Patent Publication Number: US-2023163481-A1

Title: Liquid crystal antena and fabrication thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of Chinese Patent Application No. 202111385462.X, filed on Nov. 22, 2021, the content of which is incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure generally relates to the field of wireless communication technologies and, more particularly, relates to a liquid crystal antenna and a method for fabricating a liquid crystal antenna. 
     BACKGROUND 
     Liquid crystal antenna is a new type of array antenna based on the liquid crystal phaser, which is widely used in satellite receiving antenna, vehicle radar, base station antenna and other fields. The liquid crystal phaser is the core component of the liquid crystal antenna. The liquid crystal phaser and the ground layer form an electric field to control the deflection of liquid crystal molecules to realize the control of the liquid crystal equivalent dielectric constant, and then to realize the adjustment the phase of the electromagnetic wave. Liquid crystal antennas have broad application prospects in the fields of satellite receiving antennas, vehicle radars, and 5G base station antennas. 
     However, the yield of liquid crystal antenna products is very low. Further, customized liquid crystal antenna products are very expensive and costly. In addition, due to the need for customized manufacturing, the liquid crystal antenna cannot be manufactured in large quantities, so commercial mass production cannot be realized at present, which restricts the development of liquid crystal antenna technology. 
     Therefore, there is a need to provide a liquid crystal antenna and a fabrication method that can realize the antenna function, reduce process difficulty and production cost, and improve production efficiency and product yield is a technical problem to be solved by those skilled in the art. The disclosed liquid crystal antenna and the method for fabricating the liquid crystal antenna are direct to solve one or more problems set forth above and other problems in the arts. 
     SUMMARY 
     One aspect of the present disclosure provides a liquid crystal antenna. The liquid crystal antenna includes a first substrate; a second substrate opposite to the first substrate; and a liquid crystal layer disposed between the first substrate and the second substrate. A first conductive layer is disposed on a side of the first substrate facing toward the second substrate; and a second conductive layer is disposed on a side of the second substrate facing toward the first substrate. The second conductive layer at least include a plurality of radiation electrodes. An external metal layer is disposed on a side of the first substrate away from the liquid crystal layer; and the external metal layer is connected to a fixed potential. 
     Another aspect of the present disclosure provides a method for forming a liquid crystal antenna. The method includes providing a first substrate and forming a first conductive layer on a side of the first substrate; providing a second substrate and forming a second conductive layer on a side of the second substrate, wherein the second conductive layer at least includes a plurality of radiation electrodes of block shape; pairing the first substrate with the second substrate, and disposing a liquid crystal layer between the first substrate and the second substrate, wherein the first conductive layer is disposed opposite to the second conductive layer; and disposing an external metal layer on a side of the first substrate away from the liquid crystal layer to cause the external metal layer to be connected with a fixed potential. 
     Another aspect of the present disclosure includes providing a liquid crystal antenna. The liquid crystal antenna includes a plurality of antenna units spliced together. Each of the plurality of liquid crystal antenna includes a first substrate; a second substrate opposite to the first substrate; and a liquid crystal layer disposed between the first substrate and the second substrate. A first conductive layer is disposed on a side of the first substrate facing toward the second substrate; and a second conductive layer is disposed on a side of the second substrate facing toward the first substrate. The second conductive layer at least include a plurality of radiation electrodes. An external metal layer is disposed on a side of the first substrate away from the liquid crystal layer; and the external metal layer is connected to a fixed potential. 
     Other aspects of the present disclosure can be understood by those skilled in the art in light of the description, the claims, and the drawings of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings incorporated in the specification and constituting a part of the specification illustrate the embodiments of the present disclosure, and together with the description are used to explain the principle of the present disclosure. 
         FIG.  1    illustrates a top view of an exemplary liquid crystal antenna according to various disclosed embodiments of the present disclosure; 
         FIG.  2    illustrates an A-A′-sectional view of the exemplary liquid crystal antenna in  FIG.  1   ; 
         FIG.  3    illustrates an exemplary structure of a side of first substrate facing toward the second substrate in  FIG.  2   ; 
         FIG.  4    illustrates an exemplary structure of a side of the second substrate facing toward the first substrate in  FIG.  2   ; 
         FIG.  5    illustrates an exemplary structure of a side of the first substrate away from the second substrate in  FIG.  2   ; 
         FIG.  6    illustrates another exemplary liquid crystal antenna according to various disclosed embodiments of the present disclosure; 
         FIG.  7    illustrates a B-B′-sectional view of the exemplary liquid crystal antenna in  FIG.  6   ; 
         FIG.  8    illustrates an exemplary structure of a side of the first substrate facing toward the second substrate in  FIG.  7   ; 
         FIG.  9    illustrates another exemplary liquid crystal antenna according to various disclosed embodiments of the present disclosure; 
         FIG.  10    illustrates a C-C′-sectional view of the exemplary liquid crystal antenna in  FIG.  9   ; 
         FIG.  11    illustrates an exemplary structure of the side of the first substrate facing toward the second substrate in  FIG.  10   ; 
         FIG.  12    illustrates an exemplary structure of a side of the second substrate facing toward the first substrate in  FIG.  10   ; 
         FIG.  13    illustrates an exemplary structure of a side of the first substrate facing away from the second substrate in  FIG.  10   ; 
         FIG.  14    illustrates another exemplary A-A′-sectional view of the exemplary liquid crystal antenna in  FIG.  1   ; 
         FIG.  15    illustrates another exemplary A-A′-sectional view of the exemplary liquid crystal antenna in  FIG.  1   ; 
         FIG.  16    illustrates an exemplary structure after the liquid crystal antenna is bonded with a driving circuit in  FIG.  14   ; 
         FIG.  17    illustrates an exemplary structure after the liquid crystal antenna is bonded with a driving circuit in  FIG.  15   ; 
         FIG.  18    illustrates another exemplary A-A′-sectional view of the exemplary liquid crystal antenna in  FIG.  1   ; 
         FIG.  19    illustrates another exemplary A-A′-sectional view of the exemplary liquid crystal antenna in  FIG.  1   ; 
         FIG.  20    illustrates a flow chart of an exemplary fabrication method of a liquid crystal antenna according to various disclosed embodiments of the present disclosure; 
         FIG.  21    illustrates an exemplary structure formed by the method in  FIG.  20    after forming the first conductive structure; 
         FIG.  22    illustrates an exemplary structure formed by the method in  FIG.  20    after forming the second conductive structure; 
         FIG.  23    illustrates an exemplary structure formed by the method in  FIG.  20    after pairing the first substrate and the second substrate; 
         FIG.  24    illustrates an exemplary structure formed by the method in  FIG.  20    after forming the external metal layer; 
         FIG.  25    illustrates a flow chart of another exemplary fabrication method of a liquid crystal antenna according to various disclosed embodiments of the present disclosure; 
         FIG.  26    illustrates a flow chart of another exemplary fabrication method of a liquid crystal antenna according to various disclosed embodiments of the present disclosure; 
         FIG.  27    illustrates an exemplary structure formed by the method in  FIG.  26    after forming the first conductive structure; 
         FIG.  28    illustrates an exemplary structure formed by the method in  FIG.  26    after forming the second conductive structure; 
         FIG.  29    illustrates an exemplary structure formed by the method in  FIG.  26    after pairing the first substrate and the second substrate; 
         FIG.  30    illustrates an exemplary structure formed by the method in  FIG.  26    after forming the external metal layer; 
         FIG.  31    illustrates a flow chart of another exemplary fabrication method of a liquid crystal antenna according to various disclosed embodiments of the present disclosure; 
         FIG.  32    illustrates an exemplary structure formed by the method in  FIG.  31    after forming an external metal layer of whole surface on the third substrate; 
         FIG.  33    illustrates an exemplary structure formed by the method in  FIG.  31    after forming the external metal layer; 
         FIG.  34    illustrates another exemplary structure formed by the method in  FIG.  31    after forming the external metal layer; 
         FIG.  35    illustrates a flow chart of another exemplary fabrication method of a liquid crystal antenna according to various disclosed embodiments of the present disclosure; 
         FIG.  36    illustrates an exemplary external metal layer formed by the fabrication method of the liquid crystal antenna in  FIG.  35   ; 
         FIG.  37    illustrates an exemplary liquid crystal after forming the external metal layer in the  FIG.  36   ; 
         FIG.  38    illustrates an exemplary structure formed by the method in  FIG.  35    after forming the external metal layer; 
         FIG.  39    illustrates an exemplary liquid crystal after forming the external metal layer in the  FIG.  36   ; 
         FIG.  40    illustrates another exemplary liquid crystal antenna according to various disclosed embodiments of the present disclosure; 
         FIG.  41    illustrates a D-D′-sectional view of the exemplary liquid crystal antenna in  FIG.  40   ; 
         FIG.  42    illustrates an exemplary structure of a side of the fourth substrate facing toward the fifth substrate in  FIG.  41   ; 
         FIG.  43    illustrates an exemplary structure of a side of the fifth substrate facing toward the fourth substrate in  FIG.  41   ; 
         FIG.  44    illustrates an exemplary structure of a side of the fourth substrate facing away from the fifth substrate in  FIG.  41   ; 
         FIG.  45    illustrates another D-D′-sectional view of the exemplary liquid crystal antenna in  FIG.  40   ; 
         FIG.  46    illustrates an exemplary structure of a side the fourth substrate facing away from the fifth substrate in  FIG.  45   ; 
         FIG.  47    illustrates another D-D′-sectional view of the exemplary liquid crystal antenna in  FIG.  40   ; and 
         FIG.  48    illustrates another D-D′-sectional view of the exemplary liquid crystal antenna in  FIG.  40   . 
     
    
    
