two metal circuit layers respectively. The antenna KK medium layer provided by this invention can achieve omnidirectional non-reflective suppression of surface waves, improving antenna performance.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing media and artificial electromagnetic materials, and in particular to a surface wave suppression antenna based on spatial Kramers-Kronig medium. Background Technology

[0002] In recent years, electromagnetic interference has become increasingly severe, making electromagnetic shielding technology a focus of attention. Given that surface waves (SWs) are easily excited by space waves, there is a significant demand for SW shielding, for applications such as radar cross-section manipulation, electromagnetic shielding, and antenna arrays. For example, microstrip antennas excite SWs propagating along a dielectric substrate during resonance. The cutoff frequency of the TM0 mode SW is 0, thus microstrip antennas are susceptible to SW effects, especially when the patch is printed on materials with high dielectric constants such as gallium arsenide or silicon. SW propagation causes increased back radiation and interference in the main radiation direction, leading to severe deterioration of the back lobe, side lobes, and antenna radiation performance. Currently, there are four main categories of methods for suppressing SWs. The first is to use synthetic dielectric substrates to achieve a low dielectric constant, thereby reducing the excitation intensity of SWs. The second is to use high-impedance surfaces (such as EBG structures) to suppress SW propagation, but high-impedance surfaces can cause reflection and scattering of SWs. The third is to design SW-reducing antennas; when the radius of the circle is specific, the antenna will not excite TM0 mode SWs, but this method is only effective for specific types of antennas. The fourth approach involves designing absorbers with matched wave vectors and impedances to suppress surface waves. However, this type of absorbing material is implemented using metamaterials and can only absorb normally incident surface waves. Immersing materials based on perfectly matched layers, transform optics, and parity-time symmetry can achieve omnidirectional absorption, but the existence of the "gain factor" heavily depends on active devices, increasing engineering complexity.

[0003] Previous methods for suppressing surface waves have all failed to prevent reflection, which disrupts the original modes of the radiation source, such as polarization characteristics and impedance matching. To date, no research has been reported on omnidirectional absorbers for surface waves. Therefore, finding an absorbing medium that can improve the poor absorption efficiency of absorbing materials at large angles and achieve perfect omnidirectional absorption of electromagnetic waves in half-space without requiring a "gain factor" is of great significance. Summary of the Invention

[0004] To address the problems existing in the background art, this invention provides a surface wave suppression antenna based on a spatial Kramers-Kronig medium. This invention achieves this by loading a spatial Kramers-Kronig (KK) medium layer onto the surface of the antenna element, ensuring that the electromagnetic parameters of the surface wave entering the spatial Kramers-Kronig medium are equal to those in free space, without needing to consider impedance and wave vector issues. This effectively suppresses electromagnetic waves propagating along the surface of the dielectric substrate, achieving omnidirectional, non-reflective absorption of surface waves.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] The surface wave suppression antenna includes at least one antenna element. Each antenna element includes an antenna substrate and a spatial KK medium layer. The spatial KK medium layer is laid on the upper surface of the antenna substrate and includes at least one KK medium layer. The KK medium layer is composed of several KK medium blocks with the same shape and size arranged periodically. Each KK medium block includes a KK dielectric layer, a metal pillar, and two metal circuit layers. The two metal circuit layers are respectively located on the top and bottom surfaces of the KK dielectric layer. The metal pillar is vertically arranged inside the KK dielectric layer, and its two ends are connected to the two metal circuit layers respectively.

[0007] Each metal circuit layer includes a rectangular metal sheet and two serpentine metal sheets. The rectangular metal sheet is arranged in the center of the metal circuit layer, and the two serpentine metal sheets are arranged on both sides of the rectangular metal sheet. The size and structure of the two serpentine metal sheets are symmetrical with respect to the rectangular metal sheet. One end of each serpentine metal sheet extends towards the rectangular metal sheet and connects to it. The two serpentine metal sheets are connected to the two sides of the same end of the rectangular metal sheet. The geometric center of the rectangular metal sheet, the geometric center of the two metal circuit layers, and the geometric center of the KK dielectric layer are all located on the axis of the metal pillar.

[0008] The two metal circuit layers are a first metal circuit layer and a second metal circuit layer, respectively. After the first metal circuit layer is rotated 180° about the center, it is aligned with the second metal circuit layer in the axial direction of the metal column. The upper and lower ends of the metal column are connected to the first metal circuit layer and the second metal circuit layer, respectively.

[0009] The periodic arrangement is as follows: the KK medium layer includes four trapezoidal KK medium units. The cross-section of the four trapezoidal KK medium units in the radial direction of the metal column is an isosceles trapezoid, and the cross-section of the KK medium layer in the radial direction of the metal column is a square ring. The four trapezoidal KK medium units are closely arranged around the center of the antenna substrate to form a square ring, and cover the upper surface of the antenna substrate except for the inner square area of ​​the square ring. Each trapezoidal KK medium unit includes multiple KK medium blocks. In the trapezoidal area where the same trapezoidal KK medium unit is located, the KK medium blocks are closely arrayed along the two sides of the KK medium layer, and the long side of each KK medium block is arranged along the direction parallel to the bottom side of the trapezoidal area.

