Low-profile broadband four-polarization reconfigurable metasurface antenna

Abstract

The invention relates to a low-profile broadband four-polarization reconfigurable metasurface antenna, and belongs to the technical field of radio frequency microwaves. The antenna is composed of a metasurface dual-line polarized antenna and a reconfigurable feed network. The dual-polarization metasurface antenna structure designed based on characteristic mode analysis can effectively excite two groups of degenerate linear polarization radiation modes in a working frequency band, so that the broadband performance is realized. The reconfigurable feed network controls the transmission paths of two paths of output signals through the on-off of a PIN diode, can generate single-port output signals of two different transmission paths and double-port output signals of two different transmission paths, feeds the signals into an orthogonally placed L-shaped probe structure, carries out coupled feed on the metasurface radiation patch of the antenna, and achieves the purpose of improving the antenna performance. Therefore, the excitation states of the two orthogonal linear polarization modes of the dual-polarized antenna are controlled, and finally the four different polarization modes are switched. The antenna has the advantages of being low in profile and compact in size, and switching of four broadband polarization modes can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency microwave technology and relates to a low-profile broadband four-polarized reconfigurable metasurface antenna. Background Technology

[0002] With the development of wireless communication systems, the number of antennas is constantly increasing, leading to increasingly serious electromagnetic interference problems between antennas and a heavier load on communication systems. In complex and variable channel environments, it is necessary to optimize signal transmission and reception, mitigate the interference to signal quality caused by the increased number of antennas, increase the capacity of communication systems, and improve their stability and adaptability. Polarization-reconfigurable antennas can achieve flexible switching of polarization modes, realize multiplexing, increase channel capacity, reduce the impact of multipath effects, and improve polarization mismatch tolerance, thereby improving the performance of communication systems. Therefore, polarization-reconfigurable antennas have become a highly anticipated research direction in the field of modern wireless communication.

[0003] In practical applications, polarization-reconfigurable antennas can adapt to the operational requirements of different application scenarios by adjusting their matching and radiation characteristics. For example, in complex electromagnetic environments, when the received signal exhibits random polarization characteristics due to multipath effects or interference, using a polarization-reconfigurable antenna as the receiver of a communication system can effectively solve the polarization mismatch problem and significantly improve communication quality. This type of antenna, by integrating multi-polarization functionality, can replace multiple independent antennas in traditional communication systems. This not only avoids mutual coupling interference between multiple antennas but also simplifies the system architecture, reduces system costs, and provides greater freedom for the miniaturization and integration design of communication equipment. Currently, there are three main technologies for realizing polarization reconfigurability: the first is to reconfigure the antenna radiation structure mechanically or electronically, using changes in structural parameters to achieve polarization mode switching; the second is based on metamaterial technology, dynamically adjusting the spatial distribution or electromagnetic parameters of metasurface units to change the antenna surface current distribution to achieve polarization reconfiguration; and the third is to use a reconfigurable feed network design, integrating adjustable devices (such as PIN diodes) to control the excitation phase of the dual-polarized antenna, achieving on-demand switching of multi-polarization modes.

[0004] The paper "WU Y, SUN H, A low-profile wideband omnidirectional antenna with reconfigurable tri-polarization diversity[J]. AEU-International Journal of Electronics and Communications, 2024, 176: 155149." proposes a low-profile wideband omnidirectional tri-polarized reconfigurable antenna, consisting of a center-fed circular patch (generating vertically polarized electromagnetic waves) and a curved branch patch (generating horizontally polarized electromagnetic waves). Dynamic switching between linear polarization and left-hand / right-hand circular polarization is achieved by loading PIN diodes on the curved patch to control the current path. This design eliminates the need for a complex feed network, thus avoiding the additional insertion loss introduced by traditional feed networks. However, its DC bias circuit locally alters the current distribution on the antenna surface, affecting key parameters such as the antenna's radiation mode, gain, and directivity.

[0005] The paper "Kang L, Li H, Tang B, et al. Quad-Polarization-Reconfigurable Antenna with a Compact and Switchable Feed[J].IEEE Antennas and WirelessPropagation Letters,2021,20(4):548-552" proposes a compact quad-polarization reconfigurable loop patch antenna. It uses PIN diodes to form a reconfigurable feed network, allowing the antenna to dynamically switch between single-feed and dual-feed modes. In single-feed mode, it generates ±45° linear polarization radiation. In dual-feed mode, the feed structure is a switchable phase-shifting power divider, generating left-hand circular polarization and right-hand circular polarization radiation. However, this design has two limitations: first, the DC bias circuit is directly integrated on the radiator surface to control the switching of the PIN diodes, and the parasitic parameters introduced by the bias circuit interfere with the current distribution on the antenna surface, affecting antenna performance; second, the reconfigurable feed network is complex, requiring the integration of six independent DC bias channels, increasing hardware cost and layout difficulty.

[0006] Among them, the impedance bandwidth of the linearly polarized mode of the polarization-reconfigurable antenna in Reference 1 is only 13.44%, while the impedance bandwidths of the left-hand and right-hand circularly polarized modes are only 10.87% and 10.91%, respectively. In Reference 2, the impedance bandwidth of the linearly polarized mode of the polarization-reconfigurable antenna is only 10.7%, the impedance bandwidth of the circularly polarized mode is only 13.11%, and the 3dB axial ratio bandwidth is only 9.45%. It is evident that achieving a compact, broadband polarization-reconfigurable antenna while balancing impedance bandwidth and minimizing the impact of DC bias on antenna performance during polarization switching remains a significant challenge. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a low-profile broadband quad-polarized reconfigurable metasurface antenna, which solves the problems of existing polarization reconfigurable antennas that are difficult to balance impedance bandwidth and low profile, as well as the impact of DC bias on antenna performance during polarization switching.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A low-profile broadband four-polarized reconfigurable metasurface antenna has a structure comprising a fourth dielectric substrate, a third dielectric substrate, a second dielectric substrate, and a first dielectric substrate stacked sequentially.

[0010] The first dielectric substrate has multiple symmetrically arranged metasurface patch units on its upper surface; the second dielectric substrate has a first patch on its upper surface; the third dielectric substrate has a second patch on its upper surface; and the fourth dielectric substrate has a metal ground on its upper surface and a reconfigurable power supply network on its lower surface. The first and second patches are orthogonally arranged in space.

[0011] In addition, the antenna structure includes a first feed post and a second feed post. The first feed post passes through the fourth dielectric substrate, the metal ground, the third dielectric substrate, and the second dielectric substrate, and is connected to the first patch and the reconfigurable feed network, respectively. The second feed post passes through the fourth dielectric substrate, the metal ground, and the third dielectric substrate, and is connected to the second patch and the reconfigurable feed network, respectively. The connection between the first feed post and the first patch forms a first L-shaped probe structure, while the connection between the second feed post and the second patch also forms a second L-shaped probe structure. The two L-shaped probe structures are placed orthogonally.