     DETAILED DESCRIPTION 
     Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that unless specifically stated otherwise, the relative arrangement, numerical expressions and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present disclosure. 
     The following description of at least one exemplary embodiment is actually only illustrative, and in no way serves as any limitation to the present disclosure and its application or use. 
     The techniques, methods, and equipment known to those of ordinary skill in the relevant fields may not be discussed in detail, but where appropriate, the techniques, methods, and equipment should be regarded as part of the specification. 
     In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiment may have different values. 
     It should be noted that similar reference numerals and letters indicate similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further discussed in the subsequent drawings. 
     The existing liquid crystal antenna structure is generally improved based on the structure of the liquid crystal display panel. Because the liquid crystal display technology and the liquid crystal antenna technology both adopt the deflection performance of the liquid crystal, those skilled in the art carry out some designs on the basis of the liquid crystal display structure. To achieve the effect of the liquid crystal antenna, for example, the published patent number CN107658547A discloses a liquid crystal antenna including two substrates and a liquid crystal structure located between the two substrates. The upper and lower surfaces of the upper substrate and the upper and lower surfaces of the lower substrate are all provided with the structures to achieve the liquid crystal antenna function, such as phaser, a metal ground structure, and a metal radiation electrode structure. The details can be referred to the description of the publication text. Although the liquid crystal antenna of the patent document has completed the manufacture of phaser, metal grounds, and metal radiation electrodes to achieve electromagnetic radiation requirements, the manufacturing process involves the manufacturing process of copper plating on both sides of the antenna. In the double-sided copper plating process, the conductive structure on one side of the upper substrate needs to be protected, and a protective layer is added to the surface, and then the other side of the upper substrate is turned over for the copper plating and patterning. Finally, after copper plating is completed on the upper and lower surfaces of the upper substrate, if the protective layer will affect the dielectric properties of the liquid crystal antenna, a process step to remove the protective layer needs to be added. For example, the double-sided copper plating process involves a single-sided protection and a double-sided patterning. The process not only has a large number of process consumables, but also has a low product yield, which greatly increases the manufacturing cost and manufacturing difficulty, and is likely to adversely affect the commercial promotion of the final products. 
     The present disclosure provides a liquid crystal antenna and a method for forming a liquid crystal antenna, which may realize the function of the antenna while reducing process difficulty and production cost, and improving production efficiency and product yield. 
       FIG.  1    illustrates an exemplary liquid crystal antenna according to various disclosed embodiments of the present disclosure (it is understandable that to clearly illustrate the structure of this embodiment,  FIG.  1    is filled with transparency).  FIG.  2    illustrates an A-A′-sectional view of the exemplary liquid crystal antenna in the  FIG.  1   .  FIG.  3    is a schematic structural view of a side of the first substrate facing toward the second substrate in  FIG.  2   .  FIG.  4    is a schematic structural view of a side of the second substrate facing toward the first substrate in  FIG.  2   .  FIG.  5    is a schematic structural view of a side of the first substrate facing away from the second substrate in  FIG.  2   . 
     As shown in  FIGS.  1 - 5   , a liquid crystal antenna  000  provided in one embodiment of present disclosure may include a first substrate  10  and a second substrate  20  (not filled in  FIG.  1   ), and a liquid crystal layer  30  disposed between the first substrate  10  and the second substrate  20 . A first conductive layer  101  may be disposed on the side of the first substrate  10  facing toward the second substrate  20 ; a second conductive layer  201  may be disposed on the side of the second substrate  20  facing toward the first substrate  10 ; and the second conductive layer  201  may at least include a plurality of radiation electrodes  2011 . Further, an external metal layer  40  may be disposed on the side of the first substrate  10  facing away from the liquid crystal layer  30 , and the external metal layer  40  may be connected to a fixed potential. 
     Specifically, the liquid crystal antenna  000  of this embodiment may include the first substrate  10  and the second substrate  20  disposed opposite to each other, and the liquid crystal layer  30  may be disposed between the first substrate  10  and the second substrate  20 . The side of the first substrate  10  facing the second substrate  20  may include the first conductive layer  101 , and the first conductive layer  101  may be configured to provide a portion of the structures that realize the antenna function, such as phaser structures, etc. The side of the second substrate  20  facing the first substrate  10  may include the second conductive layer  201 ; and the second conductive layer  201  may at least include the plurality of radiation electrodes  2011 , and the radiation electrodes  2011  may be configured to radiate the microwave signal of the liquid crystal antenna  000 . In such an embodiment, the materials of the first conductive layer  101  and the second conductive layer  201  may not be specifically limited, and may only need to be conductive. For example, the first conductive layer  101  and the second conductive layer  201  may be made of a metal conductive material, such as copper, etc. 
     The first conductive layer  101  in this embodiment may also include a driving electrode  1011  and a bias voltage signal line  1012 . The driving electrode  1011  may have a block shape as shown in  FIG.  3   , and the driving electrode  1011  may be electrically connected to an external power supply terminal (not shown in the figure, for example, a voltage signal can be provided by binding a driving chip) through at least one bias voltage signal line  1012 . Each driving electrode  1011  may independently control the liquid crystal antenna by at least one bias voltage signal line  1012 . For example, the bias voltage signal line  1012  may be configured to transmit the voltage signal provided by the external power supply terminal to the driving electrode  1011  to control the deflection electric field of the liquid crystal molecules of the liquid crystal layer  30  between the first substrate  10  and the second substrate  20 . 
     Further, as shown in  FIG.  3   , the plurality of driving electrodes  1011  may be uniformly distributed on the first substrate  10  as an array. It can be understood that the specific number, distribution, and material of the driving electrodes  1011  on the side of the first substrate  10  facing toward the second substrate  20  may be set by those skilled in the art according to actual conditions, and there is no specific limitation here. The figure in this embodiment only exemplarily shows the wiring structure of each bias voltage signal line  1012 , which includes but is not limited to this, and may also be other layout structures, which is not limited in this embodiment. 
     In one embodiment, in addition to the plurality of radiation electrodes  2011 , the second conductive layer  201  of the second substrate  20  of this embodiment may also include a power division network structure  2012  and a plurality of phaser structures connected to the power division network structure  2012 . Further, each phaser structure may have a one-to-one correspondence with the driving electrode  1011  on the first substrate  10  to generate the deflection electric field to drive the liquid crystal molecules of the liquid crystal layer  30 . Through the voltage transmitted to the driving electrode  1011  by the bias voltage signal  1012 , the intensity of the electric field formed between the phaser structure and the driving electrode  1011  may be controlled to adjust the deflection angle of the liquid crystal molecules of the liquid crystal layer  30  in the corresponding space to change the dielectric constant of the liquid crystal layer  30  to change the phase shift of the microwave signal in the liquid crystal layer  30 . 
     The power division network structure  2012  of this embodiment may be configured to input microwave signals to each phaser structure. The phaser structure may be a microstrip line  2013 , and the shape of the microstrip line  2013  may be zigzag (as shown in  FIG.  4   ) or spiral (not shown in the figure) or other structures, the microwave signal transmitted by the power division network structure  2012  may be further transmitted to each phaser structure, and the zigzag or spiral phaser structure may be able to increase the facing area between the phaser structure and the driving electrode  1011  to ensure that as many liquid crystal molecules as possible in the liquid crystal layer  30  may be in the electric field formed by the phaser structure and the driving electrode  1011 , and the flipping efficiency of the liquid crystal molecules may be improved. This embodiment does not limit the shape and distribution of the phaser structure, and the phaser may only need to be able to realize the transmission of microwave signals. It can be understood that, to clearly illustrate the structure of this embodiment,  FIG.  4    only illustrates 16 phaser structures on the second substrate  20 , but it is not limited to this number. In specific implementation, the number of phaser structures may be arranged as an array according to actual needs. 
     In one embodiment, the radiation electrodes  2011  of this embodiment may be connected to the phaser structure. After the phase shift of the microwave signal is completed, the phase shifted microwave signal may transmitted to the radiation electrodes  2011  through the phaser structure, and the microwave signal of the liquid crystal antenna  000  may radiated out through the radiation electrodes  2011 . 
     This embodiment only exemplifies the structures that may be included in the first conductive layer  101  and the second conductive layer  201  that may implement the antenna function, including but not limited to this. The first conductive layer  101  on the first substrate  10  and the second conductive layer  201  on the second substrate  20  may also include other structures that may realize the antenna function, as long as that the first conductive layer  101  may be disposed on the side of first substrate  10  facing toward the second substrate  20 , the second conductive layer  201  may be disposed on the side of the second substrate  20  facing toward the first substrate  10 , and the radiation electrode  2011  may also be disposed in the liquid crystal cell. For example, all the structures integrated in a liquid crystal cell and configured to realize the antenna function may be only arranged on one side surface of the same substrate to avoid the introduction of the process of manufacturing conductive layers on both sides of the substrate during the manufacturing process of the liquid crystal antenna  000 . That is, this embodiment may not need to use the processes of fabricating and patterning conductive metal layers on both sides of the substrate. Accordingly, the processes of fabricating a conductive structure on one side of the substrate and then turning it over to fabricate another conductive structure on the other side surface, and exposing, developing, and etching may be omitted, the manufacturing difficulty and manufacturing cost may be reduced, and the production efficiency and the product yield may be increased. 
     In one embodiment, the side of the first substrate  10  away from the liquid crystal layer  30  may further include an external metal layer  40  connected to a fixed potential. The external metal layer  40  may be fixed on the first substrate  10  through an adhesive component (not filled). In some embodiments, the fixed potential of the optional external metal layer  40  may also be provided by a boned driving chip, which is not described in detail in this embodiment. It can be understood that the external metal layer  40  may refer to a structure that may be additionally fabricated on the surface of the first substrate  10  away from the liquid crystal layer  30  after the first substrate  10  and the second substrate  20  are formed into a liquid crystal cell, such that, in the process of manufacturing the liquid crystal cell, it may be avoided to provide conductive metal layers on both side of the first substrate  10 . Accordingly, the difficulty of the production process may be reduced, and the production efficiency may be improved. 
     In one embodiment, the external metal layer  40  may be disposed on the entire surface of the first substrate  10  on the side of the first substrate  10  away from the liquid crystal layer  30  after the liquid crystal cell  30  is formed, and the external metal layer  40  may be connected to a fixed potential. It can be understood that the specific potential value of the external metal layer  40  connected to the fixed potential may not be specifically limited in this embodiment, and it may be selected and set according to actual requirements during specific implementation. 
     The external metal layer  40  of this embodiment may not only be used as a reflective layer, but when the microwave signal is phase-shifted, it may ensure that the microwave signal only propagates in the liquid crystal cell of the liquid crystal antenna  000  during the phase-shifting process, and may prevent it from diverging outside the liquid crystal antenna. When microwave signals are transmitted to the external metal layer  40 , the microwave signals may be reflected back through the external metal layer  40  of the whole surface structure. The external metal layer  40  connected to the fixed potential may also be used to shield external signals to avoid external signals to interfere with the microwave signals to ensure the accuracy of the phase shift of the microwave signals, which may be beneficial to increase the radiation gain of the antenna. Moreover, because the external metal layer  40  of this embodiment may be a whole surface structure, when the first substrate  10  after the formation of the liquid crystal cell is arranged on the side of the liquid crystal layer  30  away from the liquid crystal layer  30 , the requirements of the bonding accuracy may be reduced, which may beneficial to reduce the manufacturing difficulty and to further reduce manufacturing costs. 
     The liquid crystal antenna provided by this embodiment may not only realize the function of the antenna by providing the first conductive layer  101 , the second conductive layer  201 , and the external metal layer  40 , but also avoid the use of metal layers on both sides of the substrate. The process may also eliminate the need to form a conductive layer on one side of the substrate and then protect it and then fabricate a conductive layer on the other side of the substrate; and it may reduce the steps of removing the protective layer. Thus, the production steps and the process difficulty may be significantly reduced, and the product yield of liquid crystal antenna may be improved. 
     Further, in one embodiment, the film layer connected to the fixed potential may be used as the external metal layer  40 , which may be additionally fabricated on the outside of the substrate after the first substrate  10  and the second substrate  20  are formed into a liquid crystal cell. In the overall structure of the liquid crystal antenna  000 , the external metal layer  40  of the entire surface structure may not only be used as a reflective layer such that when the microwave signal is transmitted to the external metal layer  40 , the microwave signal may be reflected back through the external metal layer  40  of the entire surface structure to avoid its divergence to the outside of the liquid crystal antenna, the external metal layer  40  connected to the fixed potential may also be used to shield external signals to avoid interference from external signals to microwave signals, thereby ensuring the accuracy of phase shifting of microwave signals, which may be beneficial to increase the radiation gain of the antenna. Therefore, the external metal layer  40  of this embodiment may be a whole-surface structure and may not need to be patterned. Then, after the first substrate  10  and the second substrate  20  are formed into a liquid cell, the external metal layer  40  may additionally be fabricated on the substrate, the problem of alignment accuracy may not need to be considered and may just need to fix the external metal layer  40  of the whole structure directly on the outside of the substrate after the liquid crystal cell is formed. The process may be simple, and the use of expensive alignment equipment may be omitted. Thus, the production cost and process difficulty may be significantly reduced. 