[0010] The KK medium layer also includes several medium-air mixing medium units. All medium-air mixing medium units are triangular pyramids, with the edges of the pyramids parallel to the axis of the metal column. All medium-air mixing medium units are arranged along the four inner walls of the KK medium layer, forming serrated protrusions on the four inner walls. Each medium-air mixing medium unit has one side that fits against the corresponding inner wall, and adjacent medium-air mixing medium units share an edge.

[0011] The antenna substrate includes an antenna dielectric layer, a feed axis, a microstrip slot patch, and a ground metal layer. The feed axis is vertically arranged inside the antenna dielectric layer. The upper and lower ends of the feed axis are connected to the microstrip slot patch and the ground metal layer, respectively. The ground metal layer is arranged on the lower surface of the antenna dielectric layer, and the microstrip slot patch is arranged on the upper surface of the antenna dielectric layer.

[0012] Both the microstrip slot patch and the upper surface of the antenna dielectric layer are square in shape. The microstrip slot patch is positioned at the center of the upper surface of the antenna dielectric layer, with a slot at its center. The two sides of the microstrip slot patch are parallel to the two sides of the antenna dielectric layer, respectively. The spatial KK medium layer is laid on the upper surface of the antenna dielectric layer, and four trapezoidal KK medium elements in the same KK medium layer are respectively arranged on the four sides of the microstrip slot patch.

[0013] The spatial KK medium layer also includes several air layers, all of which have the same thickness. An air layer is arranged above and below each KK medium layer, covering the surface of the corresponding KK medium layer and fitting snugly against it.

[0014] The dielectric constant of the air layer is 1, and the permeability is 1.

[0015] The thickness of the KK medium layer is less than one-quarter of the operating wavelength of the antenna substrate.

[0016] In the KK dielectric layer, the material of the KK dielectric layer is F4B, the relative permittivity is 3.5, and the loss tangent is 0.003.

[0017] The relative permittivity distribution ε of all space KK media layers in any tangential plane rz (d) Satisfies the following formula:

[0018]

[0019] Where, ω L This is the Lorentz resonant frequency of the KK medium layer in space;

[0020] ω p The plasma frequency of the space KK medium layer at the Lorentz resonant frequency;

[0021] γ is the damping coefficient of the spatial KK medium layer at the Lorentz resonant frequency;

[0022] q is the relative permittivity ε of the space KK medium layer. rz Rate of change with d;

[0023] d is the distance between any location and the center of the spatial KK medium layer;

[0024] ω0 is the operating frequency of the antenna element;

[0025] i is the imaginary unit.

[0026] Wherein, the rate of change q of the relative permittivity along the radial linear direction is:

[0027] q=ω0 / λ0

[0028] Where ω0 is the operating frequency of the antenna element, and λ0 is the free space wavelength corresponding to ω0.

[0029] The beneficial effects of this invention are:

[0030] (1) This invention loads a spatial Kramers-Kronig (KK) medium layer onto the antenna element, making the electromagnetic parameters of the surface wave entering the spatial KK medium equal to those in free space, without needing to consider impedance and wave vector issues. This effectively suppresses electromagnetic waves propagating along the surface of the dielectric plate, achieving omnidirectional, non-reflective absorption of surface waves. This invention is significant for improving the poor absorption efficiency of absorbing materials at large angles and addressing the need for a "gain factor" in artificial absorbing media.

[0031] (2) The antenna KK medium layer provided by the present invention can achieve omnidirectional non-reflection suppression of surface waves and improve antenna performance. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention.

[0033] Figure 2 The graph shows the surface wave absorptivity, reflectivity, and transmittance of the spatial KK medium layer as a function of frequency at different incident angles θ, based on the theoretical model of the spatial KK medium layer constructed for this invention.

[0034] Figure 3 The spatial KK medium layer theoretical model constructed for this invention is shown at different profile heights h. KK The graph shows the changes in surface wave absorptivity, reflectivity, and transmittance of the KK medium layer with frequency.

[0035] Figure 4 This is a schematic diagram of the spatial KK medium layer theoretical model constructed in this invention.

[0036] Figure 5 The equivalent constitutive parameter curves obtained by inverting the KK medium block simulation model in an embodiment of the present invention are shown.

[0037] Figure 6 The discrete dielectric constant spatial distribution curve is obtained by inverting the KK medium block simulation model in an embodiment of the present invention.

[0038] Figure 7 This is a comparison chart of the simulation and test results of the surface wave suppression antenna based on the spatial KK medium layer according to an embodiment of the present invention.

[0039] Figure 8 This is a comparison of simulation and test results of the axial ratio as a function of frequency at the location directly above the radiation of the surface wave suppression antenna based on the spatial KK medium layer, according to an embodiment of the present invention.

