A 2-bit dual-polarized smart metasurface antenna unit

Abstract

The application relates to a 2-bit dual-polarized intelligent super surface antenna unit suitable for the mobile communication field, which comprises a patch, a ground plate with a coupling slot, two microstrip lines with PIN diode switches and a reflecting plate; an H-shaped slot and an I-shaped slot are engraved on the ground plate; each slot is below a microstrip line, each microstrip line comprises a main line and two delay lines, the main line is connected with the delay lines through a PIN diode switch, and the length of the microstrip line is controlled by the PIN diode switch to provide phase changes of 0 DEG, 90 DEG, 180 DEG and 270 DEG; the application realizes the 2-bit dual-polarized characteristics by using four PIN diode switches, reduces the design difficulty of the control circuit and the antenna cost, and improves the pointing accuracy and the gain of the antenna beam.

Description

Technical Field

[0001] This invention belongs to the field of antenna design technology in wireless communication technology, and specifically relates to a 2-bit dual-polarized intelligent metasurface antenna unit. Background Technology

[0002] A metasurface is an ultrathin artificial planar structure composed of structurally and functionally similar units arranged periodically in a two-dimensional plane. By rationally designing the arrangement of these units, parameters such as the phase, amplitude, and frequency of electromagnetic waves can be controlled. Introducing adjustable components into the units of the metasurface creates a smart metasurface. Traditional smart metasurfaces typically use multiple PIN diodes to switch unit states to achieve 2-bit quantization or even higher bit counts. This significantly increases the design complexity of the units. Furthermore, the use of numerous PIN diodes increases unit losses, especially under the requirement of dual-polarization independent operation, where complex control circuitry and high unit losses are unacceptable. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a 2-bit dual-polarized intelligent metasurface antenna unit, in order to reduce the design difficulty of the control circuit and the manufacturing cost of the antenna while achieving low unit loss, and improving the pointing accuracy and gain of the antenna beam.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A 2-bit dual-polarized smart metasurface antenna element comprises, from top to bottom, a patch, a ground plane, a microstrip line, and a reflector. The ground plane is etched with a coupling groove. The microstrip line consists of a main line, two PIN diode switches, and two delay lines of unequal length. The main line is located directly below the coupling groove, and its projection crosses the coupling groove. Each end of the main line is connected to a delay line via a PIN diode switch. The two PIN diode switches control the connection state between the main line and each delay line, thereby controlling the length of the microstrip line to provide phase changes of 0°, 90°, 180°, and 270°. There are two microstrip lines, providing phase shifts for two orthogonal polarization directions, thus achieving 2-bit dual-polarization characteristics.

[0006] In one embodiment, the patch is printed on the upper surface of dielectric substrate one, the floor is printed on the upper surface of dielectric substrate two, the microstrip line is printed on the lower surface of dielectric substrate two, an air layer is formed between dielectric substrate one and the floor, and an air layer is formed between the microstrip line and the reflector.

[0007] In one embodiment, each end of the main line of the microstrip line is connected to a delay line via a PIN diode switch; there are two coupling slots, with the main line of each microstrip line located directly below a coupling slot and its projection spanning the corresponding coupling slot.

[0008] In one embodiment, the resonant frequencies of both coupling slots are higher than the operating frequency band of the antenna.

[0009] In one embodiment, the coupling groove is composed of mutually isolated "H"-shaped coupling grooves and "I"-shaped coupling grooves. The "H"-shaped coupling groove is composed of a first groove, a second groove, and a third groove, wherein the first groove is parallel to the third groove, the second groove is perpendicularly connected between the first groove and the third groove, and the "I"-shaped coupling groove is parallel to the first groove and symmetrical about the second groove. The lengths of the first groove and the third groove are both less than the length of the "I"-shaped coupling groove.

