Low-profile broadband polarization reconfigurable antenna

Abstract

The invention discloses a low-profile broadband polarization reconfigurable antenna, which belongs to the field of antennae, and comprises a first dielectric substrate and a second dielectric substrate which are arranged in a laminated manner, and a planar four-arm Archimedes helical antenna is arranged on the surface, far away from the second dielectric substrate, of the first dielectric substrate. A high-resistance surface metal patch is arranged between the first dielectric substrate and the second dielectric substrate; the planar four-arm Archimedes spiral antenna comprises four spiral arms extending along an Archimedes spiral line, the four spiral arms are of a central symmetry structure, a gap exists between every two adjacent spiral arms, and the high-resistance surface metal patch comprises a plurality of metal patches sequentially distributed in the circumferential direction of the second dielectric substrate. Therefore, the bandwidth of the reconstructed antenna can be widened, and the communication performance of the antenna is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of antennas, and particularly relates to a low-profile broadband polarization reconfigurable antenna. Background Art

[0002] With the rapid development of wireless communication technologies, users have an increasing demand for communication services. An antenna is a common communication structure in a radio system. A reconfigurable antenna is an antenna that can dynamically adjust its frequency, radiation pattern, polarization, or other performance parameters. Due to the advantages of reconfigurable antennas in avoiding noise interference, increasing channel capacity, and overcoming multipath attenuation, they are widely used in fields such as wireless communication, radar, and satellite communication.

[0003] Currently, common reconfigurable antennas include a microstrip line feeding structure, a first dielectric plate, a slot plate, a second dielectric plate, and a dipole structure arranged in sequence from bottom to top. There are cross slots on the slot plate. The microstrip line feeding structure couples energy to the dipole structure through the cross slots. A PIN diode is placed in each of the four arms of the cross slots. By controlling the on / off states of the four PIN diodes, the antenna can be switched between multiple polarization states. However, the bandwidth of this type of reconfigurable antenna is relatively narrow, which limits the communication performance of the antenna. Summary of the Invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a low-profile broadband polarization reconfigurable antenna. The technical problems to be solved by the present invention are realized through the following technical solutions:

[0005] In a first aspect, the present invention provides a low-profile broadband polarization reconfigurable antenna, including a first dielectric substrate and a second dielectric substrate stacked. A planar four-arm Archimedean spiral antenna is provided on the surface of the first dielectric substrate away from the second dielectric substrate, and a high-impedance surface metal patch is provided between the first dielectric substrate and the second dielectric substrate.

[0006] The planar four-arm Archimedean spiral antenna includes four spiral arms extending along the Archimedean spiral. The four spiral arms are centrosymmetric and there is a gap between adjacent spiral arms. The high-impedance surface metal patch includes a plurality of metal patches sequentially distributed along the circumference of the second dielectric substrate.

[0007] In an embodiment of the present invention, it further includes a coaxial feeding wire and a coaxial feeding probe. A first feeding hole is provided on the first dielectric substrate, and a second feeding hole is provided on the second dielectric substrate. The coaxial feeding probe sequentially passes through the second feeding hole and the first feeding hole to feed the planar four-arm Archimedean spiral antenna. One end of the coaxial feeding wire is connected to the coaxial feeding probe, and the other end is used to be connected to a digital amplitude-phase control circuit.

[0008] In one embodiment of the present invention, four first feeding holes are provided and distributed on the central side of the first dielectric substrate, and four second feeding holes are provided and distributed on the central side of the second dielectric substrate. The four first feeding holes and the four second feeding holes correspond to each other one by one;

[0009] Four coaxial feeding wires and four coaxial feeding probes are provided. The four coaxial feeding probes are respectively inserted into the four first feeding holes, and the four coaxial feeding wires are respectively connected to the four coaxial feeding probes.

[0010] In one embodiment of the present invention, four tapered impedance transformation lines are further provided on the surface of the first dielectric substrate far from the second dielectric substrate. The first ends of the four tapered impedance transformation lines are respectively connected to the four coaxial feeding probes, and the second ends of the four tapered impedance transformation lines are respectively connected to the four spiral arms;

[0011] The cross-sectional area of the first end of the tapered impedance transformation line is larger than the cross-sectional area of the second end of the tapered impedance transformation line, and from the first end to the second end of the tapered impedance transformation line, the cross-sectional area of the tapered impedance transformation line gradually decreases.