[0012] Furthermore, the multiple symmetrically arranged metasurface patch units are arranged in a 3×3 symmetrical configuration, including five rectangular patch units and four rectangular patch units with etched H-shaped slots. The four rectangular patch units with etched H-shaped slots are symmetrically distributed in the east, south, west, and north directions relative to the center of the first dielectric substrate.

[0013] Furthermore, the reconfigurable power supply network includes an input port microstrip line, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, a seventh microstrip line, an eighth microstrip line, a ninth microstrip line, a tenth microstrip line, and an eleventh microstrip line, three capacitors, three RF chokes, three DC bias pins, and four PIN diodes: a first PIN diode, a second PIN diode, a third PIN diode, and a fourth PIN diode.

[0014] The lengths of the fourth, fifth, eighth, ninth, tenth, and eleventh microstrip lines are all one-eighth of the wavelength corresponding to the antenna's operating center frequency. The lengths of the second, third, sixth, and seventh microstrip lines are all one-quarter of the wavelength corresponding to the antenna's operating center frequency.

[0015] The input port microstrip line is connected to the first microstrip line via a capacitor; the first microstrip line is connected to the second microstrip line via a first PIN diode, and to the third microstrip line via a second PIN diode; the second microstrip line is simultaneously connected to the fourth and sixth microstrip lines; the third microstrip line is simultaneously connected to the fifth and seventh microstrip lines; the fourth microstrip line is connected to the fifth microstrip line via a third PIN diode; and the eighth microstrip line is connected to the ninth microstrip line via a fourth PIN diode. The capacitor's function is to isolate DC signals and prevent DC signals from interfering with RF signals.

[0016] The sixth microstrip line is directly connected to the eighth microstrip line, and the eighth microstrip line is connected to the tenth microstrip line through a capacitor. The other end of the tenth microstrip line serves as an output terminal of the reconfigurable feed network and is connected to the first feed post. The seventh microstrip line is directly connected to the ninth microstrip line, and the ninth microstrip line is connected to the eleventh microstrip line through a capacitor. The other end of the eleventh microstrip line serves as another output terminal of the reconfigurable feed network and is connected to the second feed post. At the midpoint of each of the first, sixth, and seventh microstrip lines, an RF choke is connected to a DC bias pin. The function of the RF choke is to prevent radio frequency signals from entering the DC bias. A bias voltage is applied to each of the DC bias pins, and a forward voltage is provided to the positive terminal of the PIN diode through the RF choke.

[0017] By changing the bias voltage applied to the DC bias pin, the on / off state of the PIN diode can be controlled, enabling the reconfigurable feed network to achieve single-port output signals with two different transmission paths and dual-port output signals with two different transmission paths. This allows the reconfigurable metasurface antenna to switch between four polarization modes: x-axis linear polarization, y-axis linear polarization, left-hand circular polarization, and right-hand circular polarization. Specifically, the diode on / off states for different polarization modes are as follows:

[0018] When the first PIN diode is turned on, and the second, third, and fourth PIN diodes are turned off, the radio frequency signal is transmitted to only one output port P through the input port microstrip line, the first microstrip line, the second microstrip line, the sixth microstrip line, and the tenth microstrip line. ox Then, the first L-shaped probe feeds the metasurface radiating patch to generate a single-port output signal. This antenna is in x-direction linear polarization mode.

[0019] When the second PIN diode is turned on and the first, third, and fourth PIN diodes are turned off, the RF signal is transmitted to only one output port P through the input port microstrip line, the first microstrip line, the third microstrip line, the seventh microstrip line, and the eleventh microstrip line. oy Then, the second L-shaped probe feeds the metasurface radiating patch to generate a single-port output signal. This antenna is in the y-direction linear polarization mode.

[0020] When the first, third, and fourth PIN diodes are turned on and the second PIN diode is turned off, the radio frequency signal passes through the input port microstrip line, the first microstrip line, the second microstrip line, the sixth microstrip line, the eighth microstrip line, the ninth microstrip line, the tenth microstrip line, and the eleventh microstrip line, generating a dual-port output signal. At this time, the feed network is equivalent to a T-type equal-division phase-shifting power divider, and the antenna is in right-hand circular polarization mode.

[0021] When the second, third, and fourth PIN diodes are turned on and the first PIN diode is turned off, the radio frequency signal generates a dual-port output signal through the input port microstrip line, the first microstrip line, the third microstrip line, the seventh microstrip line, the eighth microstrip line, the ninth microstrip line, the tenth microstrip line, and the eleventh microstrip line. At this time, the feed network is equivalent to a T-type equal-division phase-shifting power divider, and the antenna is in left-hand circular polarization mode.

[0022] Furthermore, a first feed post via is provided in the second, third, and fourth dielectric substrates for placing the first feed post; a second feed post via is provided in the third and fourth dielectric substrates for placing the second feed post. The inner walls of both the first and second feed post vias are plated with metal.

[0023] Furthermore, two circular gaps are provided in the metal ground. There is no printed metal in the circular gaps. A first feed post via is placed in the circular gap, and a second feed post via is placed in the circular gap to prevent the first and second feed posts from being directly connected to the metal ground, which would cause a short circuit.

[0024] The beneficial effects of this invention are as follows: Addressing the challenges of existing polarization-reconfigurable antennas in simultaneously achieving impedance bandwidth and low profile, as well as the impact of DC bias on antenna performance during polarization switching, this invention proposes a low-profile, broadband, four-polarization reconfigurable metasurface antenna. The antenna consists of a metasurface dual-linear polarization antenna and a reconfigurable feed network. Based on characteristic mode analysis, this invention designs a dual-polarization metasurface antenna structure that can effectively excite two sets of degenerate linear polarization radiation modes within the operating frequency band, achieving broadband performance. The reconfigurable feed network controls the transmission paths of its two output signals through the switching of PIN diodes, generating two single-port output signals and two dual-port output signals with different transmission paths. These signals are fed into an orthogonally placed L-shaped probe structure, which couples the feed to the antenna's metasurface radiating patch, thereby controlling the excitation state of the two orthogonal linear polarization modes of the dual-polarization antenna, ultimately achieving the switching of four different polarization modes. The feeding network designed in this invention does not directly contact the antenna's radiating patch, but rather uses a coupled feeding method. This reduces the impact of the DC bias circuit on the antenna's performance during polarization switching, and the separate design of the antenna and reconfigurable network increases design freedom. Therefore, the metasurface antenna proposed in this invention has the advantages of low profile and compact size, while simultaneously enabling switching between four polarization modes, all of which exhibit broadband performance. Furthermore, it demonstrates low cross-polarization levels when implementing linear polarization and excellent radiation characteristics when implementing circular polarization.

[0025] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0027] Figure 1 This is a schematic diagram of the low-profile broadband four-polarized reconfigurable metasurface antenna described in this invention.

