Antenna backward radiation suppression structure

Abstract

An antenna backward radiation suppression structure comprises a monopole antenna and a ground plane. The bottom end of the monopole antenna is fixed to the center of the ground plane. The structure is characterized by a circular plane at the center of the ground plane, with multiple identical radiation suppression structures extending uniformly outward from the periphery of the circular plane. The radiation suppression structures comprise a shank extending outward from the circular plane, with rectangular planes periodically arranged on the shank, all located on the same side of the shank. This structure effectively reduces surface waves on the ground plane and reduces backward radiation.

Description

Technical Field

[0001] The present invention relates to an antenna structure, in particular to an antenna backward radiation suppression structure. Background Art

[0002] Antennas are crucial components of wireless communication systems. They convert waveguide energy into radio wave energy and radiate it into space, or convert radio wave energy in space into waveguide energy. Furthermore, they distribute electromagnetic energy spatially, ensuring directional transmission and reception. When designing an antenna, many parameters must be considered, such as gain, 3dB bandwidth, sidelobe level, backscatter radiation level, and efficiency. These antenna specifications directly impact communication quality.

[0003] In some applications, it's desirable for an antenna to focus radiated energy within a narrow main beam while suppressing energy radiated in other directions, particularly backward radiation, which is directed in the opposite direction of the main beam. Excessive backward radiation can cause electromagnetic interference, impacting the operation of other components. In the antenna field, the "front-to-back ratio" is a common metric used to quantitatively describe the degree of backward radiation suppression. A high front-to-back ratio has always been a key performance characteristic for some antennas.

[0004] A subwavelength structure is a new type of electromagnetic structure whose periodic unit size is smaller than the wavelength, hence the name "subwavelength." This approach reduces the antenna's backward radiation by designing the cutoff frequency or adding loss to the subwavelength waveguide structure. Summary of the Invention

[0005] To solve the above problems, the present invention provides the following solutions:

[0006] An antenna backward radiation suppression structure includes a monopole antenna and a ground plane, wherein the bottom end of the monopole antenna is fixed to the center of the ground plane. The structure is characterized in that: the center of the ground plane is a circular plane, and multiple radiation suppression structures with the same structure extend evenly outward along the edge of the circular plane. The radiation suppression structure includes a tooth handle extending outward from the circular plane, and rectangular planes are periodically arranged on the tooth handle, and the rectangular planes are all located on the same side of the tooth handle.

[0007] Furthermore, the circular plane, the tooth handle and the rectangular plane are all made of metal.

[0008] Furthermore, the circular plane is made of metal, and the tooth handle and the rectangular plane are made of lossy film material.

[0009] At different frequencies, the serrated periodic structure exhibits different operating modes. At certain frequencies, the serrated periodic structure enters a cutoff mode, where surface waves decay exponentially, and the surface waves propagating to the edge of the ground plane are negligible. This cutoff mode can be used to conveniently suppress the propagation of surface waves, thereby reducing backward radiation. The backward radiation suppression effect described in this article is defined as the reduction in the maximum value within -180° ±15° on the radiation pattern. Given the antenna's operating frequency band, we can use 3D full-wave simulation to design the dimensions of the serrated periodic structure that exhibits the cutoff mode within that frequency band.

[0010] In addition to using the cutoff frequency of a metal toothed periodic structure to suppress surface wave propagation, the metal can be replaced with other thin film materials, introducing a certain amount of loss, causing the surface waves to be significantly attenuated as they propagate along the structure. This method can suppress surface wave propagation over a wide frequency band, thereby reducing backward radiation.

[0011] The beneficial effects of the present invention are:

[0012] 1. Reduce the antenna's backward radiation without affecting the antenna's return loss or increasing the additional ground plane area. This invention is simple to implement, low-cost, and has good practical value.

[0013] 2. Through appropriate size design, the metal toothed periodic structure can be used to achieve cutoff mode in certain frequency bands of interest, suppress surface waves, and reduce backward radiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a structural diagram of embodiment 1;

[0015] Figure 2 This is a structural diagram of embodiment 2;

[0016] Figure 3 This is a dispersion curve diagram of the radiation suppression structure of Example 1;

[0017] Figure 4 This is a comparison diagram of the return loss of Example 1 and a common monopole antenna;

[0018] Figure 5 This is a current amplitude distribution diagram on the radiation suppression structure of Example 1 at 14 GHz;

[0019] Figure 6 A comparison of the far-field gain of Example 1 and a conventional monopole antenna at 14GHz;

[0020] Figure 7 This is a comparison chart of the return loss of Example 2 and a common motor antenna;

[0021] Figure 8This is a current amplitude distribution diagram on the radiation suppression structure of Example 2 at 8.8 GHz;

[0022] Figure 9 This is a current distribution diagram on the radiation suppression structure of Example 2 at 14 GHz;

[0023] Figure 10 This is a comparison chart of the far-field gain of Example 2 and a common monopole antenna at 8.8 GHz;

[0024] Figure 11 This is a comparison chart of the far-field gain of Example 2 and a common monopole antenna at 14 GHz.

