Frequency selective surface radome for base station antennas

Abstract

The present application provides a frequency selective surface radome for base station antennas. The radome comprises a first dielectric layer, a common metal layer, and a second dielectric layer; the common metal layer is disposed between the first and second dielectric layers; a first patch resonant unit is attached to the upper surface of the first dielectric layer, and a second patch resonant unit is attached to the lower surface of the second dielectric layer; both the first and second patch resonant units are composed of four groups of patch resonators, each of which is provided with resonant slots of the same size, enabling accurate control of specific modes of the patch resonators and improving the stability of filtering performance.

Description

Technical Field

[0001] The present application relates to the field of electromagnetic field technology, and in particular to a frequency selective surface antenna cover facing a base station antenna. Background Art

[0002] With the rapid development of mobile communications technology, base station antennas supporting multiple frequency bands and multiple standards have become mainstream in the industry. Since base station antennas are often located outdoors, they are directly exposed to natural elements such as storms, snow, and solar radiation. This can lead to reduced antenna accuracy, shortened lifespan, and poor operational reliability. To protect the antenna from external environmental influences, a radome is typically installed over the antenna housing.

[0003] At present, the antenna cover based on frequency selective surface can enhance the anti-interference ability and stealth performance of the antenna system. It has the function of passband transmission within the working frequency band and suppression outside the working frequency band, which can reduce the impact of interference frequency components.

[0004] However, the existing antenna cover has a high cross-section height and poor angular stability, which affects the application effect and performance stability of the base station antenna. Summary of the Invention

[0005] The present application provides a frequency selective surface radome facing a base station antenna, so as to solve the technical problem of poor angular stability of the radome in the prior art.

[0006] The frequency selective surface radome provided in this application for base station antennas includes:

[0007] a first dielectric layer, a common metal layer, and a second dielectric layer;

[0008] The common metal layer is provided between the first dielectric layer and the second dielectric layer;

[0009] The upper surface of the first dielectric layer is covered with a first patch resonant unit, and the lower surface of the second dielectric layer is covered with a second patch resonant unit;

[0010] The first patch resonant unit and the second patch resonant unit are both composed of four groups of patch resonators, and the four groups of patch resonators are further provided with resonant slots of the same size.

[0011] Optionally, the four groups of patch resonators are all in the shape of right-angled isosceles triangles;

[0012] The resonant slots are respectively arranged on the first right-angled sides and the second right-angled sides of the four groups of patch resonators.

[0013] Optionally, the four groups of patch resonators include a first patch resonator combination and a second patch resonator combination;

[0014] The first patch resonator combination includes a first patch resonator and a second patch resonator, and the second patch resonator combination includes a third patch resonator and a fourth patch resonator.

[0015] Optionally, the first patch resonator and the second patch resonator are arranged to be translated along a diagonal direction;

[0016] The third patch resonator and the fourth patch resonator are arranged in a translational manner along another diagonal direction.

[0017] Optionally, a first rectangular groove is formed on the common metal layer;

[0018] The positions of the first rectangular slots correspond to the positions of the resonant slots on the four groups of patch resonators.

[0019] Optionally, the first rectangular slots have the same size as the resonant slots, and the number of the first rectangular slots is the same as the number of the resonant slots.

[0020] Optionally, four groups of second rectangular grooves are further provided on the common metal layer, and positions of the four groups of second rectangular grooves respectively correspond to the center positions of the hypotenuses of the four groups of patch resonators.

[0021] Optionally, the four groups of patch resonators have the same size parameters.

[0022] Optionally, the first dielectric layer, the common metal layer and the second dielectric layer are of the same size.

[0023] Optionally, the first dielectric layer has a dielectric constant of 2.2 and a thickness of 1.57 mm;

[0024] The second dielectric layer has a dielectric constant of 2.2 and a thickness of 1.57 mm.