[0028] Figure 2 The evolution of the metasurface structure for a low-profile broadband four-polarized reconfigurable metasurface antenna;

[0029] Figure 3 The main parameters for the characteristic mode analysis of metasurface antenna 1 are as follows: Figure 3 (a) is the pattern importance curve. Figure 3 (b) is the characteristic angle. Figure 3(c) represents the mode currents for Mode 1 and Mode 2 at 5.12 GHz. Figure 3 (d) represents the mode currents for modes 3 and 4 at 6.95 GHz. Figure 3 (e) shows the pattern radiation patterns of Mode 1 and Mode 2 at 5.12 GHz. Figure 3 (f) shows the pattern radiation patterns of Mode 3 and Mode 4 at 6.95 GHz;

[0030] Figure 4 The main parameters for the characteristic mode analysis of metasurface antenna 2 are as follows: Figure 4 (a) is the pattern importance curve. Figure 4 (b) is the characteristic angle. Figure 4 (c) represents the mode currents for Mode 1 and Mode 2 at 4.96 GHz. Figure 4 (d) represents the mode currents for modes 3 and 4 at 6.12 GHz. Figure 4 (e) shows the pattern radiation patterns of Mode 1 and Mode 2 at 4.96 GHz. Figure 4 (f) shows the pattern radiation patterns of Mode 3 and Mode 4 at 6.12 GHz;

[0031] Figure 5 Comparison of S-parameters of antennas with metasurface 1 and metasurface 2 when the feed network is non-reconfigurable;

[0032] Figure 6 This is a schematic diagram of the reconfigurable feed network for the four-polarized reconfigurable metasurface antenna of the present invention;

[0033] Figure 7 The diagram shows the signal transmission paths of a reconfigurable feeder network in four states: (a) State 1; (b) State 2; (c) State 3; (d) State 4.

[0034] Figure 8 This is a dimensioned diagram of a specific embodiment of the reconfigurable metasurface antenna of the present invention;

[0035] Figure 9 The S-parameters and gain curves of the linear polarization mode along the x-axis of the reconfigurable metasurface antenna of this invention are shown.

[0036] Figure 10 This is the radiation pattern of the linear polarization mode along the x-axis of the reconfigurable metasurface antenna of the present invention. Figure 10 (a) is the xoz plane (4.89GHz), Figure 10 (b) is the yoz plane (4.89GHz). Figure 10 (c) represents the xoz plane (6.15GHz). Figure 10 (d) represents the yoz plane (6.15GHz);

[0037] Figure 11The S-parameters and gain curves of the y-axis linear polarization mode of the reconfigurable metasurface antenna of this invention are shown.

[0038] Figure 12 This is the radiation pattern of the y-axis linear polarization mode of the reconfigurable metasurface antenna of the present invention. Figure 12 (a) represents the xoz plane (4.75GHz). Figure 12 (b) represents the yoz plane (4.75 GHz). Figure 12 (c) represents the xoz plane (5.81 GHz). Figure 12 (d) represents the yoz plane (5.81 GHz);

[0039] Figure 13 The S-parameter curves, gain curves, and axial ratio curves of the right-hand circularly polarized mode of the reconfigurable metasurface antenna of this invention are shown below. Figure 13 (a) shows the S-parameter curve and gain curve. Figure 13 (b) is the axial ratio curve;

[0040] Figure 14 The radiation pattern of the right-hand circularly polarized mode of the reconfigurable metasurface antenna. Figure 14 (a) is the xoz plane (4.70GHz), Figure 14 (b) represents the yoz plane (4.70 GHz). Figure 14 (c) represents the xoz plane (5.20GHz). Figure 14 (d) represents the yoz plane (5.20 GHz). Figure 14 (e) represents the xoz plane (5.70GHz). Figure 14 (f) represents the yoz plane (5.70 GHz);

[0041] Figure 15 The S-parameter curves, gain curves, and axial ratio curves of the left-hand circularly polarized mode of the reconfigurable metasurface antenna of this invention are shown below. Figure 15 (a) shows the S-parameter curve and gain curve. Figure 15 (b) is the axial ratio curve;

[0042] Figure 16 The radiation pattern of the left-hand circularly polarized mode of the reconfigurable metasurface antenna. Figure 16 (a) is the xoz plane (4.70GHz), Figure 16 (b) represents the yoz plane (4.70 GHz). Figure 16 (c) represents the xoz plane (5.20GHz). Figure 16 (d) represents the yoz plane (5.20 GHz). Figure 16 (e) represents the xoz plane (5.70GHz). Figure 16 (f) represents the yoz plane (5.70 GHz).

[0043] Reference numerals: 1-First feed post; 2-Second feed post; 3-First dielectric substrate; 4-Second dielectric substrate; 5-Third dielectric substrate; 6-Fourth dielectric substrate; 7-Rectangular patch one; 8-Rectangular patch two; 9-First patch; 10-Second patch; 11-Ground; 12-First feed post via; 13-Second feed post via; 14-Reconfigurable feed network; 15-First microstrip line; 16-Second microstrip line; 17-Third microstrip line; 18-Fourth microstrip line ; 19-Fifth microstrip line; 20-Sixth microstrip line; 21-Seventh microstrip line; 22-Eighth microstrip line; 23-Ninth microstrip line; 24-Tenth microstrip line; 25-Eleventh microstrip line; 26-First PIN diode; 27-Second PIN diode; 28-Third PIN diode; 29-Fourth PIN diode; 30-DC blocking capacitor; 31-RF choke; 32-DC bias pin; 33-Input port microstrip line; 34-Gap 1; 35-Gap 2. Detailed Implementation

[0044] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0045] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0046] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0047] This invention addresses the challenges of balancing impedance bandwidth and low profile in existing polarization-reconfigurable antennas, as well as the impact of DC bias on antenna performance during polarization switching. It proposes a low-profile, broadband, four-polarization-reconfigurable metasurface antenna. The antenna consists of a metasurface dual-linear polarization antenna and a reconfigurable feed network. Based on characteristic mode analysis, this invention designs the metasurface dual-polarization antenna structure, effectively exciting two degenerate linear polarization radiation modes within the operating frequency band, achieving broadband performance. The reconfigurable feed network controls the transmission paths of its two output signals through the switching of PIN diodes, generating two single-port output signals and two dual-port output signals with different transmission paths. These signals are fed into an orthogonally placed L-shaped probe structure, which couples the feed to the antenna's metasurface radiating patch, thereby controlling the excitation state of the two orthogonal linear polarization modes of the dual-polarization antenna, ultimately achieving the switching of four different polarization modes.

[0048] The feeding network designed in this invention does not directly contact the antenna's radiating patch, but rather uses a coupled feeding method. This reduces the impact of the DC bias circuit on the antenna's performance during polarization switching, and the separate design of the antenna and reconfigurable network increases design freedom. Therefore, the metasurface antenna proposed in this invention has the advantages of low profile and compact size, can achieve switching between four polarization modes, and all four polarization modes have broadband performance. Furthermore, it exhibits low cross-polarization levels when implementing linear polarization and good radiation characteristics when implementing circular polarization.

