A frequency selective surface structure for 5G frequency bands and a unit structure thereof

Abstract

This invention provides a frequency selective surface structure and its unit structure for 5G frequency bands. The unit structure, from top to bottom, includes a first metal layer, a dielectric substrate, an air layer, and a second metal layer. A rectangular ring structure and four metal plates are formed on the first metal layer. The metal plates surround the rectangular ring structure and are connected to the four corners of the inner ring of the rectangular ring structure. The four metal plates radiate outwards along the diagonals of the rectangular ring structure, and curl inwards along their four sides to form gaps within the metal plates. A cross-shaped annular gap is formed on the second metal layer. The frequency selective surface structure includes M×N periodically arranged unit structures. The frequency selective surface structure exhibits good absorption characteristics in the 2.15GHz to 5.55GHz and 6.2GHz to 9GHz frequency bands, and good transmission characteristics in the 5.84GHz to 5.94GHz frequency band. It also has good angular stability; when the incident wave is incident at different angles under different polarization modes, the resonant frequency remains within the 5G frequency band.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic fields and electromagnetic waves, and in particular to a frequency selective surface structure and its unit structure for 5G frequency bands. Background Technology

[0002] A frequency selective surface (FSS) is an artificial periodic structure, essentially a periodic surface composed of specific unit structures arranged in a specific order. It can achieve bandpass and bandstop responses to electromagnetic waves in space. An FSS allows low-loss transmission of incident electromagnetic waves in a specific frequency band, while reflecting out-of-band electromagnetic waves internally, thus it can be considered a type of spatial filter.

[0003] FSS (Flat Radome) was once widely used as a radome in antenna systems to effectively reduce mutual interference between antennas and improve antenna performance. In early single-base station military detection, FSS could reduce radar cross-section and achieve stealth by reflecting electromagnetic waves in other directions.

[0004] With the continuous development of anti-stealth technology in the field of electronic warfare in modern warfare, radar technology, such as multi-base station radar, which can receive radar signals scattered from the target in all other directions, is becoming increasingly widespread. Frequency selective surface (FSS) stealth radomes will easily lose their stealth capabilities. To address this new requirement for stealth capability, an integrated absorber-transmitter frequency selective surface (FSS) with in-band transmission and out-of-band absorption characteristics has been proposed. We can combine an absorber based on artificial electromagnetic materials with a traditional FSS to create a new type of frequency selective surface—an absorbing / transmitting frequency selective surface. The main function of a traditional FSS is to reflect out-of-band signals in other directions. However, with the development of radar anti-stealth technology, these reflected signals may be detected by enemy radar, especially since strong reflections in a particular direction increase the risk of revealing our position. For the new absorbing / transmitting frequency selective surface, out-of-band signals are absorbed instead of reflected, which greatly reduces security risks and improves combat performance. This is the original intention behind designing the absorbing / transmitting frequency selective surface.

[0005] 5G (5th Generation Mobile Networks), also known as 5th Generation Wireless Systems, is the next generation evolution of 4G. Domestic expectations for key 5G indicators and characteristics include: peak speeds reaching tens of Gbps, end-to-end latency down to 1ms (millisecond level), high spectrum utilization, low energy consumption, etc., ushering in the era of intelligent internet development from the mobile internet era. During communication, if traditional frequency selective absorbers / reflectors are used, out-of-band signal reflections will introduce more electromagnetic noise in different directions. Simultaneously, electromagnetic interference in the environment is distributed across various frequency bands, thus creating a strong demand for wideband shielded surface selective filters (FSS).

