A miniaturized broadband transmittance integrated frequency selective surface

Abstract

This invention discloses a miniaturized broadband wave-transmitting and wave-absorbing integrated frequency selective surface, belonging to the field of artificial metamaterials. This wave-absorbing and wave-absorbing integrated surface consists of a loss layer and a frequency selective surface. The loss layer includes a first loss layer and a second loss layer: the first loss layer is mainly composed of a bent metal structure, and the two are connected through metallized vias penetrating the dielectric layer. Furthermore, a cross-shaped resistive carbon paste connects the surrounding metal strips at the center of each unit to achieve wave absorption loss. The second loss layer is composed of a square ring-shaped bent metal structure with loaded lumped resistance. The frequency selective surface adopts a three-layer metal structure design, achieving broadband wave transmission. This invention, while achieving high miniaturization, not only maintains broadband wave transmission and low insertion loss performance, but also forms operating frequency bands with high wave absorption characteristics on both sides of the transmission band. Simultaneously, the electromagnetic characteristics of this invention remain stable when the incident angle is within the range of 0~30°.

Description

Technical Field

[0001] This invention belongs to the field of radar stealth technology, and further relates to a miniaturized broadband penetrating integrated frequency selective surface in the field of electromagnetic field and microwave technology. Background Technology

[0002] Frequency selective radiators (FSRs), which combine transmission and absorption properties, are widely used to reduce the radar cross section (RCS) of antennas in radar and communication systems. With the increasing number of radar and communication systems possessing wideband transmission characteristics, higher demands are being placed on the low insertion loss and wideband transmission performance of FSRs.

[0003] In the current field of broadband frequency selective surface (FSR) design, parallel resonators with large inductors are typically used to improve the structure's high transmittance and wide bandwidth characteristics. However, the 1dB passband bandwidth of such FSRs can only reach about 30%, which is insufficient to meet the actual bandwidth requirements of broadband antenna systems, thus restricting their widespread application in broadband communication and other scenarios.

[0004] In the miniaturization design of frequency selective surface mount systems (FSS), the 2.5-D structure is a commonly used technique in the industry. Yuan et al. first proposed a design scheme for FSRs based on the 2.5-D structure, providing a new design approach for the miniaturization of FSRs and the broadening of transmission bandwidth, thus promoting the technological development in this field. Subsequently, many research teams at home and abroad have carried out design and research work on broadband transmission FSRs based on the 2.5-D structure. For example, in 2021, Zeqian Yang et al. used a design method combining a 2.5-D structure with a bent arrangement to achieve an FSR with -1dB broadband transmission characteristics in the 7.81GHz-11.78GHz frequency band, with a relative bandwidth of 40.53% and a unit size of 0.26. λ C (in λ C (The free-space wavelength corresponding to the center frequency of the transmission band); Jiao Yin et al., in 2024, also based on a 2.5-D structure, achieved a broadband transmission effect of -1.5dB in the 7.15GHz-12.4GHz frequency band through a design of two superimposed loss layers, with a unit size of 0.057. λ L (in λ L (This refers to the free space wavelength corresponding to the lowest frequency in the low-frequency band).

[0005] In summary, the 2.5-D structure can indeed effectively broaden the transmission bandwidth of the FSR and has significant advantages in miniaturization. However, existing FSR research based on the 2.5-D structure still has room for improvement in key performance indicators such as transmission bandwidth broadening and in-band insertion loss control, and cannot simultaneously achieve broadband transmission, low insertion loss and miniaturization characteristics.

[0006] To address the shortcomings of the existing technologies, this patent proposes a broadband transparent FSR design based on a 2.5-D structure. It adopts a composite structure layout of "two loss layers + one frequency selection layer". The two loss layers correspond to the electromagnetic performance control on both sides of the transparent band. Through the synergistic effect of the two loss layers, the structure achieves low insertion loss and wide bandwidth transmission, effectively solving the performance defects of the existing technologies.

