Reconfigurable fabry-perot resonator antenna based on programmable metasurface

Abstract

The application discloses a kind of based on programmable super surface wave beam reconfigurable fabry-perot resonant cavity antenna, including microstrip antenna feed, upper layer reflector and lower layer reflector.Upper and lower layer reflector is fixed with plastic screw and forms a half-wave fabry-perot resonant cavity.The upper layer reflector is programmable super surface, which is composed of 1-bit transmission phase programmable unit arranged periodically.By controlling circuit output different voltage, programmable unit can be switched between "0" and "1" two encodings, respectively present 0 degree and 180 degree transmission phase, and its reflection phase remains unchanged in different encoding state, while reflectivity is high, combined with lower layer reflector to form resonant cavity, without changing operating frequency, adjusting the encoding distribution of programmable super surface can realize wave beam reconfigurable.The antenna has the characteristics of low profile, high gain, real-time switching, large scanning angle, etc., and has important application in microwave communication, radar and other fields.

Description

Technical Field

[0001] This invention relates to a beam-reconfigurable Fabry-Perot resonator antenna based on a programmable metasurface, belonging to the fields of novel artificial electromagnetic materials and microwave antennas. Background Technology

[0002] Novel artificial electromagnetic materials, also known as electromagnetic metamaterials, are artificial materials composed of periodic or aperiodic arrangements of subwavelength-sized units. They can exhibit unique phenomena not found in nature and achieve special electromagnetic properties. Metasurfaces, as two-dimensional equivalent planar structures, can reduce the longitudinal thickness and structural complexity of three-dimensional electromagnetic metamaterials. In recent years, they have been widely used to control electromagnetic waves, reducing losses, simplifying fabrication, and facilitating system integration. The concepts of digital encoding and programmable metamaterials / metasurfaces were proposed in 2014 by Professor Cui Tiejun's research group at Southeast University. Using digital encoding, real-time control of electromagnetic waves can be achieved. Under the control of FPGA and other control circuits, programmable metamaterials / metasurfaces with real-time switchable functions can be formed, showing broad application prospects. (Reference [1]: TJCui, MQQi, X.Wan, J.Zhao, and Q.Cheng, "Coding metamaterials, digital metamaterials and programmable metamaterials," Light-Science & Applications, vol.3, p.e218, Oct 2014.) However, currently programmable metasurfaces require an external feed antenna for excitation. Usually, the distance between the feed antenna and the metasurface increases with the size of the metasurface. This results in a very large cross-section and a large volume after the programmable metasurface is integrated with the feed antenna, making it inconvenient to integrate.

[0003] On the other hand, Fabry-Perot resonant cavity antennas, also known as partially reflective surface antennas, feature high gain, low profile, narrow beamwidth, and low loss. They can achieve high-gain radiation while meeting requirements for small size, compact structure, and low cost, attracting widespread research in industry. Compared to array antennas, they eliminate the need for complex phase-shifting power dividers, reducing losses. In recent years, reconfigurability and beam scanning have become research hotspots for Fabry-Perot antennas based on practical application needs. Although beam reconfigurability can be achieved in Fabry-Perot resonant cavity antennas by designing feed antenna arrays or adjustable reflector floors, these methods suffer from drawbacks such as complex feeding structures, small beam deflection angles, and large gain losses. Summary of the Invention

[0004] Technical Problem: The purpose of this invention is to solve the problems of small scanning angle and large gain loss in the beam reconfiguration of existing Fabry-Perot antennas, as well as the problem of large overall profile of ordinary programmable metasurfaces under external feed antenna excitation, and to provide a new design idea for convenient and efficient beam reconfiguration based on programmable metasurfaces.

[0005] Technical solution: To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A beam-reconfigurable Fabry-Perot resonant cavity antenna based on a programmable metasurface mainly consists of a microstrip antenna feed (3), an upper reflector (1), and a lower reflector (2). The upper and lower reflectors are fixed together with plastic screws (4) to form a half-wavelength Fabry-Perot resonant cavity. The upper reflector is a high-reflectivity transmissive programmable metasurface, which changes its coded distribution in real time under the drive of the FGPA control circuit, thereby realizing the reconfigurability of the antenna's radiating beam.

[0007] Furthermore, the programmable metasurface consists of periodically arranged 1-bit transmission phase programmable units (5), each unit integrating two switching diodes. The two switching diodes are connected in parallel and in reverse, and are symmetrically placed on the upper surface of the programmable unit. The FPGA control circuit can provide high and low levels of opposite polarity to turn on different switching diodes on the programmable unit, so that they present transmission phases of 0 degrees and 180 degrees respectively, corresponding to the two codes "0" and "1".