[0012] In one embodiment of the present invention, the tapered impedance transformation lines are all spiral structures extending along the Archimedean spiral, and the four tapered impedance transformation lines are in a centrosymmetric structure.

[0013] In one embodiment of the present invention, the inner diameter of the tapered impedance transformation line is 5.1 mm - 5.2 mm, the width of the first end of the tapered impedance transformation line is 1.5 mm - 1.9 mm, and the width of the second end of the tapered impedance transformation line is 0.4 mm - 0.5 mm;

[0014] The width of the end of the spiral arm connected to the tapered impedance transformation line is equal to the width of the second end of the tapered impedance transformation line, and the inner diameter of the spiral arm is 13.75 mm - 13.8 mm.

[0015] In one embodiment of the present invention, both the first dielectric substrate and the second dielectric substrate are circular plates, and the high-impedance surface metal patch includes a plurality of first metal patches, a plurality of second metal patches, and a plurality of third metal patches;

[0016] The plurality of first metal patches are sequentially arranged along the circumference of the second dielectric substrate and enclose a first annular structure, the plurality of second metal patches are sequentially arranged along the circumference of the second dielectric substrate and enclose a second annular structure, and the plurality of third metal patches are sequentially arranged along the circumference of the second dielectric substrate and enclose a third annular structure;

[0017] The first annular structure, the second annular structure, and the third annular structure are nested in sequence. The area of the first metal patch is smaller than the area of the second metal patch, and the area of the second metal patch is smaller than the area of the third metal patch.

[0018] In an embodiment of the present invention, the radius of the first dielectric substrate is 60 mm - 70 mm, and the thickness is 0.7 mm - 0.8 mm;

[0019] The radius of the second dielectric substrate is 100 mm - 105 mm, and the thickness is 1 mm - 1.5 mm.

[0020] In an embodiment of the present invention, a metal ground plane is provided on the surface of the second dielectric substrate away from the first dielectric substrate.

[0021] In an embodiment of the present invention, the materials of the spiral arms, the tapered impedance transformation lines, the metal patches, and the metal ground plane are all copper.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] In the above solution of the present application, the reconfigurable antenna includes a first dielectric substrate and a second dielectric substrate stacked on top of each other. A planar four-arm Archimedean spiral antenna is provided on the surface of the first dielectric substrate away from the second dielectric substrate, and a high-impedance surface metal patch is provided between the first dielectric substrate and the second dielectric substrate; the planar four-arm Archimedean spiral antenna includes four spiral arms extending along the Archimedean spiral. The four spiral arms are centrosymmetric and there is a gap between adjacent spiral arms. The high-impedance surface metal patch includes a plurality of metal patches distributed sequentially along the circumference of the second dielectric substrate. With this structure, first, when a planar four-arm Archimedean spiral antenna is provided on the first dielectric substrate, since the planar four-arm Archimedean spiral antenna has the advantages of circular polarization, wide bandwidth, and low profile, the bandwidth of the antenna can be broadened and the communication performance of the antenna can be improved. Second, when a high-impedance surface metal patch is provided between the first dielectric substrate and the second dielectric substrate, the high-impedance surface metal patch can produce frequency-selective reflection, absorption, or diffraction of electromagnetic waves. Since the maximum radiation direction of the planar four-arm Archimedean spiral antenna is in the normal direction on both sides of the plane, when the high-impedance surface metal patch is provided, the reflection characteristics of the high-impedance surface metal patch can be utilized to achieve the unidirectional radiation of the planar four-arm Archimedean spiral antenna, thereby improving the radiation performance of the antenna and increasing the gain of the antenna.

[0024] The following will further describe the present invention in detail with reference to the drawings and embodiments. Description of the Drawings

[0025] Figure 1 is an exploded view of the reconfigurable antenna provided by the embodiment of the present invention;

[0026] Figure 2 is the front view of the reconfigurable antenna provided by the embodiment of the present invention;

[0027] Figure 3It is the top view of the reconfigurable antenna provided by the embodiment of the present invention;

[0028] Figure 4 It is the schematic diagram of the conical impedance transformation line in the embodiment of the present invention;

[0029] Figure 5 It is the schematic diagram of the planar four-arm Archimedean spiral antenna in the embodiment of the present invention;

[0030] Figure 6 It is the schematic diagram of the second dielectric substrate and the high-impedance surface metal patch in the embodiment of the present invention;

[0031] Figure 7 It is the equivalent circuit diagram of the high-impedance surface metal patch in the embodiment of the present invention;

[0032] Figure 8 It is the gain pattern of the reconfigurable antenna when exciting the right-hand circularly polarized wave in the embodiment of the present invention;

[0033] Figure 9 It is the gain pattern of the reconfigurable antenna when exciting the left-hand circularly polarized wave in the embodiment of the present invention;

[0034] Figure 10 It is the right-hand circular polarization axial ratio schematic diagram of the reconfigurable antenna in the embodiment of the present invention;

[0035] Figure 11 It is the left-hand circular polarization axial ratio schematic diagram of the reconfigurable antenna in the embodiment of the present invention.