[0010] In one embodiment, the patch is rectangular in shape, and a first microstrip line is disposed directly below the "H"-shaped coupling slot. The first microstrip line includes a first main line. A second microstrip line is disposed directly below the "I"-shaped coupling slot. The second microstrip line includes a second main line. The projection of the first main line crosses the second slot perpendicularly, and the projection of the second main line crosses the "I"-shaped coupling slot perpendicularly. Each delay line is parallel to the "I"-shaped coupling slot.

[0011] In one embodiment, the first and last ends of the second main line are bent at 90° and connected to the corresponding delay lines via corresponding PIN diode switches, and the delay lines connected to the first and last ends are located on both sides of the second main line.

[0012] In one embodiment, the projection of the main line crosses the coupling slot only once, and the projection of the delay line does not overlap with the coupling slot.

[0013] In one embodiment, the anode of the PIN diode switch is connected to the main line, and the cathode is connected to the delay line; when the PIN diode switch is closed, the main line and the delay line connected to the PIN diode switch are connected; when the PIN diode switch is open, the main line and the delay line connected to the PIN diode switch are disconnected.

[0014] In one embodiment, the patch receives electromagnetic wave energy in free space. This electromagnetic wave energy is coupled to the main line of the microstrip line through a coupling groove etched on the floor, and reflected back to the main line at the end of the microstrip line. It is then coupled to the patch through the coupling groove, thereby exciting the patch to radiate into free space.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1) 2-bit quantization can provide lower quantization error and higher pointing accuracy.

[0017] 2) The use of fewer PIN diodes reduces the return loss of the unit and simplifies the design of the control circuit.

[0018] 3) The unit structure is simple, and microstrip lines are used as phase shifters, which reduces the production cost of the antenna. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural exploded view of a preferred embodiment of the present invention.

[0020] Figure 2 This is a front view of the antenna unit in a specific implementation.

[0021] Figure 3 This is a top view of the top patch of the antenna unit in a specific implementation.

[0022] Figure 4 This is a top view of the intermediate floor of the antenna unit in a specific embodiment.

[0023] Figure 5 This is a bottom view of the intermediate layer microstrip line of the antenna element in a specific embodiment.

[0024] Figure 6 The image shows the S-parameter curves of the vertical polarization of the antenna element in a specific implementation.

[0025] Figure 7 The image shows the S-parameter curves of the horizontal polarization of the antenna element in a specific implementation.

[0026] Figure 8 The image shows the phase shift curve of the vertical polarization of the antenna element in a specific implementation.

[0027] Figure 9 The image shows the phase shift curve of the horizontal polarization of the antenna element in a specific implementation. Detailed Implementation

[0028] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0029] As mentioned earlier, to achieve 2-bit quantization, existing smart metasurfaces require the deployment of a large number of PIN diodes, which is not only difficult to design but also results in high losses. Especially when applied to 5G base stations, this solution is no longer suitable for the requirements of low power consumption and dual polarization.

[0030] Therefore, this invention provides a smart metasurface antenna element, which is particularly suitable for the field of mobile communications, such as... Figure 1 and Figure 2As shown, from top to bottom, the structure includes a patch 1, a ground plane 3, a microstrip line 7, and a reflector 12. Coupling grooves are etched on the ground plane 3. The microstrip line 7 consists of a main line, two PIN diode switches, and two delay lines of unequal lengths. Each microstrip line 7 is a 2-bit phase shifter. The main line is located directly below the coupling groove, and its projection crosses the corresponding coupling groove. Each end of the main line is connected to one of the two delay lines via a PIN diode switch. The connection state between the main line and its two delay lines can be controlled by the PIN diode switches, thereby controlling the length of the microstrip line 7 and providing phase changes of 0°, 90°, 180°, and 270°. The microstrip line 7 includes two independent microstrip lines 7-1 and 7-2, which correspond to the two orthogonal polarizations of the antenna. By connecting delay lines to both ends of the main microstrip line, the length of each microstrip line 7 is controlled by a PIN diode switch. Thus, 2-bit dual polarization can be achieved independently using only four PIN diode switches, which reduces the design difficulty of the control circuit and the cost of the antenna, and improves the pointing accuracy and gain of the antenna beam.

