Metasurface unit and its base station

Abstract

The present application provides a metasurface unit and a base station thereof, the metasurface unit including a resonator unit (100) configured to receive two paths of polarized incident signals or to emit two paths of polarized reflected signals, a power divider (200) connected to the resonator unit (100) and configured to combine the two paths of polarized incident signals input by the resonator unit (100) into a combined signal and / or demultiplex the input reflected signal into two paths of polarized reflected signals and output them to the resonator unit (100), and a phase shifter (300) connected to the power divider and configured to perform phase modulation on the combined signal input by the power divider (200) and output the phase-modulated reflected signal to the power divider (200).

Description

[Technical field]

[0001] This application is proposed based on and claims priority to a Chinese patent application having application number 202210275987.2 and filing date March 21, 2022, the entire contents of which are hereby incorporated by reference into this application.

[0002] The present application relates to the field of communications, but is not limited thereto, and in particular to a metasurface unit and its base station. [Background technology]

[0003] An artificial electromagnetic metasurface is a periodically arranged array of units that can change the propagation characteristics of electromagnetic waves and realize some special functions. For example, by designing a certain phase difference between the reflected wave and the incident wave of each unit, the array of units can achieve the electromagnetic beamforming function of a certain angle. Traditional artificial electromagnetic metasurfaces are static structures, whose electromagnetic properties cannot be changed and cannot meet today's communication demands. In recent years, the concept of a programmable metasurface has been proposed, which uses a radio frequency switch on the resonant unit of the metasurface unit to realize the adjustment of the resonant frequency of the signal through different states of the radio frequency switch, realizes the control of the reflected phase, and makes the metasurface exhibit dynamic electromagnetic properties, thereby realizing the programmable multi-beamforming function.

[0004] The parameter fluctuation of the radio frequency switch is likely to cause the resonance frequency offset of the resonator unit, which affects the phase modulation accuracy of the metasurface unit. To solve this problem, the combination of the resonator unit and the phase shifter is generally adopted, and the radio frequency switch is installed in the phase shifter to achieve the separation between the resonator unit and the radio frequency switch. However, it is necessary to install one phase shifter for each polarization signal, and the hardware cost is relatively high. Summary of the Invention [Problem to be solved by the invention]

[0005] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0006] An embodiment of the present application provides a metasurface unit and its base station. [Means for solving the problem]

[0007] According to a first aspect, an embodiment of the present application provides a metasurface unit, which includes a resonator unit configured to receive two paths of polarized incident signals or radiate two paths of polarized reflected signals, a power divider connected to the resonator unit and configured to combine the two paths of polarized incident signals input by the resonator unit as a combined signal and / or split the input reflected signal into two paths of polarized reflected signals and output them to the resonator unit, and a phase shifter connected to the power divider and configured to perform phase modulation on the combined signal input by the power divider and output the reflected signal obtained by phase modulation to the power divider.

[0008] According to a second aspect, an embodiment of the present application provides a base station, the base station including a metasurface unit according to the first aspect.

[0009] Additional features and advantages of the present application will be set forth in the specification which follows, and in part will be obvious from the specification, or will be learned by the practice of the present application. The objectives and other advantages of the present application will be realized and obtained by the structure particularly pointed out in the written description, claims and drawings. The drawings are intended to provide a further understanding of the technical solution of the present application, constitute a part of the specification, and are used to interpret the technical solution of the present application together with the examples of the present application, and are not intended to limit the technical solution of the present application. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a metasurface unit according to Example 1 of the present application. [Diagram 2] FIG. 1 is a front view of a power splitter according to a first embodiment of the present application. [Diagram 3] 1 is a diagram showing the internal structure of a phase shifter according to a first embodiment of the present application. [Figure 4] FIG. 11 is a diagram showing the internal structure of a phase shifter according to a second embodiment of the present invention. [Diagram 5] FIG. 11 is a diagram showing the internal structure of a phase shifter according to a third embodiment of the present application. [Figure 6] FIG. 13 is a schematic diagram of the 2-bit reflection amplitude at the infinitely periodic boundary of a metasurface unit of an embodiment of the present application. [Figure 7] Schematic diagram of 2-bit reflection phase at the infinitely periodic boundary of a metasurface unit of an embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be described in more detail below with reference to the drawings and examples. The embodiments described herein are only used to interpret the present application, and are not intended to limit the present application.