[0036] Reference numerals: 1 - the first dielectric substrate, 2 - the second dielectric substrate, 3 - the planar four-arm Archimedean spiral antenna, 4 - the high-impedance surface metal patch, 5 - the metal ground plane, 6 - the conical impedance transformation line. Detailed implementation manners

[0037] The following further describes the present invention in detail with specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0038] The concept of reconfigurable antennas was first proposed by scholars such as D. Schaubert in 1983. Its core idea is to achieve multiple functions through a single antenna to meet different application requirements. Such antennas can change their working states through mechanical control, electrical control and other means on the premise of keeping the basic physical structure unchanged, so as to realize flexible switching of functions.

[0039] Polarization reconfigurable antennas have broad application prospects in the fields of wireless communication and sensors. By dynamically adjusting the polarization state, such antennas can significantly improve signal reliability, anti-interference ability, and the flexibility of communication systems. Specifically, polarization reconfigurable antennas can switch polarization modes according to the requirements of the communication link, thereby optimizing signal transmission quality, reducing the impact of polarization mismatch, and enhancing the stability of communication systems. In 5G and future 6G networks, polarization reconfigurable antennas can be used to enhance beamforming and interference management capabilities. By adjusting the polarization state in real time to adapt to environmental changes, such antennas can effectively improve signal coverage and anti-interference performance.

[0040] High impedance surface is an electromagnetic material with a periodic structure, characterized by its ability to produce frequency-selective reflection, absorption, or diffraction of electromagnetic waves. By adjusting the geometric shape, size, and arrangement of its elements, precise control over the propagation characteristics of electromagnetic waves can be achieved. This structure can achieve high reflectivity or high transmittance within a specific frequency range and can even shield electromagnetic waves of specific frequencies.

[0041] High impedance surfaces have been widely used in the fields of antenna design, electromagnetic wave shielding, radiation control, and array antennas in wireless communication systems. In antenna design, high impedance surfaces can be used as ground planes or reflectors, significantly improving the performance and radiation characteristics of antennas. In addition, high impedance surfaces can also be used to develop various electromagnetic shielding devices, effectively reducing electromagnetic interference to circuits or devices. As a new type of electromagnetic material structure, high impedance surfaces exhibit many advantages in antenna design, such as reducing back radiation of antennas, shrinking antenna size, increasing antenna efficiency, suppressing vertical radiation, and reducing side lobes. With further research and optimized design, high impedance surfaces are expected to play a more important role in the fields of wireless communication, radar systems, medical devices, and electronic devices, providing effective solutions for the growing demand for electromagnetic wave management.

[0042] Helical antennas have long been widely used in the fields of military surveillance, broadband communication systems, and global navigation satellite systems due to their ability to generate extremely broadband circular polarization radiation. Among them, planar spiral antennas, as a typical circularly polarized ultra-wideband antenna, stand out for their excellent performance such as simple structure, small size, wide frequency band, circular polarization, and low profile. Archimedean spiral antennas are based on the principle of self-similarity and have non-frequency-varying characteristics. Their electrical performance remains stable when the operating frequency changes, making them suitable for wideband applications. Among them, compared with two-arm spiral antennas, four-arm spiral antennas have more advantages in some special application scenarios. First, four-arm spiral antennas have the ability to excite multiple modes, making them widely used in monopulse direction finding systems; second, their highly symmetric structure results in a more perfect radiation pattern and more excellent phase stability, which is particularly important for high-precision global navigation satellite systems.

[0043] The maximum radiation direction of a planar spiral antenna is usually located in the normal direction on both sides of the plane. To achieve unidirectional radiation, the traditional method is to install a reflection cavity structure on the back of the antenna. However, the depth of the reflection cavity needs to meet the requirement of a quarter wavelength, which will increase the antenna profile and limit its flexibility in practical applications.