[0031] In this invention, the opening and closing of each PIN diode switch determines the opening and closing of the corresponding main line and the corresponding delay line. In this invention, the anode of the PIN diode switch is connected to the main line, and the cathode is connected to the delay line; when the PIN diode switch is closed, the main line and the delay line connected to that PIN diode switch are connected; when the PIN diode switch is open, the main line and the delay line connected to that PIN diode switch are disconnected. The patch 1 receives electromagnetic wave energy in free space. This electromagnetic wave energy is coupled to the main line of the microstrip line 7 through coupling grooves etched on the ground plane 3, and reflected back to the main line at the end of the microstrip line. It is then coupled back to the patch 1 through the coupling grooves, thereby exciting the patch 1 to radiate into free space.

[0032] In one embodiment of the present invention, the intelligent metasurface antenna unit further includes necessary dielectric substrates, specifically dielectric substrate 2 and dielectric substrate 6. A patch 1 is printed on the upper surface of dielectric substrate 2, and patch 1 can be rectangular, such as... Figure 3 As shown. Floor 3 is printed on the upper surface of substrate 6, as... Figure 4 As shown. Microstrip line 7 is printed on the lower surface of dielectric substrate 6, as... Figure 5 As shown. There is an air layer between dielectric substrate 2 and floor 3, and an air layer between microstrip line 7 and reflector 12.

[0033] This embodiment illustrates the specific spatial arrangement of the antenna element. The air layer between the dielectric substrate 2 and the ground plane 3 expands the operating bandwidth of the antenna element and reduces dielectric loss. The air layer between the microstrip line 7 and the reflector 12 provides space for soldering PIN diodes. The reflector 12 reflects energy leaking back and forth from the coupling slot and microstrip line back to the antenna element.

[0034] In one embodiment of the present invention, each microstrip line 7 has its main line connected to a delay line segment via a PIN diode switch at both ends, thus the two microstrip lines 7 comprise four PIN diode switches and four delay lines. Simultaneously, there are two coupling slots, with the main line of each microstrip line 7 located directly below one coupling slot, and its projection spanning the corresponding coupling slot. That is, each microstrip line 7 corresponds to one coupling slot.

[0035] In this embodiment, the relationship between the two microstrip lines 7 and the two coupling slots is given. By designing different parameters for the main line and the delay lines at both ends of each microstrip line 7, different phase shifts can be added to the signal flowing through the microstrip line under the control of the PIN diode. The length of the microstrip line is positively correlated with the physical time delay, and the linewidth determines the characteristic impedance of the microstrip line. The two coupling slots correspond to two orthogonal polarization components, and the microstrip line provides a phase shift for the polarization component corresponding to the coupling slot above it.

[0036] In one embodiment of the present invention, such as Figure 1 and Figure 4 As shown, the two coupling slots consist of an "H"-shaped coupling slot 4 and an "I"-shaped coupling slot 5, which are isolated from each other and not connected. The "H"-shaped coupling slot 4 consists of a first slot, a second slot, and a third slot, where the first and third slots are parallel, and the second slot is perpendicularly connected between the first and third slots. The "I"-shaped coupling slot 5 is parallel to the first slot and symmetrical about the second slot. The distance between the "I"-shaped coupling slot 5 and the third slot is less than the distance between the "I"-shaped coupling slot 5 and the first slot; that is, the "I"-shaped coupling slot 5 is closer to the third slot. More precisely, it should be located on the side of the third slot away from the second slot, meaning that the extension of the "I"-shaped coupling slot 5 does not intersect with the "H"-shaped coupling slot 4. The lengths of the first and third slots are both less than the length of the "I"-shaped coupling slot 5, while the lengths of the first and third slots are equal.

[0037] In this embodiment, a microstrip slot coupling method is used for patch 1 feeding. Compared with traditional probe feeding, the isolation between the antenna polarizations can be improved, and the antenna fabrication difficulty is reduced. Furthermore, slot coupling feeding provides more degrees of adjustment freedom and a wider bandwidth. The "H"-shaped coupling slot compresses the slot length by increasing the overall width, thus allowing two orthogonally polarized coupling slots to be placed simultaneously in a single antenna element, enabling independent dual-polarization operation.