[0025] The present application provides a frequency selective surface antenna cover for a base station antenna, comprising a first dielectric layer, a common metal layer, and a second dielectric layer; the common metal layer is arranged between the first dielectric layer and the second dielectric layer; the upper surface of the first dielectric layer is covered with a first patch resonant unit, and the lower surface of the second dielectric layer is covered with a second patch resonant unit; the first patch resonant unit and the second patch resonant unit are both composed of four groups of patch resonators, and the four groups of patch resonators are also provided with resonant slots of the same size, thereby realizing accurate regulation of specific modes of the patch resonators and improving the stability of filtering performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0027] Figure 1 A schematic diagram of the three-dimensional structure of the frequency selective surface radome facing the base station antenna provided in this application;

[0028] Figure 2 A front view of the frequency selective surface radome facing the base station antenna provided in this application;

[0029] Figure 3 A schematic diagram of the structural dimensions of the first and second dielectric layers in the frequency selective surface radome facing the base station antenna provided in this application;

[0030] Figure 4 A schematic diagram showing the dimensions of a common metal layer in a frequency selective surface radome facing a base station antenna provided in this application;

[0031] Figure 5 This is a simulation result diagram of Example 1 of the frequency selective surface radome facing the base station antenna provided by this application;

[0032] Figure 6 A diagram showing simulation results of the second embodiment of the frequency selective surface radome facing the base station antenna provided in this application;

[0033] Figure 7 This is a simulation result diagram of Example 3 of the frequency selective surface radome facing the base station antenna provided by this application;

[0034] Figure 8 This is a simulation result diagram of Example 4 of the frequency selective surface antenna cover facing the base station antenna provided in this application.

[0035] Reference numerals:

[0036] 100 - frequency selective surface antenna cover facing the base station antenna; 101 - first dielectric layer; 102 - common metal layer; 103 - second dielectric layer; 104 - resonant slot; 105 - first rectangular slot; 106 - second rectangular slot; 107 - first patch resonator; 108 - third patch resonator; 109 - second patch resonator; 110 - fourth patch resonator.

[0037] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0038] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0039] Traditional base station radomes primarily protect antennas from the external environment, but their performance improvement is limited. While existing frequency-selective surface radomes can provide certain bandpass filtering and stealth characteristics, their design, when applied to dual-bandpass, dual-polarization base station antennas, often results in increased structural complexity and decreased angular stability, making it difficult to meet the requirements of large-scale engineering applications. Therefore, developing a low-profile frequency-selective surface radome that supports dual-bandpass, dual-polarization, and exhibits excellent angular stability and out-of-band suppression is crucial for improving the performance of base station antenna systems.

[0040] This technical solution proposes a dual-bandpass frequency selective surface antenna cover based on isosceles right-angled triangle patch resonators and a multi-layer structure. By optimizing the patch resonant mode, the rectangular slot layout of the common metal layer, and the resonant coupling method, it achieves dual-bandpass, dual-polarization support, good angular stability, and excellent out-of-band interference suppression capabilities. While improving the anti-interference capability and stealth characteristics of the antenna system, it maintains a low-profile design and is easy to manufacture, making it suitable for modern high-performance wireless communication systems.

[0041] The following specific embodiments describe in detail the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0042] Figure 1 This is a schematic diagram of the three-dimensional structure of the frequency selective surface antenna cover facing the base station antenna provided in this application. Figure 1 As shown, the frequency selective surface radome 100 for base station antennas adopts a multi-layer structure and a specific patch resonant unit design to achieve dual-band passband characteristics, while also having good angular stability and low profile features. Its specific structure is as follows:

[0043] The frequency selective surface radome facing the base station antenna consists of a first dielectric layer 101, a common metal layer 102, and a second dielectric layer 103. The first dielectric layer 101 is located at the top, with a first patch resonant unit attached to its upper surface for receiving external electromagnetic waves and exciting the resonant mode. The second dielectric layer 103 is located at the bottom, with a second patch resonant unit attached to its lower surface. Each of the first and second patch resonant units consists of four groups of patch resonators: four patch resonators arranged on the upper surface of the first dielectric layer 101 and four patch resonators arranged on the lower surface of the second dielectric layer 103, for receiving electromagnetic waves transmitted from the first patch resonant unit. Each patch resonator is an isosceles right triangle structure with a resonant slot 104 of the same size inside to optimize the electromagnetic field distribution characteristics of the resonant mode and improve the transmission performance within the operating passband of the frequency selective surface radome.

