Circularly polarized antenna with RCS suppression characteristic

Abstract

The invention discloses a circularly polarized antenna with an RCS (radar cross section) suppression characteristic in the field of antennas. The circularly polarized antenna comprises a first dielectric substrate and a second dielectric substrate which are stacked, a metasurface structure array is arranged on the first dielectric substrate; the metasurface structure array comprises a plurality of distributed metasurface units; the plurality of first metal patches are arranged to form a convex metasurface module, and the plurality of second metal patches are arranged to form a concave metasurface module; the convex metasurface module is embedded into the concave metasurface module to form a metasurface unit; a metal floor is arranged between the first dielectric substrate and the second dielectric substrate; the metal floor is provided with a coupling slot; one side, far away from the first dielectric substrate, of the second dielectric substrate is provided with a sequential rotation feed network; energy is input by the sequential rotation feed network, and the metasurface structure is excited through the coupling gap to form a radiation signal; good radiation performance is still kept on the premise that the radar cross section of the antenna is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of radiating antennas, and in particular relates to a circularly polarized antenna with RCS suppression characteristics. Background Art

[0002] Antennas not only have radiation characteristics but also scattering characteristics. In some combat platforms with high stealth requirements, in addition to paying attention to the radar cross section (RCS) of the platform's own structure, the antenna loaded on the platform is an important scattering source, and the RCS it generates cannot be ignored.

[0003] With the increasing requirements for stealth, reducing the RCS of antennas has received widespread attention. Stealth refers to a system platform or antenna structure with a small radar cross section, which makes it impossible for enemy radars to receive the echo of the detected object, thus achieving stealth. Generally speaking, the radiation and scattering capabilities of antennas have an important internal connection, so it is difficult for existing technologies to maintain good radiation performance while reducing the radar cross section of the antenna. Summary of the invention

[0004] The object of the present invention is to provide a circularly polarized antenna with RCS suppression characteristics, so as to achieve the goal of taking into account both RCS suppression and good radiation performance.

[0005] To achieve the above object, the present invention provides:

[0006] A circularly polarized antenna with RCS suppression characteristics, comprising a first dielectric substrate and a second dielectric substrate which are stacked; a metasurface structure array is arranged on a side of the first dielectric substrate away from the second dielectric substrate; the metasurface structure array comprises a plurality of distributed metasurface units;

[0007] A plurality of first metal patches and a second metal patch are arranged in the super surface unit, wherein the plurality of first metal patches are arranged to form a convex-shaped super surface module, and the plurality of second metal patches are arranged to form a concave-shaped super surface module; the convex-shaped super surface module is embedded in the concave-shaped super surface module to form a super surface unit;

[0008] A metal floor is provided between the first dielectric substrate and the second dielectric substrate; a coupling slot is provided on the metal floor; a sequential rotating feeding network is provided on a side of the second dielectric substrate away from the first dielectric substrate; energy is input by the sequential rotating feeding network, and the metasurface structure is excited through the coupling slot to form a radiation signal.

[0009] Furthermore, the first metal patch and the second metal patch include a connecting portion, and arrows with opposite directions are respectively provided at both ends of the connecting portion; the direction of the arrow on the first metal patch and the direction of the arrow on the second metal patch are perpendicular to each other.

[0010] Furthermore, the size of the first metal patch is greater than the size of the second metal patch; in the present invention, the ratio of the size of the second metal patch to the size of the first metal patch is equal to 0.75.

[0011] Furthermore, the metasurface structure array is composed of 2×2 metasurface units; the metasurface unit is a 4×4 matrix formed by a first metal patch and a second metal patch.

[0012] Furthermore, in the metasurface structure array, the protruding directions of the convex-shaped metasurface modules in two adjacent metasurface units differ by 90 degrees, and the protruding directions of the convex-shaped metasurface modules in two diagonally distributed metasurface units differ by 180 degrees.

[0013] Furthermore, four coupling slots are provided on the metal floor, and the coupling slots are arranged in a Z shape, and the four coupling slots of the Z shape are centrally symmetrically distributed; the coupling slots are arranged in a one-to-one correspondence with the super surface units; the center point of the coupling slot overlaps with the vertical projection of the center point of the super surface unit.

