High-gain ultra-wideband antenna based on metamaterial frequency selective surface

Abstract

The utility model discloses a high-gain ultra-wideband antenna based on a metamaterial frequency selective surface, and relates to the technical field of electromagnetic materials and antenna microwaves. The high-gain ultra-wideband antenna of the utility model is composed of an ultra-wideband microstrip antenna and a frequency selective surface. The ultra-wideband microstrip antenna comprises a top layer, a middle layer and a bottom layer grounding plate; the top layer is composed of a circular radiation patch and a rectangular microstrip feeder line; the middle layer is a first dielectric substrate; the frequency selective surface is formed by periodically arranging a plurality of surface unit structures; the surface unit structure is composed of a metal unit layer and a second dielectric substrate, a circular groove is formed in the center of the metal unit layer, four right-angle grooves are evenly distributed around the circular groove, and four right-angle wire grooves are correspondingly formed outside the four right-angle grooves. Through the loaded frequency selection surface structure, the back radiation loss of the ultra wide band antenna can be reduced in the UWB (3.1 GHz-10.6 GHz) frequency band, the antenna gain can be effectively improved, and the ultra wide band antenna has the characteristics of miniaturization and low cost.

Description

Technical Field

[0001] The utility model belongs to the technical field of electromagnetic materials and antenna microwaves, and in particular relates to a high-gain ultra-wideband antenna based on a metamaterial frequency selective surface. Background Art

[0002] Frequency Selective Surfaces (FSS) are periodically arranged metal or groove structures that can exhibit specific stopband or passband characteristics under the excitation of incident electromagnetic waves. Therefore, this technology is widely used in fields such as filters, polarizers, absorbers and antenna design.

[0003] Ultra-Wideband (UWB) technology can effectively overcome the limitations of traditional communication technologies (such as narrow bandwidth, slow data speed, multipath fading and interference). According to the UWB transmission regulations issued by the Federal Communications Commission (FCC) in 2002, the general operating frequency band is mainly concentrated in the frequency band of 3.1GHz to 10.6GHz, and its output power spectrum density peak is -41.3dBm / MHz. Among them, UWB microstrip antennas are highly favored for their planar structure, small size and easy manufacturing. The optimization of its radiation characteristics will make it an ideal choice for application fields.

[0004] The design and application of FSS have been extended to UWB systems. By loading FSS, the antenna gain can be significantly increased and the back radiation can be minimized, which is crucial to improving the performance of UWB technology. Although most UWB antenna designs are currently designed to achieve the omnidirectional radiation pattern required by traditional communication systems, in some usage scenarios, antenna designs with unidirectional radiation characteristics are more in line with the needs of practical applications. Therefore, further research and development of the application of UWB-FSS technology in optimizing antenna performance is of great significance. Utility Model Content

[0005] In response to the problems of low antenna gain caused by the omnidirectional radiation of the current ultra-wideband antenna and interference caused by back radiation in specific application scenarios, the utility model provides a high-gain ultra-wideband antenna based on a metamaterial frequency selective surface, which is a small frequency selective surface used to improve the gain of the ultra-wideband antenna and reduce back radiation to meet actual engineering applications and needs.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A high-gain ultra-wideband antenna based on a metamaterial frequency selective surface, the high-gain ultra-wideband antenna is composed of an ultra-wideband microstrip antenna and a frequency selective surface; the ultra-wideband microstrip antenna is arranged directly above the frequency selective surface; the distance is half of the wavelength of the frequency value corresponding to the zero-point value of the reflection phase of the frequency reflection surface, which can be adjusted according to the actual application scenario. The number of surface unit structures of the frequency selective surface depends on the specific ultra-wideband microstrip antenna, and the overall structure remains compact and is placed on the same complete substrate.