[0044] Please refer to Figure 1 、 Figure 2 and Figure 3 , Embodiments of the present invention provide a low-profile broadband polarization reconfigurable antenna, including a first dielectric substrate 1 and a second dielectric substrate 2 arranged in a stacked manner. On the surface of the first dielectric substrate 1 far from the second dielectric substrate 2, a planar four-arm Archimedean spiral antenna 3 is provided. A high-impedance surface metal patch 4 is provided between the first dielectric substrate 1 and the second dielectric substrate 2; the planar four-arm Archimedean spiral antenna 3 includes four spiral arms extending along the Archimedean spiral. The four spiral arms are in a centrosymmetric structure and there is a gap between adjacent two spiral arms. The high-impedance surface metal patch 4 includes a plurality of metal patches distributed in sequence along the circumference of the second dielectric substrate 2.

[0045] In some embodiments of the present application, the materials of the first dielectric substrate 1 and the second dielectric substrate 2 are both Rogers RO4350B, and the relative dielectric constants are both 3.66.

[0046] In some embodiments of the present application, the four spiral arms in the planar four-arm Archimedean spiral antenna 3 are staggered. The starting ends of the four spiral arms are all located on the central side of the first dielectric substrate 1, and the starting ends of the four spiral arms differ by 90°.

[0047] In some embodiments of the present application, the above reconfigurable antenna can achieve polarization conversion between left-handed circular polarization and right-handed circular polarization in the frequency band of 1.88 - 3.67 GHz. Among them, the axial ratio bandwidth in the right-handed circular polarization state is 1.61 - 4.24 GHz, the gain is 10.1 dBi, the axial ratio bandwidth in the left-handed circular polarization state is 1.88 - 3.67 GHz, the gain is 8.21 dBi, and the profile size of the antenna is 2.06 mm.

[0048] In some embodiments of the present application, the reconfigurable antenna can achieve polarization mode switching by changing the phase relationship of the feeding points of the four spiral arms. By providing equal-amplitude feeding with a phase difference of 90° clockwise or counterclockwise for the ports of the four spiral arms, left-handed circularly polarized waves or right-handed circularly polarized waves can be excited, thereby achieving polarization reconfiguration.

[0049] In the above solution of the present application, the reconfigurable antenna includes a first dielectric substrate 1 and a second dielectric substrate 2 which are stacked. A planar four-arm Archimedean spiral antenna 3 is provided on the surface of the first dielectric substrate 1 away from the second dielectric substrate 2, and a high-impedance surface metal patch 4 is provided between the first dielectric substrate 1 and the second dielectric substrate 2. The planar four-arm Archimedean spiral antenna 3 includes four spiral arms extending along the Archimedean spiral. The four spiral arms are centrosymmetric and there is a gap between adjacent spiral arms. The high-impedance surface metal patch 4 includes a plurality of metal patches sequentially distributed along the circumference of the second dielectric substrate 2. With this structure, first, when the planar four-arm Archimedean spiral antenna 3 is provided on the first dielectric substrate 1, since the planar four-arm Archimedean spiral antenna 3 has the advantages of circular polarization, wide bandwidth, and low profile, the bandwidth of the antenna can be broadened and the communication performance of the antenna can be improved. Second, when the high-impedance surface metal patch 4 is provided between the first dielectric substrate 1 and the second dielectric substrate 2, the high-impedance surface metal patch 4 can produce frequency-selective reflection, absorption, or diffraction of electromagnetic waves. Since the maximum radiation direction of the planar four-arm Archimedean spiral antenna 3 is in the normal direction on both sides of the plane, when the high-impedance surface metal patch 4 is provided, the reflection characteristics of the high-impedance surface metal patch 4 can be utilized to achieve the unidirectional radiation of the planar four-arm Archimedean spiral antenna 3, thereby improving the radiation performance of the antenna and increasing the gain of the antenna. In addition, the present application can reduce the processing difficulty of the antenna, making the processing and production easier.

[0050] It can be understood that since the maximum radiation direction of the planar spiral antenna is in the normal direction on both sides of the plane, in order to obtain unidirectional radiation, the traditional method is to add a reflection cavity structure on its back, but the depth of the reflection cavity needs to meet the requirement of a quarter-wavelength distance, resulting in an increase in the profile of the antenna. When the high-impedance surface metal patch 4 is used in the present application, by utilizing the characteristic of the high-impedance surface with opposite-phase reflection, the requirement for the reflection surface to be a quarter-wavelength distance away from the antenna no longer needs to be met, thereby reducing the antenna profile. At the same time, due to the very high surface impedance of the high-impedance surface, it has the characteristic of suppressing surface current, and can also increase the antenna gain and improve the radiation performance.

