A low-profile broadband circularly polarized filtering antenna based on metasurface

Abstract

The present invention relates to a low-profile broadband circularly polarized filtering antenna based on a metasurface, comprising a first dielectric substrate, a metasurface printed on the upper surface of the first dielectric substrate, a second dielectric substrate located below the first dielectric substrate with a metal floor sandwiched between the two, a microstrip feeder printed on the lower surface of the second dielectric substrate, and a metal through hole opened at the center of the second dielectric substrate. The present invention introduces a metasurface structure, so that the impedance bandwidth of the antenna is greatly improved, and has a higher gain; circular polarization does not require the introduction of an additional feeding structure, and is improved on the basis of the existing square patch corner cutting to achieve circular polarization, achieving a better axial ratio bandwidth; radiation zero points are introduced only by adding metal through holes and parasitic branches, and the radiation zero point frequency and out-of-band suppression can be adjusted by adjusting the relevant dimensions; the structure is simple, and while achieving a low profile, a wide bandwidth is achieved and has good filtering characteristics.

Description

Technical Field

[0001] The invention relates to the technical field of metasurface antennas and circularly polarized antennas, in particular to a low-profile broadband circularly polarized filtering antenna based on a metasurface. Background Art

[0002] With the development of wireless communications, antennas are moving towards miniaturization, broadband and multifunctionality. As an important component of the RF front end, its integration and miniaturization have received special attention. However, the traditional design method of cascading antennas and filters to achieve filtering characteristics has resulted in excessive size and has been unable to meet development requirements. Therefore, a method of integrating filter circuits with antennas has emerged. At present, fused filter antennas have become an important way to reduce system size, and as a result, fused filter antennas have received a lot of attention.

[0003] However, the bandwidth achieved by a large number of filtering antennas is relatively narrow, and researchers have used some design methods to broaden the bandwidth, such as adding stacked parasitic patches and introducing matching networks. Generally, adding stacked parasitic patches is the most commonly used method. To make the bandwidth wider, the antenna profile achieved by this method will be higher, and a profile that is too high will be limited in practical applications.

[0004] It can be seen that the current broadband circularly polarized filter antenna expands the bandwidth by stacking parasitic patches, so the high profile becomes an inevitable problem; the low-profile broadband circularly polarized filter antenna achieves the filtering effect by introducing a filtering circuit, which leads to insertion loss in the antenna; there are few studies on the low-profile broadband circularly polarized filter antenna designed with a fusion filter antenna, and most of the existing antenna structures of this type have complex structures. Therefore, it is of great research significance to design a low-profile, simple-structured filter antenna. Summary of the invention

[0005] In order to solve the problems of too narrow bandwidth of the filtering antenna and high cross-section of the broadband filtering antenna, the purpose of the present invention is to provide a low-profile broadband circularly polarized filtering antenna based on a metasurface which has a simple structure, a low cross-section, a wide bandwidth and good filtering characteristics.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a low-profile broadband circularly polarized filtering antenna based on a metasurface, comprising a first dielectric substrate, a metasurface is printed on the upper surface of the first dielectric substrate, a second dielectric substrate is located below the first dielectric substrate and a metal floor is sandwiched between the two, a microstrip feed line is printed on the lower surface of the second dielectric substrate, and a metal through hole is opened at the center position of the second dielectric substrate.

[0007] The metasurface includes a plurality of metasurface units, which are arranged in a 4×4 array. The metasurface units are rectangular, and the horizontal length of the rectangle is greater than the vertical length of the rectangle. The upper left corner and the lower right corner of the rectangle are cut, and the two right-angled sides of the cut triangle are unequal in length, and the length of the horizontal right-angled side is greater than the length of the vertical right-angled side; the gaps between the metasurface units are unequal, and the gaps between the horizontal metasurface units are greater than the gaps between the vertical metasurface units.

[0008] The microstrip feed line includes a cross-shaped metal patch arranged at a position deviating from the center of the second dielectric substrate, introducing a radiation zero point on the right side of the passband, and opening a circular groove connected to the metal through hole on the cross-shaped metal patch; two annular metal patches with openings are symmetrically arranged on both sides of the cross-shaped metal patch, and there is a gap between the two annular metal patches and the cross-shaped metal patch, and the openings of the annular metal patches face outward.

[0009] The first dielectric substrate and the second dielectric substrate are both Rogers dielectric plates with a dielectric constant of 3.38, and the metal floor, metasurface and microstrip feed line are all made of metal copper.

[0010] Separation step grooves are etched on the metal floor. The separation step grooves are two roughly T-shaped grooves. The two T-shaped grooves are arranged horizontally symmetrically, and there is a gap between the two T-shaped grooves. The gap is connected to the metal through hole. The length of the groove close to the gap is greater than the length of the groove far from the gap, and the width of the groove far from the gap is greater than the width of the groove close to the gap.