[0014] Furthermore, the coupling slot comprises a first section of coupling sub-slots, a second section of coupling sub-slots and a third section of coupling sub-slots; the first section of coupling sub-slots and the second section of coupling sub-slots, the second section of coupling sub-slots and the third section of coupling sub-slots are perpendicular to each other, and the first section of coupling sub-slots and the third section of coupling sub-slots are parallel to each other; the first section of coupling sub-slots, the second section of coupling sub-slots and the third section of coupling sub-slots are connected in sequence to form a Z shape; the ends of the first section of coupling sub-slots and the third section of coupling sub-slots are provided with rectangular coupling sub-slots, Y-shaped coupling sub-slots or fan-shaped coupling sub-slots.

[0015] Furthermore, the sequential rotation feeding network is provided with a plurality of microstrip lines; the microstrip lines are arranged in one-to-one correspondence with the coupling slots, and the microstrip lines intersect perpendicularly with the projection of the second coupling sub-slot; the microstrip lines are provided with a fan-shaped output end, and the fan-shaped output end is arranged relative to the center point of the coupling slot.

[0016] Furthermore, it also includes a non-metallized through hole, which passes through the first dielectric substrate, the metal floor and the second dielectric substrate; a plurality of non-metallized through holes are respectively distributed at the corners of the first dielectric substrate and the second dielectric substrate; the diameter range r of the non-metallized through hole is [2mm, 3mm]; nylon screws are arranged in the non-metallized through hole, and the first dielectric substrate and the second dielectric substrate are fixed by the nylon screws.

[0017] Furthermore, the dielectric constants of the first dielectric substrate and the second dielectric substrate are in the range of [1, 10]; the thickness h1 of the first dielectric substrate and the thickness h2 of the second dielectric substrate are in the range of [0.001λ0, 0.1λ0]; λ0 is the free space wavelength.

[0018] Furthermore, the gap width g between two adjacent first metal patches in the metasurface unit is in the range of ; The side length w of the first metal patch is in the range of [0.2λ g1 ,0.4λ g1 ], the arrow side cut range is [0.2λ g1 ,0.4λ g1 ], the width v of the connection is in the range of [0.2λ g1 ,0.4λ g1 ], where λ g1 is the dielectric effective wavelength of the first dielectric substrate.

[0019] Furthermore, the side length W of the metal floor G The range is [λ0,2λ0]; the total length range of the coupling gap is is [0.5λ g2 ,2λ g2 ], the width of the coupling gap ranges from [0.05λ g2 ,0.4λ g2 ], where λ0 is the free space wavelength, λ g2 is the dielectric effective wavelength of the second dielectric substrate.

[0020] Furthermore, the width w of the microstrip line on the feed network is sequentially rotated f The range is [0.1λ g2 ,0.5λ g2 ]; The spacing S of the fan-shaped output terminals on the sequential rotary feed network ranges from [0.1λ g2 ,0.4λ g2 ], the fan angle range is [45°, 90°], where λ g2 is the dielectric effective wavelength of the second dielectric substrate.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The metasurface unit described in the present invention is provided with a plurality of first metal patches and a second metal patch, wherein the plurality of first metal patches are arranged to form a convex-shaped metasurface module, and the plurality of second metal patches are arranged to form a concave-shaped metasurface module; the convex-shaped metasurface module is embedded in the concave-shaped metasurface module to form a metasurface unit; the first metal patch and the second metal patch in the metasurface unit are mixedly arranged, which can realize RCS suppression within a wider frequency band, and realize radiation within a wider frequency band through a sequentially rotating feeding network; compared with traditional radiating antennas, the present invention has the characteristics of broadband, circular polarization, RCS suppression and low profile. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A top view of the circularly polarized antenna provided in this embodiment;

[0024] Figure 2 A side view of the circularly polarized antenna provided in this embodiment;

[0025] Figure 3 A structural diagram of the metal floor provided in this embodiment;

[0026] Figure 4 A structural diagram of a sequential rotation feeding network provided for this embodiment;

[0027] Figure 5 The S parameter characteristic diagram of the circularly polarized antenna provided in this embodiment;

[0028] Figure 6 Axis ratio characteristic diagram of the circularly polarized antenna provided in this embodiment;

