A cross-band coupling interference suppression structure, suppression system and suppression method

Abstract

The application provides a cross-band coupling interference suppression structure, a suppression system and a suppression method. In the cross-band coupling interference suppression structure, a low-frequency antenna is fixed at a first height position above a frequency selective surface and used for transmitting a low-frequency signal; a high-frequency antenna unit is fixed at a second height position below the frequency selective surface and used for transmitting a high-frequency signal; the frequency selective surface is used for reflecting the low-frequency signal and transmitting the high-frequency signal; and a reflection layer is arranged below the low-frequency antenna unit and used for reflecting the high-frequency signal. The application sets the frequency selective surface capable of transmitting the high-frequency signal and reflecting the low-frequency signal in the cross-band structure, enhances the radiation performance of the low-frequency signal of the low-frequency band antenna by reflecting the low-frequency signal, keeps the high-frequency band antenna electromagnetically transparent, avoids introducing additional insertion loss, reduces the cross-band coupling interference, and improves the working stability of the interference suppression structure.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a cross-band coupling interference suppression structure, suppression system and suppression method. Background Technology

[0002] With the accelerated deployment of 5G networks, the requirements for existing antenna deployment designs are gradually increasing. Existing antenna systems need to support multiple communication standards simultaneously and operate efficiently across multiple frequency bands. To minimize scattering interference and common-mode interference between low-frequency and high-frequency antennas within the same physical aperture, the Frequency Selective Surface (FSS) technology is proposed. This technology utilizes a two-dimensional periodic structure to exhibit frequency selectivity, meaning it displays high transmittance for electromagnetic waves of certain frequencies while exhibiting high reflectivity for others.

[0003] However, in dual-band shared aperture base station antennas, the frequency selective surface needs to act as a reflector for the low-frequency antenna to enhance its radiation performance, while maintaining electromagnetic transparency for the high-frequency antenna to avoid introducing additional insertion loss. Traditional designs place the high-frequency and low-frequency antennas in the same space, and the frequency selective surface is often optimized only for the performance of a single frequency band, making it difficult to simultaneously meet the requirements of both high and low-frequency antennas. This necessitates the use of multi-layer or multiple frequency selective surface structures to maintain low-frequency reflection performance while satisfying high-frequency transmittance, resulting in a complex structure and poor common-mode interference suppression in dual-band shared aperture base station antennas.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a cross-band coupling interference suppression structure, suppression system and suppression method to solve the problems of complex structure, low stability and high actual production and processing cost of existing coupling interference suppression structures for high and low frequency band antennas based on frequency selective surface design.

[0006] The technical solution of the present invention is as follows: This invention provides a cross-band coupling interference suppression structure, comprising: a low-frequency antenna element, a high-frequency antenna element, a frequency selective surface, and a reflective layer; wherein, The low-frequency antenna is fixed at a first height position above the frequency selection surface and is used to transmit low-frequency signals. The high-frequency antenna unit is fixed at a second height position below the frequency selective surface and is used to transmit high-frequency signals. The frequency selective surface is used to reflect the low-frequency signal and transmit the high-frequency signal; The reflective layer is disposed below the low-frequency antenna unit and is used to reflect high-frequency signals.

[0007] In a further embodiment of the present invention, the frequency selection surface includes a bandpass filter structure, a low-pass filter structure, and a selection support substrate. The bandpass filter structure and the low-pass filter structure are disposed on the upper surface of the selection support substrate, and the low-pass filter structure is disposed at the edge of the selection support substrate.

[0008] In a further embodiment of the present invention, the bandpass filter structure includes a plurality of bandpass filter units, each bandpass filter unit comprising: a first microstrip end, a second microstrip end, a third microstrip end, a fourth microstrip end, a first resonant structure, a first microstrip connecting line, a second microstrip connecting line, a third microstrip connecting line, and a fourth microstrip connecting line; wherein, The first resonant structure is located at the center of the bandpass filter unit, and the first resonant structure is connected to the first microstrip connection line, the second microstrip connection line, the third microstrip connection line and the fourth microstrip connection line in a clockwise direction. The first microstrip connecting line is connected to the first microstrip end, the second microstrip connecting line is connected to the second microstrip end, the third microstrip connecting line is connected to the third microstrip end, and the fourth microstrip connecting line is connected to the fourth microstrip end.

[0009] In a further embodiment of the present invention, the low-pass filter structure includes four low-pass filter units, each of which is disposed at one of the four corners of the frequency support substrate. The low-pass filter unit includes a first planar spiral section, a second planar spiral section, a third planar spiral section, a fourth planar spiral section, a second resonant structure, a first spiral end, a second spiral end, a third spiral end, and a fourth spiral end; wherein, the second resonant structure is located at the center of the low-pass filter unit and is connected to the first planar spiral section, the second planar spiral section, the third planar spiral section, and the fourth planar spiral section in a clockwise direction respectively; The first planar spiral portion is connected to the first spiral end, the second planar spiral portion is connected to the second spiral end, the third planar spiral portion is connected to the third spiral end, and the fourth planar spiral portion is connected to the fourth spiral end.

[0010] In a further embodiment of the present invention, the first resonant structure and / or the second resonant structure are complementary open-loop resonant structures; the complementary open-loop resonant structure includes: a central coupling portion, a first high-impedance line, a second high-impedance line, a third high-impedance line, and a fourth high-impedance line, wherein the first high-impedance line, the second high-impedance line, the third high-impedance line, and the fourth high-impedance line are respectively connected to the central coupling portion.

[0011] In a further embodiment of the present invention, the planar helical section includes: a first-port microstrip line, a second-port microstrip line, a planar helical inductor structure, a first open-circuit stub, and a second open-circuit stub; wherein, The input terminal of the planar spiral inductor structure is connected to the first port microstrip line, and the spiral center of the planar spiral inductor structure is connected to the second port microstrip line. The second port microstrip line is collinear with the first port microstrip line; The first open-circuit stub is connected to the first port microstrip line, and the second open-circuit stub is connected to the second port microstrip line.

[0012] A further embodiment of the present invention includes a balancing support; one end of the balancing support is perpendicularly connected to the frequency selection surface, and the other end of the balancing support is perpendicularly connected to the low-frequency antenna unit; the balancing support includes a first balancing substrate and a second balancing substrate, the first balancing substrate and the second balancing substrate are arranged perpendicularly, a first surface of the first balancing substrate and / or a first surface of the second balancing substrate is used for printing microstrip lines, and a second surface of the first balancing substrate and / or a second surface of the second balancing substrate is used for printing slot lines.

[0013] In a further embodiment of the present invention, the planar spiral inductor structure is disposed on the first patch, and the second port microstrip line is disposed on the second patch; the first patch is disposed on the upper surface of the second patch, and the spiral center of the planar spiral inductor structure is connected to the second port microstrip line through a shorting pin.

[0014] Based on the same inventive concept, the present invention also provides an inhibition system, including a modeling module, an effect acquisition module, and an optimization module; wherein, The output of the modeling module is connected to the effect acquisition module, and is used to model the cross-band coupling interference suppression structure described above based on electromagnetic characteristics, and output model characteristic parameters to the effect acquisition module according to the cross-band coupling interference suppression structure. The effect acquisition module is connected to the optimization module, and outputs coupling interference parameters to the optimization module according to the model characteristic parameters; The optimization module is connected to the modeling module, and adjusts the structural parameters of the cross-band coupling interference suppression structure in the modeling module according to the coupling interference parameters.