[0012] Although the schematic diagram of the device shows a division into functional modules, in some cases the division into modules in the device may be different, or the steps shown or described may be performed in a different order than in the flowchart. The terms "first", "second", etc. in the specification, claims, or above drawings are used to distinguish between similar objects, and are not necessarily intended to describe a specific order or sequence.

[0013] The present application provides a metasurface unit and its base station, the metasurface unit includes a resonator configured to receive two-path polarized incident signals or emit two-path polarized reflected signals, a power divider connected to the resonator configured to combine the two-path polarized incident signals input by the resonator into a combined signal and / or split the input reflected signal into two-path polarized reflected signals and output them to the resonator, and a phase shifter connected to the power divider configured to phase modulate the combined signal input by the power divider and output the phase-modulated reflected signal to the power divider. According to the technical solution of this embodiment, the power divider realizes the combination and splitting of two-path polarized signals, so that the two-path polarized signals share the same phase shifter, which can effectively reduce the number of phase shifters in the metasurface unit and reduce hardware costs.

[0014] In the following, examples of the present application are further described with reference to the drawings.

[0015] Referring to FIG. 1 , the present application provides a metasurface unit, the metasurface unit comprising: A resonator unit 100 configured to receive a dual-path polarized incident signal or to emit a dual-path polarized reflected signal; A power splitter 200 is connected to the resonance unit 100 and configured to combine two paths of polarized incident signals input by the resonance unit 100 into a combined signal, and / or to split an input reflected signal into two paths of polarized reflected signals and output them to the resonance unit 100; The phase shifter 300 is connected to the power divider 200 and configured to perform phase modulation on the combined signal input by the power divider 200 and output the reflected signal obtained by the phase modulation to the power divider 200.

[0016] In the operating frequency band of the metasurface unit, the resonant unit 100 can realize a dual polarization operating mode, that is, the resonant unit 100 receives electromagnetic wave signals incident from two polarizations in space through resonance, and then combines the two-path polarized incident signals into one-path combined signal by the power divider 200, inputs the combined signal into the phase shifter 300 for phase modulation, and then reflects the signal to the power divider 200, where the reflected signal is divided into two-path polarized reflected signals, which are radiated in the form of electromagnetic waves by the resonant unit 100 to form a reflected wave.

[0017] According to the structure of the metasurface unit of this embodiment, the phase shifter 300 and the resonator unit 100 are independent devices, and the device parameters of the phase shifter 300 do not affect the resonator unit 100's resonant frequency, effectively ensuring the phase modulation accuracy, and the metasurface unit can be applied to all frequency bands. In addition, the resonator unit 100 adopts a dual polarization design, and two paths of polarized signals with different polarizations are combined by the power divider 200 and then connected to the phase shifter 300. The two paths of polarized signals share one phase shifter 300 to perform phase modulation, and while supporting the dual polarization mode, the effect of reducing the phase shifter 300 in the metasurface unit by half is realized, and the hardware cost is effectively reduced.

[0018] Below, various embodiments of the metasurface unit are described by way of several examples.

[0019] Example 1: In this embodiment, referring to Fig. 1, the resonant unit 100, the power splitter 200 and the phase shifter 300 are all independent devices, the resonant unit 100 includes a first polarization port 101 and a second polarization port 102, the power splitter 200 includes a first power splitter port 205 and a second power splitter port 204, the first polarization port 101 is connected to the first power splitter port 205, and the second polarization port 102 is connected to the second power splitter port 204. The power splitter 200 further includes a third power splitter port 203, and the phase shifter 300 includes a phase shifter port 311, and the third power splitter port 203 is connected to the phase shifter port 311. The resonator unit 100 is configured to receive a first polarized incident signal and a second polarized incident signal, input the first polarized incident signal to the first power splitter port 205 via the first polarization port 101, and input the second polarized incident signal to the second power splitter port 204 via the second polarization port 102, where the polarization directions of the first polarized incident signal and the second polarized incident signal are orthogonal to each other. The resonator unit 100 is further configured to radiate a first polarized reflected signal and a second polarized reflected signal, where the polarization directions of the first polarized reflected signal and the second polarized reflected signal are orthogonal to each other, and the first polarized reflected signal is input by the power splitter 200 via the first power splitter port 205, and the second polarized reflected signal is input by the power splitter 200 via the second power splitter port 204. The power splitter 200 is configured to combine the first polarized incident signal and the second polarized incident signal as a combined signal, and input the combined signal to the phase shifter 300 via the third power splitter port 203, so that the phase shifter 300 performs phase modulation on the combined signal to obtain a reflected signal. The power splitter 200 is further configured to obtain the reflected signal input via the phase shifter port 311 by the phase shifter 300, and split the reflected signal into a first polarized reflected signal and a second polarized reflected signal.