[0025] Figure: 1. Monopole antenna; 2. Radiation suppression structure; 3. Ground plane. DETAILED DESCRIPTION

[0026] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0027] Example 1: Figure 1 As shown,

[0028] An antenna rearward radiation suppression structure includes a monopole antenna 1 and a ground plane 3. The bottom end of the monopole antenna 1 is fixed to the center of the ground plane 3. The center of the ground plane 3 is a circular plane. Multiple radiation suppression structures 2 with identical structures extend uniformly outward from the edge of the circular plane. The radiation suppression structures 2 include a shank extending outward from the circular plane. Rectangular planes are periodically arranged on the shank, and all rectangular planes are located on the same side of the shank. The circular plane, shank, and rectangular planes are all made of metal. The rectangular planes in the radiation heterostructure have an arrangement period of 5 mm, a width of 3 mm, a spacing of 2 mm between the rectangular planes, and a shank width of 1 mm.

[0029] At different frequencies, the serrated periodic structure exhibits different operating modes. At certain frequencies, the structure enters a cutoff mode, where surface waves decay exponentially, and the surface waves propagating to the ground plane edge are negligible. This cutoff mode can be used to conveniently suppress the propagation of surface waves, thereby reducing backward radiation. Given a known antenna operating frequency band, 3D full-wave simulation can be used to design the dimensions of the serrated periodic structure that exhibits the cutoff mode within that frequency band.

[0030] According to the three-dimensional full-wave simulation, the dispersion curve can be calculated, such as Figure 3 As shown in Figure 3The dashed line is the dispersion curve of the free-space electromagnetic wave, and the solid line is the dispersion curve of the radiation suppression structure in this embodiment. It can be seen that when the frequency reaches around 12.5 GHz, the dispersion curve of the radiation suppression structure tends to be horizontal. When the frequency increases, the structure no longer supports any propagation mode. Therefore, when the frequency is greater than 12.5 GHz, the structure is in cutoff mode. At this time, the surface waves transmitted from the middle ground plane are largely reflected and do not propagate along the tooth-shaped structure. Figure 4 In , we found that the introduction of the radiation suppression structure has a very small impact on the return loss of the original monopole antenna. Figure 5 The surface current amplitude distribution on the radiation suppression structure in this embodiment is plotted at 14 GHz. The current amplitude decreases significantly along the radiation suppression structure. Figure 6 The far-field gain value at 14 GHz is plotted in the figure. The results show that the radiation suppression structure has a 5 dB suppression effect on the backward radiation of the original monopole antenna (maximum value within -180°±15°).

[0031] Example 2: Figure 2 As shown,

[0032] The structure of this embodiment is the same as that of the first embodiment, except that the tooth handle and rectangular plane in the radiation suppression structure 2 are replaced with an impedance surface material, and the sheet resistance is 50 ohms. Figure 7 The return loss of the monopole antenna is compared with the case of introducing an impedance surface material and a complete ground plane, and it is found that the influence of this structure is also very small. Figure 8 and Figure 9 The current amplitude distribution diagram of the lossy surface wave transmission structure at 8.8GHz and 14GHz was drawn in the figure, and it was found that at the two frequencies, the amplitude of the surface wave decreased rapidly after it was transmitted from the central ground plane to the lossy radiation suppression structure. Figure 10 and Figure 11 In the far-field gain diagram shown, we can also clearly see that after adding the lossy structure, the backward radiation is reduced by about 10dB at the two frequency points.

[0033] In summary, the two backward radiation suppression structures based on the toothed periodic structure proposed in the present invention have obvious effects, and the implementation process is simple, low cost, does not require additional ground plane space, and has little impact on the performance of the original antenna. The invention has a wide range of applications and can be extended to general antenna structures with a ground plane. Figure 6 、 Figure 10 and Figure 11 In the simulation, we obtained 5dB, 10dB, and 5dB of backward radiation suppression, respectively. In practical applications, the backward radiation suppression effect can be optimized based on the actual size through 3D full-wave simulation to achieve the indicators that meet product requirements.

[0034] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples and is subject to numerous variations. All variations that can be directly derived or conceived by a person of ordinary skill in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. An antenna backward radiation suppression structure, comprising a monopole antenna and a ground plane, wherein the bottom end of the monopole antenna is fixed to the center of the ground plane, characterized in that: The center of the ground plane is a circular plane, and multiple radiation suppression structures with the same structure extend evenly outward along the edge of the circular plane. The radiation suppression structure includes a tooth handle extending outward from the circular plane, and rectangular planes are periodically arranged on the tooth handle, and the rectangular planes are all located on the same side of the tooth handle; the arrangement period of the rectangular planes is 5mm, the width of the rectangular planes is 3mm, the spacing between the rectangular planes is 2mm, and the width of the tooth handle is 1mm.

2. The antenna backward radiation suppression structure according to claim 1, characterized in that: The circular plane, the tooth handle and the rectangular plane are all made of metal.

3. The antenna backward radiation suppression structure according to claim 1, characterized in that: The circular plane is made of metal, and the tooth handle and the rectangular plane are made of lossy film material.

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