[0015] Based on the same inventive concept, the present invention also provides a suppression method for the above-described suppression system, comprising the following steps: Construct a cross-band coupling interference suppression structure and obtain the structural parameters of the frequency-selective surface; Modeling is performed based on electromagnetic properties to obtain model characteristic parameters; Simulations were performed based on the model characteristic parameters to obtain coupling interference parameters that characterize the system's ability to suppress cross-band coupling interference. The software optimization solution is used to solve the coupling interference suppression effect based on the constraints of the structural parameters of the frequency-selective surface, and the maximum feasible solution is obtained. The structural parameters of the crossband coupling interference suppression structure are adjusted based on the maximum feasible solution.

[0016] This invention provides a cross-band coupling interference suppression structure, suppression system, and suppression method. The cross-band coupling interference suppression structure includes: a low-frequency antenna element, a high-frequency antenna element, a frequency selective surface, and a reflective layer. The low-frequency antenna is fixed at a first height position above the frequency selective surface for transmitting low-frequency signals. The high-frequency antenna element is fixed at a second height position below the frequency selective surface for transmitting high-frequency signals. The frequency selective surface reflects the low-frequency signals and transmits the high-frequency signals. The reflective layer is disposed below the low-frequency antenna element for reflecting the high-frequency signals. This invention enhances the radiation performance of the low-frequency antenna by incorporating a frequency selective surface capable of transmitting high-frequency signals and reflecting low-frequency signals within the cross-band structure, while maintaining electromagnetic transparency for the high-frequency antenna to avoid introducing additional insertion loss, thereby reducing cross-band coupling interference and improving the operational stability of the interference suppression structure. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the crossband coupling interference suppression structure in a preferred embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the cross-band coupling interference suppression structure in another preferred embodiment of the present invention.

[0020] Figure 3 This is a side view of the cross-band coupling interference suppression structure in this invention.

[0021] Figure 4 (a) is a schematic diagram of the microstrip line distribution on the upper surface of the low-frequency antenna element in this invention. Figure 4 (b) is a schematic diagram of the microstrip line distribution on the lower surface of the low-frequency antenna element.

[0022] Figure 5(a) is a schematic diagram of the microstrip line distribution of the first balancing substrate of the balancing support in this invention. Figure 5 (b) is a schematic diagram of the microstrip line distribution of the second balanced substrate.

[0023] Figure 6 This is a schematic diagram of the microstrip line distribution of the high-frequency antenna element in this invention.

[0024] Figure 7 (a) is a schematic diagram of the first substrate structure of the bandpass filter structure in this invention. Figure 7 (b) is a schematic diagram of the second substrate structure of the bandpass filter structure in this invention.

[0025] Figure 8 (a) is a top view of the planar spiral inductor structure in this invention. Figure 8 (b) is a three-dimensional structural diagram of the planar spiral inductor structure in this invention. Figure 8 (c) is the equivalent circuit diagram of the planar spiral inductor structure in this invention.

[0026] Figure 9 (a) is a schematic diagram of the structure of the first patch of the low-pass filter structure in this invention. Figure 9 (b) is a schematic diagram of the structure of the second patch of the low-pass filter structure in this invention.

[0027] Figure 10 This is a comparison diagram of the radiation patterns of the low-frequency antenna element and the high-frequency antenna element of the cross-band coupling interference suppression structure in this invention under different conditions.

[0028] Figure 11 This is an electric field distribution diagram of the low-frequency antenna element under different conditions in this invention.

[0029] Figure 12 This is the measured antenna radiation pattern when the cross-band coupling interference suppression structure of this invention is actually working.

[0030] Figure 13 (a) is a schematic diagram of the S-parameters of the low-frequency antenna element when the cross-band coupling interference suppression structure of the present invention is actually working. Figure 13 (b) is a schematic diagram of the S-parameters of the high-frequency antenna element when the cross-band coupling interference suppression structure of the present invention is actually working.

[0031] Figure 14 (a) in the diagram is a schematic diagram of the gain and bandwidth of the low-frequency antenna element in this invention. Figure 14 (b) is a schematic diagram of the gain and bandwidth of the high-frequency antenna element in this invention.

[0032] The labels in the attached diagram are as follows: 1L, low-frequency signal; 1H, high-frequency signal; 100, low-frequency antenna element; 110, top antenna layer; 111, square ring; 112, L-shaped support arm; 120, bottom coupling layer; 200, high-frequency antenna element; 300, frequency selective surface; 310, bandpass filter structure; 3101, first substrate; 3102, second substrate; 311, first microstrip end; 312, second microstrip end; 313, third microstrip end; 314, fourth microstrip end; 315, first resonant structure; 316, first microstrip connection line; 317, second microstrip connection line; 318, third microstrip connection line; 319, fourth microstrip connection line; 320, low-pass filter structure; 3201, first patch; 3202, second patch; 3203, shorting pin; 321, first planar spiral section; 322, second planar spiral section; 3 23. Third planar spiral section; 324. Fourth planar spiral section; 3241. First port microstrip line; 3242. Second port microstrip line; 3243. Planar spiral inductor structure; 3244. First open-circuit stub; 3245. Second open-circuit stub; 3246. First port; 3247. Second port; 325. Second resonant structure; 326. First spiral end; 327. Second spiral end; 328. Third spiral end; 329. Fourth spiral end; 330. Selective support substrate; 3051. Central coupling section; 3052. First high-impedance line; 3053. Second high-impedance line; 3054. Third high-impedance line; 3055. Fourth high-impedance line; 400. Reflective layer; 500. Balance support; 510. First balance substrate; 520. Second balance substrate; 600. Supporting nylon column; 700. Ground plane. Detailed Implementation

[0033] This invention provides a cross-band coupling interference suppression structure, suppression system, and suppression method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0034] In the implementation methods and claims, unless otherwise specified in the text, the terms "a," "an," "the," and "the" may also include plural forms. If the embodiments of the present invention involve descriptions of "first," "second," etc., such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0035] It should be further understood that the term "comprising" as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, "connected" or "coupled" as used herein can include wireless connections or wireless coupling. The term "and / or" as used herein includes all or any unit and all combinations of one or more associated listed items.

[0036] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0037] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0038] The inventors discovered that with the accelerated deployment of 5G networks, base station antenna design faces unprecedented challenges. Modern base stations need to simultaneously support multiple communication standards such as 2G / 3G / 4G / 5G, requiring antenna systems to operate efficiently across multiple frequency bands. The traditional solution is to design a separate antenna system for each frequency band, but this approach not only increases equipment size and cost but also results in a significant waste of space resources. Therefore, shared aperture multi-band antenna array technology has emerged, which integrates multiple antenna elements operating in different frequency bands within the same physical space, greatly improving space utilization and reducing system costs.