[0007] Based on the positional distribution of the passband and absorption band, Frequency Selective Surfaces (FSRs) can be classified into three types: "absorb-transmit," "transmit-absorb," and "absorb-transmit-absorb." Among these, the "absorb-transmit-absorb" type FSR, due to the overlap between the passband and absorption band, is prone to increased passband insertion loss, thus affecting the overall electromagnetic performance of the structure. Its design difficulty is significantly higher than the other two types, but because it can achieve in-band wave transmission and out-of-band bidirectional absorption, it has the widest range of applications. This patent addresses the technical pain point of existing "absorb-transmit-absorb" type FSRs, which struggle to simultaneously achieve the three core characteristics of wideband wave transmission, low in-band insertion loss, and miniaturized structure. It conducts targeted structural innovation design to effectively overcome the aforementioned technical bottlenecks and significantly improve the comprehensive electromagnetic performance and engineering application value of the "absorb-transmit-absorb" type FSR. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention proposes a miniaturized broadband transparent and absorbent integrated frequency selective surface, aiming to achieve low insertion loss and broadband transparency while further improving the miniaturization level of the FSR structure.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A miniaturized broadband wave-transmitting and wave-absorbing integrated frequency selective surface, the surface having a multi-layer cascaded structure, comprising a first structural layer, a second structural layer and a third structural layer from top to bottom; Each set of upper metal patches and each set of lower metal patches includes several metal strips. Part of the metal strips of the four sets of upper metal patches form a Jerusalem cross-shaped structure centered on a cross-shaped resistive carbon paste and are partially covered by the cross-shaped resistive carbon paste. The remaining part forms a split, bent metal strip with the metal strips of the lower metal patches. Each set of upper metal patches and one set of lower metal patches are connected through metallized vias to generate resonance in the mid-frequency and high-frequency bands. This allows the first structural layer to absorb low-frequency electromagnetic waves and allow mid-frequency and high-frequency electromagnetic waves to pass through. The second structural layer includes a bent square ring-shaped metal patch, the four corners of which are connected with lumped resistance for absorbing electromagnetic waves in the high-frequency band; thereby enabling the second structural layer to absorb electromagnetic waves in the high-frequency band while allowing electromagnetic waves in the low-frequency and mid-frequency bands to pass through. The third structural layer includes three frequency-selective surfaces from top to bottom, exhibiting reflection characteristics in both low and high frequency bands and wave transmission characteristics in the mid frequency band.

[0010] In one embodiment, the four sets of upper metal patches are disposed on the upper surface of the first dielectric substrate, and the four sets of lower metal patches are disposed on the lower surface of the first dielectric substrate; a portion of each set of upper metal patches is covered by one arm end of a cross-shaped resistive carbon paste.

[0011] In one embodiment, each group of upper metal patches includes mutually isolated L-shaped metal strips, S-shaped metal strips, and L-T-shaped metal strips; wherein, one arm of the L-shaped metal strip is covered by one arm of cross-shaped resistive carbon paste, and in the L-T-shaped metal strip, one end of the L-shaped portion is connected to the bottom end of the T-shaped portion, and the other end of the L-shaped portion, the other end of the L-shaped metal strip, and both ends of the S-shaped metal strip are provided with first circular metal patches; Each group of lower metal patches includes a first type I metal strip, a second type I metal strip, and a T-type metal strip that are isolated from each other; at both ends of the first type I metal strip and the second type I metal strip, a second circular metal patch is provided; the circular metal patch is connected in sequence to a plurality of metallized vias: an L-type metal strip, a first type I metal strip, an S-type metal strip, a second type I metal strip, and an L-T type metal strip; One arm of the L-shaped metal strip, one arm of the cross-shaped resistive carbon paste, the middle part of the S-shaped metal strip, and the middle branch of the T-shaped part of the L-T-shaped metal strip are coaxially distributed and perpendicular to the first I-shaped metal strip and the second I-shaped metal strip. The T-shaped portion of the L-T type metal strip is opposite to the projection of the T-shaped metal strip.

[0012] In one embodiment, the cross-shaped resistive carbon paste is a resistive carbon paste resistive film loaded at the center of the unit. Its shape is composed of five squares with a side length of W6=1mm, and its surface resistance is 250 Ω / sq.

[0013] In one embodiment, the cross-shaped resistive carbon paste covers a length of 1 mm of the bent metal strip.

[0014] In one embodiment, the bent square ring-shaped metal patch and four lumped resistors are located on the upper surface of the second dielectric substrate. Each side of the bent square ring-shaped metal patch has a symmetrical bending structure. The four lumped resistors have the same resistance value and are respectively located at the four corners of the bent square ring-shaped metal patch, with a resistance value of 100 Ohm.

[0015] In one embodiment, each side of the bent square ring-shaped metal patch is parallel or perpendicular to the four sides of the second dielectric substrate, and resonates in the high-frequency band.

[0016] In one embodiment, the third structural layer includes a third dielectric substrate and a fourth dielectric substrate; the three frequency selection surfaces from top to bottom are, in sequence, a first frequency selection surface, a second frequency selection surface, and a third frequency selection surface; the first frequency selection surface is disposed on the upper surface of the third dielectric substrate, and the second and third frequency selection surfaces are respectively located on the upper and lower surfaces of the fourth dielectric substrate; the first and third frequency selection surfaces are identical annular metal patches, and the second frequency selection surface is a bent square annular metal patch.

[0017] In one embodiment, an air gap h is provided between the first structural layer and the second structural layer, and between the second structural layer and the third structural layer. air1 and h air2 Furthermore, it is positioned and fixed by insulating support columns. The thicknesses of the air gaps are 4.2 mm and 6.3 mm, respectively. The unit period of both the upper and lower metal patches is D=8mm. By adopting a split-design bent metal strip, the unit size is reduced to 0.049. λ L , λ L The wavelength corresponding to the lowest frequency of the absorption band; the low frequency band is 1.8-4.0 GHz, the mid frequency band is 5.9-13 GHz, and the high frequency band is 15.2-18.0 GHz.