[0020] The resonating unit 100 may be a microstrip antenna unit or a dipole antenna unit, or may be other radiating units with a resonating function, and this embodiment does not excessively limit the device selection of the resonating unit 100.

[0021] In order to realize the dual polarization operation model, the polarized input signal received by the resonator unit 100 and the polarized output signal emitted may be polarized signals whose polarization directions of the two paths are orthogonal to each other. For example, the first polarized input signal may be an electromagnetic wave signal whose polarization direction is 45 degrees in space, and the second polarized input signal may be an electromagnetic wave signal whose polarization direction is minus 45 degrees in space. The combined signal is obtained by combining the power splitter 200, and then input to the phase shifter 300 for phase modulation. The resulting reflected signal is divided into a first polarized reflected signal whose polarization direction is 45 degrees and a second polarized reflected signal whose polarization direction is minus 45 degrees in the power splitter 200, and then radiated in the form of an electromagnetic wave by the resonator unit 100 to form a reflected wave. The polarization directions described in the above example do not limit the technical solution of this embodiment, and it is sufficient to ensure that the polarization directions of the polarized signals of the two paths of input and output are orthogonal to each other.

[0022] The reflected signal of this embodiment may be a signal obtained after performing phase modulation on the first polarized incident signal, or may be a signal obtained after performing phase modulation on the second polarized incident signal. The metasurface unit of this embodiment uses the power splitter 200 to split the reflected signal, so that after phase modulation of the first polarized incident signal with a polarization direction of 45 degrees, a first polarized reflected signal with a polarization direction of 45 degrees and a second polarized reflected signal with a polarization direction of minus 45 degrees can be obtained, effectively increasing the type of signal polarization. Of course, the processing process for the second polarized incident signal with a polarization direction of minus 45 degrees is similar, and will not be further described here.

[0023] The power splitter 200 may be a Wilkinson power splitter, a 3 dB bridge, a T-junction, or an integrated component with a power splitting function, and this embodiment does not excessively limit the device selection of the power splitter 200.

[0024] The phase shifter 300 may be a device consisting of multiple segments of transmission lines and radio frequency switches, and each segment of the transmission lines is connected by a radio frequency switch to form a series connection or parallel connection relationship between the multiple segments of the transmission lines, and different phase shift effects are realized according to the combination of the states of the radio frequency switches. Of course, the phase shifter 300 may be an integrated component with a phase shift function, and the present embodiment does not excessively limit the structure of the phase shifter 300.

[0025] Also, referring to FIG. 2, the power splitter 200 further includes a power splitter transmission line 201 and an isolation resistor 202, and the power splitter transmission line 201 is connected to a first power splitter port 205, a second power splitter port 204 and a third power splitter port 203, respectively. The isolation resistor 202 is installed between a first segment line and a second segment line of the power splitter transmission line 201, where the first segment line is configured to connect the first power splitter port 205 and the second segment line is configured to connect the second power splitter port 204.

[0026] 2 is a Wilkinson power divider. When receiving electromagnetic waves, the resonator unit 100 inputs two polarized incident signals through the first power divider port 205 and the second power divider port 204, respectively, and realizes signal multiplexing by the power divider 200. Similarly, when transmitting electromagnetic waves, the phase shifter 300 inputs a reflected signal through the third power divider port 203, and the power divider 200 allocates the reflected signal to the two polarized waves of the resonator unit, thereby realizing the radiation of two-path polarized signals.

