Low-profile broadband circularly polarized antenna for ultra-wideband positioning system

Abstract

The invention discloses a low-profile broadband circularly polarized antenna for an ultra-wideband positioning system. The low-profile broadband circularly polarized antenna comprises a first dielectric substrate, a grounding plate and a second dielectric substrate, the first dielectric substrate, the grounding plate and the second dielectric substrate are sequentially attached from top to bottom; a plurality of circular metal patches are arranged on the upper surface of the first dielectric substrate to form a metasurface structure; a Z-shaped gap is etched in the grounding plate; the lower surface of the second dielectric substrate is provided with a microstrip feed structure, and the microstrip feed structure comprises a microstrip line, a feed branch with a gradual change structure, and an SMA connector. One end of the microstrip line is connected with the feed branch with the gradual change structure, and the other end is connected with the SMA connector. The circular metal patch is adopted to form the metasurface structure, the rectangular gaps of different sizes are etched in the center of the circular metal patch, the feed branch knot with the gradual change structure is coupled with the Z-shaped gap to excite the metasurface structure to generate circular polarization radiation, and large circular polarization bandwidth and impedance bandwidth are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave antennas, and in particular relates to a low-profile broadband circularly polarized antenna for an ultra-wideband positioning system. Background Art

[0002] Ultra-Wideband (UWB) technology, with its high-precision ranging and strong anti-interference capabilities, has shown great potential in indoor positioning, autonomous driving, the Industrial Internet of Things, and smart wearables. Antennas, as core components within UWB communication systems, have a direct impact on their performance.

[0003] Traditional linearly polarized antennas are susceptible to polarization mismatch due to changes in the terminal device's posture, leading to signal attenuation and even communication interruption. In contrast, circularly polarized antennas can effectively suppress multipath effects and reduce signal loss caused by polarization mismatch, thus offering significant advantages in UWB systems. Currently, mainstream UWB circularly polarized antennas include helical antennas and microstrip patch antennas. While helical antennas can achieve wide circular polarization bandwidth and directional radiation, they typically require a complex balun feed structure and metal back cavity, resulting in increased antenna height, bulk, and high manufacturing costs. Microstrip patch antennas are popular due to their lightweight and easy integration advantages, but their traditional design methods (such as corner cutting, slotting, or adding shorting pins) rely on metal reflectors with a quarter-wavelength (λ / 4) spacing to increase gain, resulting in a higher antenna profile and limiting their application in compact devices.

[0004] In recent years, metasurface technology, with its flexible control capabilities for electromagnetic waves, has provided new optimization directions for antenna design. However, existing circularly polarized antenna designs based on metasurfaces still face many challenges: metasurface units typically have narrowband characteristics, making it difficult to meet the broadband requirements of ultra-wideband systems; metasurface structures often require large physical dimensions to achieve effective electromagnetic control, resulting in an inefficiently compact antenna structure; and how to maintain high gain and stable circularly polarized radiation characteristics while reducing the antenna profile. Summary of the Invention

[0005] The main purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and provide a low-profile broadband circularly polarized antenna for an ultra-wideband positioning system.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A low-profile broadband circularly polarized antenna for an ultra-wideband positioning system, comprising a first dielectric substrate, a ground plate, and a second dielectric substrate;

[0008] The first dielectric substrate, the ground plate, and the second dielectric substrate are sequentially laminated from top to bottom;

[0009] A plurality of circular metal patches are provided on the upper surface of the first dielectric substrate to form a metasurface structure;

[0010] There are Z-shaped gaps etched into the ground plane;

[0011] A microstrip feeding structure is provided on the lower surface of the second dielectric substrate, including a microstrip line, a feeding branch with a gradient structure, and an SMA connector; one end of the microstrip line is connected to the feeding branch with the gradient structure, and the other end is connected to the SMA connector; the feeding branch with the gradient structure is coupled with the Z-shaped slot to excite the metasurface structure to generate circularly polarized radiation.