[0008] Furthermore, the programmable unit (5) constituting the programmable metasurface is a multi-layered structure, comprising, in sequence, an upper metal patch (51), an upper dielectric substrate (55), an intermediate metal patch (52), a lower dielectric substrate (56), a lower metal patch (53), two switching diodes connected to the upper metal patch, and a metal via (54) passing through the intermediate metal patch and connecting the upper and lower metal patches. The upper and lower metal patches are respectively connected to the high and low levels of the FPGA control circuit.

[0009] Furthermore, the reflection phase of the lower surface of the programmable metasurface remains unchanged under different coding states, while maintaining a high reflectivity (greater than 0.9). Combined with the lower reflector, it forms a Fabry-Perot resonant cavity, satisfying the antenna resonance condition. The electromagnetic wave excited by the microstrip antenna is reflected multiple times within the cavity, and each transmitted electromagnetic wave is modulated by the transmission phase of the programmable unit, achieving beam reconfigurability.

[0010] Furthermore, each column of cells in the programmable metasurface uses the same bias voltage and exhibits the same encoding state. By changing the encoding distribution of the programmable metasurface through the voltage output by the FPGA control circuit, beam reconfiguration in one-dimensional plane can be achieved.

[0011] Beneficial effects: Compared with the prior art, the advantages of the present invention are:

[0012] 1. The beam-reconfigurable Fabry-Perot resonator antenna based on a programmable metasurface in this invention does not require a complex phase-shifting power divider network. Reconfigurability of the antenna's radiating beam can be achieved simply by changing the coding distribution of the programmable metasurface. It offers advantages such as high gain, low loss, compact structure, large-angle beam deflection, and minimal gain loss. Furthermore, it reduces the overall profile of a conventional programmable metasurface under external feed antenna excitation to approximately half a wavelength, achieving a low-profile integrated design.

[0013] 2. The present invention is simple in design, easy to manufacture, and easy to implement. The resonant cavity antenna can be fabricated using conventional printed circuit board technology. Commercial switching diodes are soldered onto each programmable unit, and the control circuit can use a field-programmable gate array (FPGA), a microcontroller, or a CPLD, etc.

[0014] 3. The antenna in this invention can also be configured into an antenna array to further improve gain and beam reconfigurability. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the working principle of a beam-reconfigurable Fabry-Perot resonant cavity antenna based on a programmable metasurface.

[0016] Figure 2 (a) is a schematic diagram of the overall and partial structure of a beam-reconfigurable Fabry-Perot resonant cavity antenna based on a programmable metasurface. (b), (c), and (d) are schematic diagrams of the upper metal pattern on the upper reflector of the resonant cavity, the lower metal pattern on the upper reflector of the resonant cavity, and the microstrip antenna, respectively.

[0017] Figure 3 (a) is a schematic diagram of the programmable unit, and (b), (c) and (d) are schematic diagrams of the upper metal patch, the middle metal patch, and the lower metal patch, respectively.

[0018] Figure 4 It is a curve showing the variation of the reflection and transmission coefficient amplitudes of the programmable unit with frequency under two encoding conditions.

[0019] Figure 5 It is a curve showing the phase of the reflection coefficient of the programmable unit as a function of frequency under two encoding methods.

[0020] Figure 6 It is a curve showing the phase of the transmission coefficient of the programmable unit as a function of frequency under two encoding methods.

[0021] Figure 7 It is a curve showing how the return loss of the antenna changes with frequency under different coding sequences.

[0022] Figure 8 It is the E-plane gain pattern of the antenna under different coding sequences.

[0023] Figure 9 It achieves reconfigurable 3D and 2D beam patterns by outputting different coded sequences from an FPGA. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings.

[0025] In this invention, the upper reflector of the Fabry-Perot resonant cavity antenna is a programmable metasurface composed of periodically arranged 1-bit programmable transmission phase units. Each unit integrates two switching diodes. Under two different switching states, the unit structure presents two different transmission phases to the electromagnetic wave: 0 degrees and 180 degrees, marked as "0" and "1" respectively. The reflection phase of the lower surface of the programmable metasurface remains unchanged under different encoding states, while maintaining high reflectivity. Combined with the lower reflector, it forms a Fabry-Perot resonant cavity, satisfying the antenna resonance condition. The electromagnetic wave excited by the microstrip antenna is reflected multiple times within the cavity. Each transmitted electromagnetic wave is modulated by the transmission phase of the programmable unit, achieving beam reconfigurability.