[0038] In one embodiment of the present invention, such as Figure 1 and Figure 5As shown, there are two microstrip lines 7: a first microstrip line 7-1 and a second microstrip line 7-2. The first microstrip line 7-1 is composed of a first left-side delay line 10-1, a first PIN diode switch 9-1, a first main line 8-1, a second PIN diode switch 9-2, and a first right-side delay line 11-1 connected sequentially. The second microstrip line 7-2 is composed of a second left-side delay line 10-2, a third PIN diode switch 9-3, a second main line 8-2, a fourth PIN diode switch 9-4, and a second right-side delay line 11-2 connected sequentially. The first microstrip line 7-1 is positioned directly below the "H"-shaped coupling slot 4, and the second microstrip line 7-2 is positioned directly below the "I"-shaped coupling slot 5. The projection of the first main line 8-1 perpendicularly crosses the "H"-shaped coupling slot 4, more specifically, across its second slot. The projection of the second main line 8-2 perpendicularly crosses the "I"-shaped coupling slot 5. The first left-side delay line 10-1, the second left-side delay line 10-2, the first right-side delay line 11-1, and the second right-side delay line 11-2 are all parallel to the "I"-shaped coupling slot 5. That is, each delay line extends along the length of the main line.

[0039] In this embodiment, the width of microstrip line 7 determines its characteristic impedance, the lengths of the first main line 8-1 and the second main line 8-2 determine the reference point for the bipolarized additional phase, and the lengths of the first left delay line 10-1, the second left delay line 10-2, the first right delay line 11-1, and the second right delay line 11-2 determine the phase shift under different states controlled by the PIN diode switch. The length of microstrip line 7 has a non-linear positive correlation with the phase shift it provides, and this relationship is mainly determined by the coupling slot parameters corresponding to the microstrip line. For the "H"-shaped coupling slot 4 and the "I"-shaped coupling slot 5, which have different shapes and parameters, the lengths of each main line and delay line segment need to be designed according to the frequency response curve of the microstrip line below the coupling slot to obtain the ideal phase shift and operating bandwidth.

[0040] In one embodiment of the present invention, such as Figure 1 and Figure 5 As shown, the main body of the second main line 8-2 is perpendicular to the "I"-shaped coupling groove 5, with both ends bent at 90° to avoid crossing the coupling groove again. For example, the first end of the second main line 8-2 bends 90° to the right and is then connected to the second right-side delay line 11-2 via the fourth PIN diode switch 9-4; the last end of the second main line 8-2 bends 90° to the left and is then connected to the second left-side delay line 10-2 via the third PIN diode switch 9-3. In this case, the second left-side delay line 10-2 is located to the left of the second main line 8-2, while the second right-side delay line 11-2 is located to the right of the second main line 8-2. It is understood in the art that the first end of the second main line 8-2 can also be bent 90° to the left, and its last end can also be bent 90° to the right.

[0041] In this embodiment, the main body of the microstrip line is perpendicular to the coupling slot to ensure that the electric field direction in the coupling slot is consistent with that of the microstrip line, thereby achieving a better coupling effect.

[0042] In one embodiment of the present invention, the projection of the main line crosses the coupling slot only once, and the delay line is placed away from the coupling slot, that is, the projection of the delay line does not overlap with the coupling slot.

[0043] In this embodiment, based on the fundamental principle of microstrip line slot coupling feed, a microstrip line can only cross a coupling slot once. Therefore, the delay line of the microstrip line should avoid crossing the coupling slot again. Simultaneously, coupling between the microstrip line and the orthogonally polarized coupling slot of the antenna should be avoided. Thus, the routing of the delay line should avoid orthogonally polarized coupling slots as much as possible; that is, the delay line of the microstrip line should avoid both coupling slots simultaneously. For example, the delay lines 10-2 and 11-2 of microstrip line 7-2 are designed with 90° bends.