[0049] like Figure 1 As shown, a low-profile broadband quad-polarized reconfigurable metasurface antenna provided in an embodiment of the present invention has a structure comprising a first dielectric substrate (3), a second dielectric substrate (4), a third dielectric substrate (5), a fourth dielectric substrate (6) stacked in sequence, and a first feed post (1) and a second feed post (2).

[0050] Five rectangular patches (7) and four rectangular patches (8) with etched H-shaped slots are disposed on the upper surface of the first dielectric substrate (3), forming a 3×3 symmetrically arranged metasurface patch unit. The four rectangular patches (8) with etched H-shaped slots are symmetrically distributed in the four directions of east, south, west and north of the center of the first dielectric substrate (3).

[0051] The upper surface of the second dielectric substrate (4) is provided with a first patch (9), the upper surface of the third dielectric substrate (5) is provided with a second patch (10), the upper surface of the fourth dielectric substrate (6) is provided with a metal ground (11), and the lower surface is provided with a reconfigurable power supply network (14). The first patch (9) and the second patch (10) are arranged orthogonally in space.

[0052] The first feed post (1) passes through the fourth dielectric substrate (6), the metal ground (11), the third dielectric substrate (5), and the second dielectric substrate (4), and is connected to the first patch (9) and the reconfigurable feed network (14), respectively. The second feed post (2) passes through the fourth dielectric substrate (6), the metal ground (11), and the third dielectric substrate (5), and is connected to the second patch (10) and the reconfigurable feed network (14), respectively. The first feed post (1) and the first patch (9) constitute a first L-shaped probe, and the second feed post (2) and the second patch (10) constitute a second L-shaped probe.

[0053] A first feed post via (12) is provided in the second dielectric substrate (4), the third dielectric substrate (5), and the fourth dielectric substrate (6) for placing the first feed post (1); a second feed post via (13) is provided in the third dielectric substrate (5) and the fourth dielectric substrate (6) for placing the second feed post (2). The inner walls of the first feed post via (12) and the second feed post via (13) are plated with metal.

[0054] A circular gap one (34) and a circular gap two (35) are provided in the metal ground (11). There is no printed metal in the circular gap. A first feed post via (12) is placed in the circular gap (34), and a second feed post via (13) is placed in the circular gap (35) to avoid the first feed post (1) and the second feed post (2) being directly connected to the metal ground (11) and causing a short circuit.

[0055] The reconfigurable power supply network (14) includes an input port microstrip line (33), a first microstrip line (15), a second microstrip line (16), a third microstrip line (17), a fourth microstrip line (18), a fifth microstrip line (19), a sixth microstrip line (20), a seventh microstrip line (21), an eighth microstrip line (22), a ninth microstrip line (23), a tenth microstrip line (24), and an eleventh microstrip line (25), three capacitors (30), three RF chokes (31), three DC bias pins (32), and four PIN diodes: a first PIN diode (26), a second PIN diode (27), a third PIN diode (28), and a fourth PIN diode (29).

[0056] The input port microstrip line (33) is connected to the first microstrip line (15) via a capacitor (30). The first microstrip line (15) is connected to the second microstrip line (16) via a first PIN diode (26), and to the third microstrip line (17) via a second PIN diode (27). The second microstrip line (16) is simultaneously connected to the fourth microstrip line (18) and the sixth microstrip line (20). The third microstrip line (17) is simultaneously connected to the fifth microstrip line (19) and the seventh microstrip line (21). The fourth microstrip line (18) is connected to the fifth microstrip line (19) via a third PIN diode (28). The eighth microstrip line (22) is connected to the ninth microstrip line (23) via a fourth PIN diode (29).

[0057] The sixth microstrip line (20) is connected to the eighth microstrip line (22), and the eighth microstrip line (22) is connected to the tenth microstrip line (24) through a capacitor (30). The other end of the tenth microstrip line (24) serves as an output terminal of the reconfigurable feed network (14) and is connected to the first feed post (1). The seventh microstrip line (21) is connected to the ninth microstrip line (23), and the ninth microstrip line (23) is connected to the eleventh microstrip line (25) through a capacitor (30). The other end of the eleventh microstrip line (25) serves as another output terminal of the reconfigurable feed network (14) and is connected to the second feed post (2). The function of the capacitor (30) is to isolate DC signals and prevent DC signals from interfering with RF signals.

[0058] The lengths of the fourth microstrip line (18), the fifth microstrip line (19), the eighth microstrip line (22), the ninth microstrip line (23), the tenth microstrip line (24), and the eleventh microstrip line (25) are all one-eighth of the wavelength corresponding to the antenna's operating center frequency. The lengths of the second microstrip line (16), the third microstrip line (17), the sixth microstrip line (20), and the seventh microstrip line (21) are all one-quarter of the wavelength corresponding to the antenna's operating center frequency.

[0059] Specifically, the characteristic impedance of the input port microstrip line (33) is 50Ω; the characteristic impedance of the first microstrip line (15) is 50Ω with a phase shift of 90°; the characteristic impedance of the second microstrip line (16) is 50Ω with a phase shift of 90°; the characteristic impedance of the third microstrip line (17) is 50Ω with a phase shift of 90°; the characteristic impedance of the fourth microstrip line (18) is 50Ω with a phase shift of 45°; the characteristic impedance of the fifth microstrip line (19) is 50Ω with a phase shift of 45°; and the characteristic impedance of the sixth microstrip line (10) is 50Ω with a phase shift of 45°. The characteristic impedance of the first microstrip line (20) is 35.36Ω and the phase shift is 90°; the characteristic impedance of the seventh microstrip line (21) is 35.36Ω and the phase shift is 90°; the characteristic impedance of the eighth microstrip line (22) is 50Ω and the phase shift is 45°; the characteristic impedance of the ninth microstrip line (23) is 50Ω and the phase shift is 45°; the characteristic impedance of the tenth microstrip line (24) is 50Ω and the phase shift is 45°; and the characteristic impedance of the eleventh microstrip line (25) is 50Ω and the phase shift is 45°.

[0060] The middle sections of the first microstrip line (15), the sixth microstrip line (20), and the seventh microstrip line (21) are each connected to a DC bias pin (32) via an RF choke (31). The function of the RF choke (31) is to prevent radio frequency signals from entering the DC bias. A bias voltage is applied to the DC bias pin (32) respectively, and a forward voltage is provided to the positive terminal of the PIN diode through the RF choke (31).

[0061] By changing the bias voltage applied to the DC bias pin (32), the on / off state of the PIN diode can be controlled, so that the reconfigurable feed network (14) can realize single-port output signals with two different transmission paths and dual-port output signals with two different transmission paths, enabling the antenna to realize four polarization modes: x-axis linear polarization, y-axis linear polarization, left-hand circular polarization, and right-hand circular polarization.

