CN116937174A - Passive RIS antireflection film based on frequency selective surface and application thereof in 5G communication - Google Patents
Passive RIS antireflection film based on frequency selective surface and application thereof in 5G communication Download PDFInfo
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- H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
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Abstract
The application discloses a passive RIS antireflection film based on a frequency selective surface and application thereof in 5G communication, wherein the passive RIS antireflection film comprises an outdoor conducting layer substrate, an outdoor conducting layer, outdoor glass, an air layer, indoor glass, an indoor conducting layer and an indoor conducting layer substrate which are sequentially arranged in the outdoor-to-indoor direction; wherein, the outdoor conducting layer substrate close to the outdoor glass is in a windmill structure; the indoor conductive layer close to the indoor glass is of a round-end cross structure; the double-layer antireflection film designed based on the impedance matching principle can realize good impedance matching with free space, and can improve the light transmittance to the greatest extent while guaranteeing the light transmittance.
Description
Technical Field
The application belongs to the technical field of antireflection films, and particularly relates to a passive RIS antireflection film based on a frequency selective surface and application of the passive RIS antireflection film in 5G communication.
Background
The frequency selective surface (Frequency Selective Surface, FSS) is a periodic array structure with metallic resonant cells arranged in a one-dimensional or two-dimensional array, which can better control the transmission and scattering of electromagnetic waves, and can cause total reflection or total transmission of incident electromagnetic waves at the resonant frequency. It is currently common to design to utilize passive RIS surfaces to achieve adjustment of the reflected beam to enhance signal coverage. The conventional FSS antireflection film adopts a classical jersey cooling cross structure and a standing or plane split ring structure, does not consider light transmittance, and cannot be applied to glass materials of various buildings. And none of the above antireflection films were tested for practical use.
The influence of glass on signal transmission in the 5G communication process is not considered in the prior art. For example, the application with publication number of CN108254810a, named as a terahertz antireflection film based on a planar open ring structure, designs an antireflection film working in a terahertz wave band, however, the antireflection film is not matched with the frequency band of 5G communication, so that the antireflection film cannot be applied to daily 5G communication.
Disclosure of Invention
In order to overcome the defects in the prior art, the application aims to provide the passive RIS antireflection film based on the frequency selective surface and the application of the passive RIS antireflection film in 5G communication, and the double-layer antireflection film designed based on the impedance matching principle can realize good impedance matching with free space, so that the transmittance is improved to the greatest extent while the transmittance is ensured.
In order to achieve the above purpose, the technical scheme adopted by the application is as follows:
a passive RIS antireflection film based on a frequency selective surface comprises an outdoor conducting layer substrate, an outdoor conducting layer, outdoor glass, an air layer, indoor glass, an indoor conducting layer and an indoor conducting layer substrate which are sequentially arranged along the incoming wave direction; wherein, the outdoor conducting layer substrate close to the outdoor glass is in a windmill structure;
the windmill structure comprises a square base material, wherein two crossed gap structures are arranged on the surface of the base material along the diagonal position of the square base material;
the indoor conductive layer close to the indoor glass is of a round-end cross structure;
the round end cross structure comprises a square base material, the center of the square base material is provided with a cross copper patch, and the end part of the cross copper patch is provided with a round copper patch.
The specific structure of the windmill structure is as follows: comprises a square base material with a side length of p, wherein the midpoints of four sides of the square base material are provided with isosceles triangle copper patches I, wherein the isosceles triangle copper patches I are formed by (p-l) 3 ) 2 is high, l 3 Representing the vertex spacing of an isosceles triangle enclosing the windmill structure;
four corners of the square base material are isosceles triangle copper patches II, and the right-angle side length of the isosceles triangle copper patches II is d;
the specific structure of the round end cross structure is as follows: comprises a square base material with a side length p, wherein the cross copper patch is perpendicular to the square base material, and the arm length l 1 And the width is w, and the circular copper patch takes r as the radius.
Further, an isosceles triangle is formed in the up-down, left-right four directions of the windmill structure of the square unit with the side length p, and the bottom side length of the isosceles triangle is l 2 。
The windmill structure is adhered to the outdoor glass through the optical OCA colloid, and the round end cross structure is adhered to the indoor glass through the optical OCA colloid.
In the windmill structure, when considering the light transmittance of the glass, the edge of the windmill structure is hollowed, and after the windmill structure is hollowed, the hollowed size is divided into m 1 And m 2 ，m 1 For the height, m of the middle-waist triangle copper patch of the windmill gap 2 The bottom of the middle triangle copper patch is the windmill gap.
