A bandpass dual-polarized frequency selective surface

Abstract

The application discloses a band-pass dual-polarized frequency selective surface. The application adopts a composite structure of three layers of metal patches and two layers of dielectric substrates stacked alternately, and can realize high-performance frequency selection function. The frequency selective surface has a passband frequency range of 7-13 GHz, a stopband covering 0.1-6 GHz and 14-18 GHz frequency bands, and transition bands of 6-7 GHz and 13-14 GHz respectively. In the passband range, the average power transmission efficiency is greater than 0.85, and in the stopband range, the average insertion loss is lower than -13 dB. The frequency selective surface designed by the application has good dual-polarized working characteristics, can support TE polarization and TM polarization incidence at the same time, and shows stable frequency response in a wide range of incidence angles. The application has simple structure, superior performance, and is suitable for wireless communication, radar system and electromagnetic shielding fields, and has high engineering application value.

Description

Technical Field

[0001] This invention relates to a frequency selective surface, and more specifically to a bandpass dual-polarized frequency selective surface. Background Technology

[0002] A frequency selective surface is a spatial filter composed of periodically arranged metal patches or aperture elements, capable of exhibiting specific frequency response characteristics to incident electromagnetic waves, such as bandpass or bandstop. Due to its excellent frequency selectivity, it is widely used in radomes, electromagnetic shielding, satellite communications, and radar cross-section reduction.

[0003] As wireless communication and radar systems develop towards ultra-wideband, multi-band, and high reliability, higher requirements are placed on the performance of frequency selective surfaces. In particular, the demand for bandpass frequency selective surfaces with ultra-wideband passband, high selectivity, and good angle and polarization stability is becoming increasingly urgent. Summary of the Invention

[0004] To address the technical challenge of balancing bandwidth, selectivity, angular stability, and structural complexity in achieving ultra-wideband performance with existing bandpass frequency selective surfaces, this invention provides a bandpass dual-polarized frequency selective surface. Through a three-layer patch-two-layer dielectric composite structure design, this invention achieves an ultra-wideband high-transmission passband of 7-13 GHz within a relatively compact physical size, effectively suppressing signal interference in both stopbands (0.1 GHz-6 GHz and 14 GHz-18 GHz), and ensuring good dual-polarization operational stability over a wide incident angle range, thus meeting the high-performance requirements of modern wireless communication and radar systems.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] I. A bandpass-type dual-polarization frequency selective surface

[0007] The frequency selective surface comprises, from top to bottom, a first metal patch layer, a first dielectric substrate, a second metal patch layer, a second dielectric substrate, and a third metal patch layer. Each of the first, second, and third metal patch layers contains corresponding metal patch units, and these units exhibit fourfold rotational symmetry. Each metal patch unit is completely flat on the dielectric substrate. Each metal patch layer contains several metal patch units arranged in a periodic array. The centers of the metal patch units in a group of the first, second, and third metal patch layers are located on a straight line, meaning that the rotational symmetry axis of each metal patch unit in the first metal patch layer is coaxial with the rotational symmetry axes of the corresponding metal patch units in the second and third metal patch layers. The metal patch units corresponding to the first and third metal patch layers have the same geometry but different sizes, while the geometry of the metal patch units corresponding to the second metal patch layer is different from that of the metal patch units in the first metal patch layer.

[0008] The geometry of the metal patch unit corresponding to the first metal patch layer includes square.

[0009] The geometry of the metal patch unit corresponding to the second metal patch layer includes a cross shape, a variant of the cross shape, and a Jerusalem cross shape.

[0010] The first dielectric substrate and the second dielectric substrate have different dielectric constants and thicknesses.

[0011] The dielectric constant of the first dielectric substrate is greater than that of the second dielectric substrate, and the thickness of the first dielectric substrate is less than that of the second dielectric substrate.

[0012] The passband frequency range of the frequency selective surface is 7 GHz to 13 GHz; the average power transfer efficiency of the frequency selective surface within the passband frequency range is greater than 0.85.

[0013] The frequency selective surface has stopbands including a first stopband and a second stopband, the first stopband ranging from 0.1 GHz to 6 GHz and the second stopband ranging from 14 GHz to 18 GHz; the average insertion loss of the frequency selective surface in the two stopbands is less than -13 dB.