[0039] However, this compact integrated design also brings serious electromagnetic compatibility (EMC) problems. In dual-band or even multi-band shared aperture antenna systems, mutual interference between antenna elements of different frequency bands becomes a key factor restricting system performance. In particular, when low-frequency antennas (0.69-0.96 GHz) and high-frequency antennas (3.3-3.8 GHz) coexist in the same physical aperture, conventional isolation methods are often ineffective due to the significant difference in their operating frequencies. This interference mainly manifests in two forms: scattering interference and common-mode interference. Scattering interference occurs when the high-frequency antenna is operating; its radiated electromagnetic waves induce scattering currents on the low-frequency antenna. These scattering currents generate corresponding scattering fields on the low-frequency antenna, which in turn interfere with the normal operation of the high-frequency antenna. This interference causes distortion of the radiation direction of the high-frequency antenna, reduced gain, and worsened front-to-back ratio, severely affecting communication quality.

[0040] Common-mode interference occurs when low-frequency antennas are operating. The electromagnetic waves radiated by these antennas induce common-mode currents in the radiators and feed lines of high-frequency antennas. Since the operating frequency of high-frequency antennas is much higher than that of low-frequency antennas, these common-mode currents often resonate within the operating frequency band of the high-frequency antenna, generating strong radiation and interfering with the normal operation of the low-frequency antenna. This interference not only degrades the radiation performance of the low-frequency antenna but may also introduce additional intermodulation products, further worsening system performance.

[0041] Currently, researchers have proposed several methods to suppress these interferences. One common approach is to add electromagnetic shielding structures, such as metal partitions or absorbing materials, between antennas. However, this method increases the size and weight of the system, contradicting the original intention of the shared aperture design. Another approach is to employ a complex feed network design, adjusting the feed phase and amplitude to cancel out the interference. However, this method requires precise phase control, is highly sensitive to manufacturing tolerances, and is difficult to adapt to complex multi-band scenarios.

[0042] Frequency selective surface (FSS) technology offers a novel solution. A FSS is a two-dimensional periodic structure that can be designed to exhibit frequency selectivity, meaning it displays high transmittance for certain frequencies of electromagnetic waves and high reflectivity for others. However, traditional FSS designs often optimize performance for only a single frequency band, making it difficult to simultaneously meet the different requirements of high- and low-frequency antennas. Particularly in dual-band shared-aperture base station antennas, the FSS needs to satisfy two seemingly contradictory requirements: acting as a reflector for low-frequency antennas to enhance their radiation performance, while maintaining electromagnetic transparency for high-frequency antennas to avoid introducing additional insertion loss. Furthermore, existing FSS designs still have shortcomings in terms of angular stability, polarization insensitivity, and inter-element coupling control. When the angle or polarization of the incident wave changes, the frequency response of traditional FSS often shifts significantly, leading to system instability. In large-scale antenna arrays, this instability is further amplified, severely impacting the reliability of the entire base station antenna system.

[0043] Therefore, in order to solve the technical problems existing in the current communication antenna structure, such as Figure 1 As shown, the present invention provides a cross-band coupling interference suppression structure, comprising: a low-frequency antenna unit 100, a high-frequency antenna unit 200, a frequency selective surface 300, and a reflective layer 400; wherein, the low-frequency antenna is fixed at a first height position above the frequency selective surface 300 for transmitting a low-frequency signal 1L; the high-frequency antenna unit 200 is fixed at a second height position below the frequency selective surface 300 for transmitting a high-frequency signal 1H; the frequency selective surface 300 is used to reflect the low-frequency signal 1L and transmit the high-frequency signal 1H; the reflective layer 400 is disposed below the low-frequency antenna unit 100 for reflecting the high-frequency signal 1H.

[0044] Specifically, the low-frequency antenna unit 100 is located above the frequency selective surface 300. The low-frequency signal 1L emitted by this unit is reflected by the frequency selective surface 300, and the radiated energy of the low-frequency signal 1L is emitted into the upper space. The high-frequency antenna unit 200 is disposed between the frequency selective surface 300 and the lowermost reflective layer 400. The high-frequency signal 1H emitted by the high-frequency antenna unit 200 is reflected upwards by the reflective layer 400, forming directional radiation, increasing gain and suppressing back lobes. Simultaneously, since the frequency selective surface 300 exhibits transmission characteristics for the high-frequency signal 1H, it penetrates the frequency selective surface 300 and is emitted into the upper space. In one implementation, the low-frequency antenna unit 100 operates in the 0.69-0.96 GHz frequency band, and the high-frequency antenna unit 200 operates in the 3.3-3.8 GHz frequency band. The frequency selective surface 300 acts as a reflector in the low-frequency band and exhibits electromagnetic transparency in the high-frequency band.

[0045] The low-frequency antenna unit 100 includes a top antenna layer 110, a dielectric substrate (not shown in the figure), and a bottom coupling layer 120. The dielectric substrate can be an FR4 substrate. Please refer to [further details needed]. Figure 1 and Figure 4 The top antenna layer 110 mainly consists of two vertical square ring antennas 111 with L-shaped arms 112. These antennas are printed on the top of the FR4 substrate, and each square ring 111 has six additional L-shaped arms 112 inside to increase bandwidth and reduce uplink radiation distortion. Correspondingly, the bottom coupling layer 120 is located on the lower surface of the dielectric, and additional coupling lines are provided on the bottom coupling layer 120 to slightly extend the bandwidth. The structure of the high-frequency antenna unit 200 is as follows: Figure 6 As shown, it includes square antennas perpendicular to each other. In some preferred embodiments, at least one supporting nylon column 600 can be fixedly disposed on the high-frequency antenna unit 200 and the frequency selective surface 300. The bottom end of the supporting nylon column 600 is connected to the reflective layer 400 to provide support for the antennas and the frequency selective surface 300 above, preventing deformation or breakage of their surfaces due to gravity. All patches are printed on an FR4 substrate with a dielectric constant of 4.4 and a thickness of 0.762 mm. Thus, by allowing the high- and low-frequency antennas to share the same aperture and spatially multiplexing through the frequency selective surface 300, the overall size and profile height of the antenna array are significantly reduced, solving the problem of excessive size of traditional dual-frequency antennas. At the same time, it effectively isolates high- and low-frequency signals, avoids mutual coupling interference between antennas, and ensures the radiation performance of each frequency band.

[0046] In some preferred embodiments, please refer to the following: Figure 1 , Figure 2 , Figure 3 and Figure 5The cross-band coupling interference suppression structure also includes a balancing support 500; one end of the balancing support 500 is perpendicularly connected to the frequency selection surface 300, and the other end of the balancing support 500 is perpendicularly connected to the low-frequency antenna unit 100; it includes a first balancing substrate 510 and a second balancing substrate 520, the first balancing substrate 510 and the second balancing substrate 520 are vertically arranged, the first surface of the first balancing substrate 510 and / or the first surface of the second balancing substrate 520 is used for printing microstrip lines, and the second surface of the first balancing substrate 510 and / or the second surface of the second balancing substrate 520 is used for printing slot lines. That is, the first height between the low-frequency antenna unit 100 and the frequency selection unit is determined by the length of the balancing support 500, and its specific length can be set according to the coupling situation in actual use. In order to construct a balun, the first balancing substrate 510 and the second balancing substrate 520 are two vertically placed substrates, the dielectric constant of the substrates is 3, the loss tangent is 0.003, the thickness is 1.52mm, and the substrates are placed perpendicular to each other. The first balancing substrate 510 and the second balancing substrate 520 have microstrip lines printed on their front sides and groove lines printed on their back sides. The grooves of the first balancing substrate 510 and the second balancing substrate 520 are arranged in an alternating manner so as to facilitate assembly and fixation during actual use.

