Electric control liquid crystal 2-bit reconfigurable folding transmission array antenna

Abstract

The invention relates to the technical field of reconfigurable communication antenna equipment, and particularly discloses a liquid crystal-based high-aperture efficiency low-profile reconfigurable folding transmission array antenna design. The invention aims to solve the problems of insufficient aperture efficiency and high profile height in the existing reconfigurable folding array. The invention designs a novel transmission unit, and the unit integrates upper and lower layers of radiation and receiving patches with a polarization selection function, and a strip line-based liquid crystal phase shifter for realizing phase compensation. In order to minimize the profile height, the main transmission array is composed of a novel transmission unit, the auxiliary reflection array adopts a polarization conversion unit, and the interaction between the main transmission array and the auxiliary reflection array is used for folding the transmission path of electromagnetic waves. Meanwhile, the microstrip patch antenna replaces a traditional horn antenna to serve as an array feed source, so that the overall profile is reduced. In order to improve the aperture efficiency, the liquid crystal phase shifter is elaborately optimized to meet the requirement of 2-bit phase quantization, so that the phase modulation precision and the accuracy of array plane phase distribution are improved. Compared with a traditional space feed antenna and a folding array, the overall outline of the design is reduced by 2 / 3, meanwhile, the aperture efficiency is remarkably improved, and excellent two-dimensional beam scanning performance is kept.

Description

Technical Field

[0001] The present invention relates to the technical field of reconfigurable communication antenna equipment, and in particular to a 2-bit reconfigurable folding transmission array antenna of an electrically controlled liquid crystal. Background Art

[0002] With the increasing shortage of communication frequency band resources and the increasing number of communication devices, future frequency bands will face serious channel attenuation problems. High-gain antennas are the key to communication construction, and the common solution is to use array antennas. However, traditional array antennas are usually large in size and are not suitable for compact environments. Therefore, researching and designing a high-gain, low-profile and more compact array antenna is of great significance for future communications. In addition, with the increasing complexity of communication and electromagnetic environments, the reconfigurability of antennas has also become a focus of future communication system construction. Antennas with reconfigurable functions can intelligently adjust the radiation direction and concentrate energy in the target area. However, existing studies have shown that current reconfigurable antennas still face challenges in achieving low profiles and high aperture efficiency. Therefore, it is urgent to design an antenna that is both reconfigurable, high-gain and small in size (low profile) to cope with increasingly complex communication environments.

[0003] There have been a lot of achievements in the research of reconfigurable arrays, including reconfigurable reflective arrays and transmissive arrays. However, most existing studies use PIN diode solutions. As the functions become more complex, the number of PIN diodes required increases, which makes the design of the feeding network more difficult and significantly increases the cost of the antenna. Traditional reconfigurable arrays usually use space feeding from above or below, which is difficult to integrate and has a high profile. To solve this problem, some studies have tried to introduce folded structures into array design, but most of these solutions are still based on PIN diode technology. Due to the limitation of the number of PIN diodes, these solutions usually use 1-bit quantization solutions, resulting in a gain loss of about 3dB. Using multiple PIN diodes can achieve high-bit quantization, but the array design requires multiple feed lines, which makes the design of arrays with hundreds of units more difficult, so only 1bit quantization can be used. Due to the insufficient phase modulation accuracy, the gain of the antenna array is attenuated to a certain extent, which is contrary to the original intention of designing array antennas to increase gain. When the 3dB gain attenuation is converted to the antenna, half of the energy is lost. In future communication frequency bands, due to the reduction of wavelength, the loss of electromagnetic waves in free space is extremely large, and such gain loss is unacceptable. Therefore, it is particularly important to design an array antenna with higher quantization scheme, higher gain, lower profile and reconfigurable performance. Summary of the invention

[0004] In view of the problems existing in other reconfigurable transmission array antennas in the prior art, such as complex antenna structure, common use of PIN diodes, high profile, difficulty in integration and low aperture efficiency, the present invention discloses a high-aperture efficiency, low-profile reconfigurable folding transmission array antenna based on liquid crystal. This technical solution effectively reduces the profile height of the transmission array antenna (reduced to 1 / 3 of the original array profile height), and the folding structure design successfully solves the integration problem, while improving the aperture efficiency of the antenna and maintaining good two-dimensional beam scanning performance. Compared with traditional PIN diodes, the liquid crystal material modulation scheme adopted by the present invention has a wider application prospect and can adapt to the needs of future frequency bands. Therefore, the present invention has important reference value and application potential in the field of reconfigurable array antennas.