The outdoor conducting layer substrate and the indoor conducting layer substrate adopt PET substrates with dielectric constants of 3.4 and loss tangents of 0.005 as medium supports; the glass medium of the outdoor glass and the indoor glass adopts actual scene parameters, and is a double-layer glass medium with a dielectric constant of 6.7 and a loss tangent of 0.012.
In the two-layer patch type FSS structure consisting of the windmill structure and the round end cross structure, different layers of the FSS unit are equivalent to mutually cascaded circuits, and the equivalent circuit method refers to equivalent frequency selection surfaces to be inductance or electricityCapacitive element, method for calculating and solving frequency response of frequency selective surface by transmission line theory, and equivalent circuit analysis method, wherein the windmill structure is equivalent to L 1 C 1 And L is equal to 2 C 2 Parallel connection and round end cross structure equivalent to series circuit L 3 C 3 The middle part comprises outdoor glass, an air layer and indoor glass which are equivalent to transmission lines, L 1 C 1 And L is equal to 2 C 2 In parallel, with characteristic impedance Z 1 Will L 3 C 3 And the parallel circuit is connected with the circuit by a characteristic impedance Z 0 Wherein Z is connected to an external circuit 0 For free space characteristic impedance, Z 1 Equivalent impedance for glass medium;
the round end cross structure of the double-layer antireflection film generates low-frequency resonance, which is equivalent to an LC series circuit; wherein L is 1 、C 1 ，L 2 、C 2 Parallel LC cascade circuits, L, respectively representing the structural equivalence of windmills 3 、C 3 Respectively refers to a capacitance and an inductance equivalent to the round end cross structure; series L 3 C 3 Resonant at frequency f 1 The windmill structure is coupled with the round end cross structure to generate high-frequency resonance.
L 1 C 1 、L 2 C 2 Parallel and then connected with L 3 C 3 At high frequency constitute a new parallel resonance at frequency f 2 A place; the corresponding resonant frequencies are respectively:
furthermore, by adjusting parameters in the windmill structure and the round end cross structure, the method is equivalent to adjusting the equivalent impedance of the antireflection film based on the frequency selective surface, so that the antireflection film can achieve impedance matching between free space (namely in air) and two layers of media of indoor glass and outdoor glass, and the antireflection of indoor stadium signals is realized.
The passive RIS antireflection film replicates any number in the x direction and the y direction in the proportion of n multiplied by n, and the center-to-center spacing between adjacent units in the x direction and the y direction is p, so that the passive RIS antireflection film can be a super-surface array.
A method for adjusting passive RIS antireflection film based on frequency selective surface adjusts parameters in windmill structure and round end cross structure to achieve impedance matching, comprising the following steps;
step one: numerical simulation is carried out on the FSS antireflection film by using commercial electromagnetic simulation software CST Microwave;
step two: r is the radius of the lower round end cross of the round end cross structure, and the equivalent capacitance C of the lower round end cross unit is increased along with the increase of the radius r 3 Increase of series resonance frequency f 2 Move to lower frequency, S 21 The peak value is more obvious, the transition zone becomes steeper along with the radius increase, and the wave transmission rate is reduced;
step three: l (L) 1 Is a lower layer single L with a round end cross structure 3 C 3 Length of the meta-cross branch along with length l 1 Is increased, equivalent inductance L of lower round end cross unit 3 Increase of series resonance frequency f 2 Move to lower frequency and S at resonance frequency 21 The wave transmission rate is gradually reduced;
step four: spacing l of upper windmill structure 3 The lower limit of the wave-transparent frequency band is determined, and the distance l is followed 3 Is increased by the upper layer unit equivalent capacitance C 1 The value is reduced, thereby the series resonance frequency f 1 Shifting to higher frequencies, the bandwidth of the transmission band increases but the transmission rate gradually decreases;
by adjusting the above parameters, the equivalent capacitance C in the cell is changed 1 And equivalent inductance L 3 Thereby changing the equivalent impedance of the antireflection film and achieving impedance matching.
