A Low-Profile Circularly Polarized Frequency Reconfigurable Antenna

Abstract

The present invention discloses a low-profile circularly polarized frequency-reconfigurable antenna, which is characterized by comprising a top-layer metasurface structure, an upper dielectric substrate, an antenna feeding structure, a lower dielectric substrate, a metal floor with a slot, and a metal reflector, which are distributed in sequence from top to bottom. Among them, the top-layer metasurface structure is formed by periodically extending a plurality of identical metasurface units, and the metasurface unit is also connected with a first PIN diode and a first patch capacitor; the antenna feeding structure includes a DC bias structure and a microstrip feeding line structure; the metal floor with a slot includes a slot structure located in the middle of the metal bottom plate, a second PIN diode is arranged inside the slot structure, and a second patch capacitor is arranged at the edge of the slot structure; the metallized vias are used to connect the top-layer metal patch, the antenna feeding structure and the metal floor with a slot. By loading the metasurface structure as the radiator of the antenna, the profile height can be reduced, and the circularly polarized radiation effect of the antenna is achieved.

Description

Technical Field

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

[0002] The characteristic of a frequency reconfigurable antenna is that the resonant frequency can be switched within one or more frequency bands, including the switching between single frequency and single frequency, single frequency and multi-frequency, and multi-frequency and multi-frequency. Since the resonant frequency is mainly related to the size and aperture of the structure, by adjusting the effective electrical length or the resonant length of the radiation slot, the resonant frequency of the antenna can be changed. In practical applications, the most commonly used is electrical modulation. Specifically, PIN diodes or variable capacitors are used to change the antenna structure, so that the radiation slot or the effective electrical length changes, thereby reconfiguring the operating frequency. The difficulty lies in how to keep other radiation characteristics such as radiation pattern and polarization mode stable while changing the resonant frequency.

[0003] As an important index for measuring an antenna, aiming at problems such as the high profile height and narrow reconfigurable state bandwidth of traditional reconfigurable antennas, different forms of frequency reconfigurable antennas are studied, and an antenna with a low profile height and good reconfigurable effect is selected as the basic antenna for design. At the same time, because an antenna is a device highly dependent on shape and size, it is necessary to ensure that the design of the external DC control system does not affect the radiation characteristics of the antenna, and at the same time, accurately drive the diodes loaded on the antenna.

[0004] The technologies for realizing single reconfiguration of an antenna can be divided into two categories: mechanical method and electrical control method. The mechanical reconfiguration has the disadvantages of slow speed, limited space, complex control, and easy influence on accuracy by mechanical errors; the electrical control method has prominent advantages such as fast response speed, high integration, and flexible design, but the structure is relatively complex.

[0005] With the development of reconfigurable technologies, frequency-reconfigurable antennas have developed rapidly in the past decade. However, existing frequency-reconfigurable antennas generally have a narrow operating bandwidth, a high profile, or no circular polarization performance due to reasons such as the antenna's own structure. For example, Lei Ge et al. proposed a new type of frequency-reconfigurable antenna based on a circular monopole patch antenna in their published paper "Frequency-Reconfigurable Low-Profile Circular Monopolar Patch Antenna" (IEEE Transactions on Antennas and Propagation). The antenna includes a centrally-fed circular patch surrounded by four sector patches. By introducing eight varactor diodes and changing the reverse bias voltage of the varactor diodes, a frequency-reconfigurable effect from 1.64 GHz to 2.12 GHz was achieved. However, even by increasing the number of surrounding sector patches and varactor diodes, the maximum operating bandwidth does not exceed 40%, and to ensure the same radiation pattern at different frequencies, a centrally-fed method was adopted, making it difficult to achieve circular polarization radiation. Summary of the Invention

[0006] To solve the above problems existing in the prior art, the present invention provides a low-profile circularly polarized frequency-reconfigurable antenna, including a slot antenna loaded with a metasurface structure and a single-chip microcomputer control system connected thereto, for solving the problem of circularly polarized frequency reconfiguration. This antenna can achieve circularly polarized frequency-reconfigurable characteristics in three states within the bandwidth range of 4 GHz - 9 GHz. The technical problems to be solved by the present invention are realized through the following technical solutions:

[0007] The present invention provides a low-profile circularly polarized frequency-reconfigurable antenna, including a top-layer metasurface structure, an upper dielectric substrate, an antenna feeding structure, a lower dielectric substrate, a metal floor with a slot, and a metal reflector, which are distributed in sequence from top to bottom. Among them,

