A frequency reconfigurable waveguide antenna based on bottom-side metasurface switching

Abstract

The application relates to a frequency reconfiguration waveguide antenna based on bottom end metasurface switching, which comprises an antenna, a waveguide cavity and a metasurface; the antenna is a rectangular waveguide antenna; the waveguide antenna has a fixed feed port, that is, a coaxial probe penetrating through the waveguide; the waveguide antenna radiation aperture is a rectangular aperture; the metasurface is a surface attached with a special metal structure. A slide rail is embedded outside the bottom end of the waveguide, and the metasurface with a phase modulation structure can be pulled out or pushed in; by pulling out or pushing in the metasurface, the antenna has two working states, that is, working state A and working state B, which correspond to two reconfiguration frequency bands of the antenna respectively. In the application, the waveguide antenna can realize rapid reconfiguration of the working frequency through switching of the bottom end metal surface, and the radiation performance remains stable.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of frequency reconfigurable antennas, in particular to a waveguide antenna which can be reconfigured across frequency bands. BACKGROUND

[0002] Antennas are an important component of the radio frequency front end of communication and radar systems. In recent years, the fields of digital circuitry, signal processing, computer chip manufacturing, software engineering, and the like have made rapid progress, and the mid and back ends of communication systems have basically achieved full-digital signal processing functions. However, due to certain technical limitations, the antenna module at the front end of the communication system still maintains its traditional analog working mode, which is very mismatched with the digital working mode of the mid and back ends, thus restricting the upgrading and updating of the entire communication system. In order to realize the high flexibility of modern communication systems endowed by digital reconfiguration, frequency reconfiguration of radio frequency antennas has become an urgent problem to be solved. Frequency reconfigurable antennas refer to antennas whose radiation characteristics do not change significantly and whose radiation performance remains stable when the operating frequency changes significantly. Compared with frequency tuning antennas, reconfigurable antennas can switch across frequency bands, have a large frequency adjustment range, and do not change the radiation pattern and radiation gain significantly. Current technical approaches to reconfigurable antennas mainly include mechanical reconfiguration, electronic reconfiguration, and material reconfiguration, which change the current and electric field distribution of the antenna to achieve a large change in the operating frequency.

[0003] The X-band to K-band is a commonly used band for microwave radars and is also a frequency band involved in future 5G and 6G communication technologies, so the radio frequency antenna as the hardware front end needs to have multiple frequency band working capabilities. Compared with frequency tuning, frequency reconfiguration can span a wider frequency band. On the other hand, frequency reconfiguration has a faster switching speed, and for the next generation of communication technologies with high bandwidth and low latency requirements, high-speed frequency reconfiguration technology obviously has a more extensive application prospect.

[0004] Metasurface technology is a rapidly emerging electromagnetic control technology in recent years. It mainly changes the amplitude and phase response to electromagnetic waves through the distribution of the capacitance and inductance structure of the surface metal, so as to realize the non-traditional control of electromagnetic waves. The research on the reflection characteristics of metasurfaces can be traced back to the proposal and application of electromagnetic band gap (EBG) structure. On the one hand, due to the special band gap characteristics of EBG structure, it can be used to suppress the surface wave level of microstrip antennas and other printed antennas. On the other hand, since EBG can produce a reflection phase from -π to π, many EBG structures that can produce a 0° reflection phase can be regarded as artificial magnetic conductors (AMC), which can realize the purposes of reducing the antenna profile height and improving the antenna gain. When the EBG structure is used to realize the 0° phase reflection, the via in the EBG structure is dispensable. Thus, the EBG structure without the via can actually be regarded as a metal surface structure printed on the upper and lower surfaces of the dielectric substrate. Many variants of the double-layer metal surface structure are used in different environments, which have derived various functions, such as the concepts of partial reflection surface and reflective metasurface.

[0005] Compared with the transmissive metasurface, the reflective metasurface is much easier to realize, because no matter how it is designed, as long as the phase superposition condition of the reflected wave is met, the reflectivity of the bottom metal plate of the reflective metasurface can be close to 1. Therefore, the main difficulty of the reflective metasurface lies in the design of the reflection phase. Unlike traditional dielectric materials and metal materials, the response bandwidth of the metasurface material is relatively narrow, and the dispersion changes rapidly, which is very suitable for frequency reconstruction antennas that work in a single band. Therefore, the realization of antenna frequency reconstruction based on the metasurface control method is a potential technical approach.