[0040] Figure 9 This is a comparison of simulation and test results of the xz-plane axial ratio of the surface wave suppression antenna based on a spatial KK medium layer according to an embodiment of the present invention as a function of angle.

[0041] Figure 10 This is a comparison of simulation and test results of the yz plane axial ratio of the surface wave suppression antenna based on the spatial KK medium layer according to an embodiment of the present invention as a function of angle.

[0042] Figure 11 The antenna simulation and test patterns of the surface wave suppression antenna based on the spatial KK medium layer in different planes are shown in the embodiments of the present invention. Figure 11 (a) shows the antenna simulation and test radiation pattern in the xz plane; Figure 11 (b) shows the antenna simulation and test pattern in the yz plane.

[0043] In the diagram: 1. Antenna element, 2. Space KK dielectric layer, 3. Antenna dielectric layer, 4. Feed axis, 5. Microstrip slot patch, 6. Grounding metal layer, 7. KK dielectric layer, 8. First metal circuit layer, 9. Metal pillar, 10. Air layer, 11. Second metal circuit layer. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] First, this invention, through the design of a spatial Kramers-Kronig (KK) medium layer, ensures that the electromagnetic parameters of surface waves entering the spatial KK medium are equal to those in free space, without needing to consider impedance and wave vector issues. This effectively suppresses electromagnetic waves propagating along the surface of the dielectric substrate, achieving omnidirectional, non-reflective absorption of surface waves. Second, as an example, this invention provides a surface wave suppression antenna. By attaching a spatial KK medium layer around the antenna, the propagation of surface waves excited during antenna resonance can be effectively suppressed. Compared to methods such as EBG structures that suppress surface waves through high-impedance surfaces, the spatial KK medium layer does not affect the resonance of the antenna element itself and effectively improves the antenna's front-to-back ratio, back lobe, and axial ratio.

[0046] The absorbing medium provided by this invention can achieve surface electromagnetic wave absorption at all angles. The spatial KK medium layer provided by this invention is applicable to multiple arbitrary absorbing frequency bands, and therefore is suitable for microstrip antennas of any frequency band, especially broadband microstrip antennas.

[0047] Figure 1 (I) shows the side and top views of the microstrip antenna, as shown below. Figure 1 As shown in (I), the surface wave suppression antenna includes at least one antenna element 1. Each antenna element 1 includes an antenna substrate and a spatial KK medium layer 2. The spatial KK medium layer 2 is laid on the upper surface of the antenna substrate. The spatial KK medium layer 2 includes at least one KK medium layer. The KK medium layer is composed of several KK medium blocks with the same shape and size arranged periodically.

[0048] The KK medium block comprises a KK dielectric layer 7, metal pillars 9, and two metal circuit layers. The two metal circuit layers are respectively located on the top and bottom surfaces of the KK dielectric layer 7. The metal pillars 9 are vertically arranged inside the KK dielectric layer 7, with their ends connected to the two metal circuit layers. The KK medium block is rectangular in shape, with its length parallel to the length of the metal circuit layers and its width parallel to the width of the metal circuit layers. The length of the KK medium block is greater than the overall length of the metal circuit layers (first metal circuit layer 8 and second metal circuit layer 11) within the KK medium block; the width of the KK medium block is greater than the overall width of the metal circuit layers (first metal circuit layer 8 and second metal circuit layer 11) within the KK medium block.

[0049] Each metal circuit layer includes one rectangular metal strip and two serpentine metal strips. The rectangular metal strip is positioned in the center of the metal circuit layer, and the two serpentine metal strips are positioned on either side of the rectangular metal strip. The size and structure of the two serpentine metal strips are symmetrically arranged relative to the rectangular metal strip. One end of each serpentine metal strip extends towards the rectangular metal strip and connects to it. Each serpentine metal strip connects to the two sides of the same end of the rectangular metal strip. In the width direction, the dimensions of the two serpentine metal strips are the same as those of the rectangular metal strip, i.e., attached... Figure 5 L in Figure (a) ks The axis of symmetry between the two serpentine metal sheets is parallel to the width direction.

[0050] The geometric center of the rectangular metal sheet, the geometric center of the two metal circuit layers, and the geometric center of the KK dielectric layer 7 are all located on the axis of the metal column (9).

[0051] The two metal circuit layers are a first metal circuit layer 8 and a second metal circuit layer 11. The first metal circuit layer 8 is rotated 180° about its geometric center in its own plane and then aligned with the second metal circuit layer 11 in the axial direction of the metal column 9. The upper and lower ends of the metal column 9 are connected to the first metal circuit layer 8 and the second metal circuit layer 11, respectively.

[0052] The periodic arrangement is as follows: The KK medium layer includes four trapezoidal KK medium units. The four trapezoidal KK medium units are closely arranged around the center of the upper surface of the antenna substrate to form a square ring, and cover the area except for the inner square area of ​​the square ring, forming a KK medium layer with a square ring tangential section. Each trapezoidal KK medium unit includes multiple KK medium blocks. Within the trapezoidal area where the same trapezoidal KK medium unit is located, the KK medium blocks are closely arrayed along the two sides of the KK medium layer, and the long side of each KK medium block is arranged along the direction parallel to the bottom side of the trapezoidal area.