[0029] Figure 7 A gain characteristic diagram of the circularly polarized antenna provided in this embodiment;

[0030] Figure 8 A scattering suppression diagram of the circularly polarized antenna provided in this embodiment;

[0031] Fig. 9 The radiation pattern of the circularly polarized antenna provided in this embodiment;

[0032] Fig.10 The scattering pattern of the circularly polarized antenna provided in this embodiment when the incident wave is X-polarized;

[0033] Fig.11 The scattering pattern of the circularly polarized antenna provided in this embodiment when the incident wave is Y-polarized;

[0034] In the figure: 1 is the first dielectric substrate, 2 is the second dielectric substrate, 3 is the metasurface unit, 4 is the first metal patch, 5 is the convex metasurface module, 6 is the second metal patch; 7 is the metal floor; 8 is the coupling gap, 81 is the first section of the coupling sub-gap, 82 is the second section of the coupling sub-gap, 83 is the third section of the coupling sub-gap, 84 is the rectangular coupling sub-gap, 9 is the sequential rotation feeding network, 91 is the microstrip line, 92 is the fan-shaped output end, 10 is the non-metallized through hole, and 11 is the concave metasurface module. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0036] It should be noted that in the description of the present invention, the directions or positional relationships indicated by the terms "front", "rear", "left", "right", "up", "down", "inside", "outside", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. The terms "front", "rear", "left", "right", "up", and "down" used in the description of the present invention refer to the directions in the accompanying drawings, and the terms "inside" and "outside" refer to the directions toward or away from the geometric center of a specific component, respectively.

[0037] like Figures 1 to 4 As shown, a circularly polarized antenna with RCS suppression characteristics includes a first dielectric substrate 1 and a second dielectric substrate 2 that are stacked; a metasurface structure array is arranged on a side of the first dielectric substrate 1 away from the second dielectric substrate 2; the metasurface structure array includes a plurality of distributed metasurface units 3; the metasurface structure array in this embodiment is composed of 2×2 metasurface units 3.

[0038] The metasurface unit 3 is provided with a plurality of first metal patches 4 and second metal patches 6, and the number of the first metal patches 4 and the second metal patches 6 in each metasurface unit is equal. In the present embodiment, the metasurface unit is a 4×4 matrix formed by the first metal patch 4 and the second metal patch 6; the first metal patch 4 and the second metal patch 6 include a connecting portion, and arrows in opposite directions are respectively provided at both ends of the connecting portion; the direction of the arrow on the first metal patch is perpendicular to the direction of the arrow on the second metal patch; in the present embodiment, RCS suppression is performed by offsetting the phase difference between the direction of the arrow on the first metal patch 4 and the direction of the arrow on the second metal patch 6.

[0039] The size of the first metal patch 4 is larger than that of the second metal patch 6; in the present invention, the ratio of the size of the second metal patch 6 to the size of the first metal patch 4 is equal to 0.75. The polarization twist bandwidths of the metal patches of 1 times and 0.75 times are basically overlapped, so although the two are of different sizes and in opposite directions, scattering suppression can also be achieved.

[0040] A number of first metal patches 4 are arranged to form a convex metasurface module 5, and a number of second metal patches 6 are arranged to form a concave metasurface module 11; the convex metasurface module 5 is embedded in the concave metasurface module 11 to form a metasurface unit 3. In the metasurface structure array, the protruding directions of the convex metasurface modules 5 in two adjacent metasurface units 3 differ by 90 degrees, and the protruding directions of the convex metasurface modules 5 in two diagonally distributed metasurface units 3 differ by 180 degrees. For metasurface units of the same size, the resonance frequency is the same, but the radiation will be canceled out if they are in opposite directions. However, if the resonance frequency is reduced to 0.75 times, the second metal patch 6 will not affect the radiation of the first metal patch 4, thus ensuring the high radiation performance of the antenna.

[0041] A metal floor 7 is provided between the first dielectric substrate 1 and the second dielectric substrate 2; four coupling slots 8 are provided on the metal floor 7, and the coupling slots 8 are arranged in a Z shape, and the four coupling slots 8 in the Z shape are centrally symmetrically distributed; the coupling slots 8 are arranged in a one-to-one correspondence with the metasurface units 3; the center point of the coupling slot 8 overlaps with the vertical projection of the center point of the metasurface unit 3.