[0012] Furthermore, there are specifically 16 circular metal patches arranged in a 4×4 pattern on the upper surface of the first dielectric substrate;

[0013] There are four types of circular metal patches, namely three types of circular metal patches with rectangular gaps of different sizes etched in the center of the patch and a circular metal patch without etched gaps.

[0014] Furthermore, two metal rectangular pads are symmetrically provided on the lower surface of the second dielectric substrate for welding SMA connectors.

[0015] Furthermore, it also includes a metal via hole, which passes through the second dielectric substrate and connects the rectangular pad and the ground plate.

[0016] Furthermore, screws are included, and the screws penetrate the first dielectric substrate, the grounding plate and the second dielectric substrate. The first dielectric substrate, the grounding plate and the second dielectric substrate are tightly fitted and fixed by the screws.

[0017] Furthermore, the first dielectric substrate, the ground plate, and the second dielectric substrate have the same length and width dimensions, which are 40 mm×40 mm.

[0018] The first dielectric substrate and the second dielectric substrate are FR4 plates with a relative dielectric constant of 4.6 and a loss tangent of 0.017; the thickness of the first dielectric substrate is 2 mm, and the thickness of the second dielectric substrate is 1 mm;

[0019] The ground plate is specifically a metal ground plate.

[0020] Furthermore, the screws are specifically plastic screws, and there are four of them, symmetrically distributed at the four corners of the antenna.

[0021] Furthermore, the radius of the circular metal patches is 4.2 mm;

[0022] Three circular metal patches with rectangular gaps of different sizes etched in the center of the patch. The width of the etched rectangular gaps is 2mm, and the lengths are 5mm, 4mm, and 3mm respectively.

[0023] Furthermore, the upper and lower short gaps of the Z-shaped gap are both 6.55 mm long and 2.3 mm wide, and the middle long gap is 16.3 mm long and 2.3 mm wide.

[0024] Furthermore, the microstrip line has a specific width of 1.4 mm and a length of 17.65 mm;

[0025] The feed branch with a gradient structure has a narrowest bandwidth of 1.4mm, a maximum width of 9.85mm, and a total length of 9mm.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] 1. The present invention adopts circular metal patch units to form a metasurface structure, etches rectangular gaps of different sizes in the center of the circular metal patch, and adopts Z-shaped gap coupling to excite the metasurface structure to generate two mutually orthogonal electric fields with a phase difference of 90 degrees, which has a wider circular polarization bandwidth; and coupled feeding is performed through feeding branches with a gradient structure, which is conducive to impedance matching to obtain a larger impedance bandwidth.

[0028] 2. The present invention achieves a wider circular polarization bandwidth without increasing the size of the antenna by etching uneven rectangular slots on a circular metal patch and combining it with Z-shaped slot feeding. The antenna uses two closely adjacent dielectrics without introducing air dielectric, has a compact size, a simple structure, and a low processing cost.

[0029] 3. The circularly polarized antenna of the present invention has the advantages of low profile, wide bandwidth and high gain, and has great application potential in ultra-wideband systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0031] Figure 2 is a side view of the present invention;

[0032] Figure 3 is a schematic diagram of the upper surface of the first dielectric substrate in the present invention;

[0033] Figure 4 is a schematic diagram of the ground plate in the present invention;

[0034] Figure 5 is a schematic diagram of the lower surface of the second dielectric substrate in the present invention;

[0035] Figure 6 is a simulated reflection coefficient curve of the antenna of the embodiment;

[0036] Figure 7 is a simulated axial ratio curve of the antenna of the embodiment;

[0037] Figure 8 1 is a simulated gain and efficiency curve of the antenna of the embodiment;

[0038] Figure 9a is a simulated radiation pattern of the embodiment antenna in the XOZ plane at 6.0 GHz;

[0039] Figure 9b is a simulated radiation pattern of the antenna of the embodiment in the YOZ plane at 6.0 GHz;