[0008] The top-layer metasurface structure is disposed on the upper surface of the upper dielectric substrate and is formed by periodic extension of a plurality of identical metasurface units. The metasurface unit is also connected to a first PIN diode and a first patch capacitor;

[0009] The antenna feeding structure is printed on the lower surface of the upper dielectric substrate and includes a DC bias structure and a microstrip feeding structure. The DC bias structure includes a first sub-structure and a second sub-structure located on both sides of the upper surface of the upper dielectric substrate. The first sub-structure and the second sub-structure respectively include a plurality of metal wires, and each metal wire is connected to the first PIN diode through a metallized via; the microstrip feeding structure is located between the first sub-structure and the second sub-structure;

[0010] The metal floor with a gap is disposed on the lower surface of the lower dielectric substrate, and includes a gap structure located in the middle of the metal floor. A second PIN diode is disposed inside the gap structure, and a second patch capacitor is disposed at the edge of the gap structure.

[0011] The metal reflector is disposed below the metal floor and is spaced apart from the metal floor.

[0012] The inner surface of the metallized via is coated with a metal layer. The metallized via penetrates up and down and is used to connect the top metasurface structure, the antenna feed structure, and the metal floor with a gap.

[0013] In an embodiment of the present invention, the top metasurface structure includes n×n metasurface units. Each metasurface unit is in a strip shape and is inclined 45° in the same direction, so that the metasurface units at different rows and corresponding positions are on the same straight line, where n≥4.

[0014] In an embodiment of the present invention, adjacent metasurface units in the same inclined direction are connected by the first PIN diode; a first patch capacitor is disposed on the side of each metasurface unit connected by the first PIN diode, and the metasurface unit is connected to the metal floor with a gap through the first patch capacitor for performing AC-DC isolation of signals.

[0015] In an embodiment of the present invention, the microstrip feeder structure is vertically disposed between the left sub-structure and the right sub-structure of the DC bias structure, and a circular metal patch is disposed at a position near the lower end of the microstrip feeder structure.

[0016] In an embodiment of the present invention, the left sub-structure and the right sub-structure respectively include metal wires and socket structures corresponding to each metal wire. The socket structures of the left sub-structure and the right sub-structure are symmetrically distributed and are both used to connect an external DC control system.

[0017] In an embodiment of the present invention, the microstrip feeder structure and the DC bias structure are respectively connected to an external DC control system through the metallized vias.

[0018] In an embodiment of the present invention, the gap structure includes two square grooves and a rectangular groove connecting the two square grooves. A second PIN diode placed in the same direction is disposed inside each of the two square grooves; a second patch capacitor placed in the same direction is disposed outside each of the two square grooves.

[0019] In an embodiment of the present invention, two rectangular grooves and one circular groove are formed on the metal reflector. Among them, the two rectangular grooves are arranged in parallel along the long axis direction, and the circular groove is located between the two rectangular grooves.

[0020] In an embodiment of the present invention, the distance between the metal floor with a slit and the metal reflector is 2.4 mm.

[0021] In an embodiment of the present invention, both the upper dielectric substrate and the lower dielectric substrate are made of a non-metallic material with a dielectric constant of 4.5; the materials of the top metasurface structure, the metal floor with a slit, and the metal reflector are all copper.

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

[0023] 1. The present invention proposes a circularly polarized frequency reconfigurable antenna loaded with a metasurface structure. By loading the metasurface structure as the radiator of the antenna, the profile height can be reduced, and the circularly polarized radiation effect of the antenna is achieved; using PIN diodes as the electronic control components has the advantages of fast response speed, stable performance, and the voltage fluctuation will not affect the switching state of the PIN diodes; using an external DC control system reduces the complexity of the control system and can control the state of the antenna in real time.

[0024] 2. The low-profile circularly polarized frequency reconfigurable antenna of the present invention can switch the voltage loaded on the switching diode in real time by controlling the external circuit, so as to switch the working state of the antenna in real time; it can switch functions according to the actual scenario at any time, so it has great application value.

