Electromagnetic band gap structure

Abstract

An array comprising an electromagnetic band gap structure, the electromagnetic band gap structure comprising a dielectric substrate and a plurality of conductive patches located on the dielectric substrate for suppressing surface waves propagating on the conductive patches. The conductive patches include a first conductive patch and a second conductive patch spaced apart from and electromagnetically coupled to the first conductive patch. The shape of the second conductive patch is a polygon comprising at least three corners.

Description

TECHNICAL FIELD

[0001] The present application relates to communication systems, and in particular to an electromagnetic bandgap structure. BACKGROUND

[0002] In a half-duplex communication system, the transmitter and receiver operate on different frequency bands, which results in communication delay and spectrum congestion. A full-duplex communication system, on the other hand, supports simultaneous transmission and reception on the same frequency band, which can potentially double the achievable spectral efficiency (i.e. double the throughput). In a full-duplex system, in order to overcome the inherent self-interference between the transmit and receive signals, high isolation between the transmit and receive antennas is required. Therefore, improving the isolation between the transmit and receive antennas is an important and attractive topic for researchers, and many techniques have been researched and proposed.

[0003] For example, some solutions propose the use of defective ground structures, parasitic elements and near-field resonators. Although these solutions have shown significant isolation improvement, electromagnetic bandgap (EBG) structures and frequency-selective surface (FSS) structures have recently also attracted attention. However, such solutions often have a narrow working frequency band, and the isolation improvement is not more than 10 dB. Another disadvantage of existing solutions is that some isolation structures are bulky, require multi-layer design and vias, resulting in more complex manufacturing and low cost-effectiveness. SUMMARY

[0004] According to a first aspect of the application, there is provided an array comprising an electromagnetic bandgap structure. The electromagnetic bandgap structure comprises: a dielectric substrate; a plurality of electrically-conductive patches on the dielectric substrate for suppressing surface waves propagating on the electrically-conductive patches, the plurality of electrically-conductive patches comprising: a first electrically-conductive patch; a second electrically-conductive patch spaced apart from and electromagnetically coupled to the first electrically-conductive patch, wherein the second electrically-conductive patch is in the shape of a polygon comprising at least three corners. As a result, surface currents can accumulate and concentrate at each corner of the polygon patch, which can lead to a stopband of the electromagnetic bandgap structure.

[0005] The dielectric substrate and the plurality of electrically-conductive patches can collectively form a frequency-selective surface.

[0006] The polygon can comprise no more than 72 corners. The polygon can comprise no more than 16 corners. When the polygon approaches the shape of a circle, the suppression of surface currents can be weakened. Therefore, according to some embodiments, it can be useful to set an upper limit on the number of corners of the polygon.

[0007] The polygon can be an octagon including 16 corners. The 16 corners include 8 inner corners and 8 outer corners, each inner corner being 135° and each outer corner being 90°.

[0008] The outer boundary of the first conductive patch can be square shaped.

[0009] The conductive patches can be co-planar. According to some embodiments, the electromagnetic bandgap structure can not include any vias. Thus, the electromagnetic bandgap structure can be compatible with PCB technology and relatively easy to manufacture. For example, according to some embodiments, the dielectric substrate can include a top layer of a printed circuit board.

[0010] The first conductive patch can include an opening shaped to correspond to a shape of the second conductive patch. The second conductive patch can be located within the opening, thereby forming a slot between edges of the opening and edges of the second conductive patch.

[0011] The array can include a plurality of electromagnetic bandgap structures, wherein the plurality of electromagnetic bandgap structures includes the electromagnetic bandgap structure, adjacent electromagnetic bandgap structures of the plurality of electromagnetic bandgap structures being spaced apart from each other by a gap.

[0012] According to another aspect of the present application, there is provided a full-duplex transceiver, comprising: a transmitter for transmitting electromagnetic waves at an operating frequency; a receiver for receiving electromagnetic waves at the operating frequency; an electromagnetic bandgap structure located between the transmitter and the receiver and configured to reduce interference between the transmitter and the receiver, the electromagnetic bandgap structure comprising: a dielectric substrate; a plurality of conductive patches located on the dielectric substrate and configured to suppress surface waves propagating on the conductive patches, the plurality of conductive patches including: a first conductive patch; a second conductive patch spaced apart from and electromagnetically coupled to the first conductive patch, wherein the second conductive patch is shaped as a polygon including at least three corners.