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] Figure 1 This is a schematic diagram illustrating the working principle of a beam-reconfigurable Fabry-Perot resonator antenna based on a programmable metasurface. Electromagnetic waves excited by the microstrip antenna feed are reflected back and forth within the half-wavelength Fabry-Perot resonator. When the encoding state of the programmable metasurface is consistent, the transmitted electromagnetic waves are superimposed in phase each time, improving the gain. The FPGA control circuit alters the arrangement of the encoding sequence on the programmable digital metasurface, adjusting the phase distribution of the transmitted electromagnetic waves on the output plane, thus achieving beam deflection. Different digital encoding sequences correspond to different deflected beams under different conditions. By pre-storing these sequences in the FPGA, switching the encoding sequences during use achieves beam reconfiguration.

[0028] Figure 2 (a) is a schematic diagram of the overall and partial structure of a beam-reconfigurable Fabry-Perot resonant cavity antenna based on a programmable metasurface. The entire resonant cavity antenna consists of an upper reflector 1, a lower reflector 2, a microstrip antenna feed 3, and plastic screws 4 distributed at the four corners to fix the upper and lower reflectors. The upper reflector 1 is a programmable metasurface, mainly composed of 12×12 programmable elements 5 arranged periodically. The metal patterns on the upper and lower surfaces of the programmable metasurface are as follows... Figure 2 As shown in (b) and (c), the microstrip antenna feed 3 has a U-shaped slotted structure, which is used to increase the bandwidth.

[0029] Figure 3 (a) is a schematic diagram of the programmable unit. The programmable unit 5 is a multi-layer structure consisting of three metal patches and two dielectric substrates, including, in sequence, an upper metal patch 51, an upper dielectric substrate 55, a middle metal patch 52, a lower dielectric substrate 56, a lower metal patch 53, two switching diodes connected to the upper metal patch, and a metal via 54 passing through the middle metal patch and connecting the upper and lower metal patches. The upper metal patch 51 is a rectangular ring structure, with a smaller rectangular metal patch at the center of the unit. The two switching diodes connect the smaller rectangular metal patch to the larger rectangular metal ring, one on the left and one on the right. The side length of the middle metal patch 52 is equal to the period length of the unit structure, and it has a ring-shaped opening at the center. The side length of the lower metal patch 53 is slightly less than the period length of the unit structure, and it has a U-shaped groove in the middle. The metal via 54 passes through the center of the upper dielectric substrate 55, the middle metal patch 52, and the lower dielectric substrate 56, connecting the centers of the upper and lower metal patches. Each programmable unit integrates two switching diodes connected in parallel and reverse, symmetrically placed on the encoding unit. The control circuit provides two voltages of the same magnitude but opposite polarity, so the two diodes operate in two states: "on-off" and "off-on," corresponding to "0" and "1" encodings, respectively. Since only one diode is conducting and the other is off in both encoding states, they are electromagnetically identical. However, the positions of the conducting and off diodes are interchanged in the two encoding states, which is equivalent to rotating the upper metal patch of the unit by 180 degrees, which is also equivalent to rotating the current direction by 180 degrees. This creates a 180-degree transmission phase difference between the two encoding states. The working principle of this programmable unit is as follows: the lower metal patch 53 first receives the induced current from the microstrip antenna feed 3 in the resonant cavity, and then the upper metal patch 51 receives the current through the metal via 54 before radiating it.

[0030] Figure 4-6 These are curves showing the changes in the amplitude, phase, and phase of the reflection and transmission coefficients of the programmable unit as a function of frequency under two encoding methods. Figure 4 As shown, under both "0" and "1" encoding, the amplitudes of the reflection and transmission coefficients do not change with the encoding state switching, maintaining a high lower surface reflectivity. At the 10GHz frequency point, the reflection coefficient of the programmable unit's lower surface remains around 0.96. Furthermore, the reflection coefficient phase also does not change with the encoding state switching; at the 10GHz frequency point, the reflection phase of the programmable unit's lower surface remains around -163 degrees. Figure 5As shown. In summary, the amplitude and phase of the reflection coefficient of the lower surface of the programmable unit do not change with the switching of the encoding state, maintaining a stable high reflectivity and phase. The switching of the encoding state does not disrupt the resonance of the resonant cavity, providing perfect conditions for constructing a Fabry-Perot resonant cavity. Finally, as different diodes on the programmable unit are turned on, corresponding to different encoding states, the phase of the transmission coefficient of the programmable unit also maintains a 180-degree phase difference over a large frequency range, achieving modulation of the transmission phase.