[0006] At present, the frequency reconstruction antennas based on metasurface control proposed internationally mainly adopt rotation, truncation or voltage control methods. These methods inevitably produce more parasitic electromagnetic effects, which significantly change the radiation performance of the antenna after frequency reconstruction, and the standing wave performance is not ideal. On the other hand, the use of truncation or rotation methods requires the provision of external rotation control or truncation control modules, which greatly increases the external volume of the antenna. SUMMARY

[0007] In view of the above technical problems, especially the electromagnetic parasitic effect caused by the complex regulation structure, the application provides a frequency reconfiguration waveguide antenna based on bottom end metasurface switching, and the pushing or pulling of the metasurface is controlled in the form of being attached to the slide rail at the bottom end of the antenna, so that the cross-band switching of the working frequency of the waveguide antenna in two states is realized. Since the regulation structure of the antenna is simple and the cavity has good sealing, the electromagnetic parasitic effect of the antenna and the required external volume can be effectively reduced, while the radiation performance of the reconfiguration antenna is maintained.

[0008] The technical scheme adopted by the application to achieve the above object is: a reflective metasurface structure, comprising a metal capacitor layer, a first circuit board, a metal inductor layer, a second circuit board and a metal reflection layer arranged in sequence from top to bottom.

[0009] The metal capacitor layer is arranged on the first circuit board.

[0010] The metal inductor layer is arranged on the second circuit board.

[0011] The second circuit board is arranged on the metal reflection layer.

[0012] The metal capacitor layer is pasted on the first circuit board by using a hot melt plastic film; the metal inductor layer is pasted between the first circuit board and the second circuit board by using a hot melt plastic film; and the metal reflection layer is pasted on the bottom surface of the second circuit board by using a hot melt plastic film.

[0013] The metal capacitor layer is composed of a plurality of metal capacitor layer units, the plurality of metal capacitor layer units are uniformly distributed on the first circuit board, and the spacing between any two adjacent metal capacitor layer units is equal.

[0014] The metal capacitor layer unit is rectangular.

[0015] The metal inductor layer is composed of a plurality of metal inductor layer units, the plurality of metal inductor layer units are uniformly distributed on the second circuit board, and the spacing between any two adjacent metal inductor layer units is equal.

[0016] The metal inductor layer unit is strip-shaped.

[0017] A frequency reconfiguration waveguide antenna based on bottom end metasurface switching, comprising a waveguide antenna, a feed coaxial line arranged on the waveguide antenna, and a reflective metasurface structure arranged at the bottom of the waveguide antenna.

[0018] The bottom side wall of the waveguide antenna is provided with an entrance, the reflective metasurface structure is slid into or out of the inner cavity of the waveguide antenna through the entrance by a sliding device, different standing wave resonance states exist in the inner cavity of the waveguide antenna by the different states of the reflective metasurface structure being located inside and outside the waveguide antenna, and the frequency is reconfigured by the reflection phase response of different frequency bands.

[0019] A frequency reconstruction method based on bottom end metasurface switching, comprising the following steps:

[0020] When the reflective metasurface structure covers the bottom surface of the waveguide antenna cavity, the waveguide antenna is in working state A; when the original metal bottom surface of the waveguide antenna is the bottom surface of the waveguide antenna cavity, the waveguide antenna is in working state B;

[0021] The coaxial current of the feeding coaxial line enters the inner cavity of the waveguide antenna to convert into a resonant electric field; part of the electromagnetic wave is transmitted and reflected longitudinally on the original metal bottom surface or the reflective metasurface structure in the inner cavity of the waveguide antenna, and is emitted after multiple reflection and superposition in the inner cavity of the waveguide antenna;

[0022] By the reflection phase responses of different frequency bands in working state A and working state B, the elimination of the second frequency band and the generation of the third frequency band are realized, that is, the second frequency band is reconstructed to the third frequency band.