[0011] It can be seen from the above technical scheme that the beneficial effects of the present invention are: first, the present invention introduces a metasurface structure, so that the impedance bandwidth of the antenna is greatly improved, and it has a higher gain; second, the present invention realizes circular polarization without introducing an additional feeding structure, and improves on the existing square patch cutting to achieve circular polarization, thereby achieving a better axial ratio bandwidth; third, the present invention introduces radiation zero points only by adding metal through holes and parasitic branches without introducing additional filtering circuits, and the radiation zero point frequency and out-of-band suppression can be adjusted by adjusting relevant dimensions; fourth, the present invention has a simple structure, and while achieving a low profile, it achieves a wide bandwidth and has good filtering characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a front view of the present invention;

[0013] Figure 2 for Figure 1 A schematic diagram of the structure of the first dielectric substrate and the metasurface;

[0014] Figure 3 for Figure 1 Schematic diagram of the structure of the metal floor;

[0015] Figure 4 for Figure 1 A schematic diagram of the structure of the second dielectric substrate and the microstrip feed line;

[0016] Figure 5 is a return loss diagram of the present invention;

[0017] Figure 6 is an axial ratio parameter diagram of the present invention;

[0018] Figure 7 is the radiation gain diagram of the present invention;

[0019] Figure 8 The xoz surface radiation pattern of the present invention working at a frequency of 4.7 GHz;

[0020] Fig. 9 This is the yoz surface radiation pattern of the present invention working at a frequency of 4.7 GHz. DETAILED DESCRIPTION

[0021] like Figure 1 As shown, a low-profile broadband circularly polarized filtering antenna based on a metasurface comprises a first dielectric substrate 1, a metasurface 3 is printed on the upper surface of the first dielectric substrate 1, a second dielectric substrate 2 is located below the first dielectric substrate 1 and a metal floor 4 is sandwiched between the two, a microstrip feed line 6 is printed on the lower surface of the second dielectric substrate 2, and a metal through hole 5 is opened at the center of the second dielectric substrate 2.

[0022] like Figure 2 As shown, the metasurface 3 includes a plurality of metasurface units 9, and the plurality of metasurface units 9 are arranged in a 4×4 array. The metasurface units 9 are rectangular, and the horizontal length of the rectangle is greater than the vertical length of the rectangle. The upper left corner and the lower right corner of the rectangle are cut, and the two right-angled sides of the cut triangle are not equal in length, and the length of the horizontal right-angled side is greater than the length of the vertical right-angled side. On the basis of the existing square patch cutting to achieve circular polarization, it is improved to achieve a better axial ratio bandwidth; the gaps between the metasurface units 9 are unequal, and the gaps between the horizontal metasurface units 9 are greater than the gaps between the vertical metasurface units 9.

[0023] like Figure 4 As shown, the microstrip feed line 6 includes a cross-shaped metal patch 10 arranged at a position deviating from the center of the second dielectric substrate 2, introducing a radiation zero point on the right side of the passband, and a circular groove 8 connected to the metal through hole 5 is opened on the cross-shaped metal patch 10; two annular metal patches 11 with openings 12, i.e. parasitic branches, are symmetrically arranged on both sides of the cross-shaped metal patch 10, and there is a gap between the two annular metal patches 11 and the cross-shaped metal patch 10, and the opening 12 of the annular metal patch 11 faces outward, so that another radiation zero point is added to the right side of the passband, thereby improving the filtering characteristics of the upper stopband.

[0024] The first dielectric substrate 1 and the second dielectric substrate 2 are both Rogers dielectric plates with a dielectric constant of 3.38. The metal floor 4, the metasurface 3 and the microstrip feed line 6 are all made of metal copper.

[0025] like Figure 3 As shown, the metal floor 4 is etched with a separation step groove 13, which is two roughly T-shaped grooves, which are arranged horizontally symmetrically, and there is a gap 7 between the two T-shaped grooves, which is connected to the metal through hole 5, and the length of the groove close to the gap 7 is greater than the length of the groove far from the gap, and the width of the groove far from the gap 7 is greater than the width of the groove close to the gap. The metal through hole 5 connects the metal floor 4 and the microstrip feed line 6, so that a reverse current is formed near the metal through hole 5, and a radiation zero point is introduced on the left side of the passband.

[0026] like Figure 5 As shown, within the operating frequency band of 4.14 GHz to 5.40 GHz, the antenna’s S 11 That is, the reflection coefficient is below -10 dB, which means that the relative bandwidth of the antenna designed in the present invention can reach 26.34%, thus achieving broadband characteristics.