[0013] The electromagnetic bandgap structure is configured to provide an isolation of up to 14.8 dB between the transmitter and the receiver. The electromagnetic bandgap structure is configured to provide an isolation of up to 14.8 dB between the transmitter and the receiver over a fractional bandwidth of 31%. This isolation represents a substantial improvement over existing electromagnetic bandgap structures and frequency selective surface structures.

[0014] According to another aspect of the present application, there is provided a method of tuning an electromagnetic bandgap structure. The electromagnetic bandgap structure comprises: a dielectric substrate; a plurality of electrically-conductive patches on the dielectric substrate for suppressing surface waves propagating on the electrically-conductive patches, the plurality of electrically-conductive patches comprising: a first electrically-conductive patch; a second electrically-conductive patch spaced apart from and electromagnetically coupled to the first electrically-conductive patch, wherein the second electrically-conductive patch is in the shape of a polygon comprising at least three corners. The method comprises: adjusting one or more of: a spacing between the first electrically-conductive patch and the second electrically-conductive patch; an angle defined by each corner; a number of corners in the polygon.

[0015] The electromagnetic bandgap structure can be included in an array of electromagnetic bandgap structures, wherein the electromagnetic bandgap structure is spaced apart from an adjacent electromagnetic bandgap structure by a gap; the adjusting can comprise adjusting one or more of: the spacing between the first electrically-conductive patch and the second electrically-conductive patch; the angle defined by each corner; the gap; the number of corners in the polygon.

[0016] Thus, the operating frequency of the electromagnetic bandgap structure can be tuned according to the application in which the electromagnetic bandgap structure is used.

[0017] This summary of the application does not necessarily describe all aspects. Other aspects, features, and advantages will be apparent to those of ordinary skill in the art upon reviewing the description of the specific embodiments below. BRIEF DESCRIPTION OF DRAWINGS

[0018] Embodiments of the application will now be described in detail in connection with the accompanying drawings, in which:

[0019] Figure 1A is a top view of an electromagnetic bandgap structure according to one embodiment of the application;

[0020] Figure 1B is a perspective view of an electromagnetic bandgap structure according to one embodiment of the application Figure 1A

[0021] Figure 2A is a schematic diagram of a high frequency structure simulator setup according to one embodiment of the application;

[0022] Figure 2B is a perspective view of an electromagnetic bandgap structure according to one embodiment of the application Figure 1A and Figure 1B is a dispersion plot of an electromagnetic bandgap structure according to one embodiment of the application;

[0023] Figure 3A is a top view of a suspended transmission line above an array of electromagnetic bandgap structures according to one embodiment of the application;

[0024] Figure 3B is a top view of a suspended transmission line above an array of electromagnetic bandgap structures according to one embodiment of the application;​Figure 3A side view of a suspended transmission line above an array of EBG structures of

[0025] Figure 4 Figure 3A and Figure 3B graph of scattering parameter versus frequency for an embodiment of

[0026] Figure 5 graph of scattering parameter versus frequency for two antennas separated by an air dielectric according to an embodiment of the invention;

[0027] Figure 6 graph of scattering parameter versus frequency for two antennas separated by an array of EBG structures according to an embodiment of the invention; Figure 1A and Figure 1B graph of scattering parameter versus frequency for two antennas separated by an array of EBG structures according to an embodiment of the invention;

[0028] Figure 7A top view of an array of EBG structures located between two antennas according to an embodiment of the invention;

[0029] Figure 7B graph of scattering parameter versus frequency for an embodiment of Figure 7A

[0030] Figure 8A shows surface currents through an EBG structure according to an embodiment of the invention; Figure 1A and Figure 1B

[0031] Figure 8B shows surface currents through an array of EBG structures according to an embodiment of the invention. Figure 7A DETAILED DESCRIPTION

[0032] The present invention aims to provide a novel electromagnetic bandgap structure, thereby providing improved isolation over a wide bandwidth. While various embodiments of the present invention are described below, the present invention is not limited to these embodiments, and variations of these embodiments are well within the scope of the present invention as defined by the appended claims.

[0033] Generally, embodiments of the present invention relate to an electromagnetic bandgap (EBG) structure comprising a dielectric substrate and a plurality of electrically conductive patches located on the dielectric substrate and configured to suppress surface waves propagating on the electrically conductive patches. The electrically conductive patches comprise at least two patches, in particular at least one first electrically conductive patch and at least one second electrically conductive patch spaced apart from and electromagnetically coupled to the first electrically conductive patch. The second electrically conductive patch is shaped as a polygon comprising at least three corners.​​​​

[0034] According to some embodiments, the dielectric substrate and the plurality of electrically conductive patches collectively comprise a frequency selective surface.