[0008] The ultra-wideband microstrip antenna comprises a top layer, a middle layer and a bottom ground plate; the top layer is composed of a circular radiation patch and a rectangular microstrip feeder; the middle layer is a rectangular first dielectric substrate;

[0009] The bottom ground plate is a bottom patch formed by cutting corners of a rectangular patch and opening rectangular grooves on the long sides after the corner cutting;

[0010] The frequency selective surface is composed of a plurality of surface unit structures arranged periodically; the surface unit structure is composed of a metal unit layer and a second dielectric substrate, and the metal unit layer is arranged on the second dielectric substrate;

[0011] A circular groove is opened in the center of the metal unit layer, and four right-angle grooves are evenly distributed around the circular groove, and the four right-angle grooves are symmetrically distributed about the diagonal line of the metal unit layer; four right-angle line grooves are correspondingly arranged outside the four right-angle grooves.

[0012] Furthermore, the four right-angled grooves are right-angled triangular grooves, whose hypotenuses are arc-shaped, the apex of the right angle is located on the diagonal of the metal unit layer, the right angle side is parallel to the right angle side of the metal unit layer, and the center of the arc hypotenuse coincides with the center of the circular groove.

[0013] Furthermore, the four right-angle wire grooves are chamfered wire grooves, the slope value of the bevel is 45°, and the length of the chamfered right-angle side is 0.5mm; the single side length of the right-angle wire groove is 3.65mm.

[0014] Furthermore, the radius of the circular radiation patch is 5 mm; the length of the rectangular microstrip feed line is 11 mm and the width is 2.6 mm.

[0015] Further, the bottom ground plate is a bottom patch formed by cutting corners of a rectangular patch and opening rectangular grooves on the long sides after the corner cutting;

[0016] The two cut corners of the bottom patch are cut at 45 degrees and have a length of 4 mm; a rectangular groove with a length of 3 mm and a width of 1.75 mm is dug in the middle of the long side of the cut corner of the bottom ground plate.

[0017] Furthermore, the side length L1 of the metal unit layer is 12 mm; the side length L2 of the second dielectric substrate is 11.5 mm; the radius R1 of the circular groove is 3.5 mm;

[0018] Furthermore, the metal unit layer and the second dielectric substrate are both rectangular.

[0019] Furthermore, the thickness of the first dielectric substrate and the second dielectric substrate is 1.6 mm, and both the first dielectric substrate and the second dielectric substrate use FR4 (loss tangent 0.025, relative dielectric constant 4.4); the distance between the ultra-wideband microstrip antenna and the frequency selective surface is half the wavelength of the frequency value corresponding to the zero point value of the reflection phase of the frequency reflection surface.

[0020] Furthermore, the frequency selective surface is composed of a number of surface unit structures arranged periodically; a 3×3 or larger periodic array can be formed according to the antenna size.

[0021] The first dielectric substrate and the second dielectric substrate are both made of FR4, with a loss tangent of 0.025 and a relative dielectric constant of 4.4.

[0022] Compared with the prior art, the utility model has the following advantages:

[0023] 1. The accuracy of the frequency selective surface working frequency band is improved. The transmission coefficient range that meets the requirements (3.01GHz~10.63GHz) is only about 1.6% different from the UWB (3.1GHz~10.6GHz) frequency band, which effectively reduces unnecessary interference with electromagnetic waves in other frequency bands.

[0024] 2. This design meets the needs of miniaturization, and uses a minimum 3×3 (36mm×36mm) array of frequency selective surfaces, which can increase the average gain of the ultra-wideband antenna by about 128.57%, effectively reducing the cost. In addition, for antennas of different sizes, the density of the array can be increased to improve the stability of the gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a front view of a surface unit structure in the frequency selective surface;

[0026] Figure 2 It is a bottom view of a surface unit structure in the frequency selective surface;

[0027] Figure 3 It is a rear view of a surface unit structure in the frequency selective surface;

[0028] Figure 4 It is a three-dimensional diagram of a surface unit structure in a frequency selective surface;

[0029] Figure 5It is a schematic diagram of the dimensions of the surface unit structure;

[0030] Figure 6 It is a schematic diagram of a frequency selective surface formed by periodically arranging a 3×3 surface unit structure;