[0040] Figure 10a is a simulated radiation pattern of the embodiment antenna in the XOZ plane at 6.5 GHz;

[0041] Figure 10b is a simulated radiation pattern of the antenna of the embodiment in the YOZ plane at 6.5 GHz;

[0042] Figure 11a is a simulated radiation pattern of the antenna of the embodiment at the XOZ plane at 7.0 GHz;

[0043] Figure 11b is a simulated radiation pattern of the antenna of the embodiment in the YOZ plane at 7.0 GHz;

[0044] Explanation of the accompanying figures: 1-first dielectric substrate; 2-second dielectric substrate; 3-ground plate; 4-circular metal patch without etched gaps; 5-circular metal patch with etched rectangular gaps of 5 mm long and 2 mm wide; 6-circular metal patch with etched rectangular gaps of 4 mm long and 2 mm wide; 7-circular metal patch with etched rectangular gaps of 3 mm long and 2 mm wide; 8-Z-shaped gap; 9-plastic screw; 10-metal via; 11-50 ohm microstrip line; 12-feed branch with gradient structure; 13-rectangular pad; 14-SMA connector. DETAILED DESCRIPTION

[0045] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0046] Example

[0047] like Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 as well as Figure 5 As shown, a low-profile broadband circularly polarized antenna for an ultra-wideband positioning system comprises:

[0048] A first dielectric substrate 1, a ground plate 3 and a second dielectric substrate 2;

[0049] The first dielectric substrate, the ground plate, and the second dielectric substrate are tightly fitted together from top to bottom;

[0050] A plurality of circular metal patches are provided on the upper surface of the first dielectric substrate to form a metasurface structure; the metasurface structure can be excited by slot coupling to generate circularly polarized radiation;

[0051] A Z-shaped slot 8 is etched on the ground plate; on the one hand, the ground plate serves as a metal radiation plate of the metasurface antenna, and on the other hand, couples and feeds the metasurface structure through the Z-shaped slot.

[0052] A microstrip feeding structure is provided on the lower surface of the second dielectric substrate, including a 50-ohm microstrip line 11, a feeding branch 12 with a gradient structure, and an SMA connector 14; one end of the microstrip line is connected to the feeding branch with the gradient structure, and the other end is connected to the SMA connector; the feeding branch with the gradient structure is coupled with the Z-shaped gap to stimulate the radiation of the metasurface structure.

[0053] like Figure 3 As shown, in this embodiment, there are 16 circular metal patches arranged in a 4×4 pattern on the top surface of the first dielectric substrate. There are four types of circular metal patches: three types with rectangular slits of varying sizes etched in the center of the patches, and four circular metal patches without etched slits. In this embodiment, the radius of each circular metal patch is 4.2 mm. For the three types of circular metal patches with rectangular slits of varying sizes etched in the center of the patches, the etched rectangular slits are all 2 mm wide and 5 mm, 4 mm, and 3 mm long, respectively.

[0054] like Figure 3 As shown, in this embodiment, the circular metal patches 4 without etched gaps are located at the four corners; the circular metal patch 5 with etched rectangular gaps of 5 mm long and 2 mm wide is located in the middle; the circular metal patches 6 with etched rectangular gaps of 4 mm long and 2 mm wide are located on the left and right sides; and the circular metal patches 7 with etched rectangular gaps of 3 mm long and 2 mm wide are located at the upper and lower positions.

[0055] like Figure 2 and Figure 5 As shown, in this embodiment, two metal rectangular pads 13 are symmetrically provided on the lower surface of the second dielectric substrate for soldering SMA connectors. This embodiment also includes a metal via 10 that passes through the second dielectric substrate and connects the rectangular pads and the ground plate.

[0056] like Figure 1 As shown, in this embodiment, plastic screws 9 are also included. The screws pass through the first dielectric substrate, the ground plate and the second dielectric substrate. The first dielectric substrate, the ground plate and the second dielectric substrate are tightly fixed by the screws; the number of plastic screws is 4, symmetrically distributed at the four corners of the antenna.

