Low profile slotted frequency reconfigurable antenna

Abstract

The application discloses a low-profile slot type frequency reconfigurable antenna, comprising: a full-metal reflection baffle, an upper layer dielectric substrate and a lower layer dielectric substrate arranged in sequence; the full-metal reflection baffle is located on one side of the upper surface of the upper layer dielectric substrate; the upper surface of the upper layer dielectric substrate is provided with a first metal patch and a second metal patch; the upper surface of the lower layer dielectric substrate is printed with a feeding structure, and the lower surface is printed with two metal ground plates; the two metal ground plates are respectively provided with grooves, two groups of PIN diodes connected with the two grooves are arranged in the grooves, the conduction directions of the two groups of PIN diodes are opposite, and the two metal ground plates are electrically connected with an external single-chip microcomputer through a direct-current feeding line structure. In the application, the PIN diode is used as an electric control element, the response speed is improved, one group of voltages can be used to control the working state of the antenna through the two groups of PIN diodes placed in opposite directions, the complexity of the structure is reduced, the complexity of the control system is reduced, and the cost of the antenna is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of reconfigurable antennas, and particularly relates to a low-profile slot type frequency reconfigurable antenna. BACKGROUND

[0002] The achievements of modern wireless communication technology have greatly promoted the design of antennas. Nowadays, in some application scenarios requiring multi-band communication functions, multiple antennas are often integrated together, which not only leads to poor effects between antennas due to coupling, but also complex multi-antenna integration process. Therefore, frequency reconfigurable antennas that can realize multi-frequency switching have become the current research focus. In view of the requirements of low scattering, multi-functional radiation, reconfiguration and intelligence of radio frequency aperture, research on wideband reconfigurable antenna technology is carried out.

[0003] The frequency reconfigurable antenna is characterized in that the resonant frequency can be switched within one or more frequency bands, including single frequency and single frequency, single frequency and multi-frequency, and multi-frequency and multi-frequency. Since the resonant frequency is mainly related to the size and aperture of the structure, the resonant frequency of the antenna can be changed by adjusting the effective electrical length or the resonant length of the radiation slot. In practical applications, the most commonly used is electrical modulation, which specifically changes the antenna structure by using PIN diodes or variable capacitors to change the radiation slot or the effective electrical length, so as to reconfigure the working frequency.

[0004] In the prior art, Lei Ge et al. proposed a new type of frequency reconfigurable antenna based on a circular monopolar patch antenna in the paper "Frequency-Reconfigurable Low-Profile Circular Monopolar Patch Antenna" (IEEE Transactions on Antennas and Propagation), which includes a center-fed circular patch surrounded by four sector-shaped patches. Eight variable capacitors are introduced, and by changing the reverse bias voltage of the variable capacitors, the frequency reconfigurable effect from 1.64 GHz to 2.12 GHz is realized. However, this design has the problems of complex antenna structure, use of many electrically controlled elements, complex control system, long response time, high cost, and large influence of variable capacitor performance on voltage. SUMMARY

[0005] In order to solve the above problems in the prior art, the application provides a low-profile slot type frequency reconfigurable antenna. The technical problem to be solved by the application is solved by the following technical scheme:

[0006] A low-profile slot type frequency reconfigurable antenna, comprising: a full-metal reflection baffle, an upper layer dielectric substrate and a lower layer dielectric substrate arranged in sequence.

[0007] The full-metal reflection baffle is located on one side of the upper surface of the upper dielectric substrate;

[0008] The upper surface of the upper dielectric substrate is provided with a first metal patch and a plurality of second metal patches;

[0009] The upper surface of the lower dielectric substrate is printed with a feeding structure, and the lower surface is printed with two metal ground plates;

[0010] The two metal ground plates are arranged in parallel to form a square structure, and each of the two metal ground plates has a groove on two adjacent sides, and two groups of PIN diodes connected with the two grooves are arranged in the grooves, and a patch capacitor is connected to each end of the groove, and the patch capacitor is connected with the two grooves;

[0011] The two groups of PIN diodes are oppositely connected, and the two metal ground plates are electrically connected with an external single-chip microcomputer through a direct-current feeding line structure; the direct-current feeding line structure is connected with the second metal patch;

[0012] The first metal patch is connected with the feeding structure;

[0013] The lower dielectric substrate is provided with a first metal via hole, the first metal via hole is connected with the first metal patch, and the first metal via hole passes through the feeding structure.

[0014] In an embodiment of the present application, the number of PIN diodes in each group is one.