The anti-reflection film is applied to 5G communication, the anti-reflection film is adhered to two sides of a medium of outdoor glass 3 and indoor glass 5, signals are sent out by a base station and transmitted to an indoor venue through a passive RIS, and the direction of a reflected main beam is changed by adjusting the reflection phase of a radiation unit on the surface of the passive RIS;
on the interface between the free space and the medium, when the medium impedance is equal to the free space wave impedance, the interface reflection coefficient is 0, and the transmission reaches the maximum, namely the impedance matching is realized. The process that the medium passes through the passive RIS and enters the room is used for improving path loss and diffraction loss caused by a part of complex buildings, and the anti-reflection film adhered on the glass medium is used for realizing impedance matching with free space, so that the wave transmission loss is reduced, the signal transmittance is increased, and the coverage of indoor signals is enhanced.
The application has the beneficial effects that:
the application designs a double-layer antireflection film according to the impedance matching principle. Compared with the original glass medium, the glass medium loaded with the designed double-layer antireflection film has the effect of improving the transmission coefficient to different degrees when the glass medium is incident at a large angle under two polarizations;
in order to ensure the practical application value of the designed antireflection film, the transmittance is improved to the greatest extent while the transmittance is ensured, the transmittance of the designed antireflection film is improved, hollowing-out treatment is carried out, and the actual measurement is carried out to verify the wave-transmitting effect.
Proved by verification, the designed double-layer antireflection film realizes good impedance matching with free space, and the wave transmittance and the light transmittance are obviously improved in a required frequency band.
Drawings
Fig. 1 is a schematic diagram of an actual application scenario of an antireflection film.
Fig. 2 is a three-dimensional structure diagram of a double-layer antireflection film.
Fig. 3 is a double-layer antireflection film equivalent circuit.
Fig. 4 is a schematic diagram of a transmission coefficient curve corresponding to the parameter variation.
Fig. 5 is a schematic diagram of the surface current distribution corresponding to each layer unit of three frequency points.
Fig. 6 is a three-dimensional structure diagram after the "hollowed-out" process.
FIG. 7 is a plot of TE polarization S-parameters for a "hollowed" design.
FIG. 8 is a graph of the "hollowed out" design TM polarization S-parameter.
FIG. 9 is a schematic diagram of the relative surface impedance of an "hollowed out" design antireflection film.
Fig. 10 is a schematic view of an antireflection film processing sample.
FIG. 11 is a schematic diagram of a detail of the processing of an anti-reflection film unit.
FIG. 12 is a schematic diagram of an anti-reflection film sample transmission coefficient test system.
Fig. 13 is a comparison of normal incidence glass media and anti-reflection film S parameter test results.
Fig. 14 is a comparison of 30 ° incident glass media with the S parameter test results for an antireflection film.
Fig. 15 is a comparison of TE polarized 60 ° incident glass media with the S parameter test results of an antireflection film.
Detailed Description
The application is described in further detail below with reference to the accompanying drawings.
The application scene is shown in figure 1, the passive RIS antireflection film based on the frequency selective surface is stuck on two sides of a double-layer glass medium, and signals are sent out by a base station and transmitted to an indoor venue through the passive RIS. The passive RIS changes the direction of the reflected main beam by adjusting the reflection phase of the radiation unit, the process can improve the path loss and diffraction loss caused by a part of complex buildings, and the anti-reflection film adhered on the glass medium realizes the impedance matching with the free space, thereby reducing the wave transmission loss, increasing the signal transmittance and enhancing the coverage of indoor signals.
In order to realize good impedance matching in the frequency range of 4.8GHz-4.9GHz, antireflection film structures are respectively designed on two sides of a double-layer glass medium.
The initial design of the double-layer antireflection film unit structure is shown in FIG. 2, and comprises the steps of sequentially arranging the thickness h from outdoor to indoor 3 Is a conductive layer substrate of a thickness h j Is a conductive layer of (a) and a thickness h 0 Outdoor glass 3, thickness h 1 Air layer 4, thickness h of 2 Indoor glass 5, thickness h j Is a conductive layer of thickness h 3 Is a conductive layer substrate; in the figure, l 1 Arm length l representing round end cross structure 2 Representing the length of the base of an isosceles triangle enclosing a windmill structure，l 3 The vertex pitch of an isosceles triangle surrounding the windmill structure is represented, w represents the line width, and r represents the radius of the end circle of the round-end cross structure. Wherein the conducting layer close to the outdoor glass 3 is in a windmill structure; the conducting layer close to the indoor glass 5 is of a round-end cross structure;
the windmill structure and the round end cross structure are both stuck on two sides of the glass by optical OCA colloid.
The specific structure of the windmill structure is as follows: at the midpoints of four sides of a square cell with side length p, the square cell is divided into four parts (p-l) 3 ) And 2, making isosceles triangle copper patches with the height and then making isosceles triangle copper patches with the right angle side length d at four corners of the unit. The thickness of the copper patch was 0.018mm.