[0057] In this embodiment, the first dielectric substrate, ground plane, and second dielectric substrate have identical dimensions of 40 mm x 40 mm. The first and second dielectric substrates are made of FR4 with a relative dielectric constant of 4.6 and a loss tangent of 0.017. The thickness of the first dielectric substrate is 2 mm, and that of the second is 1 mm. The ground plane is a metal ground plane. The upper and lower short slots of the Z-shaped slot are both 6.55 mm long and 2.3 mm wide, while the middle long slot is 16.3 mm long and 2.3 mm wide. The microstrip line used for feeding is 1.4 mm wide and 17.65 mm long. The feed branch with a tapered structure has a minimum width of 1.4 mm and a maximum width of 9.85 mm, for a total length of 9 mm.

[0058] In the antenna of this embodiment, the signal is coupled from the feed branch on the lower surface of the second dielectric substrate to the Z-shaped slot, and then transmitted to the metasurface structure on the upper surface of the first dielectric substrate through the Z-shaped slot on the ground plane. Since the energy is coupled from the Z-shaped slot to the upper surface of the first dielectric substrate, it can simultaneously excite the metasurface to generate two mutually orthogonal electric fields with a certain phase difference between the two electric fields. The rectangular slot of the circular metal patch can be used to adjust the phase difference of the electric fields in the two directions, making the phase difference close to 90 degrees, thereby forming circularly polarized radiation.

[0059] In this embodiment, the energy radiated by the metasurface is obtained by coupling the microstrip feeding structure on the lower surface of the second dielectric substrate through the Z-shaped gap. Therefore, after determining the center frequency, the circular polarization bandwidth of the metasurface antenna can be improved by adjusting the size of the rectangular gap in the circular metal patch and the size of the Z-shaped gap, and the impedance matching bandwidth can be optimized by adjusting the length and width of the microstrip line and the feeding branch with a gradient structure.

[0060] like Figure 6 and Figure 7 As shown in the figure, the reflection coefficient curve and axial ratio curve obtained by simulating the antenna of this embodiment are shown respectively. As shown in the figure, the antenna has a wide impedance bandwidth and circular polarization bandwidth. The impedance bandwidth can reach 50.7% (5.637-7.928GHz), the 3dB axial ratio bandwidth is 27.5% (5.952-7.853GHz), and the overlapping bandwidth of impedance and axial ratio is 27.5% (5.952-7.853GHz). Figure 8 FIG. 4 shows the simulated gain and efficiency curves of the antenna of this embodiment. As can be seen from the figure, the gain and efficiency are relatively stable within the axial ratio bandwidth, with the highest gain reaching 6.7 dBic and the 3 dB gain bandwidth being 32%.

[0061] like Figure 9a and Figure 9b As shown in FIG, the simulated radiation pattern of the antenna of this embodiment at 6.0 GHz in the XOZ and YOZ planes; Figure 10a and Figure 10b As shown in FIG, the simulated radiation pattern of the antenna of this embodiment at 6.5 GHz in the XOZ and YOZ planes; Figure 11a and Figure 11b As shown in FIG. 1 , the simulated radiation patterns of the antenna of this embodiment in the XOZ and YOZ planes at 7.0 GHz are shown. As can be seen from the figure, the radiation pattern of the antenna of this embodiment is directional, radiating along the Z-axis direction, and the back lobe of the radiation pattern is relatively small, with a good front-to-back ratio.

[0062] In the present embodiment, a low-profile broadband circularly polarized antenna for an ultra-wideband positioning system is manufactured using a two-layer dielectric substrate. The metasurface structure consists of circular metal patches arranged in a 4×4 pattern. Rectangular slots are etched in the circular metal patches, and feeding branches with a gradient structure are coupled with the Z-shaped slots to excite the metasurface structure to generate circularly polarized radiation, thereby achieving a larger circularly polarized bandwidth. Feeding branches with a gradient structure are used for impedance matching to obtain a larger impedance bandwidth. In addition, the antenna of the present embodiment has the characteristics of small size, low profile, suitability for ultra-wideband positioning system applications, simple installation steps, and low cost.