[0006] To address the aforementioned issues, frequency selective surfaces (FSS) can be applied to the 5G band to ensure reliable signal transmission and prevent frequency interference. Currently, there is research on applying FSS to 5G band transmission, but this research mainly focuses on passband structures with distributed stopbands or structures with narrow stopband bandwidths. This does not meet the current development trend of integrated passband and wide absorption band frequency selective surfaces. Furthermore, existing FSS structures applied to the 5G band also suffer from poor stability, resulting in poor filtering characteristics. Summary of the Invention

[0007] The purpose of this invention is to provide a frequency selective surface structure and its unit structure for 5G bands, achieving good wave transmission characteristics within the 5.84GHz to 5.94GHz frequency band; allowing signals within the band to pass through while blocking signals outside the band, thus protecting 5G band signals from interference by electromagnetic signals of other frequencies. Absorption is achieved over a relatively wide frequency band, exhibiting good absorption characteristics in the 2.15GHz to 5.55GHz and 6.2GHz to 9GHz frequency bands.

[0008] The technical solution for achieving the objective of this invention is as follows:

[0009] One aspect of the present invention provides a frequency selective surface structure unit structure for 5G frequency bands, which includes, from top to bottom, a first metal layer, a dielectric substrate, an air layer and a second metal layer.

[0010] The first metal layer has a rectangular ring structure and four metal plates. The metal plates surround the rectangular ring structure and are connected to the four corners of the inner ring of the rectangular ring structure. The four metal plates radiate outward along the diagonal of the rectangular ring structure. The metal plates are quadrilateral and are rolled inward along their four sides to form gaps.

[0011] A cross-shaped annular slit is formed on the second metal layer, and the cross-shaped annular slit is oriented diagonally to the second metal layer.

[0012] Both the first metal layer and the second metal layer are centrally symmetrical structures. The center of the rectangular ring structure, the center of the four metal plates, and the center of the cross-shaped annular gap all coincide with the center of the first metal layer and the center of the second metal layer.

[0013] In one embodiment of the present invention, a rectangular ring structure is loaded with four loading resistors.

[0014] In one embodiment of the present invention, the rectangular ring structure is a square ring, and the diagonal direction of the rectangular ring structure is consistent with the diagonal direction of the first metal layer.

[0015] In one embodiment of the present invention, each of the four metal plates has two long sides of equal length and two short sides of equal length. The short sides are parallel to the four sides of the first metal layer, and the long sides coincide with the four corners of the square boundary inside the rectangular ring structure. The metal plates are radially distributed along the diagonal of the first metal layer.

[0016] In one embodiment of the present invention, the gap is a resonant groove, the resonant groove located on the first metal layer is parallel to the edge of the first metal layer, and each resonant groove is symmetrically distributed along the diagonal axis of the first metal layer.

[0017] Half of the resonant groove starts from the vertex of the rectangular ring structure, extends along the direction parallel to the long side of the first metal layer, bends near the edge of the first metal layer, turns to be parallel to the short side of the first metal layer, then turns again near the diagonal of the first metal layer, bends inward and turns to be parallel to the diagonal of the first metal layer, and terminates after extending for a certain distance.

[0018] The other half of the resonant groove is symmetrically distributed along the diagonal of the first metal layer.

[0019] In one embodiment of the present invention, the cross-shaped annular slits are oriented along the diagonal of the second metal layer.

[0020] In one embodiment of the present invention, the dielectric substrate has a dielectric constant close to that of air and a thickness of 1 mm.

[0021] In one embodiment of the present invention, the air layer is 12 mm thick, and the total distance between the first metal layer and the second metal layer is 13 mm.

[0022] Another aspect of the present invention provides a frequency selective surface structure for 5G bands, comprising M×N periodically arranged frequency selective surface structure unit structures, wherein the frequency selective surface structure unit structure is a frequency selective surface structure unit structure for 5G bands as described above.

[0023] Where M and N are integers greater than or equal to 1.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. The frequency-selective surface structure of this invention can achieve absorption over a wide frequency band. It exhibits good absorption characteristics in the 2.15 GHz to 5.55 GHz frequency band and the 6.2 GHz to 9 GHz frequency band.

[0026] 2. The frequency selective surface structure of the present invention can achieve good wave transmission characteristics (both absorption and transmission rates are above 80%) in the 5G frequency band from 5.84GHz to 5.94GHz; allowing signals within the frequency band to pass through while blocking signals outside the frequency band, thus protecting 5G frequency band signals from interference by electromagnetic signals of other frequencies.