[0047] Further, please refer to Figure 2 The frequency selective surface 300 includes a bandpass filter structure 310, a low-pass filter structure 320, and a selective support substrate 330. The bandpass filter structure 310 and the low-pass filter structure 320 are disposed on the upper surface of the selective support substrate 330, with the low-pass filter structure 320 located at the edge of the selective support substrate 330. Specifically, the frequency selective surface 300 consists of a 3.3-3.8 GHz bandpass filter located at the center and four 0.69-0.96 GHz low-pass filters distributed at the corners. This layout not only achieves independent control of high and low frequency bands but also ensures the uniformity of electromagnetic field distribution, avoiding unwanted hotspot effects when operating at high frequencies. By proposing an innovative topology design, the frequency selective surface 300 cleverly integrates bandpass and low-pass characteristics on the same plane. Preferably, both the bandpass filter and the low-pass filter are printed on an FR4 substrate.

[0048] Among them, such as Figure 7As shown, the bandpass filter structure 310 includes a plurality of bandpass filter units, each including: a first microstrip end 311, a second microstrip end 312, a third microstrip end 313, a fourth microstrip end 314, a first resonant structure 315, a first microstrip connecting line 316, a second microstrip connecting line 317, a third microstrip connecting line 318, and a fourth microstrip connecting line 319. The first resonant structure 315 is located at the center of the bandpass filter unit and is connected clockwise to the first microstrip connecting line 316, the second microstrip connecting line 317, the third microstrip connecting line 318, and the fourth microstrip connecting line 319. The first microstrip connecting line 316 is connected to the first microstrip end 311, the second microstrip connecting line 317 is connected to the second microstrip end 312, the third microstrip connecting line 318 is connected to the third microstrip end 313, and the fourth microstrip connecting line 319 is connected to the fourth microstrip end 314.

[0049] Please refer to the corresponding documents as well. Figure 2 , Figure 8 and Figure 9 The bandpass filter includes a first substrate 3101 and a second substrate 3102 that overlap each other. The first substrate 3101 is provided with a structure including a first microstrip end 311, a second microstrip end 312, a third microstrip end 313, a fourth microstrip end 314, a first resonant structure 315, a first microstrip connecting line 316, a second microstrip connecting line 317, a third microstrip connecting line 318, and a fourth microstrip connecting line 319. The second substrate 3102 has end-thickening structures with the same shape as each microstrip end at its four corners, corresponding to the first microstrip end 311, the second microstrip end 312, the third microstrip end 313, and the fourth microstrip end 314. The bandpass filter adopts an improved stepped-impedance resonator (SIR) structure, and achieves high transmittance in the 3.3-3.8 GHz frequency band by precisely controlling the geometric parameters of the microstrip line length around the central patch. More importantly, the design maintains stable transmission performance across an incident angle range of 0° to 60°, with a transmission coefficient higher than -0.5 dB for both TM and TE waves, ensuring consistent performance of the high-frequency unit at different scanning angles.

[0050] In some preferred embodiments, the low-pass filter structure 320 includes four low-pass filter units, each of which is disposed at one of the four corners of the frequency support substrate. Each low-pass filter unit includes a first planar spiral portion 321, a second planar spiral portion 322, a third planar spiral portion 323, a fourth planar spiral portion 324, a second resonant structure 325, a first spiral end portion 326, a second spiral end portion 327, a third spiral end portion 328, and a fourth spiral end portion 329. The second resonant structure 325 is located at the center of the low-pass filter unit and is connected to the first planar spiral portion 321, the second planar spiral portion 322, the third planar spiral portion 323, and the fourth planar spiral portion 324 in a clockwise direction. The first planar spiral portion 321 is connected to the first spiral end portion 326, the second planar spiral portion 322 is connected to the second spiral end portion 327, the third planar spiral portion 323 is connected to the third spiral end portion 328, and the fourth planar spiral portion 324 is connected to the fourth spiral end portion 329.

[0051] The low-pass filter employs an innovative design combining a planar spiral inductor and microstrip lines. The planar spiral inductor provides a high inductance value, lowering the cutoff frequency, while the microstrip lines extending at both ends provide additional capacitance, further improving low-frequency reflection characteristics. Particularly noteworthy is the vertical connection between the top and bottom metal layers, forming a three-dimensional current path through metal pins, significantly improving low-frequency reflection efficiency while maintaining structural compactness. The planar spiral section includes: a first-port microstrip line 3241, a second-port microstrip line 3242, a planar spiral inductor structure 3243, a first open-circuit stub 3244, and a second open-circuit stub 3245; wherein, the input terminal of the planar spiral inductor structure 3243 is connected to the first-port microstrip line 3241, and the spiral center of the planar spiral inductor structure 3243 is connected to the second-port microstrip line 3242; the second-port microstrip line 3242 is collinear with the first-port microstrip line 3241; the first open-circuit stub 3244 is connected to the first-port microstrip line 3241, and the second open-circuit stub 3245 is connected to the second-port microstrip line 3242.

[0052] A ground plane 700 is disposed below the antenna of the planar helical section. The ground plane 700 can be any metallic conductor, such as a metal plate, metal shell, or PCB copper foil, to influence and improve the electromagnetic characteristics of the antenna. The planar helical inductor structure 3243, the first open-circuit branch 3244, and the second open-circuit branch 3245 form a helical inductor structure. The first planar helical section 321, the second planar helical section 322, the third planar helical section 323, and the fourth planar helical section 324 in each low-pass filter unit are composed of a planar helical inductor and microstrip lines extending from both ends. The width of the first port microstrip line 3241 and the second port microstrip line 3242 are the same, and they are collinear on the horizontal plane. The input end of the first port microstrip line 3241 is bent downward in the vertical direction to form a first port 3246 for receiving external signals. The output end of the second port microstrip line 3242 is bent downward in the vertical direction to form a second port 3247 for outputting signals to the outside. In some preferred embodiments, the planar spiral inductor structure 3243 is disposed on the first patch 3201, and the second port microstrip line 3242 is disposed on the second patch 3202; the first patch 3201 is disposed on the upper surface of the second patch 3202, and the spiral center of the planar spiral inductor structure 3243 is connected to the second port microstrip line 3242 through a shorting pin 3203. That is, the low-pass filter includes two overlapping patches, a first patch 3201 and a second patch 3202. A first-port microstrip line 3241, a planar spiral inductor structure 3243, and a first open-circuit stub 3244 are disposed on the upper patch 3201, and a second open-circuit stub 3245 and a second-port microstrip line 3242 are disposed on the lower patch 3202. When the first patch 3201 and the second patch 3202 are attached, the spiral center of the planar spiral inductor structure 3243 and one end of the second-port microstrip line 3242 overlap. Thus, the top-layer planar spiral inductor is connected to the metal second-port microstrip line 3242, which serves as the bottom-layer microstrip line, via the spiral center of the planar spiral inductor structure 3243 and a shorting pin 3203 passing through the dielectric. The performance of this low-pass filter can be directly measured in simulation software, such as... Figure 8 As shown in (b) above. Simultaneously, the equivalent circuit model of this low-pass filter is performed as follows: Figure 8 As shown in (c). Since the FR4 dielectric in the double-layer surface mount can be considered as an additional capacitor, because the double-layer surface mount design adds additional capacitance to the spiral inductor, and the microstrip lines extending at both ends are equivalent to capacitors. L'0=3.873 nH, C'0=0.65 pF, C'1=0.815 pF, C'2=0.725 pF.