[0015] In an embodiment of the present application, the number of PIN diodes in each group is two;

[0016] The two PIN diodes in one group have the same conduction direction and are symmetrically arranged at positions close to the two ends of the groove;

[0017] The two PIN diodes in another group have opposite conduction directions to the two PIN diodes in one group and are symmetrically arranged between the two PIN diodes in one group.

[0018] In an embodiment of the present application, the direct-current feeding line structure comprises two inductors and two second metal via holes; the number of the second metal patches is two;

[0019] The inductors are connected with the edges of the metal ground plate adjacent to the edges of the groove, and the two inductors are located on the same side of the metal ground plate and on the two sides of the groove;

[0020] The second metal via hole is located on the lower dielectric substrate and on one side of the inductor;

[0021] The two second metal vias are connected with the two inductors respectively, and are connected with the two second metal patches respectively, and are connected with the external single-chip microcomputer.

[0022] In an embodiment of the present application, the first metal patch and the second metal patch are circular.

[0023] In an embodiment of the present application, an isolation through hole is formed in one of the metal floors;

[0024] The isolation through hole is connected with the edge of the metal floor opposite to the groove, the isolation through hole is concentric with the first metal via, and the radius is greater than the radius of the first metal via;

[0025] The feeding structure is in a strip shape, the first metal via penetrates one end of the feeding structure, and the other end of the feeding structure extends towards the corresponding position of the groove.

[0026] In an embodiment of the present application, the material of the upper layer dielectric substrate and the lower layer dielectric substrate is Arlon AD 450 material with a dielectric constant of 4.5 and a loss tangent of 0.0035;

[0027] The materials of the feeding structure, the metal floor and the full-metal reflection baffle are copper.

[0028] The beneficial effects of the present application are:

[0029] In the present application, PIN diodes are used as electric control elements, the response speed is improved, the voltage floating does not affect the switching state of the PIN diode, the performance stability is improved, through the structure of two groups of PIN diodes placed reversely, one group of voltage can be used to control the working state of the whole antenna, the complexity of the structure is reduced, the complexity of the control system is reduced, the response speed of the antenna is improved, and the cost of the antenna is reduced.

[0030] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A structure schematic diagram of a low-profile slot-type frequency reconfigurable antenna is provided for an embodiment of the present application.

[0032] Figure 2a A structure schematic diagram of the upper surface of the lower layer dielectric substrate is provided for an embodiment of the present application.

[0033] Figure 2b A structure schematic diagram of the lower surface of the lower layer dielectric substrate is provided for an embodiment of the present application.

[0034] Figure 2c A structure schematic view of an upper surface of an upper layer medium substrate provided for an embodiment of the present application is shown in the figure;

[0035] Figure 3a A reflection coefficient schematic view of a low-profile slot type frequency reconfigurable antenna provided for an embodiment of the present application working at 5.24 GHz is shown in the figure;

[0036] Figure 3b An E-plane pattern of a low-profile slot type frequency reconfigurable antenna provided for an embodiment of the present application working at 5.24 GHz is shown in the figure;

[0037] Figure 3c An H-plane pattern of a low-profile slot type frequency reconfigurable antenna provided for an embodiment of the present application working at 5.24 GHz is shown in the figure;

[0038] Figure 4a A reflection coefficient schematic view of a low-profile slot type frequency reconfigurable antenna provided for an embodiment of the present application working at 6.15 GHz is shown in the figure;

[0039] Figure 4b An E-plane pattern of a low-profile slot type frequency reconfigurable antenna provided for an embodiment of the present application working at 6.15 GHz is shown in the figure;

[0040] Figure 4c An H-plane pattern of a low-profile slot type frequency reconfigurable antenna provided for an embodiment of the present application working at 6.15 GHz is shown in the figure;

[0041] Figure 5a A reflection coefficient schematic view of a low-profile slot type frequency reconfigurable antenna provided for an embodiment of the present application working at 7.15 GHz is shown in the figure;

[0042] Figure 5b An E-plane pattern of a low-profile slot type frequency reconfigurable antenna provided for an embodiment of the present application working at 7.15 GHz is shown in the figure;

[0043] Figure 5c An H-plane pattern of a low-profile slot type frequency reconfigurable antenna provided for an embodiment of the present application working at 7.15 GHz is shown in the figure.

[0044] Explanation of reference signs:

[0045] 10 - full metal reflector; 20 - upper dielectric substrate; 21 - first metal patch; 22 - second metal patch; 30 - lower dielectric substrate; 31 - feed structure; 32 - metal ground plate; 321 - first metal ground plate; 322 - second metal ground plate; 323 - isolation via; 33 - groove; 34 - first metal via; 35 - inductor; 36 - second metal via; 37 - patch capacitor; 41 - first group of PIN diodes; 42 - second group of PIN diodes. DETAILED DESCRIPTION

[0046] The application will be further described in details below in connection with specific embodiments, but the embodiments of the application are not limited thereto.