[0042] The coupling slot 8 comprises a first coupling sub-slot 81, a second coupling sub-slot 82 and a third coupling sub-slot 83; the first coupling sub-slot 81 and the second coupling sub-slot 82, the second coupling sub-slot 82 and the third coupling sub-slot 83 are perpendicular to each other, and the first coupling sub-slot 81 and the third coupling sub-slot 83 are parallel to each other; the first coupling sub-slot 81, the second coupling sub-slot 82 and the third coupling sub-slot 83 are connected in sequence to form a Z shape; in this embodiment, the ends of the first coupling sub-slot 81 and the third coupling sub-slot 83 are both provided with rectangular coupling sub-slots 84, and the rectangular coupling sub-slot 84 can also be replaced by a Y-shaped coupling sub-slot or a fan-shaped coupling sub-slot.

[0043] A sequential rotation feeding network 9 is arranged on the side of the second dielectric substrate 2 away from the first dielectric substrate 1; a plurality of microstrip lines 91 are arranged on the sequential rotation feeding network 9; the microstrip lines 91 are arranged one-to-one with the coupling slots 8, and the microstrip lines 91 intersect perpendicularly with the projection of the second coupling sub-slot 8; a fan-shaped output end 82 is arranged on the microstrip line 91, and the fan-shaped output end 92 is arranged opposite to the center point of the coupling slot 8. Energy is input by the sequential rotation feeding network, and the metasurface structure is excited through the coupling slot to form a radiation signal.

[0044] The circularly polarized antenna also includes a non-metallized through hole 10, which passes through the first dielectric substrate 1, the metal floor 7 and the second dielectric substrate 2; a plurality of non-metallized through holes 10 are respectively distributed at the corners of the first dielectric substrate 1 and the second dielectric substrate 2; the diameter range r of the non-metallized through hole is [2mm, 3mm]; a nylon screw is arranged in the non-metallized through hole, and the first dielectric substrate and the second dielectric substrate are fixed by the nylon screw.

[0045] The dielectric constant range of the first dielectric substrate 1 and the second dielectric substrate 2 is [1, 10]; the thickness h1 of the first dielectric substrate 1 and the thickness h2 of the second dielectric substrate 2 Range is ; is the free space wavelength.

[0046] The gap width g between two adjacent first metal patches 4 in the super surface unit 3 is in the range of ; The side length w of the first metal patch 4 is in the range of , the arrow side cut range is , the width v of the connection ranges from ,in, is the dielectric effective wavelength of the first dielectric substrate 1.

[0047] The side length W of the metal floor 7 G Range is ; The cumulative total length of all coupling slots is n×(Ls1+2Ls2+2Ls3); The length Ls1 of a single coupling slot 8 is in the range of [0.5λ g2 ,2λ g2 ], the width Ws1 of the second coupling sub-slot 82 is in the range of [0.03λ g2 ,0.4λ g2 ], the width Ws2 of the first coupling sub-slot 81 and the third coupling sub-slot 83 is in the range of [0.03λ g2 ,0.3λ g2 ], the width of the rectangular coupling sub-slit Ws3 ranges from [0.03λ g2 ,0.3λ g2 ], where λg2 is the effective wavelength of the lower dielectric substrate, n is the number of coupling slots 8 in the metal floor; Ls1 represents the length of the second coupling sub-slot 82, Ls2 represents the length of the first coupling sub-slot 81 and the third coupling sub-slot 83, and Ls3 represents the length of the rectangular coupling sub-slot.

[0048] Sequential rotation of the width w of the microstrip line of the feeding network 9 f2 The range is [0.1λ g1 ,0.5λ g1 ]; the width w of the impedance transformation part of the microstrip line of the sequential rotation feeding network 9 f1 The range is [0.07λ g1 ,0.35λ g1 ]; the spacing S of the fan-shaped output terminals on the sequential rotary feed network ranges from [0.1λ g2 ,0.4λ g2 ], the fan angle range is [45°, 90°], where λ g2 is the dielectric effective wavelength of the second dielectric substrate.

