Multiband multi-angle low-profile spatial filter

Abstract

The application belongs to the technical fields of electromagnetic wave regulation and control and microwave antenna, and discloses a multi-frequency-band multi-angle low-profile spatial filter, which comprises an upper-layer metasurface metal layer, a dielectric substrate layer and a lower-layer metasurface metal layer, the upper-layer metasurface metal layer and the lower-layer metasurface metal layer are etched on the upper and lower surfaces of the dielectric substrate layer and are symmetrically arranged, the upper-layer metasurface metal layer and the lower-layer metasurface metal layer are respectively composed of a plurality of identical metasurface units arranged in an array, each metasurface unit is combined by three groups of resonant units with different sizes, and each resonant unit comprises a circular ring resonant groove, a cross-shaped resonant groove and an X-shaped resonant groove. The application can work in multiple frequency bands while reducing the profile height, and realizes filtering of signals with different angles of incidence.

Description

Technical Field

[0001] This application belongs to the field of electromagnetic wave modulation and microwave antenna technology, specifically relating to a multi-band, multi-angle, low-profile space filter. Background Technology

[0002] With the rapid development of modern wireless communication and radar systems, the control dimensions of electromagnetic waves are no longer limited to traditional frequency and polarization. The propagation direction of electromagnetic waves has become a key physical dimension in space signal processing. As a device capable of selectively propagating electromagnetic waves according to the incident angle, space filters have significant application value in fields such as antenna sidelobe suppression, angle isolation in multi-user environments, spatial multiplexing, and high-performance radome design.

[0003] Early spatial filtering research mainly relied on geometric optics principles and the Brewster effect, such as achieving impedance matching at a specific angle by stacking isotropic dielectric plates or magnetic materials. However, such methods often require large physical space and heavy volumetric structures, which runs counter to the trend of modern electromagnetic systems pursuing lightweight, miniaturization and low-profile integration, thus limiting their application in airborne or portable devices.

[0004] In recent years, the planarization design of space filters based on metasurfaces has gradually become a research hotspot. Although such designs have reduced the structural thickness to some extent, existing space filter planarization technologies still face severe challenges: On the one hand, in order to meet the impedance matching conditions at a specific incident angle, most existing designs must introduce a thicker air layer or an additional metal metasurface layer between multi-layer unit structures. This not only increases the mechanical complexity of the structure but also results in a still high profile height. On the other hand, existing angle-selective surfaces are usually designed only for a single operating frequency, and once their transmission angle is fixed, it is difficult to change. They lack the flexibility to achieve different spatial transmission windows for different frequencies in complex multi-band environments, and cannot meet the needs of modern multifunctional wireless communication systems for independent spatial control of multiple frequency bands.

[0005] Therefore, developing an angle-selective surface that can achieve independent multi-band control under ultra-low profile conditions and whose transmission angle dynamically switches with frequency has become a key technical challenge that urgently needs to be overcome in the field of electromagnetic control. Summary of the Invention

[0006] To address the aforementioned issues, this application proposes a multi-band, multi-angle, low-profile spatial filter. Compared to traditional spatial filters, this application reduces the profile height while operating in multiple frequency bands, enabling filtering of incident signals at different angles.

[0007] To achieve the above objectives, this application employs the following technical solution:

[0008] This application discloses a multi-band, multi-angle, low-profile spatial filter. The spatial filter includes an upper metasurface metal layer, a dielectric substrate layer, and a lower metasurface metal layer. The upper and lower metasurface metal layers are etched on the upper and lower surfaces of the dielectric substrate layer and are symmetrically arranged. The upper and lower metasurface metal layers are each composed of multiple identical metasurface units arranged in an array. Each metasurface unit is composed of three sets of resonant units of different sizes.

[0009] A further improvement of this application is that each of the resonant units includes a circular ring resonant groove, a cross-shaped resonant groove, and an X-shaped resonant groove, and the geometric centers of the circular ring resonant groove, the cross-shaped resonant groove, and the X-shaped resonant groove all coincide with the geometric center of the metasurface unit in which the circular ring resonant groove, the cross-shaped resonant groove, and the X-shaped resonant groove are located.

[0010] A further improvement of this application is that the transmission coefficient of the spatial filter has the following relationship with the incident frequency and angle: at a frequency of 12.71 GHz, the transmission angle is 0° to 5°; at a frequency of 11.30 GHz, the transmission angle is 29° to 31°; and at a frequency of 10.73 GHz, the transmission angle is 39° to 41°.

[0011] A further improvement of this application is that the thickness of the dielectric substrate layer is: =0.8mm, the material is F4BM220, its dielectric constant is 2.2, the loss tangent is 0.001, and the size of the metasurface unit is... The length × width × height of the spatial filter is .