     In one embodiment, the external metal layer  40  of a whole surface structure connected to the fixed potential may be fabricated on the outside of the substrate after the liquid crystal cell is formed. Thus, the consideration of the light transmittance and the alignment of the radiation holes may be avoided when other patterned conductive structures of the liquid crystal antenna are disposed on the outside of the substrate after the liquid crystal cell is formed. Thus, the process difficulty and production cost may be significantly reduced. It should be noted that the first substrate  10 , the second substrate  20 , and the liquid crystal layer  30  of this embodiment may form a liquid crystal cell, and the specific process of forming the liquid crystal cell may be set by those skilled in the art according to the actual situation, which is not limited here. For example, a frame sealant  50  may be coated on the first substrate  10 , and then the liquid crystal is dispersed by the liquid crystal injection technology, and the first substrate  10  and the second substrate  20  may be aligned and bonded according to the alignment marks on the second substrate  20 , and the sealant may be cured. The sealant  50  may make the first substrate  10  and the second substrate  20  adhere stably to obtain the liquid crystal cell. Specifically, the materials of the first substrate  10  and the second substrate  20  may also be set by those skilled in the art according to the actual situation, which is not limited here. Exemplarily, the first substrate  10  and the second substrate  20  may be any rigid material of glass and ceramics or may also be any flexible material of polyimide and silicon nitride. Such materials may not absorb microwave signals, that is, the insertion loss in the microwave frequency band may be substantially small. Thus, it may be beneficial to reduce the signal insertion loss, and may greatly reduce the loss of microwave signals in the transmission process. 
     It should be further explained that this embodiment only exemplarily illustrates the structure of the liquid crystal antenna  000 , but is not limited to this, and may also include other structures, such as an alignment layer between the first substrate  10  and the second substrate  20 , etc. It can be understood with reference to the structure of the liquid crystal antenna in the related art, which is not described in detail in this embodiment. This embodiment is only an example to illustrate the structure that the first conductive layer  101  and the second conductive layer  201  may be provided, including but not limited to the above-mentioned structure and working principle. In specific implementation, it can be set according to the required functions of the liquid crystal antenna. The examples are not repeated here. 
     In some embodiments, referring to  FIGS.  1 - 5   , the external metal layer  40  may be electrically contacted to ground. For example, the fixed potential connected to the external metal layer  40  may be a ground signal. The ground signal may be provided by a driving chip bonded to the liquid crystal antenna  000  (for example, on the edge of the first substrate  10 , the area may be provided with a bonding area for the driving chip bonding. this embodiment will not be repeated here. The details may be referred to the technology of substrate bonding chip in the related art for understanding). Because the liquid crystal antenna  000  itself may need to be bonded with the driving chip to provide a driving voltage signal, and the ground signal in the driving chip may one of the more common and more useful signals, the fixed potential of the external metal layer  40  of this embodiment may be set as the ground signal to use the driving chip needed to be bonded with the liquid crystal antenna  000  needs to provide the fixed potential signal to avoid the complexity of the structure. Further, the external metal layer  40  connected to the ground signal and the radiation electrode  2011  on the second substrate  20  may form an antenna cavity structure to form a radiation gap at the edge of the radiation electrode  2011 , which may be beneficial to radiate microwave signals. 
       FIG.  6    is a schematic diagram of a top view of another exemplary liquid crystal antenna according to various disclosed embodiments of the present disclosure (understandably, for clarity of the structure of this embodiment,  FIG.  6    is filled with transparency).  FIG.  7    is a schematic diagram of a B-B′-sectional view of the exemplary liquid crystal antenna in  FIG.  6   .  FIG.  8    is an exemplary structure of the side of the second substrate facing toward the first substrate in  FIG.  7    (it can be understood that the structural diagram of the surface of the first substrate facing the second substrate of this embodiment may be understood with reference to  FIG.  3   , and the structural diagram of the side of the first substrate away from the second substrate may be understood with reference to  FIG.  5   ). 
     As shown in  FIGS.  6 - 8   , and referring to  FIG.  3    and  FIG.  5   , in one embodiment, the first conductive layer  101  may include a plurality of driving electrodes  1011 ; and the second conductive layer  201  may also include a power division network structure  2012  and a plurality of microstrip lines  2013 . The power division network structure  2012  may be connected to the signal input terminal  2014 . One end of the microstrip line  2013  may be connected to the power division network structure  2012 ; and the other end of the micro-ribbon  2013  may be respectively connected to the radiation electrode  2011 . The orthographic projection of the driving electrode  1011  on the second substrate  20  and the microstrip line  2013  may at least partially overlap. 
     In one embodiment, the first conductive layer  101  on the side of the first substrate  10  facing the second substrate  20  may be used to fabricate a plurality of driving electrodes  1011 , and the plurality of block-shaped driving electrodes  1011  may be uniformly distributed as an array on the first substrate  10 . The driving electrode  1011  may be connected to an external power supply terminal through at least one bias voltage signal line  1012 , and each driving electrode  1011  may independently control the liquid crystal antenna by at least one bias voltage signal line  1012 . For example, the bias voltage signal line  1012  may be configured to transmit the voltage signal provided by the external power supply terminal to the driving electrode  1011  to control the deflection electric field of the liquid crystal molecules of the liquid crystal layer  30  between the first substrate  10  and the second substrate  20 . The second conductive layer  201  on the side of the second substrate  20  facing the first substrate  10  may be used to fabricate a plurality of radiation electrodes  2011 , and may also be used to fabricate a power division network structure  2012  and a plurality of microstrip lines  2013  connected to the power division network structure  2012 . One end of the power division network structure  2012  may be connected to the signal input terminal  2014 . 
     In one embodiment, the signal input terminal  2014  may be inserted into a signal input rod  2014 A and may be fixed by a coaxial cable connector  2014 B. The signal input rod  2014 A may be used to input the microwave signal and transmit it to the power division network structure  2012  through the signal input terminal  2014 . The power division network structure  2012  may be a one-transmit-to-multiple structure. One end of the microstrip line  2013  may be connected to the power division network structure  2012 . Thus, the microwave signal input from the signal input terminal  2014  may be simultaneously transmitted to each microstrip line  2013  through the power division network structure  2012 . The orthographic projection of the driving electrode  1011  on the second substrate  20  and the microstrip line  2013  may at least partially overlap. For example, the driving electrode  1011  and the microstrip line  2013  may be in a one-to-one correspondence on the first substrate  10  and the second substrate  20  for generating the electric field that drives the deflection of the liquid crystal molecules of the liquid crystal layer  30 . By controlling the bias voltage signal line  1012  to control the voltage transmitted to the driving electrode  1011 , the intensity of the electric field formed between the microstrip line  2013  and the driving electrode  1011  may be controlled to adjust the corresponding deflection angle of the liquid crystal molecules of the liquid crystal layer  30  in the corresponding space, the dielectric constant of the liquid crystal layer  30  may be changed to realize the phase shift of the microwave signal in the liquid crystal layer  30  and to achieve the effect of changing the phase of the microwave. The other end of the microstrip line  2013  may be respectively connected to the radiation electrode  2011 . After the phase shift of the microwave signal is completed, the phase-shifted microwave signal may be transmitted to the radiation electrode  2011  through the microstrip line  2013 , and the microwave signal of the liquid crystal antenna  001  may be radiated out through the radiation electrode  2011 . 
     The first substrate  10  of this embodiment may be provided with the first conductive layer  101  only on the side facing toward the second substrate  20 , and the second substrate  20  may be provided with the second conductive layer  201  only on the side facing toward the first substrate  10 . The phaser structure, the radiation electrode  2011 , the power division network structure  2012 , and the driving electrode  1011  may be integrated in the same liquid crystal cell through the first conductive layer  101  and the second conductive layer  201 , and they may all be disposed on opposite sides of the liquid crystal layer  30  to realize the function of the liquid crystal antenna. Thus, it may be possible to avoid the introduction of the process of manufacturing conductive layers on both sides of the substrate during the manufacturing process of the liquid crystal antenna. For example, it may not be necessary to form and pattern conductive layers on both sides of a substrate, the process of forming a conductive structure on one side of the substrate and turning over to fabricate another layer of conductive structure on the other side surface, and exposure, development and etching may be omitted. Thus, it may be beneficial to reduce manufacturing difficulty and manufacturing cost, and the production efficiency, and the production yield may be improved. 
     In one embodiment, as shown in  FIG.  8   , the power division network structure  2012  in this embodiment may include a main section  2012 A and multiple branch sections  2012 B (in the figure, the configuration that a main section  2012 A is connected to two branch sections  2012 B is used as an example). One end of the main section  2012 A may be connected to the signal input terminal  2014 , the other end of the main section  2012 A may be connected to one end of the branch section  2012 B, the other end of the branch section  2012 B may be connected to the microstrip line  2013 , and the main section  2012 A may be respectively connected to a plurality of branch sections  2012 B. Each branch section  2012 B may be connected to the microstrip line  2013  respectively, thereby realizing the one-transmit-to-multiple structure of the power division network structure  2012 . Through the power division network structure  2012 , the microwave signal inputted into the signal input terminal  2014  may be transmitted to each microstrip line  2013  at the same time. 
     It is understandable that when the number of microstrip lines  2013  included in the liquid crystal antenna is larger, that is, the corresponding array of driving electrodes  1011  is larger, and the number of driving electrodes  1011  may be larger. As shown in  FIG.  8   , one branch section  2012 B of the power division network structure  2012  may be further connected to a plurality of sub-sections  2012 C to further realize the effect of one-transmit-to-multiple at one time. 
       FIG.  9    is a schematic diagram of a top view of another exemplary liquid crystal antenna according to various disclosed embodiments of the present disclosure (it is understandable that, to clearly illustrate the structure of this embodiment,  FIG.  9    is filled with transparency).  FIG.  10    is a schematic C-C′-sectional view of the exemplary liquid crystal antenna in  FIG.  9   .  FIG.  11    is a schematic structural diagram of the side of the first substrate facing toward the second substrate in  FIG.  10   .  FIG.  12    is a schematic structural view of the side of the second substrate facing toward the first substrate in  FIG.  10   .  FIG.  13    is a schematic structural view of the side of the first substrate facing away from the second substrate in  FIG.  10   . 
     As shown in  FIGS.  9 - 13   , in a liquid crystal antenna  002  provided in this embodiment, the first conductive layer  101  may include a power division network structure  2012  and a plurality of microstrip lines  2013 . The second conductive layer  201  may further includes a plurality of driving electrodes  1011 , and the driving electrodes  1011  and the radiation electrodes  2011  may be insulated from each other. The power division network structure  2012  may be connected to the signal input terminal  2014 . One end of the microstrip line  2013  may be connected to the power division network structure  2012 . The orthographic projection of the microstrip line  2013  on the second substrate  20  and the driving electrode  1011  may at least partially overlap. 
     In this embodiment, the first conductive layer  101  located on the side of the first substrate  10  facing toward the second substrate  20  may be used to fabricate the power division network structure  2012 , the plurality of microstrip lines  2013 , and one end of the power division network structure  2012  may be connected to the signal input terminal  2014 . In one embodiment, the signal input terminal  2014  may be inserted into the signal input rod  2014 A and may be fixed by the coaxial cable connector  2014 B. The signal input rod  2014 A may be used to input microwave signals and pass the signals to the power division network structure  2012  through the signal input terminal  2014 . The power division network structure  2012  may be a one-transmit-to-multiple network structure. One end of the microstrip line  2013  may be connected to the power division network structure  2012 . Therefore, through the power division network structure  2012 , the microwave signal input from the signal input terminal  2014  may be simultaneously transmitted to each microstrip line  2013 . The second conductive layer  201  on the side of the second substrate  20  facing the first substrate  10  may be used to fabricate the plurality of radiation electrodes  2011  and may also be used to fabricate the plurality of driving electrodes  1011 . The driving electrodes  1011  and the radiation electrodes  2011  may be insulated from each other. 
     In one embodiment, the driving electrodes  1011  and the radiation electrodes  2011  may both have a block structure. The driving electrodes  1011  of the block shape may be uniformly distributed on the second substrate  20  as an array, and the radiation electrodes  2011  of block shape may also be uniformly distributed on the second substrate  20  as an array. 
     Further, the second conductive layer  201  may also be used to provide a plurality of bias voltage signal lines  1012 . The driving electrodes  1011  may be connected to an external power supply terminal through at least one bias voltage signal line  1012 . Each driving electrode  1011  may be able to independently control the liquid crystal antenna through at least one bias voltage signal line  1012 . For example, the bias voltage signal line  1012  may be used to transmit the voltage signal provided by the external power supply terminal to the driving electrode  1011 , thereby controlling deflection electric field of the liquid crystal molecules of the liquid crystal layer  30  between the first substrate  10  and the second substrate  20 . The orthographic projection of the microstrip line  2013  on the second substrate  20  may at least partially overlap the driving electrode  1011 . For example, the driving electrode  1011  and the microstrip line  2013  may have one-to-one correspondence on the first substrate  10  and the second substrate  20  to generate the electric field that drives the deflection of the liquid crystal molecules of the liquid crystal layer  30 . By controlling the voltage transmitted to the driving electrode  1011  through the bias voltage signal line  1012 , the intensity of the electric field formed between the microstrip line  2013  and the driving electrode  1011  may be controlled to adjust the deflection angle of the liquid crystal molecules of the liquid crystal layer  30  in the corresponding space. Accordingly, the dielectric constant of the liquid crystal layer  30  may be changed to realize the phase shift of the microwave signals in the liquid crystal layer  30  and to achieve the effect of changing the phase of the microwave signals. After the phase shift of the microwave signal is completed, the phase shifted microwave signal may be coupled to the radiation electrodes  2011  on the second substrate  20  through the microstrip line  2013  on the first substrate  10 , and the microwave signal of the liquid crystal antenna may be radiated out through the radiation electrodes  2011 . 