[0053] Using the base direction of the trapezoidal region as the row direction and the geometric height direction of the trapezoidal region as the column direction, the number of rows of KK media in each trapezoidal KK media unit is determined by the width of the square ring and the width of the KK media block. Within each row of KK media blocks, the number of KK media blocks decreases progressively from the longer side to the shorter side of the trapezoidal region. Within the same trapezoidal KK media unit, the length direction of the KK media block is parallel to the two parallel sides of the trapezoidal KK media unit.

[0054] The KK medium layer also includes several medium-air mixing medium units. All medium-air mixing medium units are triangular pyramids, with the edges of the pyramids parallel to the axis of the metal column 9. All medium-air mixing medium units are arranged along the four inner walls of the KK medium layer, forming serrated protrusions on the four inner walls of the KK medium layer. Each medium-air mixing medium unit has one side that fits against the corresponding inner wall, and adjacent medium-air mixing medium units share an edge.

[0055] The antenna substrate includes an antenna dielectric layer 3, a feed axis 4, a microstrip slot patch 5, and a ground metal layer 6. The ground metal layer 6 is disposed on the lower surface of the antenna dielectric layer 3, and the feed axis 4 is vertically disposed inside the antenna dielectric layer 3. The upper and lower ends of the feed axis 4 are connected to the microstrip slot patch 5 and the ground metal layer 6, respectively. The upper surface of the antenna dielectric layer 3 is square in shape, and a microstrip slot patch 5 is disposed at its center. A slot is provided at the center of the microstrip slot patch 5, which is located vertically and along one of the diagonals of the microstrip slot patch 5. The horizontal cross-section of the microstrip slot patch 5 is square, and the horizontal cross-section of the slot is rectangular. The two sides of the microstrip slot patch 5 are parallel to the two sides of the antenna dielectric layer 3. A spatial KK medium layer 2 is laid on the upper surface of the antenna dielectric layer 3, and four trapezoidal KK medium elements in the same KK medium layer are respectively disposed on the four sides of the microstrip slot patch 5.

[0056] The center of the antenna dielectric layer 3, the microstrip slot patch 5, the center of the ground metal layer 6, and the center of all spatial KK dielectric layers 2 are located on the axis of the feed axis 4.

[0057] The spatial KK medium layer 2 also includes several air layers 10, all of which have the same thickness; an air layer 10 is arranged above and below each KK medium layer, and the air layer 10 covers the surface of the corresponding KK medium layer and is arranged in close contact with the corresponding KK medium layer.

[0058] Furthermore, in practice, the number of KK media layers is not fixed and needs to be adjusted according to changes in the size and shape of the antenna.

[0059] Thickness of KK medium layer (thickness h of KK medium block) k0 It is less than one-quarter of the operating wavelength of the antenna substrate.

[0060] The relative permittivity distribution ε of all spatial KK medium layers 2 in any tangential plane rz (d) Satisfies the following formula:

[0061]

[0062] Where, ω L The Lorentz resonant frequency of the KK medium layer 2 in space;

[0063] ω p The plasma frequency of the space KK medium layer 2 at the Lorentz resonant frequency;

[0064] γ is the damping coefficient of the spatial KK medium layer 2 at the Lorentz resonant frequency;

[0065] q is the relative permittivity ε of the space KK medium layer 2. rz Rate of change with d;

[0066] d is the distance between any location and the center of the spatial KK medium layer 2;

[0067] ω0 is the operating frequency of antenna element 1;

[0068] i is the imaginary unit;

[0069] Wherein, the rate of change q of the relative permittivity along the radial linear direction is:

[0070] q=ω0 / λ0

[0071] Where ω0 is the operating frequency of antenna element 1, and λ0 is the free space wavelength corresponding to ω0.

[0072] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. However, this invention is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this invention.

[0073] The principle of this invention is as follows:

[0074] Unlike the absorption mechanism of traditional absorbers, KK medium is a spatially non-uniform material. Surface waves can be regarded as a special plane wave with a wave vector greater than that of free space. Therefore, the spatial KK medium layer also has omnidirectional non-reflective absorption characteristics for surface waves. It is only necessary to ensure that the electromagnetic parameters of the surface wave at the point where it enters the spatial KK medium are equal to those of free space. Impedance and wave vector issues do not need to be considered.