[0047] As shown in Figure 1 , Figure 2a , Figure 2b , Figure 2c A low-profile slot-type frequency reconfigurable antenna, comprising: a full metal reflector 10, an upper dielectric substrate 20 and a lower dielectric substrate 30 arranged in sequence. The full metal reflector 10 is located on one side of the upper surface of the upper dielectric substrate 20; and the full metal reflector 10 and the upper dielectric substrate 20 have a spacing therebetween.

[0048] The upper surface of the upper dielectric substrate 20 is printed with a first metal patch 21 and a plurality of second metal patches 22; the upper surface of the lower dielectric substrate 30 is printed with a feed structure 31, and the lower surface of the lower dielectric substrate 30 is printed with two metal ground plates 32. The two metal ground plates 32 are a first metal ground plate 321 and a second metal ground plate 322.

[0049] The two metal ground plates 32 are arranged in parallel to form a square structure, and each of the two metal ground plates 32 has a groove 33 on two adjacent sides thereof, and the groove 33 is provided with two groups of PIN diodes connected with the two grooves 33, and the two ends of the groove 33 are respectively connected with a patch capacitor 37 connected with the two ends of the groove 33. The first metal ground plate 321 and the second metal ground plate 322 are rectangular in shape with the groove 33, and the two grooves 33 are respectively located on two adjacent long sides of the first metal ground plate 321 and the second metal ground plate 322. The first metal ground plate 321 and the second metal ground plate 322 have a gap therebetween, the groove 33 of the first metal ground plate 321 and the groove 33 of the second metal ground plate 322 are opposite to each other, and the first metal ground plate 321 and the second metal ground plate 322 form a square shape with a side length of P2.

[0050] The on directions of the two groups of PIN diodes are opposite, and the working frequency of the antenna is regulated by changing the bias voltage across the switching diode. The two metal floors 32 are electrically connected to the external single-chip microcomputer through a direct-current feeding structure, and the frequency reconfigurable function of the antenna is realized by switching the bias voltage on the PIN diode; the direct-current feeding structure is connected with the second metal patch 22; the first metal patch 21 is connected with the feeding structure 31; the first metal via hole 34 is arranged on the lower layer dielectric substrate 30, the first metal via hole 34 is connected with the first metal patch 21, and the first metal patch 21 is located above the first metal via hole 34; and the first metal via hole 34 penetrates through the feeding structure 31.

[0051] In the embodiment, the PIN diode is used as the electrically controlled element, the response speed is improved, the voltage floating does not affect the switching state of the PIN diode, the performance stability is improved, and the structure is simplified and the cost is saved.

[0052] Meanwhile, the voltage loaded on the switching diode can be switched in real time by the upper computer control external circuit, so that the working state of the antenna can be switched in real time, the function can be switched at any time according to the actual scene, has great application value. The present application also has the characteristics of wide frequency band coverage, flexible control, various functions, strong practicability and the like.

[0053] In a feasible implementation manner, the thickness of the upper layer dielectric substrate 20 is H1, the thickness of the lower layer dielectric substrate 30 is H2, and the side length of the two layers of dielectric substrates is P1, wherein H1 = 2.1 mm, H2 = 0.508 mm, and P1 = 55 mm. The feeding structure 31 includes a coaxial back feeding structure of the antenna and a direct-current feeding network of all PIN diodes of the antenna. The materials of the upper layer dielectric substrate 20 and the lower layer dielectric substrate 30 are Arlon AD 450 materials with a dielectric constant of 4.5 and a loss tangent of 0.0035; and the materials of the feeding structure 31, the metal floor 32 and the full-metal reflecting baffle 10 are copper.

[0054] Further, as shown in Figure 2b In the embodiment, four PIN diodes and two patch capacitors 37 are used, the number of electrically controlled elements is small, and the structure is further simplified and the cost is saved.