[0005] The invention discloses a 2-bit reconfigurable folded transmission array antenna of electrically controlled liquid crystal, comprising a main transmission array, a sub-reflection array and a microstrip patch antenna feed source.

[0006] To achieve the above advantages, the technical solution of the present invention is:

[0007] A new transmission unit of the main transmission array is designed, and the unit period is set to 5mm (greater than half of the free space wavelength of 28 GHz). The main transmission array is provided with a plurality of mutually arranged and mutually independent new transmission array units. The units all adopt a 2-bit phase quantization scheme.

[0008] The transmission array unit consists of 15 parts from top to bottom, including receiving patch, upper dielectric plate (dielectric constant is 3.66), upper metal ground, liquid crystal layer, liquid crystal frame (dielectric constant is 2.2), phase shift layer, lower metal ground, lower dielectric plate (dielectric constant is 3.66), radiation patch, upper dipole patch, lower dipole patch, upper metal column, upper conversion column, lower metal column, and lower conversion column. The sub-reflection array unit consists of polarization conversion structure, dielectric plate layer (dielectric constant is 3.5) and ground.

[0009] The feed source adopts a microstrip patch antenna with a simple structure. The microstrip patch antenna is installed in the center of the sub-reflection array and occupies an area of ​​3×3 sub-reflection units.

[0010] The new transmission unit is composed of a liquid crystal phase shifter (the function is realized by the combination of the liquid crystal layer and the phase shift layer) and a polarization selection layer (upper and lower layers of dipole patches and upper and lower layers of conversion columns). The adjustable phase range of the new transmission unit exceeds 270°, and the unit has both the function of adjusting the phase difference and polarization selection.

[0011] The phase shift layer of the new transmission unit receives electromagnetic waves from the upper receiving patch through the upper conversion column and works with the liquid crystal layer to complete the phase difference adjustment. At the same time, the electromagnetic waves that have completed the phase difference adjustment are transmitted to the lower radiation patch through the lower conversion column. The upper conversion column passes through the upper dielectric layer and then passes through a hole with a radius slightly larger than itself through the upper metal ground to connect to the phase shift layer. Similarly, the lower conversion column and the phase shift layer are also connected to the lower metal ground in this way.

[0012] The phase shift layer of the new transmission unit is connected to the upper and lower conversion columns by winding around the upper and lower metal columns, and the strip line of the phase shift layer is cut to reduce the discontinuity at the bend. The place where the phase shift layer is connected to the upper and lower conversion columns is replaced by a circular piece with a radius slightly larger than the conversion column for impedance matching.

[0013] The upper and lower metal grounds and liquid crystal frames of the new transmission unit wrap the liquid crystal and phase shift layer to form a liquid crystal stripline phase shifter. The metal ground is slightly smaller than the dielectric layer to facilitate the subsequent feeding network design.

[0014] The sub-reflection array unit that constitutes the sub-reflection array is a polarization conversion structure composed of four metal strips divided into two groups arranged at a certain angle. The angle between a group of metal strips is 38°. The metal strips are on the upper layer of the dielectric plate, and the lower layer of the dielectric plate is covered with metal ground.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The transmission array antenna of the present invention is tuned based on liquid crystal, which is different from the previous PIN diode. It can be used in future frequency bands and can be mass-produced using existing liquid crystal production lines, which has future application value and significance.

[0017] Compared with the reconfigurable array in the prior art, the present invention adopts a new type of transmission array unit, which has a novel unit design structure and is expanded by using the feed line of the phase shift layer. The upper and lower metal grounds and the liquid crystal layer form a liquid crystal-based stripline phase shifter, which cleverly realizes the function of adjusting the unit phase difference. The design structure is novel and the transmission loss is low.