[0062] The operating modes of the low-profile broadband four-polarization reconfigurable metasurface antenna proposed in this invention can be described using eigenmode analysis. Eigenmode analysis is used to identify multiple required operating modes within the antenna passband and guide improvements to the antenna structure to achieve the desired antenna performance. Eigenmode analysis is primarily based on mode importance (MS) and mode current distribution characteristics. Here, mode importance (MS) is the eigenvalue λ. n The function is defined as:

[0063] MS n =1 / (1+jλ) n MS n This represents the potential contribution of mode n to the total radiation when excitation is applied. The range of MS is [0,1]. The closer MS is to the maximum value of 1, the stronger the resonant state of the mode and the easier it is to excite. Conversely, the closer MS is to 0, the more the mode is in a storage state and the less difficult it is to excite.

[0064] This invention employs a method of separately designing a metasurface dual-polarized antenna and a reconfigurable feed network, then combining them to realize a low-profile broadband four-polarized reconfigurable metasurface antenna. The reconfigurable feed network is located on the lower surface of the fourth dielectric substrate layer of the antenna structure, and it is directly connected only to the feed posts of the two L-shaped probes. The output signal of the reconfigurable feed network is transmitted through the two feed posts to the rectangular patches of the two L-shaped probes, coupling and feeding the antenna's metasurface radiating patches. This method can reduce the impact of the DC bias circuit on the antenna performance during polarization mode switching.

[0065] To illustrate the design process of the metasurface dual-polarized antenna, the evolution of the metasurface structure of the metasurface dual-polarized antenna is as follows: Figure 2As shown, the metasurface of this invention, namely metasurface 2, is evolved from metasurface 1. In metasurface 1, the radiating patches are square patches of identical size. First, metasurface 1 is analyzed using characteristic modes. Figure 3 The main parameters for characteristic mode analysis of metasurface structure 1 and the rectangular patches in the two L-shaped probes include mode importance curves (MS), characteristic angle curves, and mode current distributions.

[0066] from Figure 3 (a) and Figure 3 (b) It is evident that the mode importance curves and characteristic angle curves of modes 1 and 2 are similar, as are those of modes 3 and 4. Therefore, modes 1 and 2 constitute one set of degenerate modes, while modes 3 and 4 constitute another set. The resonant points of modes 1 and 2 are at 5.12 GHz, while those of modes 3 and 4 are at 6.95 GHz, indicating a significant difference in the resonant points between these two sets of degenerate modes. Figure 3 (c) and Figure 3 (d) shows the mode current distribution of two sets of degenerate modes on the first and second patches of the metasurface structure 1 and the two L-shaped probes below it, at the corresponding resonant frequencies of 5.12 GHz and 6.95 GHz, respectively. The mode currents on the metasurface structure 1 are in one set of degenerate modes, such as mode 1 and mode 2 in the x-axis and y-axis directions, respectively. The mode currents of these two modes are orthogonal, and the current direction on the radiating patch of the metasurface 1 in each mode is consistent with the current direction of the rectangular patch of one of the L-shaped probes, which is consistent with the current distribution characteristics of a dual-polarized antenna. However, the resonant frequencies of these two sets of degenerate modes differ significantly, which will form two passbands with large frequency differences after feeding and excitation, making it difficult to combine them to achieve broadband.

[0067] Therefore, H-shaped slits are etched on a portion of the patch of metasurface 1 to form metasurface 2. The main parameters of the characteristic mode analysis of metasurface 2 are as follows: Figure 4 As shown. Among them, Figure 4 (a) shows the mode importance curves for metasurface structure 2 and the rectangular patches in the two L-shaped probes. Figure 4 (b) shows the characteristic angle curve of metasurface antenna 2. It can be seen that modes 1 and 2, and modes 3 and 4 each constitute a set of degenerate modes. The resonant points of modes 1 and 2 are both at 4.96 GHz, and the resonant points of modes 3 and 4 are both at 6.12 GHz. Therefore, the resonant points of the two sets of degenerate modes are closer than those of metasurface 1. Figure 4 (c) and Figure 4(d) shows the mode currents of the first and second patches of the two L-shaped probes below metasurface 2 at their respective resonant frequencies of 4.96 GHz and 6.12 GHz. The mode currents on the metasurface fall within a set of degenerate modes. The mode currents of the two modes are orthogonal, and the current direction on the metasurface in each mode is consistent with the current direction of the rectangular patch of one of the L-shaped probes, which conforms to the current distribution characteristics of a dual-polarized antenna. Therefore, the potential bandwidth of the antenna can be broadened by simultaneously exciting these two sets of degenerate modes.

[0068] To further observe the radiation characteristics of the metasurface dual-polarized antenna, Figure 3 (e) Figure 3 (f) and Figure 4 (e) Figure 4 (f) shows the mode radiation patterns of metasurface 1 and metasurface 2. It can be seen that, in addition to the aforementioned ability to broaden the potential bandwidth of the antenna, metasurface 2 also features a second group of degenerate modes, modes 3 and 4, whose radiation is more concentrated in the x or y direction compared to metasurface 1, making it more advantageous for designing dual-polarized antennas.

[0069] Figure 5 The S-parameters of antennas loaded with different metasurfaces are shown. The antenna loaded with metasurface 1 has two operating frequency bands within the target frequency band, with |S| at the lower frequency... 11 The frequency band with a voltage level less than -10dB is from 4.42GHz to 5.29GHz. 22 The frequency band with a value less than -10dB is from 4.33GHz to 5.32GHz, and the high-frequency |S 11 The frequency band with a voltage level less than -10dB is from 6.32GHz to 6.47GHz. 22 The frequency band with a band less than -10dB is 6.41GHz to 6.56GHz. It is evident that both low and high frequencies have their own passbands, preventing the formation of a single, wide passband.

[0070] The antenna with metasurface 2 loaded has a -10dB impedance bandwidth of |S 11 |: 4.84GHz~6.71GHz, |S 22 (4.75GHz~6.58GHz). Compared to the antenna loaded with metasurface 1, the two resonant points of the antenna loaded with metasurface 2 are closer together. Therefore, when both degenerate modes are excited simultaneously, a continuous passband is formed, significantly widening the operating bandwidth of the metasurface dual-polarized antenna. S-parameter analysis of these two dual-polarized antennas loaded with different metasurfaces confirms that eigenmode analysis provides excellent guidance for antenna structure design. eigenmode analysis optimized the metasurface structure, bringing the resonant frequencies of the two degenerate modes closer together, thus significantly widening the antenna's operating bandwidth when both modes are excited simultaneously.