The specific structure of the round end cross structure is as follows: arm length l perpendicular to four sides of square unit is made at midpoint of square unit with side length p 1 And is a cross copper patch 10 of width w. The center copper patch is arranged by taking the middle points of the tail ends of the four arms of the cross structure as the center of a circle and r as the radius. The thickness of the copper patch was 0.018mm. The outermost conductive layer substrate was supported by a PET substrate having a dielectric constant of 3.4 and a loss tangent of 0.005. The actual scene parameters of the indoor and outdoor glass media are respectively double-layer glass media with dielectric constant of 6.7 and loss tangent of 0.012.
The equivalent circuit method can be known that the equivalent circuit of the patch type FSS structure at the lower right corner in fig. 2 is that the capacitor and the inductor are connected in series, and the equivalent circuit of the slot type FSS structure at the upper right corner in fig. 2 is that the capacitor and the inductor are connected in parallel.
The windmill structure is equivalent to the parallel connection of LC series circuits, the round end cross structure is equivalent to the LC series circuits, and the middle two layers of glass and the air layer 4 are equivalent to transmission lines; according to the principle of multi-layer cascading, the equivalent circuit of the FSS structure shown in figure 2 can be shown in figure 3. Wherein Z is 0 For free space characteristic impedance, Z 1 Is equivalent impedance of glass media.
The round end cross structure of the double-layer antireflection film generates low-frequency resonance, which is equivalent to an LC series circuit. Wherein L is 1 、C 1 ，L 2 、C 2 Respectively represent the structures of windmillsEfficient parallel LC cascade circuit, L 3 、C 3 Respectively refers to the equivalent capacitance and inductance of the round end cross structure. Series L 3 C 3 Resonant at frequency f 1 The windmill structure is coupled with the round end cross structure to generate high-frequency resonance;
i.e. L 1 C 1 、L 2 C 2 Parallel and then connected with L 3 C 3 At high frequency constitute a new parallel resonance at frequency f 2 A place; the corresponding resonant frequencies are respectively:
and (3) carrying out simulation analysis on parameters in the double-layer antireflection film:
(1) In FIG. 4 (a), r is the radius of the lower cross at the round end, and the step size is 0.3mm. It can be seen that the radius r has a large effect on the pass band resonance frequency. With the increase of radius r, equivalent capacitance C of lower round end cross unit 3 Increase of series resonance frequency f 2 Moving to lower frequencies. However, in order to ensure that the wave-transparent frequency band covers 4.8GHz-4.9GHz, r=0.8 mm is finally selected;
(2) In FIG. 4 (b), l 1 The step length is 0.5mm for the length of the cross branch of the lower unit. l (L) 1 The resonance frequency and the wave-transmitting loss of the wave-transmitting passband are greatly influenced. With length l 1 Is increased, equivalent inductance L of lower round end cross unit 3 Increase of series resonance frequency f 2 Moving to lower frequencies. Reducing step after comprehensively considering wave-transmitting frequency band and wave-transmitting rate to finally select l 1 ＝3.2mm；
(3) In fig. 4 (c), the pitch l of the upper layer windmill structure 3 The lower limit of the wave-transparent frequency band is determined, and the distance l is followed 3 Is increased by the upper layer unit equivalent capacitance C 1 The value is reduced, thereby the series resonance frequency f 1 Bias to higher frequenciesThe bandwidth of the wave transmission band is increased but the wave transmission rate is gradually reduced. Final selection of l 3 ＝2.2mm。
The structural parameters were determined via the simulation result analysis described above as shown in table 1.
In order to more intuitively understand the working principle of the structure of each layer of antireflection film unit, fig. 5 shows the surface current distribution of each layer of unit under three resonance modes (4.8 GHz, 4.9GHz and 5.4 GHz). In 4.8GHz and 4.9GHz resonance modes, the induced current flowing through the upper windmill structure is weak, the induced current on the cross of the round end of the lower layer is strong, the vertical polarization can be equivalent to inductance, and the series resonance frequency f is increased along with the increase of the length of the cross branch 2 Shift to low frequency; in the 5.4GHz resonance mode, the upper windmill structure and the lower round end cross have stronger induced current, which means that the upper unit and the lower unit are mutually coupled, and the parallel resonance is carried out at the frequency f 2 Where it is located.