[0055] The two PIN diodes of one group are symmetrically arranged at positions close to two ends of the groove 33 and have the same conduction direction. The two PIN diodes of another group have opposite conduction directions to the two PIN diodes of one group and are symmetrically arranged between the two PIN diodes of one group. Specifically, the two PIN diodes of the first group of PIN diodes 41 are symmetrically arranged about the center of the groove 33, the two PIN diodes of the first group of PIN diodes 41 are placed in the same direction (have the same conduction direction), the two PIN diodes of the second group of PIN diodes 42 are symmetrically arranged about the center of the groove 33, and the two PIN diodes of the second group of PIN diodes 42 are placed in the opposite direction to the first group of PIN diodes 41. The two PIN diodes of the second group of PIN diodes 42 are located between the two PIN diodes of the first group of PIN diodes 41. The distance between the two PIN diodes of the first group of PIN diodes 41 and the center of the groove 33 is L3, and the distance between the two PIN diodes of the second group of PIN diodes 42 and the center of the groove 33 is L4. The antenna of the embodiment can realize the frequency reconfigurable function of three states in the bandwidth range of 4GHz-8GHz. The two patch capacitors 37 placed in the same direction can not affect the current distribution on both sides of the slot while ensuring the isolation of the direct current signal, thereby providing bias for the two groups of PIN diodes.

[0056] In a feasible implementation, the capacitance of the patch capacitor 37 is 10nF, the length L2 of the groove 33 is 36mm, the sum of the widths of the two grooves 33 is W2=2.4mm, L3=12.4mm, L4=8.8mm, and P2=43.2mm.

[0057] In a feasible implementation, the number of PIN diodes in each group can also be one, and the use of two PIN diodes can realize the frequency reconfigurable function of two states.

[0058] Further, as shown in Figure 2b and Figure 2c The DC feed line structure includes two inductors 35 and two second metal vias 36. The number of second metal patches 22 is two. The inductors 35 are connected to the edge of the metal ground plate 32 adjacent to the edge where the groove 33 is located, and the two inductors 35 are located on the same side of the metal ground plate 32 and on both sides of the groove 33.

[0059] The second metal via 36 is located on the lower layer dielectric substrate 30 and on one side of the inductor 35. The two second metal vias 36 are respectively connected to the two inductors 35, and the two second metal vias 36 are respectively connected to the two second metal patches 22. The two second metal vias 36 are correspondingly arranged with the two second metal patches 22, the two second metal vias 36 are located below the two second metal patches 22, and the second metal vias 36 are all connected to an external single-chip microcomputer.

[0060] In this embodiment, two inductors 35 are used to isolate the AC signal of the antenna from the DC signal of the single-chip microcomputer system.

[0061] Preferably, the inductance of the inductor 35 is 8nH, the first metal patch 21 and the second metal patch 22 are circular, and the first metal patch 21 is used to make antenna coupling feed from the back, wherein the diameter of the first metal patch 21 is D1=12.6mm, and the diameter of the second metal patch 22 is D2=9.4mm. A full-metal reflective baffle 10 is placed at a height H3 of the upper layer dielectric substrate 20, and the full-metal reflective baffle 10 is a square metal plate with a side length of 75mm and H3=2.1mm.

[0062] Further, one of the metal floors 32 is provided with an isolation through hole 323, for example, as shown in Figure 2b The second metal floor 322 is provided with an isolation through hole 323. The isolation through hole 323 is connected to the edge of the metal floor 32 opposite to the groove 33, the isolation through hole 323 is concentric with the first metal via hole 34, and the radius of the isolation through hole 323 is greater than the radius of the first metal via hole 34. The isolation through hole 323 is used to avoid the connection between the inner core of the feed structure 31 and the metal floor 32.

[0063] As shown in Figure 2a The feed structure 31 is in a long strip shape, the first metal via hole 34 passes through one end of the feed structure 31, and the other end of the feed structure 31 extends towards the corresponding position of the groove 33. The length of the feed structure 31 is L1, and the width of the feed structure 31 is W1, wherein L1=25.5mm and W1=1.3mm. In this embodiment, the coaxial back feed mode is adopted, and the full-metal reflective baffle 10 is used, which is easy for the actual installation of the antenna.

[0064] The low-profile slot-type frequency reconfigurable antenna of the present application meets the needs of different frequency band communications, can control the working state of the antenna in real time through an external circuit, avoids the coupling problem caused by the placement of different frequency band antennas, improves the variable frequency band utilization rate, and can be applied to the fields of wireless communication such as multi-frequency band base station antennas and reconfigurable antenna arrays, and has a wide range of application scenarios. The present application has the characteristics of wide frequency band coverage, flexible control, multiple functions, strong practicability, etc.

[0065] In order to verify the realizability of the single-chip microcomputer control system, the single-chip microcomputer control system is processed by using the PCB process, and the working state of the corresponding diode on the metasurface is judged through the connected LED lamp. The effect of the present application is further described in combination with the simulation experiment.