[0027] The power divider transmission line 201 may be a stripline structure as shown in Fig. 2, respectively connecting the first power divider port 205, the second power divider port 204 and the third power divider port 203, and installing an isolation resistor 202 between the first segment line connected to the first power divider port 205 and the second segment line connected to the second power divider port 204, thereby realizing the isolation of the two-path polarized signals. The isolation resistor 202 may be a surface-mount resistor, and the resistance value may be adjusted according to actual needs.

[0028] 3, the phase shifter 300 further includes a DC blocking capacitor 302, a radio frequency switch module, and an AC blocking inductor 308, which are connected in series, and the DC blocking capacitor 302 is connected to a phase shifter port 311. The phase shifter 300 includes a first phase shifter transmission line 301, a second phase shifter transmission line 304, a third phase shifter transmission line 305, and a fourth phase shifter transmission line 307. The radio frequency switch module includes a first radio frequency switch 310, a second radio frequency switch 309, and a third radio frequency switch 306. The DC blocking capacitor 302 and the first radio frequency switch 310 are connected via the first phase shifter transmission line 301. The first radio frequency switch 310 and the second radio frequency switch 309 are connected in series via the second phase shifter transmission line 304. The second radio frequency switch 309 and the third radio frequency switch 306 are connected in series via a third phase shifter transmission line 305. The third radio frequency switch 306 and the AC blocking inductor 308 are connected via a fourth phase shifter transmission line 307. A DC bias line 303 is connected to each of the first phase shifter transmission line 301, the second phase shifter transmission line 304, and the third phase shifter transmission line 305.

[0029] In this embodiment, the first phase shifter transmission line 301, the second phase shifter transmission line 304, the third phase shifter transmission line 305 and the fourth phase shifter transmission line 307 are connected in series through three radio frequency switches to form a complete transmission line. The above transmission lines may adopt microstrip line or stripline structure, which can be selected according to actual needs.

[0030] The DC blocking capacitor 302 can isolate the direct current and prevent the bias current from entering the power distributor 200. The AC blocking inductor 308 can isolate the radio frequency signal and prevent the radio frequency signal from entering the bias circuit 303. The DC blocking capacitor 302 and the AC blocking inductor 308 can adopt a patch device, or can be a distributed capacitor and a distributed inductor, and the type and parameters can be selected according to actual needs.

[0031] The three radio frequency switches in this embodiment may adopt PIN diodes, varactor diodes, triodes, field effect transistors, single-pole single-throw / single-pole multi-throw switches, etc., and this embodiment does not excessively limit the selection of the radio frequency switches.

[0032] In the phase shifter 300 of this embodiment, three radio frequency switches are connected through the first phase shifter transmission line 301, the second phase shifter transmission line 304 and the third phase shifter transmission line 305 to realize the series connection of the phase shifter transmission lines, so that four kinds of phases, that is, 2-bit phase states, can be realized according to the different states of the three radio frequency switches, the phase quantification precision can be effectively improved, and the scalability is excellent. For example, the combined signal is input through the phase shifter port 311, passes through the DC blocking capacitor 302 and then enters the radio frequency switch module, the combined signal passes through the radio frequency switch that is once opened, reaches an open circuit or short circuit terminal, and is reflected. The different combinations of the open states of the three radio frequency switches can realize four kinds of states, where when all three radio frequency switches are off, the combination state is "00" and the corresponding reflection phase is 0 degrees; when the first radio frequency switch 310 is turned on, the combination state is "01" and the corresponding reflection phase is minus 90 degrees; when the first radio frequency switch 310 and the second radio frequency switch 309 are turned on, the combination state is "10" and the corresponding reflection phase is minus 180 degrees; when the first radio frequency switch 310, the second radio frequency switch 309 and the third radio frequency switch 306 are turned on, the combination state is "11" and the corresponding reflection phase is minus 270 degrees. A schematic diagram of the reflection amplitude obtained by using the metasurface unit of this embodiment can be seen in FIG. 6, where the combination states corresponding to the four curves from top to bottom at the abscissa 2.5 GHz are "00", "01", "11" and "10". The schematic diagram of the reflection phase can be seen in Figure 7, where the combination states corresponding to the four curves from top to bottom at the abscissa 2.5 GHz are "00", "01", "10" and "11". As can be seen from Figures 6 and 7, the reflection phase and reflection amplitude are different in different combination states, which shows that the metasurface unit has strong scalability and relatively high phase quantification accuracy.