[0025] 3. The low-profile circularly polarized frequency reconfigurable antenna of the present invention has the characteristics of wide frequency band coverage, flexible control, diverse functions, and strong practicability. The metasurface can realize three circularly polarized frequency reconfigurable functions in the frequency range of 4 GHz - 9 GHz. The frequency reconfigurable antenna meets the requirements of different frequency band communications, can control the working state of the antenna in real time through an external circuit, and avoids the coupling problem caused by the placement of antennas in different frequency bands. It has a broad application scenario in the field of wireless communication.

[0026] The present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0027] Figure 1 is a schematic structural diagram of a low-profile circularly polarized frequency reconfigurable antenna provided by an embodiment of the present invention;

[0028] Figure 2 is a schematic structural diagram of a top metasurface structure provided by an embodiment of the present invention;

[0029] Figure 3 is a schematic structural diagram of an antenna feeding structure provided by an embodiment of the present invention;

[0030] Figure 4 is a schematic structural diagram of a metal floor with a slit provided by an embodiment of the present invention;

[0031] Figure 5 is a schematic structural diagram of a metal reflector provided by an embodiment of the present invention;

[0032] Figure 6 is a schematic diagram of the working principle of a low-profile circularly polarized frequency reconfigurable antenna provided by an embodiment of the present invention;

[0033] Figure 7 are the parameters of a low-profile circularly polarized frequency reconfigurable antenna provided by an embodiment of the present invention when operating in the low-frequency band;

[0034] Figure 8 are the parameters of a low-profile circularly polarized frequency reconfigurable antenna provided by an embodiment of the present invention when operating in the medium-frequency band;

[0035] Figure 9 are the parameters of a low-profile circularly polarized frequency reconfigurable antenna provided by an embodiment of the present invention when operating in the high-frequency band.

[0036] Description of reference numerals:

[0037] 1 - top-layer metasurface structure; 11 - metasurface unit; 12 - first PIN diode; 13 - first patch capacitor; 2 - upper dielectric substrate; 3 - antenna feeding structure; 31 - DC bias structure; 311 - metal wire; 312 - socket structure; 32 - microstrip feeder structure; 33 - circular metal patch; 4 - lower dielectric substrate; 5 - metal floor with a slit; 51 - slit structure; 52 - second PIN diode; 53 - second patch capacitor; 6 - metal reflector; 61 - rectangular groove; 62 - circular groove; 7 - metallized via. Detailed implementation manners

[0038] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following provides a detailed description of a low-profile circularly polarized frequency reconfigurable antenna according to the present invention in conjunction with the accompanying drawings and specific implementation manners.

[0039] The foregoing and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and specific understanding of the technical means and effects adopted by the present invention to achieve the predetermined purpose can be obtained. However, the accompanying drawings are only for reference and illustration, and are not used to limit the technical solution of the present invention.

[0040] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant is intended to cover non-exclusive inclusion, so that an article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed. Without further limitation, an element defined by the statement "including one..." does not exclude the presence of another identical element in the article or device including the said element.

[0041] This embodiment provides a low-profile circularly polarized frequency-reconfigurable antenna with a loaded metasurface structure that can operate at different frequency bands. The metasurface structure loaded on the upper layer of the antenna is formed by the periodic extension of exactly the same metasurface unit in the xy two-dimensional plane. Each group of metasurface units isolates the AC and DC signals through a capacitor, and then is connected to an I / O port of the single-chip microcomputer control system through a DC feeder, and the state of the metasurface array is controlled by computer input.

[0042] Please refer to Figure 1From 0 to 5, the low-profile circularly polarized frequency reconfigurable antenna of this embodiment includes a top-layer metasurface structure 1, an upper dielectric substrate 2, an antenna feeding structure 3, a lower dielectric substrate 4, a metal floor 5 with a slot, and a metal reflector 6 that are distributed in sequence from top to bottom. Among them, the top-layer metasurface structure 1 is arranged on the upper surface of the upper dielectric substrate 2 and is formed by periodic extension of a plurality of exactly the same metasurface units 11. The metasurface unit 11 is also connected with a first PIN diode 12 and a first patch capacitor 13; the antenna feeding structure 3 is printed on the lower surface of the upper dielectric substrate 2 and includes a DC bias structure 31 and a microstrip feeding structure 32. The DC bias structure 31 includes a first sub-structure and a second sub-structure located on both sides of the upper surface of the upper dielectric substrate 2. The first sub-structure and the second sub-structure respectively include a plurality of metal wires, and each metal wire is connected to the first PIN diode 12 through a metallized via 7; the microstrip feeding structure 32 is located between the first sub-structure and the second sub-structure; the metal floor 5 with a slot is arranged on the lower surface of the lower dielectric substrate 4 and includes a slot structure 51 located in the middle of the metal floor. A second PIN diode 52 is arranged inside the slot structure 51, and a second patch capacitor 53 is arranged at the edge of the slot structure 51; the metal reflector 6 is arranged below the metal floor 5 and is spaced from the metal floor 5; the inner surface of the metallized via 7 is coated with a metal layer, and the metallized via 7 penetrates up and down and is used to connect the top-layer metasurface structure 1, the antenna feeding structure 3, and the metal floor 5 with a slot.