[0027] 3. The frequency selective surface structure of the present invention has good angular stability. When irradiated by incident waves at different angles, the deviation of the first resonant frequency and the deviation of the second resonant frequency are within an acceptable range and are always within the 5G frequency band. The absorption efficiency is still over 80% when the incident angle is 30 degrees. Attached Figure Description

[0028] Figure 1 This is a three-dimensional perspective view of a frequency selection surface structure unit structure for 5G frequency bands provided in an embodiment of the present invention;

[0029] Figure 2 This is a side view of a frequency selection surface structure unit structure for 5G frequency bands provided in an embodiment of the present invention;

[0030] Figure 3 This is a front view of the first metal layer in a frequency selection surface structure unit structure for 5G frequency bands provided in an embodiment of the present invention;

[0031] Figure 4 This is a front view of the second metal layer in a frequency selection surface structure unit structure for 5G frequency bands provided in an embodiment of the present invention;

[0032] Figure 5 This is a three-dimensional perspective view of a frequency selection surface structure unit structure for 5G frequency bands provided in an embodiment of the present invention;

[0033] Figure 6This is a simulation diagram of the filtering performance of a frequency selective surface structure for 5G bands provided in an embodiment of the present invention;

[0034] Figure 7 This is a simulation diagram of the angular stability performance of the transmittance of a frequency-selective surface structure for 5G frequency bands provided by an embodiment of the present invention;

[0035] Figure 8 This is a simulation diagram of the absorption rate angle stability performance of a frequency selective surface structure for 5G frequency bands provided by an embodiment of the present invention;

[0036] Figure 9 Detailed geometric parameters of the metal layer provided in the embodiments of the present invention;

[0037] Figure 10 The angular stability simulation parameters of the FSS structure provided by this invention in TE mode;

[0038] Figure 11 The surface current distribution of the damaged layer when the incident electromagnetic wave frequency is 2.8 GHz;

[0039] Figure 12 The surface current distribution of the damaged layer when the incident electromagnetic wave frequency is 5.9 GHz;

[0040] Figure 13 The surface current distribution of the damaged layer when the incident electromagnetic wave frequency is 8.4 GHz;

[0041] Figure 14 The surface current distribution of the damaged layer when the incident electromagnetic wave frequency is 5.0 GHz;

[0042] Figure 15 The surface current distribution of the lossless layer when the incident electromagnetic wave frequency is 2.8 GHz;

[0043] Figure 16 The surface current distribution of the lossless layer when the incident electromagnetic wave frequency is 5.9 GHz;

[0044] Figure 17 The surface current distribution of the lossless layer when the incident electromagnetic wave frequency is 8.4 GHz;

[0045] Reference numerals: 1-First metal layer; 11-Metal plate; 111-Resonant groove; 12-Rectangular ring structure; 13-Loading resistor; 2-Dielectric substrate; 3-Air layer; 4-Second metal layer; 41-Cross-shaped annular gap. Detailed Implementation

[0046] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following describes in detail the integrated frequency selective surface structure and its unit structure for 5G frequency bands proposed according to the present invention, in conjunction with the accompanying drawings and specific embodiments.

[0047] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0048] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes that element.

[0049] Example 1:

[0050] Please see Figure 1 and Figure 2 This invention provides a frequency selection surface structure unit structure for 5G frequency bands, comprising, from top to bottom, a first metal layer 1, a dielectric substrate 2, an air layer 3, and a second metal layer 4. The first metal layer 1 has a rectangular ring structure 12 and four metal plates 11. The metal plates 11 surround the rectangular ring structure 12 and are connected to the four corners of the inner ring of the rectangular ring structure 12. The four metal plates 11 radiate outwards along the diagonal of the rectangular ring structure 12. The metal plates 11 are quadrilaterals, and gaps are formed within the metal plates 11 by curling inwards along their four sides. The second metal layer 4 has a cross-shaped annular gap 41, oriented along the diagonal of the second metal layer 4. Both the first metal layer 1 and the second metal layer 4 are centrally symmetrical structures, with the center of the rectangular ring structure 12, the center of the four metal plates 11, and the center of the cross-shaped annular gap 41 coinciding with the center of the first metal layer 1 and the center of the second metal layer 4.