[0018] Compared with the reconfigurable array in the prior art, the present invention adopts a new type of transmission array unit, and the unit design is based on magnetic dipoles. The upper and lower layers of the unit use magnetic dipole units to radiate and receive electromagnetic waves. This structure widens the unit bandwidth.

[0019] Compared with the reconfigurable array in the prior art, the present invention adopts a new type of transmission array unit, which uses two upper and lower oppositely arranged receiving and radiating patches to select and radiate the same polarized wave, and cleverly realizes the polarization selection function.

[0020] Compared with the reconfigurable array in the prior art, the present invention adopts a new type of transmission array unit, which can meet the design requirements of the 2-bit quantization scheme, significantly improve the control accuracy of the array, make the phase distribution of the antenna array more accurate, and thus improve the aperture efficiency. Compared with the existing reconfigurable array, the present invention has significant advantages in aperture efficiency, successfully achieves a balance between high aperture efficiency and excellent two-dimensional scanning capability, and has the advantages of low profile and easy integration. In two-dimensional space, the present invention can achieve a scanning range of -60° to 60°. Compared with the "Design of Ka-band Transmission Phased Array Antenna Based on Liquid Crystal" of the University of Electronic Science and Technology, although both use liquid crystal 2-bit transmission array technology, the document uses two layers of liquid crystal layers, resulting in a complex structure and belonging to a traditional transmission array structure with a high cross-section. The present invention only uses one layer of liquid crystal tuning layer, and the structure is simpler. In addition, the present invention adopts a folded array structure, which folds the transmission path of the electromagnetic wave through the interaction between the sub-reflection array and the main transmission array, reducing the antenna profile height to 1 / 3 of the traditional transmission array. The final profile height is only 1.5λ0 (the free space wavelength corresponding to 24GHz), the focal length ratio is 0.24, and the simulated peak aperture efficiency reaches 30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of a 2-bit reconfigurable folded transmission array antenna of an electrically controlled liquid crystal according to the present invention;

[0022] Figure 2 It is a schematic structural diagram of a novel transmission unit constituting a 2-bit reconfigurable folded transmission array antenna of an electrically controlled liquid crystal according to the present invention;

[0023] Figure 3 It is a schematic structural diagram of a polarization conversion unit of a sub-reflection array of a 2-bit reconfigurable folded transmission array antenna constituting an electrically controlled liquid crystal according to the present invention;

[0024] Figure 4 It is a schematic structural diagram of a microstrip patch antenna constituting a radiation feed source of a 2-bit reconfigurable folded transmission array antenna of an electrically controlled liquid crystal according to the present invention;

[0025] Figure 5 It is a schematic diagram of the folding radiation principle of the 2-bit reconfigurable folding transmission array antenna of the electrically controlled liquid crystal of the present invention;

[0026] Figure 6 Four phase states corresponding to the 2-bit reconfigurable transmission unit of the present invention vary with frequency;

[0027] Figure 7 This is a simulation performance diagram of the polarization conversion unit of the sub-reflection array of the 2-bit reconfigurable folded transmission array antenna constituting the electrically controlled liquid crystal of the present invention;

[0028] Figure 8 The four transmission states corresponding to the 2-bit reconfigurable transmission unit of the present invention vary with frequency;

[0029] Fig. 9 This is a graph showing the variation of the directivity coefficient of the 2-bit reconfigurable folded transmission array antenna of the electrically controlled liquid crystal according to the present invention with the scanning angle;

[0030] Fig.10 a, 10b, 10c and Fig.10 d is a 3D simulation effect diagram of a 2-bit reconfigurable folded transmission array antenna of an electrically controlled liquid crystal according to the present invention with beams pointing to 0 degrees, 30 degrees, and maximum angles of 60 degrees and -60 degrees;