[0044] Specifically, a resonant slot 104 is provided on the first right-angled side and the second right-angled side of each isosceles right-angled triangle patch resonator. The resonant slot can be configured to not affect the TM 10 mode resonant frequency, the TM 11 The control of the mode resonance frequency, where TM stands for transverse magnetic mode, means that in this mode, the magnetic field of the electromagnetic wave has no component in the propagation direction, while the electric field has a component in the propagation direction. 10 The mode is the most basic transverse magnetic mode. "10" means that on the cross section, the electric field has a half-wave change in one direction (usually the width direction) and no change in the other direction (usually the height direction). This mode can propagate within a specific frequency range. 11 A mode indicates that the electric field has a half-wave variation in both directions across the cross section. This mode typically appears at higher frequencies because it requires higher frequencies to support this more complex field distribution.

[0045] The common metal layer 102 is located between the first and second dielectric layers 103 to provide metal shielding properties. At the same time, rectangular coupling gaps are formed at specific locations to adjust the transmission of electromagnetic waves. The rectangular coupling gaps include four groups of first rectangular slots 105 and four groups of second rectangular slots 106. The arrangement of the first rectangular slots 105 and the second rectangular slots 106 can further improve the dual-band passband and angular stability of the frequency selective surface antenna cover. Specifically, the first rectangular slots 105 match the first right-angled side and the second right-angled side of the resonant slot 104 on each isosceles right-angled triangle patch resonator. The first rectangular slots 105 have the same size and number as the resonant slots 104 to ensure that the coupling paths between the two layers of patch resonators are consistent, ensuring TM 10 and TM 11The high-efficiency coupling of the modes between the double-layer patch resonators improves the low-frequency bandpass performance and optimizes the high-frequency bandpass filtering characteristics. The second rectangular slot 106 matches the center position of the hypotenuse of the isosceles right triangle, further enhancing the high-frequency mode (TM 11 ) energy transmission, making high-frequency bandpass filtering more stable.

[0046] The specific steps of the frequency selective surface radome are as follows: electromagnetic waves in free space are incident on the first patch resonant unit, exciting the TM 10 and TM 11 The first rectangular slot 105 is located in the common metal layer 102, and its size and position match the resonant slot 104 on the first patch resonant unit, so that TM 10 Patterns and TMs 11 The mode can be transmitted to the second patch resonant unit and resonate again on the second patch resonant unit. Therefore, the overall frequency selection mechanism includes the first patch resonant unit to the first rectangular slot 105 and then to the second patch resonant unit, wherein the first rectangular slot 105 enhances the low frequency mode (TM 10 ) transmission, making the low-frequency passband more stable, and the second rectangular slot 106 optimizes the high-frequency mode (TM 11 ) transmission, making the high-frequency passband more stable.

[0047] The frequency-selective surface radome for base station antennas provided in this application optimizes dual-bandpass performance and improves angular stability by providing a first rectangular slot 105 (corresponding to the resonant slot 104) and a second rectangular slot 106 (corresponding to the center of the hypotenuse) in the common metal layer 102. This structure not only enhances the transmission performance of both low- and high-frequency modes, but also reduces manufacturing complexity and improves engineering feasibility, providing a novel solution for the design of high-performance base station radomes.

[0048] Figure 2 This is a front view of the frequency selective surface antenna cover facing the base station antenna provided in this application. Figure 2 As shown, the frequency selective surface radome facing the base station antenna adopts a multi-layer structure. While maintaining a low profile, it ensures efficient dual-band bandpass filtering characteristics and excellent angular stability by optimizing the size of the patch resonator, the physical parameters of the dielectric layer, and the consistency of the overall structure.

[0049] First, to ensure the consistency of the resonance characteristics, the dimensions of the four groups of patch resonators need to be set to the same parameters. This ensures that each resonator performs consistently under the same electromagnetic environment, thereby ensuring the same frequency response in the dual polarization directions, thereby improving the polarization stability of the frequency selective surface antenna cover.