[0035] According to one particular embodiment described in further detail below, the polygon includes 16 corners (i.e., the polygon is octagonal). Generally, the closer the polygon is to the shape of a circle, the weaker the suppression. Thus, according to some embodiments, the polygon can include no more than 72 corners.

[0036] According to some embodiments, the electromagnetic bandgap structure with the frequency selective surface can suppress surface waves by up to 14.8 dB across its entire operational frequency band. According to some embodiments, the operational frequency band can be a 1.1 GHz bandwidth from 3.1 GHz to 4.2 GHz.

[0037] According to some embodiments, the electromagnetic bandgap structure can be implemented between two antennas (e.g., a transmit antenna and a receive antenna) in a full-duplex transceiver. Thus, the electromagnetic bandgap structure can reduce the mutual coupling between the two antennas.

[0038] Embodiments of the electromagnetic bandgap structure described herein can also be implemented in a planar structure that is fully compatible with PCB technology and relatively easy to manufacture.

[0039] Turning to Figure 1A and Figure 1B different views of an electromagnetic bandgap (EBG) structure 100 according to one embodiment of the present application. The EBG structure 100 includes a dielectric substrate 10 having a thickness d, on which a frequency selective surface (FSS) is provided that includes electrically conductive patches 20 and 30 that are electromagnetically coupled. The electrically conductive patch 20 includes a square boundary on which a recess is formed that is octagonal in shape. The electrically conductive patch 30 is octagonal in shape and is positioned within the correspondingly shaped recess of patch 20. A slot 12 is formed between the outer boundary of patch 30 and the inner boundary of patch 20 (i.e., the boundary formed by the recess of patch 20). The octagonal patch 30 includes eight inner corners 32 and eight outer corners 34 (for a total of 16 corners).

[0040] The length of the EBG structure 100 is L = 35.5 mm. The side length of the patch 20 is W = 34.34 mm, while the octagonal patch 30 has dimensions a = 30.61 mm, b = 21.65 mm, with an internal angle 32 of 135° and an external angle 3 of 90°. The slot 12 has a dimension s = 0.25 mm. The patches 20 and 30 are patterned on a ground dielectric substrate 10 with a dielectric constant (DK) of 3.66, a loss tangent of 0.004, and a dielectric thickness of d = 1.524 mm. As will be appreciated by those skilled in the art, the EBG structure will have different dimensions depending on the particular desired properties of the EBG structure (e.g., desired stopband).

[0041] As noted above, one of the main properties of an EBG structure is the ability to suppress surface waves. Thus, an EBG can act as a stopband by eliminating the interfering surface currents generated by adjacent elements, thereby improving isolation and reducing the coupling effects between elements. The stopband of an EBG structure can be generated using numerical simulation tools. The dispersion diagram of the EBG structure 100 is shown in Figure 2A and extracted using a finite element high-frequency structure simulator (HFSS) solver.

[0042] The HFSS setup shown in Figure 2A was used to extract the bandgap of the EBG structure 100. The computational domain and boundary conditions (irreducible Brillouin zone) of the EBG structure 100 are shown in the figure. Figure 2B The dispersion diagram shows the relationship between the wave number and the frequency and gives the propagation modes that exist between different modes and one or more bandgaps. The gap between the upper limit of one propagation mode and the intersection with the next propagation mode represents the region in which the EBG structure 100 prevents any propagation. An electromagnetic bandgap between 3.1 GHz and 4.2 GHz was observed in the EBG structure 100, as shown in Figure 2B .

[0043] The operating frequency (i.e., the bandgap) of the EBG structure 100 can be adjusted by controlling the slot 12 between the patches 20 and 30, and / or the angles defined by the corners 32 and 34 of the patch 30, and / or the number of corners (i.e., the shape of the polygon). The operating frequency can also be tuned based on the gap separating adjacent EBG structures in an array of EBG structures, as described in further detail below in connection with Figure 3A . The EBG structure 100 can operate over a wide range of frequencies, particularly low frequencies and millimeter waves of 5G frequencies.