[0027] like Figure 6 As shown, in the working frequency band of 4.48 GHz to 5.37 GHz, the AR, i.e., the axial ratio, of the antenna is less than 3 dB, indicating that the axial ratio bandwidth of the antenna designed in the present invention can reach 18.2%, achieving better circular polarization characteristics.

[0028] like Figure 7 As shown, the average in-band gain is 8.27dBi, radiation zeros are introduced at 3.8GHz, 5.9GHz and 6.4GHz, and out-of-band suppression greater than 17dB is achieved in both the upper stopband and the lower stopband, indicating that the antenna designed in the present invention achieves good filtering characteristics.

[0029] like Figure 8 , 9 As shown, it can be seen from the figure that no matter it is the xoz plane or the yoz plane, the left-hand circular polarization (LHCP) gain of the antenna is greater than the right-hand circular polarization (RHCP) gain, indicating that the antenna designed by the present invention is a left-hand circular polarization (LHCP) antenna.

[0030] In order to solve the problem of high profile of filtering antenna, metasurface antenna has attracted attention as a low profile, high frequency band and high gain antenna. Applying metasurface structure to filtering antenna can achieve wide bandwidth and obtain a higher antenna gain by using this simple structure.

[0031] In addition, most of the metasurface-based filtering antennas currently studied mainly radiate linearly polarized waves, while circularly polarized antennas have unique advantages over linearly polarized antennas. They can not only receive linearly polarized waves in any direction, but also have anti-interference characteristics. Therefore, they are more popular in practical applications.

[0032] In summary, the present invention introduces a metasurface structure, so that the impedance bandwidth of the antenna is greatly improved and has a higher gain; the present invention realizes circular polarization without introducing an additional feeding structure, and improves on the existing square patch cutting to achieve circular polarization, thereby achieving a better axial ratio bandwidth; the present invention introduces a radiation zero point only by adding metal through holes and parasitic branches without introducing an additional filtering circuit, and the radiation zero point frequency and out-of-band suppression can be adjusted by adjusting relevant dimensions; the present invention has a simple structure, realizes a wide bandwidth while achieving a low profile and has good filtering characteristics.

Claims

1. A low-profile broadband circularly polarized filtering antenna based on a metasurface, characterized in that: It comprises a first dielectric substrate (1), a super surface (3) is printed on the upper surface of the first dielectric substrate (1), a second dielectric substrate (2) is located below the first dielectric substrate (1) and a metal floor (4) is sandwiched between the two, a microstrip feed line (6) is printed on the lower surface of the second dielectric substrate (2), and a metal through hole (5) is opened at the center of the second dielectric substrate (2); The microstrip feed line (6) comprises a cross-shaped metal patch (10) arranged at a position deviating from the center of the second dielectric substrate (2), introducing a radiation zero point on the right side of the passband, and a circular groove (8) connected to the metal through hole (5) is provided on the cross-shaped metal patch (10); two annular metal patches (11) with openings (12) are symmetrically arranged on both sides of the cross-shaped metal patch (10), a gap is provided between the two annular metal patches (11) and the cross-shaped metal patch (10), and the openings (12) of the annular metal patches (11) face outwards; The metal floor (4) is etched with a separation step groove (13), which is two roughly T-shaped grooves, the two T-shaped grooves are arranged horizontally symmetrically, and there is a gap (7) between the two T-shaped grooves, the gap (7) is connected to the metal through hole (5), the length of the groove close to the gap (7) is greater than the length of the groove away from the gap, and the width of the groove away from the gap (7) is greater than the width of the groove close to the gap.

2. The low-profile broadband circularly polarized filtering antenna based on a metasurface according to claim 1, characterized in that: The metasurface (3) comprises a plurality of metasurface units (9), the plurality of metasurface units (9) being arranged in a 4×4 array, the metasurface units (9) being rectangular, the horizontal length of the rectangle being greater than the vertical length of the rectangle, and the upper left corner and the lower right corner of the rectangle being cut, the two right-angled sides of the cut triangle are unequal in length, the length of the horizontal right-angled side being greater than the length of the vertical right-angled side; the gaps between the metasurface units (9) are unequal, the gaps between the metasurface units (9) being greater than the gaps between the vertical metasurface units (9).

3. The low-profile broadband circularly polarized filtering antenna based on a metasurface according to claim 1, characterized in that: The first dielectric substrate (1) and the second dielectric substrate (2) are both made of Rogers dielectric plates with a dielectric constant of 3.38, and the metal floor (4), the metasurface (3) and the microstrip feed line (6) are all made of metal copper.

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