[0075] The waveguide method was used to simulate the omnidirectional absorption characteristics of surface waves in a spatial KK medium layer. For example... Figure 4 As shown, a theoretical model of the spatial KK medium layer is constructed. In the theoretical model of the spatial KK medium layer, taking the profile height h of the theoretical model of the spatial KK medium layer KK = 0.1λ0, and the length t KK = 1λ0 (y1 ≤ y < y2, y1 = 0.5λ0, y2 = 1.5λ0). The theoretical model of the spatial KK medium layer here is an anisotropic medium, where ε rx = ε ry = μ rx = μ ry = μ rz = 1, while ε rz along the y direction needs to satisfy the KK relation, and this relation can be obtained by calculating from the following formula:

[0076]

[0077] where ω p is the plasma frequency of the theoretical model of the spatial KK medium layer at the Lorentz resonance frequency. At this time, ω p = 1.5ω0, ω L is the Lorentz resonance frequency of the theoretical model of the spatial KK medium layer. At this time, ω L = 2ω0, γ is the damping coefficient of the theoretical model of the spatial KK medium layer at the Lorentz resonance frequency. At this time, γ = 0.2ω0, q is the change rate of the relative permittivity of the theoretical model of the spatial KK medium layer along the y direction, ω0 is the operating frequency of the antenna, and i is the imaginary unit;

[0078] q = ω0 / λ0

[0079] where ω0 is the operating frequency of the antenna, and λ0 is the free space wavelength at the operating frequency of ω0.

[0080] The results of simulating and verifying the theoretical model of the spatial KK medium layer are as follows:

[0081] When the incident angles θ (0°, 30° and 60°) of the surface wave are different, the curves of the surface wave absorption rate, reflection rate and transmittance of the theoretical model of the spatial KK medium layer changing with frequency are as Figure 2 shown. When at different profile heights h KK , the curves of the surface wave absorption rate, reflection rate and transmittance of the theoretical model of the spatial KK medium layer changing with frequency are as Figure 3 shown. Combining Figure 2 and Figure 3 it can be clearly seen that as the profile height of the theoretical model of the spatial KK medium layer increases, the surface wave absorption rate also gradually increases. When the profile height h KKWith a wavelength of 0.1λ0, the space KK medium layer exhibits an absorption rate of over 90% for incident waves near frequency ω0, and increasing the incident angle has almost no effect on the absorption rate. Therefore, the space KK medium layer possesses omnidirectional, non-reflective absorption properties for surface waves propagating along the dielectric substrate surface, effectively suppressing surface waves propagating along the antenna dielectric substrate and thus improving antenna performance.

[0082] Specific embodiments of the present invention are as follows:

[0083] This invention takes a circularly polarized antenna in the microwave band as an example. Figure 1 As shown, this embodiment mainly consists of an antenna substrate and a spatial KK medium layer 2. The spatial KK medium layer 2 is arranged on the upper surface of the antenna substrate. The spatial KK medium layer 2 includes three KK medium layers, which are supported by a foam board (air layer 10) with a dielectric constant close to that of air. The thickness of the foam board is 0.9 mm.

[0084] The antenna substrate includes an antenna dielectric layer 3, a feed axis 4, a microstrip slot patch 5, and a ground metal layer 6 on the lower surface of the antenna dielectric layer 3. The microstrip slot patch 5 and the ground metal layer 6 are connected by the feed axis 7. A slot is vertically formed on the top surface of the microstrip slot patch 5, and the slot is arranged along one of the diagonals of the microstrip slot patch 5. The horizontal cross-section of the microstrip slot patch 5 is square, and the horizontal cross-section of the slot is rectangular. The feed axis 4 is a cylinder.

[0085] The specific structural parameters of the antenna substrate are as follows:

[0086] The length of the antenna dielectric layer 3 is W0 = 180 mm, the width of the antenna dielectric layer 3 is L0 = 180 mm, the thickness of the antenna dielectric layer 3 is h = 2 mm, the length of the microstrip slot patch 5 is W1 = 8.1 mm, the width of the microstrip slot patch 5 is L1 = 8.1 mm, the length of the rectangular slot is W2 = 4.45 mm, the width of the rectangular slot is L2 = 0.45 mm, the distance from the feed axis 4 to the boundary of the microstrip slot patch is d = 1.4 mm, and the radius of the feed axis 4 is R0 = 0.4 mm.

[0087] Each KK media layer consists of several KK media blocks with the same shape and size. Figure 1 (Ⅳ) is a three-dimensional view of the KK medium block and the air layers 10 located above and below it, as shown in the figure. Figure 1As shown in (III), each KK medium block includes a KK dielectric layer 7, two metal circuit layers (a first metal circuit layer 8 and a second metal circuit layer 11) located on the upper and lower surfaces of the KK dielectric layer 7 respectively, and metal pillars 9 connecting the two metal circuit layers. Each metal circuit layer includes a rectangular metal sheet and two serpentine metal sheets. The rectangular metal sheet is arranged in the center of the metal circuit layer, and the two serpentine metal sheets are symmetrically arranged on both sides of the rectangular metal sheet. One end of each of the two serpentine metal sheets extends towards the rectangular metal sheet and is connected to the two sides of the same end of the rectangular metal sheet.