[0051] Please see Figures 1 to 3 , Figure 1 This is a three-dimensional perspective view of a frequency selection surface unit structure applied to the 5G frequency band provided in an embodiment of the present invention; Figure 2This is a side view of a frequency selection surface unit structure applied to the 5G frequency band provided in an embodiment of the present invention; Figure 3 This is a front view of a frequency selective surface unit (SSU) structure metal layer provided in an embodiment of the present invention. The SSU structure of this embodiment includes, from top to bottom, a first metal layer 1, a dielectric substrate 2, an air layer 3, and a second metal layer 4. In this embodiment, the surface dimensions of the first metal layer 1, the dielectric substrate 2, and the second metal layer 4 are all 25mm*25mm. Furthermore, the thickness of the dielectric substrate 2 is 1mm, and the thicknesses of the first metal layer 1 and the second metal layer 4 are in the range of 0.017mm-0.035mm.

[0052] Please continue reading. Figure 1 and Figure 2 The frequency selection surface structure unit structure for 5G bands described above preferably has a rectangular ring structure 12 loaded with four loading resistors 13.

[0053] Furthermore, the first metal layer 1 has a rectangular ring structure 12 loaded with four 180Ω resistors 13 and four quadrilateral metal plates. The metal plates surround the ring and are connected to the four corners of its inner ring, radiating outward along the diagonal. There are gaps in the metal plates that curl inward along the four sides of the metal plates.

[0054] Please continue reading. Figure 1 and Figure 2 The frequency selection surface structure unit structure for 5G bands described above preferably has a rectangular ring structure 12 that is a square ring, with the diagonal direction of the rectangular ring structure 12 being consistent with the diagonal direction of the first metal layer 1.

[0055] Furthermore, the second metal layer is based on a full metal plate 4, on which a cross-shaped annular slit 41 is formed, with the cross oriented along the diagonal. Both the first metal layer 1 and the second metal layer 4 are centrally symmetrical structures, and the center of the rectangular ring structure, the center of the four radial metal plates, and the geometric center of the cross-shaped annular slit of the second metal layer all coincide with the center of the metal layer. The rectangular ring structure 12 is a square ring, with its diagonal direction consistent with the diagonal direction of the metal layer. The four quadrilateral metal plates 11 each have two long sides of equal length and two short sides of equal length. The short sides are parallel to the four sides of the metal plate, and the long sides coincide with the four corners of the square boundary inside the square ring. The metal plates are radially distributed along the diagonal of the metal layer.

[0056] Please continue reading. Figure 1 and Figure 2The frequency selection surface structure unit structure for 5G bands described above preferably has four metal plates 11, each with two long sides of equal length and two short sides of equal length. The short sides are parallel to the four sides of the first metal layer 1, and the long sides coincide with the four corners of the square boundary inside the rectangular ring structure 12. The metal plates 11 are radially distributed along the diagonal of the first metal layer 1.

[0057] Please continue reading. Figure 1 and Figure 2 The aforementioned frequency selection surface structure unit structure for 5G bands preferably has a slot as a resonant groove 111. The resonant groove 111 located on the first metal layer 1 is parallel to the edge of the first metal layer 1, and each resonant groove 111 is symmetrically distributed along the diagonal axis of the first metal layer 1. One half of the resonant groove 111 starts from the vertex of the rectangular ring structure 12, extends along the direction parallel to the long side of the first metal layer 1, bends near the edge of the first metal layer 1, turns parallel to the short side of the first metal layer 1, and then turns again near the diagonal of the first metal layer 1, bends inward and turns to be parallel to the diagonal of the first metal layer 1, and terminates after extending for a certain distance. The other half of the resonant groove 111 is symmetrically distributed along the diagonal of the first metal layer 1 with the other half of the resonant groove 111.