[0051] In some embodiments of the present application, it further includes a coaxial feeding wire and a coaxial feeding probe. A first feeding hole is provided on the first dielectric substrate 1, and a second feeding hole is provided on the second dielectric substrate 2. The coaxial feeding probe sequentially passes through the second feeding hole and the first feeding hole to feed the planar four-arm Archimedean spiral antenna 3. One end of the coaxial feeding wire is connected to the coaxial feeding probe, and the other end is used to be connected to a digital amplitude-phase control circuit. With this structure, coaxial feeding can be achieved through the coaxial feeding wire, the coaxial feeding probe, the first feeding hole, and the second feeding hole. When feeding the four spiral arms through the digital amplitude-phase control circuit, the polarization mode can be switched by changing the phase relationship of the feeding points of the four spiral arms. By providing equal-amplitude feeding with a phase difference of 90° clockwise or counterclockwise at the ports of the four spiral arms, a left-handed circularly polarized wave or a right-handed circularly polarized wave can be excited.

[0052] In some embodiments of the present application, the feeding network of the present application adopts a four-port digital amplitude-phase control circuit. The four ports can provide equal-amplitude feeding with a phase difference of 90° in sequence, and the phase of the four ports can be switched through a key, so as to achieve polarization reconfigurability.

[0053] In some embodiments of the present application, there are four first feeding holes which are distributed on the central side of the first dielectric substrate 1, and there are four second feeding holes which are distributed on the central side of the second dielectric substrate 2. The four first feeding holes and the four second feeding holes correspond one by one; there are four coaxial feeding wires and four coaxial feeding probes. The four coaxial feeding probes are respectively inserted into the four first feeding holes, and the four coaxial feeding wires are respectively connected to the four coaxial feeding probes. With this structure, by respectively providing equal-amplitude feeding with a phase difference of 90° clockwise or counterclockwise for the four spiral arms through the four coaxial feeding wires and the coaxial feeding probes, the phase relationship of the feeding points of the four spiral arms can be changed, and further the switching of the polarization mode of the reconfigurable antenna can be achieved.

[0054] It should be noted that for the planar four-arm Archimedean spiral antenna 3 with central feeding, it is usually necessary to expand the inner radius to leave enough space for the feeding area. The increase in the inner radius means a lower high-frequency operating point because the spiral antenna radiates from a region where one spiral circumference is equal to one wavelength. In the present application, the inner radius of the planar four-arm Archimedean spiral antenna 3 is several times the width of the antenna, providing enough length for impedance transformation.

[0055] In some embodiments of the present application, such as Figure 3 and Figure 4As shown, four tapered impedance transformation lines 6 are further provided on the surface of the first dielectric substrate 1 away from the second dielectric substrate 2. The first ends of the four tapered impedance transformation lines 6 are respectively connected to four coaxial feeding probes, and the second ends of the four tapered impedance transformation lines 6 are respectively connected to four spiral arms; the cross-sectional area of the first end of the tapered impedance transformation line 6 is larger than the cross-sectional area of the second end of the tapered impedance transformation line 6, and from the first end to the second end of the tapered impedance transformation line 6, the cross-sectional area of the tapered impedance transformation line 6 gradually decreases. With this structure, the tapered impedance transformation line 6 realizes the matching between different impedance transmission lines through a smooth impedance transition, reduces signal reflection and loss, improves signal integrity, and realizes impedance matching and feeding.

[0056] In some embodiments of the present application, the tapered impedance transformation lines 6 are all spiral structures extending along an Archimedean spiral, and the four tapered impedance transformation lines 6 are in a centrosymmetric structure. With this structure, the length of the tapered impedance transformation line 6 can be increased, and the impedance matching and feeding of the tapered impedance transformation line 6 can be further optimized.

