A wideband low insertion loss high selectivity frequency selective surface and applications

Abstract

The application discloses a kind of wide band low insertion loss high selectivity frequency selective surface and application.It includes several unit structures, unit structure includes main structure and longitudinal structure, main structure includes two layers of rotation symmetry, aperture type frequency selective surface screen interval parallel arrangement of the dielectric layer and metal layer, longitudinal structure includes vertical and auxiliary metal strip, vertical metal strip upper end penetrates the through groove of upper aperture type frequency selective surface screen and does not contact electrically connected;Vertical metal strip bottom is equipped with auxiliary metal strip, auxiliary metal strip is pasted on the upper surface of lower aperture type frequency selective surface screen dielectric layer.The application inserts transmission zero between stop band and passband by longitudinal structure, realizes the low loss and high selectivity of passband transmission response under dual polarization, effectively improves the isolation of multi-frequency antenna array, improves the antenna pattern deterioration problem caused by co-aperture antenna coupling, with the characteristics of wide band, high selectivity, low loss, low profile, simple structure.

Description

TECHNICAL FIELD

[0001] The present application relates to a frequency selective surface in the field of electromagnetic compatibility and co-boresight antenna decoupling, and in particular to a wide-band low insertion loss high selectivity frequency selective surface (FSS) and its application in co-boresight antenna decoupling. BACKGROUND

[0002] With the development of mobile communication technology, human society has entered the 5G era, but communication operators still need to provide services for 2G, 3G and 4G device users, and multiple communication systems will coexist for a long time. The separate arrangement of base station antennas of various frequency bands in a mobile communication system will lead to a shortage of site resources and increase the cost of construction, operation and maintenance.

[0003] Co-boresight antennas can improve the space utilization of base stations and realize multi-system co-sites by placing multiple antennas of different frequency bands in the same aperture. Co-boresight antennas will produce a certain degree of coupling and lead to deterioration of antenna performance. In recent years, researchers have begun to introduce frequency selective surfaces into the design of multi-band antenna decoupling. Due to its spatial filtering characteristics, it can effectively improve the isolation of multi-band antennas and achieve the effect of reducing antenna coupling or even complete decoupling, making it possible to realize high-performance multi-band co-boresight antennas.

[0004] Existing two-dimensional FSSs cannot overcome the problem that the suppression degree of the transmission response stop band deteriorates with the increase of the incident angle of TM polarized electromagnetic waves, and the passband selectivity of the FSS is poor at large incident angles. Three-dimensional FSSs are limited by their structural characteristics. When the incident angle of dual-polarized electromagnetic wave excitation increases, the average loss of the transmission response passband will increase rapidly. Currently, there are few three-dimensional FSSs that can maintain a low-1dB loss in the dual-polarized transmission response passband when the incident angle of electromagnetic waves is greater than 40 degrees. The existing FSSs with low selectivity and high passband loss cannot meet the urgent need of co-boresight antennas to reduce antenna coupling or even achieve complete decoupling. SUMMARY

[0005] In view of the limited existing multi-band antenna decoupling technology and the problem of co-boresight antenna decoupling for wide-band low insertion loss high selectivity frequency selective surfaces, the present application designs a frequency selection structure based on the theory of frequency selective surface, which can effectively enhance the decoupling effect of multi-band co-boresight antennas.

[0006] By placing a FSS with low insertion loss and high selectivity in the co-boresight antenna system, the present application can effectively suppress the coupling between the working antennas in the passband frequency band of the FSS and the working antennas in the stop band of the FSS, thereby more effectively improving the problem of antenna pattern deterioration caused by co-boresight antenna coupling.

[0007] The application introduces an L-shaped metal patch in a double-layer cascaded band-pass FSS through structural innovation, successfully inserts a transmission zero point between the stop band and pass band of TM polarization transmission response, ensures extremely low average loss of the pass band, and makes the TM polarization transmission response stop band performance of the FSS much better than that of a traditional FSS. The application can be used for the research of co-aperture antenna decoupling and has great engineering application value.