[0044] Turning to Figure 3AFig. 6 shows the suspended line test with a 3x3 array 200 of EBG structures 100. The EBG structures 100 are printed on a square PCB substrate 150 with a length of 141.284 mm, a dielectric constant of 3.66, and a thickness = 1.524 mm. As shown in Fig. 6, a suspended transmission line 160 with a width of 5.72 mm is placed above the array 200 with a spacing of 0.5 mm. Adjacent EBG structures 100 are spaced apart by a gap of 1.16 mm. Figure 3B

[0045] Figure 4 Fig. 7 shows the simulated transmission coefficients of the suspended transmission line 160 placed above the array 200. The simulation results show that the EBG structures 100 act as a stopband to suppress surface waves within the bandgap frequency of the EBG structures 100. Figure 4 The results shown in Fig. 7 are in perfect agreement with the results obtained from the dispersion diagram shown in Fig. 5. Figure 2B The dispersion diagram shows a stopband of about 1.1 GHz (3.11 GHz to 4.21 GHz) and gives a fractional bandwidth of about 31%.

[0046] The degree of isolation enhancement that can be achieved by the EBG structures 100 is also investigated. In this scenario, two antennas are considered and tested for three cases. In all three cases, a constant spacing of 141.284 mm is used between the antennas.

[0047] • Case #1 : Air medium is used between the two antennas 50 and 60, resulting in an isolation of 29 dB as shown in Fig. 8. Figure 5

[0048] • Case #2: A substrate 70 with a dielectric constant of 3.66 is inserted between the two antennas 50 and 60, resulting in an isolation of 26 dB as shown in Fig. 9. Figure 6

[0049] • Case #3: A 3x3 array 200 of EBG structures 100 is inserted between the two antennas 50 and 60 as shown in Fig. 10. Figure 7A Figure 7B The s-parameter results shown in Fig. 10 demonstrate that the EBG structures 100 act as a stopband throughout its bandgap, rendering surface wave propagation between the antennas 50 and 60 negligible. The isolation between the antennas 50 and 60 is enhanced, with a minimum of 40.9 dB.

[0050] Table 1 below summarizes the results of the three test cases. It can be seen that the average isolation difference between Case #3 and Case #1 and Case #2 is 12 dB and 14.4 dB, respectively.

[0051] Table 1

[0052] ​​​​

[0053] It can be seen that embodiments of the EBG structure described herein have the advantage that by accumulating and concentrating the generated surface currents in the outer and inner corners of the polygonal patches (e.g., corners 32 and 34 of patch 30), the propagation of surface waves on the surface of the EBG structure can be suppressed, as shown in Figure 8A and Figure 8B This creates a bandgap region, over which propagation is negligible.

[0054] As mentioned above, although the EBG structure 100 includes patches 30 shaped as octagons, the present application can extend to EBG structures having polygonal patches of any other suitable shape, including triangular patches, square patches, pentagonal patches, hexagonal patches, etc. In this case, according to some embodiments, it is expected that acceptable isolation can be achieved by patches having 36 sides, in particular defining angles of 170°.

[0055] Accordingly, embodiments of the EBG structure described herein can be used to reduce coupling between any highly coupled components, and can be used in wideband frequency applications requiring high isolation. Moreover, due to the planar nature of the EBG structure, certain embodiments of the EBG structure described herein can be easily incorporated into PCB technology.

[0056] The described EBG structure can be particularly suitable for full-duplex 5G and 6G applications, and can be easily inserted between transceiving antennas to reduce mutual coupling. Moreover, different shaped printed antennas or components can benefit from the higher isolation achieved by the EBG structure described herein.

[0057] The word “a” or “an” when used in the context of the term “comprising” or “containing” in the claims and / or the specification means “one,” but also is consistent with “one or more” in the context of the specification. Similarly, the words “another” and “a second” mean at least a second or more unless context clearly indicates otherwise.

[0058] The terms “coupled to,” “coupled with,” or “connected to” as used herein can have several different meanings depending on the context in which these terms are used. For example, as used herein, the terms “coupled to,” “coupled with,” or “connected to” can indicate that two elements or devices are directly connected to one another, or by way of one or more intermediate elements or devices, by mechanical elements, depending on the particular context. The term “and / or” as used herein when used in a list of items, means that any one or more of the items in that list can be employed by the application.

[0059] As used herein, a reference to "about" or "approximately" a value or "substantially" equal to a value means within ±10% of the value.

[0060] While the application has been described in connection with specific embodiments thereof, it will be understood that it is not intended to be limited to these embodiments, and that modifications, alterations, and variations can be made by persons skilled in the art in the practice thereof having the benefit of the present disclosure, without departing from the scope of the present application.

[0061] It is also contemplated that any part or all of any aspects or embodiments of the present disclosure discussed in this specification can be implemented together or separately.