[0050] Secondly, since the resonators have the same size, they can regulate the coupling strength of the first rectangular slot 105 and the second rectangular slot 106 to TM 10 and TM 11 The response of the modes remains consistent, resulting in more stable filtering performance within the dual-band passband. Furthermore, since the dimensions of all layers are perfectly matched, the mechanical strength of the entire structure is enhanced, avoiding stress concentration or deformation caused by different dimensions and improving the reliability of the frequency selective surface radome.

[0051] Specifically, the dielectric constant of the first dielectric layer 101 and the second dielectric layer 103 of the present invention are both 2.2 and 1.57 mm thick. The advantage of selecting a dielectric constant of 2.2 is that it provides low reflection and high transmission efficiency. This allows the frequency selective surface radome to reduce the energy reflected by electromagnetic waves during transmission, thereby improving signal transmission efficiency and bandpass filtering performance.

[0052] On the other hand, the relatively thin 1.57mm thickness keeps the overall thickness of the frequency selective surface radome low, meeting the requirements of low-profile and lightweight base station antennas. This thickness improves the magnetic coupling efficiency between the upper and lower patch resonators, enabling the first and second rectangular slots 105, 106 to efficiently transmit dual-frequency modes, improving bandpass filtering characteristics.

[0053] from Figure 2 It can be seen that the frequency selective surface antenna cover adopts a three-layer structure, including: upper substrate (first dielectric layer 101): 1.57 mm, dielectric constant of 2.2, common metal ground (middle metal layer): lower substrate (second dielectric layer 103): 1.57 mm, dielectric constant of 2.2, upper metal (upper patch resonator), lower metal (lower patch resonator). This symmetrical structure can ensure more uniform electromagnetic wave transmission, and because the structure, material and size of the upper and lower layers are completely symmetrical, the frequency selective surface antenna cover will not produce directional deviation during the electromagnetic wave transmission process, further ensuring stable bandpass characteristics under different incident angles.

[0054] In addition, the resonators of the upper and lower layers are of the same size, and combined with the first rectangular groove 105 and the second rectangular groove 106 of the common metal layer 102, the TM 10 and TM 11 The dual-polarization response of the mode is consistent. Since the thickness and size of the dielectric layers are completely consistent, the stress distribution of the entire structure is uniform, avoiding structural bending or deformation caused by differences in thickness or size between layers, and improving the mechanical stability of the radome.

[0055] Figure 3This is a schematic diagram of the structural dimensions of the first dielectric layer and the second dielectric layer in the frequency selective surface antenna cover for the base station antenna provided in this application. Figure 3 The figure shows a unit structure of a frequency selective surface antenna cover based on isosceles right triangle patch resonators. Its main components include: four isosceles right triangle patch resonators, two of which are placed in a diagonal direction and two are placed in a diagonal direction, and each forms a symmetrical structure along the diagonal. Each patch resonator has a slot structure inside to control the electromagnetic field distribution of the resonant mode and improve the filtering performance. The period parameter p represents the period of the unit structure, determines the repetitive arrangement of the entire frequency selective surface antenna cover, and affects the frequency selection characteristics. The gap g represents the distance between adjacent patch resonators. For example, g = 3mm, which affects the coupling strength between the resonators and thus the bandwidth and resonant frequency. The patch side length l1 directly determines the resonant frequency and affects the low-frequency and high-frequency operating ranges.

[0056] Through the isosceles right triangle structure and slot design, the TM 10 and TM 11 Precise control of the pattern enables the frequency-selective surface radome to possess dual-bandpass filtering capabilities. This structure maintains stable frequency selectivity even under wide angles of incidence, minimizing the impact of angle on transmission performance. Furthermore, due to the symmetrical arrangement of the four triangular resonators along two diagonal lines, the structure can simultaneously support x- and y-polarized signals, improving the system's communication capacity and anti-interference capabilities.