[0043] Specifically, the top-layer metasurface structure 1 includes n×n metasurface units 11. Each metasurface unit 11 is in a strip shape and is inclined 45° in the same direction, so that the metasurface units 11 located in different rows and corresponding positions are on the same straight line, where n≥4. Adjacent metasurface units 11 in the same inclined direction are connected by the first PIN diode 12; a first patch capacitor 13 is arranged on the side of each metasurface unit 11 connected by the first PIN diode 12, and the metasurface unit 11 is connected to the metal floor 5 with a slot through the first patch capacitor 13 for AC and DC isolation of signals.

[0044] Please refer to Figure 2, in this embodiment, the total number of metasurface units 11 is 4×4, which are evenly divided into 4 groups along the x-direction to form a metasurface array. The number of metasurface units 11 contained in this metasurface array is 16. Each metasurface unit 11 is arranged to be inclined at 45° along the same direction. The adjacent metasurface units 11 on the same straight line are connected by the first PIN diodes 12, and there are a total of 9 first PIN diodes 12. The metasurface unit 11 is connected to the metal floor 5 with a slit by using a first patch capacitor 13 with a capacitance value of 10 nF for AC-DC isolation of signals. The length of the metasurface unit 11 is L1, the width is W1, and the spacing between units is D1. Preferably, L1 = 5.26 mm, W1 = 0.54 mm, and D1 = 4.4 mm. The first PIN diodes 12 are arranged at a 45° angle, and the operating frequency of the antenna is regulated by changing the bias voltage across the diodes.

[0045] The arrangement of the 4×4 metasurface units 11 is as follows: 4 are evenly arranged in each row and each column, and each metasurface unit 11 is inclined at 45° along the same direction, forming a square as a whole. The number of units on the diagonal of this square is 4, the number of units close to the diagonal is 3, the number of units on the second-nearest diagonal is 2, and the number of units at the position farthest from the diagonal is 1.

[0046] In this embodiment, the thickness of the upper dielectric substrate 2 is H1, the thickness of the middle dielectric substrate 4 is H2, and the side lengths of the two dielectric substrates are both P1. Among them, H1 = 2 mm, H2 = 0.5 mm, and P1 = 30 mm; the materials of the upper dielectric substrate 2 and the lower dielectric substrate 4 both use non-metallic materials with a dielectric constant of 4.5, preferably Arlon AD450, and the loss tangent is 0.0035. The upper dielectric substrate 2 and the middle dielectric substrate 4 are separated by an insulating resin gasket.

[0047] Furthermore, an antenna feeding structure 3 and a metal floor 5 with a slit are respectively provided on the upper and lower surfaces of the lower dielectric substrate. Among them, the antenna feeding structure includes the coaxial backfeeding structure of the antenna and the external DC control system of all PIN diodes of the antenna. PIN diodes and capacitors are provided on the lower metal floor with a slit; the metallized vias 7 pass through the upper dielectric substrate and are connected to the external DC control system on the back of the upper dielectric substrate; the control of each part of the PIN diodes on the antenna is connected to the external DC control system through DC feed lines, and the frequency reconfigurable function of the antenna is realized by switching the bias voltage on the PIN diodes.