[0031] Figure 7 It is a front view schematic diagram of the ultra-wideband microstrip antenna structure;

[0032] Figure 8 It is a schematic diagram of the back side of the ultra-wideband microstrip antenna structure;

[0033] Fig. 9 It is a top view of the 3×3 frequency selective surface loaded under the ultra-wideband microstrip antenna;

[0034] Fig.10 It is a side view of a 3×3 frequency selective surface loaded under an ultra-wideband microstrip antenna;

[0035] Fig.11 The following are schematic diagrams of the simulation results of the frequency selective surface unit in HFSS software: (a) schematic diagram of simulation analysis; (b) schematic diagram of transmission coefficient, reflection coefficient and reflection phase curves;

[0036] Fig.12 It is the transmission coefficient variation curve of the frequency selective surface; (a) transmission coefficient at different polarization angles (b) transmission coefficient at different incident angles;

[0037] Fig.13 is the real and imaginary parts of the effective dielectric constant and magnetic permeability. Schematic diagram (a) Equivalent dielectric constant ε (b) Equivalent magnetic permeability μ;

[0038] Fig.14 It is a schematic diagram of the return loss curve of the ultra-wideband microstrip antenna before and after loading the frequency selective surface;

[0039] Fig.15 The radiation diagrams of the ultra-wideband microstrip antenna before and after loading the frequency selective surface at 4.5 GHz, 7 GHz and 9.5 GHz in the XZ plane (E plane), XY plane (H plane) and YZ plane are compared;

[0040] Fig.16 It is a comparison diagram of the gain change curve of the antenna before and after loading the frequency selective surface;

[0041] Fig.17 This is a comparison of the gain change curves of the ultra-wideband microstrip antenna before and after loading the frequency selective surface;

[0042] Figure numerals: 1. ultra-wideband microstrip antenna; 2. frequency selective surface; 3. circular radiation patch; 4. rectangular microstrip feed line; 5. first dielectric substrate; 6. bottom patch; 7. metal unit layer; 8. second dielectric substrate; 9. circular slot; 10. right-angle slot; 11. right-angle line slot. DETAILED DESCRIPTION

[0043] In order to further illustrate the technical solution of the present utility model, the present utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0044] Example 1

[0045] A high-gain ultra-wideband antenna based on a metamaterial frequency selective surface:

[0046] The high-gain ultra-wideband antenna is composed of an ultra-wideband microstrip antenna 1 and a frequency selective surface 2; and the ultra-wideband microstrip antenna 1 is arranged directly above the frequency selective surface 2, such as Fig. 9 and Fig.10 The top view and side view of the 3×3 frequency selective surface loaded under the ultra-wideband microstrip antenna are shown;

[0047] The ultra-wideband microstrip antenna 1 comprises a top layer, a middle layer and a bottom ground plate, such as Figure 7 and 8 As shown, the top layer is composed of a circular radiation patch 3 and a rectangular microstrip feed line 4; the middle layer is a rectangular first dielectric substrate 5; the bottom ground plane is a bottom patch 6 formed by cutting a rectangular patch and opening a rectangular groove on the long side after cutting the corners; wherein the performance of the antenna is optimized by cutting the corners and digging grooves on the ground plane, so that the antenna meets the ultra-wideband working frequency band. The antenna structure is simple and easy to manufacture. The radius of the circular radiation patch 3 is 5mm; the length of the rectangular microstrip feed line 4 is 11mm and the width is 2.6mm. The two cut corners of the bottom patch 6 are 45 degrees and the length is 4mm; a rectangular groove with a length of 3mm and a width of 1.75mm is dug in the middle of the long side of the cut corner of the bottom ground plane.

[0048] The frequency selective surface 2 is composed of several surface unit structures arranged in a 3×3 periodic pattern; Figure 6 As shown; the surface unit structures are periodically arranged and combined at certain intervals to form a frequency selective surface 2. The surface unit structures are in the same horizontal plane and are closely connected. Depending on the size of the microstrip antenna, frequency selective surfaces of different periods can be formed to match it.

