X-band wave transmission frequency selection surface unit structure and surface structure

Abstract

This invention discloses a frequency-selective surface unit structure and surface structure for X-band wave transmission, relating to the field of microwave technology. The unit structure includes a first dielectric substrate, a second dielectric substrate, and an air layer between the first and second dielectric substrates. A square annular metal patch and a cross-shaped metal patch are disposed on the side of the first dielectric substrate closest to the second dielectric substrate. Two square annular metal patches are disposed on the side of the second dielectric substrate furthest from the first dielectric substrate. The frequency-selective surface unit structure for X-band wave transmission and the surface structure based on this invention can improve the reflection effect in the reflection frequency band, resulting in better in-band transmission coefficient and a wider transmission bandwidth, thereby achieving broadband in-band wave transmission and out-of-band reflection in the X-band.

Description

Technical Field

[0001] This invention relates to the field of microwave technology, and more specifically to a frequency-selective surface unit structure and surface structure for X-band wave transmission. Background Technology

[0002] X-band refers to electromagnetic waves in the frequency range of 8 GHz to 12 GHz, which are widely used in radar detection and satellite communication.

[0003] Frequency selective surfaces (FSS) possess unique polarization selectivity characteristics, such as converting linearly polarized incident waves into circularly polarized waves, and horizontally polarized incident waves into vertically polarized waves. Based on these unique properties, FSSs have been widely applied in radar radomes, reflectors, polarizers, microwave sensors, and space filters. A FSS is a two-dimensional periodic structure with planar metal array elements (patches or aperture units smaller than the operating wavelength) on a dielectric substrate, exhibiting transmission and reflection characteristics at certain resonant frequencies. FSS structures produce good reflection characteristics within a specific frequency range of their stopband. However, existing FSS structures suffer from poor transmission and narrow bandwidth for X-band electromagnetic waves. Therefore, overcoming these problems is a technical challenge that needs to be addressed by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a frequency-selective surface unit structure and surface structure for X-band wave transmission.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A frequency-selective surface unit structure for X-band wave transmission includes a first dielectric substrate, a second dielectric substrate, and an air layer between the first dielectric substrate and the second dielectric substrate.

[0007] A metal patch is provided on the side of the first dielectric substrate close to the second dielectric substrate;

[0008] The second medium substrate has only a metal patch on the side away from the first medium substrate.

[0009] The metal patch provided in the first medium substrate includes a first square ring-shaped metal patch disposed on the periphery of the first medium substrate and a cross-shaped metal patch disposed on the inner periphery of the first medium substrate.

[0010] The metal patch provided in the second medium substrate includes a second square ring-shaped metal patch disposed on the periphery of the second medium substrate and a third square ring-shaped metal patch disposed on the inner periphery of the second medium substrate.

[0011] Optionally, both the first dielectric substrate and the second dielectric substrate are F4B dielectric boards with a dielectric constant of 2.65, a loss angle of 0.0013, and a thickness of 0.5 mm.

[0012] Optionally, the size of the surface unit structure is half the wavelength corresponding to the operating center frequency.

[0013] Optionally, the surface unit structure has a size of 15 mm.

[0014] Optionally, the dimensions of the second square annular metal patch surrounding the second medium substrate are: width updl = 0.5 mm, side length upl = 14.3 mm; the dimensions of the third square annular metal patch surrounding the second medium substrate are: width updl2 = 0.5 mm, side length upl2 = 5 mm.

[0015] Optionally, the dimensions of the first square annular metal patch on the periphery of the first medium substrate are: width dl = 0.5 mm, side length l = 14.6 mm; the dimensions of the cross-shaped metal patch on the inner periphery of the first medium substrate are: length l2 = 7 mm, width w2 = 0.8 mm.

[0016] A frequency-selective surface structure for X-band transmission is constructed by arranging the frequency-selective surface unit structure in a periodic rectangular array.