[0057] On the other hand, the four patch resonators can be divided into a first patch resonator combination and a second patch resonator combination, and the electromagnetic coupling characteristics are optimized through a reasonable arrangement, thereby improving the dual-polarization performance and angular stability. Among them, the first patch resonator combination includes a first patch resonator 107 and a second patch resonator 109, which are mainly responsible for the electromagnetic wave resonance response in the first diagonal direction, wherein the first diagonal direction is as follows Figure 3 The second patch resonator combination includes a third patch resonator 108 and a fourth patch resonator 110, which are mainly responsible for the electromagnetic wave resonance response in the second diagonal direction, wherein the second diagonal direction is as shown in FIG. Figure 3 By periodically arranging two groups of patch resonators along the first diagonal direction and the second diagonal direction, respectively, the same resonant response can be formed in the two orthogonal polarization diagonal directions, thereby achieving dual-polarization characteristics in the two orthogonal diagonal directions.

[0058] Furthermore, the electromagnetic waves in the two diagonal polarization directions can be symmetrically decomposed into electromagnetic waves polarized along the x-axis and y-axis directions, respectively, and the combination of the two groups of patch resonators has the following characteristics: the low-frequency resonance mode (TM) of the first patch resonator 107 and the second patch resonator 109 10 ) and high frequency resonant modes (TM 11 ) are symmetrically and periodically distributed along the first diagonal line; the low-frequency resonance mode (TM) of the third patch resonator 108 and the fourth patch resonator 110 10 ) and high frequency resonant modes (TM 11 ) are symmetrically and periodically distributed along the second diagonal. Such electromagnetic wave polarization characteristics and modal electromagnetic field distribution characteristics mean that the structural layout adopted by the present invention still has dual-polarization characteristics in the two orthogonal directions of the x-axis and y-axis. Furthermore, this layout, which takes into account both the high symmetry and periodicity of the structure and the electromagnetic field distribution of the high- and low-frequency resonant modes, enables the radome to maintain stable transmission characteristics under large angles of incidence, improving angular stability and, in turn, increasing the channel capacity and anti-interference capability of the communication system.

[0059] The frequency selective surface antenna cover for base station antennas provided in this application achieves efficient dual-frequency filtering, wide-angle stability, dual-polarization support and low-profile design by optimizing the resonator arrangement, coupling gap and period design. It is suitable for modern base station antenna systems and improves anti-interference capability and channel capacity.

[0060] Figure 4 This is a schematic diagram of the dimensions of the common metal layer in the frequency selective surface antenna cover facing the base station antenna provided in this application. Figure 4 As shown, the main function of the common metal layer size is to provide an electromagnetic coupling channel. By optimizing the rectangular coupling gap on the metal layer, the electromagnetic wave transmission characteristics are regulated to achieve dual-polarization dual-bandpass characteristics.

[0061] Specifically, multiple rectangular coupling slots are formed on the common metal layer 102 to control the transmission characteristics of electromagnetic waves. The specific functions of the various dimensional parameters are as follows: p = 54mm represents the period of the frequency selective surface radome, which affects the array arrangement of the entire radome and determines the frequency selectivity. s1 =4mm, which defines the longitudinal and transverse coupling gap sizes, determines the transmission efficiency of electromagnetic waves through the metal layer, and directly affects the low frequency (TM 10 mode) coupling strength. 21 =10mm, l 22 = 1mm, used to adjust the electromagnetic transmission ability of different resonant modes, especially the high frequency mode (TM 11 ) transmission characteristics. l3 = 12.8 mm, which defines the coupling length in a specific area and optimizes the high frequency mode (TM11 ) matching effect. s1 =2mm, w s2 =0.5mm, w s3 =1mm, which defines the gap width and mainly controls the transmission bandwidth, so that the frequency selective surface antenna cover maintains stable frequency selection characteristics within the target frequency band. s3 =3.5mm, which works together with other gap lengths to optimize the dual-bandpass characteristics.

[0062] The rectangular gaps in the figure are distributed around the common metal layer 102, forming strong magnetic coupling with the patch resonators on the upper and lower layers, ensuring TM 10 and TM 11 The mode achieves efficient transmission within both passbands. The symmetrical layout of the rectangular slots, centered around point O, ensures dual-polarization characteristics, ensuring consistent transmission of x- and y-polarized signals at the same frequency. The tilted rectangular slots further optimize the transmission characteristics of incident electromagnetic waves in different polarization directions, improving angular stability.