[0033] Example 2: The metasurface unit of this embodiment is similar to that of Example 1, with the main differences being as follows.

[0034] 4 , the phase shifter 300 includes a first phase shifter transmission line 301, a second phase shifter transmission line 304, a third phase shifter transmission line 305, a fourth phase shifter transmission line 307, and a fifth phase shifter transmission line 313. The radio frequency switch module includes a third radio frequency switch 306 and a group of radio frequency switches 312, which includes a first radio frequency switch 310 and a second radio frequency switch 309. The DC blocking capacitor 302 and the first radio frequency switch 310 are connected via a first phase shifter transmission line 301, the first radio frequency switch 310 and the second radio frequency switch 309 are connected in parallel via a second phase shifter transmission line 304 and a fifth phase shifter transmission line 313, the second radio frequency switch 309 and the third radio frequency switch 306 are connected in series via a third phase shifter transmission line 305, and the third radio frequency switch 306 and the AC blocking inductor 308 are connected via a fourth phase shifter transmission line 307.

[0035] In the radio frequency switch module of this embodiment, the second phase shifter transmission line 304 and the fifth phase shifter transmission line 313 form a parallel connection, and 2-bit phase response can also be realized by different states of the three radio frequency switches. The difference is that the installation direction of the second radio frequency switch 309 in this embodiment is different from that of the second radio frequency switch 309 in the first embodiment, and two DC blocking capacitors 302 and a bias circuit 303 are installed in the fifth phase shifter transmission line 313 accordingly. The difference between this embodiment and the first embodiment is that the connection method between the radio frequency switch and the transmission line is different, and other principles are almost the same, so no further description is given here.

[0036] Example 3: The metasurface unit of this embodiment is similar to that of Example 2, with the main differences being as follows.

[0037] Referring to FIG. 5, the radio frequency switch module includes at least two radio frequency switch groups 312 connected in series with each other.

[0038] In this embodiment, by adding one radio frequency switch group 312 based on the second embodiment, an 8-bit phase state is realized by five radio frequency switches in the phase shifter 300, and the accuracy of phase adjustment can be further improved. The principle that the switch states of the five radio frequency switches determine the reflection phase is similar to that of the second embodiment, and only one bit is added to describe the 8-bit state, for example, the combination state is "000" in the all-off state and "111" in the all-on state, which will not be described further here for the sake of simplicity.

[0039] Except for the above differences, the other parts of the metasurface unit of this embodiment can be referred to the description in Example 2, and for the sake of simplicity, they will not be described further here.

[0040] The present application further provides a base station including a metasurface unit according to any one of the above embodiments.

[0041] After any one of the metasurface units in the above embodiments is applied to a base station, a power distributor is installed in the metasurface unit, so that in dual polarization mode, the two-path polarized signals share one phase shifter, effectively reducing the number of phase shifters and reducing hardware costs.

[0042] The embodiment of the present application includes a resonator unit configured to receive two paths of polarized incident signals or emit two paths of polarized reflected signals, a power divider connected to the resonator unit and configured to combine the two paths of polarized incident signals input by the resonator unit as a combined signal and / or split the input reflected signal into two paths of polarized reflected signals and output them to the resonator unit, and a phase shifter connected to the power divider and configured to phase modulate the combined signal input by the power divider and output the phase-modulated reflected signal to the power divider. According to the technical solution of the embodiment, the power divider realizes the combination and splitting of two paths of polarized signals, so that the two paths of polarized signals share the same phase shifter, which can effectively reduce the number of phase shifters in the metasurface unit and reduce hardware costs.

[0043] Although some embodiments of the present application have been described above, the present application is not limited to the above-described embodiments, and a person skilled in the art may make various equivalent modifications or replacements without violating the scope of the present application, and all of these equivalent modifications or replacements are included in the scope limited by the claims of the present application.

Claims

1. a resonator unit configured to receive a dual-path polarized incident signal or to emit a dual-path polarized reflected signal; A power splitter is connected to the resonator unit and configured to combine the two paths of polarized incident signals input by the resonator unit into a combined signal, and / or to split an input reflected signal into two paths of polarized reflected signals and output them to the resonator unit; A metasurface unit characterized by including a phase shifter connected to the power divider and configured to perform phase modulation on the combined signal input by the power divider and output the reflected signal obtained by phase modulation to the power divider.