[0008] The technical scheme adopted by the application to solve the problems in the related art is as follows:

[0009] The application comprises a plurality of identical, periodically arranged unit structures, each of which mainly comprises a main structure and a longitudinal structure perpendicular to the plane where the main structure is located, the main structure mainly comprises two layers of aperture type frequency selective surface screens arranged in parallel with an interval, each of the aperture type frequency selective surface screens mainly comprises a dielectric layer and a metal layer stacked together, and the two aperture type frequency selective surface screens are arranged in parallel with the dielectric layers facing each other; the two layers of aperture type frequency selective surface screens are connected and supported by the longitudinal structure, and the lower aperture type frequency selective surface screen is connected with the longitudinal structure.

[0010] The sizes of the outer edges of the two aperture type frequency selective surface screens of the unit structure are the same.

[0011] The space between the two aperture type frequency selective surface screens is air.

[0012] The metal layer mainly comprises a ring-shaped metal sheet and an intermediate metal sheet, the outer edge of the ring-shaped metal sheet has the same size and shape as the dielectric layer, the intermediate metal sheet is arranged in the ring-shaped metal sheet, and there is a gap between the outer periphery of the intermediate metal sheet and the inner periphery of the ring-shaped metal sheet.

[0013] The dielectric layer, the intermediate metal sheet and the ring-shaped metal sheet are all square, the gap between each side of the four sides of the intermediate metal sheet and the ring-shaped metal sheet is an S-shaped serrated gap, and the serration width of the gap gradually increases from the middle to the two ends.

[0014] The four corners of the intermediate metal sheet are supported and connected with the ring-shaped metal sheet by a dielectric material of the same material as the dielectric layer, and the dielectric material and the dielectric layer are integrally fixed.

[0015] The ring-shaped metal sheet of the metal layer of the lower aperture type frequency selective surface screen is provided with a through slot on one side, and the through slot is provided with a dielectric material of the same material as the dielectric layer and integrally fixed with the dielectric layer.

[0016] The annular metal sheet and the intermediate metal sheet are made through a PCB processing technology.

[0017] The annular metal sheet of the metal layer of the two-layer aperture type frequency selective surface screen is provided with a through groove at the same position on the upper and lower layers, and the through groove is used for arranging a longitudinal structure and cooperating with the longitudinal structure; the longitudinal structure comprises a vertical metal strip and an auxiliary metal strip, the bottom end of the vertical metal strip is inserted into the through groove of the annular metal sheet of the lower-layer aperture type frequency selective surface screen, and is electrically connected with the annular metal sheet of the lower-layer aperture type frequency selective surface screen at one position; the upper end of the vertical metal strip penetrates out of the through groove of the annular metal sheet of the upper-layer aperture type frequency selective surface screen in sequence after passing through the dielectric layer of the lower-layer aperture type frequency selective surface and the dielectric layer of the upper-layer aperture type frequency selective surface screen, and is not in contact and not electrically connected with the annular metal sheet of the upper-layer aperture type frequency selective surface screen; the auxiliary metal strip is integrally arranged on the side surface of the bottom end of the vertical metal strip, and is arranged parallel to the dielectric layer of the lower-layer aperture type frequency selective surface screen and is close to the upper surface of the dielectric layer of the lower-layer aperture type frequency selective surface screen.

[0018] The side surfaces of the vertical metal strip and the auxiliary metal strip are provided with dielectric materials of the same material as the dielectric layer, and the dielectric materials are integrally fixed with the dielectric layer to support the vertical metal strip.

[0019] The material of the dielectric layer is Rogers RT5880.

[0020] The metal pattern layer of the FSS screen is an aperture type square ring gap, and the curling technology is used for miniaturization design.

[0021] The application can be applied to frequency selection characteristics in the decoupling of a common aperture antenna.

[0022] The application can transmit electromagnetic waves with TE and TM polarizations at -60° to 60° of incidence at an ultra-low loss in a passband frequency range of 3.3GHz to 3.8GHz, and can reflect the electromagnetic waves at a high suppression degree in a stopband frequency range of 0.69GHz to 2.69GHz.

[0023] The beneficial results of the application are:

[0024] The application realizes the wide-band low insertion loss high selectivity frequency selection performance by the FSS structure design of low profile, miniaturization, easy processing and low cost.

[0025] The application is suitable for multi-band co-antenna decoupling.

[0026] The application has the characteristics of wide-band, high selectivity, low loss, low profile and simple structure, does not need to occupy too much space, and is easy to add in a co-antenna system.