[0031] Figure numerals: 1-main transmission array, 2-sub-reflection array, 3-feed source, 4-new transmission unit, 5-receiving plate, 6-upper dielectric plate, 7-upper metal ground, 8-liquid crystal layer, 9-liquid crystal frame, 10-phase shift layer, 11-lower floor, 12-lower dielectric plate, 13-radiation patch, 14-upper dipole patch, 15-lower dipole patch, 16-upper metal column, 17-upper conversion column, 18-lower Layer metal column, 19-lower layer conversion column, 20-sub-reflection array unit, 21-polarization conversion structure, 22-dielectric plate layer, 23-polarization conversion unit metal floor, 24-microstrip patch antenna, 101-circular piece of conversion column, 131-upper layer magnetic dipole, 141-lower layer magnetic dipole, 241-patch antenna, 242-feeding network, 243-dielectric plate, 244-floor, 245-SMA connector. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0033] Reference Figure 1 The present invention includes a main transmission array 1, a sub-reflection array 2 and a microstrip patch antenna feed 3. The feed 3 is fixed at the center of the sub-reflection array 2, occupying a 3×3 unit size area of ​​the main and sub-reflection array surfaces. The feed 3 uses a microstrip patch antenna 24, which has a simple structure, a stable radiation beam, and is easy to control. The profile height of the array is determined by the radiation beam angle of the microstrip patch antenna 24, and it also needs to be designed in combination with the sub-reflection array.

[0034] The main transmission array 1 includes N×N periodically arranged reconfigurable transmission units 4, and in this example, N is 13;

[0035] Reference Figure 2The novel transmission unit 4 comprises 13 parts, including a receiving patch 5, an upper dielectric plate 6 (with a dielectric constant of 3.66), an upper metal ground 7, a liquid crystal layer 8, a liquid crystal frame 9 (with a dielectric constant of 2.2), a phase shift layer 10, a lower metal ground 11, a lower dielectric plate 12 (with a dielectric constant of 3.66), a radiation patch 13, an upper dipole patch 14, a lower dipole patch 15, an upper metal column 16, an upper conversion column 17, a lower metal column 18, and a lower conversion column 19. The sub-reflection array unit 20 is composed of a polarization conversion structure 21, a dielectric plate layer 22 (with a dielectric constant of 3.5) and a ground 23. The feed source adopts a microstrip patch antenna 24 with a simple structure. The novel transmission unit is composed of a liquid crystal phase shifter (the function is realized by the liquid crystal layer 8 and the phase shift layer 10) and a polarization selection layer (upper and lower layers of dipole patches 14, 15 and upper and lower layers of conversion columns 16, 17).

[0036] Reference Figure 3 The sub-reflection array unit 20 is composed of a polarization conversion structure 21 and a dielectric plate 22. The polarization conversion structure is composed of four metal strips divided into two groups arranged at a certain angle. The angle between a group of metal strips is 38°. The metal strips are on the upper layer of the dielectric plate 22, and the lower layer of the dielectric plate is covered with a metal ground 11. The structure can realize polarization conversion in a broadband of 26GHz-31GHz.

[0037] Reference Figure 4 , using the microstrip patch antenna 24 as the feed source of the antenna array for radiation, the feed source antenna has a simple structure, and the profile height of the array is also determined by the radiation capability of the microstrip patch antenna. The microstrip patch antenna is composed of a patch antenna 241, a feeding network 242, a dielectric board 243 and a floor 244. For the convenience of feeding, a back SMA connector is used for feeding 245.

[0038] Reference Figure 5 , combined with Figure 1To explain, the folded transmission array consists of three parts: the main transmission surface composed of transmission units with polarization selection and phase compensation functions, the actual feed source, and the sub-reflection array unit with polarization conversion function. The microstrip patch antenna located on the sub-reflection array radiates, and the X-polarization (Y-polarization) is radiated to the main transmission surface. The electromagnetic waves with the same polarization as the main transmission array unit are reflected, and the electromagnetic waves with the opposite polarization to the main transmission array unit are directly transmitted. After the X-polarized (Y-polarized) electromagnetic wave is radiated to the sub-reflection array, the X-polarized (Y-polarized) beam is converted into Y-polarized (X-polarized) by the polarization conversion unit. The electromagnetic wave that has completed the polarization conversion is radiated again to the main transmission array surface. Since the polarization of the beam is converted, the new beam required for polarization twisting is transmitted through the main transmission array, and the phase shifter of the main transmission array unit performs phase compensation on the new electromagnetic wave. The electromagnetic wave that has completed phase compensation is radiated in the direction of the shaping. According to the principle of ray tracing, since the antenna undergoes secondary reflection and the phase compensation array is different from the reflective array, the antenna profile is reduced to 1 / 3 of that of an ordinary transmission array antenna. According to the equivalent principle, the virtual feed is located at the position of the traditional transmission array, and the actual feed is located at the center of the antenna's sub-reflective array. The profile height H is reduced by 2 / 3 without significantly affecting the antenna performance. At the same time, this structure also makes it easy to place the feed on the sub-reflective array, facilitating the integration of the antenna, so that the beam scanning is not affected in the main radiation area.