     In such an embodiment, the first substrate  10  may be provided with the first conductive layer  101  only on the side facing toward the second substrate  20 , and the second substrate  20  may be provided with the second conductive layer  201  only on the side facing toward the first substrate  10 , through the conductive layer  101  and the second conductive layer  201 , the phaser structure, the radiation electrodes  2011 , the power division network structure  2012 , and the driving electrodes  1011  may be fabricated in the same liquid crystal cell, and they may be all located on the opposite sides of the liquid crystal layer  30  to realize the function of the liquid crystal antenna. Accordingly, it may be possible to avoid the introduction of the process of manufacturing conductive layers on both sides of the substrate during the manufacturing process of the liquid crystal antenna. That is, the process for forming and patterning conducive layers on both sides of one substrate may be unnecessary. The process for forming the conductive structure on one side of the substrate and then turning over the substrate to fabricate another layer of conductive structure on the other side surface, and for exposure, development and etching may be omitted. Accordingly, the manufacturing difficulty and manufacturing cost may be reduced, and the production efficiency and the product yield may be improved. 
     In one embodiment, as shown in  FIG.  11   , the power division network structure  2012  may include a main section  2012 A and a plurality of branch sections  2012 B (in the figure, the configuration that the main section  2012 A is connected to two branch sections  2012 B is as an example). One end of the main section  2012 A may be connected to the signal input terminal  2014 , the other end of the main section  2012 A may be connected to one end of the branch section  2012 B, the other end of the branch section  2012 B may be connected to the microstrip line  2013 . Through the structure that the main section  2012 A is respectively connected to the plurality of branch sections  2012 B and each branch section  2012 B is connected to the microstrip lines  2013  respectively, the one-transmit-to-multiple structure of the power division network structure  2012  may be realized. Through the power division network structure  2012 , the microwave signal inputted the signal input terminal  2014  may be transmitted to each microstrip line  2013  at the same time. 
     It is understandable that when the number of microstrip lines  2013  included in the liquid crystal antenna is larger, that is, the corresponding array of driving electrodes  1011  is larger, and the number of driving electrodes  1011  may be larger. As shown in  FIG.  8   , one branch section  2012 B of the power division network of the structure  2012  may be further connected to a plurality of sub-sections  2012 C to further realize the one-transmit-to-multiple effect of the signals. 
       FIG.  14    is a schematic diagram of another exemplary A-A′ sectional view of the exemplary liquid crystal antenna in  FIG.  1   . As shown in  FIG.  14    and referring to  FIG.  1   , in one embodiment, the liquid crystal antenna  200  may further include a third substrate  60 . The external metal layer  40  may be attached on the third substrate  60 , and the third substrate  60  and the external metal layer  40  together may be fixed on the side of the first substrate  10  facing away from the liquid crystal layer  30 . 
     In such an embodiment, after the first substrate  10  and the second substrate  20  are formed into a liquid crystal cell, the external metal layer  40 , which may be additionally fabricated on the surface of the first substrate  10  away from the liquid crystal layer  30 , may be attached on the third substrate  60 . The third substrate  60  may be configured as the carrier substrate of the external metal layer  40 , and may be fixed on the side of the first substrate  10  facing away from the liquid crystal layer  30  together with the external metal layer  40 . During the manufacturing process, the third substrate  60  may be manufactured in batches first. The fixing structure of the third substrate  60  and the external metal layer  40  may be disposed on the side of the first substrate  10  away from the liquid crystal layer  30  after the first substrate  10  and the second substrate  20  are formed into the liquid crystal cell. Accordingly, in the process of manufacturing the liquid crystal cell, it may be possible to avoid forming conductive metal layers on both sides of the first substrate  10 , thereby reducing the difficulty of the production process and improving the production efficiency. When bonding on the side of the first substrate  10  away from the liquid crystal layer  30  after forming the liquid crystal cell, the bonding accuracy requirement of the overall third substrate  60  and the external metal layer  40  may be reduced, thereby reducing the difficulty of bonding and further reducing the manufacturing cost. 
     It is understandable that the third substrate  60  of this embodiment may be one of a flexible substrate, or a rigid substrate. For example, the material of the third substrate  60  may be any rigid/hard material including glass and ceramic, or it may also be any kind of flexible material including polyimide and silicon nitride. Because the above-mentioned materials may not absorb microwave signal, that is, the insertion loss in the microwave frequency band may be relatively small, it may be beneficial to reduce the signal insertion loss and may greatly reduce loss the microwave signal during the transmission. 
     In one embodiment, after the external metal layer  40  is set, the specific positions of the third substrate  60  and the external metal layer  40  on the side of the first substrate  10  away from the liquid crystal layer  30  may not be limited. As shown in  FIG.  1    and  FIG.  14   , after the liquid crystal antenna of this embodiment is fabricated, the external metal layer  40  may be bonded and fixed on the surface of the first substrate  10  facing away from the second substrate  20 , and the third substrate  60  may be disposed on the side of the external metal layer  40  facing away from the first substrate. For example, the external metal layer  40  may be disposed between the first substrate  10  and the third substrate  60 . 
       FIG.  15    is another exemplary A-A′-sectional view of the exemplary liquid crystal antenna in in  FIG.  1   . As shown in  FIG.  15    and referring to  FIG.  1   , after the liquid crystal antenna is fabricated, the third substrate  60  may be bonded and fixed on the side of the first substrate  10  facing away from the second substrate  20 , and the external metal layer  40  may be disposed on the side of the third substrate  60  facing away from the first substrate  10 . For example, the third substrate  60  may be disposed between the first substrate  10  and the external metal layer  40 . 
     In one embodiment, when the third substrate  60  is disposed between the first substrate  10  and the external metal layer  40 , the total thickness D 1  of the third substrate  60  and the first substrate  10  after being bonded and fixed may be equal to the thickness D 2  of the second substrate  20 . 
     In one embodiment, the third substrate  60  may be bonded and fixed on the side of the first substrate  10  facing away from the second substrate  20 , and the external metal layer  40  may be disposed on the side of the third substrate  60  facing away from the first substrate  10 . That is, when the third substrate  60  is disposed between the first substrate  10  and the external metal layer  40 , the sum of the thicknesses D 1  of the third substrate  60  and the first substrate  10  after being bonded and fixed may be equal to the thickness D 2  of the second substrate  20  such that the third substrate  60  used as the carrier of the external metal layer  40  may have a sufficient strength, and on the premise of ensuring the strength, the third substrate  60  and the first substrate  10  after being bonded and fixed as a whole may be thinned as much as possible, and may have a same, or similar thickness as the second substrate  20 . Accordingly, the increase of the insertion loss of high-frequency signals caused by the excess large total thickness D 1  of the third substrate  60  and the first substrate  10  after being bonded and fixed as a whole may be avoided. Thus, the gain of the liquid crystal antenna may be increased; and the signal insertion loss may be decreased. 
     It is understandable that when the liquid crystal antenna of this embodiment needs to be bonded with a driving chip to provide driving signals, the driving chip  70  may be fixed to the flexible circuit board  80  and connected to the substrate of the liquid crystal antenna through the flexible circuit board  80 .  FIG.  16    is a schematic diagram of the structure of the liquid crystal antenna in  FIG.  14    after the driving chip is bonded. 
     As shown in  FIG.  16   , the third substrate  30  and the external metal layer  40  may extend beyond the first substrate  10  for bonding and connecting with the driving chip  70 . The liquid crystal cell formed by the first substrate  10  and the second substrate  20  may independently use the driving chip. As shown in  FIG.  16   , the first substrate  10  may extend beyond the second substrate  20  for bonding the driving chip  60  used to provide the driving signal for the liquid crystal cell. 
       FIG.  17    is a schematic diagram of the structure of the liquid crystal antenna in  FIG.  15    after the driving chip is bonded. As shown in  FIG.  17   , the third substrate  30  and the external metal layer  40  may be flush with the edge of the first substrate  10 . The flexible circuit board  80  connected with the driving chip  70  may be directly bonded to the side of the external metal layer  40  facing away from the third substrate  60 , and the liquid crystal cell formed by the first substrate  10  and the second substrate  20  may independently use the driving chip  70 . As shown in  FIG.  17   , the portion of the first substrate  10  that extends beyond the second substrate  20  may be used to bond the driving chip  70  that provides driving signals for the liquid crystal cell. 
     It should be noted that this embodiment is only an example of a structure after the liquid crystal antenna is bonded to the driving chip, including but not limited to this, and other structures may also be possible, and this embodiment will not be repeated here. 
     In some embodiments, referring to  FIG.  1   ,  FIG.  14    and  FIG.  15   , the external metal layer  40  may be a copper layer structure, and the third substrate  60  may be a printed circuit board. 
     The external metal layer  40  provided on the outside of the liquid crystal cell formed by the first substrate  10  and the second substrate  20  may be a copper layer structure, and the third substrate  60  may be a printed circuit board (PCB). The third substrate  60  and the external metal layer  40 , which are directly connected and fixed to each other, may be formed by copper coating on the printed circuit board. The circuit structure in the printed circuit board itself may directly provide a fixed potential signal to the external metal layer  40  through the circuit structure layer, and because, comparing with a third substrate of glass, the thickness of the third substrate  60  of the printed circuit board may be smaller, which may be beneficial to avoid that the total thickness of the third substrate  60  and the first substrate  10  after being bonded and fixed as a whole may be too large, which may cause the increase of the insertion loss of the high-frequency signal. Thus, the gain of the liquid crystal antenna may be increased, and the signal insertion loss may be decreased. 
     In one embodiment, as shown in  FIG.  1    and  FIG.  15   , the third substrate  60  may also be made of other materials, and may only need to satisfy that the thickness D 0  of the third substrate  60  is smaller than the thickness D 2  of the second substrate  20  such that the sum of the thickness D 1  of the third substrate  60  bonded on the first substrate  10  may meet the requirement of being similar to or equal to the thickness D 2  of the second substrate  20 , which may provide favorable conditions for the liquid crystal antenna to reduce signal insertion loss. 
       FIG.  18    is a schematic diagram of another exemplary A-A′-sectional view of the exemplary liquid crystal antenna in  FIG.  1   .  FIG.  19    is a schematic diagram of another exemplary A-A′-sectional view of the exemplary liquid crystal antenna in  FIG.  1   . As shown in  FIGS.  18 - 19    and referring to  FIG.  1   , in some embodiments, the external metal layer  40  may be made of a copper adhesive. The copper adhesive may be attached on the side of the first substrate  10  facing away from the second substrate  20 , thereby helping to reduce the difficulty of the manufacturing process. 
     As shown  FIG.  1    and  FIG.  18   , the copper adhesive may include a first adhesive layer  401 , and the first adhesive layer  401  may be doped with copper particles  402 . For example, the external metal layer  40  may have its own adhesive colloid, namely the first adhesive layer  401 , and a certain number of copper particles  402  may be doped in the first adhesive layer  401  such that the external metal layer  40  may be directly attached on the side of the first substrate  10  facing away from the second substrate  20 . At the same time, the doped copper particles  402  may also ensure the conductivity of the external metal layer  40 . In one embodiment, the first adhesive layer  401  doped with copper particles  402  may be self-adhesive and may be directly attached and fixed on the first substrate  10  to better reduce the thickness of the external metal layer  40 . Thus, the overall thickness of the liquid crystal antenna may be reduced. It can be understood that this embodiment does not specifically limit the number, particle size, and volume of the copper particles  402  doped in the first adhesive layer  401 , and it may only need to satisfy that the external metal layer  40  is a copper adhesive, and at the same time meet the viscosity and conductivity. 
     As shown in  FIG.  1    and  FIG.  19   , the copper adhesive may include a second adhesive layer  403  and a copper foil layer  404 . The second adhesive layer  403  may be disposed on the side of the copper foil layer  404  adjacent to the first substrate  10 . The second adhesive layer  403  may be bonded and fixed on the first substrate  10 , and the thickness D 3  of the second adhesive layer  403  may be less than or equal to 100 μm. For example, the external metal layer  40  may be a fixed structure of the second adhesive layer  40  and the copper foil layer  404  with self-adhesiveness. The copper foil layer  404  itself may have a relatively small thickness, and the thickness D 3  of the second adhesive layer  403  is less than or equal to 100 μm. Accordingly, the thickness of the external metal layer  40  as a whole may be reduced, and there may be no need to provide other carrier substrates to be fixed and attached to the first substrate  10 . Thus, the overall thickness of the liquid crystal antenna may be reduced. 
     The present disclosure also provides a method for forming a liquid crystal antenna.  FIG.  20    is a flowchart of an exemplary method for forming a liquid crystal antenna according to various disclosed embodiments of the present disclosure.  FIG.  21    is a schematic diagram of the structure after the first conductive layer is fabricated in the forming method of the liquid crystal antenna in  FIG.  20   .  FIG.  22    is a schematic diagram of the structure after the second conductive layer is fabricated in the forming method of a liquid crystal antenna in  FIG.  20   .  FIG.  23    is a schematic diagram of the structure after the first substrate and the second substrate are assembled into a liquid crystal cell in the forming method of a liquid crystal antenna in  FIG.  20   .  FIG.  24    is the schematic diagram of the structure after the external metal layer is formed in the forming method of a liquid crystal antenna in  FIG.  20   . The method may be used to form the present disclosed liquid crystal antenna. 
     As shown in  FIGS.  20 - 24   , and referring to  FIGS.  1 - 5   , the fabrication forming the liquid crystal antenna may include: 
     S 01 : as shown in  FIG.  21   , providing a first substrate  10  and forming a first conductive layer  101  on a side of the first substrate  10 . In one embodiment, the first conductive layer  101  may be patterned to form the structures required by the liquid crystal antenna on the first substrate  10 , and the specific structures may be referred to the description of the embodiments in  FIGS.  1 - 5   ;
 