[0071] After completing the dual-polarized antenna design, a reconfigurable network is added to the lower surface of the fourth layer substrate of the antenna, such as... Figure 6 As shown. The first feed post in the first L-shaped probe and the second feed post in the second L-shaped probe are respectively connected to the two output terminals P of the reconfigurable feed network. ox and P oy The signal is fed into the first patch of the first L-shaped probe and the second patch of the second L-shaped probe through the first and second feed pillars, respectively, to couple and feed the metasurface radiating patch. Four PIN diodes control the signal transmission path on the transmission lines in the feed network, thus enabling the reconfigurable feed network to control the excitation state of the two orthogonal linear polarization modes input to the dual-polarized antenna. This allows the antenna to switch between four polarization modes: x-axis linear polarization, y-axis linear polarization, left-hand circular polarization, and right-hand circular polarization, achieving a four-polarization reconfigurable function. The specific polarization modes under different diode states are shown in Table 1.

[0072] Table 1. Polarization modes of PIN diodes under different states.

[0073]

[0074] To clarify the working principle of the proposed reconfigurable feed network, different transmission paths corresponding to different PIN diode configurations are described. The reconfigurable feed network can be divided into four states: state 1, state 2, state 3, and state 4, as follows: Figure 7 As shown, the light-colored microstrip line represents the radio frequency signal transmission path, while the dark-colored microstrip line represents the radio frequency signal that does not pass through the microstrip line.

[0075] State 1 as Figure 7 As shown in (a), the first PIN diode S1 is turned on, while the second, third, and fourth PIN diodes S2, S3, and S4 are turned off. The RF signal flows from the reconfigurable feed network input port P. in Feed-in, transmitted through input port microstrip lines, microstrip transmission lines TL1, TL2, TL6 and TL10, to only one output port P. ox Then, power is supplied to the antenna through the first L-shaped probe. The output port P... oy Since there is no signal output, the signal fed into the metasurface radiating patch from the feed network is only in the x-axis direction, and not in the y-axis direction. Therefore, the antenna's polarization mode is a linear polarization mode in the x-axis direction.

[0076] State 2 as Figure 7 As shown in (b), PIN diode S2 is turned on at this time, while PIN diodes S1, S3, and S4 (first, third, and fourth PIN diodes) are turned off. Similar to state 1, the RF signal flows from the reconfigurable feed network input port P. inFeed in, through the input port microstrip line, microstrip transmission lines TL1, TL3, TL7 and TL11 to the output port P. oy Then, the second L-shaped probe feeds the metasurface radiating patch. The output port P... ox Since there is no signal output, the signal fed into the metasurface radiating patch from the feed network is only in the y-axis direction, and not in the x-axis direction. Therefore, the antenna's polarization mode is a linear polarization mode in the y-axis direction.

[0077] State 3 as Figure 7 As shown in (c), at this time, the first, third, and fourth PIN diodes S1, S3, and S4 are turned on, while the second PIN diode S2 is turned off. The RF signal flows from the reconfigurable feed network input port P. in The signal is fed in through the input port microstrip line, transmission lines TL1, TL2, and TL6. Since the second PIN diode S2 is disconnected, transmission line TL3 is equivalent to a quarter-wavelength transmission line with an open-circuit termination. Therefore, node A can be considered a short-circuit point. This causes the combined transmission lines TL4 and TL5, and transmission line TL7, to both become quarter-wavelength transmission lines with short-terminated terminations. In this case, nodes B and C of transmission lines TL4 and TL7 are equivalent to being in an open-circuit state, therefore no signal is transmitted on transmission lines TL3, TL4, TL5, and TL7.

[0078] The microstrip transmission line TL6 is connected to a bi-splitter T-shaped power divider, which splits the RF signal in two. One branch is TL10, and the other branch is TL8, TL9, and TL11. Half of the RF signal is transmitted to the output port P through transmission line TL10. ox The first L-shaped probe then feeds the metasurface radiation patch; the other half of the RF signal is transmitted to the output port P through transmission lines TL8, TL9, and TL11. oy Then, the metasurface radiating patch is fed through a second L-shaped probe. At this point, the entire feeding network is equivalent to a T-type equal-division phase-shifting power divider. Since transmission lines TL8 and TL9 are each one-eighth wavelength long, the two segments combined are one-quarter wavelength long, therefore the power transmitted to the output port P... ox and output port P oy The phase difference of the signals is 90°, so the phase difference of the signals fed into the orthogonally placed first L-shaped probe and second L-shaped probe is also 90°, so the polarization mode of the antenna is right-hand circular polarization mode.

[0079] State 4 Figure 7 As shown in (d), at this time, the second, third, and fourth PIN diodes S2, S3, and S4 are turned on, while the first PIN diode S1 is turned off. The signal flows from the input port P of the reconfigurable feed network. inThe signal is fed in through the input port microstrip line and transmission lines TL1, TL3, and TL7. Since the first PIN diode S1 is open, transmission line TL2 is equivalent to a quarter-wavelength transmission line with an open-circuit termination. Therefore, node B can be considered a short-circuit point. This causes the combined transmission lines TL4 and TL5, and transmission line TL6, to both become quarter-wavelength transmission lines with short-terminated terminations. In this case, nodes A and D of transmission lines TL5 and TL6 are equivalent to being in an open-circuit state, therefore no signal is transmitted on transmission lines TL2, TL4, TL5, and TL6.

[0080] At the end of transmission line TL7, a two-way T-shaped power divider is connected to split the RF signal in two, with one branch being TL11 and the other branch being TL9, TL8, and TL10. Half of the RF signal travels through transmission line TL11 to the output port P. oy The second L-shaped probe then powers the antenna; the other half of the RF signal is transmitted to the output port P via transmission lines TL9, TL8, and TL10. ox Then, the antenna is fed through the first L-shaped probe. At this point, the feeding network is equivalent to a T-shaped equal-division phase-shifting power divider. Since transmission lines TL8 and TL9 are each one-eighth of the wavelength, the two segments together are a quarter of the wavelength, therefore the power transmitted to the output port P... ox and output port P oy The signal phase difference is -90°, so the signal phase difference between the first L-shaped probe and the second L-shaped probe, which are orthogonally placed, is also -90°. Therefore, the polarization mode of the antenna is left-hand circular polarization.

[0081] Figure 9 This is a graph showing the gain and S-parameters of the x-axis linear polarization mode of the low-profile broadband four-polarized reconfigurable metasurface antenna of this invention. Figure 9 (a) It can be seen that the relative impedance bandwidth of the linear polarization mode along the x-axis (|S) 11 The value (<-10dB) is 24.04%, with a frequency range of 4.83GHz to 6.15GHz. (From...) Figure 9 (b) It can be seen that the average gain of the x-axis linear polarization mode within the operating bandwidth is 8.04 dBi and the peak gain is 8.21 dBi. Figure 10 The radiation patterns of the antenna in the xoz and yoz planes in the x-axis linear polarization mode at frequencies of 4.89 GHz and 6.15 GHz are shown, with cross-polarization below -20 dB.