[0014] Within the incident angle range of 0° to 60°, the frequency selective surface maintains the aforementioned passband and stopband characteristics for both TE-polarized and TM-polarized incident electromagnetic waves.

[0015] The frequency selective surface has a transition band that includes a first transition band and a second transition band; the first transition band ranges from 6 GHz to 7 GHz, and the second transition band ranges from 13 GHz to 14 GHz.

[0016] II. A type of antenna radome

[0017] The radome includes a bandpass-type dual-polarized frequency selective surface.

[0018] III. A communication device

[0019] The communication device includes either the bandpass dual-polarized frequency selective surface or the radome.

[0020] IV. A radar system

[0021] The radar system includes either the aforementioned bandpass dual-polarized frequency selective surface or the aforementioned radome.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention achieves an excellent balance between structural complexity, physical thickness, and electrical performance through asymmetric multilayer structure parameter design, providing a high-performance, easy-to-engineer ultrawideband bandpass frequency selective surface. Attached Figure Description

[0024] Figure 1 This is an exploded view of the structure of the frequency-selective surface of the present invention.

[0025] Figure 2 This is a schematic diagram of the frequency-selective surface layered structure of the present invention.

[0026] Figure 3 The power transmission efficiency of the frequency selective surface of the present invention under TE polarization at different incident angles (0° to 60°) within the operating bandwidth (0.1 GHz to 18 GHz).

[0027] Figure 4 The transmission coefficient of the frequency-selective surface of the present invention under TE polarization at different incident angles (0° to 60°) within the operating bandwidth (0.1 GHz to 18 GHz).

[0028] Figure 5 The power transmission efficiency of the frequency selective surface of the present invention under different incident angles (0° to 60°) with TM polarization within the operating bandwidth (0.1 GHz to 18 GHz).

[0029] Figure 6 The transmission coefficient of the frequency-selective surface of the present invention under TM polarization at different incident angles (0° to 60°) within the operating bandwidth (0.1 GHz to 18 GHz). Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the preferred embodiments and simulation results. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. All other improvements and applications obtained by those skilled in the art based on this invention without inventive effort are within the scope of protection of this invention.

[0031] An exploded view of the structure of a bandpass dual-polarization frequency selective surface provided in this embodiment of the invention is shown below. Figure 1 As shown, its layered structure decomposition diagram is as follows: Figure 2 As shown. The frequency selection surface includes a first metal patch layer, a first dielectric substrate, a second metal patch layer, a second dielectric substrate, and a third metal patch layer stacked sequentially from top to bottom; each of the first, second, and third metal patch layers contains a corresponding metal patch unit, and the metal patch units of the first, second, and third metal patch layers are all fourfold rotationally symmetrical structures, with each metal patch unit completely laid flat on the dielectric substrate.

[0032] Figure 1 The basic structural units are infinitely extended along the X and Y axes in a two-dimensional plane with a fixed period P to form a complete periodic frequency-selective surface. The overall structure has a period of 7 mm.

[0033] The centers of the metal patch units in a set of first, second, and third metal patch layers are located on a straight line, meaning that the rotational symmetry axis of each metal patch unit in the first metal patch layer is coaxial with the rotational symmetry axes of the corresponding metal patch units in the second and third metal patch layers. The metal patch units corresponding to the first and third metal patch layers have the same geometry but different dimensions, while the geometry of the metal patch units corresponding to the second metal patch layer is different from that of the metal patch units in the first metal patch layer.

[0034] The geometry of the metal patch units corresponding to the first metal patch layer includes square shapes with a side length of 5.35 mm. The first metal patch layer is composed of a highly conductive metal material (such as copper, silver, or aluminum), and its thickness is much smaller than the operating wavelength, typically 0.035 mm (i.e., 1 ounce of copper foil). Square metal patch units are periodically formed on this layer using processes such as photolithography and etching. This patch layer primarily contributes to the resonance near the low-frequency edge of the passband, and its size is a key parameter for controlling the low-frequency cutoff characteristics.

[0035] The third metal patch layer is the bottom metal layer, and its material is the same as the upper metal layer. Square metal patch units are etched on this layer, with a side length L3 = 5.58 mm. This size is slightly larger than the square patch in the first layer, and it mainly controls the resonant characteristics of the high-frequency edge of the passband, and works in conjunction with the upper structure to create a steep high-frequency transition band.