[0018] In one embodiment, the first structural layer has a first dielectric plate, the second structural layer has a second dielectric plate, and the third structural layer has a third dielectric plate and a fourth dielectric plate. All dielectric plates are made of F4BTMS220 with a relative permittivity of 2.2. The thickness of the first dielectric plate is h1 = 0.508 mm, the thickness of the second dielectric plate is h2 = 0.254 mm, and the thicknesses of the third and fourth dielectric plates are both h3 = 2.1 mm. The insulating support column is made of nylon, has a diameter of 7 mm, and its height is consistent with the corresponding air gap thickness.

[0019] Compared with the prior art, the present invention has the following advantages: 1. The miniaturized broadband transmittance integrated frequency selective surface of this invention is based on a 2.5-D structural design (the technology of printing metallized through-holes on a two-dimensional planar support dielectric substrate). Through the metallized through-holes and their compact arrangement, while ensuring synergistic optimization of broadband transmission and dual-band absorption performance, a highly miniaturized structure is achieved. This results in the core characteristic of integrated transmittance and absorption, possessing partial absorption in the S-band and Ku-band, and partial transmission in the C-band and X-band. The unit period of this frequency selective surface is only 0.049. λ L The unit section height is only 0.095. λ L Compared to traditional frequency selective surfaces, this device offers significant advantages in miniaturization, making it easier for practical engineering applications and integrated installation. In terms of wave transmission performance, this frequency selective surface achieves stable and excellent wave transmission characteristics within the 5.92GHz to 12.88GHz frequency band covered by parts of the C-band and X-band. The relative bandwidth of this transmission band reaches 74%, and the in-band insertion loss is strictly controlled below 1dB. It possesses technical advantages such as low insertion loss, wide bandwidth, and strong wave transmission stability, fully meeting the wave transmission requirements of broadband communication scenarios.

[0020] 2. The miniaturized broadband transmittance integrated frequency selective surface described in this invention possesses stable absorption performance on both sides of the aforementioned broadband transmittance band, effectively absorbing interfering electromagnetic waves outside the transmittance band. Specifically, in the frequency bands of 1.84GHz to 3.97GHz corresponding to a portion of the L-band and a portion of the S-band, and in the frequency bands of 15.03GHz to 18.11GHz corresponding to a portion of the Ku-band, the absorption rate of this frequency selective surface is not less than 80%; furthermore, in the high-frequency band of 15.30GHz to 17.88GHz, its absorption rate can reach over 90%, exhibiting even better absorption performance and significantly improving overall electromagnetic compatibility. Attached Figure Description

[0021] Figure 1 This is a side view of the overall structure of the present invention.

[0022] Figure 2 This is a top view of the first structural layer of the miniaturized broadband frequency selective wave-absorbing and wave-transmitting integrated surface of the present invention.

[0023] Figure 3 This is a top view of the miniaturized broadband frequency selective wave-absorbing and wave-transmitting integrated surface upper metal patch of the present invention.

[0024] Figure 4 This is a bottom view of the first structural layer of the miniaturized broadband frequency selective wave-absorbing and wave-transmitting integrated surface of the present invention.

[0025] Figure 5 This is a bottom view of the miniaturized broadband frequency selective wave-absorbing and wave-transmitting integrated surface metal patch of the present invention.

[0026] Figure 6 This is a top view of the miniaturized broadband frequency selective wave-absorbing and wave-transmitting integrated surface second structural layer of the present invention.

[0027] Figure 7 This is a top view of the miniaturized broadband frequency selective wave-absorbing and wave-transmitting integrated surface third structure layer of the present invention.

[0028] Figure 8 The simulation results of the basic unit S-parameters and absorption rate of the miniaturized broadband frequency selective wave-absorbing and wave-transmitting integrated surface of the present invention are as follows.

[0029] Figure 9 The figure shows the S-parameter simulation results of the basic unit of the miniaturized broadband frequency selective wave-absorbing and wave-transmitting integrated surface of the present invention when incident at a certain angle.

[0030] Figure 10 This is a simulation result of the absorption rate of the basic unit of the miniaturized broadband frequency selective wave-absorbing and wave-transmitting integrated surface of the present invention when incident at a certain angle. Detailed Implementation

[0031] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0032] Reference Figure 1 In this embodiment, the surface has a multi-layer cascaded structure, which includes a first structural layer 1, a second structural layer 2, and a third structural layer 3 from top to bottom. The first structural layer 1 has a first dielectric substrate 8, the second structural layer 2 has a second dielectric substrate 11, and the third structural layer 3 has a third dielectric substrate 13 and a fourth dielectric substrate 15. The first dielectric substrate 8, the second dielectric substrate 11, the third dielectric substrate 13, and the fourth dielectric substrate 15 are arranged from top to bottom.