Because the double-layer antireflection films are adhered to the inner side and the outer side of the glass medium, the influence on the indoor light transmittance still needs to be considered on the premise of improving the electromagnetic wave transmittance. The substrate of the designed double-layer FSS antireflection film medium adopts a PET substrate and is subjected to light transmission treatment, the light transmittance can reach about 80%, the double-layer patch unit shown in fig. 2 is subjected to hollowing treatment for further improving the light transmittance, the hollowing is designed as shown in fig. 6, the reflection coefficient curve and the transmission coefficient curve of the double-layer FSS antireflection film medium are simulated and analyzed, and the final double-layer antireflection film structure is determined by comparison.
The unit structure and the electromagnetic property of the double-frequency dual-polarized digital coding super-surface are provided. The application is further illustrated below with reference to specific examples.
Table 1 double layer anti-reflection film structural size (mm)
Example 1: by simulating the units in CST, the influence of incident waves with different angles on S parameters is tested, and S21 and insertion loss of the initial non-hollowed windmill structure and the hollowed windmill structure are analyzed.
Simulation analysis was performed on the three-dimensional model structure after the "hollowed-out" treatment, and the results are shown in table 2. S21 is improved by 4.3dB-5.7dB compared with the state of a glass medium when TE polarized electromagnetic waves are normally incident, S21 is improved by 5.22dB-5.71dB when the TE polarized electromagnetic waves are incident at 30 degrees, and S21 is improved by 1.71dB-3.65dB when the TE polarized electromagnetic waves are obliquely incident at 60 degrees with larger insertion loss; the S21 at the incidence of the TM polarization of 60 degrees has a 0.6dB drop compared with the state of the glass medium at maximum, and the passband is shifted to the low-frequency direction, but the drop of the wave transmission loss is smaller, so that the corresponding S21 value at the incidence of 0-60 degrees is raised to be within-3.6 dB.
TABLE 2 glass media and "hollowed-out" Structure S 21 Data comparison table
As can be seen by comparing the original design of the double-layer antireflection film with the simulation data after the "hollowing" treatment, the hollowing part is actually a correction to the windmill structure, and the original structure is hollowed out in consideration of the light transmittance of the glass.
After the windmill structure is hollowed out, m is as follows 1 ＝3.4mm，m 2 =4.8 mm, where m 1 For the height, m of the middle-waist triangle copper patch of the windmill gap 2 The bottom of the middle triangle copper patch is the windmill gap.
The change trend of the design after the hollowing-out treatment is basically consistent with that of the original design under two polarizations, and the design shows that TE polarization wave-transmitting loss is improved to different degrees under different incidence angles, but the inherent loss is large due to the overlarge glass thickness, so that the large-angle performance is not greatly optimized; the original large-angle wave-transmitting performance is better under TM polarization, and the overall insertion loss can be kept within-3.6 dB even though the lifting value is smaller. The difference is that the original impedance matching degree is reduced after the hollowing out of the unit structure, so that the wave-transparent insertion loss is reduced compared with that before the hollowing out, but the reduction amplitude is smaller, and the maximum reduction amplitude is only 0.2dB. Therefore, the structural design after the hollowing realizes the improvement of the light transmittance by increasing the wave transmission loss by 0.2dB.
Simulation analysis the relative surface impedance of the bilayer anti-reflection film for the "hollowed out" design described above is shown in figure 9. On the interface between the free space and the medium, when the medium impedance is equal to the free space wave impedance, the interface reflection coefficient is 0, and the transmission reaches the maximum, namely the impedance matching is realized. As can be seen from fig. 9, the relative surface impedance is in the frequency band of 4.8GHz to 4.9GHz, the real part tends to be 1, and the imaginary part tends to be 0. Therefore, the designed anti-reflection film impedance is between the free space impedance and the glass medium impedance, namely, the wave transmittance is improved to the maximum extent by realizing impedance matching.
Example 2:
the transmission coefficients of different angles under the light transmittance and actual measurement conditions are obtained by processing the real objects of the units and testing the real objects, and factors which possibly generate errors in the experimental process are analyzed.
To verify the designed dual-layer anti-reflection film based on the frequency selective surface, two-layer anti-reflection film samples, each having a size of 470mm by 470mm and each comprising 52 by 52 units, were processed according to the structure designed after the "hollowed-out" treatment, as shown in fig. 10. The upper diamond ring structure and the lower round end cross structure are printed on PET medium base material with thickness of 0.05mm (epsilon) r =3.4, tan δ=0.005) and an optical OCA glue (epsilon) with a thickness of 0.05mm was coated on top r =3.8, tan δ=0.005), the outer layer of the PET substrate and the outer layer of the optical OCA glue are both adhered with a protective film, and when in use, the outer protective film is torn off to be adhered on the glass medium.