[0049] The surface unit structure is composed of a metal unit layer 7 and a second dielectric substrate 8. Figure 1 The front view of the surface unit structure is shown; and the metal unit layer 7 is arranged on the second dielectric substrate 8; Figure 2As shown in the top view of the surface unit structure; the metal unit layer 7 and the second dielectric substrate 8 are both rectangular (square); the second dielectric substrate 8 is represented by gray, and the thickness of the substrate used is FR4 (loss tangent 0.025, relative dielectric constant 4.4) with a thickness of H1=1.6mm; the material of the metal unit layer 7 is copper, represented by light yellow, and a circular groove 9 is opened in the center of the metal unit layer 7, and four right-angle grooves 10 are evenly distributed around the circular groove 9, and the four right-angle grooves 10 are symmetrically distributed about the diagonal of the metal unit layer 7; the four right-angle grooves 10 are right-angled triangular grooves, and their hypotenuses are arc-shaped, the vertex of the right angle is located on the diagonal of the metal unit layer 7, the right-angle side is parallel to the right-angle side of the metal unit layer 7, and the arc center of the arc hypotenuse coincides with the center of the circular groove 9. Four right-angle grooves 11 are correspondingly arranged outside the four right-angle grooves 10. The four right-angle grooves 11 are chamfered angle grooves, the slope value of the chamfer is 45°, and the length W2 of the chamfered right angle side is 0.5mm; the single side length L3 of the right-angle groove 11 is 3.65mm. Figure 5 As shown, the side length L2 of the metal unit layer 7 is 11.5 mm; the side length L1 of the second dielectric substrate 8 is 12 mm; and the radius R1 of the circular groove 9 is 3.5 mm;

[0050] like Figure 5 The design of the single-layer frequency selective surface shown can provide a stopband response over the entire ultra-wideband band with different phases to have the ability to enhance the gain of planar ultra-wideband antennas. The proposed unit covers one side of a single dielectric substrate and has a compact size of 12mm×12mm.

[0051] The surface unit structure size parameters of the ultra-wideband microstrip antenna 1 and the frequency selective surface 2 are shown in Table 1:

[0052] Table 1

[0053]

[0054]

[0055] The thickness of the first dielectric substrate 5 and the second dielectric substrate 8 is 1.6 mm. Fig. 9 and 10 As shown, the distance between the ultra-wideband microstrip antenna 1 and the frequency selective surface 2 is half of the wavelength of the frequency value corresponding to the zero-point value of the reflection phase of the frequency selective surface.

[0056] Example 2 Principle and simulation results:

[0057] The frequency selective surface is simulated and analyzed using HFSS (High Frequency Structure Simulator) software. By setting ideal boundary conditions and upper and lower ports, the surface unit structure is simulated and analyzed, and the scattering S parameters of the frequency selective surface are obtained. Fig.11 shown.

[0058] observe Fig.11 From the curve in (b), we can see that within the ultra-wideband operating frequency band (3.1GHz~10.6GHz), the reflection coefficient of the frequency selective surface fluctuates at 0dB, and the transmission coefficient is less than -10dB within 3.01GHz~10.63GHz. It can reflect the electromagnetic waves radiated by the antenna in the ultra-wideband operating frequency band, while transmitting other frequency bands, meeting the requirements of enhancing antenna gain. In order to achieve the best effect of the proposed antenna gain, the electromagnetic waves radiated by the antenna and the reflected waves of the frequency selective surface FSS should be in phase, Fig.11 In (b), the reflection phase decreases linearly with frequency, meeting the in-phase requirement, and reaches zero at 6.82 GHz.