[0058] Furthermore, the resonant grooves 111 located on the metal sheet are parallel to the edge of the metal sheet. Each resonant groove is symmetrically distributed along the diagonal axis of the metal layer. One half of this structure starts near the vertex of the square ring, extends along a direction parallel to the long side of the metal sheet, bends near the edge of the metal sheet, turns parallel to the shorter side of the metal sheet, and then turns again near the diagonal of the metal layer, bending inward to become parallel to the diagonal of the metal layer, extending for a certain distance before terminating. The other half of this resonant groove is symmetrically distributed along the diagonal of the metal layer.

[0059] Please continue reading. Figure 1 and Figure 2 The frequency selection surface structure unit structure for 5G bands described above preferably has the cross-shaped annular slits 41 oriented along the diagonal of the second metal layer 4.

[0060] Please continue reading. Figure 1 and Figure 2 The aforementioned frequency selection surface structure unit structure for 5G bands preferably has a dielectric substrate 2 with a dielectric constant close to that of air and a thickness of 1 mm.

[0061] Please continue reading. Figure 1 and Figure 2 The aforementioned frequency selection surface structure unit structure for 5G bands preferably has an air layer 3 thickness of 12mm and a total distance of 13mm between the first metal layer 1 and the second metal layer 4.

[0062] Please see Figure 2 , Figure 3 , Figure 4 and Figure 9 , Figure 9 These are the detailed geometric parameters of the metal layer provided in the embodiments of the present invention.

[0063] The frequency-selective surface structure of this invention can achieve absorption over a wide frequency band. It exhibits good absorption characteristics in the 2.15GHz to 5.55GHz and 6.2GHz to 9GHz frequency bands. The frequency-selective surface structure of this invention can achieve good transmission characteristics (both absorption and transmission rates are above 80%) in the 5G band (5.84GHz to 5.94GHz), allowing signals within the band to pass through while blocking signals outside the band, thus protecting 5G band signals from interference from other frequency electromagnetic signals. The frequency-selective surface structure of this invention has good angular stability; the deviations of the first and second resonant frequencies are within acceptable ranges when irradiated by incident waves at different angles, always remaining within the 5G band, and the absorption efficiency still exceeds 80% at an incident angle of 30 degrees.

[0064] Example 2:

[0065] This embodiment provides a penetrating integrated frequency selective surface structure and its unit structure for use in the 5G band. The unit structure, from top to bottom, includes a first metal layer, an air foam board, an air layer, and a second metal layer. The first metal layer has a rectangular ring structure with four 180Ω resistors and four quadrilateral metal plates. The metal plates surround the rings and are connected to the four corners of their inner rings, radiating outwards along the diagonals. There are gaps within the metal plates that curl inwards along their four sides. The second metal layer is based on a full metal plate with a cross-shaped annular gap, the cross pointing diagonally. The center of the rectangular ring structure, the center of the four radial metal plates, and the geometric center of the cross-shaped annular gap in the second metal layer all coincide with the center of the metal layer. The foam board has a dielectric constant close to that of air and a thickness of 1 mm. Below the foam board is a 12 mm thick air layer. The total distance between the first and second metal layers is 13 mm. The penetrating integrated frequency selective surface structure includes M×N periodically arranged unit structures. The frequency-selective surface structure exhibits good absorption characteristics in the 2.15GHz to 5.55GHz and 6.2GHz to 9GHz frequency bands, and good transmission characteristics (both absorption and transmission rates are above 80%) in the 5.84GHz to 5.94GHz frequency band; it also has good angular stability, with the resonant frequency always within the 5GHz band when the incident wave is incident at different angles under different polarization modes.

[0066] Based on the above scheme, this embodiment of the invention provides a frequency selective surface structure for 5G bands, including M×N periodically arranged frequency selective surface structure unit structures. The frequency selective surface structure unit structure is a frequency selective surface structure unit structure for 5G bands according to Embodiment 1; wherein, M and N are integers greater than or equal to 1.