[0049] The specific parameters in this embodiment are set as follows: the thickness h1 of the first dielectric substrate 1 is 3.25 mm, the thickness h2 of the second dielectric substrate 2 is 0.813 mm; the gap width g between two adjacent first metal patches in the metasurface unit is 0.4 mm, the side length w of the first metal patch is 7.2 mm, the arrow side cut range of the first metal patch is 4.5 mm, and the width v of the connecting portion is 4.3 mm; the side length W of the metal floor 6 is G is 76mm; the total length of the coupling gap 7 is 44.56mm;

[0050] The width Ws1 of the second coupling sub-gap 82 is 1.72 mm, corresponding to the length L S1 The width Ws2 of the first coupling sub-gap 81 and the third coupling sub-gap 83 is 1.72 mm, corresponding to the length L S2 is 5.28mm; the width of the rectangular coupling sub-gap Ws3 is 4mm, corresponding to the length L S3 The width w of the microstrip line of the sequentially rotating feeding network 9 is 3 mm. f2 The width w of the impedance transformation portion of the sequential rotation feed network 9 microstrip line is 1.8 mm; f1 The fan-shaped output terminal spacing S on the sequential rotary feeding network is 2.8mm, and the fan-shaped angle is 75°.

[0051] like Figure 5 As shown in FIG. 1 , the S parameter characteristic diagram of the circularly polarized antenna provided in the embodiment. It can be seen that |S 11The circular polarization working impedance bandwidth of |<-10dB is about 55.91% (5.27-9.36GHz). It can be seen from the above that the circular polarization antenna provided in the embodiment can effectively achieve the impedance broadband characteristic.

[0052] like Figure 6 As shown, the axial ratio characteristic diagram of the circularly polarized antenna provided in the embodiment. It can be seen that the circularly polarized working impedance bandwidth of AR<-3dB is about 40.74% (5.61-8.48GHz). From the above, it can be seen that the circularly polarized antenna provided in the embodiment can effectively achieve the axial ratio broadband characteristic.

[0053] like Figure 7 As shown, the gain characteristic diagram of the circularly polarized antenna provided in the embodiment. The peak value of the left-hand circularly polarized gain achieved over the entire working bandwidth is about 7.3dBi. As can be seen from the above, the metasurface result provided in the embodiment can effectively achieve a good gain characteristic.

[0054] like Figure 8 As shown, the scattering suppression diagram of the circularly polarized antenna provided by the embodiment. The RCS suppression of X and Y polarizations exceeds 6 dB in the 5.7-16.4 GHz bandwidth, exceeds 4 dB in the 16.4-19 GHz bandwidth, the maximum suppression of X polarization is 22.06 dB at 8.5 GHz, and the maximum suppression of Y polarization is 16.4 dB at 8.2 GHz.

[0055] like Fig. 9 As shown, the radiation patterns of the circularly polarized antenna provided in the embodiment at different frequencies are shown in FIG. 5.9 GHz, 6.85 GHz, 7.4 GHz, and 7.95 GHz are selected for observation within the bandwidth range, and the radiation patterns are good.

[0056] like Fig.10 and Fig.11 As shown, when the incident wave is X-polarized, 7.1 GHz, 8.5 GHz, 10.5 GHz, and 12.2 GHz are selected within the RCS suppression bandwidth for observation; when the incident wave is Y-polarized, 7.3 GHz, 8.5 GHz, 10.5 GHz, and 12.1 GHz are selected within the RCS suppression bandwidth for observation. The scattering suppression of the entire plane is relatively good and uniform.

[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A circularly polarized antenna with RCS suppression characteristics, characterized in that: It comprises a first dielectric substrate and a second dielectric substrate which are stacked; a super surface structure array is arranged on a side of the first dielectric substrate away from the second dielectric substrate; the super surface structure array comprises a plurality of distributed super surface units; A plurality of first metal patches and a second metal patch are arranged in the super surface unit, wherein the plurality of first metal patches are arranged to form a convex-shaped super surface module, and the plurality of second metal patches are arranged to form a concave-shaped super surface module; the convex-shaped super surface module is embedded in the concave-shaped super surface module to form a super surface unit; A metal floor is provided between the first dielectric substrate and the second dielectric substrate; a coupling gap is provided on the metal floor; a sequential rotating feeding network is provided on a side of the second dielectric substrate away from the first dielectric substrate; Energy is input by a sequentially rotating feeding network, and the metasurface structure is excited to form a radiation signal through the coupling slots.