[0057] In some embodiments of the present application, as Figure 4 and Figure 5 shown, the inner diameter r t of the tapered impedance transformation line 6 is 5.1 mm - 5.2 mm, preferably 5.15 mm, the width w0 of the first end of the tapered impedance transformation line 6 is 1.5 mm - 1.9 mm, preferably 1.7 mm, the width w1 of the second end of the tapered impedance transformation line 6 is 0.4 mm - 0.5 mm, preferably 0.45 mm; the width w of the end of the spiral arm connected to the tapered impedance transformation line 6 is equal to the width w1 of the second end of the tapered impedance transformation line 6, and the inner diameter r d of the spiral arm is 13.75 mm - 13.8 mm, preferably 13.775 mm.

[0058] In some embodiments of the present application, the equation of the planar Archimedean spiral is:

[0059]

[0060] where r is the distance from any point on the curve to the origin of the polar coordinate, is the azimuth angle, is the starting angle, r0 is the distance from the starting point of the spiral to the origin, and a is the spiral growth rate. Let respectively, and four symmetric planar Archimedean spirals can be obtained, and the spiral width of each spiral arm is equal to the distance between the two spiral arms. In this way, a self-complementary structure can be formed, which is beneficial to realizing broadband impedance matching. For an Archimedean spiral antenna, the annular band with a circumference of about one wavelength forms an effective radiation area. The outer diameter D of the spiral depends on the wavelength λ corresponding to the lower limit frequencymax , generally, its perimeter C = πD ≥ 1.25λ max . The inner diameter of the spiral has a great influence on the impedance matching and upper working frequency of the antenna. Generally, 2r0 < λ min / 4, where λ min is the wavelength corresponding to the upper working frequency.

[0061] Based on Duchamp's theory, the impedance of an N-arm self-complementary spiral antenna operating in mode m satisfies the formula:

[0062]

[0063] It can be obtained therefrom that, in mode 1, the planar four-arm Archimedean spiral antenna 3 has an impedance of 133.3 Ω in free space. In practice, the actual impedance of the planar four-arm Archimedean spiral antenna 3 printed on the first dielectric substrate is less than the theoretical value, and this half-space impedance can be approximated as where ε eff is the effective dielectric constant of the dielectric substrate, and its usual value is (ε r +1) / 2. In this application, the antenna is constructed on a dielectric substrate with ε r = 3.66, and the impedance of the antenna is about 87 Ω.

[0064] Traditional spiral antennas mostly adopt a balun structure to ensure balanced feeding, but the structure of the balun is too large and not conducive to the design of low-profile antennas. Based on the theory of tapered transmission lines, this application designs four-segment tapered impedance transformation lines 6 connected to the four spiral arms of the planar four-arm Archimedean spiral antenna 3, uses a coaxial probe to feed at the top of the tapered transmission line, and connects the other end of the coaxial to a digital amplitude-phase control circuit to achieve impedance matching and feeding.

[0065] The maximum reflection coefficient of the tapered impedance transformation line 6 with a length of L is determined by the following formula:

[0066]

[0067] where Z L is the load impedance, Z0 is usually 50 Ω, and λ g is the waveguide wavelength at the cut-off frequency in the medium. Thus, for an acceptable reflection coefficient ρ m , the minimum length of the tapered impedance transformation line 6 is:

[0068]

[0069] Based on the above formula, the physical length of the tapered impedance transformation line 6 in this application is about 0.24λ g = 14.4 mm, and it is placed at the center of the antenna.

[0070] The high-resistance surface adopted in this application can achieve the same phase of the reflected wave and the incident wave within its resonant frequency band, which can be equivalent to an ideal magnetic conductor and has an inhibitory effect on surface waves. When electromagnetic waves are projected onto the high-resistance surface, current will be generated in the metal patch units on the upper surface of the medium. The current flows along the upper surface metal patch, through the metal vias and the ground plane to form inductance, and charges will accumulate between two adjacent metal patches on the upper surface, thus generating capacitance between the two metal patches. Therefore, the high-impedance surface structure can be equivalent to a parallel LC resonant circuit, that is, the equivalent circuit diagram of the high-resistance surface metal patch 4 as shown in Figure 7 is shown.

[0071] Please refer to Figure 6 and Figure 7 . The equivalent capacitance and inductance of the high-resistance surface can be approximately calculated by the following formulas:

[0072]

[0073] L = μ0h

[0074] where W is the side length of the metal patch on the high-resistance surface unit, ε0 and ε1 are the permittivities of free space and the dielectric substrate respectively, 2g is the gap width between two metal patch units, p = W + 2g is the unit period size, μ0 is the magnetic permeability of free space, and h is the thickness of the dielectric substrate.