[0033] In terms of functional structure, the first structural layer 1 includes an upper metal patch 4, a lower metal patch 5, a cross-shaped resistive carbon paste 6, and metallized vias 7. The upper metal patch 4 and the lower metal patch 5 are located on the upper and lower surfaces of the first dielectric substrate 8, respectively, and are improved from the Jerusalem cross-shaped structure. Performance optimization is achieved by introducing bent metal strips and cross-shaped resistive carbon paste 6 into its structure. Thus, there are four sets of upper metal patches 4 and four sets of lower metal patches 5, and multiple metallized vias 7. Each set of upper metal patches 4 or each set of lower metal patches 5 has a bent metal strip. The bent metal strip is split, and a circular metal patch is added to the edge of the split metal strip. Finally, the split parts of the metal strip are folded back and connected through the metallized vias 7. The bent metal strip is partially covered by a cross-shaped resistive carbon paste 6. Since the cross-shaped resistive carbon paste 6 can absorb low-frequency electromagnetic waves, the first structural layer 1 of the present invention can absorb low-frequency electromagnetic waves while allowing mid-frequency and high-frequency electromagnetic waves to pass through.

[0034] The second structural layer 2 includes a bent square ring-shaped metal patch 9 and four lumped resistors 10, all arranged on the upper surface of the second dielectric substrate 11. The lumped resistors 10 are connected to the bent square ring-shaped metal patch 9. Because they can absorb electromagnetic waves in the high-frequency band, the second structural layer 2 of the present invention can absorb electromagnetic waves in the high-frequency band while allowing electromagnetic waves in the low-frequency and mid-frequency bands to pass through.

[0035] The third structural layer 3 includes a first frequency selective surface 12, a second frequency selective surface 14, and a third frequency selective surface 16. The first frequency selective surface 12 is disposed on the upper surface of the third dielectric substrate 13, and the second frequency selective surface 14 and the third frequency selective surface 16 are located on the upper and lower surfaces of the fourth dielectric substrate 15, respectively. Through the three frequency selective surfaces distributed in sequence, the third structural layer 3 of the present invention exhibits reflection characteristics in both the low-frequency and high-frequency bands, and transmittance characteristics in the mid-frequency band.

[0036] In this invention, the low-frequency band is 1.8-4.0 GHz, the mid-frequency band is 5.9-13 GHz, and the high-frequency band is 15.2-18.0 GHz.

[0037] Based on the above structure, this invention achieves a composite design of two loss layers and one frequency-selective layer. The first loss layer is mainly composed of a bent metal structure, and the two are connected through metallized vias penetrating the dielectric layer. Furthermore, a cross-shaped resistive carbon paste connects the surrounding metal strips at the center of the unit to achieve absorption loss. The second loss layer is composed of a square ring-shaped bent metal structure with loaded lumped resistance. The two loss layers correspond to the electromagnetic performance regulation on both sides of the transmission band, and their synergistic effect ultimately achieves low insertion loss and wide bandwidth transmission. Simultaneously, within the absorption frequency band of one loss layer, the other loss layer exhibits good transmission characteristics. The two loss layers form independent absorption bands in the low-frequency and high-frequency bands, respectively, thus achieving a three-stage electromagnetic response of "absorption-transmission-absorption." The frequency-selective layer adopts a three-layer metal structure design, realizing broadband transmission functionality.

[0038] Furthermore, since this invention separates the low-frequency absorption and high-frequency absorption functions into two loss layers, it offers dual technical advantages: First, realizing the low-frequency absorption function requires a larger resonant structure; separate design effectively ensures the rationality of the internal unit layout of the loss layer with low-frequency absorption function, avoiding structural interference. Second, the loss layer with high-frequency absorption function can focus on optimizing the absorption effect; its low-frequency transmission band is precisely determined by the high-frequency absorption frequency, eliminating the need for additional structural constraints on low-frequency transmission, thus improving the design accuracy and stability of high-frequency absorption performance.

[0039] Specifically, in an embodiment of the present invention, an air gap h is provided between the first structural layer 1 and the second structural layer 2. air1 =4.2 mm, and an air gap h is provided between the second structural layer 2 and the third structural layer 3. air2 =6.3 mm, with adjacent structural layers positioned and fixed by insulating support columns. The unit period of both the upper metal patch 4 and the lower metal patch 5 is D=8mm. By employing a split-design bent metal strip, the unit size can be reduced to 0.049. λ L The unit section height is only 0.095. λ L , λ L This is the wavelength corresponding to the lowest frequency in the absorption band.

[0040] Among them, the lowest frequency of the absorption band f L =1.84GHz, corresponding wavelength λ L ≈163.04mm, element size D=8mm, element section height is h = 15.458mm, therefore the unit size is the same as λ LThe ratio is 8mm / 163.04mm≈0.049, and the unit section height is... λ L The ratio is 15.458mm / 163.04mm≈0.095.