[0023] The electromagnetic coupling between the layers of the reflective metasurface structure resonates to generate a reflection phase.

[0024] The position of the feeding coaxial line is unchanged, and the radiation patterns of the antenna in working state A and working state B are the same, and the polarization directions are the same.

[0025] The present application has the following advantages and benefits:

[0026] 1. The present application realizes a large amplitude reconstruction of the antenna operating frequency by switching in and out of a metasurface structure, and the control structure is simple and efficient, and there is no obvious electromagnetic parasitic effect.

[0027] 2. The control structure designed in the present application only needs an additional slide rail, occupies a smaller volume, and has a lower processing cost. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a working state A schematic diagram of a frequency reconstruction waveguide antenna based on bottom end metasurface switching of the present application;

[0029] Figure 2 It is a working state B schematic diagram of a frequency reconstruction waveguide antenna based on bottom end metasurface switching of the present application;

[0030] Figure 3 It is a cross-sectional schematic diagram of a metasurface in a frequency reconstruction waveguide antenna based on bottom end metasurface switching of the present application;

[0031] Figure 4 It is a top layer metal structure schematic diagram of a metasurface in a frequency reconstruction waveguide antenna based on bottom end metasurface switching of the present application;

[0032] Figure 5A middle layer metal structure diagram of a super surface in a frequency reconfigurable waveguide antenna based on bottom super surface switching;

[0033] Wherein 1 is the reflection super surface structure of the bottom of the antenna, 2 is the waveguide antenna radiation aperture, 3 is the bottom metal surface of the waveguide antenna on which the super surface structure relies, 4 is the switching sliding rail of the super surface structure, 5 is the sliding aperture of the super surface structure, 6 is the inner core of the waveguide antenna coaxial feed, 7 is the outer metal layer of the waveguide antenna coaxial feed, 8 is the array arrangement of the top layer metal of the super surface in the first horizontal direction, 9 is the array arrangement of the top layer metal of the super surface in the second horizontal direction, 10 is the spacing of the super surface array unit, 11 is the array arrangement of the middle layer metal structure of the super surface, 12 is the spacing of the middle layer metal structure of the super surface, and 13 is the bottom layer metal reflection surface structure of the super surface. DETAILED DESCRIPTION

[0034] The application will be further described in detail below in combination with the drawings and examples.

[0035] The application discloses a frequency reconfigurable waveguide antenna based on bottom super surface switching, adopts a mode of controlling the push-in or pull-out of the super surface by attaching the super surface to the sliding rail at the bottom of the antenna, and thus realizes the cross-band switching of the working frequency of the waveguide antenna in two states. Since the regulating structure of the antenna is simple and the cavity is well closed, the electromagnetic parasitic effect of the antenna and the required external volume can be effectively reduced, while the radiation performance of the reconfigured antenna is maintained.

[0036] The application comprises an antenna, a waveguide cavity and a super surface; the antenna is a rectangular waveguide antenna; the waveguide antenna has a fixed feed port, that is, a coaxial probe passing through the waveguide; the waveguide antenna radiation aperture is a rectangular aperture; and the super surface is a surface attached with a special metal structure. The sliding rail is embedded outside the bottom of the waveguide, and the super surface with a phase modulation structure can be pulled out or pushed in; by pulling out or pushing in the super surface, the antenna has two working states, that is, working state A and working state B, which correspond to two reconfigured frequency bands of the antenna respectively. In the application, the waveguide antenna can realize the rapid reconfiguration of the working frequency through the switching of the bottom metal surface, and the radiation performance remains stable.

[0037] The antenna has two working states A and B, which correspond to different positions of the super surface. This results in different standing wave resonance states of the antenna cavity. The antenna is switched in different working frequency bands. The antenna cavity metal bottom surface and the bottom sliding rail are connected with the super surface. When the bottom super surface is pulled out through the gap reserved on the side, the bottom of the cavity is a smooth metal surface. When the super surface is pushed in through the gap, the bottom of the cavity is the super surface.