Claims

1. An array comprising an electromagnetic bandgap structure, characterized in that, The electromagnetic bandgap structure includes: Dielectric substrate; A plurality of conductive patches located on the dielectric substrate are used to suppress surface waves propagating on the conductive patches, the plurality of conductive patches comprising: First conductive patch; A second conductive patch is spaced apart from and electromagnetically coupled to the first conductive patch, wherein the second conductive patch is a polygon with at least three corners.

2. The array according to claim 1, characterized in that, The dielectric substrate and the plurality of conductive patches together constitute a frequency selective surface.

3. The array according to claim 1 or 2, characterized in that, The polygon has no more than 72 corners.

4. The array according to claim 1 or 2, characterized in that, The polygon has no more than 16 corners.

5. The array according to claim 1 or 2, characterized in that, The polygon is an octagon containing 16 angles.

6. The array according to claim 5, characterized in that, The 16 angles include 8 interior angles and 8 exterior angles, each interior angle being 135° and each exterior angle being 90°.

7. The array according to any one of claims 1 to 6, characterized in that, The outer boundary of the first conductive patch is square.

8. The array according to any one of claims 1 to 7, characterized in that, The conductive patches are coplanar.

9. The array according to any one of claims 1 to 8, characterized in that, The first conductive patch includes an opening whose shape corresponds to that of the second conductive patch; The second conductive patch is located within the opening, thereby forming a groove between the edge of the opening and the edge of the second conductive patch.

10. The array according to any one of claims 1 to 9, characterized in that, The electromagnetic bandgap structure does not include any vias.

11. The array according to any one of claims 1 to 10, characterized in that, The dielectric substrate includes the top layer of the printed circuit board.

12. The array according to any one of claims 1 to 11, characterized in that, The array includes multiple electromagnetic bandgap structures, wherein the multiple electromagnetic bandgap structures include the electromagnetic bandgap structure, and adjacent electromagnetic bandgap structures in the multiple electromagnetic bandgap structures are spaced apart from each other by gaps.

13. A full-duplex transceiver, characterized in that, include: A transmitter is used to emit electromagnetic waves at its operating frequency. A receiver for receiving electromagnetic waves at the operating frequency; An electromagnetic bandgap structure located between the transmitter and the receiver is used to reduce interference between the transmitter and the receiver. The electromagnetic bandgap structure includes: Dielectric substrate; A plurality of conductive patches located on the dielectric substrate are used to suppress surface waves propagating on the conductive patches, the plurality of conductive patches comprising: First conductive patch; A second conductive patch is spaced apart from and electromagnetically coupled to the first conductive patch, wherein the second conductive patch is a polygon with at least three corners.

14. The full-duplex transceiver according to claim 13, characterized in that, The electromagnetic bandgap structure is used to provide isolation of up to 14.8 dB between the transmitter and the receiver.

15. The full-duplex transceiver according to claim 13 or 14, characterized in that, The electromagnetic bandgap structure is used to provide isolation of up to 14.8 dB between the transmitter and the receiver over a 31% fractional bandwidth.

16. The full-duplex transceiver according to any one of claims 13 to 15, characterized in that, The dielectric substrate and the plurality of conductive patches together constitute a frequency selective surface.

17. The full-duplex transceiver according to any one of claims 13 to 16, characterized in that, The polygon has no more than 72 corners.

18. The full-duplex transceiver according to any one of claims 13 to 16, characterized in that, The polygon has no more than 16 corners.

19. A tuning method for an electromagnetic bandgap structure, characterized in that, The electromagnetic bandgap structure includes: Dielectric substrate; A plurality of conductive patches located on the dielectric substrate are used to suppress surface waves propagating on the conductive patches, the plurality of conductive patches comprising: First conductive patch; The second conductive patch is spaced apart from and electromagnetically coupled to the first conductive patch, wherein the shape of the second conductive patch is a polygon including at least three corners; The method includes: Adjust one or more of the following: The spacing between the first conductive patch and the second conductive patch; The angle defined for each corner; The number of angles in the polygon.

20. The method according to claim 19, characterized in that, The electromagnetic bandgap structure is included in an electromagnetic bandgap structure array, wherein the electromagnetic bandgap structure is separated from adjacent electromagnetic bandgap structures by gaps; The adjustments include adjusting one or more of the following: The spacing between the first conductive patch and the second conductive patch; The angle defined for each angle; The gap; The number of angles in the polygon.

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