[0067] Furthermore, another embodiment of the present invention provides a frequency selective surface structure with integrated penetration-absorbing properties applied to the 5G frequency band; please refer to [link to relevant documentation]. Figure 5 , Figure 5 This is a three-dimensional perspective view of a frequency selective surface structure provided in an embodiment of the present invention. The frequency selective surface structure includes M×N periodically arranged frequency selective surface unit structures as described in any of the above embodiments, where M and N are integers greater than or equal to 1. In this embodiment, the frequency selective surface structure includes 10*10 unit structures; in other embodiments, the frequency selective surface structure may include 5×5, 20×20, 40×40, or even more unit structures.

[0068] To verify the performance of the frequency selective surface structure (FSS structure) in this embodiment of the invention, multiple performance simulation analyses were performed on the FSS structure using the commercial simulation software HFSS.

[0069] Please see Figure 6 , Figure 5 This is a simulation diagram of the filtering performance of an integrated absorber-permeable frequency selective surface structure applied to the 5G band, provided by an embodiment of the present invention.

[0070] The frequency-selective surface structure exhibits good absorption characteristics in the 2.15GHz to 5.55GHz and 6.2GHz to 9GHz frequency bands, and good transmission characteristics (both absorption and transmission rates are above 80%) in the 5.84GHz to 5.94GHz frequency band; it also has good angular stability, with the resonant frequency always within the 5GHz band when the incident wave is incident at different angles under different polarization modes.

[0071] like Figure 6 As shown in the transmittance curve, in the FSS structure of this embodiment, the resonant frequency of the resonant slot loaded on the first metal layer and the cross-shaped annular slot loaded on the second metal layer is 5.9 GHz, the transmittance can reach 90%, and the bandwidth is 100 MHz when the transmittance is above 80%. Figure 6 The absorption coefficient curves show that this frequency-selective surface structure exhibits good absorption characteristics in the 2.15 GHz to 5.55 GHz band and the 6.2 GHz to 9 GHz band, with an absorption rate exceeding 80%. Figure 6The reflectivity curves show that the reflectivity of this frequency-selective surface structure is below 20% in the 2.15 GHz to 9 GHz frequency band. In other words, in TE polarization mode, this structure exhibits good transmission performance for signals around 5.9 GHz and effectively resists interference from out-of-band signals and suppresses reflections throughout the passband and absorption band.

[0072] Furthermore, to investigate the angular stability of the integrated penetration-absorbing frequency selective surface structure of this invention applied to the 5G band, it was irradiated in TE mode with incident waves at incident angles of 0°, 15°, 25°, and 30° to obtain the frequency characteristics of the structure. Please refer to [further details omitted]. Figure 7 and Figure 8 , Figure 7 This is a simulation diagram of the angular stability performance of the transmission coefficient of an integrated absorber-transmitter frequency selective surface structure applied to the 5G band, provided by an embodiment of the present invention. Figure 8 This is a simulation diagram of the angular stability performance of the absorption coefficient of an integrated frequency selective surface structure for absorbing and penetrating the 5G band, provided by an embodiment of the present invention.

[0073] like Figure 7 As shown, the FSS structure exhibits good angular stability and excellent wave transmission characteristics at 5.9GHz (5.84GHz to 5.94GHz). Under electromagnetic incident wave illumination at different angles, the frequency deviation is within an acceptable range and remains within the 5G frequency band, demonstrating excellent signal transmission and anti-interference capabilities. Figure 10 These are the detailed geometric parameters for angular stability simulation of the transmission coefficient in embodiments of the present invention.

[0074] Furthermore, such as Figure 8 As shown, the FSS structure of this embodiment of the invention has strong angular stability and excellent wave absorption characteristics at ≤5.55GHz and ≥6.2GHz. Under electromagnetic incident wave illumination at different angles, the frequency deviation is within an acceptable range and is within the 5G signal frequency band, exhibiting excellent signal transmission capability and anti-interference capability.

[0075] Furthermore, comprehensive Figure 7 and Figure 8 Performance simulation diagrams and Figure 10 The simulation parameters show that, under TE mode, when the FSS structure of this embodiment is irradiated with incident waves at incident angles of 0°, 15°, 25°, and 30°, the resonant frequency and passband are always within the 5G frequency band, and it still has excellent filtering performance, which confirms that this structure has excellent angular stability.