[0041] This invention further provides a specific design for the upper metal patch 4, see reference. Figure 2 and Figure 3 The upper metal patch 4 includes an L-shaped metal strip 41, an S-shaped metal strip 42, a first circular metal patch 43, and an L-T-shaped metal strip 44. A portion of one arm of the L-shaped metal strip 41 is covered by one arm of the cross-shaped resistive carbon paste 6, and this arm is preferably coaxially arranged with the arm covered by the cross-shaped resistive carbon paste 6. On the upper surface of the first dielectric substrate 8, the metal strips of the upper metal patch 4 are isolated from each other. The S-shaped metal strip 42 is bent at a right angle, with its middle portion coaxially arranged with the aforementioned "one arm of the L-shaped metal strip 41" and having a spacing. The L-T-shaped metal strip 44 is composed of an L-shaped portion and a T-shaped portion connected together. The T-shaped portion consists of a first strip and a second strip. The first strip is parallel to one side of the first dielectric substrate 8, and the second strip is located inside the first strip. One end of the second strip is perpendicularly connected to the middle of the first strip, and the other end is perpendicularly connected to the first arm of the L-shaped portion. The second arm of the L-shaped portion extends inward towards the first dielectric substrate 8. The second strip is preferably arranged coaxially with one arm of the aforementioned "L-shaped metal strip 41" and has a gap with the middle portion of the S-shaped metal strip 42. This forms a layout in which the cross-shaped resistive carbon paste 6, L-shaped metal strip 41, S-shaped metal strip 42, and L-T-shaped metal strip 44 are distributed from the inside out. To achieve vertical folding connections, first circular metal patches 43 are distributed at the end of the other arm of the L-shaped metal strip 41, both ends of the S-shaped metal strip 42, and the end of the second arm of the L-shaped portion of the L-T-shaped metal strip 44.

[0042] This invention further provides a specific design for the lower metal patch 5, see reference. Figure 4 and Figure 5The lower metal patch 5 includes a first I-shaped metal strip 51, a second I-shaped metal strip 52, a second circular metal patch 53, and a T-shaped metal strip 54. On the lower surface of the first dielectric substrate 8, the metal strips of the lower metal patch 5 are isolated from each other. The T-shaped metal strip 54 consists of a first strip and a second strip. The first strip is parallel to one side of the first dielectric substrate 8, and the second strip is located inside the first strip, with one end perpendicularly connected to the middle of the first strip and the other end spaced apart from the second I-shaped metal strip 52. Here, the first I-shaped metal strip 51 and the second I-shaped metal strip 52 are parallel and perpendicular to the aforementioned "one arm of the L-shaped metal strip 41". The T-shaped metal strip 54 is approximately projected opposite to the T-shaped portion of the L-T-shaped metal strip 44. To achieve a vertical fold-back connection, second circular metal patches 53 are distributed at both ends of the first I-shaped metal strip 51 and at both ends of the second I-shaped metal strip 52.

[0043] Thus, through the first circular metal patch 43, the second circular metal patch 53, and the metallized via 7, the following are sequentially connected: L-shaped metal strip 41, first I-shaped metal strip 51, S-shaped metal strip 42, second I-shaped metal strip 52, and L-T-shaped metal strip 44. The overall structure can be divided into a Jerusalem cross-shaped structure (including the shorter part of the L-shaped metal strip 41 and the T-shaped metal strip part of the L-T-shaped metal strip 44), split bent metal strips (including the longer part of the L-shaped metal strip 41, the first I-shaped metal strip 51, the S-shaped metal strip 42, the second I-shaped metal strip 52, and the L-shaped metal strip part of the L-T-shaped metal strip 44), and a center resistive carbon paste 6. The T-shaped metal strip 54 is completely isolated and mainly serves to increase the equivalent capacitance between units.

[0044] The split, bent metal strips resonate in parallel LC circuits at mid-to-high frequencies. Therefore, the first structural layer 1 exhibits wave transmission characteristics at mid-to-high frequencies. Simultaneously, the central resistive carbon paste forms the R in the series RLC circuit. The split, bent metal strips, the Jerusalem cross-shaped structure, and the T-shaped metal strip 54 constitute the series LC portion of the series RLC circuit. The inductive effect of the metal strips corresponds to the series inductance L, and the equivalent capacitance between units corresponds to the capacitance C. This RLC circuit resonates at low frequencies, exhibiting wave absorption characteristics.

[0045] The cross-shaped resistive carbon paste 6 is a resistive carbon paste resistive film, loaded at the center of the unit. Its shape is composed of five squares with a side length of W6 = 1 mm, and its surface resistivity is 250 Ω / sq. It is used to absorb low-frequency electromagnetic waves. To connect the metal strip and utilize the loss function of the resistive carbon paste (the resistive part in the series RLC circuit), the length of the cross-shaped resistive carbon paste 6 covering the metal strip must be at least W6 = 1 mm.