The transmittance of the PET medium substrate can reach 80%, in order to further increase the transmittance of the antireflection film, the unit structure adopts a grid processing technology instead of etching the patch, and the unit processing details are shown in fig. 11. The bottom gray is the background color used for the display unit processing details.
Two layers of antireflection films are respectively stuck on two sides of glass, and the double-layer glass is divided into outdoor glass 3, an inner air layer 4 and indoor glass 5. Since the FSS antireflection film is divided into two layers, and the two layers are different and need to be adhered to the inner and outer layers of the glass, the layer of the double glazing close to the outside (outdoor glass 3) is distinguished from the layer of the double glazing close to the inside (indoor glass 5) in the above description.
The transmission coefficient was measured in a microwave darkroom, and the actual test scenario is shown in fig. 12. Firstly, the transmission coefficient of an air window with the same size as a sample in an incidence state of 0-60 degrees is tested, as shown in fig. 12 (a), the center of the testing tool window is aligned to the centers of two horn antennas (the working frequency band is 1-18 GHz), the two horn antennas are respectively connected to two ports of a vector network analyzer (Vector network analyzer, VNA) agent N5230C, and the transmission coefficient between the two antennas is measured. The state of the antenna is kept unchanged, a glass medium is erected, an antenna with the thickness of 19mm is used as a transmitting antenna, an antenna with the thickness of 22mm is used as a receiving antenna, and the transmission coefficient under the incident state of 0-60 degrees is measured. The antenna state is still unchanged, the antireflection film sample is erected, as shown in fig. 12 (b), one side of the diamond ring unit faces the transmitting horn antenna, the round end cross unit faces the receiving horn antenna, and the transmission coefficient under the incidence state of 0-60 degrees is measured. The transmission coefficient of the glass medium and the antireflection film is the difference between the measurement result and the measurement result of the transmission coefficient of the air window.
To verify the wave transmission characteristics of the designed antireflection film, the transmission coefficient test data of the glass medium and the antireflection film under three angles of 0 degree, 30 degree and 60 degree are respectively selected for comparison, and comparison curves are shown in fig. 13-15. The characteristic that the S parameter curve loaded with the antireflection film is offset to the low-frequency band compared with the S parameter curve of the glass medium in the frequency band of 4.8GHz-4.9GHz is also consistent with the simulation result, and the insertion loss after the antireflection film is loaded is obviously improved compared with the glass medium. The test data of the S parameters of the glass medium and the antireflection film are offset to a high frequency relative to the simulation data, and the possible causes of errors are as follows: the processed glass medium size is 500mm multiplied by 500mm, the processed size of the anti-reflection film is 470mm multiplied by 470mm, and the two anti-reflection films are difficult to align when being adhered, so that the dislocation problem exists; when the antireflection film is stuck, bubbles are generated due to the fact that the antireflection film is not stuck tightly; there are errors in the thickness processing of the glass media. But the test and simulation results verify the wave-transparent characteristics of the antireflection film.
In the application, the conductive layer substrate adopts a PET substrate with a dielectric constant of 3.4 and a loss tangent of 0.005, and the colloid is stuck on two sides of glass by adopting OCA colloid. It is understood that the same or similar results can be achieved by changing the substrate, changing the gel material, and changing the double vacuum glass to other types of glass, and should be considered as the scope of the present application.
The units shown in fig. 2 or fig. 6 are duplicated by any number in the x direction and the y direction in the proportion of n multiplied by n, and the center-to-center spacing between adjacent units in the x direction and the y direction is p, so that the super-surface array can be formed.
The application designs the array to be 52×52 units, the array size is 470×470mm, and similar performances can be achieved by changing the number of units or changing the size of the hollowed-out part.
The scope of the present application is not limited thereto, and any changes, substitutions or alterations herein are readily contemplated as would be within the spirit and scope of the present application. Therefore, the above mentioned changes and substitutions should also be considered as the protection scope of the present application.
