A bandpass frequency selective surface

Abstract

The present invention discloses a bandpass frequency selective surface, comprising: M×N identical units consisting of a metal resonance layer and a dielectric substrate, wherein the metal resonance layer is composed of a periodically arranged pattern array; the metal pattern of the resonance layer comprises four zigzag metal strips that are rotationally symmetrical along the center normal of the metal resonance layer. The present invention has a moderately miniaturized characteristic, and can still maintain a bandpass performance within a stable band when electromagnetic waves of different polarizations are incident at a large angle, has a simple structure, a low profile, is easy to process, and has a better heat dissipation capability than an extremely miniaturized frequency selective surface.

Description

Technical Field

[0001] The invention relates to the technical field of wireless communication devices and electromagnetic filtering, and in particular to a bandpass frequency selective surface. Background Art

[0002] As a frequency-selective device, the main function of frequency selective surfaces in the field of wireless communications is to block unwanted signals and allow signals of target frequencies to pass through, thereby improving the signal-to-noise ratio and improving communication effects. For traditional frequency selective surfaces, the size of their resonant units is equivalent to half the wavelength of the operating frequency. This feature makes it difficult to include a sufficient number of resonant units in a limited space in some practical applications, such as wireless communication systems operating at low frequencies, and therefore it is not easy to obtain an angularly stable frequency response. In order to pursue frequency selective surfaces with high stability, researchers have excessively pursued the miniaturization of frequency selective surfaces. However, in frequency selective surfaces with limited conductivity, real metals are not ideal conductors, so resistance losses need to be considered. In over-miniaturized frequency selective surfaces, the metal arrangement becomes increasingly dense, and the problem of heat generation gradually becomes more serious. Therefore, designing moderately miniaturized frequency selective surfaces with high angular stability is of great significance to the development and practical application of wireless communication systems operating at low frequencies.

[0003] Based on the above problems, how to design an angle-stable, moderately miniaturized bandpass frequency selective surface for wireless local area network frequency band has become an urgent problem to be solved in this field. Summary of the invention

[0004] Based on this, it is necessary to propose a bandpass frequency selective surface with simple structure, easy implementation and high angular stability.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A bandpass frequency selective surface, characterized in that: the frequency selective surface is a periodic structure, including M×N units, adjacent units have no spacing, and M and N are both positive integers greater than or equal to 2;

[0007] The unit comprises a metal resonance layer and a substrate; along the wave incident direction, the metal resonance layer and the substrate are arranged in sequence;

[0008] The metal resonance layer includes four zigzag metal strips which are rotationally symmetrical along the center normal of the metal resonance layer. Each zigzag metal strip is bent 12 times, and the bending angle is 90°.

[0009] The frequency selective surface has a resonance depth of about 0.04 dB near a frequency of 2.45 GHz and has a passband near this frequency; and the insertion loss of the frequency selective surface to electromagnetic waves in the range of 0.92-3.69 GHz is lower than -3 dB.

[0010] The frequency selective surface has an angle-stable frequency response to electromagnetic waves of different polarizations, namely, TE polarization and TM polarization, and has a moderate miniaturization characteristic.

[0011] Optionally, the thickness of the substrate is 1 mm.

[0012] Optionally, the thickness of the metal resonance layer is 30 um.

[0013] Optionally, the side length of the unit is 11.4 mm.

[0014] Optionally, the total length of the meandering metal strip line is 30 mm and the width is 0.2 mm.

[0015] Optionally, the material of the metal resonance layer is metal copper, and the material of the substrate is a polytetrafluoroethylene F4BM high-frequency antenna board.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention proposes a bandpass frequency selective surface, which has an angularly stable frequency response to electromagnetic waves of different polarizations, namely TE polarization and TM polarization, and has a moderate miniaturization characteristic. In the present invention, the current path is extended by a tortuous metal strip line, which reduces the equivalent electrical size of the unit, which is beneficial to reduce the sensitivity to electromagnetic waves incident at large angles and improve the angular stability of the frequency selective surface. The present invention is beneficial to reduce the density of metal arrangement by moderately miniaturizing the unit. Compared with an overly miniaturized frequency selective surface, the present invention enhances the heat dissipation performance of the frequency selective surface without sacrificing angular stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 This is a schematic structural diagram of a single unit of a bandpass frequency selective surface according to an embodiment of the present invention;

[0020] Figure 2A side view of a single unit array of a bandpass frequency selective surface according to an embodiment of the present invention;

[0021] Figure 3 It is a front view of a 2×2 unit array of a bandpass frequency selective surface according to an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the metal resonance layer structure of a single unit of a bandpass frequency selective surface according to an embodiment of the present invention;

[0023] Figure 5 A transmission response diagram of a bandpass frequency selective surface according to an embodiment of the present invention;

[0024] Figure 6 It is a transmission response diagram of a bandpass frequency selective surface under different incident angles in the TE mode of an embodiment of the present invention;

[0025] Figure 7 Graph showing transmission responses of a bandpass frequency selective surface under TM mode at different incident angles according to an embodiment of the present invention.

[0026] Among them, 1. substrate, 2. metal resonance layer, 3. meandering metal strips. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] The present invention provides a bandpass frequency selective surface. The bandpass frequency selective surface is a periodic structure, composed of M×N identical units, with no spacing between adjacent units, and M and N are both integers greater than or equal to 2.