[0046] exist Figure 2 and Figure 4 In the structure shown, the width of the long side (the covered side) of the L-shaped metal strip 41 is W1=0.3mm, the width of the short side is W2=0.15mm, the width of the S-shaped metal strip 42 is W2=0.15mm, and the overall length is L1=3.5mm. The width of the short side (the second strip) of the T-shaped portion of the L-T-shaped metal strip 44 is W3=0.3mm, the length is L3=0.3mm, and the width of the long side (the first strip) of the T-shaped portion is W4=0.15mm, the length is L2=3mm. The lengths of the first I-shaped metal strip 51 and the second I-shaped metal strip 52 are both L2=3mm. The diameters of the first circular metal patch 43 and the second circular metal patch 53 are both D. r =0.4mm.

[0047] This invention further provides a specific design for a bent square ring-shaped metal patch 9, see reference. Figure 6 The bent square ring-shaped metal patch 9 is located at the center of the upper surface of the second dielectric substrate 11. The four lumped resistors 10 have equal resistance values ​​and are connected to the four corners of the bent square ring-shaped metal patch 9, which allows electromagnetic waves in the low and mid frequency bands to pass through. The bent square ring-shaped metal patch 9 and the lumped resistors 10 work together to absorb waves in the high frequency band. The overall side length of the bent square ring-shaped metal patch 9 is L4=2.9mm, and the strip width is W9=0.1mm. The middle part of each side is provided with a bent part, which is preferably symmetrically distributed. In this embodiment, each side is provided with 3 inward bends, one in the middle and two on both sides, and they are symmetrical about the middle one. The length of the bent part on both sides is L5=0.8mm, and the length of the bent part in the middle is L6=1.2mm. The dimensions of the lumped resistors 10 are designed as L7=0.6mm and W7=0.3mm, and their resistance is 100 Ohm, which is used to absorb electromagnetic waves in the high frequency band. Each side of the bent square ring-shaped metal patch 9 is parallel or perpendicular to the four sides of the second dielectric plate 11, and resonates in the high-frequency band.

[0048] The bent square ring-shaped metal patch 9 corresponds to the LC part of the series RLC circuit. The bending at 3 points on each side of the square ring increases the electrical length of the metal strip, which is used to increase the corresponding equivalent inductance L. The equivalent capacitance C is generated by the coupling between units. The four lumped resistors 10 correspond to the R part of the series RLC circuit. The lumped resistors 10 and the bent square ring-shaped metal patch 9 constitute the series RLC circuit, which is an absorbing frequency point at high frequency resonance.

[0049] This invention further provides a specific design for the three frequency-selective surfaces of the third structural layer 3, see reference. Figure 7 The first frequency selection surface 12 and the third frequency selection surface 16 are identical annular metal patches, while the second frequency selection surface 14 is a bent square annular metal patch. The diameter of the annular metal patch is D. R=5mm, the ring width S=0.1mm, and the bending lengths of the bent square ring metal patch are P=2.15mm and Q=0.9mm respectively.

[0050] The annular metal patches on the first frequency selection surface 12 and the third frequency selection surface 16 each form a series LC circuit, where L is equivalent to the annular metal strip, and C is equivalent to the inter-cell capacitive coupling and the internal coupling of the annulus. The bent square annular metal patch on the second frequency selection surface 14 is equivalent to an inductor; the bent portion increases the electrical length of the metal strip to increase the equivalent inductance. The three metal patches work together to generate a passband at the mid-frequency range.

[0051] In a further embodiment of the present invention, the first dielectric substrate 8, the second dielectric substrate 11, the third dielectric substrate 13, and the fourth dielectric substrate 15 are all made of F4BTMS220 with a relative permittivity of 2.2; wherein the thickness of the first dielectric substrate 8 is h1=0.508mm, the thickness of the second dielectric substrate 11 is h2=0.254mm, and the thickness of the third dielectric substrate 13 and the fourth dielectric substrate 15 is h3=2.1mm. Metallic material is printed on the dielectric substrates, introducing characteristic impedance.

[0052] The upper metal patch 4, the lower metal patch 5, the bent square ring-shaped metal patch 9, and each frequency selection surface are all made of copper and are used to propagate electromagnetic waves.

[0053] The insulating support column is made of nylon, has a diameter of 7 mm, and its height is consistent with the thickness of the corresponding air gap. It is used to support each layer of dielectric plates and construct air gaps.

[0054] Figure 8 This is a curve showing the S-parameters and absorption rate characteristics of the miniaturized broadband integrated frequency selective surface of this invention. The horizontal axis of the curve represents frequency, the left vertical axis corresponds to the S-parameters, and the right vertical axis corresponds to the absorption rate. The square-marked curve represents the transmission coefficient |S... 21 |The curve, marked with a circle, represents the reflection coefficient|S 11 The curve, marked with an equilateral triangle, represents the absorption rate curve. The curve characteristics show that the transmission frequency range for this integrated absorber / transmitter with a surface insertion loss ≤1dB is 5.92GHz to 12.88GHz. This transmission frequency range has an absolute bandwidth of 6.96GHz and a relative bandwidth of 74%. Simultaneously, two high absorption frequency bands are formed on either side of this transmission frequency range, namely 1.84GHz to 3.97GHz and 15.03GHz to 18.11GHz, with absorption rates of no less than 80% in both bands.

