A frequency selective surface with wide band, narrow transition band and good wide angle stability

Abstract

The application discloses a kind of broadband narrow transition zone and frequency selective surface with good wide-angle stability, belong to electromagnetic surface technical field.The frequency selective surface described in the application is composed of four layers structure, butterfly-shaped metal patch is printed on the 1st, 3rd layer dielectric plate, metal column connects butterfly-shaped metal patch up and down;Metal mesh is printed on the 2nd layer dielectric plate on single side;Cross-shaped patch is printed on the back side of butterfly-shaped metal patch, composite square patch is printed on the top layer and bottom layer dielectric plate respectively as wide-angle matching layer.The application designs the passband of frequency selective surface by designing the operating frequency band of butterfly-shaped dipole antenna, and adjusts the wide-angle stability by introducing wide-angle matching layer and capacitive patch.The application can realize stable passband transmission performance under different polarizations and incident angles within 2.3-4GHz, and the passband loss is within 1dB.The transition zone bandwidth of transistion is relatively narrow, which is 6.7%, the stopband frequency band is 0.5-2.15GHz, and the stopband suppression is greater than 10dB, with excellent reflection performance.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic surfaces, specifically relating to a frequency selective surface with a wide bandwidth, narrow transition band, and good large-angle stability. Background Technology

[0002] With the rapid development of communication technology, 5G communication systems are widely used. Meanwhile, 2G, 3G, and 4G systems continue to be used, leading to increasingly scarce antenna space resources. To address this issue, common-aperture base station antennas have emerged. To save space and cost, antenna arrays operating in different frequency bands are integrated onto the same aperture surface. However, in multi-frequency common-aperture antenna arrays, the stacking of antennas from different frequency bands complicates the electromagnetic environment, and the coupling between antennas from different frequency bands can affect the performance of the antenna array. Furthermore, in common-aperture base station antennas, antenna arrays from different frequency bands share the same metal reflector. With the development of mobile communication technology and the needs of base station construction, it may be necessary to set up high-frequency and low-frequency arrays as independent modules, thus requiring antenna arrays from different frequency bands to have dedicated reflectors.

[0003] A frequency selective surface (FSS) is a periodically arranged two- or three-dimensional structure whose response to electromagnetic waves varies with frequency. Based on its filtering characteristics for electromagnetic waves of different operating frequencies, incident angles, and polarization states, the FSS can be considered a spatial filter and is widely used in the electromagnetic field. To eliminate cross-band coupling and ensure the normal operation of antennas in different frequency bands, a FSS is introduced into a common-aperture antenna array. By designing its passband and stopband, transmission and reflection of specific frequency bands can be achieved, allowing high-frequency electromagnetic waves to pass without loss while ensuring good reflection of low-frequency electromagnetic waves. This places extremely high demands on the design of the FSS layer. It requires the FSS layer to have low loss and good large-angle stability within the passband; and to enable its flexible application in communication systems, the FSS needs to have a narrow passband and stopband transition bandwidth.

[0004] In 2004, Abbas Abbaspour-Tamijani et al. published "Antenna–Filter–AntennaArrays as a Class of Bandpass Frequency-Selective Surfaces," first proposing the FSS design concept based on the antenna-filter-antenna (AFA). An AFA module is a filter with a radiating port, integrated from two antennas and a central non-radiating resonant structure. Since then, the AFA-based design concept has been widely applied in FSS design. In 2017, Rana Sadaf Anwar et al. published "A Broadband Third-order Antenna-filter-antennaBased Frequency Selective Surface at High Oblique Angle of Incidence," proposing a broadband FSS based on AFA theory that can achieve dual polarization. While it has a wide bandwidth, its transition bandwidth is also relatively wide, making a fast transition between the passband and stopband impossible. Furthermore, the filtering response of the AFA-FSS is achieved through the design of a non-radiating structure, limiting its design freedom.

[0005] In 2022, Huawei Lin et al. published "High-Selectivity FA-FA-Based Frequency Selective Surfaces Using Magnetoelectronic Dipole Antennas," which first proposed the FSS design concept based on a filter antenna-filter antenna (FA-FA). The radiation null of the filter antenna is used to design the transmission null of the FSS, thereby increasing the design freedom of the FSS. This structure can maintain good transmission performance in the passband and good stopband suppression when the electromagnetic wave is incident at 0 degrees. However, this scheme also has some shortcomings. Its stability at large angles is poor, especially when the electromagnetic wave is incident at 60 degrees, making it difficult to apply to antenna arrays to ensure good transmission characteristics. In addition, it uses a relatively thick dielectric substrate, which is difficult to process and apply in practice.