S 02 : as shown in  FIG.  22   , providing a second substrate  20  and forming a second conductive layer  201  on a side of the second substrate  20 . In one embodiment, the second conductive layer  101  may be patterned to form the structures required by the liquid crystal antenna on the second substrate  20 . For example, the second conductive layer  201  may at least include a plurality of block-shaped radiation electrodes  2011 . The specific structures may be referred to the description of the embodiments in  FIGS.  1 - 5   ;
 
S 03 : as shown in  FIG.  23   , pairing the first substrate  10  and the second substrate  20  and disposing the liquid crystal layer  30  such that the liquid crystal layer  30  may be included between the first substrate  10  and the second substrate  20 , and the first conductive layer  101  and the second conductive layer  201  may be arranged opposite to each other. In one embodiment, the frame sealant  50  may be coated on the first substrate  10 , and then the liquid crystal may be dispersed by the liquid crystal injection technology, and the first substrate  10  and the second substrate  20  may be aligned and bonded according to the alignment marks on the second substrate  20 . After curing the frame sealant  50  to cause the first substrate  10  and the second substrate  20  to have a stable bonding, the liquid crystal cell may be obtained; and
 
S 04 : as shown in  FIG.  24   , fabricating an external metal layer  40  on the side of the first substrate  10  facing away from the liquid crystal layer  30  such that the external metal layer  40  is connected to a fixed potential.
 
     The fabrication method provided in this embodiment may be used to form the liquid crystal antenna in the above-mentioned embodiments. The figure in this embodiment only illustrates the structure that may be fabricated by the first conductive layer  101  and the second conductive layer  201  to realize the antenna function, including but not limited to this. 
     In the manufacturing method of this embodiment, only the side of the first substrate  10  facing toward the second substrate  20  may be provided with the first conductive layer  101 , and only the side of the second substrate  20  facing toward the first substrate  10  may be provided with the second conductive layer  201 . The radiation electrodes  2011  may also be disposed in the liquid crystal cell. For example, the structures may be integrated in the liquid crystal cell, and the structures used to realize the antenna function may only be disposed on one side of the same substrate. Thus, the introduction of the process of fabricating conductive layers on both sides of the substrate of the liquid crystal antenna during the fabrication of the liquid crystal antenna may be avoided. For example, in this embodiment, it may not be necessary to use the process of fabricating and patterning conductive metal layers on both sides of a substrate. Thus, the need for fabricating a conductive structure on one side of the substrate and then turning it over on the other side surface, and exposing, developing and etching may be eliminated. Accordingly, the manufacturing difficulty and manufacturing cost may be reduced, and the production efficiency and the product yield may be improved. 
     In the fabrication method of this embodiment, the external metal layer  40  may be a structure that is additionally formed on the side of the first substrate  10  facing away from the liquid crystal layer  30  after the first substrate  10  and the second substrate  20  are formed into the liquid crystal cell. Thus, in the process of fabricating the liquid crystal cell, the process for forming conductive metal layers on two sides of the first substrate  10  may be avoided. Accordingly, the difficulty of the production process may be reduced; and the production efficiency may be improved. In one embodiment, the external metal layer  40  may be disposed on the entire surface of the first substrate  10  on the side of the first substrate  10  facing away from the liquid crystal layer  30  after the liquid crystal cell is formed, and the external metal layer  40  may be connected to a fixed potential. It can be understood that the specific potential value of the external metal layer  40  connected to the fixed potential may not be specifically limited in this embodiment, and it may be selected and set according to actual requirements during specific implementation. 
     The external metal layer  40  of this embodiment may not only be used as a reflective layer, but when the microwave signal is phase-shifted, it may ensure that the microwave signal only propagates in the liquid crystal cell of the liquid crystal antenna during the phase-shifting process and prevent it from diverging outside the liquid crystal antenna. When the microwave signal is transmitted to the external metal layer  40 , the microwave signal may be reflected back through the entire surface of the external metal layer  40 . The external metal layer  40  connected to the fixed potential may also be configured to shield external signals to avoid external signals to interfere with the microwave signal to ensure the accuracy of the phase shift of the microwave signal; and the radiation gain of the antenna may be increased. Moreover, because the external metal layer  40  of this embodiment may be a whole surface structure, after being disposed on the side of the first substrate  10  facing away from the liquid crystal layer  30  after the formation of the liquid crystal cell, the requirements of the bonding accuracy may be reduced. Thus, the manufacturing difficulty may be reduced, and the manufacturing costs may be reduced. 
       FIG.  25    is a flowchart of another exemplary method for forming a liquid crystal antenna according to various disclosed embodiments of the present disclosure. As shown in  FIG.  25    and referring to  FIGS.  1 - 8   , and  FIGS.  20 - 24   , a plurality of first conductive layers  101  may be formed on a side of the first substrate  10 . The method may also include S 011 : patterning the first conductive layer  101  and using the first conductive layer  101  to make a plurality of block-shaped driving electrodes  1011 ; and forming the second conductive layer  201  on one side of the second substrate  20 . The method may further include: S 021 , patterning the second conductive layer  201  and using the second conductive layer  201  to form a plurality of radiation electrodes  2011 , a power division network structure  2012 , and a plurality of microstrip lines  2013 . The power division network structure  2012  may be connected to the signal input signal  2014 . One end of the microstrip line  2013  may be connected to the power division network structure  2012 , and the other end of the microstrip line  2013  may be connected to the radiation electrode  2011  respectively. The orthographic projection of the driving electrode  1011  on the second substrate  20  and the microstrip line  2013  may at least partially overlap. 
     In one embodiment, the first conductive layer  101  on the side of the first substrate  10  facing toward the second substrate  20  may be patterned to form the plurality of driving electrodes  1011 . The plurality of block-shaped driving electrodes  1011  may be uniformly distributed on the first substrate  10  as an array. The driving electrodes  1011  may be connected to an external power supply terminal through at least one bias voltage signal line  1012 , and each driving electrode  1011  may independently control the liquid crystal antenna by at least one bias voltage signal line  1012 . For example, the bias voltage signal line  1012  may be used to transmit the voltage signal provided by the external power supply terminal to the driving electrode  1011  to control the deflection electric field of the liquid crystal molecules of the liquid crystal layer  30  between the first substrate  10  and the second substrate  20 . The second conductive layer  201  on the side of the second substrate  20  facing toward the first substrate  10  may be patterned to fabricate a plurality of radiation electrodes  2011 , a power division network structure  2012 , and a plurality of microstrip lines  2013  connected to the power division network structure  2012 . One end of the power division network structure  2012  may be connected to the signal input terminal  2014 . In one embodiment, the signal input terminal  2014  may be inserted into the signal input rod  2014 A, and fixed by the coaxial cable connector  2014 B. The signal input rod  2014 A may be used to input the microwave signal and transmitted the microwave signal to the power division network structure  2012  through the signal input terminal  2014 . The power division network structure  2012  may be a one-transmit-to-multiple network structure. One end of the microstrip line  2013  may be connected to the power division network structure  2012 . Therefore, through the power division network structure  2012 , the microwave signal input by the signal input terminal  2014  may be simultaneously transmitted to each microstrip line  2013 . The orthographic projection of the driving electrode  1011  on the second substrate  20  and the microstrip line  2013  may at least partially overlap. For example, the driving electrode  1011  and the microstrip line  2013  may be in a one-to-one correspondence on the first substrate  10  and the second substrate  20  for generating the electric field that drives the deflection of the liquid crystal molecules of the liquid crystal layer  30 . By controlling the voltage signal transmitted to the driving electrode  1011  through the bias voltage signal line  1012 , the intensity of the electric field formed between the microstrip line  2013  and the driving electrode  1011  may be controlled to adjust the deflection angle of the liquid crystal molecules of the liquid crystal layer  30  in the corresponding space; and the dielectric constant of the liquid crystal layer  30  may be changed to realize the phase shift of the microwave signal in the liquid crystal layer  30  and achieve the effect of changing the phase of the microwave. The other end of the microstrip line  2013  may be respectively connected to the radiation electrodes  2011 . After the phase shift of the microwave signal is completed, the phase-shifted microwave signal may be transmitted to the radiation electrode  2011  through the microstrip line  2013 , and the microwave signal of the liquid crystal antenna may be radiated out through the radiation electrodes  2011 . In one embodiment, the microstrip line may be provided with a common voltage. 
       FIG.  26    is a flowchart of another exemplary fabrication method of a liquid crystal antenna according to various disclosed embodiments of the present disclosure.  FIG.  27    is the schematic diagram of the structure after the first conductive layer is fabricated in the method provided in  FIG.  26   .  FIG.  28    is the schematic diagram of the structure after the second conductive layer is fabricated in the method provided in  FIG.  26   .  FIG.  29    is the schematic diagram of the structure after the first substrate and the second substrate are paired in the method provided in  FIG.  26   .  FIG.  30    is the structure diagram of the structure after the external metal layer is fabricated in the method provided in  FIG.  26   . The fabrication method of the liquid crystal antenna may be used to fabricate the liquid crystal antenna provided in the embodiment of  FIGS.  9 - 13   . 
     As shown in  FIGS.  26 - 30    and referring to  FIGS.  9 - 13   , the fabrication method may include: 
     S 11 : providing a first substrate  10  and forming a first conductive layer  101  on a side of the first substrate  10 ;
 