[0036] In the preferred design of this embodiment, the geometric centers of the units on the first, second, and third metal patch layers are strictly aligned in the projection direction perpendicular to the frequency selective surface (FSS) plane to ensure the symmetry of the structure and guarantee dual polarization performance.

[0037] The geometry of the metal patch units corresponding to the second metal patch layer includes a cross shape, a variant of the cross shape, and a Jerusalem cross shape. When the geometry is cross-shaped, its arm length is equal to the structural period of 7 mm, and the arm width is 0.7 mm. The cross-shaped structure generates resonance in the passband center and high-frequency region, and through its cross arms, it generates complex electromagnetic coupling with the upper and lower square patches, playing a key role in widening the passband, especially improving the transmission performance in the high-frequency band.

[0038] The dielectric constant of the first dielectric substrate is greater than that of the second dielectric substrate, and the thickness of the first dielectric substrate is less than that of the second dielectric substrate. Optionally, the relative dielectric constant of the first dielectric substrate is 2.7, and the thickness is 1.05 mm. The relative dielectric constant of the second dielectric substrate is 2.3, and the thickness is 1.25 mm.

[0039] This asymmetric dielectric configuration of "thin layer with high dielectric constant + thick layer with low dielectric constant" is an effective means to optimize the resonant peak distribution, improve passband flatness, and broaden the operating bandwidth in multilayer FSS.

[0040] The first dielectric substrate serves as a support and isolation element. Furthermore, the specific dielectric constant and thickness of the first dielectric substrate, together with the first metal patch unit, determine the equivalent reactance of the first-stage resonant network, affecting impedance matching and bandwidth.

[0041] The passband frequency range of the frequency selective surface is 7 GHz to 13 GHz; the average power transfer efficiency of the frequency selective surface in the passband frequency range is greater than 0.85.

[0042] The frequency selective surface has stopbands including a first stopband and a second stopband, with the first stopband ranging from 0.1 GHz to 6 GHz and the second stopband ranging from 14 GHz to 18 GHz. The average insertion loss of the frequency selective surface is less than -13 dB across both stopbands.

[0043] Within the incident angle range of 0° to 60°, the frequency-selective surface maintains both passband and stopband characteristics for both TE-polarized and TM-polarized incident electromagnetic waves.

[0044] The frequency selective surface has transition bands including a first transition band and a second transition band; the first transition band ranges from 6 GHz to 7 GHz, and the second transition band ranges from 13 GHz to 14 GHz.

[0045] To verify the performance of the frequency-selective surface provided in this embodiment of the invention, a full-wave simulation analysis of the structure was performed using electromagnetic simulation software (CSTMicrowave Studio). During the simulation, the FSS was placed in an air environment, and periodic boundary conditions and Floquet port excitation were used.

[0046] Figure 3 and Figure 4 The simulated power transmission efficiency and transmission coefficient of the frequency-selective surface for TE-polarized waves are shown under different incident angles (θ = 0°, 15°, 30°, 45°, 60°). As can be seen from the figure:

[0047] 1. The transmission coefficient remains at a high level in the frequency band from 7 GHz to 13 GHz, and its average transmission efficiency is calculated to be greater than 0.85, forming a high-performance passband.

[0048] 2. In the frequency bands of 0.1 GHz to 6 GHz and 14 GHz to 18 GHz, the transmission coefficient is low, forming an effective stopband, and the average insertion loss is less than -13 dB.

[0049] 3. The transition bands between the passband and stopband are located at 6 GHz-7 GHz and 13 GHz-14 GHz, respectively, indicating that the structure has high frequency selectivity.

[0050] 4. This invention has good angular stability over a wide incident angle range, which can meet the application scenarios of large-angle oblique incidence of electromagnetic waves in practical engineering.

[0051] Figure 5 and Figure 6 Simulated curves of power transmission efficiency and transmission coefficient for TM-polarized waves are shown for this frequency-selective surface under different incident angles (incident angle θ = 0°, 15°, 30°, 45°, 60°). Its performance is highly similar to that under TE polarization conditions, demonstrating the excellent dual-polarization operating characteristics of this invention.

[0052] To quantitatively evaluate the performance of the frequency selective surface proposed in this invention under actual operating conditions, Tables 1 and 2 list the simulation data of the average power transfer efficiency of the FSS in the passband and the average insertion loss in the stopband when TE-polarized and TM-polarized waves are incident at different angles (0°, 15°, 30°, 45°, 60°).