[0076] In summary, the frequency selective surface structure of this invention has a dual-band bandpass effect, achieving good absorption characteristics in the 2.15GHz to 5.55GHz and 6.2GHz to 9GHz bands, and good transmission characteristics (both absorption and transmission rates are above 80%) in the 5.84GHz to 5.94GHz band. This allows signals within the band to pass through while blocking signals outside the band, protecting 5G signals from interference from electromagnetic signals of other frequencies.

[0077] Example 3:

[0078] This embodiment uses simulation to obtain and analyze the surface current distribution of the unit at the absorption frequency and the transmission frequencies located on both sides of the absorption frequency. Simulation analysis is performed on the current distribution of the damaged metal surface when the incident electromagnetic wave frequencies are 2.8 GHz, 5.9 GHz, and 8.4 GHz. The three selected frequency points are located in the low-frequency absorption band on the left, the mid-frequency passband, and the high-frequency absorption band on the right, respectively. The simulation results of the surface current at the three frequencies are shown in the figure. Figure 11 The surface current distribution of the lossy layer is shown when the incident electromagnetic wave frequency is 2.8 GHz. Figure 12 The surface current distribution of the lossy layer is shown when the incident electromagnetic wave frequency is 5.9 GHz. Figure 13 The surface current distribution of the lossy layer is shown when the incident electromagnetic wave frequency is 8.4 GHz. Figure 14 The surface current distribution of the lossy layer is shown when the incident electromagnetic wave frequency is 5.0 GHz. In the black metal region, the lighter color represents the current, and the lighter the color, the stronger the current.

[0079] As shown in the figure, when the incident wave frequency is 2.8 GHz, which is in the low-frequency absorbing band, the entire unit resonates. However, the resonance mainly occurs near the square ring patch, where a strong current is induced around the patch resistors. It is noteworthy that the current flows along the y-axis to the two resistors, and the current intensity on them is significantly higher than that on the two resistors with current flowing along the x-axis. This is because the polarization direction of the incident electromagnetic wave in the simulation is parallel to the y-axis, and the resistors in this direction have the same polarization direction as the electromagnetic wave, thus carrying a stronger current.

[0080] When the incident electromagnetic wave frequency is 5.9 GHz, which is in the central passband, the weak current in the patch resistor results in only a small loss for the incident electromagnetic wave. The absorption rate near the corresponding transmission frequency is still around 8%, but the remaining 90% is transmitted. Simultaneously, a strong current is generated on both sides of the resonant slot, which is a hallmark of electromagnetic waves passing through an aperture-type bandpass FSS.

[0081] When the incident electromagnetic wave frequency is 8.4 GHz, which is in the high-frequency absorbing band, a large amount of surface current is excited on the metal patch of the entire loss layer, especially at the central square ring patch with the applied resistor. Similar to the 2.8 GHz case, a large amount of current flows through the two resistors along the y-direction. The electromagnetic energy of the incident electromagnetic wave is excited into electrical energy, which is then converted into heat energy and dissipated after passing through the resistor, thus exhibiting the absorbing characteristics.

[0082] When analyzing the surface current of the loss layer at different incident frequencies, the following phenomenon was observed: when the incident frequency is 5 GHz, almost no current flows near the patch resistor. In fact, 5 GHz is the reflection band of the integrated absorber-reflector structure when the lower layer is an all-metal plate, i.e., the transmission frequency of the loss layer without interference from the lossless layer. At this point, the current flowing through the resistor in the loss layer is at its weakest, and the absorption rate of the integrated absorber-reflector structure is also at its lowest. However, after loading a bandpass structure into the lower layer, the passband frequency shifts due to the coupling effect between the loss layer and the lossless layer, changing to the current 5.9 GHz. The simulation results of the surface current of the loss layer under a 5 GHz incident wave are as follows: Figure 12 As shown.