[0082] Figure 11 This is a graph showing the gain and S-parameters of the y-axis linear polarization mode of the low-profile broadband four-polarized reconfigurable metasurface antenna of this invention. Figure 11 (a) It can be seen that the |S| of the linear polarization mode along the y-axis 11The frequency range with a bandwidth less than -10dB is 4.65GHz to ~5.81GHz, with a relative bandwidth of 22.18%. Figure 11 (b) It can be seen that the average gain of the linear polarization mode in the y-axis direction within the operating bandwidth is 7.87 dBi and the peak gain is 8.32 dBi. Figure 12 The radiation patterns in the xoz and yoz planes of the antenna in linear polarization mode along the y-axis are shown at frequencies of 4.75 GHz and 5.81 GHz. It can be seen that, regardless of whether the antenna is in linear polarization mode along the x-axis or y-axis, the cross-polarization is below -20 dB, and it exhibits low backscattering.

[0083] Figure 13 For the right-hand circular polarization mode of the present invention, |S 11 | Gain curve and axial ratio curve. As shown in the figures, the relative impedance bandwidth of the right-hand circularly polarized mode (|S) 11 The gain (<-10dB) is 28.41%, with a frequency range of 4.47GHz to 5.95GHz, and a peak gain of 8.16dBic within the operating bandwidth. The antenna's axial ratio is less than 3dB in the frequency range of 4.67GHz to 5.82GHz, with a relative axial ratio bandwidth of 21.92%.

[0084] Figure 14 This diagram shows the radiation patterns of the antenna in right-hand circular polarization mode in the xoz and yoz planes at frequencies of 4.70 GHz, 5.20 GHz, and 5.70 GHz. The radiation patterns show that the gain of right-hand circular polarization is at least 16.7 dB higher than that of left-hand circular polarization, confirming that the antenna exhibits good right-hand circular polarization performance within the operating frequency band in right-hand circular polarization mode.

[0085] Figure 15 |S for left-hand circularly polarized mode 11 | Gain curve and axial ratio curve. From the graphs, it can be seen that the |S of the left-hand circularly polarized mode 11 The frequency range with a gain less than -10dB is 4.68GHz to 6.07GHz, the relative impedance bandwidth is 25.86%, and the peak gain within the operating bandwidth is 8.12dBic. The relative axial ratio bandwidth (axial ratio <3dB) of the left-hand circular polarization mode is 29.69%, with a frequency range of 4.56GHz to 6.15GHz.

[0086] Figure 16This diagram shows the radiation patterns of the antenna in its left-hand circular polarization mode in the xoz and yoz planes at frequencies of 4.70 GHz, 5.20 GHz, and 5.70 GHz. The radiation patterns show that the gain of the left-hand circular polarization is at least 19.19 dB higher than that of the right-hand circular polarization, confirming that the left-hand circular polarization mode exhibits good left-hand circular polarization performance within the operating frequency band.

[0087] like Figure 8 The dimensions of the antenna described in this embodiment are shown. This embodiment's sample is a low-profile, broadband, four-polarized, reconfigurable metasurface antenna operating at frequencies of 4.47 GHz to 6.15 GHz. The antenna dimensions are 47.5 mm × 47.5 mm × 4.25 mm (i.e., 0.87λ0 × 0.87λ0 × 0.07λ0, where λ0 is the free-space wavelength corresponding to the center frequency). The antenna uses four F4B265 dielectric substrates with a dielectric constant of 2.65, a loss tangent of 0.0015, and thicknesses of 1.5 mm, 0.25 mm, 2 mm, and 0.5 mm, respectively. The PIN diode is an SMP1345-079LF, the capacitor is a 50 pF surface-mount capacitor, and the RF choke is a 1 nH inductor. The specific dimensions of this antenna are shown below. Figure 8 As shown in Table 2, the specific dimensions of the antenna are as follows:

[0088] Table 2. Parameters and dimensions of quad-polarized reconfigurable antennas (unit: mm)

[0089]

[0090] Characteristic mode simulations were performed using CST simulation software, and full-wave electromagnetic simulations were performed using HFSS simulation software. Figure 9 (a) It can be seen that the relative impedance bandwidth (|S) of the linear polarization mode along the x-axis of the polarization-reconfigurable antenna is... 11 The |<-10dB) value is 24.04%, with a frequency range of 4.83GHz to 6.15GHz. (By...) Figure 9 (b) shows that the average gain of the x-axis linear polarization mode of the polarization-reconfigurable antenna within the operating bandwidth is 8.04 dBi, and the peak gain is 8.21 dBi. From... Figure 10 It can be seen that in the x-axis linear polarization mode, the cross-polarization is less than -20dB.

[0091] like Figure 11 As shown in (a), the |S| of the linear polarization mode along the y-axis of the polarization-reconfigurable antenna 11 The frequency range with a bandwidth less than -10dB is 4.65GHz to 5.81GHz, with a relative bandwidth of 22.18%. Figure 11(b) It can be seen that the average gain of the linear polarization mode of the polarization reconfigurable antenna along the y-axis is 7.87 dBi and the peak gain is 8.32 dBi within the operating bandwidth. Figure 12 The radiation patterns in the xoz and yoz planes of the antenna in linear polarization mode along the y-axis are shown at frequencies of 4.75 GHz and 5.81 GHz. It can be seen that, regardless of whether the antenna is in linear polarization mode along the x-axis or y-axis, the cross-polarization is below -20 dB, and it exhibits low backscattering.

[0092] like Figure 13 As shown, the relative impedance bandwidth (|S) of the right-hand circularly polarized mode 11 The gain (<-10dB) is 28.41%, with a frequency range of 4.47GHz to 5.95GHz, and a peak gain of 8.16dBic within the operating bandwidth. The antenna's axial ratio is less than 3dB in the frequency range of 4.67GHz to 5.82GHz, with a relative axial ratio bandwidth of 21.92%.

[0093] like Figure 14 As shown in the radiation pattern, it can be observed that the gain of right-hand circular polarization in the electromagnetic wave propagation direction is at least 16.7 dB higher than that of left-hand circular polarization, confirming that the antenna has good right-hand circular polarization performance in the operating frequency band when in right-hand circular polarization mode.

[0094] Depend on Figure 15 It can be seen that the |S| of the left-hand circular polarization mode of the polarization-reconfigurable antenna 11 The frequency range with a gain less than -10dB is 4.68GHz to 6.07GHz, the relative impedance bandwidth is 25.86%, and the peak gain within the operating bandwidth is 8.12dBic. The relative axial ratio bandwidth (axial ratio <3dB) of the left-hand circular polarization mode is 29.69%, with a frequency range of 4.56GHz to 6.15GHz.

[0095] like Figure 16 As shown in the radiation pattern, it can be observed that the gain of left-hand circular polarization is at least 19.19 dB higher than that of right-hand circular polarization in the direction of electromagnetic wave propagation, confirming that the left-hand circular polarization mode has good left-hand circular polarization performance in the operating frequency band.