[0048] Please refer to Figure 3, the antenna feeding structure 3 of this embodiment includes a DC bias structure 31 and a microstrip feeder structure 32, and the whole antenna feeding structure 3 is printed on the lower surface of the upper dielectric substrate 2. The DC bias structure 31 uses a metal wire with a line width of 0.3 mm and is connected to the upper first PIN diode 12 through a metallized via 7 to provide DC control for the first PIN diode 12. The microstrip feeder structure 32 is vertically arranged between the left sub-structure and the right sub-structure of the DC bias structure 31, and a circular metal patch 33 is arranged at a position near the lower end of the microstrip feeder structure 32. The left sub-structure and the right sub-structure respectively include a metal wire 311 and a socket structure 312 correspondingly connected to each metal wire 311. The socket structures of the left sub-structure and the right sub-structure are symmetrically distributed and are both used to connect an external DC control system. The microstrip feeder structure 32 and the DC bias structure 31 are respectively connected to an external DC control system through metallized vias 7.

[0049] The length of the microstrip feeder structure 32 is K1, the width is K2, and a circular metal patch 33 with a radius of R1 is placed. The circular metal patch 33 is for better slot coupling feeding. Preferably, K1 = 16 mm, K2 = 0.64 mm, and R1 = 1.28 mm.

[0050] Please refer to Figure 4 , on the lower surface of the lower dielectric substrate 4, a metal floor 5 with a slot is etched, including a slot structure 51 in the middle of the metal floor. A second PIN diode 52 is arranged inside the slot structure 51, and a second patch capacitor 53 is arranged at the edge of the slot structure 51.

[0051] In this embodiment, the slot structure 51 is in an "I" shape, including two square slots and a rectangular slot connecting the two square slots. A second PIN diode 52 placed in the same direction is arranged on the inner side of each of the two square slots; a second patch capacitor 53 placed in the same direction is arranged on the outer side of each of the two square slots.

[0052] Among them, the length of the rectangular slot is B2, the width is B3, the side length of the square slot is B1, and the side length of the metal floor 5 is P2. Preferably, B1 = 4 mm, B2 = 12 mm, B3 = 1 mm, and P2 = 25.7 mm. The distances from the two second PIN diodes 52 to the center of the rectangular slot are both 5 mm. Two second patch capacitors 53 with a capacitance value of 10 nF placed in the same direction are loaded at the outer edge of the square slot. The purpose is to not affect the current distribution on both sides of the slot, and at the same time ensure the isolation of the DC signal and provide a bias voltage for the second PIN diode 52.

[0053] Continue to refer to Figure 5, a metal reflector 6 is placed at a height H3 from the antenna feed structure 3. The metal reflector 6 is a square metal plate with a side length P3. Two rectangular grooves 61 and one circular groove 62 are formed on the metal reflector 6. Among them, the two rectangular grooves 61 are arranged in parallel along the long axis direction, and the circular groove 62 is located between the two rectangular grooves 61. The rectangular groove 61 has a length of M1 and a width of M2, so that the external DC control system can be connected to the frequency reconfigurable antenna. The radius of the circular groove 62 is R2, which is used for antenna coupling feeding from the back. Preferably, H3 = 2.4 mm, M1 = 13 mm, M2 = 4 mm, and R2 = 2.5 mm. The interval between the metal floor 5 with a slit and the metal reflector 6 is 2.4 mm

[0054] In addition, both the upper dielectric substrate 2 and the lower dielectric substrate 4 are made of Arlon AD450 with a dielectric constant of 4.5 and a loss tangent of 0.0035; the materials of the top metasurface structure 1, the metal floor 5 with a slit, and the metal reflector 6 are all copper.

[0055] The low-profile circularly polarized frequency reconfigurable antenna in this embodiment loads the metasurface structure as the radiator of the antenna instead of the traditional structure that uses the metasurface as the reflection floor of the antenna. The metasurface array is connected by PIN diodes, and the operating frequency of the antenna is selected through the state of the PIN diodes. A structure with a loaded capacitor is adopted, which not only does not change the current distribution at the floor slit but also provides a DC bias voltage for the PIN diodes. The antenna can achieve the circularly polarized frequency reconfigurable characteristic in three states within the bandwidth range of 4 GHz - 9 GHz.

[0056] Referring to Figures 1 - 5 , in order to verify the feasibility of the low-profile circularly polarized frequency reconfigurability, the antenna in this embodiment is processed by PCB technology, and the switching diodes are soldered to the corresponding positions of the antenna through wave soldering technology.