Claims (10)
1. The passive RIS antireflection film based on the frequency selective surface is characterized by comprising an outdoor conducting layer substrate (1), an outdoor conducting layer (2), outdoor glass (3), an air layer (4), indoor glass (5), an indoor conducting layer (6) and an indoor conducting layer substrate (7) which are sequentially arranged along the incoming wave direction; wherein, the outdoor conducting layer substrate (1) close to the outdoor glass (3) is in a windmill structure;
the windmill structure comprises a square base material, wherein two crossed gap structures are arranged on the surface of the base material along the diagonal position of the square base material;
the indoor conducting layer (6) close to the indoor glass (5) is of a round-end cross structure;
the round-end cross structure comprises a square base material, wherein the center of the square base material is provided with a cross copper patch (10), and the end part of the cross copper patch (10) is provided with a round copper patch (11).
2. A according to claim 1The passive RIS antireflection film based on the frequency selective surface is characterized in that the specific structure of the windmill structure is as follows: comprises a square base material with a side length of p, wherein the midpoints of four sides of the square base material are provided with isosceles triangle copper patches I (8), wherein the isosceles triangle copper patches I (8) are formed by (p-l) 3 ) 2 is high, l 3 Representing the vertex spacing of an isosceles triangle enclosing the windmill structure;
four corners of the square base material are isosceles triangle copper patches II (9), and the right-angle side length of the isosceles triangle copper patches II (9) is d;
the specific structure of the round end cross structure is as follows: comprises a square base material with a side length p, wherein the cross copper patch (10) is perpendicular to the square base material, and the arm length l 1 And the width is w, and the circular copper patch (11) takes r as the radius.
3. The passive RIS antireflection film based on a frequency selective surface according to claim 2, wherein an isosceles triangle is formed in four directions of up, down, left and right of the windmill structure of a square unit with a side length p, and the bottom side length of the isosceles triangle is l 2 。
4. A passive RIS antireflection film based on a frequency selective surface according to claim 1, wherein the windmill structure is attached to the outdoor glass (3) by an optical OCA glue, and the round end cross structure is attached to the indoor glass (5) by an optical OCA glue.
5. A passive RIS antireflection film based on a frequency selective surface according to claim 1, characterized in that the outdoor conductive layer substrate (1) and the indoor conductive layer substrate (7) are supported by a PET substrate with a dielectric constant of 3.4 and a loss tangent of 0.005 as a medium; the glass media of the outdoor glass (3) and the indoor glass (5) adopt actual scene parameters, and are double-layer glass media with dielectric constant of 6.7 and loss tangent of 0.012.
6. A passive RIS anti-reflection film based on a frequency selective surface according to claim 1, whichCharacterized in that in the two-layer patch type FSS structure formed by the windmill structure and the round end cross structure, different layers of the FSS unit are equivalent to mutually cascaded circuits, the equivalent circuit method is to equivalent a frequency selective surface to be an inductance or capacitance element, and the windmill structure is equivalent to L 1 C 1 And L is equal to 2 C 2 Parallel connection and round end cross structure equivalent to series circuit L 3 C 3 The middle part comprises outdoor glass (3), an air layer (4) and indoor glass (5) which are equivalent to transmission lines, L 1 C 1 And L is equal to 2 C 2 In parallel, with characteristic impedance Z 1 Will L 3 C 3 And the parallel circuit is connected with the circuit by a characteristic impedance Z 0 Wherein Z is connected to an external circuit 0 For free space characteristic impedance, Z 1 Equivalent impedance for glass medium;
the round end cross structure of the double-layer antireflection film generates low-frequency resonance, which is equivalent to an LC series circuit; wherein L is 1 、C 1 ，L 2 、C 2 Parallel LC cascade circuits, L, respectively representing the structural equivalence of windmills 3 、C 3 Respectively refers to a capacitance and an inductance equivalent to the round end cross structure; series L 3 C 3 Resonant at frequency f 1 The windmill structure is coupled with the round end cross structure to generate high-frequency resonance;
L 1 C 1 、L 2 C 2 parallel and then connected with L 3 C 3 At high frequency constitute a new parallel resonance at frequency f 2 A place; the corresponding resonant frequencies are respectively:
the parameters in the windmill structure and the round end cross structure are adjusted, which is equivalent to the adjustment of the equivalent impedance of the antireflection film based on the frequency selective surface, so that the antireflection film can achieve impedance matching with two layers of media of indoor glass (5) and outdoor glass (3) in the air, and the antireflection of indoor stadium signals is realized.
7. The passive RIS antireflection film based on a frequency selective surface of claim 1, wherein the passive RIS antireflection film replicates an arbitrary number in the x-direction and the y-direction in a proportion of n×n, and the center-to-center spacing between adjacent units in the x-direction and the y-direction is p, so that the passive RIS antireflection film can be a super-surface array.