[0044] In one embodiment of the present invention, the operating frequency band is selected as 3.4-3.8 GHz, which belongs to the n78 band in the Sub-6 GHz frequency band of 5G mobile communication. For example, the characteristic impedance of the microstrip line 7 is 50 ohms.

[0045] In this embodiment, patch 1 is a rectangular patch unit with a length and width of approximately λ. g (Wavelength in the dielectric) / 2, operating in half-wavelength mode. The resonant frequencies of both coupling slots are higher than the antenna's operating frequency band. Their main function is to couple the energy between patch 1 and microstrip line 7 without introducing additional resonant points. Each microstrip line 7 consists of a main line, two PIN diode switches, and two delay lines. The lengths of the two delay lines in each microstrip line are different. The connection between the main line and the delay lines is controlled by the PIN diode switches, changing the total length of the microstrip line and thus providing different reflection phases. Dielectric substrate 2 is a low-loss F4B high-frequency board, and dielectric substrate 6 is a low-loss Rogers RO4003 substrate.

[0046] The technical solution of this invention is implemented as follows: Each microstrip line 7 is a 2-bit phase shifter, which includes a main line, two PIN diode switches, and two delay lines of unequal length. The two microstrip lines provide phase shifts for two orthogonal polarization directions to achieve dual-polarization operation of the antenna. Figure 5The diagram shows a bottom view of two microstrip lines. By changing the open and closed states of the PIN diode switches on each microstrip line, four different total lengths of microstrip lines can be generated. These four lengths correspond to unit states of 0°, 90°, 180°, and 270°, respectively. Taking the first microstrip line 7-1 as an example, the specific working principle is explained as follows: 1) When both the first PIN diode switch 9-1 and the second PIN diode switch 9-2 are open, the microstrip line length is the shortest, and the provided phase shift is minimal. This phase shift serves as a reference, corresponding to a 0° phase. 2) When the first PIN diode switch 9-1 is open and the second PIN diode switch 9-2 is closed, the first main line 8-1 is connected to the shorter first right-side delay line 11-1. At this time, the length of the first microstrip line 7-1 increases, providing a greater phase shift, corresponding to a 90° phase. 3) When the first PIN diode switch 9-1 is closed and the second PIN diode switch 9-2 is open, the first main line 8-1 is connected to the longer first left-side delay line 10-1. At this time, the length of the first microstrip line 7-1 is longer than in 2), corresponding to a 180° phase. 4) When both the first PIN diode switch 9-1 and the second PIN diode switch 9-2 are closed, the length of the first microstrip line 7-1 is at its longest, providing the largest phase, corresponding to a 270° phase. Table 1 shows the different combinations of PIN diode switches corresponding to the four unit states under two orthogonal polarization directions. Therefore, this phase shifter achieves 2-bit phase shift functionality using only two PIN diode switches.

[0047] Table 1 shows the different state combinations of the PIN diode switch corresponding to the four unit states.

[0048]

[0049] Where: 0 indicates the switch is open, and 1 indicates the switch is closed.

[0050] Figure 6 and Figure 7 The |S11| parameters of the element in the two orthogonal polarization directions are shown. Within the operating frequency band, the |S11| parameters of all four states are less than -0.3dB, indicating that the antenna element can effectively re-radiate the received energy into free space, and the loss caused by the element is acceptable in practical engineering applications.

[0051] Figure 8 and Figure 9 The phase shift curves of the unit in two orthogonal polarization directions show that the phase difference between adjacent states of the unit remains within the range of 90°±20° within the operating frequency band. This indicates that the antenna unit can provide low quantization error over a wide operating frequency band, thereby providing high pointing accuracy and antenna gain. A certain deviation in quantization phase is considered acceptable in practical engineering applications.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. All equivalent changes and modifications made within the scope of the claims of the present invention shall fall within the scope of the claims of the present invention.