[0055] Figure 9 and Figure 10This is a graph showing the S-parameters and absorbance curves of a miniaturized broadband integrated frequency selective surface (FSR) under incident angles of 0–40°. It can be seen that at an incident angle of 30°, the 1.5dB transmission bandwidth of this FSR is 5.84 GHz to 13.47 GHz, but at an incident angle of 40°, the in-band insertion loss increases. Within 30°, this invention can maintain more than 80% of the absorption bandwidth; when the incident angle is 40°, the absorption bandwidth begins to decrease. This indicates that this invention can exhibit good angular stability within an incident angle of 30° and a highly stable operating center frequency band.

[0056] The simulation results above demonstrate that the integrated absorption and penetration frequency selective surface of this embodiment achieves effective absorption across a wide frequency band, both low and high, while transmitting electromagnetic waves with low insertion loss in the mid-frequency band. Due to the structural symmetry, this frequency selective surface exhibits the same transmission and absorption effects under both TE and TM polarization. Furthermore, by employing metallized vias and densely arranged metal strips, the unit size of this frequency selective surface is reduced to 0.049. λ L The profile height is 0.095. λ L .

[0057] This invention, by setting two loss layers, can synergistically optimize the electromagnetic performance of the transmission band while achieving absorption functions in different frequency bands. At the same time, a bandpass frequency selective surface structure with mid-frequency bandpass, low-frequency and high-frequency reflection window characteristics is specially designed. Moreover, both loss layers and frequency selective layers adopt miniaturized design schemes, which together ensure the core advantages of miniaturization and wide bandwidth of this invention.

[0058] This invention achieves high miniaturization while maintaining broadband transmission and low insertion loss performance, and also creates operating frequency bands with high absorption characteristics on both sides of the transmission band. Furthermore, the electromagnetic characteristics of this invention remain stable when the incident angle is within the range of 0~30°.

[0059] It should be noted that the above are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. For those skilled in the art, this application can have various adjustments and variations. Any modifications, equivalent substitutions, improvements, and optimizations made within the spirit and core principles of this application should be included within the scope of protection defined by the claims of this application.

Claims

1. A miniaturized broadband wave-transmitting and wave-absorbing integrated frequency selective surface, characterized in that, The surface has a multi-layer cascaded structure, which includes a first structural layer (1), a second structural layer (2) and a third structural layer (3) from top to bottom; The first structural layer (1) includes a cross-shaped resistive carbon paste (6), four sets of upper metal patches (4), four sets of lower metal patches (5), and multiple metallized vias (7). The cross-shaped resistive carbon paste (6) is used to absorb electromagnetic waves in the low-frequency band. Each set of upper metal patches (4) and each set of lower metal patches (5) includes several metal strips. Some of the metal strips of the four sets of upper metal patches (4) form a Jerusalem cross-shaped structure centered on a cross-shaped resistive carbon paste (6) and are partially covered by the cross-shaped resistive carbon paste (6). The remaining part forms a split, bent metal strip with the metal strips of the lower metal patches (5). Each set of upper metal patches (4) and a set of lower metal patches (5) are connected through a metallized via (7) to generate resonance in the mid-frequency and high-frequency bands. This enables the first structural layer (1) to absorb electromagnetic waves in the low-frequency band and allow electromagnetic waves in the mid-frequency and high-frequency bands to pass through. The second structural layer (2) includes a bent square ring-shaped metal patch (9), the four corners of which are connected by a lumped resistance (10) for absorbing electromagnetic waves in the high frequency band; thereby enabling the second structural layer (2) to absorb electromagnetic waves in the high frequency band and allow electromagnetic waves in the low frequency band and mid frequency band to pass through. The third structural layer (3) includes three frequency-selective surfaces from top to bottom, exhibiting reflection characteristics in both low and high frequency bands and wave transmission characteristics in the mid frequency band.

2. The miniaturized broadband transmittance and absorbance integrated frequency selective surface according to claim 1, characterized in that, The four sets of upper metal patches (4) are disposed on the upper surface of the first dielectric plate (8), and the four sets of lower metal patches (5) are disposed on the lower surface of the first dielectric plate (8); a portion of each set of upper metal patches (4) is covered by one arm end of a cross-shaped resistive carbon paste (6).