[0063] In short, by rationally designing the longitudinal and transverse rectangular gaps (l s1 , l s2 ), optimize the transmission path of low-frequency signals and improve low-frequency bandpass performance. 21 , l 22 , l3, and other parameters optimize the high-frequency resonant mode, increasing high-frequency transmission efficiency and improving bandpass filtering performance. Furthermore, the structure achieves dual-polarization characteristics through evenly distributed slots along the x- and y-axes, allowing transmission of both x- and y-polarized signals and enhancing anti-interference capabilities. This optimized common metal layer design enables the frequency selective surface radome to meet the requirements of modern communication systems for efficient frequency selection, angular stability, and dual-polarization support, offering broad engineering application prospects.

[0064] Figure 5 This is a simulation result diagram of the first embodiment of the frequency selective surface antenna cover for base station antennas provided by this application. Figure 5 The figure shows the scattering parameter simulation results of the frequency selective surface radome facing the base station antenna in the electromagnetic simulation software under normal incidence and TE (Transverse Electric Incidence) polarized incident waves. This is used to determine the transmission and reflection characteristics of the frequency selective surface radome facing the base station antenna. The main observed parameters include:

[0065] S 11 (Reflection coefficient): Indicates the proportion of incident electromagnetic waves that are reflected. The lower the value, the smaller the energy reflection, indicating that the matching effect of the antenna cover at this frequency point is better.

[0066] S 21 (Transmission coefficient): Indicates the transmission characteristics of electromagnetic waves. The higher the value, the more likely the signal can pass through the frequency selective surface antenna cover structure.

[0067] Specifically, the figure shows two passband frequencies at 3.7 GHz and 5.0 GHz, respectively, demonstrating the FSS radome's dual-bandpass capability. The presence of two transmission poles in each frequency band indicates that the FSS radome has a higher-order filtering characteristic and offers improved selectivity.

[0068] The bandwidth characteristics include low-frequency passband and high-frequency passband. The center frequency of the low-frequency passband is 3.7 GHz, the -3dB bandwidth is between 3.60 GHz and 3.78 GHz, and the relative bandwidth is 4.7%. The center frequency of the high-frequency passband is 5.0 GHz, the -3dB bandwidth is between 4.96 GHz and 5.1 GHz, and the relative bandwidth is 2.9%. It can be seen that the low-frequency and high-frequency passband bandwidths of the frequency selective surface for base station antennas provided in this application are moderate, ensuring the stable transmission of communication signals.

[0069] In addition, regarding the transmission characteristics, by carefully observing S 21 It can be seen from the curve that within the two passband ranges, the transmission coefficient is close to 0dB, indicating that the frequency selective surface proposed in this application has extremely high transmission efficiency within the target frequency band and can effectively transmit signals, while having good suppression capability outside the passband.

[0070] Secondly, as for the out-of-band suppression characteristics, it can be seen from the figure that in the 3.0–3.5GHz and 5.2–6.0GHz frequency bands, S 21 It drops below -20dB, indicating that the antenna cover has a strong inhibitory effect on interference signals in these frequency bands, thereby improving the anti-interference capability.

[0071] The above simulation results verify the dual-bandpass, low insertion loss, high selectivity and out-of-band interference suppression capabilities of the frequency selective surface antenna cover for base station antennas proposed in this application, providing a high-efficiency and stable frequency selection solution for modern wireless communication systems, which is particularly suitable for 5G communications, satellite communications, and radar stealth systems.

[0072] Figure 6 This is a simulation result diagram of the second embodiment of the frequency selective surface antenna cover for base station antennas provided in this application. Figure 6 The figure shows the scattering parameter simulation results of the frequency selective surface radome facing the base station antenna in the electromagnetic simulation software under normal incidence and TM polarization incident wave, which is used to analyze the transmission and reflection characteristics of the frequency selective surface radome in this polarization mode. The main parameters include:

[0073] S11 (Reflection coefficient), low values (such as -10dB or less) indicate low reflection and the frequency selective surface antenna cover is well matched in this frequency band. The curve shows that at 3.7GHz and 5.0GHz, S 11 It is lower than -10dB, indicating that the frequency selective surface antenna cover has less reflection of TM polarized waves in these two frequency bands and can allow more signals to be transmitted.