S 111 : as shown in  FIG.  27   , performing a patterning process on the first conductive layer  101 , and using the first conductive layer  101  to form a power division network structure  2012  and a plurality of microstrip lines  2013 . The details may be referred to the description of the embodiments in  FIGS.  9 - 13   ;
 
S 12 : providing a second substrate  20  and forming a second conductive layer  201  on a side of the second substrate  20 ;
 
S 121 : as shown in  FIG.  28   , performing a patterning process on the second conductive layer  201 , and using the second conductive layer  201  to form a plurality of block-shaped radiation electrodes  2011  and a plurality of block-shaped driving electrodes  1011 . The driving electrodes  1011  and the radiation electrodes  2011  may be insulated from each other. The power division network structure  2012  may be connected to the signal input terminal  2014 , and one end of the microstrip line  2013  may be connected to the power division network structure  2012 . The details may be referred to the description of the embodiments in  FIGS.  9 - 13   ;
 
S 13 : as shown in  FIG.  29   , pairing the first substrate  10  and the second substrate  20 , and disposing the liquid crystal layer  30  such that the liquid crystal layer  30  may be included between the first substrate  10  and the second substrate  20 , and the first conductive layer  101  and the second conductive layer  201  may be arranged opposite to each other. In one embodiment, the frame sealant  50  may be coated on the first substrate  10 , and then the liquid crystal may be dispersed by the liquid crystal injection technology, and the first substrate  10  and the second substrate  20  may be aligned and attached according to the alignment marks on the second substrate  20 . Then, the frame sealant  50  may be cured such that the first substrate  10  and the second substrate  20  may be attached stably to obtain a liquid crystal cell. The orthographic projection of the microstrip line  2013  on the second substrate  20  and the driving electrode  1011  may at least partially overlap; and
 
S 14 : as shown in  FIG.  30   , forming an external metal layer  40  on the side of the first substrate  10  facing away from the liquid crystal layer  30  such that the external metal layer  40  may be connected to a fixed potential.
 
     In one embodiment, the first conductive layer  101  on the side of the first substrate  10  facing toward the second substrate  20  may be patterned to form a power division network structure  2012 , and a plurality of microstrip lines  2013 . One end of the power division network structure  2012  may be connected to the signal input terminal  2014 . In one embodiment, the signal input terminal  2014  may be inserted into a signal input rod  2014 A and fixed by a coaxial cable connector  2014 B. The signal input rod  2014 A may be used to input microwave signal and the microwave signal may be transmitted to the power division network structure  2012  through the signal input terminal  2014 . The power division network structure  2012  may be a one-transmit-to-multiple network structure. One end of the microstrip line  2013  may be connected to the power division network structure  2012 . Thus, through the power division network structure  2012 , the microwave signal input from the signal input terminal  2014  may be simultaneously transmitted to each microstrip line  2013 . 
     The second conductive layer  201  on the side of the second substrate  20  facing toward the first substrate  10  may be patterned to fabricate a plurality of radiation electrodes  2011  and a plurality of driving electrodes  1011 . The driving electrodes  1011  and the radiation electrodes  2011  may be insulated from each other. In one embodiment, the driving electrodes  1011  and the radiation electrodes  2011  may both have a block structure, the driving electrodes  1011  of the block shape may be uniformly distributed on the second substrate  20  in as an array, and the radiation electrodes  2011  of the block shape may also be uniformly distributed on the second substrate  20  in as an array. Further, the second conductive layer  201  may also be used to provide a plurality of bias voltage signal lines  1012 . The driving electrode  1011  may be connected to an external power supply terminal through at least one bias voltage signal line  1012 . Each driving electrode  1011  may independently control the liquid crystal antenna by at least one bias voltage signal line  1012 . For example, the bias voltage signal line  1012  may be used to transmit the voltage signal provided by the external power supply terminal to the drive electrode  1011  to control the electric field for deflecting the liquid crystal molecules of the liquid crystal layer  30  between the first substrate  10  and the second substrate  20 . The orthographic projection of the microstrip line  2013  on the second substrate  20  may at least partially overlap the driving electrode  1011 . For example, the driving electrode  1011  and the microstrip line  2013  may have a one-to-one correspondence on the first substrate  10  and the second substrate  20  for generating the electric field that drives the deflection of the liquid crystal molecules of the liquid crystal layer  30 . By controlling the voltage transmitted to the driving electrode  1011  through the bias voltage signal line  1012 , the intensity of the electric field formed between the microstrip line  2013  and the driving electrode  1011  may be controlled to adjust the deflection angle of the liquid crystal molecules of the liquid crystal layer  30  in the corresponding space. Accordingly, the dielectric constant of the liquid crystal layer  30  may be changed to realize the phase shift of the microwave signal in the liquid crystal layer  30  and to achieve the effect of changing the phase of the microwave. After the phase shift of the microwave signal is completed, the phase shifted microwave signal may be coupled to the radiation electrode  2011  on the second substrate  20  through the microstrip line  2013  on the first substrate  10 , and the microwave signal of the liquid crystal antenna may be radiated out through the radiation electrodes  2011 . 
       FIG.  31    is a flowchart of another exemplary fabrication method of a liquid crystal antenna according to various disclosed embodiments of the present disclosure.  FIG.  32    is the schematic diagram of the structure after an external metal layer of a whole surface structure is fabricated in the method provided in  FIG.  31   .  FIG.  33    is the schematic diagram of the structure after the external metal layer is fabricated in the method provided in  FIG.  31   .  FIG.  34    is the schematic diagram of another structure after the external metal layer is formed in the method provided in  FIG.  31   . The fabrication method of the liquid crystal antenna may be used to fabricate the liquid crystal antenna provided in the embodiment of  FIGS.  14 - 15   . 
     As shown in  FIGS.  31 - 34    and referring to  FIGS.  1 - 8   ,  FIGS.  14 - 15   , and  FIGS.  21 - 23   , in some embodiments, the method for forming a liquid crystal antenna may include: 
     S 21 : providing a first substrate  10  and forming a first conductive layer  101  on a side of the first substrate  10 ;
 
S 211 : as shown in  FIG.  21   , performing a patterning process on the first conductive layer  101 , and using the first conductive layer  101  to fabricate a plurality of block-shaped driving electrodes  1011 ;
 
S 22 : providing a second substrate  20  and forming a second conductive layer  201  on s side of the second substrate  20 ;
 
S 221 : as shown in  FIG.  22   , performing a patterning process on the second conductive layer  201  and using the second conductive layer  201  to fabricate a plurality of radiation electrodes  2011 , a power division network structure  2012 , and a plurality of microstrip lines  2013 . The power division network structure  2012  may be connected to the provided signal input terminal  2014 , one end of the microstrip line  2013  may be connected to the power division network structure  2012 , and the other end of the microstrip line  2013  may be connected to the radiation electrode  2011 , respectively;
 
S 23 : as shown in  FIG.  23   , pairing the first substrate  10  and the second substrate  20 , and disposing the liquid crystal layer  30  such that the liquid crystal layer  30  may be located between the first substrate  10  and the second substrate  20 , and the first conductive layer  101  and the second conductive layer  201  may be arranged opposite to each other. In one embodiment, the frame sealant  50  may be coated on the first substrate  10 , and then the liquid crystal may be dispersed by the liquid crystal injection technology, and the first substrate  10  and the second substrate  20  may be aligned and bonded according to the alignment marks on the second substrate  20 . Then, the frame sealant  50  may be cured such that the first substrate  10  and the second substrate  20  may be attached stably to obtain a liquid crystal cell. The orthographic projection of the driving electrode  1011  on the second substrate  20  and the microstrip line  2013  may at least partially overlap;
 
S 24 : as shown in  FIG.  32   , providing a third substrate  60  and forming an external metal layer  40  of a whole surface structure on a side of the third substrate  60 ; and
 
S 25 : as shown in  FIGS.  33 - 34   , attaching the third substrate  60  and the external metal layer  40  together to the side of the first substrate  10  facing away from the liquid crystal layer  30  such that the external metal layer  40  may be connected to a fixed potential.
 
     In the manufacturing method provided in this embodiment, after the first substrate  10  and the second substrate  20  are formed into the liquid crystal cell, the external metal layer  40 , which may be additionally manufactured on the side of the first substrate  10  facing away from the liquid crystal layer  30 , may be attached on the third substrate  60 . The third substrate  60  may be configured as the carrier substrate of the external metal layer  40  and may be fixed on the side of the first substrate  10  facing away from the liquid crystal layer  30  together with the external metal layer  40 . During the manufacturing process, the fixing structure of the third substrate  60  and the external metal layer  40  (as shown in  FIG.  32   ) may be formed in batches first. Then, the fixing structure of the third substrate  60  and the external metal layer  40  may be directly disposed on the side of the first substrate  10  facing away from the liquid crystal layer  30  after the first substrate  10  and the second substrate  20  are formed into a liquid crystal cell. Accordingly, it may be possible to avoid forming conductive metal layers on two sides of the first substrate  10 , the difficulty of the production process may be reduced, and the production efficiency may be improved. When the fixing structure of the third substrate  60  and the external metal layer  40  is fixed on the side of the first substrate  10  facing away from the liquid crystal layer  30  after the liquid crystal cell is formed, the overall bonding accuracy requirements of the third substrate  60  and the external metal layer  40  may be reduced, and the production costs may be further reduced. 
     In one embodiment, as shown in  FIG.  33   , after the liquid crystal antenna of this embodiment is fabricated, the external metal layer  40  may be attached and fixed on the surface of the first substrate  10  facing away from the second substrate  20 , and the third substrate  60  may be located on the side of the external metal layer  40  away from the first substrate  10 . For example, the external metal layer  40  may be located between the first substrate  10  and the third substrate  60 . 
     In one embodiment, as shown in  FIG.  34   , after the liquid crystal antenna of this embodiment is fabricated, the third substrate  60  may be bonded and fixed on the surface of the first substrate  10  facing away from the second substrate  20 , and the external metal layer  40  may be located on the side of the third substrate  60  facing away from the first substrate  10 . For example, the third substrate  60  may be located between the first substrate  10  and the external metal layer  40 . It can be understood that this embodiment does not limit the specific positions of the third substrate  60  and the external metal layer  40  on the side of the first substrate  10  facing away from the liquid crystal layer  30  after the external metal layer  40  is disposed. 
       FIG.  35    illustrates a flowchart of another exemplary fabrication method of a liquid crystal antenna according to various disclosed embodiments of the present disclosure.  FIG.  36    is a schematic structural diagram of the external metal layer provided in the fabrication method of the liquid crystal antenna in  FIG.  35   .  FIG.  37    is a schematic structural diagram of the liquid crystal antenna after the external metal layer is formed by the method in in  FIG.  36   . FIG.  38  is another schematic diagram of the external metal layer provided in the fabrication method of the liquid crystal antenna in  FIG.  35   .  FIG.  39    is a schematic diagram of the liquid crystal antenna after the external metal layer in  FIG.  38    is formed. The method may be used to form the liquid crystal antenna of the embodiment of  FIG.  18    and  FIG.  19   . 
     As shown in  FIGS.  35 - 39    and referring to  FIGS.  1 - 8   ,  FIGS.  18 - 19    and  FIGS.  21 - 23   , the method for forming the liquid crystal antenna may include: 
     S 31 : providing a first substrate  10 , and forming a first conductive layer  101  on a side of the first substrate  10 ;
 