3. The miniaturized broadband transmittance and absorbance integrated frequency selective surface according to claim 2, characterized in that, Each set of upper metal patches (4) includes mutually isolated L-shaped metal strips (41), S-shaped metal strips (42) and L-T-shaped metal strips (44); wherein, one arm of the L-shaped metal strip (41) is covered by one arm of the cross-shaped resistive carbon paste (6), and in the L-T-shaped metal strip (44), one end of the L-shaped part is connected to the bottom end of the T-shaped part, and the other end of the L-shaped part, the other end of the L-shaped metal strip (41) and both ends of the S-shaped metal strip (42) are provided with first circular metal patches (43); Each set of lower metal patches (5) includes a first type I metal strip (51), a second type I metal strip (52), and a T-type metal strip (54) that are isolated from each other; at both ends of the first type I metal strip (51) and the second type I metal strip (52), a second circular metal patch (53) is provided; the circular metal patch is connected to multiple metallized vias (7) in sequence: L-type metal strip (41), first type I metal strip (51), S-type metal strip (42), second type I metal strip (52), and L-T type metal strip (44); One arm of the L-shaped metal strip (41) is coaxially distributed with one arm of the cross-shaped resistive carbon paste (6), the middle part of the S-shaped metal strip (42), and the middle branch of the T-shaped part of the L-T-shaped metal strip (44), and is perpendicular to the first I-shaped metal strip (51) and the second I-shaped metal strip (52). The T-shaped portion of the L-T type metal strip (44) is opposite to the projection of the T-type metal strip (54).

4. The miniaturized broadband transmittance and absorbance integrated frequency selective surface according to claim 1, 2, or 3, characterized in that, The cross-shaped resistive carbon paste (6) is a resistive carbon paste resistive film, loaded at the center of the unit. Its shape is composed of five squares with a side length of W6=1mm, and its surface resistance is 250 Ω / sq.

5. The miniaturized broadband transmittance and absorbance integrated frequency selective surface according to claim 4, characterized in that, The length of the metal strip covered by the cross-shaped resistive carbon paste (6) on the upper metal patch (4) is 1 mm.

6. The miniaturized broadband transmittance and absorbance integrated frequency selective surface according to claim 1, 2, or 3, characterized in that, The bent square ring-shaped metal patch (9) and four lumped resistors (10) are located on the upper surface of the second dielectric plate (11). Each side of the bent square ring-shaped metal patch (9) has a symmetrical bending structure. The four lumped resistors (10) have the same resistance value and are respectively located at the four corners of the bent square ring-shaped metal patch (9), with a resistance value of 100 Ohm.

7. The miniaturized broadband transmittance and absorbance integrated frequency selective surface according to claim 6, characterized in that, Each side of the bent square ring-shaped metal patch (9) is parallel or perpendicular to the four sides of the second dielectric plate (11), and resonates in the high frequency band.

8. The miniaturized broadband transmittance and absorbance integrated frequency selective surface according to claim 1, 2, or 3, characterized in that, The third structural layer (3) includes a third dielectric plate (13) and a fourth dielectric plate (15); the three frequency selection surfaces from top to bottom are a first frequency selection surface (12), a second frequency selection surface (14) and a third frequency selection surface (16); the first frequency selection surface (12) is located on the upper surface of the third dielectric plate (13), and the second frequency selection surface (14) and the third frequency selection surface (16) are located on the upper and lower surfaces of the fourth dielectric plate (15), respectively; the first frequency selection surface (12) and the third frequency selection surface (16) are the same annular metal patch, and the second frequency selection surface (14) is a bent square annular metal patch.

9. The miniaturized broadband transmittance and absorbance integrated frequency selective surface according to claim 1, 2, or 3, characterized in that, An air gap h is provided between the first structural layer (1) and the second structural layer (2), and between the second structural layer (2) and the third structural layer (3). air1 and h air2 And it is positioned and fixed by insulating support columns. The thickness of the air gap is 4.2 mm and 6.3 mm respectively. The unit period of the upper metal patch (4) and the lower metal patch (5) is D=8 mm. By adopting a split design of bent metal strips, the unit size is reduced to 0.

049. λ L , λ L The wavelength corresponding to the lowest frequency of the absorption band; the low frequency band is 1.8-4.0 GHz, the mid frequency band is 5.9-13 GHz, and the high frequency band is 15.2-18.0 GHz.

10. The miniaturized broadband transmittance and absorbance integrated frequency selective surface according to claim 9, characterized in that, The first structural layer (1) has a first dielectric plate (8), the second structural layer (2) has a second dielectric plate (11), the third structural layer (3) has a third dielectric plate (13) and a fourth dielectric plate (15), and the material of each dielectric plate (8) is F4BTMS220 with a relative permittivity of 2.2; wherein, the thickness of the first dielectric plate (8) is h1=0.508mm, the thickness of the second dielectric plate (11) is h2=0.254mm, and the thickness of the third dielectric plate (13) and the fourth dielectric plate (15) is h3=2.1mm; the insulating support column is made of nylon, has a diameter of 7mm, and its height is consistent with the thickness of the corresponding air gap.

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