2. The circularly polarized antenna with RCS suppression characteristics according to claim 1, characterized in that: The first metal patch and the second metal patch include a connecting portion, and arrows with opposite directions are respectively arranged at both ends of the connecting portion; the direction of the arrow on the first metal patch and the direction of the arrow on the second metal patch are perpendicular to each other.

3. The circularly polarized antenna with RCS suppression characteristics according to claim 1, characterized in that: The size of the first metal patch is greater than that of the second metal patch.

4. The circularly polarized antenna with RCS suppression characteristics according to claim 1, characterized in that: The metasurface structure array is composed of 2×2 metasurface units; the metasurface unit is a 4×4 matrix formed by a first metal patch and a second metal patch.

5. The circularly polarized antenna with RCS suppression characteristics according to claim 4, characterized in that: In the metasurface structure array, the protruding directions of the convex-shaped metasurface modules in two adjacent metasurface units differ by 90 degrees, and the protruding directions of the convex-shaped metasurface modules in two diagonally distributed metasurface units differ by 180 degrees.

6. The circularly polarized antenna with RCS suppression characteristics according to claim 4, characterized in that: The metal floor is provided with four coupling slots, the coupling slots are arranged in a Z-shape, and the four coupling slots in the Z-shape are centrally symmetrically distributed; the coupling slots are arranged in a one-to-one correspondence with the metasurface units; the center point of the coupling slot overlaps with the vertical projection of the center point of the metasurface unit.

7. The circularly polarized antenna with RCS suppression characteristics according to claim 1 or 6, characterized in that: The coupling slot comprises a first section of coupling sub-slots, a second section of coupling sub-slots and a third section of coupling sub-slots; the first section of coupling sub-slots and the second section of coupling sub-slots, the second section of coupling sub-slots and the third section of coupling sub-slots are perpendicular to each other, and the first section of coupling sub-slots and the third section of coupling sub-slots are parallel to each other; the first section of coupling sub-slots, the second section of coupling sub-slots and the third section of coupling sub-slots are connected in sequence to form a Z shape; the ends of the first section of coupling sub-slots and the third section of coupling sub-slots are both provided with rectangular coupling sub-slots, Y-shaped coupling sub-slots or fan-shaped coupling sub-slots.

8. The circularly polarized antenna with RCS suppression characteristics according to claim 7, characterized in that: The sequential rotation feeding network is provided with a plurality of microstrip lines; the microstrip lines are arranged in one-to-one correspondence with the coupling slots, and the microstrip lines intersect perpendicularly with the projection of the second section of the coupling sub-slot; the microstrip lines are provided with a fan-shaped output end, and the fan-shaped output end is arranged opposite to the center point of the coupling slot.

9. The circularly polarized antenna with RCS suppression characteristics according to claim 1, characterized in that: The dielectric constants of the first dielectric substrate and the second dielectric substrate are in the range of [1, 10]; the thickness h1 of the first dielectric substrate and the thickness h2 of the second dielectric substrate are in the range of [0.001λ0, 0.1λ0]; λ0 is the free space wavelength.

10. The circularly polarized antenna with RCS suppression characteristics according to claim 2, characterized in that: The gap width g between two adjacent first metal patches in the metasurface unit is in the range of ; The side length w of the first metal patch is in the range of [0.2λ g1 ,0.4λ g1 ], the arrow side cut range is [0.2λ g1 ,0.4λ g1 ], the width of the connection The range is [0.2λ g1 ,0.4λ g1 ], where λ g1 is the dielectric effective wavelength of the first dielectric substrate; The side length of the metal floor is W G The range is [λ0,2λ0]; the total length range of the coupling gap is is [0.5λ g2 ,2λ g2 ], the width of the coupling gap ranges from [0.05λ g2 ,0.4λ g2 ], where λ0 is the free space wavelength, λ g2 is the dielectric effective wavelength of the second dielectric substrate.

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