[0074] S 21 (Transmission coefficient), a high value (close to 0dB) indicates high transmission efficiency, and the frequency selective surface antenna cover has good bandpass characteristics in this frequency band. It can be observed from the figure that around 3.7GHz and 5.0GHz, S 21 is relatively high (close to 0dB), indicating that the frequency selective surface radome has good dual-bandpass characteristics under TM polarization wave incidence.

[0075] Specifically, the dual-bandpass characteristics show two passband center frequencies of 3.7 GHz and 5.0 GHz, respectively, demonstrating that the FSS radome also possesses dual-bandpass capability for TM-polarized waves. Each passband has two transmission poles, indicating that the structure offers higher-order selectivity and allows for precise control of the passband frequency range.

[0076] Regarding bandwidth characteristics, the -3dB bandwidth is between 3.60GHz and 3.78GHz, with a relative bandwidth of 4.7%. The -3dB bandwidth of the high-frequency passband (5.0GHz) is between 4.96GHz and 5.1GHz, with a relative bandwidth of 2.9%. This bandwidth is suitable for dual-band communication systems such as Wi-Fi 6 and satellite communications.

[0077] For the transmission coefficient S 21 , which is close to 0 dB in the passband, indicating that the structure has high transmission efficiency for TM polarized waves and low insertion loss.

[0078] For out-of-band suppression capability, in the 3.0–3.5GHz and 5.2–6.0GHz bands, S 21 It decreases significantly, indicating that the frequency selective surface has a good filtering and suppression capability for out-of-band interference signals, which helps to improve the anti-interference capability of the system.

[0079] Figure 7 This is a simulation result diagram of the third embodiment of the frequency selective surface antenna cover for base station antennas provided by this application. Figure 7 As shown in the figure, the scattering parameter simulation results of the frequency selective surface antenna cover facing the base station antenna under TE (Transverse Electric Incidence) polarized incident waves at large angles of incidence in electromagnetic simulation software are shown.

[0080] The simulation shows that at different incident angles (𝜃=0 ∘ , 30 ∘ , 50 ∘ ) S under the condition 21 The transmission coefficient is used to determine the angular stability of the FSS radome. The passband center frequency and bandwidth barely change with incident angle, and the center frequencies of the low-frequency passband (approximately 3.7 GHz) and high-frequency passband (approximately 5.0 GHz) are essentially stable. This demonstrates that the FSS radome maintains stable frequency selectivity over a wide range of angles.

[0081] In addition, the insertion loss increases slightly as the angle increases (e.g. 𝜃=50 ∘ ), S 21 The curve drops slightly (insertion loss increases), but the overall change is small. This shows that the structure is highly adaptable to large-angle incidence and can still maintain high transmission efficiency.

[0082] On the other hand, the frequency selective surface radome of this application maintains good dual-band characteristics under both TE (transverse electric wave) and TM (transverse magnetic wave) polarizations, but its performance varies slightly with different polarizations. For example, under TE incident waves, the passband center frequency and bandwidth remain essentially unchanged, with only a slight increase in insertion loss. This indicates that the propagation characteristics of TE polarized waves are well matched to the structure and are unaffected by polarization changes. Under TM incident waves, the center frequency and bandwidth of the low-frequency passband (3.7 GHz) are stable, consistent with the TE wave performance, while the bandwidth of the high-frequency passband (5.0 GHz) is slightly offset. This may be due to a slightly different degree of coupling between the TM wave's magnetic field distribution and the TM11 resonant mode of the frequency selective surface radome, resulting in a slight impact on the high frequency portion.

[0083] Figure 8 This is a simulation result diagram of the fourth embodiment of the frequency selective surface antenna cover for base station antennas provided by this application. Figure 8 As shown, the scattering parameter simulation results of the frequency selective surface antenna cover facing the base station antenna under TM polarization incident waves at large angles of incidence in the electromagnetic simulation software are shown.