[0053] in, Figure 9 In the diagram, (a) represents the first patch 3201 located on the top layer of the medium. Figure 9(b) in the diagram represents the second patch 3202 located on the bottom layer of the dielectric. Due to the stepped impedance filter structure, by precisely controlling the geometric parameter FS3 of the microstrip line length around the central patch, the frequency selective surface 300 exhibits electromagnetic transparency to the high-frequency band (3.3-3.8 GHz). Furthermore, a low-pass filter composed of a planar spiral inductor and an open-circuit microstrip line is subsequently designed on the microstrip line around the central patch. Therefore, strong coupling current will pass through at low frequencies, resulting in reflectivity to the low-frequency band (0.69-0.96 GHz). This structure retains the bandpass characteristics of the frequency selective surface 300 element in the 3.3-3.8 GHz range. Thus, it ultimately achieves the effect of acting as a reflector for low-frequency antennas (0.69-0.96 GHz) and achieving electromagnetic transparency for high-frequency antennas (3.3-3.8 GHz).

[0054] Furthermore, please refer to the following: Figure 7 and Figure 9 The first resonant structure 315 and / or the second resonant structure 325 are complementary split-ring resonators (CSRR). The CSRR includes a central coupling section 3051, a first high-impedance line 3052, a second high-impedance line 3053, a third high-impedance line 3054, and a fourth high-impedance line 3055, wherein the first high-impedance line 3052, the second high-impedance line 3053, the third high-impedance line 3054, and the fourth high-impedance line 3055 are respectively connected to the central coupling section 3051. By etching the complementary split-ring resonator structure onto the ground plane or conductor layer of the microstrip line or coplanar waveguide, a negative equivalent dielectric constant effect can be effectively generated near its resonant frequency by the time-varying electric field in the transmission line, thus equivalent to a parallel LC resonant circuit. The main function of this structure is to achieve frequency blocking of the signal by introducing a controllable transmission zero, thereby constructing a band-stop or band-pass response with steep cutoff characteristics. It possesses subwavelength characteristics, and its physical size is much smaller than the operating wavelength, enabling miniaturized filter design, greatly reducing the circuit board area, and significantly improving the filter's frequency selectivity and out-of-band rejection capability. Furthermore, its resonant frequency can be precisely controlled by adjusting the geometric parameters of the ring, making it easy to integrate with other planar circuits.

[0055] In some preferred embodiments, the preferred structural parameters of the frequency selective surface 300 include: H0=18mm, H1=30mm, H2=115mm, W0=240mm, W1=132mm, L0=65mm, L1=44.5mm, L2=13mm, L3=49mm, L4=20mm, L5=16.68mm, L6=5mm, L7=7mm, L8=9.41mm, L9=16.8mm, FB0=8.15mm, FB1=10mm, FB2=25.6mm, FB3=24.47mm, FB4=15mm, FB5=12.95mm, FB6=15mm, FB7=4.2mm, FB8 ...10mm, FB3=24.47mm, FB4=15mm, FB5=12.95mm, FB6=15mm, FB7=4.2mm, FB8=10mm, FB2=10mm, FB3=10mm, FB4=10mm, FB5=10mm, FB6=10mm, FB7=10mm, FB8=10mm, FB2=10mm, FB3=10mm, FB4=10mm, FB5=10mm, FB6=10mm, FB7=10mm, FB8=10mm, FB2=10mm, FB2=10mm, FB2=10mm, FB3=10mm, FB4=10mm, FB5=10mm, FB6=1 =25.3mm, FB9=25mm, G0=3.5mm, G1=3mm, Wh0=1mm, Wh1=2mm, FS0=30mm, FS1=5.5mm, FS2=3mm, FS3=9.7mm, FS4=5mm, FS5=8mm, FS6=5.4mm, FS7=4.6mm, FS8=7.6mm, FSL0=2.5mm, FSL1=5.9mm, FSL2=2mm, FSL3=2.45mm, FSL4=3.1mm, FSL5=4.4125mm, FSL6=4mm, WFSL0=1.5mm, WFSL1=0.7mm, WFSL2=0.3mm.

[0056] This invention provides a cross-band coupling interference suppression structure. By incorporating a frequency selective surface 300 within the cross-band structure that transmits high-frequency signals 1H and reflects low-frequency signals 1L, the radiation performance of the low-frequency antenna 1L is enhanced by reflecting the low-frequency signal 1L. Simultaneously, electromagnetic transparency is maintained for the high-frequency antenna, avoiding the introduction of additional insertion loss, reducing cross-band coupling interference, and improving the operational stability of the interference suppression structure. Regarding material selection, this invention fully considers the balance between cost and performance. All frequency selective surface 300 components are printed on an FR4 substrate. FR4 substrate is inexpensive, easy to process, and has a dielectric constant of 4.4, which facilitates a compact structural design. The thickness of the FR4 substrate is precisely optimized to balance electrical performance and mechanical strength. Through electromagnetic simulation and experimental verification, the optimal thickness of the FR4 substrate is 1mm, ensuring sufficient mechanical rigidity without significantly affecting electromagnetic performance. In terms of practical antenna system integration, this invention proposes a precise height control mechanism. The spacing between the low-frequency antenna element 100, the frequency selective surface 300, and the high-frequency antenna element 200 is systematically optimized to maximize isolation while maintaining radiation efficiency. Specifically, the spacing between the frequency selective surface 300 and the low-frequency antenna element 100 is set to one-quarter wavelength of the center frequency of the low-frequency band. This utilizes the principle of electromagnetic wave interference to further enhance the reflection effect of the low-frequency band. The spacing between the frequency selective surface 300 layer and the high-frequency antenna element 200 is optimized according to the characteristics of the high-frequency band to ensure that the high-frequency signal 1H can pass through the frequency selective surface 300 layer without loss.

[0057] like Figure 10 As shown, Figure 10 (a) and Figure 10 (b) compares the radiation patterns of the low-frequency antenna element 100. Figure 10 (c) and (d) in the diagram compare the radiation patterns of the high-frequency antenna element 200 under two different conditions: with a metallic ground plane 700 and with a frequency-selective surface 300 reflector. Observations show that the radiation pattern remains essentially unchanged, confirming the applicability of the proposed frequency-selective surface 300.

[0058] like Figure 11 As shown, Figure 11 (a) shows the electric field distribution of the low-frequency antenna element 100 located on the metal reflector layer 400. Figure 11 (b) shows the electric field distribution of the same low-frequency antenna element 100, but this time it is located on the metallic reflective layer 400 along with four high-frequency antenna elements 200. Due to the presence of common-mode interference, we can see that the radiation pattern of the low-frequency antenna element 100 is significantly distorted. Figure 11Figure (c) shows the electric field distribution of the low-frequency antenna element 100 after the addition of the frequency selective surface 300 layer, and again, four high-frequency antenna elements 200 are present on the metallic reflective layer 400. Clearly, common-mode interference is greatly suppressed, demonstrating the excellent performance of the frequency selective surface 300.