[0038] The waveguide antenna has a fixed coaxial feed pin and a feed port. The feed current enters the antenna interior through the feed port, and the coaxial current is converted into a resonant electric field of the waveguide cavity through the feed pin. When the metasurface is the bottom surface of the antenna cavity, it corresponds to the working state A of the antenna. When the metal bottom surface is the bottom surface of the antenna cavity, it corresponds to the working state B of the antenna.

[0039] The metasurface structure includes metal capacitive layers 8 and 9, a metal inductive layer 11, and a metal reflective layer 13. There is no through-hole connection between the capacitive layers 8 and 9 and the inductive layer 11. The special reflection phase is generated through resonant vibration of electromagnetic coupling between the layers.

[0040] By switching the push-in and pull-out states of the metasurface, the reflection phase response of different frequency bands is realized, the second frequency band is eliminated, and the third frequency band is generated, which is equivalent to reconstructing the second frequency band to the third frequency band.

[0041] The technical scheme adopted by the application to achieve the above-mentioned purpose is: a frequency reconfiguration waveguide antenna based on bottom-end metasurface switching, comprising: a waveguide antenna 2, a metasurface 1, and a feed coaxial line 7.

[0042] The waveguide antenna disclosed by the application is a single-edge open cavity metal waveguide antenna with a rectangular aperture. The switching schematic diagram of the metasurface in different states is shown in Figure 1 and Figure 2 .

[0043] Figure 1 and Figure 2 The switching of the bottom-end metasurface material into the state of the waveguide antenna is shown. Figure 1 The sliding rail entrance at the bottom end of the waveguide antenna is shown in 5. The lower sliding rail assembly is mainly placed in 3 and 4, and the upper sliding rail assembly is fixed with the surface 1. The upper sliding rail assembly and the lower sliding rail assembly are mutually buckled to form a sliding rail, wherein the upper surface of the upper sliding cover assembly is the surface 1, and the surface of the lower sliding rail assembly is a smooth metal surface 3. The application integrates the functions of the sliding rail and the antenna, and uses the sliding rail to switch the surface structure 1 in and out to complete the reconfiguration of the working frequency of the antenna.

[0044] Figure 3 The top layer structures 8 and 9 are shown in Figure 4 as metal rectangular blocks with deep color, 10 is a PCB circuit board material (Tai Kangli TLT material, dielectric constant 2.55), and 11 is a long strip structure shown in Figure 5 with deep color. 12 is a PCB circuit board with the same material (Tai Kangli TLT material, dielectric constant 2.55). 13 is a bottom layer of planar metal copper layer. Figure 4 In the planar structure shown in Figure 5 , the length of a single rectangle is 3.5 mm, and the width is 3.5 mm.

[0045] The designed waveguide cavity mainly resonates in TE 01 Mode, which will carry almost all the electromagnetic field energy in the waveguide. By setting the waveguide size and the length of the feed line to satisfy the cut-off frequency, the waveguide antenna return loss under the SMA feed can be calculated.

[0046] The designed antenna radiates in the standard waveguide TE 01 Mode produces far-field radiation, and the waveguide aperture field is the transverse distribution of the base mode field. The waveguide antenna without the optimization of the aperture impedance structure belongs to the resonant type of antenna, and its single standing wave frequency band is necessarily narrow and is quite obviously affected by the waveguide resonance condition, so it can be frequency reconstructed by using the phase response material such as metasurface. In addition, the radiation pattern of the waveguide antenna is quite stable, and can maintain a high level of radiation gain in the process of antenna reconstruction.

[0047] The size of the waveguide antenna 1 needs to be optimized to obtain an initial feed height of 7 mm and obtain its initial return loss performance. Through theoretical analysis, the return loss performance of the antenna under different feed heights can be obtained. At this time, the standing wave operating frequency band of the antenna mainly has two segments, respectively at frequency f1 and frequency f2. With the increase of the feed height, f1 decreases, and f2 is blue-shifted. Such an effect shows that the resonant wavelength of f1 is proportional to the feed height g, and the wavelength corresponding to f2 is related to h-g. When the feed height is reduced to 6 mm, an additional new frequency band is generated at a higher frequency f3. However, if the height is increased to 13 mm, f2 and f3 will disappear at the same time.