[0088] Figure 1 (III) is a top view and a side view of an antenna loaded with a space KK medium layer, as shown. Figure 1 As shown in (III), each KK medium layer has a centrosymmetric structure. Within the same KK medium layer, several KK medium blocks are closely arranged to form a square ring. A top view of the spatial KK medium layer / KK medium layer is shown below. Figure 1 As shown in the blue area of ​​(III), the square ring can be divided into four centrally symmetrical trapezoidal KK medium units along the diagonal (the line connecting the two corresponding vertices of the inner and outer squares). The top view of the trapezoidal KK medium unit is trapezoidal. In the side view (right), the blue area illustrates the arrangement relationship between the spatial KK medium layer 2 and the antenna substrate. The thickness of the blue area is the thickness of the spatial KK medium layer 2.

[0089] Figure 1 (II) is a top view of one column of KK media blocks. Each trapezoidal KK media unit consists of 14 rows of KK media blocks. The number of KK media blocks in each row decreases regularly from the outside to the inside (i.e., from the long side to the short side of the trapezoidal KK media unit), and they are aligned one by one along the geometric height of the trapezoidal KK media unit (the direction perpendicular to the long and short sides of the trapezoidal KK media unit). In the same trapezoidal KK media unit, the length direction of the KK media blocks is parallel to the two parallel sides of the trapezoidal KK media unit. The specific arrangement is as follows: Figure 1 (V) is shown.

[0090] like Figure 1 As shown in (II), the space KK medium layer 2 also includes several medium-air mixing medium units with the same shape and size. The inner side of each trapezoidal KK medium unit (near the microstrip slot patch 5) is provided with medium-air mixing medium to achieve matching between the space KK medium layer 2 and air. The medium-air mixing medium unit is shaped like a triangular pyramid, with all three lateral edges of the pyramid parallel to the axis of the metal column 9. The top and bottom surfaces of the pyramid are both equilateral triangles (as shown in the attached diagram). Figure 1 (As shown in Figure II). In the same KK medium layer, the inner walls of the four trapezoidal KK medium units are respectively arranged with four rows of medium-air mixing medium units with a sawtooth-shaped protrusion structure.

[0091] The specific structural parameters of the space KK medium layer 2 are as follows:

[0092] The distance h from the top surface of the space KK medium layer 2 to the top surface of the antenna dielectric substrate KK =9mm (e.g.) Figure 1 (as shown in Figure (Ⅲ));

[0093] The thickness h of air layer 10 k1 =0.9mm;

[0094] The length W of the KK medium block k0 =8mm, the width d of the KK medium block k =4mm, thickness h of KK medium block k0 =1.2mm;

[0095] The overall length W of the metal circuit layers (first metal circuit layer 8, second metal circuit layer 11) in the KK medium block ks = 5.82mm, overall width L ks =2.25mm;

[0096] In the metal circuit layers (first metal circuit layer 8, second metal circuit layer 11) of the KK medium block, the width W of the serpentine metal sheet... k1 =0.25mm, the distance g between adjacent bent segments in the serpentine metal sheet k =0.25mm;

[0097] In the KK medium block, the radius of the metal pillar 7 is R. k =0.4mm.

[0098] The distance t between the two parallel sides of the trapezoidal KK medium unit KK =60mm (e.g.) Figure 1 (as shown in Figure (II));

[0099] The feed axis 4, microstrip slot patch 5, and grounding metal layer 6 of the antenna substrate are all made of copper, with a conductivity of 5.96 × 10⁻⁶. 7 S / m.

[0100] The relative permittivity of the antenna dielectric layer 3 is 10.2, and the loss tangent is 0.002.

[0101] In the KK medium layer, the first metal circuit layer 8, the second metal circuit layer 11, and the metal pillars 9 are all made of copper, with a conductivity of 5.96 × 10⁻⁶. 7 S / m.

[0102] In the KK dielectric layer, the KK dielectric layer 7 is made of F4B, which has a relative permittivity of 3.5 and a loss tangent of 0.003.

[0103] The dielectric constant of air layer 10 is 1, and its permeability is 1.

[0104] Based on this embodiment, simulation tests were conducted on the dielectric constant distribution of the KK medium block. Simulation tests were also performed on antennas without the spatial KK medium layer 2 (simulation-antenna), antennas with the spatial KK medium layer 2 (simulation-antenna + KK dielectric), and antennas with a high-impedance structure (simulation-antenna + high-impedance structure). Experimental tests were also conducted on antennas without the spatial KK medium layer 2 (simulation-antenna) and antennas with the spatial KK medium layer 2 (simulation-antenna + KK dielectric). The test results are as follows:

[0105] Figure 5 , Figure 6 The equivalent constitutive parameter curves and discretized dielectric constant distribution curves obtained by inverting the KK medium block are shown respectively.

[0106] The simulation process is as follows: The KK medium block is simulated using CST simulation software in the frequency range of 4.0–5.5 GHz. Periodic boundary conditions are set in both the height and length directions of the KK medium block, extending the element into an infinitely large plane. The incident electromagnetic wave propagates along the width direction of the KK medium block, and the electric field polarization direction is parallel to the height direction. Figure 5 As shown, the KK dielectric block can achieve Lorentz resonance near 5 GHz. This is achieved by changing the overall length W of the metal circuit layers (first metal circuit layer 8, second metal circuit layer 11) in the KK dielectric block. ks (While keeping other parameters constant) Adjust the Lorentz resonant frequency of the KK medium block to achieve a dielectric constant distribution that varies along the width direction and satisfies the KK relationship (e.g., Figure 6 As shown in the figure, by fitting the discretized dielectric constant distribution, it can be seen that the fitted dielectric constant satisfies the spatial KK relationship distribution.