2. The resonating unit includes a first polarization port and a second polarization port, the power splitter includes a first power splitter port and a second power splitter port, the first polarization port is connected to the first power splitter port, and the second polarization port is connected to the second power splitter port; The resonator unit is configured to receive a first polarized input signal and a second polarized input signal, input the first polarized input signal to the first power splitter port via the first polarization port, and input the second polarized input signal to the second power splitter port via the second polarization port, where the polarization directions of the first polarized input signal and the second polarized input signal are orthogonal to each other; The metasurface unit of claim 1, wherein the resonant unit is further configured to radiate a first polarized reflected signal and a second polarized reflected signal, wherein the polarization directions of the first polarized reflected signal and the second polarized reflected signal are orthogonal to each other, and the first polarized reflected signal is input by the power splitter through the first power splitter port, and the second polarized reflected signal is input by the power splitter through the second power splitter port.

3. the power splitter further comprises a third power splitter port, the phase shifter comprises a phase shifter port, the third power splitter port is connected to the phase shifter port; the power divider is configured to combine the first polarized input signal and the second polarized input signal as the combined signal, input the combined signal to the phase shifter via the third power divider port, and cause the phase shifter to perform phase modulation on the combined signal to obtain the reflected signal; The metasurface unit of claim 2, wherein the power divider is further configured to obtain the reflected signal input by the phase shifter through the phase shifter port and split the reflected signal into the first polarization reflected signal and the second polarization reflected signal.

4. the power splitter further includes a power splitter transmission line and an isolation resistor, the power splitter transmission line being respectively connected to the first power splitter port, the second power splitter port, and the third power splitter port; 4. The metasurface unit of claim 3, wherein the isolation resistor is installed between a first segment line and a second segment line of the power divider transmission line, where the first segment line is configured to connect the first power divider port and the second segment line is configured to connect the second power divider port.

5. The metasurface unit of claim 3, wherein the phase shifter further includes a DC blocking capacitor, a radio frequency switch module, and an AC blocking inductor connected in series in order, the DC blocking capacitor being connected to the phase shifter port, and the radio frequency switch module being configured to perform phase modulation on the combined signal to obtain the reflected signal.

6. the phase shifter includes a first phase shifter transmission line, a second phase shifter transmission line, a third phase shifter transmission line, and a fourth phase shifter transmission line; and the radio frequency switch module includes a first radio frequency switch, a second radio frequency switch, and a third radio frequency switch; 6. The metasurface unit of claim 5, wherein the DC blocking capacitor and the first radio frequency switch are connected via the first phase shifter transmission line, the first radio frequency switch and the second radio frequency switch are connected in series via the second phase shifter transmission line, the second radio frequency switch and the third radio frequency switch are connected in series via the third phase shifter transmission line, and the third radio frequency switch and the AC blocking inductor are connected via the fourth phase shifter transmission line.

7. The metasurface unit of claim 6, wherein a DC bias line is connected to the first phase shifter transmission line, the second phase shifter transmission line, and the third phase shifter transmission line, respectively.

8. the phase shifter includes a first phase shifter transmission line, a second phase shifter transmission line, a third phase shifter transmission line, a fourth phase shifter transmission line, and a fifth phase shifter transmission line; the radio frequency switch module includes a third radio frequency switch and a group of radio frequency switches, the group of radio frequency switches includes a first radio frequency switch and a second radio frequency switch; 6. The metasurface unit of claim 5, wherein the DC blocking capacitor and the first radio frequency switch are connected via the first phase shifter transmission line, the first radio frequency switch and the second radio frequency switch are connected in parallel via the second phase shifter transmission line and the fifth phase shifter transmission line, the second radio frequency switch and the third radio frequency switch are connected in series via the third phase shifter transmission line, and the third radio frequency switch and the AC blocking inductor are connected via the fourth phase shifter transmission line.

9. The metasurface unit of claim 8 , wherein the second phase shifter transmission line and the fifth phase shifter transmission line are each connected to a DC bias line.

10. The metasurface unit of claim 8 , wherein the radio frequency switch module includes at least two groups of the radio frequency switches connected in series with each other.

11. A base station comprising a metasurface unit according to any one of claims 1 to 10.

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