[0017] As can be seen from the above technical solution, the present invention discloses a frequency-selective surface unit structure and surface structure for X-band wave transmission, which has the following advantages compared with the prior art:

[0018] This invention discloses a frequency-selective surface unit structure for X-band transmission and a surface structure based on the unit structure. A square annular metal patch and a cross-shaped metal patch are disposed on a first dielectric substrate, and two square annular metal patches are disposed on a second dielectric substrate. This results in better in-band transmission coefficient and a wider transmission bandwidth, thereby achieving broadband in-band transmission and out-of-band reflection. Furthermore, this invention uses an equivalent circuit method to design the unit structure size, dielectric layer thickness, etc., to obtain optimal unit structure parameters. The operating frequency band of the frequency-selective surface structure can be changed by adjusting the unit structure size and the metal patch size. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

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

[0021] Figure 2 This is a schematic diagram of the overall frequency-selective surface structure of the present invention;

[0022] Figure 3(a) is a schematic diagram of the first dielectric substrate structure of the frequency selective surface unit structure of the present invention;

[0023] Figure 3(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 This is an equivalent circuit diagram of the frequency selective surface unit structure of the present invention;

[0025] Figure 5(a) is a simulation diagram of the transmission coefficient of the frequency selective surface unit structure of the present invention;

[0026] Figure 5(b) is a simulation diagram of the reflection coefficient of the frequency selective surface unit structure of the present invention;

[0027] Wherein, 1 is the first dielectric substrate, 2 is the second dielectric substrate, 3 is the air layer, 4 is the first square annular metal patch, 5 is the cross-shaped metal patch, 6 is the second square annular metal patch, 7 is the third square annular metal patch; 11 is the first dielectric substrate of the frequency selective surface structure, 12 is the air layer of the frequency selective surface structure, and 13 is the second dielectric substrate of the frequency selective surface structure. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention discloses a frequency-selective surface unit structure for X-band wave transmission, see [link to relevant documentation]. Figure 1 It includes a first medium base layer 1, a second medium base layer 2, and an air layer 3 between the first medium base layer 1 and the second medium base layer 2;

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

[0031] A metal patch is provided on the side of the second medium substrate 2 away from the first medium substrate 1.

[0032] In a specific embodiment, referring to FIG3(a), the metal patch disposed on the first medium base layer 1 includes a first square ring-shaped metal patch 4 disposed on the periphery of the first medium base layer 1 and a cross-shaped metal patch 5 disposed on the inner periphery of the first medium base layer 1.

[0033] In a specific embodiment, referring to FIG3(b), the metal patch disposed on the second dielectric substrate 2 includes a second square ring-shaped metal patch 6 disposed on the periphery of the second dielectric substrate 2 and a third square ring-shaped metal patch 7 disposed on the inner periphery of the second dielectric substrate 2.

[0034] This invention also provides a frequency-selective surface structure for X-band wave transmission, see [link to relevant documentation]. Figure 2 The frequency selective surface structure is composed of frequency selective surface unit structures arranged in a periodic rectangular array.

[0035] The equivalent circuit model of the frequency selective surface unit cell structure of this invention is as follows: Figure 4 As shown, Z0 represents the wave impedance in free space, Z F2 Z is the equivalent impedance of the first dielectric substrate 1. F1 Z1 represents the equivalent impedance of the second dielectric substrate 2, and Z1 represents the wave impedance of the spacer layer. Figure 4 Transition matrix To determine the relationship between the input and output of the cascaded network, we can then use the relationship between the transition matrix and the scattering matrix to solve for the scattering matrix, i.e., the S-parameters.

[0036]

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

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

[0039] Transforming the transition matrix yields S 11 and S 21 .