[0096] The metasurface antenna proposed in this invention has the advantages of low profile and compact size. It can switch between four polarization modes, and all four polarization modes have broadband performance. Furthermore, it has a low cross-polarization level when implementing linear polarization mode and good radiation characteristics when implementing circular polarization mode.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A low-profile broadband four-polarized reconfigurable metasurface antenna, characterized in that: Its structure includes a first dielectric substrate (3), a second dielectric substrate (4), a third dielectric substrate (5), and a fourth dielectric substrate (6) stacked sequentially; the upper surface of the first dielectric substrate (3) is provided with a plurality of symmetrically arranged metasurface patch units; the upper surface of the second dielectric substrate (4) is provided with a first patch (9), the upper surface of the third dielectric substrate (5) is provided with a second patch (10), the upper surface of the fourth dielectric substrate (6) is provided with a metal ground (11), and the lower surface is provided with a reconfigurable power supply network (14); the first patch (9) and the second patch (10) are orthogonally arranged in space; The antenna structure also includes a first feed post (1) and a second feed post (2); the first feed post (1) passes through the fourth dielectric substrate (6), the metal ground (11), the third dielectric substrate (5), and the second dielectric substrate (4), and is connected to the first patch (9) and the reconfigurable feed network (14) respectively; the second feed post (2) passes through the fourth dielectric substrate (6), the metal ground (11), and the third dielectric substrate (5), and is connected to the second patch (10) and the reconfigurable feed network (14) respectively; the first feed post (1) and the first patch (9) constitute a first L-shaped probe, and the second feed post (2) and the second patch (10) constitute a second L-shaped probe.

2. The low-profile broadband four-polarized reconfigurable metasurface antenna according to claim 1, characterized in that: The plurality of symmetrically arranged metasurface patch units are 3×3 symmetrically arranged metasurface patch units.

3. The low-profile broadband four-polarized reconfigurable metasurface antenna according to claim 2, characterized in that: The metasurface patch unit includes five rectangular patches (7) and four rectangular patches (8) with etched H-shaped slots; the four rectangular patches (8) with etched H-shaped slots are symmetrically distributed in the east, south, west and north directions relative to the center of the first dielectric substrate (3).

4. The low-profile broadband four-polarized reconfigurable metasurface antenna according to claim 1, characterized in that: The reconfigurable power supply network (14) includes an input port microstrip line (33), a first microstrip line (15), a second microstrip line (16), a third microstrip line (17), a fourth microstrip line (18), a fifth microstrip line (19), a sixth microstrip line (20), a seventh microstrip line (21), an eighth microstrip line (22), a ninth microstrip line (23), a tenth microstrip line (24), and an eleventh microstrip line (25), three capacitors (30), three RF chokes (31), three DC bias pins (32), and four PIN diodes: a first PIN diode (26), a second PIN diode (27), a third PIN diode (28), and a fourth PIN diode (29). The input port microstrip line (33) is connected to the first microstrip line (15) through a capacitor (30); the first microstrip line (15) is connected to the second microstrip line (16) through a first PIN diode (26), and to the third microstrip line (17) through a second PIN diode (27); the second microstrip line (16) is simultaneously connected to the fourth microstrip line (18) and the sixth microstrip line (20); the third microstrip line (17) is simultaneously connected to the fifth microstrip line (19) and the seventh microstrip line (21); the fourth microstrip line (18) is connected to the fifth microstrip line (19) through a third PIN diode (28); the eighth microstrip line (22) is connected to the ninth microstrip line (23) through a fourth PIN diode (29); the function of the capacitor (30) is to isolate DC signals and prevent DC signals from interfering with RF signals; The sixth microstrip line (20) is connected to the eighth microstrip line (22), and the eighth microstrip line (22) is connected to the tenth microstrip line (24) through a capacitor (30); the other end of the tenth microstrip line (24) serves as an output terminal of the reconfigurable feed network (14) and is connected to the first feed post (1); the seventh microstrip line (21) is connected to the ninth microstrip line (23), and the ninth microstrip line (23) serves as a capacitor (30) and is connected to the eleventh microstrip line (25); the other end of the eleventh microstrip line (25) serves as another output terminal of the reconfigurable feed network (14) and is connected to the second feed post (2). In the middle of the first microstrip line (15), the sixth microstrip line (20), and the seventh microstrip line (21), each is connected to a DC bias pin (32) through an RF choke (31); the function of the RF choke (31) is to prevent the radio frequency signal from entering the DC bias.

5. The low-profile broadband four-polarized reconfigurable metasurface antenna according to claim 4, characterized in that: A bias voltage is applied to the DC bias pin (32) respectively, and a positive voltage is provided to the positive terminal of the PIN diode through the RF choke (31). By changing the bias voltage applied to the DC bias pin (32), the on / off state of the PIN diode can be controlled, enabling the reconfigurable feed network (14) to achieve single-port output signals with two different transmission paths and dual-port output signals with two different transmission paths. This allows the reconfigurable metasurface antenna to switch between four polarization modes: x-axis linear polarization, y-axis linear polarization, left-hand circular polarization, and right-hand circular polarization.

6. The low-profile broadband four-polarized reconfigurable metasurface antenna according to claim 5, characterized in that: When the first PIN diode (26) is turned on and all other PIN diodes are blocked, the antenna is in x-axis linear polarization mode. When the second PIN diode (27) is turned on and the other PIN diodes are blocked, the antenna is in the y-axis linear polarization mode. When the first PIN diode (26) is turned on, the third PIN diode (28) is turned on, the fourth PIN diode (29) is turned on, and the second PIN diode (27) is blocked, the antenna is in right-hand circular polarization mode; When the second PIN diode (27) is turned on, the third PIN diode (28) is turned on, the fourth PIN diode (29) is turned on, and the first PIN diode (26) is blocked, the antenna is in left-hand circular polarization mode.

7. A low-profile broadband four-polarized reconfigurable metasurface antenna according to claim 1 or 4, characterized in that: A first feed post via (12) is provided in the second dielectric substrate (4), the third dielectric substrate (5) and the fourth dielectric substrate (6) for placing the first feed post (1); a second feed post via (13) is provided in the third dielectric substrate (5) and the fourth dielectric substrate (6) for placing the second feed post (2).

8. A low-profile broadband four-polarized reconfigurable metasurface antenna according to claim 7, characterized in that: The inner walls of the first feed post via (12) and the second feed post via (13) are both plated with metal.

9. A low-profile broadband four-polarized reconfigurable metasurface antenna according to claim 1, characterized in that: A circular gap one (34) and a circular gap two (35) are provided in the metal ground (11); there is no printed metal in the circular gap. A first feed post via (12) is placed in the circular gap (34), and a second feed post via (13) is placed in the circular gap (35) to avoid the first feed post (1) and the second feed post (2) being directly connected to the metal ground (11) and causing a short circuit.

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