[0059] like Figure 12 As shown, Figure 12 (a) in the diagram shows the simulated and measured radiation pattern of the low-frequency antenna element 100 at 0.69 GHz. Figure 12 (b) shows the simulated and measured radiation pattern of the low-frequency antenna element 100 at 0.8 GHz. Figure 12 (c) in the diagram shows the simulated and measured radiation pattern of the low-frequency antenna element 100 at 0.96 GHz, and Figure 12 In diagram (d), the simulated and measured radiation patterns of the high-frequency subarray 1 in the high-frequency antenna element 200 at 3.3 GHz, 3.5 GHz, and 3.8 GHz are shown. Figure 12 In the diagram (e), the simulated and measured radiation pattern of the high-frequency subarray 1 in the high-frequency antenna element 200 at 3.5 GHz is shown. Figure 12 In diagram (f), the simulated and measured radiation pattern of the high-frequency subarray 1 in the high-frequency antenna element 200 at 3.8 GHz is shown. Figure 12 The simulation results match the measurement data, and the low-frequency antenna element 100 and the high-frequency antenna element 200 exhibit very stable radiation patterns throughout the entire bandwidth.

[0060] like Figure 13 As shown in (a), the return loss of the low-frequency antenna element 100 is less than -10 dB in the target frequency range of 0.69 GHz to 0.96 GHz, and the isolation exceeds 25 dB. Similarly, as Figure 13 As shown in (b), the high-frequency antenna element 200 also has a return loss of less than -10 dB in the frequency range of 3.3 GHz to 3.8 GHz, and an isolation of better than 25 dB.

[0061] like Figure 14 As shown in (a), the gain of the low-frequency antenna element 100 is 6.8 ± 0.3 dBi, and the HPBW is 68 ± 6°; Figure 14 As shown in (b), the gain of the high-frequency subarray 1 is 8.8 ± 0.8 dBi, and the HPBW is 50 ± 4°. Experimental results demonstrate that the designed dual-frequency shared aperture antenna array exhibits excellent radiation performance in both low and high frequency bands, confirming the effectiveness of the proposed frequency-selective surface 300-element technique in minimizing common-mode interference.

[0062] Based on the same inventive concept, the present invention also provides a suppression system, including a modeling module, an effect acquisition module, and an optimization module; wherein, the output end of the modeling module is connected to the effect acquisition module, and is used to model the aforementioned cross-band coupling interference suppression structure based on electromagnetic characteristics, and output model characteristic parameters to the effect acquisition module according to the cross-band coupling interference suppression structure; the effect acquisition module is connected to the optimization module, and outputs coupling interference parameters to the optimization module according to the model characteristic parameters; the optimization module is connected to the modeling module, and adjusts the structural parameters of the cross-band coupling interference suppression structure in the modeling module according to the coupling interference parameters.

[0063] Based on the above embodiments, the present invention also provides an apparatus for suppressing cross-band coupling interference in a dual-band shared aperture base station antenna using a frequency selective surface 300. The apparatus includes: a construction module for constructing a dual-band shared aperture base station antenna system, the system including a low-frequency antenna element 100, a high-frequency antenna element 200, and a frequency selective surface 300; a modeling module for modeling the electromagnetic characteristics of the dual-band shared aperture base station antenna system to obtain the coupling relationship between the low-frequency antenna element 100 and the frequency selective surface 300, and the electromagnetic transparency characteristics between the high-frequency antenna element 200 and the frequency selective surface 300; an effect acquisition module for obtaining the effect of the system in suppressing cross-band coupling interference based on the coupling relationship and electromagnetic transparency characteristics; and an optimization module for optimizing the structural parameters of the frequency selective surface 300 through electromagnetic simulation and experimental verification, so that the system achieves optimal isolation and radiation performance in the target frequency band. Specific details are as described in the embodiments of the cross-band coupling interference suppression structure, and will not be repeated here.

[0064] Based on the same inventive concept, the present invention also provides a suppression method for the above-described suppression system, comprising the following steps: S100. Construct a cross-band coupling interference suppression structure and obtain the structural parameters of frequency selection surface 300. S200. Modeling is performed based on electromagnetic properties to obtain model characteristic parameters; S300. Based on the model characteristic parameters, simulation is performed to obtain coupling interference parameters that characterize the system's ability to suppress cross-band coupling interference. The coupling interference suppression effect of S400 and frequency-selective surface 300 is optimized by software to obtain the maximum feasible solution. S500: Adjust the structural parameters of the cross-band coupling interference suppression structure according to the maximum feasible solution.

[0065] This invention provides a cross-band coupling interference suppression structure, suppression system, and suppression method. The cross-band coupling interference suppression structure includes: a low-frequency antenna element 100, a high-frequency antenna element 200, a frequency selective surface 300, and a reflective layer 400. The low-frequency antenna is fixed at a first height position above the frequency selective surface 300 and is used to transmit a low-frequency signal 1L. The high-frequency antenna element 200 is fixed at a second height position below the frequency selective surface 300 and is used to transmit a high-frequency signal 1H. The frequency selective surface 300 reflects the low-frequency signal 1L and transmits the high-frequency signal 1H. The reflective layer 400 is disposed below the low-frequency antenna element 100 and is used to reflect the high-frequency signal 1H. This invention enhances the radiation performance of the low-frequency antenna by providing a frequency selective surface 300 in the cross-band structure that can transmit the high-frequency signal 1H and reflect the low-frequency signal 1L, while maintaining electromagnetic transparency for the high-frequency antenna to avoid introducing additional insertion loss, reducing cross-band coupling interference, and improving the operational stability of the interference suppression structure.

[0066] In terms of material selection, this invention fully considers the balance between cost and performance. All frequency-selective surface 300 elements are printed on an FR4 substrate. This material is not only inexpensive and easy to process, but also has a suitable dielectric constant. For example, an FR4 substrate with a dielectric constant of 4.4 is preferably used, which is beneficial for achieving a compact structural design. The thickness of the FR4 substrate has been precisely optimized to balance electrical performance and mechanical strength. Through electromagnetic simulation and experimental verification, we have determined an optimal thickness of 1 mm, which ensures sufficient mechanical rigidity without significantly affecting electromagnetic performance.

[0067] In practical antenna system integration, this invention proposes a precise height control mechanism. The spacing between the low-frequency antenna element 100, the frequency selective surface 300, and the high-frequency antenna element 200 is systematically optimized to maximize isolation while maintaining radiation efficiency. Specifically, the spacing between the frequency selective surface 300 and the low-frequency antenna element 100 is set to a quarter wavelength of the low-frequency center frequency, which utilizes the principle of electromagnetic wave interference to further enhance the reflection effect in the low-frequency band. The spacing between the frequency selective surface 300 layer and the high-frequency antenna element 200 is optimized according to the characteristics of the high-frequency band to ensure that the high-frequency signal 1H can pass through the frequency selective surface 300 layer without loss.