[0048] According to the analysis of the waveguide combined with the metasurface structure, the present application proposes such an idea that through the reflection phase response of the metasurface at different frequency bands, after switching the metasurface material, the elimination of f2 and the generation of f3 are realized, that is, f2 can be reconstructed to f3.

[0049] As described above, the reflection phase dispersion of the metasurface should be able to adjust the standing wave field at f1 and f2 respectively. If the super surface structure of multiple periods covers the metal bottom surface of the waveguide, the equivalent height of the feed generated by the special reflection phase of the metasurface can be expressed as Where g1 represents the vertical distance between the feed and the upper surface of the metasurface, β is the propagation constant of the mixed mode in the z direction in the waveguide, is the reflection phase of the metasurface. Since the metal bottom of the waveguide can be regarded as a perfect conductive reflector, its reflection phase is constant at π in the microwave frequency band. In order to reconstruct the second frequency band to the third frequency band, the reflection phase of the metasurface at f2 should be-π / 18, and at f3 should be-3π / 4, which can be calculated from the expression of the equivalent height of the feed.

[0050] The designed super surface is a reflection surface combined by three layers of metal 8, 11, 13 and two layers of dielectric material 10 and 12, and a longitudinal sectional view is shown in Figure 3 The front surface of the first layer of dielectric material 10, i.e. the top layer of metal 8, is an inductive capacitive layer of the super surface, and a structural view is shown in Figure 4 The back surface of the first layer of dielectric material 10, i.e. the middle layer of metal 11, is an inductive inductive layer of the super surface, and a structural view is shown in Figure 5 The back surface of the second layer of dielectric material 12, i.e. the bottom layer of metal 13, is a complete metal reflection surface, and can also be regarded as a perfect electric conductor (PEC).

[0051] The present application mainly adopts a geometric optical method to design the electromagnetic wave traveling wave path of the reflection super surface, and although the theory of geometric optics usually ignores high-order resonant modes, it is more effective in analyzing the main modes in the resonant cavity.

[0052] The designed reflection wave path includes: electromagnetic waves enter the waveguide cavity from the coaxial feed port to perform basic mode resonance, part of the electromagnetic waves are transmitted and reflected on the longitudinal super surface, and are emitted after multiple reflections and superposition inside the waveguide structure. The reflection phase of the normal copper metal reflection surface is fixed at +π in the microwave frequency band, and the electromagnetic wave transmission phase of the super surface top layer structure is The condition for the electromagnetic wave to achieve resonance enhancement through the super surface regulation is When the resonance condition is met, the energy of the reflection super surface is close to 100%, and the overall reflection phase is equal to the reflection phase of the super surface top layer structure.

[0053] The super surface top layer structure 8 and 9 designed in the present application is mainly based on the structural deformation of a new type of super surface unit. Through the coupling resonance of 8, 9 and 11, the reflection phase of 1 is designed. The first step of the design scheme is to deform the traditional EBG structure into a uniform and isotropic capacitive surface. The dielectric gap between the top layer metal units is regarded as an equivalent capacitor, and the spacing of the array units affects the capacitance of the top layer structure. The middle layer metal structure 11 is a cross-direction transmission line structure, and each unit conductor is regarded as an equivalent inductor, and the inductance value is regulated by the width of the transmission line. According to the above reflection wave path scheme, the top layer 8, the middle layer 11 and the bottom reflection surface 13 of the super surface need to meet the resonance enhancement condition. If the three layers of structures change synchronously or slowly with respect to frequency, a stable wideband phase response can be obtained. However, the capacitive surface 9 is not easy to obtain a linearly increasing transmission phase or reflection phase, and the reflection phase curve of 13 is always +π, so if a wideband reflection phase is required, the two structures of 8 and 11 need to be synchronized, or only one layer of structure is introduced. The present application does not involve the instantaneous bandwidth of the wideband antenna, and will not be described in detail here.

[0054] The combination of the structures of the metasurfaces 8, 9 and 11 is mainly to make the metasurface produce a large change in the reflection phase in the target frequency band. When the surface current amplitude is large, the corresponding reflection phase change gradient is also large, the reflection phase change of the structure 1 is sensitive, and slight changes in the structure parameters of the structures 8 and 11 can also greatly change the reflection phase response of the structure 1. When the lengths of the structures 8 and 9 continue to increase, the surface current flow direction continues to reverse, but the amplitude becomes smaller, at this time the surface current distribution of the structure 1 is stable, the reflection phase curve gradient corresponding to the resonant state is flatter, and the change amplitude of the reflection phase is small and not easy to change.

