C-band wave-transmitting frequency selective surface unit structure and surface structure

Abstract

The present invention discloses a C-band wave-transmitting frequency-selective surface unit structure and a surface structure, which relate to the field of microwave technology. The unit structure comprises a first dielectric substrate, a second dielectric substrate, and an air layer between the first dielectric substrate and the second dielectric substrate; two cross-shaped hollow metal patches are arranged on the side of the first dielectric substrate close to the second dielectric substrate; two cross-shaped hollow metal patches are arranged on the side of the second dielectric substrate away from the first dielectric substrate, and a resistor patch welded on the two cross-shaped hollow metal patches. The present invention discloses a C-band wave-transmitting frequency-selective surface unit structure and a surface structure formed according to the unit structure, which have a better in-band transmission coefficient and a wider bandwidth of the wave-transmitting frequency band, thereby realizing in-band broadband wave transmission in the C-band and out-band broadband reflection.

Description

Technical Field

[0001] The present invention relates to the field of microwave technology, and more particularly to a C-band wave-transmitting frequency selective surface unit structure and a surface structure. Background Art

[0002] The C-band refers to electromagnetic waves in the frequency band from 4GHz to 8GHz, which are widely used in fields such as radar and satellite TV broadcasting. The frequency selective surface is a two-dimensional periodic structure with a planar metal array on a medium. It exhibits transmission and reflection characteristics at a certain resonant frequency. The frequency selective surface structure will produce good reflection characteristics within a specific frequency range of its stop band. The reflective frequency selective structure uses reflection in a specific frequency band to achieve stealth. However, the existing frequency selective surface structure has technical defects such as poor transmittance to electromagnetic waves in the C-band and narrow bandwidth. Therefore, how to overcome the above problems is a technical problem that technicians in this field need to solve. Summary of the invention

[0003] In view of this, the present invention provides a C-band wave-transmitting frequency selective surface unit structure and surface structure.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A C-band wave-transmitting frequency selective surface unit structure comprises a first dielectric base layer, a second dielectric base layer, and an air layer between the first dielectric base layer and the second dielectric base layer;

[0006] A metal patch is provided on one side of the first dielectric base layer close to the second dielectric base layer;

[0007] The side of the second dielectric base layer away from the first dielectric base layer is only provided with a metal patch.

[0008] The metal patch arranged on the first dielectric base layer comprises a first cross-shaped hollow metal patch arranged on the periphery of the first dielectric base layer and a second cross-shaped hollow metal patch arranged on the inner periphery of the first dielectric base layer.

[0009] The metal patch arranged on the second dielectric base layer comprises a third cross-shaped hollow metal patch arranged on the periphery of the second dielectric base layer and a fourth cross-shaped hollow metal patch arranged on the inner periphery of the second dielectric base layer.

[0010] Optionally, the first dielectric base layer and the second dielectric base layer are both F4B dielectric plates with a dielectric constant of 2.65, a loss angle of 0.0013, and a thickness of 0.5 mm.

[0011] Optionally, the size of the surface unit structure is 1 / 2 of the wavelength corresponding to the operating center frequency.

[0012] Optionally, the size of the surface unit structure is 30 mm.

[0013] Optionally, the dimensions of the third cross-shaped hollow metal patch on the periphery of the second dielectric base layer are: side length l1=29mm, l2=3mm, width dl1=0.5mm; the dimensions of the fourth cross-shaped hollow metal patch on the inner periphery of the second dielectric base layer are: side length l3=8mm, l4=2mm, width dl3=0.5mm.

[0014] Optionally, the size of the first cross-shaped hollow metal patch outside the first dielectric base layer is consistent with the size of the third cross-shaped hollow metal patch; the size of the cross-shaped metal patch inside the first dielectric base layer is consistent with the size of the fourth cross-shaped hollow metal patch.

[0015] A C-band wave-transmitting frequency selective surface structure is formed by arranging the frequency selective surface unit structures in a periodic rectangular array.

[0016] It can be seen from the above technical solutions that the present invention discloses a C-band wave-transmitting frequency selective surface unit structure and surface structure, which has the following beneficial effects compared with the prior art:

[0017] The present invention discloses a C-band wave-transmitting frequency-selective surface unit structure and a surface structure formed based on the unit structure. Two cross-shaped hollow metal patches are arranged on a first dielectric base layer, and two cross-shaped hollow metal patches are arranged on a second dielectric base layer. The in-band transmission coefficient is better and the bandwidth of the wave-transmitting band is wider, thereby realizing in-band broadband wave transmission and out-of-band reflection.