[0027] The application has the characteristics of fast roll-off speed of the passband to the stopband, simple structure and easy processing, and can effectively improve the isolation of a multi-band antenna array when arranged in a co-antenna, and is particularly suitable for suppressing antenna mutual coupling under the co-antenna layout architecture of the multi-band antenna array, and effectively improves the problem of pattern deterioration caused by antenna mutual coupling. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the application and, together with the specification, serve to explain the principles of the application.

[0029] Figure 1 A three-dimensional view of the wide-band low insertion loss high selectivity FSS unit structure provided by the application is shown in the figure.

[0030] Figure 2 A side view of the wide-band low insertion loss high selectivity FSS unit structure provided by the application is shown in the figure.

[0031] Figure 3A three-dimensional view of the longitudinal structure of the wide-band low insertion loss high selectivity FSS unit structure provided by the present application is shown in the drawings.

[0032] Figure 4 A top view of the dielectric layer of the wide-band low insertion loss high selectivity FSS unit structure provided by the present application is shown in the drawings.

[0033] Figure 5 A top view of the metal layer of the wide-band low insertion loss high selectivity FSS unit structure provided by the present application is shown in the drawings.

[0034] Figure 6 A three-dimensional schematic view of the wide-band low insertion loss high selectivity FSS provided by the present application is shown in the drawings.

[0035] Figure 7 A stop-band transmission response graph of the FSS when a TE polarized electromagnetic wave is excited at a vertical incidence provided by the present application is shown in the drawings.

[0036] Figure 8 A stop-band transmission response graph of the FSS when a TE polarized electromagnetic wave is excited at a ±60-degree incidence provided by the present application is shown in the drawings.

[0037] Figure 9 A stop-band transmission response graph of the FSS when a TM polarized electromagnetic wave is excited at a ±60-degree incidence provided by the present application is shown in the drawings.

[0038] Figure 10 A pass-band transmission response graph of the FSS when a TE polarized electromagnetic wave is excited at a vertical incidence provided by the present application is shown in the drawings.

[0039] Figure 11 A pass-band transmission response graph of the FSS when a TE polarized electromagnetic wave is excited at a ±60-degree incidence provided by the present application is shown in the drawings.

[0040] Figure 12 A pass-band transmission response graph of the FSS when a TM polarized electromagnetic wave is excited at a ±60-degree incidence provided by the present application is shown in the drawings.

[0041] Figure 13 A comparison graph of the transmission response of the FSS and a conventional FSS when a TE polarized electromagnetic wave is excited at a 60-degree incidence provided by the present application is shown in the drawings.

[0042] Figure 14 A comparison graph of the transmission response of the FSS and a conventional FSS when a TM polarized electromagnetic wave is excited at a 60-degree incidence provided by the present application is shown in the drawings.

[0043] In the drawings: main structure 1; longitudinal structure 2, vertical metal strip 21, auxiliary metal strip 22; aperture type frequency selective surface screen 3, dielectric layer 31, metal layer 32.

[0044] The result parameters shown in the drawings are:

[0045] The result parameters shown in the drawings are:

[0046] DETAILED DESCRIPTION

[0047] The application will be further described below with reference to the drawings.

[0048] As Figures 1-5 shown, the frequency selective surface structure FSS mainly consists of a main structure 1 and a longitudinal structure 2 perpendicular to the plane where the main structure 1 is located, the main structure 1 mainly consists of two layers of aperture type frequency selective surface screens 3 with a rotationally symmetric structure arranged in parallel with an interval, each aperture type frequency selective surface screen 3 mainly consists of a layer of dielectric layer 31 on the inner side and a layer of metal layer 32 on the outer side stacked together, the two aperture type frequency selective surface screens 3 are arranged in parallel with the dielectric layer facing each other, and the metal layers of the two aperture type frequency selective surface screens 3 are arranged outward; the two layers of aperture type frequency selective surface screens 3 are supported and connected by the longitudinal structure 2, and the lower aperture type frequency selective surface screen 3 is connected with the longitudinal structure 2 and electrically connected with the outside through the longitudinal structure 2.

[0049] The sizes of the outer edges of the two aperture type frequency selective surface screens 3 are the same.