[0059] Example 3

[0060] By extracting the aforementioned S parameters of transmission coefficient and reflection coefficient ( Fig.11 ), the characteristics of the frequency selective surface are analyzed, and the equivalent dielectric constant and permeability of the frequency selective surface are obtained. The real and imaginary parts of the effective dielectric constant and permeability are as follows: Fig.13 As shown, it can be clearly seen that the real part of the equivalent dielectric constant and permeability of the frequency selective surface structure within 7-10GHz are both negative, so the frequency selective surface can be considered as a metamaterial, because its dielectric constant and permeability are both negative in a specific range, and it is also called DNG (Double Negative) material. DNG material is suitable for producing narrow beam radiation in the far field and can be used to make small, high and reconfigurable antennas. In addition, the imaginary part of the frequency selective surface FSS unit is negative or close to zero in the entire ultra-wideband microstrip antenna UWB frequency band. Therefore, the loss of this metamaterial to electromagnetic wave propagation will be very small.

[0061] Example 4

[0062] When the frequency selective surface is excited by an incident wave, it can exhibit a stopband or passband response, and their behavior depends not only on the frequency of the electromagnetic wave, but also on the polarization direction and incident angle of the electromagnetic wave. In order to study the polarization sensitivity of the proposed frequency selective surface FSS design, the electric and magnetic fields are rotated in different directions at normal incident angles, such as Fig.12 (a) shows the polarization angle From 0° to 90°. Fig.12(a) It can be seen that the proposed frequency selective surface FSS design has good performance for different polarization directions. It shows the same performance and can effectively reflect electromagnetic waves in the ultra-wideband frequency band. In addition, for the incident angle θ, the transmission response of the frequency selective surface FSS design is below -10dB from 0° to 45°, which still meets the requirements for reflecting electromagnetic waves in the ultra-wideband frequency band, such as Fig.12 (b) as shown.

[0063] Example 5

[0064] Fig.14 The return loss curves of the ultra-wideband microstrip antenna before and after loading the frequency selective surface are shown. After loading the frequency selective surface, the performance of the antenna at low frequencies deteriorates, but the return loss in the entire ultra-wideband range (3.1GHz~10.6GHz) remains below -10dB, meeting the working requirements of the ultra-wideband antenna.

[0065] Fig.15 The radiation patterns of the E-plane, H-plane, and YZ-plane of the antenna with and without the metasurface are plotted at low, medium, and high frequencies, respectively. By designing the frequency selective surface, the radiated electromagnetic waves of the antenna are reshaped, and improved radiation is shown in the wide side direction, and back radiation is reduced. When the frequency selective surface is not loaded, the ultra-wideband microstrip antenna is an omnidirectional radiation surface. After the frequency selective surface is loaded, due to its position directly below the antenna's ground plane, it exhibits radiation patterns on the E-plane and YZ-plane, and back radiation is suppressed. In addition, in order to obtain a better radiation pattern, the frequency selective surface of the 3×3 array can be increased to 5×5 or higher.

[0066] Fig.16 The following is a comparison of the gain change curves of the antenna before and after loading the frequency selection surface. Before loading the frequency selection, the average gain of the antenna was 3.5dB and the maximum gain was 5.15dB. After loading the FSS surface, the average gain increased by about 4.5dB and the maximum gain reached 9.14dB. Compared with the low frequency, the gain amplitude of the antenna in the range of 7 to 9GHz is reduced. Overall, the gain level has increased from 2.3 to 5.1dB (without FSS) to 6.9 to 9.14dB (with FSS).

[0067] Fig.17 The three-dimensional directional comparison diagram of the radiation gain of the ultra-wideband antenna before and after the frequency selective surface is loaded is shown. Before loading, the ultra-wideband antenna exhibits an omnidirectional radiation pattern. After loading the frequency selective surface, the electromagnetic waves radiated from the back of the antenna are reflected and superimposed on the forward radiation of the antenna, the energy is more concentrated, and the gain is increased while forming a unidirectional radiation pattern.

[0068] The above shows and describes the main features and advantages of the utility model. For those skilled in the art, it is obvious that the utility model is not limited to the details of the above exemplary embodiments, and the utility model can be implemented in other specific forms without departing from the spirit or basic features of the utility model. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the utility model is limited by the attached claims rather than the above description, and it is intended to include all changes that fall within the meaning and scope of the equivalent elements of the claims in the utility model.