[0039] According to the above description, the transmission array unit needs to have phase compensation and polarization selection functions, and the sub-reflection array unit has a polarization conversion function.

[0040] In order to achieve the desired radiation beam when the array radiates, the compensation phase distribution on the main transmission surface is accurately calculated by the following formula to obtain the desired beam, thereby realizing beam scanning. For the calculation method of phase compensation of different units on the transmission array, according to the coordinate system, it is assumed that the beam direction of the antenna is According to the theory of array antenna, the phase compensation calculation formula of the transmission array is as follows: R (x i ,y i ) is the compensation phase required for the ith unit, (x i ,y i ) is the coordinate of the ith unit, k0 is the propagation constant in vacuum, d i is the distance from the phase center of the feed to the center of the ith unit. Assume that the coordinates of the phase center of the feed are (x f ,y f , z f ), then d i The calculation formula is as follows:

[0041]

[0042]

[0043] In order to make the unit obtain the above phase distribution, the transmission unit needs to be tuned by liquid crystal. The working principle of the phase shift layer of this unit is based on the inverted microstrip line of liquid crystal. The liquid crystal molecules are rod-shaped. The liquid crystal molecules between the metal plates will be deflected by the voltage. Generally, the voltage state is divided into three types: bias voltage V b , starting voltage V th , cut-off voltage V sat When the bias voltage is less than the start voltage, the liquid crystal molecules are arranged horizontally due to the anchoring effect of the orientation layer. The dielectric constant at this time is expressed as ε r，⊥ As the voltage gradually increases, when the bias voltage is greater than the cut-off voltage, the liquid crystal molecules deflect to the maximum angle, and the dielectric constant at this time is expressed as ε r，|| When the bias voltage is between the cut-off voltage and the start-up voltage, the liquid crystal molecules are in an intermediate state, and the dielectric constant of the liquid crystal layer increases with the increase of the voltage. However, this state is not linear. The simulation parameters of the liquid crystal used in the present invention at 24GHz are (ε r，⊥ =2.5,tanδε r，⊥ =4.8E-03,ε r，|| =3.5,tan δε r，|| =2.7E-03).

[0044] The liquid crystal phase shifter used in the present invention is in the form of a strip line. The phase difference provided by the liquid crystal phase shifter is related to the length of the phase shift layer. Through optimization design, a phase change greater than 270° can be obtained to achieve 2-bit quantization. The phase shifter is cut at the bend to reduce the discontinuity at the bend.

[0045] When the radiation direction of the transmitted wave is θ m By determining, we can get the transmission phase Φ required by the transmission unit in the i-th column and j-th row. R (x ij ), when 0°≤Φ R (x ij )<90°, the phase of the cell in the i-th column and j-th row is adjusted to state “0”. R (x ij )<180°, adjust the phase of the cell in the i-th column and j-th row to state "1". When 90°≤Φ R (x ij )<180°, adjust the phase of the cell in the i-th column and j-th row to state "3". When 180°≤Φ R (x ij)<270°, adjust the phase of the unit in the i-th column and j-th row to state "4". According to the above principle, the N×N columns of transmission units are arranged with 2-bit coding, so that the directional pattern can point to a specific direction. Changing the coding sequence can realize the reconfigurable characteristics of the antenna directional pattern. Based on the above method, the array can be quantized with 2-bit to achieve good two-dimensional scanning capability.