[0050] The metal layer mainly consists of a ring-shaped metal sheet and an intermediate metal sheet, and is a rotationally symmetric structure, the outer edge of the ring-shaped metal sheet has the same size and shape as the dielectric layer, and the intermediate metal sheet is arranged inside the ring-shaped metal sheet, and there is a gap between the outer periphery of the intermediate metal sheet and the inner periphery of the ring-shaped metal sheet.

[0051] The dielectric layer, the intermediate metal sheet and the ring-shaped metal sheet are all square, the gap between each side of the four sides of the intermediate metal sheet and the inner periphery of the ring-shaped metal sheet is an S-shaped serrated gap, and the serration width of the gap gradually increases from the middle to the two ends. The S-shaped serrated gap is formed by arranging metal strips alternately on both sides of the gap, and the alternately arranged metal strips are connected to the intermediate metal sheet and the ring-shaped metal sheet respectively.

[0052] The intermediate metal sheet is provided with a dielectric material of the same material as the dielectric layer at the four corners, and is supported and connected with the ring-shaped metal sheet through the dielectric material of the same material as the dielectric layer 31, and the dielectric material and the dielectric layer 31 are integrally fixedly connected.

[0053] The ring-shaped metal sheet of the metal layer of the lower aperture type frequency selective surface screen 3 is provided with a through slot on one side, and the through slot is provided with a dielectric material of the same material as the dielectric layer 31 integrally fixed with the dielectric layer 31.

[0054] The ring-shaped metal sheet and the intermediate metal sheet are both made by PCB integrated processing technology, and finally form a whole piece of metal sheet with a thickness range of one ounce.

[0055] The annular metal sheet of the metal layer of the two-layer aperture type frequency selective surface screen 3 is provided with a through groove at the same position on the upper and lower layers, and the through groove is used for arranging and matching the longitudinal structure 2; the longitudinal structure 2 comprises a vertical metal strip 21 and an auxiliary metal strip 22, the bottom end of the vertical metal strip 21 is inserted into the through groove of the annular metal sheet of the lower-layer aperture type frequency selective surface screen 3, and is electrically connected with the annular metal sheet of the lower-layer aperture type frequency selective surface screen 3 at one position; the upper end of the vertical metal strip 21 sequentially penetrates through the dielectric layer 31 of the lower-layer aperture type frequency selective surface screen 3, the dielectric layer 31 of the upper-layer aperture type frequency selective surface screen 3, and then penetrates out of the through groove of the annular metal sheet of the upper-layer aperture type frequency selective surface screen 3, and is not in contact and electrically connected with the annular metal sheet of the upper-layer aperture type frequency selective surface screen 3; the auxiliary metal strip 22 is integrally connected with the side surface of the bottom of the vertical metal strip 21, and the auxiliary metal strip 22 is arranged parallel to the dielectric layer 31 of the lower-layer aperture type frequency selective surface screen 3 and closely adheres to the upper surface of the dielectric layer 31 of the lower-layer aperture type frequency selective surface screen 3.

[0056] The side surfaces of the vertical metal strip 21 and the auxiliary metal strip 22 are provided with dielectric materials of the same material as the dielectric layer 31, and the dielectric materials are integrally fixedly connected with the dielectric layer 31 to support the vertical metal strip 21.

[0057] The auxiliary metal strip 22 is horizontally parallel to the dielectric layer 31, and provides equivalent capacitance and inductance.

[0058] The structure of the vertical metal strip 21 and the auxiliary metal strip 22 can significantly reduce the suppression degree of the FSS structure blocking band transmission response when the TM polarized electromagnetic wave excitation oblique incidence under the premise of ensuring the low loss of the transmission passband, introduces a transmission zero point on the left side of the passband, and realizes the rapid roll-off of the FSS structure blocking band and the high selectivity of the passband under the dual polarization.

[0059] Further, the vertical metal strip 21 of the longitudinal structure 2 penetrates through the upper and lower-layer aperture type frequency selective surface screens 3, and is higher than the upper-layer aperture type frequency selective surface screen 3, and is not electrically connected with the metal layer of the upper-layer aperture type frequency selective surface screen 3.