[0075] After obtaining the equivalent capacitance and inductance through the unit structure parameters of the high-resistance surface, the impedance Z and resonant frequency ω0 of the parallel resonant circuit can be calculated, and their expressions are as follows:

[0076]

[0077] where j is the imaginary unit, j = √-1, ω is the angular frequency, L is the equivalent inductance, and C is the equivalent capacitance. The circular high-resistance surface was studied by scholars such as C.A. Balanis. Compared with the traditional square high-resistance surface, the proposed circular high-resistance surface structure has more advantages in integrating with antennas such as spiral antennas with curvature. Specifically, the working bandwidth will be increased by 10%, the radiation pattern is more stable and symmetric, and the gain is also significantly improved.

[0078] Please refer to Figure 6 . The radius R of the second-layer dielectric substrate is 102 mm, the width w r of the high-resistance surface metal patch 4 is 22 mm, the curvature w a of the high-resistance surface metal patch 4 is 14°, the gap width g r of the high-resistance surface metal patch 4 is 9 mm, and the gap curvature g a of the high-resistance surface metal patch 4 is 6°.

[0079] In some embodiments of the present application, both the first dielectric substrate 1 and the second dielectric substrate 2 are circular plates. The high-impedance surface metal patch 4 includes a plurality of first metal patches, a plurality of second metal patches, and a plurality of third metal patches. The plurality of first metal patches are sequentially arranged along the circumference of the second dielectric substrate 2 and enclose a first annular structure. The plurality of second metal patches are sequentially arranged along the circumference of the second dielectric substrate 2 and enclose a second annular structure. The plurality of third metal patches are sequentially arranged along the circumference of the second dielectric substrate 2 and enclose a third annular structure. The first annular structure, the second annular structure, and the third annular structure are nested in sequence. The area of the first metal patch is smaller than that of the second metal patch, and the area of the second metal patch is smaller than that of the third metal patch. With this structure, the reflection performance of the high-impedance surface metal patch 4 can be improved, and thus the gain of the reconfigurable antenna can be improved.

[0080] In some embodiments of the present application, the radius of the first dielectric substrate 1 is 60 mm - 70 mm, preferably 65 mm, and the thickness is 0.7 mm - 0.8 mm, preferably 0.76 mm. The radius of the second dielectric substrate 2 is 100 mm - 105 mm, preferably 102 mm, and the thickness is 1 mm - 1.5 mm, preferably 1.3 mm. With this structure, the dimensions of the first dielectric substrate 1 and the second dielectric substrate 2 are optimized, making it more convenient to process and form the first dielectric substrate 1 and the second dielectric substrate 2.

[0081] In some embodiments of the present application, a metal ground plane 5 is provided on the surface of the second dielectric substrate 2 away from the first dielectric substrate 1. With this structure, the reconfigurable antenna can be grounded through the metal ground plane 5.

[0082] In some embodiments of the present application, the materials of the spiral arm, the tapered impedance transformation line 6, the metal patch, and the metal ground plane 5 are all copper. With this structure, the performance of the reconfigurable antenna can be improved, and the cost of the antenna can be reduced.

[0083] Based on the above parameters, the reconfigurable antenna is simulated. Among them, Figure 8 shows the gain pattern of the reconfigurable antenna when exciting a right-handed circularly polarized wave; Figure 9 shows the gain pattern of the reconfigurable antenna when exciting a left-handed circularly polarized wave; Figure 10 shows the right-handed circular polarization axial ratio schematic diagram of the reconfigurable antenna; Figure 11 shows the left-handed circular polarization axial ratio schematic diagram of the reconfigurable antenna. It can be Figures 8 to 11 seen that in the present application, the axial ratio bandwidth in the right-handed circular polarization state is 1.61 - 4.24 GHz, the gain is 10.1 dBi, the axial ratio bandwidth in the left-handed circular polarization state is 1.88 - 3.67 GHz, the gain is 8.21 dBi, the gain of the antenna is improved, and the radiation pattern of the antenna is more stable and symmetric.

[0084] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0085] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is two or more unless otherwise specifically defined.