[0055] The reflection phase of the metasurface 1 designed in the present application has a greater correlation with the patch size of the top layer 8 and 9. In the target frequency band, the reflection phase starts from -π at the low frequency band and ends at +π as the frequency increases. The width of the top layer 8 and 9 can effectively tune the phase change gradient and the reflection phase value in the target frequency band.

[0056] The metasurface unit structure designed in the present application is composed of a partially reflective surface (8, 9, 11) and a perfect metal reflecting surface 13. The structure of the partially reflective surface can be regarded as a basic resonant unit, and in order to obtain a reflectivity close to 100%, a PEC is further loaded behind the PRS. By optimizing and adjusting the parameters of the metasurface unit, the required reflection phase curve can be obtained, and the reflection phase generated thereby is -3π / 4 and -π / 18 at f2 and f3, respectively. According to the expression of the equivalent height g, which implies that the equivalent feed height is 13 mm. Compared with the waveguide antenna with a PEC reflecting surface alone (without loading the metasurface), such a reflection phase will adjust the mode field distribution of the standing wave field to produce a wavefront lag of about half a wavelength. Therefore, the effect brought by the equivalent height of 13 mm eliminates the standing wave frequency band at f2, which is similar to the standing wave characteristics of the waveguide antenna without loading the metasurface but with a real feed height of 13 mm at f2. On the other hand, due to the reflection phase dispersion characteristics of the metasurface, the reflection phase thereof at f3 is which indicates that the equivalent feed height thereof is 6 mm. Compared with the reflection phase of -π of the PEC, the difference is about one-eighth of the period, so the adjusted standing wave mode field wavefront lags about 1 mm, but such a slight change is sufficient to produce a new standing wave frequency band at f3. In this way, from the overall effect, by loading and unloading the metasurface reflecting surface, the standing wave frequency band of the waveguide antenna is reconstructed from f2 to f3.

[0057] The reflection phase of the metasurface designed in the present application has a greater correlation with the patch size of the top layer. In the target frequency band, the reflection phase starts from -π at the low frequency band and ends at +π as the frequency increases. The width of the top layer metal patch can effectively tune the phase change gradient and the reflection phase value in the target frequency band.

[0058] The antenna A and the antenna B are 180 degrees out of phase, and the polarization directions of the antenna A and the antenna B are perpendicular, and the radiation directions are opposite.

[0059] The antenna A and the antenna B are respectively any one of a slot antenna, a microstrip antenna, a horn antenna, a dipole antenna, a loop antenna, a bowtie antenna and a log-periodic antenna.

[0060] The feeding coaxial line is one, which is the inner core of the coupling coaxial line entering the waveguide cavity through the coaxial port.

[0061] The antenna has a gap on the bottom end side, and the bottom end has a metal sliding rail connected to the bottom layer of the metasurface.

[0062] The antenna has two working states, corresponding to the working state A when the metasurface is pushed in and the working state B when the metasurface is pulled out. The two working states share the same coaxial feeding line. When the waveguide antenna is in working state A, the physical thickness of the metasurface will slightly reduce the physical height of the waveguide antenna feeding end from the bottom end, and this factor has little effect on the working frequency of the waveguide antenna. The metasurface structure mainly changes the working frequency of the waveguide antenna through its dispersion phase. Due to the phase change of the metasurface from 0 to 2pi in a specific frequency band, the equivalent electrical thickness changes from 0 to 1 wavelength.

[0063] The reconfiguration tuning part of the antenna is composed of a metasurface and a metal translation sliding rail, which supports the conversion of the antenna from a PEC reflecting surface to a metasurface reflecting surface. Through the loading and unloading of the metasurface reflecting surface, the standing wave frequency band of the waveguide antenna can be reconfigured from f2 to f3, and the far-field radiation pattern of the antenna remains unchanged during the reconfiguration process, and the central radiation gain does not decrease significantly.