[0006] To address the aforementioned problems, this invention discloses a frequency selective surface with a wide bandwidth, narrow transition band, and good large-angle stability. Summary of the Invention

[0007] Based on the aforementioned background technology, this invention addresses the shortcomings of existing technologies by proposing a frequency selective surface with a wide bandwidth, narrow transition band, and excellent large-angle stability. In this frequency selective surface, a butterfly dipole antenna is used as the base antenna, its operating bandwidth being used for FSS passband design. Metal pillars are used as transmission lines to connect the upper and lower symmetrical dipoles, and a metal mesh in the middle layer acts as the ground plane for FSS stopband design. Cross-shaped shaped patches and a wide-angle matching layer are employed to adjust the large-angle stability of the frequency selective surface. This frequency selective surface exhibits low-frequency reflection performance in the 0.5-2.15 GHz band and high-frequency transmission performance in the 2.3-4 GHz band; its passband loss is less than 1 dB within the 0-60° incident range, demonstrating excellent large-angle stability and achieving an extremely narrow transition bandwidth.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] The frequency selection surface is designed based on a butterfly dipole antenna and includes a dielectric substrate with two layers of printed butterfly metal patches and cross-shaped metal patches, metal pillars connecting the butterfly patches, a dielectric substrate with a layer of printed metal mesh conductors, and a dielectric substrate with a wide-angle matching layer printed on it.

[0010] A butterfly-shaped dipole antenna is printed on the top and third dielectric substrates and connected by metal pillars, providing a passband for the FSS design. A metal mesh conductor strip is printed on the second dielectric substrate as the antenna's reflector ground plane, providing a stopband for the FSS design. A cross-shaped patch is printed on the top and third dielectric substrates; a composite square patch is printed on the top and bottom dielectric substrates as a wide-angle matching layer, and both work together to improve the large-angle stability of the FSS.

[0011] The advantages of the frequency selective surface of the present invention are:

[0012] This invention uses a butterfly dipole antenna as the basic antenna element for the design of the FSS unit, which broadens the FSS passband and increases the design freedom of the FSS.

[0013] This invention features a wide passband (2.3-4 GHz), a wide stopband (0.5-2.15 GHz), and an extremely narrow transition band (6.7%). It exhibits good transmission performance within the passband and good reflection performance outside the passband.

[0014] This invention has excellent large-angle stability and can achieve large-angle passband characteristics with a transmission loss of less than 1dB at ±60 degrees. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the frequency selective surface unit structure described in this invention;

[0016] Figure 2 This is a side view of the frequency-selective surface unit structure described in this invention;

[0017] Figure 3 for Figure 1 The diagram shows an exploded view of the top-layer structure of the frequency-selective surface.

[0018] Figure 4 for Figure 1 The diagram shows an exploded view of the second layer structure of the frequency-selective surface.

[0019] Figure 5 for Figure 1 The diagram shows an exploded view of the third layer structure of the frequency-selective surface.

[0020] Figure 6 for Figure 1 The diagram shows an exploded view of the surface substructure for frequency selection.

[0021] Figure 7 This is a transmission characteristic curve of the frequency selective surface under TE and TM polarization in the 0.5-4 GHz band with 0° incident light, as shown in the embodiment of the present invention.

[0022] Figure 8 This is a transmission characteristic curve of the frequency selective surface under TE and TM polarization in the 0.5-4 GHz band with a 60° incident angle, as shown in the embodiment of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the embodiments described.

[0024] like Figure 1 and Figure 2As shown, the frequency-selective surface unit has a period of 30 mm and an overall height of 27.1 mm. The structure includes four dielectric substrates (2.1, 2.2, 2.3, 2.4) with a dielectric constant of 2.2, butterfly-shaped metal patches (1.1, 1.6), cross-shaped metal patches (1.2, 1.5), a metal mesh (1.4), composite square metal patches (1.3, 1.7), and a metal cylinder (2.5). The butterfly-shaped metal patches (1.1, 1.6) and cross-shaped patches (1.2, 1.5) are printed on both sides of dielectric substrates 2.1 and 2.3, respectively. The metal cylinder (2.5) connects the upper and lower butterfly-shaped patches. The metal mesh (1.4) is printed on dielectric substrate 2.2, and the composite square patches (1.3, 1.7) are printed on dielectric substrates 2.1 and 2.4, respectively. The dielectric substrates (2.1, 2.3) are 1 mm thick, and the dielectric substrates (2.2, 2.4) are 0.8 mm thick. The spacing between substrates 2.1 and 2.2 is 7 mm, the spacing between 2.2 and 2.3 is 6 mm, and the spacing between 2.3 and 2.4 is 10.5 mm.