[0057] The overall structure of the antenna in this embodiment adopts the design of a microstrip metasurface antenna. The top-loaded metasurface unit is an inclined 45° metal rectangular structure. The metasurface unit is periodically expanded along the xy axis to form a 4×4 metasurface array, and the metasurface unit is excited by slot coupling feeding to obtain good impedance matching. After the design of the basic metasurface antenna is completed, the DC drive circuit of the antenna is designed to facilitate the control of the states of the loaded electronic control devices. Finally, the designed antenna is physically processed and the diodes are driven by a battery pack to facilitate the design of the voltage and current of the external DC control system.

[0058] The antenna as a whole is divided into two parts. The first part is the bottom slot coupling structure, which can control the antenna to operate in the high - frequency or low - frequency region by changing the on - and off states of the diodes loaded on the slot. The second part is the 4×4 metasurface structure. By changing the on - and off states of the diodes loaded on the metasurface, the reactances in two directions can be changed, thereby radiating circularly polarized waves.

[0059] Please refer to Figure 6 , Figure 6 which is a schematic diagram of the working principle of a low - profile circularly polarized frequency - reconfigurable antenna provided by an embodiment of the present invention. The radiated electric field E of the antenna is decomposed into a component E2 perpendicular to the 45 - degree oblique direction and a component E1 along the direction of the metal patch. The presence of the metal wire causes the reactances in these two directions to be unequal. The impedance Z2 in the E2 direction increases inductively, and the impedance Z1 in the E1 direction increases capacitively. Therefore, the phase of the electric - field component E2 leads the phase of E1. By changing the on - and off states of the diodes loaded on the metasurface, the reactance along the E1 direction can be changed. When the amplitude of E2 is equal to that of E1 and the phase of E2 leads the phase of E1 by 90 degrees, circularly polarized waves can be radiated.

[0060] The following further describes the effects of the low - profile circularly polarized frequency - reconfigurable antenna according to the embodiments of the present invention in combination with simulation experiments. The electromagnetic characteristics of the specific low - profile circularly polarized frequency - reconfigurable antenna are analyzed as follows.

[0061] To illustrate the electromagnetic characteristics of the multi - dimensionally adjustable digital - coding metasurface unit, the commercial simulation software ANSYS HFSS is used to Figure 1 model and simulate the unit structure.

[0062] Please refer to Figure 7 , Figure 7 which are the reflection coefficient, axial ratio, and radiation pattern parameters of a low - profile circularly polarized frequency - reconfigurable antenna provided by an embodiment of the present invention when operating in the low - frequency region. The simulation results show that by controlling the states of the PIN diodes loaded on the antenna, the low - profile circularly polarized frequency - reconfigurable antenna satisfies the functions of circular polarization and frequency reconfiguration in the low - frequency operating region.

[0063] Please refer to Figure 8 , Figure 8 which are the reflection coefficient, axial ratio, and radiation pattern parameters of a low - profile circularly polarized frequency - reconfigurable antenna provided by an embodiment of the present invention when operating in the middle - frequency region. The simulation results show that the antenna satisfies the functions of circular polarization and frequency reconfiguration in the middle - frequency operating region.

[0064] Please refer to Figure 9 , Figure 9They are the reflection coefficient, axial ratio, and radiation pattern parameters of a low-profile circularly polarized frequency-reconfigurable antenna provided by an embodiment of the present invention when operating in the high-frequency region. The simulation results show that the antenna satisfies the circular polarization and frequency-reconfigurability functions in the high-frequency operating region.

[0065] The present invention proposes a circularly polarized frequency-reconfigurable antenna loaded with a metasurface structure. By loading the metasurface structure as the radiator of the antenna, the profile height can be reduced, and the circular polarization radiation effect of the antenna is achieved. Using PIN diodes as the electrical control components has the advantages of fast response speed, stable performance, and the switching state of the PIN diodes not being affected by voltage fluctuations. Using an external DC control system reduces the complexity of the control system and can simultaneously control the state of the antenna in real time. The present invention can switch the voltage applied to the switching diodes in real time by controlling the external circuit through a computer, thereby switching the operating state of the antenna in real time. The present invention can switch functions according to the actual scenario at any time, thus having great application value. The present invention has the characteristics of a wide frequency band coverage range, flexible control, diverse functions, and strong practicability. The metasurface can achieve three circularly polarized frequency-reconfigurable functions in the frequency range of 4 GHz - 9 GHz.