[0066] In order to illustrate the electromagnetic characteristics of the low-profile slot-type frequency reconfigurable antenna, the commercial simulation software ANSYSHFSS is used to Figure 1The unit structure is modeled and simulated.

[0067] Figure 3a 、 Figure 3b 、 Figure 3c The reflection coefficient and the radiation pattern parameter of the low-profile slot frequency reconfigurable antenna in a low-frequency working area are simulated, and the simulation result shows that the low-profile slot frequency reconfigurable antenna meets the frequency reconfigurable function in the low-frequency working area by controlling the state of the PIN diode loaded on the antenna.

[0068] Figure 4a 、 Figure 4b 、 Figure 4c The reflection coefficient and the radiation pattern parameter of the low-profile slot frequency reconfigurable antenna in a medium-frequency working area are simulated, and the simulation result shows that the low-profile slot frequency reconfigurable antenna meets the frequency reconfigurable function in the medium-frequency working area by controlling the state of the PIN diode loaded on the antenna.

[0069] Figure 5a 、 Figure 5b 、 Figure 5c The reflection coefficient and the radiation pattern parameter of the low-profile slot frequency reconfigurable antenna in a high-frequency working area are simulated, and the simulation result shows that the low-profile slot frequency reconfigurable antenna meets the frequency reconfigurable function in the high-frequency working area by controlling the state of the PIN diode loaded on the antenna.

[0070] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0071] In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0072] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0073] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0074] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0075] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A low profile slotted frequency reconfigurable antenna, characterized in that, The application relates to a full-metal reflection baffle (10), an upper-layer dielectric substrate (20) and a lower-layer dielectric substrate (30) arranged in sequence. The full-metal reflection baffle (10) is located on one side of the upper surface of the upper-layer dielectric substrate (20). A first metal patch (21) and a plurality of second metal patches (22) are arranged on the upper surface of the upper-layer dielectric substrate (20). A feeding structure (31) is printed on the upper surface of the lower-layer dielectric substrate (30), and two metal ground plates (32) are printed on the lower surface. The two metal ground plates (32) are arranged in parallel to form a square structure, and each of the two metal ground plates (32) has a groove (33) on two adjacent sides. The two groups of PIN diodes are oppositely connected, and the two metal ground plates (32) are electrically connected with an external single-chip microcomputer through a direct-current feeding line structure. The first metal patch (21) is connected with the feeding structure (31). A first metal via hole (34) is arranged on the lower-layer dielectric substrate (30) and connected with the first metal patch (21). The first metal via hole (34) passes through the feeding structure (31).

2. The low-profile slotted frequency reconfigurable antenna according to claim 1, wherein, The number of PIN diodes in each group is one.

3. The low-profile slotted frequency reconfigurable antenna according to claim 1, wherein, The number of PIN diodes in each group is two. The two PIN diodes in one group are oppositely connected and symmetrically arranged at positions close to the two ends of the groove (33). The two PIN diodes in another group are oppositely connected with the two PIN diodes in one group and symmetrically arranged between the two PIN diodes in one group.

4. The low-profile slotted frequency reconfigurable antenna according to claim 2 or 3, characterized in that, The direct-current feeding line structure comprises two inductors (35) and two second metal via holes (36). The inductors (35) are connected with the edges of the metal ground plate (32) adjacent to the edges of the groove (33). The two inductors (35) are located on the same side of the metal ground plate (32) and on the two sides of the groove (33). The second metal via holes (36) are located on the lower-layer dielectric substrate (30) and on one side of the inductors (35).

5. The low-profile slotted frequency reconfigurable antenna according to claim 4, wherein, The two second metal via holes (36) are respectively connected with the two inductors (35) and the two second metal patches (22) and connected with an external single-chip microcomputer.

6. The low-profile slotted frequency reconfigurable antenna according to claim 5, wherein, The first metal patch (21) and the second metal patch (22) are circular. One of the metal ground plates (32) is provided with an isolation through hole (323). The isolation via (323) is connected with the edge of the metal floor (32) opposite to the groove (33), the isolation via (323) is concentric with the first metal via (34), and the radius is greater than that of the first metal via (34); The feeding structure (31) is in a long strip shape, the first metal via (34) penetrates one end of the feeding structure (31), and the other end of the feeding structure (31) extends towards the corresponding position of the groove (33).

7. The low-profile slotted frequency reconfigurable antenna according to claim 6, wherein, The materials of the upper layer medium substrate (20) and the lower layer medium substrate (30) are Arlon AD 450 materials with a dielectric constant of 4.5 and a loss tangent of 0.0035; the materials of the feeding structure (31), the metal floor (32) and the full-metal reflection baffle (10) are copper.

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