[0025] The butterfly-shaped metal patches (1.1, 1.6) function as dipole antenna patches, the metal mesh (1.4) functions as a ground plane, and the metal pillars (2.5) connect the upper and lower dipole antennas. When the characteristic impedance of the metal pillars matches the input impedance of the dipole antennas, the currents on the upper and lower dipole patches are equal in amplitude and opposite in phase, forming a passband. The coupling effect between the cross-shaped patches (1.2, 1.5) and the butterfly-shaped patches is equivalent to a parallel capacitor. In this way, the common-mode resonance generated on the metal pillars at large angles of incidence is moved out of the passband. Together with the composite square patches (1.3, 1.7) which serve as a wide-angle matching layer, the angular stability of the FSS is adjusted.

[0026] like Figure 3 As shown, the butterfly patch size is (1.1)L a =9.1mm, L b =7mm, metal column (2.5) spacing L c =26.9mm, metal column radius R=0.7mm, composite square patch (1.3) side length L1=10.3mm, branch size L2=4mm. Cross-shaped patch (1.2) size is L p =14mm, W p =2.7mm. For example... Figure 4 As shown, the width of the metal mesh (1.4) is W=4mm. Figure 5 medium structural dimensions and Figure 3 The correspondence is the same. For example... Figure 6 As shown, the side length of the composite square patch (1.7) is L3=16.5mm, and the other parameters are L4=6mm and L5=4.6mm.

[0027] Figure 7The graph shows the 0° transmission characteristic of the frequency-selective surface unit structure in the above embodiment. It can be seen that when the electromagnetic wave is incident at 0°, the FSS has a transmission loss of less than 1 dB in the 2.3-4 GHz range, exhibiting good passband transmission characteristics; a stopband rejection of greater than 10 dB in the 0.5-2.15 GHz range, exhibiting good stopband rejection characteristics; and an extremely narrow transition bandwidth of 6.7%.

[0028] Figure 8 The graph shows the 60° transmission characteristic of the frequency selective surface unit structure in the above embodiment. It can be seen that when the electromagnetic wave is incident at 60°, the FSS has a transmission loss of less than 1 dB in the 2.3-4 GHz range, and this frequency selective surface has excellent large-angle stability.

[0029] The above description and embodiments are only some preferred examples of the present invention and do not constitute any limitation on the present invention. For those skilled in the art, this application can have various modifications and variations, but modifications and changes based on the concept of the present invention are still within the protection scope of the claims of the present invention.

Claims

1. A frequency selective surface with a wide bandwidth, narrow transition band, and good large-angle stability, characterized in that: The frequency selection surface comprises a four-layer dielectric substrate structure, consisting of upper and lower butterfly-shaped metal patches and connecting metal pillars, cross-shaped metal patches, metal grids, and composite square metal patches.

2. The frequency selective surface with a wide bandwidth, narrow transition band, and good large-angle stability according to claim 1, characterized in that, The butterfly-shaped metal patches are printed on the first and third layers of the dielectric substrate, respectively, and are symmetrically distributed along the diagonal of the dielectric substrate. The metal pillars connect them vertically.

3. The frequency selective surface with a wide bandwidth, narrow transition band, and good large-angle stability according to claim 1, characterized in that, The cross-shaped patch is printed on the back of the butterfly-shaped patch, and capacitive coupling is generated between the cross-shaped patch and the butterfly-shaped patch, which acts as an equivalent capacitor.

4. The frequency selective surface with wide bandwidth, narrow transition band, and good large-angle stability according to claim 1, characterized in that, The metal mesh is printed on one side of the second dielectric substrate and is located between the upper and lower butterfly patches, providing an equivalent reflective ground plane for the upper and lower butterfly dipole antennas.

5. A frequency selective surface with a wide bandwidth, narrow transition band, and good large-angle stability according to claim 1, characterized in that, The composite square patch is printed on the top and bottom substrates respectively, and the composite square structure is formed by etching short branches on the four sides of the base square patch.

6. A frequency selective surface with a wide bandwidth, narrow transition band, and good large-angle stability according to claim 1, characterized in that, The first and third dielectric substrates are 1 mm thick, the second and fourth dielectric substrates are 0.8 mm thick, and there is air between the dielectric substrates, with a total thickness of 27.1 mm.

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