Claims

1. A 2-bit dual-polarized smart metasurface antenna element, characterized in that, From top to bottom, it includes a patch (1), a ground plane (3), a microstrip line (7), and a reflector (12); the ground plane (3) is etched with a coupling groove; the microstrip line (7) consists of a main line, two PIN diode switches, and two delay lines of unequal length. The main line is located directly below the coupling groove and its projection crosses the coupling groove. The two ends of the main line are connected to a delay line through one of the PIN diode switches. The connection state between the main line and each delay line is controlled by the two PIN diode switches, thereby controlling the length of the microstrip line (7) to provide phase changes of 0°, 90°, 180°, and 270°; there are two microstrip lines (7), which provide phase shifts for two orthogonal polarization directions to achieve 2-bit dual polarization characteristics; Each microstrip line (7) has a delay line connected to both ends of its main line via a PIN diode switch; there are two coupling slots, with each microstrip line (7) located directly below a coupling slot and its projection spanning the corresponding coupling slot; the two coupling slots correspond to two orthogonal polarization components, and each microstrip line (7) provides a phase shift for the polarization component corresponding to the coupling slot above it; the two microstrip lines (7) correspond to the two orthogonal polarizations of the antenna. The coupling groove is composed of mutually isolated "H"-shaped coupling groove (4) and "I"-shaped coupling groove (5). The "H"-shaped coupling groove (4) is composed of a first groove, a second groove and a third groove, wherein the first groove is parallel to the third groove, and the second groove is perpendicularly connected between the first groove and the third groove. The "I"-shaped coupling groove (5) is parallel to the first groove and symmetrical about the second groove, and the lengths of the first groove and the third groove are both less than the length of the "I"-shaped coupling groove (5). The patch (1) is rectangular in shape. A first microstrip line (7-1) is disposed directly below the "H"-shaped coupling groove (4). The first microstrip line (7-1) includes a first main line (8-1). A second microstrip line (7-2) is disposed directly below the "I"-shaped coupling groove (5). The second microstrip line (7-2) includes a second main line (8-2). The projection of the first main line (8-1) crosses the second groove perpendicularly, and the projection of the second main line (8-2) crosses the "I"-shaped coupling groove (5) perpendicularly.

2. The 2-bit dual-polarized smart metasurface antenna unit according to claim 1, characterized in that, The patch (1) is printed on the upper surface of the first dielectric plate (2), the floor (3) is printed on the upper surface of the second dielectric plate (6), the microstrip line (7) is printed on the lower surface of the second dielectric plate (6), there is an air layer between the first dielectric plate (2) and the floor (3), and there is an air layer between the microstrip line (7) and the reflector (12).

3. The 2-bit dual-polarized smart metasurface antenna unit according to claim 1, characterized in that, The resonant frequencies of both coupling slots are higher than the operating frequency band of the antenna.

4. The 2-bit dual-polarized smart metasurface antenna unit according to claim 1, characterized in that, The first and last ends of the second main line (8-2) are bent at 90° and connected to the corresponding delay lines through corresponding PIN diode switches, and the delay lines connected to the first and last ends are located on both sides of the second main line (8-2).

5. The 2-bit dual-polarized smart metasurface antenna unit according to claim 1, characterized in that, The projection of the main line crosses the coupling slot only once, and the projection of the delay line does not overlap with the coupling slot.

6. The 2-bit dual-polarized smart metasurface antenna unit according to claim 1, characterized in that, When the PIN diode switch is closed, the main line and the delay line connected to the PIN diode switch are connected; when the PIN diode switch is open, the main line and the delay line connected to the PIN diode switch are disconnected.

7. The 2-bit dual-polarized smart metasurface antenna unit according to claim 1, characterized in that, The patch (1) receives electromagnetic wave energy in free space. The electromagnetic wave energy is coupled to the main line of the microstrip line (7) through the coupling groove etched on the floor (3), and reflected back to the main line at the end of the microstrip line. It is then coupled to the patch (1) through the coupling groove, thereby exciting the patch (1) to radiate into free space.

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