[0064] The top layer capacitor structure and the middle layer inductor structure of the metasurface are designed to change the reflection phase of the metasurface in the target frequency band. When the surface current amplitude is large, the corresponding reflection phase change gradient is also large, which means that the reflection phase of this structure is sensitive, and a slight change in the top layer and middle layer metal structure parameters will greatly change the overall reflection phase response. When the length of the top layer metal patch continues to increase, the surface current flow continues to reverse, but the amplitude becomes smaller, at this time the surface current distribution of the structure is stable, and the resonance state corresponding to the reflection phase curve gradient is more flat, and the change amplitude of the reflection phase is small and not easy to change.

Claims

1. A frequency reconfigurable waveguide antenna based on bottom side metasurface switching, characterized in that, The waveguide antenna, a feed coaxial line arranged on the waveguide antenna, and a reflective metasurface structure arranged at the bottom of the waveguide antenna are provided. An inlet is arranged on the sidewall of the bottom of the waveguide antenna, and the reflective metasurface structure is slid into or out of the inner cavity of the waveguide antenna through the inlet by a sliding device. Different standing wave resonance states exist in the inner cavity of the waveguide antenna by the different states of the reflective metasurface structure inside and outside the waveguide antenna, and the frequency is reconstructed by the reflection phase response of different frequency bands. The reflective metasurface structure comprises, from top to bottom, a metal capacitor layer, a first circuit board, a metal inductor layer, a second circuit board, and a metal reflection layer. The metal capacitor layer is arranged on the first circuit board. The metal inductor layer is arranged on the second circuit board. The second circuit board is arranged on the metal reflection layer. The metal capacitor layer is composed of a plurality of metal capacitor layer units, and the plurality of metal capacitor layer units are uniformly distributed on the first circuit board, and the distance between any two adjacent metal capacitor layer units is equal. The metal inductor layer is composed of a plurality of metal inductor layer units, and the plurality of metal inductor layer units are uniformly distributed on the second circuit board, and the distance between any two adjacent metal inductor layer units is equal.

2. The frequency-reconfigurable waveguide antenna based on bottom-side metasurface switching of claim 1, wherein, The metal capacitor layer is pasted on the first circuit board by using a hot melt plastic film, the metal inductor layer is pasted between the first circuit board and the second circuit board by using a hot melt plastic film, and the metal reflection layer is pasted on the bottom surface of the second circuit board by using a hot melt plastic film.

3. The frequency-reconfigurable waveguide antenna based on bottom side metasurface switching according to claim 1, wherein, The metal capacitor layer unit is rectangular.

4. The frequency-reconfigurable waveguide antenna based on bottom side metasurface switching of claim 1, wherein, The metal inductor layer unit is strip-shaped. 5.A frequency reconfiguring method based on bottom-end metasurface switching, applied to the frequency reconfiguring waveguide antenna based on bottom-end metasurface switching according to claim 1, characterized in that, The method comprises the following steps: When the reflective metasurface structure covers the bottom surface of the waveguide antenna cavity, the waveguide antenna is in working state A; when the original metal bottom surface of the waveguide antenna is the bottom surface of the waveguide antenna cavity, the waveguide antenna is in working state B. The coaxial current of the feed coaxial line is converted into a resonant electric field in the inner cavity of the waveguide antenna. Part of the electromagnetic waves are transmitted and reflected longitudinally on the original metal bottom surface or the reflective metasurface structure in the inner cavity of the waveguide antenna, and are emitted after multiple reflection and superposition in the inner cavity of the waveguide antenna. The reflection phase of different frequency bands in working state A and working state B is used to realize the elimination of the second frequency band and the generation of the third frequency band, i.e. reconstructing the second frequency band to the third frequency band.

6. The method of claim 5, wherein the bottom side surface is a bottom side surface of a bottom side surface switch. The electromagnetic coupling between the layers of the reflective metasurface structure resonates to generate a reflection phase.

7. The method of claim 5, wherein the bottom side surface is a metasurface. The position of the feed coaxial line is unchanged, and the radiation patterns and polarization directions of the waveguide antenna in working state A and working state B are the same.

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