S 311 : referring to  FIG.  21   , performing a patterning process on the first conductive layer  101 , and using the first conductive layer  101  to fabricate a plurality of block-shaped driving electrodes  1011 ;
 
S 32 : providing a second substrate  20 , and forming a second conductive layer  201  on a side of the second substrate  20 ;
 
S 321 : referring to  FIG.  22   , performing a patterning process on the second conductive layer  201 , and using the second conductive layer  201  to fabricate a plurality of radiation electrodes  2011 , a power division network structure  2012 , and a plurality of microstrip lines  2013 . The power division network structure  2012  may be connected to the provided signal input terminal  2014 . One end of the microstrip line  2013  may be connected to the power division network structure  2012 , and the other end of the microstrip line  2013  may be connected to the radiation electrode  2011 , respectively;
 
S 33 : pairing the first substrate  10  and the second substrate  20 , and disposing the liquid crystal layer  30  such that the liquid crystal layer  30  may be included between the first substrate  10  and the second substrate  20 , and the first conductive layer  101  and the second conductive layer  201  may be arranged opposite to each other. In one embodiment, the frame sealant  50  may be coated on the first substrate  10 , and then the liquid crystal may be dispersed by the liquid crystal injection technology, and the first substrate  10  and the second substrate  20  may be aligned and bonded according to the alignment marks on the second substrate  20 . Then, the frame sealant  50  may be cured such that the first substrate  10  and the second substrate  20  may be attached stably to obtain a liquid crystal cell. The orthographic projection of the driving electrode  1011  on the second substrate  20  and the micro-ribbon line structure  2013  may at least partially overlap;
 
S 34 : providing a copper adhesive as the external metal layer  40 . As shown in  FIG.  36   , the copper adhesive may include a first adhesive layer  401 , and the first adhesive layer  401  may be doped with copper particles  402 . As shown in  FIG.  38   , the copper adhesive may include a second adhesive layer  403  and a copper foil layer  404 , and the thickness of the second adhesive layer  403  may be less than or equal to  100  um; and
 