[0086] In the present invention, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0087] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A low-profile broadband polarization reconfigurable antenna, characterized in that: It comprises a first dielectric substrate and a second dielectric substrate which are stacked, wherein a planar four-arm Archimedean spiral antenna is arranged on a surface of the first dielectric substrate away from the second dielectric substrate, and a high-resistance surface metal patch is arranged between the first dielectric substrate and the second dielectric substrate; The planar four-arm Archimedean spiral antenna includes four spiral arms extending along the Archimedean spiral line, the four spiral arms are centrally symmetrical and there is a gap between two adjacent spiral arms, and the high-resistance surface metal patch includes a plurality of metal patches distributed in sequence along the circumference of the second dielectric substrate.

2. The low-profile broadband polarization reconfigurable antenna according to claim 1, characterized in that: It also includes a coaxial feeding wire and a coaxial feeding probe. The first dielectric substrate is provided with a first feeding hole, and the second dielectric substrate is provided with a second feeding hole. The coaxial feeding probe passes through the second feeding hole and the first feeding hole in sequence to feed the planar four-arm Archimedean spiral antenna. One end of the coaxial feeding wire is connected to the coaxial feeding probe, and the other end is used to be connected to a digital amplitude and phase control circuit.

3. The low-profile broadband polarization reconfigurable antenna according to claim 2, characterized in that: There are four first feeding holes and they are distributed on the central side of the first dielectric substrate, there are four second feeding holes and they are distributed on the central side of the second dielectric substrate, and the four first feeding holes correspond to the four second feeding holes one by one; There are four coaxial feeding wires and four coaxial feeding probes, and the four coaxial feeding probes are respectively inserted into the four first feeding holes, and the four coaxial feeding wires are respectively connected to the four coaxial feeding probes.

4. The low-profile broadband polarization reconfigurable antenna according to claim 3, characterized in that: Four conical impedance transformation lines are also provided on the surface of the first dielectric substrate away from the second dielectric substrate, the first ends of the four conical impedance transformation lines are respectively connected to the four coaxial feeding probes, and the second ends of the four conical impedance transformation lines are respectively connected to the four spiral arms; The cross-sectional area of ​​the first end of the tapered impedance transformation line is greater than the cross-sectional area of ​​the second end of the tapered impedance transformation line, and the cross-sectional area of ​​the tapered impedance transformation line gradually decreases from the first end to the second end of the tapered impedance transformation line.

5. The low-profile broadband polarization reconfigurable antenna according to claim 4, characterized in that: The four conical impedance transformation lines are all spiral structures extending along the Archimedean spiral line, and the four conical impedance transformation lines are centrally symmetrical structures.

6. The low-profile broadband polarization reconfigurable antenna according to claim 5, characterized in that: The inner diameter of the tapered impedance transformation line is 5.1 mm-5.2 mm, the width of the first end of the tapered impedance transformation line is 1.5 mm-1.9 mm, and the width of the second end of the tapered impedance transformation line is 0.4 mm-0.5 mm; The width of one end of the spiral arm connected to the conical impedance transformation line is equal to the width of the second end of the conical impedance transformation line, and the inner diameter of the spiral arm is 13.75 mm-13.8 mm.

7. The low-profile broadband polarization reconfigurable antenna according to claim 1, characterized in that: The first dielectric substrate and the second dielectric substrate are both circular plates, and the high-resistance surface metal patches include a plurality of first metal patches, a plurality of second metal patches, and a plurality of third metal patches; A plurality of the first metal patches are sequentially arranged along the circumference of the second dielectric substrate to form a first annular structure, a plurality of the second metal patches are sequentially arranged along the circumference of the second dielectric substrate to form a second annular structure, and a plurality of the third metal patches are sequentially arranged along the circumference of the second dielectric substrate to form a third annular structure; The first annular structure, the second annular structure and the third annular structure are nested in sequence, the area of ​​the first metal patch is smaller than the area of ​​the second metal patch, and the area of ​​the second metal patch is smaller than the area of ​​the third metal patch.

8. The low-profile broadband polarization reconfigurable antenna according to claim 7, characterized in that: The radius of the first dielectric substrate is 60 mm-70 mm, and the thickness is 0.7 mm-0.8 mm; The radius of the second dielectric substrate is 100 mm-105 mm, and the thickness is 1 mm-1.5 mm.

9. The low-profile broadband polarization reconfigurable antenna according to claim 4, characterized in that: A metal grounding plate is disposed on a surface of the second dielectric substrate which is away from the first dielectric substrate.

10. The low-profile broadband polarization reconfigurable antenna according to claim 9, characterized in that: The spiral arm, the conical impedance transformation line, the metal patch and the metal ground plate are all made of copper.

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