[0053] Table 1. Average power transfer efficiency in the passband (7-13 GHz) under different polarizations and incident angles.

[0054]

[0055] Table 2. Average insertion loss in the stopband at different polarizations and incident angles (unit: dB)

[0056]

[0057] At vertical incidence (0°), the FSS of this invention maintains an average power transmission efficiency of 0.94 for both TE and TM polarized waves across an ultra-wide passband (7-13 GHz), achieving efficient signal transmission. Even under large-angle oblique incidence (60°), the average efficiency remains above 0.82. The decrease in passband efficiency with angle variation is not significant, and the performance values ​​for TE and TM polarization are close, demonstrating that the structure of this invention possesses excellent wide-angle stability and polarization insensitivity.

[0058] Within the low-frequency stopband (0.1 GHz–6 GHz) and high-frequency stopband (14 GHz–18 GHz), the average insertion losses under TE and TM polarization are -15.10 dB and -13.30 dB, respectively, with suppression depths exceeding -20 dB at some frequencies, demonstrating excellent out-of-band signal rejection capabilities. While the stopband suppression performance under TM polarization shows a certain expected decrease as the incident angle increases to 60°, the average insertion loss in both stopbands remains consistently below -11 dB, meeting the stringent requirements for out-of-band interference suppression in engineering applications (typically below -10 dB). The suppression performance under TE and TM polarization also exhibits consistency.

[0059] In summary, the embodiments of the present invention achieve ultra-wideband, high-transmission, high-suppression, and stable dual-polarization bandpass filtering functions through a specific combination of a first-layer square patch (5.35 mm), a second-layer cross-shaped patch (arm length 7 mm, arm width 0.7 mm), a third-layer square patch (5.58 mm), and two layers of asymmetric dielectric (ε1=2.7, H1=1.05 mm; ε2=2.3, H2=1.25 mm).

[0060] The above embodiments are used to explain and illustrate the present invention, and not to limit it. Those skilled in the art should understand that any modifications and changes made to the present invention within the spirit and scope of the claims fall within the protection scope of the present invention.

Claims

1. A bandpass dual-polarization frequency selective surface, characterized in that, The system comprises a first metal patch layer, a first dielectric substrate, a second metal patch layer, a second dielectric substrate, and a third metal patch layer, which are stacked sequentially from top to bottom. Each of the first, second, and third metal patch layers contains a corresponding metal patch unit. The metal patch units of the first, second, and third metal patch layers are all four-fold rotationally symmetric structures. The metal patch units corresponding to the first and third metal patch layers have the same geometry but different dimensions, while the geometry of the metal patch units corresponding to the second metal patch layer is different from that of the metal patch units in the first metal patch layer. The metal patch unit corresponding to the first metal patch layer has a square geometry and is a solid structure; the side length of the metal patch unit corresponding to the first metal patch layer is less than the structural period. The first dielectric substrate and the second dielectric substrate have different dielectric constants and thicknesses; The dielectric constant of the first dielectric substrate is greater than that of the second dielectric substrate, and the thickness of the first dielectric substrate is less than that of the second dielectric substrate. The geometry of the metal patch unit corresponding to the second metal patch layer includes a cross shape; the arm length of the metal patch unit corresponding to the second metal patch layer is equal to the structural period.

2. The bandpass dual-polarization frequency selective surface according to claim 1, characterized in that, The passband frequency range of the frequency selective surface is 7 GHz to 13 GHz; the average power transfer efficiency of the frequency selective surface within the passband frequency range is greater than 0.

85.

3. The bandpass dual-polarization frequency selective surface according to claim 1, characterized in that, The frequency selective surface has stopbands including a first stopband and a second stopband, the first stopband ranging from 0.1 GHz to 6 GHz and the second stopband ranging from 14 GHz to 18 GHz; the average insertion loss of the frequency selective surface in the two stopbands is less than -13 dB.

4. An antenna radome, characterized in that, A bandpass dual-polarization frequency selective surface comprising any one of claims 1-3.

5. A communication device, characterized in that, It comprises a bandpass dual-polarized frequency selective surface according to any one of claims 1-3, or comprises the radome according to claim 4.

6. A radar system, characterized in that, It comprises a bandpass dual-polarized frequency selective surface according to any one of claims 1-3, or comprises the radome according to claim 4.

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