[0031] Figure 7 These are curves showing the return loss of the antenna as a function of frequency under different coding sequences. The curves for the return loss versus frequency under the five different coding sequences are basically the same in shape, which verifies that the programmable metasurface design can provide stable lower surface reflection amplitude and phase, and that different coding sequences do not change the antenna's resonant state. In addition, the antenna is well matched at 10 GHz, and switching the coding sequence does not cause the antenna's operating frequency to shift.

[0032] Figure 8 The E-plane gain pattern of the antenna under different coding sequences. Under the seven codes "000000000000", "000000111111", "000011110000", "000111000111", "100011001110", "00110011001111", and "011011001001", the antenna beam deflection angle gradually increases from 0 degrees to 60 degrees. Since the programmable unit used is a 1-bit transmission phase modulation unit, only symmetrical dual-beam radiation can be generated in directions deviating from 0 degrees. Therefore, the gain of each beam in the dual-beam configuration is theoretically 3 dBi less than the 0-degree single-beam under the "000000000000" coding. Further design of a 2-bit programmable unit could remove this limitation and achieve single-beam scanning.

[0033] Figure 9 This method achieves reconfigurable 3D and 2D beam patterns by outputting different coded sequences from an FPGA. Different coded sequences are stored in the FPGA, with each sequence corresponding to an antenna pattern. Depending on the application scenario, the FPGA control circuit outputs the appropriate coded sequence, and the antenna radiates the corresponding beam, thus achieving beam reconfiguration.

Claims

1. A beam-reconfigurable Fabry-Perot resonant cavity antenna based on a programmable metasurface, characterized in that, The antenna includes an upper reflector (1), a lower reflector (2), and a microstrip antenna feed (3); the upper reflector (1) and the lower reflector (2) form a half-wavelength Fabry-Perot resonant cavity; the upper reflector (1) is a high-reflectivity transmissive programmable metasurface, which changes its coding distribution in real time under the drive of the FGPA control circuit, thereby realizing the reconfigurability of the antenna radiation beam; Among them, the programmable metasurface, which serves as the upper reflector (1), is composed of periodically arranged 1-bit transmission phase programmable units (5). Each programmable unit (5) integrates two switching diodes. The two switching diodes are connected in parallel and in opposite directions and are symmetrically placed on the upper surface of the programmable unit (5). The FPGA control circuit provides high and low levels with opposite polarities to conduct different switching diodes on the programmable unit, so that they present transmission phases of 0 degrees and 180 degrees respectively, corresponding to the two codes "0" and "1". Among them, the programmable unit (5) constituting the programmable metasurface is a multi-layer structure, which includes an upper metal patch (51), an upper dielectric substrate (55), an intermediate metal patch (52), a lower dielectric substrate (56), a lower metal patch (53), two switching diodes connected to the upper metal patch (51), and a metal via (54) passing through the intermediate metal patch (52) and connecting the upper and lower metal patches; the upper and lower metal patches are respectively connected to the high and low levels of the FPGA control circuit; The upper metal patch (51) is a rectangular ring structure, and there is a small rectangular metal patch at the center of the unit. Two switching diodes connect the small rectangular metal patch to the large rectangular metal ring, one on the left and one on the right. The side length of the middle metal patch (52) is equal to the period length of the unit structure, and there is a ring-shaped opening at the center. The side length of the lower metal patch (53) is slightly less than the period length of the unit structure, and there is a U-shaped groove in the middle of the patch.

2. The beam-reconfigurable Fabry-Perot resonator antenna based on a programmable metasurface according to claim 1, characterized in that, The reflection phase of the lower surface of the upper reflector (1) remains unchanged under different coding states, and the reflectivity is greater than 0.

9. Combined with the lower reflector (2), it forms a Fabry-Perot resonant cavity, which satisfies the antenna resonance condition. The electromagnetic wave excited by the microstrip antenna feed (3) is reflected multiple times in the cavity. Each transmitted electromagnetic wave is modulated by the transmission phase of the programmable unit (5) to realize beam reconfigurability.

3. The beam-reconfigurable Fabry-Perot resonator antenna based on a programmable metasurface according to claim 1, characterized in that, In the programmable metasurface (1) which serves as the upper reflector, each column of cells uses the same bias voltage and presents the same encoding state. The encoding distribution of the programmable metasurface is changed by the voltage output by the FPGA control circuit, thereby realizing beam reconfigurability in one-dimensional plane.

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