[0040]

[0041]

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

[0043] If the intermediate dielectric layer is air, then Z1 = Z0, Q = 0. Based on the ideal target frequencies f1 and f3, S... 21 =0, then Z F1 Z F2 =0, if Z F1 =0, equivalent to a metallic surface, total internal reflection will occur, therefore Z F2 =0. Because Z F1 For complex impedance, Z F1 =R+jX Substitute into S 11 The expression, by S 11 =1 gives:

[0044]

[0045] According to S at f2 21 =1, for S 21 The calculation yields:

[0046]

[0047] When Z F1 Z F2 As we approach infinity, the modulus of the denominator |cosθ1+jsinθ1|=1, therefore S 21 =1. Therefore, as long as the upper and lower layers are bandpass structures, it is possible to achieve in-band wave transmission and out-of-band reflection.

[0048] The frequency selection surface structure for in-band wave transmission and out-of-band reflection must meet the following conditions:

[0049] 1. Z1 = Z0, that is, the two square ring-shaped metal patches of the second dielectric base layer 2 and the square ring-shaped metal patch and cross-shaped metal patch 5 of the first dielectric base layer 1 are separated by an air layer 3.

[0050] 2. Z F2 =0, meaning that the first square ring-shaped metal patch 4 and cross-shaped metal patch 5 of the first dielectric substrate 1 need to resonate at f1 and f3.

[0051] Through optimized design of the frequency selective surface structure, the final dimensions are obtained: the size of the frequency selective surface unit structure is 15mm, which is about half of the wavelength corresponding to the center frequency; the dimensions of the second square annular metal patch 6 on the periphery of the second dielectric substrate 2 are: width updl = 0.5mm, side length upl = 14.3mm; the dimensions of the third square annular metal patch 7 on the inner periphery of the second dielectric substrate 2 are: width updl2 = 0.5mm, side length upl2 = 5mm; the dimensions of the first square annular metal patch 4 on the periphery of the first dielectric substrate 1 are: width dl = 0.5mm, side length l = 14.6mm; the dimensions of the cross-shaped metal patch 5 on the inner periphery of the first dielectric substrate 1 are: length l2 = 7mm, width w2 = 0.8mm.

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

[0053] like Figures 5(a)-5(b) As shown, within the frequency band (2GHz-20GHz) of the designed unit, the bandwidth of the pass-through radio frequency band greater than 3dB is 7.3GHz-14.2GHz.

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

[0055] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A frequency-selective surface unit structure for X-band wave transmission, characterized in that, It includes a first medium base layer (1), a second medium base layer (2), and an air layer (3) between the first medium base layer (1) and the second medium base layer (2); A metal patch is provided on the side of the first medium substrate (1) near the second medium substrate (2); The second medium substrate (2) has only a metal patch on the side away from the first medium substrate (1); The metal patch provided on the first medium substrate (1) includes a first square ring-shaped metal patch (4) provided on the periphery of the first medium substrate (1) and a cross-shaped metal patch (5) provided on the inner periphery of the first medium substrate (1); The metal patch provided on the second medium substrate (2) includes a second square ring-shaped metal patch (6) provided on the periphery of the second medium substrate (2) and a third square ring-shaped metal patch (7) provided on the inner periphery of the second medium substrate (2); Both the first dielectric substrate (1) and the second dielectric substrate (2) are F4B dielectric boards 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 half the wavelength corresponding to the operating center frequency; the size of the surface unit structure is 15 mm.

2. The frequency-selective surface unit structure for X-band wave transmission according to claim 1, characterized in that, The dimensions of the second square ring-shaped metal patch (6) are: width updl = 0.5mm, side length upl = 14.3mm; the dimensions of the third square ring-shaped metal patch (7) are: width updl2 = 0.5mm, side length upl2 = 5mm.

3. The frequency-selective surface unit structure for X-band wave transmission according to claim 1, characterized in that, The dimensions of the first square ring-shaped metal patch (4) are: width dl = 0.5 mm, side length l = 14.6 mm; the dimensions of the cross-shaped metal patch (5) surrounding the first medium base layer (1) are: length l2 = 7 mm, width w2 = 0.8 mm.

4. A frequency-selective surface structure for X-band wave transmission, characterized in that, It is constructed using the frequency-selective surface unit structure as described in any one of claims 1-3, arranged in a periodic rectangular array.

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