[0012] A further improvement of this application is that the resonant frequencies of the circular ring resonant groove, the cross-shaped resonant groove, and the X-shaped resonant groove are different.

[0013] The beneficial effects of this application are:

[0014] This application overcomes the shortcomings of existing spatial filters, such as high profile, single operating frequency band, and fixed filtering angle. Specifically:

[0015] First, in terms of structural design, this application breaks through the limitations of traditional space filters that rely on air layers or multi-layer dielectric stacking to achieve impedance matching. By arranging symmetrical metal topologies on both sides of a single-layer dielectric substrate, an ultra-low profile height as low as 0.029 wavelengths is achieved. This extreme compactness not only significantly reduces the weight of the overall structure but also greatly improves the mechanical robustness of the system, enabling it to perfectly adapt to modern integrated electromagnetic environments with extremely demanding space load requirements, such as airborne and shipborne applications.

[0016] Secondly, this application achieves a unique three-band independent angle selection function through the resonance and impedance modulation of the metasurface unit geometry. It can achieve precise functional mapping between multiple preset transmission angle windows according to the switching of the operating frequency, and maintains extremely high transmission efficiency (insertion loss as low as below 1dB) and excellent angle selection accuracy (transmission bandwidth as narrow as 5°) in each operating frequency band. This provides highly flexible spatial filtering and signal guiding capabilities for multi-frequency wireless communication systems.

[0017] Furthermore, this application exhibits extremely strong suppression characteristics within the non-target incident angle range, with a stopband suppression capability exceeding 15dB. It can effectively filter multipath interference and clutter from undesired directions, significantly enhancing the spatial isolation and anti-interference performance of the system.

[0018] Finally, the metal-dielectric-metal configuration adopted in this application has the characteristics of simple structure, no need for complex power supply network or tuning components, and is fully compatible with standard printed circuit board (PCB) processing technology. While ensuring high performance, it significantly reduces production costs and process difficulty, and has extremely high engineering practical value and large-scale promotion potential. Attached Figure Description

[0019] Figure 1 This is a functional diagram of this application.

[0020] Figure 2 This is a schematic diagram of the spatial filter structure of this application.

[0021] Figure 3 This is the equivalent circuit model of this application.

[0022] Figure 4 The transmittance coefficient |S| under the three-angle passband 21 | Curve showing variation with frequency.

[0023] Figure 5 The transmittance coefficient |S at other angles 21 | Curve showing variation with frequency.

[0024] Figure 6 It refers to the spatial angle filtering performance under three operating frequency bands. Detailed Implementation

[0025] The embodiments of the present invention will be disclosed below with reference to the drawings. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details are not intended to limit the present invention. That is, in some embodiments of the present invention, these practical details are not essential. In addition, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner.

[0026] This application relates to a multi-band, multi-angle, low-profile space filter. Angle filtering is illustrated below. Figure 1 As shown, specifically: at 12.71 GHz, the transmission angle is 0° to 5°; at 11.30 GHz, the transmission angle is 29° to 31°; and at 10.73 GHz, the transmission angle is 39° to 41°. Based on the impedance matching principle and equivalent circuit theory, this application achieves three-band spatial angle filtering by introducing and designing three sets of resonant structures. Its structure is simple and highly feasible, and can be well applied in modern wireless communication systems such as radome design and spatial filtering.

[0027] like Figure 2 As shown, this application discloses a multi-band, multi-angle, low-profile spatial filter. The spatial filter includes an upper metasurface metal layer, a dielectric substrate layer, and a lower metasurface metal layer. The upper and lower metasurface metal layers are etched on the upper and lower surfaces of the dielectric substrate layer and are symmetrically arranged. The upper and lower metasurface metal layers are each composed of multiple identical metasurface units arranged in an array. Each metasurface unit is composed of three sets of resonant units of different sizes.

[0028] When performing filtering analysis on the spatial filter of this application, the transmission coefficient S is mainly referenced. 21 The amplitude of the spectral line, the larger the amplitude, the higher the value of |S|. 21 | ≥ -1 dB indicates that the electromagnetic wave has high transmittance and low amplitude, i.e., |S 21 | ≤ -15 dB indicates that electromagnetic waves cannot be transmitted.

[0029] like Figure 2 As shown, each resonant unit of this application includes a circular annular resonant groove, a cross-shaped resonant groove, and an X-shaped resonant groove. The geometric centers of the circular annular resonant groove, the cross-shaped resonant groove, and the X-shaped resonant groove all coincide with the geometric center of the metasurface unit where the circular annular resonant groove, the cross-shaped resonant groove, and the X-shaped resonant groove are located. The radius of the circular annular resonant groove is... =5.1mm, width =0.5mm, the length of the cross-shaped resonant groove is =12mm, width is =0.3mm, the length of the X-shaped resonant groove is =12mm, width is =0.5mm.