[0018] The present invention obtains the optimal unit structure parameters by adjusting the unit structure size and the dielectric layer thickness through an equivalent circuit method, and can change the working frequency band of the frequency selective surface structure by adjusting the unit structure size and the patch size. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0020] Figure 1 This is a schematic diagram of the structure of a frequency selective surface unit of the present invention;

[0021] Figure 2 It is an overall schematic diagram of the frequency selective surface structure of the present invention;

[0022] FIG3( a ) is a schematic diagram of the first dielectric substrate structure of the frequency selective surface unit structure of the present invention;

[0023] FIG3( b ) is a schematic diagram of the second dielectric substrate structure of the frequency selective surface unit structure of the present invention;

[0024] Figure 4 is an equivalent circuit diagram of the frequency selective surface unit structure of the present invention;

[0025] FIG5( a ) is a transmission coefficient simulation diagram of a frequency selective surface unit structure of the present invention;

[0026] FIG5( b ) is a simulation diagram of the reflection coefficient of the frequency selective surface unit structure of the present invention;

[0027] Among them, 1 is the first dielectric base layer, 2 is the second dielectric base layer, 3 is the air layer, 4 is the first cross-shaped hollow metal patch, 5 is the second cross-shaped hollow metal patch, 6 is the third cross-shaped hollow metal patch, and 7 is the fourth cross-shaped hollow metal patch; 11 is the first dielectric base layer of the frequency selective surface structure, 12 is the air layer of the frequency selective surface structure, and 13 is the second dielectric base layer of the frequency selective surface structure. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The embodiment of the present invention discloses a C-band wave-transmitting frequency selective surface unit structure, see Figure 1 , comprising a first dielectric base layer 1, a second dielectric base layer 2, and an air layer 3 between the first dielectric base layer 1 and the second dielectric base layer 2;

[0030] A metal patch is provided on one side of the first dielectric substrate 1 close to the second dielectric substrate 2;

[0031] A metal patch is disposed on a side of the second dielectric substrate 2 away from the first dielectric substrate 1 .

[0032] 3( a ), the metal patches arranged on the first dielectric base layer 1 include a first cross-shaped hollow metal patch 4 arranged on the periphery of the first dielectric base layer 1 and a second cross-shaped hollow metal patch 5 arranged on the inner periphery of the first dielectric base layer 1 .

[0033] 3( b ), the metal patches provided on the second dielectric base layer 2 include a third cross-shaped hollow metal patch 6 provided on the periphery of the second dielectric base layer 2 and a fourth cross-shaped hollow metal patch 7 provided on the inner periphery of the second dielectric base layer 2 .

[0034] The embodiment of the present invention also provides a frequency selective surface structure that is wave-transmissive in the C band, see Figure 2 The frequency selective surface structure is composed of a frequency selective surface unit structure arranged in a periodic rectangular array.

[0035] The equivalent circuit model of the frequency selective surface unit structure of the present invention is as follows: Figure 4 As shown, Z0 represents the wave impedance of free space, Z F1 is the resistive layer, Z F2 is a lossless matching layer, and Z1 represents the wave impedance of the spacer layer. Figure 4 Transfer Matrix To find the relationship between the input and output of the cascade network, then, using the relationship between the transfer matrix and the scattering matrix, the scattering matrix, i.e., the S parameter, can be solved:

[0036]

[0037] in, Characterizes the relationship between the total input voltage and total input current of port 1 and the total output voltage and total output current of port 2, f is the operating frequency, c is the speed of light in a vacuum, ε r1 is the relative dielectric constant of the dielectric substrate, and h1 is the thickness of the air layer.

[0038] In order to achieve in-band transmission and out-band reflection, this embodiment defines f1, f2 and f3 in sequence from low frequency to high frequency, and designs ideal indicators S at f1 and f3. 11 =1, S 21 =0, design the ideal index S at f2 11 =0, S 21 =1. 11 and S 21 They refer to the reflection coefficient of port 1 and the forward transmission coefficient from port 1 to port 2 respectively.

[0039] Transforming the transfer matrix can get S 11 and S 21 .

[0040]

[0041]

[0042] Where M = Z F1 Z F2 ,N=ZF1 +Z F2 ,T=Z F1 -Z F2 , and

[0043] The middle dielectric layer is air, then Z1=Z0, Q=0, according to the ideal target f1 and f3 frequency S 21 =0, then Z F1 Z F2 =0, if Z F1 = 0, equivalent to a metal surface, total reflection will occur, so Z F2 = 0. Since Z F1 As complex impedance, Z F1 =R+jX Substitute into S 11 Expression, by S 11 =1, we get:

[0044]

[0045] At f2, according to S 21 =1, for S 21 Calculate and get:

[0046]

[0047] When Z F1 Z F2 →∞, the denominator modulus |cosθ1+jsinθ1|=1, so S 21 = 1. Therefore, as long as the upper and lower layers are bandpass structures, in-band transmission and out-band reflection can be achieved.