[0107] Figure 7 The diagram shows a comparison of the simulation and test results of the surface wave suppression antenna based on a spatial KK medium layer according to an embodiment of the present invention. As can be seen from the simulation results of the high-impedance antenna, the antenna S-parameters remain almost unchanged before and after loading the spatial KK medium layer 2. Therefore, loading the spatial KK medium layer 2 has no effect on the antenna resonance, which is mainly attributed to the omnidirectional non-reflective absorption characteristics of the spatial KK medium layer for surface waves.

[0108] Figure 8 The diagram shows a comparison of simulation and test results of the axial ratio as a function of frequency at the location directly above the radiation of the surface wave suppression antenna based on a spatial KK medium layer, according to an embodiment of the present invention. The results indicate that loading the spatial KK medium layer 2 can effectively improve the circular polarization radiation performance of the antenna.

[0109] Figure 9 and Figure 10 The simulation and test results of the surface wave suppression antenna based on a spatial KK medium layer according to the embodiments of the present invention are shown in the comparison graphs of the axial ratio in the xz and yz planes as a function of angle. The results show that after loading the spatial KK medium layer 2 (antenna + KK medium), the 3dB axial ratio beamwidth of the antenna in the xz and yz planes increases by approximately 30° and 15°, respectively. Although the tested circular polarization performance deteriorates to some extent in a few radiation directions, the broadening of the 3dB axial ratio beamwidth of the antenna after the spatial KK medium layer is still visible, further demonstrating that the spatial KK medium layer can effectively improve the circular polarization radiation performance of the antenna.

[0110] Figure 11 This invention demonstrates the surface wave suppression antenna based on a spatial KK medium layer at its resonant frequency (4.9 GHz) in the xz plane (...). Figure 11 (a) and yz plane ( Figure 11 (b) Comparison of antenna simulation and test patterns. Test results show that loading the spatial KK medium layer 2 can effectively reduce the antenna's back radiation, reducing the antenna back lobe by approximately 5 dB. The antenna gains before and after loading the spatial KK medium layer, obtained from tests (simulations), are 4.3 dBi and 3.8 dBi (4.5 dBi and 4.1 dBi), respectively, proving that loading the spatial KK medium layer has little impact on the antenna gain. The radiation patterns of the surface wave suppression antenna based on the high-impedance structure are also compared in the figure. It can be seen that although loading the high-impedance structure can also effectively suppress the antenna's back radiation, the reflection of surface waves causes severe distortion of the antenna pattern. Although there are some errors between the test and simulation results for the axial ratio and radiation pattern, they are still sufficient to show that loading the spatial KK medium layer can effectively improve the antenna's various radiation performance characteristics.

[0111] The operating frequency of the spatial KK medium layer in this embodiment of the invention is 5 GHz. In reality, this invention can arbitrarily customize frequencies between the microwave and terahertz bands; the microwave band is simply chosen for demonstration purposes. To enable the invention to operate at other frequencies, the unit structure dimensions can be changed.

[0112] The spatial KK medium layer in this embodiment of the invention can also be applied to other antennas; this invention simply selects a circularly polarized antenna as an example. In fact, the spatial KK medium layer design method proposed in this invention is suitable for microstrip antennas of any frequency band, especially broadband microstrip antennas. This invention is not intended to limit the scope of the invention in any way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content, resulting in equivalent examples. However, any simple modifications, equivalent changes, and alterations made to the above examples based on the technical essence of this invention, without departing from the scope of the invention, still fall within the scope of the invention.

Claims

1. A surface wave suppression antenna based on a spatial Kramers-Kronig medium, characterized in that: The surface wave suppression antenna includes at least one antenna element (1), each antenna element (1) includes an antenna substrate and a spatial KK medium layer (2), the spatial KK medium layer (2) is laid on the upper surface of the antenna substrate, the spatial KK medium layer (2) includes at least one KK medium layer, the KK medium layer is formed by a number of KK medium blocks with the same shape and size arranged periodically; the KK medium block includes a KK dielectric layer (7), a metal pillar (9) and two metal circuit layers, the two metal circuit layers are respectively located on the top and bottom surfaces of the KK dielectric layer (7), the metal pillar (9) is arranged inside the KK dielectric layer (7), and the two ends of the metal pillar (9) are respectively connected to the two metal circuit layers.

2. The surface wave suppression antenna based on spatial Kramers-Kronig medium according to claim 1, characterized in that: Each metal circuit layer includes a rectangular metal sheet and two serpentine metal sheets; the rectangular metal sheet is arranged in the center of the metal circuit layer, and the two serpentine metal sheets are arranged on both sides of the rectangular metal sheet. The two serpentine metal sheets are symmetrically arranged relative to the rectangular metal sheet. One end of the serpentine metal sheet extends towards the rectangular metal sheet and connects to it. The two serpentine metal sheets are connected to the same end of the rectangular metal sheet. The geometric center of the rectangular metal sheet, the geometric center of the two metal circuit layers and the geometric center of the KK dielectric layer (7) are all located on the axis of the metal pillar (9).