[0084] The figure shows different incident angles (𝜃=0 ∘ , 30 ∘ , 50 ∘ ) S under the condition 21 The coefficient is used to determine the angular stability of the FSS radome. As can be seen from the figure, the FSS radome facing the base station antenna has distinct transmission peaks at 3.7 GHz and 5.0 GHz, demonstrating its dual-bandpass characteristics. The frequencies of these two transmission peaks remain largely unchanged with the incident angle, indicating that the structure has good angular stability.

[0085] In addition, at 𝜃=0 ∘ to 𝜃=50 ∘ Within the range, the passband center frequency remains basically stable, and the insertion loss (S 21 Peak) at a larger incident angle (𝜃=50 ∘ ) increases slightly, but the change is small, indicating that the frequency selective surface radome facing the base station antenna has strong adaptability to different incident angles.

[0086] Secondly, it can be seen from the figure that in the frequency band above 5.2GHz, S 21 The significant decrease (below -20dB) shows that the frequency selective surface antenna cover can effectively suppress high-frequency interference signals and reduce interference to other systems.

[0087] The frequency selective surface radome for base station antennas proposed in this application has good angular stability. ∘ to 50 ∘ Within the range of incident angles, the passband center frequency and bandwidth remain basically unchanged; high transmission efficiency, low insertion loss, and excellent transmission performance in the 3.7GHz and 5.0GHz frequency bands; excellent out-of-band interference suppression capability, with significant transmission attenuation (less than -40dB) in the frequency band above 5.2GHz, effectively reducing interference, and is suitable for 5G communications, satellite communications, and stealth radar systems with wide-angle incidence.

[0088] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of the present application and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0089] It should be understood that the present application is not limited to the exact structure described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A frequency selective surface radome facing a base station antenna, characterized in that: include: a first dielectric layer, a common metal layer, and a second dielectric layer; The common metal layer is arranged between the first dielectric layer and the second dielectric layer; The upper surface of the first dielectric layer is covered with a first patch resonant unit, and the lower surface of the second dielectric layer is covered with a second patch resonant unit; The first patch resonant unit and the second patch resonant unit are both composed of four groups of patch resonators, and the four groups of patch resonators are further provided with resonant slots of the same size; The four groups of patch resonators are all in the shape of right-angled isosceles triangles; the resonant slots are respectively arranged on the first right-angled sides and the second right-angled sides of the four groups of patch resonators.

2. The frequency selective surface radome according to claim 1, wherein: The four groups of patch resonators include a first patch resonator combination and a second patch resonator combination; The first patch resonator combination includes a first patch resonator and a second patch resonator, and the second patch resonator combination includes a third patch resonator and a fourth patch resonator.

3. The frequency selective surface radome according to claim 2, characterized in that: The first patch resonator and the second patch resonator are arranged in a diagonal direction; The third patch resonator and the fourth patch resonator are arranged in a translational manner along another diagonal direction.

4. The frequency selective surface radome according to any one of claims 1 to 3, characterized in that: A first rectangular groove is formed on the common metal layer; The positions of the first rectangular slots correspond to the positions of the resonant slots on the four groups of patch resonators.

5. The frequency selective surface radome according to claim 4, characterized in that: The first rectangular slots have the same size as the resonant slots, and the number of the first rectangular slots is the same as the number of the resonant slots.

6. The frequency selective surface radome according to claim 4, characterized in that: Four groups of second rectangular grooves are further provided on the common metal layer, and the positions of the four groups of second rectangular grooves respectively correspond to the center positions of the hypotenuses of the four groups of patch resonators.

7. The frequency selective surface radome according to any one of claims 1 to 3, characterized in that: The size parameters of the four groups of patch resonators are all the same.

8. The frequency selective surface radome according to any one of claims 1 to 3, characterized in that: The first dielectric layer, the common metal layer and the second dielectric layer have the same size.

9. The frequency selective surface radome according to any one of claims 1 to 3, characterized in that: The dielectric constant of the first dielectric layer is 2.2 and the thickness is 1.57 mm; The second dielectric layer has a dielectric constant of 2.2 and a thickness of 1.57 mm.

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