[0068] This invention provides a method for suppressing cross-band coupling interference in a dual-band shared aperture base station antenna using a frequency selective surface 300. The method includes: constructing a dual-band shared aperture base station antenna system, the system comprising a low-frequency antenna element 100, a high-frequency antenna element 200, and a frequency selective surface 300; modeling the electromagnetic characteristics of the dual-band shared aperture base station antenna system to obtain the coupling relationship between the low-frequency antenna element 100 and the frequency selective surface 300, and the electromagnetic transparency characteristics between the high-frequency antenna element 200 and the frequency selective surface 300; firstly, determining the operating frequency band of the low-frequency antenna element 100 as 0.69-0.96 GHz, determining the operating frequency band of the high-frequency antenna element 200 as 3.3-3.8 GHz, and determining the structure of the frequency selective surface 300 as consisting of a 3.3-3.8 GHz bandpass filter and four 0.69-0.96 GHz bandpass filters. The composition of the GHz low-pass filter was determined, and the material parameters of the frequency selective surface 300 were determined: dielectric constant εr = 4.4, FR4 substrate with a thickness of 1 mm. A three-dimensional model of the frequency selective surface 300 structure was then established, including a band-stop filter and a low-pass filter. Periodic boundary conditions were set to simulate the periodic structural characteristics of the frequency selective surface 300. Appropriate meshing was set to ensure simulation accuracy. First, for low frequencies (0.69-0.96 GHz), the reflection characteristics R_FSS of the frequency selective surface 300 were calculated. The reflection coefficient S11 of the frequency selective surface 300 in this frequency band was calculated using electromagnetic simulation software. Then, the reflection performance of the frequency selective surface 300 in this frequency band was verified to ensure high reflectivity. For high frequencies (3.3-3.8 GHz), the transmission characteristics T_FSS of the frequency selective surface 300 were first calculated. The transmission coefficient S21 of the frequency selective surface 300 in this frequency band was calculated using simulation software. Finally, the transmission performance of the frequency selective surface 300 in this frequency band was verified to ensure that the transmission coefficient is higher than -0.5 dB.

[0069] The coupling between the low-frequency antenna element 100 and the frequency selective surface 300 originates from the interaction of electromagnetic fields. When the low-frequency antenna element 100 is working, the electromagnetic waves it radiates interact with the frequency selective surface 300, resulting in reflection.

[0070] The coupling coefficient between the low-frequency antenna element 100 and the frequency selective surface 300 was obtained through electromagnetic simulation. The coupling relationship is expressed as follows:

[0071] Where E_LB represents the radiation characteristics of the low-frequency antenna element 100, and R_FSS represents the reflection characteristics of the frequency selective surface 300, obtained through electromagnetic simulation calculations. The frequency selective surface 300 exhibits high reflection characteristics in the low-frequency band, therefore R_FSS is close to 1, resulting in a relatively large coupling coefficient C_LB. However, this coupling is required by the design to enhance the radiation performance of the low-frequency antenna element 100. C_LB represents the coupling coefficient between the low-frequency antenna element 100 and the frequency selective surface 300.

[0072] The electromagnetic transparency between the high-frequency antenna element 200 and the frequency selective surface 300 stems from the transmission characteristics of the frequency selective surface 300 in the high-frequency band. When the high-frequency antenna element 200 is operating, the electromagnetic waves it radiates pass through the frequency selective surface 300, which exhibits high transmission characteristics in that frequency band; therefore, the transmission coefficient T_HB is close to 1. The transmission coefficient between the high-frequency antenna element 200 and the frequency selective surface 300 is obtained through electromagnetic simulation, and the electromagnetic transparency characteristic is expressed as:

[0073] Where E_HB represents the radiation characteristics of the high-frequency antenna element 200, and T_FSS represents the transmission characteristics of the frequency selective surface 300, obtained through electromagnetic simulation calculations. T_FSS is the transmission characteristic frequency of the frequency selective surface 300, and T_HB represents the transmission coefficient between the high-frequency antenna element 200 and the frequency selective surface 300. The selective surface 300 exhibits high transmission characteristics in the high-frequency band, therefore T_FSS is close to 1, resulting in a large transmission coefficient T_HB, meaning that the signal from the high-frequency antenna element 200 can pass through the frequency selective surface 300 layer without loss.

[0074] The performance of the frequency selective surface 300 at different incident angles, such as 0° to 60°, was verified by electromagnetic simulation. The transmission coefficients of TM and TE waves were compared to ensure stable performance over a wide angle range. An equivalent circuit model (ECM) of the low-pass filter was constructed and verified in ADS software. The structural parameters of the frequency selective surface 300 were adjusted based on the simulation results. A prototype of the frequency selective surface 300 was fabricated and experimentally tested to verify the simulation results.

[0075] The frequency selective surface 300, as a two-dimensional periodic structure, has electromagnetic properties determined by its geometry and material. According to the documentation, the frequency selective surface 300 exhibits different characteristics in different frequency bands: its low-pass filter characteristics for the low-frequency band (0.69-0.96 GHz) can be expressed as follows: Where L is the equivalent inductance and C is the equivalent capacitance. In low-pass filter design, the planar spiral inductor provides a high inductance value, and the microstrip lines extending at both ends provide additional capacitance. The bandpass filter characteristics for the high-frequency band 3.3-3.8 GHz can be expressed as: Among them, the bandpass filter adopts a stepped impedance filter, and high transmittance in a specific frequency band is achieved by precisely controlling the geometric parameter FS3 of the microstrip line length around the center patch.

[0076] Subsequent electromagnetic simulations verified the transmission performance of the frequency-selective surface 300 in the high-frequency band (3.3-3.8 GHz). The results showed that the proposed bandpass filter exhibited transmission coefficients higher than -0.5 dB for both TM and TE waves with incident angles ranging from 0° to 60°, ensuring consistent performance of the high-frequency unit across different scanning angles. Simultaneously, the performance of the low-pass filter was verified in ADS software using H_FSS direct measurement (DM) and equivalent circuit modeling. This modeling and verification process ensures that the frequency-selective surface 300 provides high reflectivity in the low-frequency band and high transmission in the high-frequency band, effectively suppressing cross-band coupling interference.

[0077] This invention discloses a cross-band coupling interference suppression structure, suppression system, and suppression method, which have the following beneficial effects: Compared with existing technologies, this invention provides a method and related equipment for suppressing cross-band coupling interference in dual-band shared aperture base station antennas using a frequency selective surface. In the method provided by this invention, a dual-band shared aperture base station antenna system is constructed, comprising a low-frequency antenna element, a high-frequency antenna element, and a frequency selective surface. Then, the electromagnetic characteristics of the dual-band shared aperture base station antenna system are modeled to obtain the coupling relationship between the low-frequency antenna element and the frequency selective surface, and the electromagnetic transparency characteristics between the high-frequency antenna element and the frequency selective surface. Subsequently, based on the coupling relationship and electromagnetic transparency characteristics, the effect of the system in suppressing cross-band coupling interference is obtained. Finally, through electromagnetic simulation and experimental verification, the structural parameters of the frequency selective surface are optimized, enabling the system to achieve optimal isolation and radiation performance within the target frequency band.