3. The surface wave suppression antenna based on spatial Kramers-Kronig medium according to claim 2, characterized in that: The two metal circuit layers are a first metal circuit layer (8) and a second metal circuit layer (11); after the first metal circuit layer (8) is rotated 180° about the center, it is aligned with the second metal circuit layer (11) in the axial direction of the metal column (9), and the upper and lower ends of the metal column (9) are connected to the first metal circuit layer (8) and the second metal circuit layer (11) respectively.

4. The surface wave suppression antenna based on spatial Kramers-Kronig medium according to claim 1, characterized in that: The periodic arrangement is as follows: the KK medium layer includes four trapezoidal KK medium units. The cross-section of the four trapezoidal KK medium units in the radial direction of the metal column (9) is an isosceles trapezoid, and the cross-section of the KK medium layer in the radial direction of the metal column (9) is a square ring. The four trapezoidal KK medium units are arranged closely around the center of the antenna substrate to form a square ring. Each trapezoidal KK medium unit includes multiple KK medium blocks. In the trapezoidal region where the same trapezoidal KK medium unit is located, the KK medium blocks are arranged closely in an array along the two sides of the KK medium layer, and the long side of each KK medium block is arranged along the direction parallel to the bottom side of the trapezoidal region.

5. The surface wave suppression antenna based on spatial Kramers-Kronig medium according to claim 4, characterized in that: The KK medium layer also includes several medium-air mixing medium units. All medium-air mixing medium units are triangular pyramids in shape. The direction of the triangular pyramid is parallel to the axis of the metal column (9). All medium-air mixing medium units are arranged along the four inner walls of the KK medium layer, forming serrated protrusions on the four inner walls of the KK medium layer. Each medium-air mixing medium unit has one side that fits against the corresponding inner wall, and two adjacent medium-air mixing medium units share the same edge.

6. The surface wave suppression antenna based on spatial Kramers-Kronig medium according to claim 4, characterized in that: The antenna substrate includes an antenna dielectric layer (3), a feed axis (4), a microstrip slot patch (5), and a ground metal layer (6). The feed axis (4) is vertically arranged inside the antenna dielectric layer (3). The upper and lower ends of the feed axis (4) are connected to the microstrip slot patch (5) and the ground metal layer (6), respectively. The ground metal layer (6) is located on the lower surface of the antenna dielectric layer (3), and the microstrip slot patch (5) is located on the upper surface of the antenna dielectric layer (3). The microstrip slot patch (5) and the antenna dielectric... The upper surface of layer (3) is square in shape. The microstrip slot patch (5) is arranged at the center of the upper surface of the antenna dielectric layer (3). The center of the microstrip slot patch (5) is provided with a slot. The two sides of the microstrip slot patch (5) are parallel to the two sides of the antenna dielectric layer (3). The spatial KK medium layer (2) is laid on the upper surface of the antenna dielectric layer (3). The four trapezoidal KK medium units in the same KK medium layer are respectively arranged on the four sides of the microstrip slot patch (5).

7. The surface wave suppression antenna based on spatial Kramers-Kronig medium according to claim 1, characterized in that: The spatial KK medium layer (2) also includes several air layers (10), all of which have the same thickness; an air layer (10) is arranged above and below each KK medium layer; the dielectric constant of the air layer (10) is 1 and the permeability is 1.

8. The surface wave suppression antenna based on spatial Kramers-Kronig medium according to claim 1, characterized in that: The thickness of the KK medium layer is less than one-quarter of the operating wavelength of the antenna substrate.

9. The surface wave suppression antenna based on spatial Kramers-Kronig medium according to claim 1, characterized in that: The material of the KK dielectric layer (7) is F4B, with a relative permittivity of 3.5 and a loss tangent of 0.

003.

10. The surface wave suppression antenna based on spatial Kramers-Kronig medium according to claim 1, characterized in that: The relative permittivity distribution ε of all spatial KK media layers (2) on any tangential plane rz (d) Satisfies the following formula: Where, ω L The Lorentz resonant frequency of the space KK medium layer (2) is given by . ω p The plasma frequency of the space KK medium layer (2) at the Lorentz resonant frequency; γ is the damping coefficient of the spatial KK medium layer (2) at the Lorentz resonant frequency; q is the relative permittivity ε of the space KK medium layer (2). rz The rate of change; d is the distance from the center of the spatial KK medium layer (2); ω0 is the operating frequency of antenna element (1); i is the imaginary unit; Wherein, the rate of change q of the relative permittivity along the radial linear direction is: q=ω0 / λ0 Where ω0 is the operating frequency of antenna element (1) and λ0 is the free space wavelength corresponding to ω0.

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