[0069] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A high-gain ultra-wideband antenna based on a metamaterial frequency selective surface, characterized in that: The high-gain ultra-wideband antenna is composed of an ultra-wideband microstrip antenna (1) and a frequency selective surface (2); and the ultra-wideband microstrip antenna (1) is arranged directly above the frequency selective surface (2); The ultra-wideband microstrip antenna (1) comprises a top layer, a middle layer and a bottom ground plane; the top layer is composed of a circular radiation patch (3) and a rectangular microstrip feed line (4); the middle layer is a first dielectric substrate (5); The bottom ground plate is a bottom patch (6) formed by cutting corners of a rectangular patch and opening rectangular grooves on the long sides after the corner cutting; The frequency selective surface (2) is composed of a plurality of surface unit structures arranged periodically; the surface unit structure is composed of a metal unit layer (7) and a second dielectric substrate (8), and the metal unit layer (7) is arranged on the second dielectric substrate (8); A circular groove (9) is provided at the center of the metal unit layer (7), four right-angle grooves (10) are evenly distributed around the circular groove (9), and the four right-angle grooves (10) are symmetrically distributed about the diagonal line of the metal unit layer (7); and four right-angle linear grooves (11) are correspondingly arranged outside the four right-angle grooves (10).

2. The high-gain ultra-wideband antenna based on a metamaterial frequency selective surface according to claim 1, characterized in that: The four right-angle grooves (10) are right-angled triangular grooves, whose hypotenuses are arc-shaped, the apex of the right angle is located on the diagonal of the metal unit layer (7), the right angle side is parallel to the right angle side of the metal unit layer (7), and the center of the arc hypotenuse coincides with the center of the circular groove (9).

3. The high-gain ultra-wideband antenna based on a metamaterial frequency selective surface according to claim 1, characterized in that: The four right-angle wire grooves (11) are chamfered wire grooves, the slope value of the chamfered angle is 45°, and the length of the chamfered right angle side is 0.5 mm; the single side length of the right-angle wire groove (11) is 3.65 mm.

4. The high-gain ultra-wideband antenna based on a metamaterial frequency selective surface according to claim 1, characterized in that: The radius of the circular radiation patch (3) is 5 mm; the length of the rectangular microstrip feed line (4) is 11 mm and the width is 2.6 mm.

5. The high-gain ultra-wideband antenna based on a metamaterial frequency selective surface according to claim 1, characterized in that: The two cut corners of the bottom patch (6) are 45 degrees and 4 mm long; a rectangular groove with a length of 3 mm and a width of 1.75 mm is dug in the middle of the long side of the cut corner of the bottom ground plate.

6. The high-gain ultra-wideband antenna based on a metamaterial frequency selective surface according to claim 1, characterized in that: The side length L1 of the metal unit layer (7) is 12 mm; the side length L2 of the second dielectric substrate (8) is 11.5 mm; and the radius R1 of the circular groove (9) is 3.5 mm.

7. The high-gain ultra-wideband antenna based on a metamaterial frequency selective surface according to claim 1, characterized in that: The metal unit layer (7) and the second dielectric substrate (8) are both rectangular.

8. The high-gain ultra-wideband antenna based on a metamaterial frequency selective surface according to claim 1, characterized in that: The thickness of the first dielectric substrate (5) and the second dielectric substrate (8) is 1.6 mm, and the distance between the ultra-wideband microstrip antenna (1) and the frequency selective surface (2) is half of the wavelength of the frequency value corresponding to the zero-point value of the reflection phase of the frequency reflection surface.

9. The high-gain ultra-wideband antenna based on a metamaterial frequency selective surface according to claim 1, characterized in that: The surface unit structure is composed of 3×3 or more periodic arrays according to the antenna size.

10. The high-gain ultra-wideband antenna based on a metamaterial frequency selective surface according to claim 1, characterized in that: The first dielectric substrate (5) and the second dielectric substrate (8) are both made of FR4, with a loss tangent angle of 0.025 and a relative dielectric constant of 4.4.

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