[0030] The thickness of the dielectric substrate layer is =0.8mm. This application does not require an additional air layer for impedance matching; without the thickness of the air layer, its profile height is reduced. Dimensions are measured in terms of wavelength; in a vacuum, the wavelength of an electromagnetic wave equals the speed of light divided by its frequency. This application meets a minimum operating frequency of 10.73GHz, corresponding to a wavelength of... Therefore, a height of 0.8 mm is 0.0008 / 0.028 = 0.029, meaning that this application achieves an ultra-low profile height as low as 0.029 wavelengths.

[0031] The dielectric substrate material of this application is F4BM220, with a dielectric constant of 2.2 and a loss tangent of 0.001. The size of the metasurface unit is... The length × width × height of the spatial filter is .

[0032] The equivalent circuit of a spatial filter is as follows: Figure 3 As shown, the cross-shaped resonant slot and the X-shaped resonant slot are respectively mapped to two sets of series LC resonant branches, namely L1-C1 and L2-C2. The annular resonant slot is equivalent to a composite resonant circuit in which an inductor L3 and a capacitor C3 are connected in series and then in parallel with an inductor L4. The dielectric substrate layer is equivalent to a T-shaped network. The two inductors in the dielectric substrate layer A series connection with a capacitor The filter is composed of parallel components. Through precise optimization of the equivalent circuit mapping of the resonant structure, the impedance matching conditions in free space are accurately met at the target frequency and specific incident angle. The specific optimized equivalent circuit parameters are shown in Table 1, where capacitance is in fF and inductance is in nH.

[0033] Table 1

[0034] The three passbands will then be analyzed independently. For example... Figure 4 As shown in (a), when the electromagnetic wave is incident perpendicularly, the spatial angle filter exhibits bandpass filtering characteristics at 12.71 GHz, and its transmission zero is: .like Figure 4 As shown in (b), when the electromagnetic wave is incident at a 30° angle, the spatial angle filter exhibits bandpass filtering characteristics at 11.30 GHz, and its transmission zero is: and .like Figure 4 As shown in (c), when the electromagnetic wave is incident at a 40° angle, the spatial angle filter exhibits bandpass filtering characteristics at 10.73 GHz, and its transmission zero is: and . Figure 5This indicates that the transmission coefficient of electromagnetic waves incident at other incident angles in the three operating frequency bands is less than -15dB. Figure 6 The angle selectivity performance of the spatial filter at 12.71 GHz, 11.20 GHz and 10.73 GHz was demonstrated, further confirming its spatial angle filtering performance.

[0035] This invention has the advantages of simple structure, low profile and multi-frequency angle selectivity, and has broad application prospects in advanced radome design, angle-selective filtering and interference suppression in modern wireless communication.

[0036] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A multi-band, multi-angle, low-profile spatial filter, the spatial filter comprising an upper metasurface metal layer, a dielectric substrate layer, and a lower metasurface metal layer, characterized in that: The upper metasurface metal layer and the lower metasurface metal layer are etched on the upper and lower surfaces of the dielectric substrate layer, and the upper metasurface metal layer and the lower metasurface metal layer are symmetrically arranged. The upper metasurface metal layer and the lower metasurface metal layer are each composed of multiple identical metasurface units arranged in an array, and each metasurface unit is composed of three sets of resonant units of different sizes.

2. The multi-band, multi-angle, low-profile spatial filter according to claim 1, characterized in that: Each of the resonant units includes a circular resonant groove, a cross-shaped resonant groove, and an X-shaped resonant groove. The geometric centers of the circular resonant groove, the cross-shaped resonant groove, and the X-shaped resonant groove all coincide with the geometric center of the metasurface unit in which the circular resonant groove, the cross-shaped resonant groove, and the X-shaped resonant groove are located.

3. A multi-band, multi-angle, low-profile spatial filter according to claim 1, characterized in that: The transmission coefficient of the spatial filter is related to the incident frequency and angle as follows: at a frequency of 12.71 GHz, the transmission angle is 0° to 5°; at a frequency of 11.30 GHz, the transmission angle is 29° to 31°; and at a frequency of 10.73 GHz, the transmission angle is 39° to 41°.

4. A multi-band, multi-angle, low-profile spatial filter according to claim 1, characterized in that: The thickness of the dielectric substrate layer is =0.8mm, the length × width × height of the spatial filter is .

5. A multi-band, multi-angle, low-profile spatial filter according to claim 1, characterized in that: The resonant frequencies of circular resonant grooves, cross-shaped resonant grooves, and X-shaped resonant grooves are different.

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