[0063] It should also be noted that, in this specification, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or apparatus comprising the element.

[0064] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-profile broadband circularly polarized antenna for an ultra-wideband positioning system, characterized in that: It includes a first dielectric substrate, a ground plate and a second dielectric substrate; The first dielectric substrate, the ground plate, and the second dielectric substrate are sequentially laminated from top to bottom; A plurality of circular metal patches are provided on the upper surface of the first dielectric substrate to form a metasurface structure; There are Z-shaped gaps etched into the ground plane; A microstrip feeding structure is provided on the lower surface of the second dielectric substrate, including a microstrip line, a feeding branch with a gradient structure, and an SMA connector; One end of the microstrip line is connected to a feed branch with a gradient structure, and the other end is connected to an SMA connector; The feeding branches with gradient structure are coupled with Z-shaped slots to stimulate the metasurface structure to produce circularly polarized radiation.

2. The low-profile broadband circularly polarized antenna for an ultra-wideband positioning system according to claim 1, characterized in that: There are specifically 16 circular metal patches arranged in a 4×4 pattern on the upper surface of the first dielectric substrate; There are four types of circular metal patches, namely three types of circular metal patches with rectangular gaps of different sizes etched in the center of the patch and a circular metal patch without etched gaps.

3. The low-profile broadband circularly polarized antenna for an ultra-wideband positioning system according to claim 1, wherein: Two metal rectangular pads are symmetrically provided on the lower surface of the second dielectric substrate for welding SMA connectors.

4. The low-profile broadband circularly polarized antenna for an ultra-wideband positioning system according to claim 3, wherein: It also includes a metal via hole, which passes through the second dielectric substrate and connects the rectangular pad and the ground plate.

5. The low-profile broadband circularly polarized antenna for an ultra-wideband positioning system according to claim 1, wherein: The device further comprises screws, which penetrate the first dielectric substrate, the grounding plate and the second dielectric substrate. The first dielectric substrate, the grounding plate and the second dielectric substrate are tightly fitted and fixed by the screws.

6. The low-profile broadband circularly polarized antenna for an ultra-wideband positioning system according to claim 5, characterized in that: The first dielectric substrate, the ground plate, and the second dielectric substrate have the same length and width dimensions of 40 mm × 40 mm; The first dielectric substrate and the second dielectric substrate are FR4 plates with a relative dielectric constant of 4.6 and a loss tangent of 0.017; the thickness of the first dielectric substrate is 2 mm, and the thickness of the second dielectric substrate is 1 mm; The ground plate is specifically a metal ground plate.

7. The low-profile broadband circularly polarized antenna for an ultra-wideband positioning system according to claim 6, characterized in that: The screws are plastic screws, and there are four of them, symmetrically distributed at the four corners of the antenna.

8. The low-profile broadband circularly polarized antenna for an ultra-wideband positioning system according to claim 2, wherein: The radius of the circular metal patches is 4.2 mm; Three circular metal patches with rectangular gaps of different sizes etched in the center of the patch. The width of the etched rectangular gaps is 2mm, and the lengths are 5mm, 4mm, and 3mm respectively.

9. The low-profile broadband circularly polarized antenna for an ultra-wideband positioning system according to claim 1, wherein: The upper and lower short gaps of the Z-shaped gap are both 6.55 mm long and 2.3 mm wide, and the long gap in the middle is 16.3 mm long and 2.3 mm wide.

10. The low-profile broadband circularly polarized antenna for an ultra-wideband positioning system according to claim 1, wherein: The specific width of the microstrip line is 1.4mm and the length is 17.65mm; The feed branch with a gradient structure has a narrowest bandwidth of 1.4mm, a maximum width of 9.85mm, and a total length of 9mm.

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