[0078] This invention provides a method for effectively suppressing cross-band coupling interference in a dual-band shared aperture base station antenna system. By designing a frequency selective surface structure, the frequency selective surface has a reflective effect on low-frequency elements and electromagnetic transparency to high-frequency elements, thereby effectively suppressing cross-band coupling interference and improving the radiation performance and isolation of the antenna system.

[0079] This invention offers technical advantages in several aspects, including electromagnetic performance, manufacturing cost, system integration, and environmental adaptability. In terms of performance, through the precise design of the frequency selective surface, isolation exceeding 25 dB between two frequency bands is successfully achieved, far exceeding the industry standard requirement of 15-20 dB. Simultaneously, the insertion loss of high-frequency signals from the frequency selective surface is controlled to within 0.5 dB, which is crucial for maintaining the overall efficiency of the system. Regarding radiation characteristics, the presence of the frequency selective surface barely alters the antenna's radiation pattern shape, maintaining an aspect ratio above 20 dB, thus ensuring the quality and efficiency of signal coverage.

[0080] From a manufacturing cost perspective, this invention uses standard PCB processes and conventional materials, requiring no special equipment or expensive materials. The cost of a single frequency selective surface unit is less than one-third of that of traditional electromagnetic shielding solutions. More importantly, because the frequency selective surface simultaneously achieves isolation between high and low frequency bands and reflection in the low-frequency band, the entire antenna system eliminates the need for additional reflectors and isolation structures, further reducing material costs and assembly complexity. Under large-scale production conditions, the total cost of a dual-frequency antenna array using this invention can be reduced by more than 30% compared to traditional solutions.

[0081] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A cross-band coupling interference suppression structure, characterized in that, include: Low-frequency antenna element, high-frequency antenna element, frequency selective surface and reflective layer; among which, The low-frequency antenna is fixed at a first height position above the frequency selection surface and is used to transmit low-frequency signals. The high-frequency antenna unit is fixed at a second height position below the frequency selective surface and is used to transmit high-frequency signals. The frequency selective surface is used to reflect the low-frequency signal and transmit the high-frequency signal; The reflective layer is disposed below the low-frequency antenna unit and is used to reflect high-frequency signals.

2. The cross-band coupling interference suppression structure according to claim 1, characterized in that, The frequency selection surface includes a bandpass filter structure, a low-pass filter structure, and a selection support substrate. The bandpass filter structure and the low-pass filter structure are disposed on the upper surface of the selection support substrate, and the low-pass filter structure is disposed at the edge of the selection support substrate.

3. The cross-band coupling interference suppression structure according to claim 2, characterized in that, The bandpass filter structure includes several bandpass filter units, each comprising: a first microstrip end, a second microstrip end, a third microstrip end, a fourth microstrip end, a first resonant structure, a first microstrip connecting line, a second microstrip connecting line, a third microstrip connecting line, and a fourth microstrip connecting line; wherein... The first resonant structure is located at the center of the bandpass filter unit, and the first resonant structure is connected to the first microstrip connection line, the second microstrip connection line, the third microstrip connection line and the fourth microstrip connection line in a clockwise direction. The first microstrip connecting line is connected to the first microstrip end, the second microstrip connecting line is connected to the second microstrip end, the third microstrip connecting line is connected to the third microstrip end, and the fourth microstrip connecting line is connected to the fourth microstrip end.

4. The cross-band coupling interference suppression structure according to claim 2, characterized in that, The low-pass filter structure includes four low-pass filter units, each of which is respectively located at the four corners of the frequency support substrate. The low-pass filter unit includes a first planar spiral section, a second planar spiral section, a third planar spiral section, a fourth planar spiral section, a second resonant structure, a first spiral end, a second spiral end, a third spiral end, and a fourth spiral end; wherein, the second resonant structure is located at the center of the low-pass filter unit and is connected to the first planar spiral section, the second planar spiral section, the third planar spiral section, and the fourth planar spiral section in a clockwise direction respectively; The first planar spiral portion is connected to the first spiral end, the second planar spiral portion is connected to the second spiral end, the third planar spiral portion is connected to the third spiral end, and the fourth planar spiral portion is connected to the fourth spiral end.

5. The cross-band coupling interference suppression structure according to claim 3 or 4, characterized in that, The first resonant structure and / or the second resonant structure are complementary open-loop resonant structures; The complementary open-loop resonant structure includes: a central coupling part, a first high-impedance line, a second high-impedance line, a third high-impedance line, and a fourth high-impedance line, wherein the first high-impedance line, the second high-impedance line, the third high-impedance line, and the fourth high-impedance line are respectively connected to the central coupling part.

6. The cross-band coupling interference suppression structure according to claim 4, characterized in that, The planar helical section includes: a first-port microstrip line, a second-port microstrip line, a planar helical inductor structure, a first open-circuit stub, and a second open-circuit stub; wherein, The input terminal of the planar spiral inductor structure is connected to the first port microstrip line, and the spiral center of the planar spiral inductor structure is connected to the second port microstrip line. The second port microstrip line is collinear with the first port microstrip line; The first open-circuit stub is connected to the first port microstrip line, and the second open-circuit stub is connected to the second port microstrip line.

7. The cross-band coupling interference suppression structure according to claim 1, characterized in that, It also includes a balancing support; one end of the balancing support is perpendicularly connected to the frequency selection surface, and the other end of the balancing support is perpendicularly connected to the low-frequency antenna unit; it includes a first balancing substrate and a second balancing substrate, the first balancing substrate and the second balancing substrate are arranged perpendicularly, the first surface of the first balancing substrate and / or the first surface of the second balancing substrate are used for printing microstrip lines, and the second surface of the first balancing substrate and / or the second surface of the second balancing substrate are used for printing slot lines.

8. The cross-band coupling interference suppression structure according to claim 6, characterized in that, The planar spiral inductor structure is disposed on the first patch, and the second port microstrip line is disposed on the second patch; the first patch is disposed on the upper surface of the second patch, and the spiral center of the planar spiral inductor structure is connected to the second port microstrip line through a shorting pin.

9. An inhibition system, characterized in that, It includes a modeling module, an effect acquisition module, and an optimization module; among which, The output of the modeling module is connected to the effect acquisition module, and is used to model the cross-band coupling interference suppression structure as described in any one of claims 1 to 8 based on electromagnetic characteristics, and output model characteristic parameters to the effect acquisition module according to the cross-band coupling interference suppression structure. The effect acquisition module is connected to the optimization module, and outputs coupling interference parameters to the optimization module according to the model characteristic parameters; The optimization module is connected to the modeling module, and adjusts the structural parameters of the cross-band coupling interference suppression structure in the modeling module according to the coupling interference parameters.

10. A suppression method, characterized in that, For the suppression system as described in claim 9, the steps include: Construct a cross-band coupling interference suppression structure and obtain the structural parameters of the frequency-selective surface; Modeling is performed based on electromagnetic properties to obtain model characteristic parameters; Simulations were performed based on the model characteristic parameters to obtain coupling interference parameters that characterize the system's ability to suppress cross-band coupling interference. The software optimization solution is used to solve the coupling interference suppression effect based on the constraints of the structural parameters of the frequency-selective surface, and the maximum feasible solution is obtained. The structural parameters of the crossband coupling interference suppression structure are adjusted based on the maximum feasible solution.

Images