[0048] The frequency selective surface structure with in-band transmission and out-band reflection must meet the following conditions:

[0049] 1. Z1=Z0, that is, the frequency selective surfaces of the two cross-shaped hollow metal patches of the second dielectric substrate 2 and the two cross-shaped hollow metal patches of the first dielectric substrate 1 are separated by an air layer 3;

[0050] 2. Z F2 =0, that is, the frequency selective surfaces of the first cross-shaped hollow metal patch 4 and the second cross-shaped hollow metal patch 5 of the first dielectric base layer 1 need to resonate at f1 and f3;

[0051] By optimizing the design of the frequency selective surface structure, the final size is obtained: the size of the frequency selective surface unit structure is 30 mm, which is about 1 / 2 of the wavelength corresponding to the center frequency; the size of the third cross-shaped hollow metal patch 6 on the periphery of the second dielectric base layer 2 is: side length l1=29 mm, l2=3 mm, width dl1=0.5 mm; the size of the fourth cross-shaped hollow metal patch 7 on the inner periphery of the second dielectric base layer 2 is: side length l3=8 mm, l4=2 mm, width dl3=0.5 mm; the size of the first cross-shaped hollow metal patch 4 on the periphery of the first dielectric base layer 1 is consistent with the size of the third cross-shaped hollow metal patch 6; the size of the second cross-shaped hollow metal patch 5 on the inner periphery of the first dielectric base layer 1 is consistent with the size of the fourth cross-shaped hollow metal patch 7.

[0052] In a specific embodiment, the first dielectric base layer 1 and the second dielectric base layer 2 are both F4B dielectric plates with a dielectric constant of 2.65, a loss angle of 0.0013, and a thickness of 0.5 mm.

[0053] like Figure 5(a)-Figure 5(b) As shown, within the frequency band (0 GHz-12 GHz) of the designed unit, the bandwidth of the transmittance band greater than 3 dB is 3.523 GHz-9.789 GHz.

[0054] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0055] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A C-band wave-transmitting frequency selective surface unit structure, characterized in that: It comprises a first dielectric base layer (1), a second dielectric base layer (2), and an air layer (3) between the first dielectric base layer (1) and the second dielectric base layer (2); A metal patch is provided on one side of the first dielectric base layer (1) close to the second dielectric base layer (2); The second dielectric base layer (2) is provided with only a metal patch on a side away from the first dielectric base layer (1); The metal patch arranged on the first dielectric base layer (1) comprises a first cross-shaped hollow metal patch (4) arranged on the periphery of the first dielectric base layer (1) and a second cross-shaped hollow metal patch (5) arranged on the inner periphery of the first dielectric base layer (1); The metal patch arranged on the second dielectric base layer (2) comprises a third cross-shaped hollow metal patch (6) arranged on the periphery of the second dielectric base layer (2) and a fourth cross-shaped hollow metal patch (7) arranged on the inner periphery of the second dielectric base layer (2); Determine the equivalent circuit model and transfer matrix of the frequency selective surface unit structure, and solve the expression form of the scattering matrix of the equivalent circuit model; determine the ideal index expression of the equivalent circuit model that requires a full reflection band, and the expression is as follows: The ideal index expression of the equivalent circuit model for the transmission band is determined as follows: Among them, S 11 represents the reflection coefficient of port 1 of the equivalent circuit model, S 21 represents the forward transmission coefficient from port 1 to port 2 of the equivalent circuit model, Z0 represents the wave impedance of free space, Z1 represents the wave impedance of the spacer layer, and Z F1 is the impedance layer, Z F2 Indicates the lossless matching layer M, N, T, P, Q, θ1 is the intermediate quantity, M = Z F1 Z F2 、N=Z F1 +Z F2 、T=Z F1 -Z F2 , Where f represents the operating frequency, c represents the speed of light in vacuum, ε r1 represents the relative dielectric constant of the dielectric substrate, and h1 represents the thickness of the air layer; According to the ideal index expression, the conditions that the frequency selective surface structure that transmits waves in the band and reflects outside the band meets are analyzed, and the conditions include: Z1=Z0, indicating that the frequency selective surfaces of the two cross-shaped hollow metal patches of the second dielectric substrate (2) and the two cross-shaped hollow metal patches of the first dielectric substrate (1) are separated by an air layer 3; Z F2 =0, indicating that the frequency selective surfaces of the first cross-shaped hollow metal patch (4) and the second cross-shaped hollow metal patch (5) of the first dielectric base layer (1) need to generate resonance at f1 and f3; The dimensions of the third cross-shaped hollow metal patch (6) are: side length l1 = 29 mm, l2 = 3 mm, width dl1 = 0.5 mm; the dimensions of the fourth cross-shaped hollow metal patch (7) are: side length l3 = 8 mm, l4 = 2 mm, width dl3 = 0.5 mm; The size of the first cross-shaped hollow metal patch (4) is consistent with the size of the third cross-shaped hollow metal patch (6); the size of the second cross-shaped hollow metal patch (5) inside the first dielectric base layer (1) is consistent with the size of the fourth cross-shaped hollow metal patch (7); The first dielectric base layer (1) and the second dielectric base layer (2) are both F4B dielectric plates with a dielectric constant of 2.65, a loss angle of 0.0013, and a thickness of 0.5 mm; The size of the surface unit structure is 1 / 2 of the wavelength corresponding to the working center frequency.

2. A C-band wave-transmitting frequency selective surface unit structure according to claim 1, characterized in that: The size of the surface unit structure is 30 mm.

3. A C-band wave-transmitting frequency selective surface structure, characterized in that: The frequency selective surface unit structure described in any one of claims 1 to 2 is arranged in a periodic rectangular array.

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