[0060] The present application is a frequency selective structure based on the theory of frequency selective surface, and the resonant unit arranged periodically transmits or reflects the incident electromagnetic wave of different frequencies, incident angles and polarization modes. Specifically, the present application can transmit the TE and TM polarized electromagnetic wave excited by-60° to 60° incidence with ultra-low loss in the passband frequency band of 3.3GHz to 3.8GHz, and can reflect with high suppression degree in the blocking band frequency band of 0.69GHz to 2.69GHz.

[0061] The verification condition of the embodiment of the present application is as follows:

[0062] As shown in Figures 1-5 , a wide stopband low insertion loss high selectivity FSS structure of an embodiment of the application. The upper and lower surfaces of the structure are aperture type square ring slot FSS units, the metal layers of the aperture type frequency selective surface screens 3 of the upper and lower layers are rotationally symmetrical structures, and the sizes are completely consistent.

[0063] In order to reduce the passband loss caused by the medium and expand the bandwidth of the FSS under the large-angle incidence of the TE mode electromagnetic wave, a medium punching design is adopted, the medium surface is attached with metal to provide support for the metal layer, and the thickness of the metal is one ounce. The foam with a thickness of AH is used as the structural support of the aperture type frequency selective surface screens 3 of the upper and lower layers, and at the same time provides a suitable distance for the coupling of the double-layer aperture type frequency selective surface screens 3. The medium layer is Rogers RT5880 (lossy) with a relative dielectric constant ε r = 2.2 and a loss tangent of 0.0009, and the thickness is 0.127 mm.

[0064] Figure 6 A three-dimensional schematic diagram of the wide stopband low insertion loss high selectivity frequency selective surface proposed in the application is composed of Figure 1 unit structures arranged periodically in the two-dimensional plane direction. Only the arrangement of 8x8 unit structures is shown in the figure.

[0065] As shown in Figure 7 and Figure 10 , the FSS is built in the simulation software, and the stopband transmission response of the FSS under the vertical incidence of the TE and TM polarized electromagnetic wave is obtained through simulation. A 2GHz wide stopband is provided in the frequency band of 0.69GHz to 2.69GHz, and the stopband suppression degree is better than -13.1dB. In the passband frequency band of 3.3GHz to 3.8GHz, the transmission loss of the electromagnetic wave is better than -0.15dB.

[0066] As shown in Figure 8 and Figure 11 , the FSS is built in the simulation software, and the stopband transmission response of the FSS under the ±60 degree incidence of the TE polarized electromagnetic wave is obtained through simulation. A 2GHz wide stopband is provided in the frequency band of 0.69GHz to 2.69GHz, and the stopband suppression degree is better than -20.6dB. In the passband frequency band of 3.3GHz to 3.8GHz, the transmission loss of the electromagnetic wave is better than -0.6dB.

[0067] As shown in Figure 9 and Figure 12The FSS is built in simulation software, and the band-stop transmission response of the FSS under the excitation of TM polarized electromagnetic wave at ±60 degrees of incidence is obtained through simulation, which provides a 2GHz wide band-stop in the frequency band of 0.69GHz to 2.69GHz, and the stop-band rejection is better than -20dB, and the transmission loss of electromagnetic wave is better than -0.35dB in the pass-band frequency band of 3.3GHz to 3.8GHz.

[0068] As shown in Figure 13 The FSS built in simulation software and the traditional FSS without longitudinal structure are compared in terms of transmission response to 60-degree incidence of TE polarized electromagnetic wave, and the difference between the transmission responses of the two is small because the electric field of TE polarized wave does not change with the change of incidence angle and is always parallel to the surface of the FSS structure.

[0069] As shown in Figure 14 The FSS built in simulation software and the traditional FSS without longitudinal structure are compared in terms of transmission response to 60-degree incidence of TM polarized electromagnetic wave, and the transmission response of the FSS structure inserts a transmission zero point between the band-stop and the pass-band, and the zero point only occurs when the electric field has a Z-axis component. The transmission zero point introduced by the longitudinal structure makes the transmission response of the FSS much better than that of the traditional FSS, while ensuring that the average loss of the pass-band is very low.

[0070] The above-described embodiments are merely descriptions of the preferred embodiments of the present application, and do not limit the scope of the present application, and various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art without departing from the spirit of the present application shall fall within the protection scope of the claims of the present application.