8. A passive RIS antireflection film based on a frequency selective surface according to claim 1, wherein the windmill structure is characterized in that the edges of the windmill structure are hollowed out in consideration of the transparency of the glass itself, and the size of the hollowed out representation is divided into m after the windmill structure is hollowed out 1 And m 2 ，m 1 For the height, m of the middle-waist triangle copper patch of the windmill gap 2 The bottom of the middle triangle copper patch is the windmill gap.
9. The method for adjusting a passive RIS antireflection film based on a frequency selective surface according to any of claims 1 to 8, wherein adjusting parameters in a windmill structure and a round end cross structure to achieve impedance matching comprises the steps of;
step one: numerical simulation is carried out on the FSS antireflection film by using commercial electromagnetic simulation software CST Microwave;
step two: r is the radius of the lower round end cross of the round end cross structure, and the equivalent capacitance C of the lower round end cross unit is increased along with the increase of the radius r 3 Increase of series resonance frequency f 2 Move to lower frequency, S 21 The peak value is more obvious, the transition zone becomes steeper along with the radius increase, and the wave transmission rate is reduced;
step three: l (L) 1 Is a lower layer single L with a round end cross structure 3 C 3 Length of the meta-cross branch along with length l 1 Is increased, the lower round end cross unit is equalEffective inductance L 3 Increase of series resonance frequency f 2 Move to lower frequency and S at resonance frequency 21 The wave transmission rate is gradually reduced;
step four: spacing l of upper windmill structure 3 The lower limit of the wave-transparent frequency band is determined, and the distance l is followed 3 Is increased by the upper layer unit equivalent capacitance C 1 The value is reduced, thereby the series resonance frequency f 1 Shifting to higher frequencies, the bandwidth of the transmission band increases but the transmission rate gradually decreases;
by adjusting the above parameters, the equivalent capacitance C in the cell is changed 1 And equivalent inductance L 3 Thereby changing the equivalent impedance of the antireflection film and achieving impedance matching.
10. A passive RIS anti-reflection film based on a frequency selective surface according to any of claims 1-8, applied to 5G communication, the anti-reflection film being glued on both sides of the outdoor glass (3), indoor glass (5) medium, the signal being sent by the base station, transmitted to the indoor venue via the passive RIS, the passive RIS surface changing the direction of the reflected main beam by adjusting the reflection phase of the radiating element;
on the interface between the free space and the medium, when the medium impedance is equal to the free space wave impedance, the interface reflection coefficient is 0, and the transmission reaches the maximum, namely the impedance matching is realized. The process that the medium passes through the passive RIS and enters the room is used for improving path loss and diffraction loss caused by a part of complex buildings, and the anti-reflection film adhered on the glass medium is used for realizing impedance matching with free space, so that the wave transmission loss is reduced, the signal transmittance is increased, and the coverage of indoor signals is enhanced.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117458161A (en) * | 2023-12-21 | 2024-01-26 | 江苏赛博空间科学技术有限公司 | 5G frequency band electromagnetic wave transmission enhancement structure of double-layer hollow glass |
| CN117479521A (en) * | 2023-12-27 | 2024-01-30 | 江苏赛博空间科学技术有限公司 | Electromagnetic shielding structure of wave-transparent material |
| CN117769235A (en) * | 2023-12-29 | 2024-03-26 | 江苏赛博空间科学技术有限公司 | Metal pattern functional layer structure for realizing electromagnetic wave attenuation |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117458161A (en) * | 2023-12-21 | 2024-01-26 | 江苏赛博空间科学技术有限公司 | 5G frequency band electromagnetic wave transmission enhancement structure of double-layer hollow glass |
| CN117458161B (en) * | 2023-12-21 | 2024-04-05 | 江苏赛博空间科学技术有限公司 | 5G frequency band electromagnetic wave transmission enhancement structure of double-layer hollow glass |
| CN117479521A (en) * | 2023-12-27 | 2024-01-30 | 江苏赛博空间科学技术有限公司 | Electromagnetic shielding structure of wave-transparent material |
| CN117479521B (en) * | 2023-12-27 | 2024-05-28 | 江苏赛博空间科学技术有限公司 | Electromagnetic shielding structure of wave-transparent material |
| CN117769235A (en) * | 2023-12-29 | 2024-03-26 | 江苏赛博空间科学技术有限公司 | Metal pattern functional layer structure for realizing electromagnetic wave attenuation |
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