[0030] Figure 1 This is a schematic diagram of the structure of a single unit of a bandpass frequency selective surface according to an embodiment of the present invention. As shown in the figure, the single unit is a square structure, consisting of a substrate 1 and a metal resonance layer 2. In this embodiment, the material of the metal resonance layer 2 is copper, and the material of the substrate 1 is a polytetrafluoroethylene F4BM high-frequency antenna board.

[0031] Figure 2This is a side view of a single unit array of a bandpass frequency selective surface according to an embodiment of the present invention. As shown in the figure, the thickness of the substrate 1 is b, and the thickness of the metal resonance layer 2 is a. In this embodiment, the thickness a of the metal resonance layer 2 is 35 um, and the thickness b of the substrate is 1 mm.

[0032] Figure 3 It is a front view of a 2×2 unit array of a bandpass frequency selective surface according to an embodiment of the present invention. The unit period is P, and in this embodiment, P is 11.4 mm.

[0033] Figure 4 Schematic diagram of the metal resonant layer structure of a single unit of a bandpass frequency selective surface according to an embodiment of the present invention. Figure 4 As shown, the metal resonance layer 2 includes four meandering metal strips 3 which are rotationally symmetrical along the center normal of the metal resonance layer 2, each meandering metal strip is bent 12 times, and the bending angle is 90°. In this embodiment, the initial length d of the meandering metal strip line is 1 mm, the length d1 of the first bend is 5.2 mm, the length d2 of the second bend is 1.2 mm, the length d3 of the third bend is 2.2 mm, the length d4 of the fourth bend is 1.7 mm, the length d5 ​​of the fifth bend is 2.2 mm, the length d6 of the sixth bend is 1.1 mm, the length d7 of the seventh bend is 4.9 mm, the length d8 of the eighth bend is 1.1 mm, the length d9 of the ninth bend is 2 mm, the length d10 of the tenth bend is 1.7 mm, the length d11 of the eleventh bend is 2.3 mm, the length d12 of the twelfth bend is 3.4 mm, and the width w is 0.2 mm.

[0034] Figure 5 This is a transmission performance curve of the bandpass frequency selective surface according to an embodiment of the present invention. The center frequency of the transmission passband is 2.45 GHz, and the insertion loss is -0.04 dB.

[0035] Figure 6 The transmission response of the bandpass frequency selective surface in TE mode under different incident angles according to an embodiment of the present invention; Figure 7 This is the transmission response of the bandpass frequency selective surface TM mode under different incident angles in the embodiment of the present invention. Figure 6 and Figure 7 The bandpass frequency selective surface of the present invention is insensitive to different incident angles, that is, it has a stable transmission response to electromagnetic waves with different incident angles.

[0036] The period of the bandpass frequency selective surface provided by the present invention is 0.09 wavelengths (0.09λ), which is a moderately miniaturized frequency selective surface. Although it is not an extremely miniaturized frequency selective surface, it has achieved the high angular stability of an extremely miniaturized frequency selective surface. However, since it is not an extremely miniaturized frequency selective surface, the metal strips of the metal resonance layer are not so dense, so it can maintain a good heat dissipation capability during operation. In other words, the bandpass frequency selective surface provided by the present invention has the best angular stability among the reported bandpass frequency selective surfaces (it still has relatively stable performance at an incident angle of 80°), but the arrangement of the metal pattern is much sparser than that of the metal patterns of extremely miniaturized frequency selective surfaces with the same angular stability, so it has a better heat dissipation capability.

[0037] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A bandpass frequency selective surface, characterized in that: The frequency selective surface is a periodic structure, including M×N units, adjacent units have no spacing, and M and N are both positive integers greater than or equal to 2; The unit comprises a metal resonance layer and a substrate; along the wave incident direction, the metal resonance layer and the substrate are arranged in sequence; The metal resonance layer comprises four zigzag metal strips which are rotationally symmetrical along the center normal of the metal resonance layer, each zigzag metal strip is bent 12 times, and the bending angle is 90°; the initial sections of the four zigzag metal strips are connected; The width of the meandering metal strip is 0.2 mm, the initial length is 1 mm, the length of the first meandering is 5.2 mm, the length of the second meandering is 1.2 mm, the length of the third meandering is 2.2 mm, the length of the fourth meandering is 1.7 mm, the length of the fifth meandering is 2.2 mm, the length of the sixth meandering is 1.1 mm, the length of the seventh meandering is 4.9 mm, the length of the eighth meandering is 1.1 mm, the length of the ninth meandering is 2 mm, the length d of the tenth meandering is 1.7 mm, the length of the eleventh meandering is 2.3 mm, and the length of the twelfth meandering is 3.4 mm; The center frequency of the transmission passband of the frequency selective surface is 2.45 GHz, and the insertion loss is -0.04 dB; the insertion loss of the frequency selective surface to electromagnetic waves in the range of 0.92-3.69 GHz is less than -3 dB; The frequency selective surface has an angle-stable frequency response to TE polarized and TM polarized electromagnetic waves, and has a miniaturized characteristic with a period of 0.09 wavelengths.

2. The bandpass frequency selective surface according to claim 1, characterized in that: The thickness of the substrate is 1 mm.

3. The bandpass frequency selective surface according to claim 1, characterized in that: The thickness of the metal resonance layer is 35 um.

4. The bandpass frequency selective surface according to claim 1, characterized in that: The side length of the unit is 11.4 mm.

5. The bandpass frequency selective surface according to claim 1, characterized in that: The material of the metal resonance layer is metal copper, and the material of the substrate is a polytetrafluoroethylene F4BM high-frequency antenna board.

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