[0046] The following is a further description of the technical effects of the present invention in combination with the simulation results:

[0047] Simulation conditions:

[0048] HFSS, 3D electromagnetic field simulation software. Multi-purpose full-wave 3D electromagnetic (EM) simulation software, used to design and simulate high-frequency electronic products, such as antennas, components, interconnects, connectors, ICs and PCBs. The present invention uses HFSS microwave simulation function to simulate and analyze the transmission coefficient, transmission phase and radiation pattern of the antenna unit.

[0049] Simulation content:

[0050] refer to Figure 6 The figure is a simulation result diagram of the new transmission unit proposed in the present invention at 26GHz to 31GHz, with normal incident waves with X polarization and Y polarization (modes 1 and 2) acting on the unit. The simulation results are as follows Figure 6 As shown. By changing the dielectric constant of the liquid crystal, the four phase states change linearly in a wide frequency range. The phase difference between state 1 and state 4 is greater than 270°, and the phases in two adjacent states meet the requirements of 2-bit phase quantization. This is conducive to antenna control. In the range of 26 GHz to 31 GHz, there is enough control phase difference.

[0051] refer to Figure 7 This is a simulation result of the transmission and reflection performance of the new transmission unit proposed in the present invention at 26GHz to 31GHz. It can be seen that when the radiation condition is Y-polarized wave incident, the antenna has the ability to reflect X-polarized waves and receive Y-polarized waves. This shows that the transmission unit has a good polarization selection function and meets the structural requirements.

[0052] refer to Figure 8 This is a performance simulation diagram of the polarization conversion unit constituting the sub-reflection array of the array antenna described in the present invention. It can be seen that within the broadband range of 26GHz-31GHz, the unit has good polarization conversion capability and the incident Y-polarized electromagnetic wave is converted into an X-polarized electromagnetic wave.

[0053] refer to Fig. 9This is a graph showing the variation of the directivity coefficient of the high-aperture efficiency, low-profile reconfigurable folded transmission array antenna based on liquid crystal with scanning angle. It can be seen that the antenna array has good beam scanning capability. According to the principle of symmetry, only one surface scanning capability is shown here.

[0054] refer to Fig.10 a, 10b, 10c and Fig.10 d is a 3D simulation effect diagram of the 2-bit reconfigurable folded transmission array beam pointing to 0deg, 30deg and the maximum angles of 60deg and -60deg, which more clearly demonstrates the beam scanning capability of the array antenna.

Claims

1. A 2-bit reconfigurable folded transmission array antenna of electrically controlled liquid crystal, comprising a main transmission array (1), a secondary reflection array (2) and a microstrip patch antenna feed source (3). The main transmission array (1) is characterized in that a plurality of mutually arranged and independent new transmission array units (4) are arranged on the main transmission array (1). The transmission array unit (4) is composed of the following parts: The receiving patch (5), the upper dielectric plate (6) (dielectric constant 3.66), the upper metal ground (7), the liquid crystal layer (8), the liquid crystal frame (9) (dielectric constant 2.2), the phase shift layer (10), the lower metal ground (11), the lower dielectric plate (12) (dielectric constant 3.66), the radiation patch (13), the upper dipole patch (14), the lower dipole patch (15), the upper metal column (16), the upper conversion column (17), the lower metal column (18) and the lower conversion column (19), a total of 15 parts. The sub-reflection array unit (20) is composed of a polarization conversion structure (21) and a dielectric plate layer (22) (dielectric constant 3.5) and a ground (23). The feed source adopts a simple microstrip patch antenna (24), which is composed of a patch antenna (241), a feeding network (242), a dielectric plate (243) (dielectric constant 2.2) and a ground (244). In order to simplify the feeding operation, the bottom SMA connector is used for feeding (245). The new transmission unit is composed of a liquid crystal phase shifter (realized by a liquid crystal layer (8) and a phase shift layer (10)) and a polarization selection layer (upper and lower dipole patches (14) (15) and upper and lower conversion rods (16) (17)), with an adjustable phase difference of more than 270°, and has both adjustable phase difference and polarization selection functions. The center frequency of the unit design is 28 GHz.