Claims

1. A frequency selective surface with wide stopband, low insertion loss, and high selectivity, characterized in that: It includes several identical, periodically arranged unit structures. Each unit structure mainly consists of a main structure (1) and a longitudinal structure (2) perpendicular to the plane of the main structure (1). The main structure (1) mainly consists of two aperture-type frequency selective surface screens (3) with rotational symmetry arranged in parallel at intervals. Each aperture-type frequency selective surface screen (3) mainly consists of a dielectric layer (31) and a metal layer (32) stacked together. The two aperture-type frequency selective surface screens (3) are arranged in parallel with the dielectric layer facing each other. The two aperture-type frequency selective surface screens (3) are supported and connected by the longitudinal structure (2), and the lower aperture-type frequency selective surface screen (3) is connected to the longitudinal structure (2). The annular metal sheets of the two-layer aperture-type frequency selective surface (3) are provided with through slots at the same location on both the upper and lower sides. The through slots are used to arrange the longitudinal structure (2) and cooperate with the longitudinal structure (2). The longitudinal structure (2) includes a vertical metal strip (21) and an auxiliary metal strip (22). The bottom end of the vertical metal strip (21) is inserted into the through slot of the annular metal sheet of the lower aperture-type frequency selective surface (3) and is electrically connected to the annular metal sheet of the lower aperture-type frequency selective surface (3). The upper end of the vertical metal strip (21) passes through the lower aperture-type frequency selective surface (3) in sequence. 3) The dielectric layer (31) of the upper aperture type frequency selective surface screen (3) passes through the through groove of the annular metal sheet of the upper aperture type frequency selective surface screen (3), and there is no contact or electrical connection between it and the annular metal sheet of the upper aperture type frequency selective surface screen (3); the bottom side of the vertical metal strip (21) is integrally connected with an auxiliary metal strip (22), the auxiliary metal strip (22) is arranged parallel to the dielectric layer (31) of the lower aperture type frequency selective surface screen (3) and closely attached to the upper surface of the dielectric layer (31) of the lower aperture type frequency selective surface screen (3); The vertical metal strip (21) and the auxiliary metal strip (22) are provided with a dielectric material of the same material as the dielectric layer (31) on their sides. The dielectric material and the dielectric layer (31) are fixed together to support the vertical metal strip (21).

2. The frequency selective surface with wide stopband, low insertion loss, and high selectivity according to claim 1, characterized in that: The outer edges of the two aperture-type frequency selective surface screens (3) of the unit structure are the same size.

3. The frequency selective surface with wide stopband, low insertion loss, and high selectivity according to claim 1, characterized in that: The metal layer is mainly composed of an annular metal sheet and an intermediate metal sheet. The outer edge of the annular metal sheet has the same shape and size as the dielectric layer. The intermediate metal sheet is arranged inside the annular metal sheet, and there is a gap between the outer periphery of the intermediate metal sheet and the inner periphery of the annular metal sheet.

4. The frequency selective surface with wide stopband, low insertion loss, and high selectivity according to claim 3, characterized in that: The dielectric layer, the intermediate metal sheet, and the annular metal sheet are all square. The gap between each side of the intermediate metal sheet and the annular metal sheet is an S-shaped serrated gap, and the width of the serration gradually increases from the middle to both ends.

5. The frequency selective surface with wide stopband, low insertion loss, and high selectivity according to claim 3, characterized in that: The four corners of the intermediate metal sheet are supported and connected by a dielectric material of the same material as the dielectric layer (31) and an annular metal sheet, and the dielectric material and the dielectric layer (31) are fixed together.

6. The frequency selective surface with wide stopband, low insertion loss, and high selectivity according to claim 3, characterized in that: The lower aperture type frequency selective surface screen (3) has a through groove on one side of the annular metal sheet of the metal layer. The through groove contains a dielectric material that is integrally fixed with the dielectric layer (31) and is made of the same material as the dielectric layer (31).

7. The frequency selective surface with wide stopband, low insertion loss, and high selectivity according to claim 6, characterized in that: Both the annular metal sheet and the intermediate metal sheet are manufactured using PCB processing technology.

8. The application of the wide stopband, low insertion loss, and high selectivity frequency selective surface structure according to any one of claims 1-7, characterized in that: Application of frequency selectivity characteristics in common aperture antenna decoupling.

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