[0066] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and 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 belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A low-profile circularly polarized frequency reconfigurable antenna, characterized in that, It includes a top metasurface structure (1), an upper dielectric substrate (2), an antenna feeding structure (3), a lower dielectric substrate (4), a metal floor (5) with a slit, and a metal reflector (6) which are distributed in sequence from top to bottom. Among them, The top metasurface structure (1) is disposed on the upper surface of the upper dielectric substrate (2) and is formed by periodic extension of a plurality of identical metasurface units (11). The metasurface unit (11) is also connected with a first PIN diode (12) and a first patch capacitor (13); The antenna feeding structure (3) is printed on the lower surface of the upper dielectric substrate (2) and includes a DC bias structure (31) and a microstrip feeding line structure (32). The DC bias structure (31) includes a first sub-structure and a second sub-structure located on both sides of the upper surface of the upper dielectric substrate (2). The first sub-structure and the second sub-structure respectively include a plurality of metal wires, and each metal wire is connected to the first PIN diode (12) through a metallized via (7); the microstrip feeding line structure (32) is located between the first sub-structure and the second sub-structure; The metal floor (5) with a slit is disposed on the lower surface of the lower dielectric substrate (4) and includes a slit structure (51) located in the middle of the metal floor. A second PIN diode (52) is disposed inside the slit structure (51), and a second patch capacitor (53) is disposed at the edge of the slit structure (51); The metal reflector (6) is disposed below the metal floor (5) and is spaced from the metal floor (5); The inner surface of the metallized via (7) is coated with a metal layer. The metallized via (7) penetrates up and down and is used to connect the top metasurface structure (1), the antenna feeding structure (3), and the metal floor (5) with a slit.

2. The low-profile circularly polarized frequency reconfigurable antenna according to claim 1, characterized in that The top metasurface structure (1) includes n×n metasurface units (11). Each metasurface unit (11) is in a strip shape and is disposed at an inclination of 45° in the same direction, so that the metasurface units (11) at different rows and corresponding positions are on the same straight line, where n≥4.

3. The low-profile circularly polarized frequency reconfigurable antenna according to claim 2, characterized in that The adjacent metasurface units (11) in the same inclined direction are connected by the first PIN diode (12); a first patch capacitor (13) is disposed on the side of each metasurface unit (11) connected by the first PIN diode (12), and the metasurface unit (11) is connected to the metal floor (5) with a slit through the first patch capacitor (13) for AC-DC isolation of signals.

4. The low-profile circularly polarized frequency reconfigurable antenna according to claim 1, characterized in that, The microstrip feeding line structure (32) is vertically disposed between the left sub-structure and the right sub-structure of the DC bias structure (31), and a circular metal patch (33) is disposed at a position near the lower end of the microstrip feeding line structure (32).

5. The low-profile circularly polarized frequency reconfigurable antenna according to claim 4, characterized in that The left sub-structure and the right sub-structure respectively include metal wires (311) and socket structures (312) correspondingly connected to each metal wire (311). The socket structures of the left sub-structure and the right sub-structure are symmetrically distributed and are both used to connect to an external DC control system.

6. The low-profile circularly polarized frequency reconfigurable antenna according to claim 4, wherein The microstrip feeder structure (32) and the DC bias structure (31) are respectively connected to an external DC control system through the metallized vias (7).

7. The low-profile circularly polarized frequency reconfigurable antenna according to claim 1, characterized in that, The slot structure (51) includes two square slots and a rectangular slot connecting the two square slots. A second PIN diode (52) placed in the same direction is respectively arranged on the inner sides of the two square slots; a second patch capacitor (53) placed in the same direction is respectively arranged on the outer sides of the two square slots.

8. The low-profile circularly polarized frequency reconfigurable antenna according to claim 7, wherein Two rectangular grooves (61) and a circular groove (62) are formed on the metal reflector (6). Among them, the two rectangular grooves (61) are arranged in parallel along the long axis direction, and the circular groove (62) is located between the two rectangular grooves (61).

9. The low-profile circularly polarized frequency reconfigurable antenna according to claim 1, wherein The distance between the metal floor (5) with slots and the metal reflector (6) is 2.4 mm.

10. The low-profile circularly polarized frequency reconfigurable antenna according to any one of claims 1 to 9, characterized in that, Both the upper dielectric substrate (2) and the lower dielectric substrate (4) are made of a non-metallic material with a dielectric constant of 4.5; the materials of the top metasurface structure (1), the metal floor (5) with slots, and the metal reflector (6) are all copper.

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