2. According to claim 1, a high-aperture efficiency, low-profile reconfigurable folded transmission array antenna based on liquid crystal is composed of 13 parts: a receiving patch (5), an upper dielectric plate (6), an upper metal ground (7), a liquid crystal layer (8), a liquid crystal frame (9), a phase shift layer (10), a lower metal ground (11), a lower dielectric plate (12), a radiation patch (13), an upper dipole patch (14), a lower dipole patch (15), an upper metal column (16), an upper conversion column (17), a lower metal column (18), and a lower conversion column (19). The sub-reflection array unit (20) is composed of a polarization conversion structure (21), a dielectric plate layer (22), and a ground (23). The feed source adopts a microstrip patch antenna (24) with a simple structure. The novel transmission unit is composed of a liquid crystal phase shifter (the function of which is realized by a liquid crystal layer (8) and a phase shift layer (10)) and a polarization selection layer (upper and lower layers of dipole patches (14) (15) and upper and lower layers of conversion columns (16) (17)).

3. The 2-bit reconfigurable folded transmission array antenna of electrically controlled liquid crystal according to claim 1, characterized in that: The novel transmission unit is composed of two magnetic dipoles. The upper magnetic dipole (131) is used for receiving electromagnetic waves and is located on the upper dielectric layer. The lower magnetic dipole (141) is used for radiating electromagnetic waves and is located on the lower dielectric layer. The transmission unit has a polarization selection function and can only receive and radiate electromagnetic waves in the same radiation direction as the dipole patch.

4. The 2-bit reconfigurable folded transmission array antenna of electrically controlled liquid crystal according to claim 1, characterized in that: The upper magnetic dipole (131) of the novel transmission unit is used for receiving electromagnetic waves. It is surrounded by four periodic patches and the upper metal column (16) to form a magnetic dipole to assist in receiving electromagnetic waves (the upper periodic patch (14) is connected to the upper metal column (16), and the metal column (16) penetrates the upper dielectric layer (6) and is connected to the upper metal ground (7)), and widens the bandwidth. The lower magnetic dipole (141) and the lower metal column (18) also form a magnetic dipole to radiate electromagnetic waves (similarly, the lower periodic patch (15) is connected to the lower metal column (18), and the metal column (18) penetrates the lower dielectric layer (12) and is connected to the lower metal ground (11)), and is also used to widen the bandwidth.

5. The 2-bit reconfigurable folded transmission array antenna of electrically controlled liquid crystal according to claim 1, characterized in that: The phase shift layer (10) of the novel transmission unit receives electromagnetic waves from the upper receiving patch (5) through the upper conversion column (17) and works with the liquid crystal layer (8) to provide a phase difference. At the same time, the electromagnetic waves with phase adjustment are transmitted to the lower radiation patch (13) through the lower conversion column (19). The upper conversion column (17) passes through the upper dielectric layer (6) and then passes through a hole with a radius slightly larger than itself through the upper metal ground (7) to connect with the phase shift layer (10). Similarly, the lower conversion column (19) and the phase shift layer (10) are also connected in the same way.

6. The 2-bit reconfigurable folded transmission array antenna of electrically controlled liquid crystal according to claim 1, characterized in that: The phase shift layer (10) of the novel transmission unit meanders around the upper and lower metal pillars and cuts the corners at the same time to reduce the discontinuity at the bend. The place where the phase shift layer (10) is connected to the upper and lower conversion pillars is replaced by a round piece (101) with a radius slightly larger than the conversion pillar for impedance matching.

7. The 2-bit reconfigurable folded transmission array antenna of electrically controlled liquid crystal according to claim 1, characterized in that: The upper and lower metal ground layers and the liquid crystal frame (9) of the novel transmission unit wrap the liquid crystal and the phase shift layer (8) to form a liquid crystal stripline phase shifter. The size of the metal ground layer is slightly smaller than that of the dielectric layer, which is convenient for the subsequent feeding network design.

8. The 2-bit reconfigurable folded transmission array antenna of electrically controlled liquid crystal according to claim 1, characterized in that: The sub-reflection array unit (20) constituting the sub-reflection array (2) is a polarization conversion structure composed of four metal strips divided into two groups arranged at a certain angle, wherein the angle between the metal strips in one group is 38 degrees. The metal strips are on the upper layer of the dielectric plate (22), and the lower layer of the dielectric plate is covered with a metal ground (11).

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