[0083] The simulation results of the surface current of the non-destructive layer when the incident frequencies of the electromagnetic waves are the three mentioned above are shown in the figure. Figure 15 The surface current distribution of the lossless layer is shown when the incident electromagnetic wave frequency is 2.8 GHz. Figure 16 The surface current distribution of the lossless layer is shown when the incident electromagnetic wave frequency is 5.9 GHz. Figure 17 The image shows the surface current distribution of the lossless layer when the incident electromagnetic wave frequency is 8.4 GHz. In the image, the lighter colors on the black metal base represent current, with lighter colors indicating stronger current. It can be seen that when the incident wave frequency is 1.1 GHz, a large amount of surface current is excited in the region on both sides of the cross-shaped slot on the metal patch, indicating that the electromagnetic wave excites the cross-shaped slot to resonate and transmit, exhibiting passband characteristics. When the incident frequency is 2.8 GHz and 8.4 GHz, there is only a very weak surface current or no current on the metal, especially no resonance occurs on both sides of the cross-shaped annular resonant slot. This indicates that in the absorption band, the bandpass layer is similar to a metal plate, exhibiting total reflection characteristics for electromagnetic waves, and therefore no resonance occurs.

[0084] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0085] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0086] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A frequency-selective surface structure unit structure for 5G frequency bands, characterized in that, From top to bottom, it includes a first metal layer, a dielectric substrate, an air layer, and a second metal layer; The first metal layer has a rectangular ring structure and four metal plates. The metal plates surround the rectangular ring structure and are connected to the four corners of the inner ring of the rectangular ring structure. The four metal plates radiate outward along the diagonal of the rectangular ring structure. The metal plates are quadrilateral and are rolled inward along their four sides to form gaps. The rectangular ring structure is loaded with four load resistors. A cross-shaped annular slit is formed on the second metal layer, and the cross-shaped annular slit is oriented diagonally to the second metal layer. Both the first metal layer and the second metal layer are centrally symmetrical structures. The center of the rectangular ring structure, the center of the four metal plates, and the center of the cross-shaped annular gap all coincide with the center of the first metal layer and the second metal layer. Each of the four metal plates has two long sides of equal length and two short sides of equal length. The short sides are parallel to the four sides of the first metal layer, and the long sides coincide with the four corners of the square boundary inside the rectangular ring structure. The metal plates are distributed radially along the diagonal of the first metal layer. The gap is a resonant groove. The resonant groove located on the first metal layer is parallel to the edge of the first metal layer. Each resonant groove is symmetrically distributed along the diagonal axis of the first metal layer. Half of the resonant groove starts from the vertex of the rectangular ring structure, extends along the direction parallel to the long side of the first metal layer, bends near the edge of the first metal layer, turns to be parallel to the short side of the first metal layer, then turns again near the diagonal of the first metal layer, bends inward and turns to be parallel to the diagonal of the first metal layer, and terminates after extending for a certain distance. The other half of the resonant groove is symmetrically distributed along the diagonal of the first metal layer.

2. The frequency selective surface structure unit structure for 5G frequency bands according to claim 1, characterized in that, The rectangular ring structure is a square ring, and the diagonal direction of the rectangular ring structure is consistent with the diagonal direction of the first metal layer.

3. The frequency selective surface structure unit structure for 5G frequency bands according to claim 1, characterized in that, The cross-shaped annular slits are oriented along the diagonal of the second metal layer.

4. The frequency selective surface structure unit structure for 5G frequency bands according to claim 1, characterized in that, The dielectric substrate has a dielectric constant close to that of air and a thickness of 1 mm.

5. A frequency selective surface structure unit structure for 5G frequency bands according to claim 1, characterized in that, The air layer is 12 mm thick, and the total distance between the first metal layer and the second metal layer is 13 mm.

6. A frequency selection surface structure for 5G frequency bands, characterized in that, include A periodically arranged frequency selective surface structure unit structure, wherein the frequency selective surface structure unit structure is a frequency selective surface structure unit structure for 5G band as described in any one of claims 1-5; Where M and N are integers greater than or equal to 1.

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