     S 35 : as shown in  FIG.  37    and  FIG.  39   , directly attaching the external metal layer  40  of the copper adhesive on the surface of the first substrate  10  facing away from the liquid crystal layer  30  such that the external metal layer  40  may be connected to a fixed potential. 
     The external metal layer  40  of this embodiment may be made of a copper adhesive. The copper adhesive may be a structure that includes a first adhesive layer  401  doped with copper particles  402 . For example, the external metal layer  40  may include a self-adhesive glue, i.e., the first adhesive layer  401 , and a certain amount of copper particles  402  may be doped in the first adhesive layer  401 . When the external metal layer  40  is directly attached on the surface of the first substrate  10  away from the second substrate  20 , the doped copper particles  402  may also ensure the conductivity of the external metal layer  40 . In one embodiment, the first adhesive layer  401  doped with copper particles  402  may be self-adhesive and may be directly attached and fixed on the first substrate  10  to better reduce the thickness of the external metal layer  40 . Accordingly, the overall thickness of the liquid crystal antenna may be reduced. It can be understood that this embodiment does not specifically limit the number, particle size, and volume of the copper particles  402  doped in the first adhesive layer  401 , and it may only need to satisfy that the external metal layer  40  is a copper adhesive, and at the same time, to meet the viscosity and conductivity. 
     The copper adhesive may also be a structure including a second adhesive layer  403  and a copper foil layer  404 . The thickness of the second adhesive layer  403  may be less than or equal to 100 μm. For example, the external metal layer  40  may be a fixed structure having a self-adhesive second adhesive layer  40  and a copper foil layer  404 . The thickness of the copper foil layer  404  itself may be relatively thin, and the thickness of the second adhesive layer  403  may be less than or equal to 100 μm. Thus, the thickness of the external metal layer  40  as a whole may be reduced, and there may be no need to provide other carrier substrate to be attached and fixed with the first substrate  10 . Accordingly, the overall thickness of the liquid crystal antenna may be further reduced. In one embodiment, the external metal layer  40  of copper adhesive may be directly attached to the surface of the first substrate  10  away from the liquid crystal layer  30 , and the process difficulty may be reduced, and the process efficiency may be improved. 
       FIG.  40    is a schematic diagram of a top view of another exemplary liquid crystal antenna according to various disclosed embodiments of the present disclosure (it is understandable that, to clearly illustrate the structure of this embodiment,  FIG.  40    is filled with transparency).  FIG.  41    is a D-D′-sectional view of the exemplary liquid crystal antenna in  FIG.  40   .  FIG.  42    is a schematic structural diagram of the surface of the fourth substrate facing toward the fifth substrate in  FIG.  41   .  FIG.  43    is a schematic diagram view of the surface of the fifth substrate facing toward the fourth substrate in  41 .  FIG.  44    is a schematic structural view of the surface of the fourth substrate facing away from the fifth substrate in  FIG.  41   . 
     As shown in  FIGS.  40 - 44   , a liquid crystal antenna  003  provided in this embodiment may include a plurality of spliced antenna units  00 . Each antenna unit  00  may include a fourth substrate  901  and a fifth substrate  902  disposed oppositely, and a second liquid crystal layer  903  disposed between the fourth substrate  901  and the fifth substrate  902 . A third conductive layer  9011  may be disposed on the side of the fourth substrate  901  facing the fifth substrate  902 ; a fourth conductive layer  9021  may be disposed on the side of the fifth substrate  902  facing toward the fourth substrate  901 , and the fourth conductive layer  9021  may include at least a plurality of second radiation electrodes  90211 . Further, a second external metal layer  904  may be disposed the side of the fourth substrate  901  facing away from the second liquid crystal layer  903 , and the second external metal layer  904  may be connected to a fixed potential. The second external metal layers  904  corresponding to each antenna unit  00  may be electrically connected. 
     Specifically, the liquid crystal antenna  003  provided in this embodiment may include a plurality of spliced antenna units  00 . In one embodiment, the plurality of antenna units  00  may be arranged as an array. For example, the liquid crystal antenna  003  illustrated in  FIG.  40    may be a 2×2 (representing two antenna units  00  in the horizontal direction and two antenna elements  00  in the vertical direction) array spliced structure. It can be understood that the number of multiple spliced antenna units  00  included in the liquid crystal antenna  003  is not limited, other numbers of spliced antenna units  00  may also be included, such as an 8×8 array or a 16×16 array may be used to splice the antenna units  00  together to form the liquid crystal antenna  003 . 
     Each antenna unit  00  in this embodiment may be understood as one unit of a liquid crystal antenna structure, and multiple antenna units  00  may be spliced together (disposed together). Further, two adjacent antenna units  00  may be spliced and fixed together using the adhesive  01  disposed between (or a structure with an adhesive property such as double-sided tape) and the adjacent antenna units  00  may also be spliced and fixed in other ways, which is not specifically limited in this embodiment. For the disclosed embodiments, on the one hand, the process for forming a large area of conductive structure of the antenna on a substrate may be avoided, and the difficulty of the manufacturing process may be reduced to a certain extent and the product yield may be improved. On the other hand, the design of the liquid crystal antenna  003  of the array structure formed by splicing may become standardized and may adapt to different requirements of the antenna array. 
     Each antenna unit  00  of this embodiment may include a fourth substrate  901  and a fifth substrate  902  that are opposed to each other, and a second liquid crystal layer  903  may be disposed between the fourth substrate  901  and the fifth substrate  902 . The side of the fourth substrate  901  facing toward the fifth substrate  902  may include a third conductive layer  9011 , and the third conductive layer  9011  may be used to provide a portion of the structures that realize the antenna function, such as a phaser. The side of the fifth substrate  902  facing toward the fourth substrate  901  may include a fourth conductive layer  9021 . The fourth conductive layer  9021  may include at least a plurality of second radiation electrodes  90211 , and the second radiation electrodes  90211  may be used to radiate out the microwave signal of the liquid crystal antenna  003 . In one embodiment, the materials of the third conductive layer  9011  and the fourth conductive layer  9021  may not be specifically limited and may only need to be able to conduct electricity. For example, the materials of the third conductive layer  9011  and the fourth conductive layer  9021  may be metal conductive materials, such as copper, etc. 
     In one embodiment, the third conductive layer  9011  of this embodiment may include a second driving electrode  90111  and a second bias voltage signal line  90112 . The second driving electrode  90111  may have a block structure as shown in  FIG.  42   . The second driving electrode  90111  may be connected to an external power supply terminal through at least one second bias voltage signal line  90112  (not shown in the figure, for example, a voltage signal may be provided by bonding a driving chip). Each second driving electrode  90111  may independently control the liquid crystal antenna through at least one second bias voltage signal line  90112 . For example, the second bias voltage signal line  90112  may be used to transmit the voltage signal provided by the external power supply terminal to the second drive electrode  90111  to control the deflection electric field of the liquid crystal molecules of the second liquid crystal layer  903  between the fourth substrate  901  and the fifth substrate  902 . 
     Further, in one embodiment, as shown in  FIG.  42   , the plurality of second driving electrodes  90111  may be uniformly distributed on the fourth substrate  901  as an array. It can be understood that the specific number, distribution, and material of the second driving electrodes  90111  on the side of the fourth substrate  901  facing toward the fifth substrate  902  may be set by those skilled in the art according to actual conditions, and there may be no specific limitation. The figure in this embodiment only exemplarily shows the wiring structure of each second bias voltage signal line  90112 , which includes but is not limited to this, and may also be other layout structures, which is not limited in this embodiment. 
     In one embodiment, the fourth conductive layer  9021  of the fifth substrate  902  of this embodiment may include a second power division network structure  90212  and a plurality of phaser structures connected to the power division network structure  90212  in addition to a plurality of second radiation electrodes  90211 . Further, each second phaser structure may have a one-to-one correspondence with the second driving electrode  90111  on the fourth substrate  901  to generate the deflection electric field of the liquid crystal molecules of the second liquid crystal layer  903 . By controlling the voltage transmitted to the second drive electrode  90111  through the second bias voltage signal line  90112 , the intensity of the electric field formed between the second phaser structure and the second driving electrode  90111  may be controlled to adjust the deflection angle of the liquid crystal molecules of the second liquid crystal layer  903  in the corresponding space to change the dielectric constant of the second liquid crystal layer  903 . Accordingly, the phase shift of the microwave signal in the second liquid crystal layer  903  may be realized to achieve the effect of changing the phase of the microwave. 
     The second power division network structure  90212  of this embodiment may be configured to input microwave signals to each second phaser structure. The second phaser structure may be a second microstrip line  90213 . The shape of the second microstrip line  90213  may be zigzag (as shown in  FIG.  43   ) or spiral (not shown in the figure) or other structures. The microwave signal transmitted by the second power division network structure  90212  may be further transmitted to each second phaser structure. The zigzag or spiral-shaped second phaser structure may increase the direct facing area between the second phase shifter structure and the second driving electrode  90111  to ensure that as many liquid crystal molecules as possible in the second liquid crystal layer  903  are in the electric field formed by the second phaser structure and the second driving electrode  90111 . Accordingly, the inversion efficiency of the liquid crystal molecules may be improved. This embodiment does not limit the shape and distribution of the second phaser structure and may only need to be able to realize the transmission of microwave signals. It can be understood that, to clearly illustrate the structure of this embodiment,  FIG.  43    only illustrates the structure of 16 second phasers on the fifth substrate  902 , but it is not limited to this number. In specific implementation, the number of the second phaser structures may be arrayed according to actual needs. 
     In one embodiment, the second radiation electrodes  90211  may be connected to the second phaser structure. After the phase shift of the microwave signal is completed, the phase shifted microwave signal may be transmitted to the second radiation electrodes  90211  through the phaser structure, and through the second radiation electrodes  90211 , the microwave signal of each antenna unit  00  of the liquid crystal antenna  003  may be radiated out. 
     This embodiment only exemplifies the structures that may be included in the third conductive layer  9011  and the fourth conductive layer  9021  of the antenna unit  00  and may realize the antenna function, including but not limited to this. The third conductive layer  9011  on the fourth substrate  901  and the fourth conductive layer  9021  on the fifth substrate  902  may also include other structures that may realize the antenna function, as long as the third conductive layer  9011  may be only disposed on the side of the fourth substrate  901  facing toward the fifth substrate  902 , the fourth conductive layer  9012  may be only disposed on the side of the fifth substrate  902  facing toward the fourth substrate  901 , and the second radiation electrode  90211  may also be disposed in the liquid crystal cell. For example, such structures may be integrated in a liquid crystal cell. The structures used to realize the antenna function may only be disposed on one side surface of the same substrate to avoid the introduction of the process of manufacturing conductive layers on both sides of the substrate during the manufacturing process of the liquid crystal antenna  003 . For example, the present embodiment may not need to use the process of fabricating and patterning conductive metal layers on both sides of a substrate and may reduce the need to fabricate a conductive structure on one side of the substrate and then turn it over to fabricate another conductive structure on the other side, and expose, develop, and etch. Thus, the manufacturing difficulty and the manufacturing cost may be reduced, and the production efficiency and the product yield may be improved. 
     In one embodiment, a second external metal layer  904  may be disposed the side of the fourth substrate  901  facing away from the second liquid crystal layer  903 . The second external metal layer  904  may be connected to a fixed potential. The optional second external metal layer  904  may be a viscous connector (not filled in  FIG.  41   ) fixed on the fourth substrate  901 . The fixed potential of the optional second external metal layer  904  may also be provided by a bonded driving chip, which is not described in detail in this embodiment. It can be understood that the second external metal layer  904  may refer to a structure additionally formed on a side of the fourth substrate  901  away from the second liquid crystal layer  903  after the fourth substrate  901  and the fifth substrate  902  of each antenna unit  00  are formed into a liquid crystal cell. 
     Thus, it may avoid disposing conductive metal layers on both sides of the fourth substrate  901  during the process of manufacturing the liquid crystal cell. Accordingly, the difficulty of the production process may be reduced, and the production efficiency may be improved. In one embodiment, the second external metal layer  904  may be disposed on the entire surface of the fourth substrate  901  on the side away from the second liquid crystal layer  903  after the liquid crystal cell is formed, and the second external metal layer  904  may be connected to a fixed potential. It can be understood that the specific potential value of the second external metal layer  904  connected to the fixed potential may not be specifically limited in this embodiment, and it may be selected and set according to actual requirements during specific implementation. 
     The second external metal layer  904  of this embodiment may not only be used as a reflective layer, but when the phase the microwave signal is shifted, it may ensure that the microwave signal only propagates in the liquid crystal cell of each antenna unit  00  during the phase shifting process, and may avoid to disperse to the outside of the liquid crystal antenna. When the microwave signal is transmitted to the second external metal layer  904 , the microwave signal may be reflected back through the second external metal layer  904  of the entire surface structure. The second external metal layer  904  connected to with the fixed potential may also be used to shield external signals to avoid interference of external signals to microwave signals, thereby ensuring the accuracy of phase shifting of microwave signals. Thus, the radiation gain of the antenna may be increased. Because the second external metal layer  904  of this embodiment may be a whole surface structure, when the second external metal layer  904  is disposed on the side of the fourth substrate  901  away from the second liquid crystal layer  903  after the formation of the liquid crystal cell, the requirements for the bonding accuracy may be reduced, and the manufacturing difficulty and the manufacturing costs may be further reduced. 
     In addition, the second external metal layer  904  corresponding to each antenna unit  00  of this embodiment may be electrically connected. Thus, the second external metal layers  904  may jointly provide a fixed potential signal to each corresponding antenna unit  00  of the liquid crystal antenna  003 ; and the wiring may be simplified 
       FIG.  45    is a schematic diagram of another exemplary D-D′-sectional view of the exemplary liquid crystal antenna in  FIG.  40   .  FIG.  46    is structural view of the side of the fourth substrate in  FIG.  45    facing away from the fifth substrate (it is understandable that, to clearly illustrate the structure of this embodiment,  FIG.  46    is filled with transparency). 
     As shown in  FIGS.  45 - 46    and referring to  FIG.  40   , the second external metal layer  904  corresponding to each antenna unit  00  of the liquid crystal antenna  003  of this embodiment may also be connected as one whole structure. For example, the second external metal layers  904  corresponding to each antenna unit  00  may be connected to each other to form a whole surface structure such that a plurality of second external metal layers  904  connected as a whole surface structure to form a carrier structure. The carrier structure may be used to carry a plurality of spliced antenna units  00 . Thus, the manufacturing process of the second external metal layers  904  may be simplified. 
     It should be noted that the fourth substrate  901 , the fifth substrate  902 , and the second liquid crystal layer  903  of each antenna unit  00  of this embodiment may form a liquid crystal cell. The specific process of forming the liquid crystal cell may be set by those skilled in the art according to the actual situation; and there is no limitation here. For example, the second frame sealant  905  may be coated on the fourth substrate  901 , and then liquid crystal may be dispersed by the liquid crystal injection technology, and the fourth substrate  901  and the fifth substrate  902  may be aligned and bonded according to the alignment marks on the fifth substrate  902 . The second frame sealant  905  may be cured to stably adhere to the fourth substrate  901  and the fifth substrate  902 , and the liquid crystal cell may be obtained. The materials of the fourth substrate  901  and the fifth substrate  902  may also be set by those skilled in the art according to the actual situation, which is not limited here. Exemplarily, the fourth substrate  901  and the fifth substrate  902  may be any rigid material, such as glass and ceramics, or may be any flexible material, such as polyimide and silicon nitride. Because such materials may not absorb microwave signals, the insertion loss in the microwave frequency band may be substantially small, the signal insertion loss may be reduced, and the loss of microwave signals in the transmission process may be significantly reduced. 
     It should be further explained that this embodiment only exemplarily illustrates the structure of the antenna units  00  of the liquid crystal antenna  003 , but it is not limited to this, and may also include other structures, such as the alignment layer, etc. between the fourth substrate  901  and the fifth substrate  902 . The structures may be specifically understood with reference to the structure of the liquid crystal antenna in the related art, which is not repeated in this embodiment. This embodiment is only an example of the structures that the third conductive layer  9011  and the fourth conductive layer  9021  may be provided, including but not limited to the above-mentioned structures and working principle. In specific implementation, it may be set according to the required functions of the liquid crystal antenna; and the examples are not repeated here. 
       FIG.  47    is a schematic diagram of another exemplary D-D′-sectional view of the exemplary liquid crystal antenna in  FIG.  40   .  FIG.  48    is a schematic diagram of another exemplary D-D′-sectional view of the exemplary liquid crystal antenna in  FIG.  40   . 
     As shown in  FIGS.  47 - 48   , and referring to  FIG.  40   , the present disclosed liquid crystal antenna  003  may also include a sixth substrate  906 . In a direction X parallel to the plane where the sixth substrate  906  is located, a plurality of antenna units  00  may all be disposed on the same sixth substrate  906 . The second external metal layer  904  may be bonded and fixed on the sixth substrate  906 . The sixth substrate  906  may be located on a side of the fourth substrate  901  facing away from the fifth substrate  902 . 
     In one embodiment, after the fourth substrate  901  and the fifth substrate  902  are formed into a liquid crystal cell, the second external metal layer  904 , which is additionally fabricated on the surface of the fourth substrate  901  away from the second liquid crystal layer  903 , may be attached on the sixth substrate  906 . The sixth substrate  906  may be configured as the carrier substrate for the plurality of second external metal layers  904 , and may be fixed on the side of the fourth substrate  901  away from the fifth substrate  902  together with the second external metal layer  904 . 
     In the fabrication process, a large-area sixth substrate  906  and a plurality of second external metal layers  904  connected as a whole may be fabricated to form a fixed structure firstly, and then, after the fourth substrate  901  and the fifth substrate  902  are formed into a liquid crystal cell, the respective antenna units  00  may be collectively arranged on the fixing structure formed by the same sixth substrate  906  and the plurality of second external metal layers  904  connected as a whole. Accordingly, the same sixth substrate  906  may be used as a carrier substrate for the plurality of antenna units  00 , and it may be possible to realize the splicing and fixing of the plurality of antenna units  00  on the same sixth substrate  906 . Thus, the process for forming conductive metal layers both sides of the fourth substrate  901  may be avoided, thereby further reducing the difficulty of the production process, and improving production efficiency at the same time. It may also reduce requirements of the bonding accuracy of the fixing structure formed by the same sixth substrate  906  and the plurality of second external metal layers  904  connected as a whole. Thus, the difficulty of bonding and the manufacturing cost may be further reduced. 
     It is understandable that the sixth substrate  906  in this embodiment may be one of a flexible substrate or a rigid substrate. For example, the material of the sixth substrate  906  may be any rigid/hard material, such as glass and ceramic, or it may also be any kind of flexible material, such as polyimide and silicon nitride. Because the above-mentioned materials may not absorb microwave signals, the insertion loss in the microwave frequency band may be substantially small. Thus, the signal insertion loss may be reduced, and the microwave signal loss during the transmission may be significantly reduced. 
     This embodiment does not limit the specific positions of the sixth substrate  906  and the second external metal layer  904  on the side of the fourth substrate  901  away from the second liquid crystal layer  903  after the second external metal layer  904  is disposed. In some embodiments, as shown in  FIG.  40    and  FIG.  47   , after the liquid crystal antenna  003  of this embodiment is fabricated, the second external metal layer  904  may be disposed on the side of the sixth substrate  906  adjacent to the fourth substrate  901 . For example, the second external metal layer  904  may be bonded and fixed on the fourth substrate  901 . In other embodiments, as shown in  FIG.  40    and  FIG.  48   , after the liquid crystal antenna  003  of this embodiment is fabricated, the second external metal layer  904  may be disposed on the side of the sixth substrate  906  away from the fourth substrate  901 . For example, the sixth substrate  906  and the respective fourth substrate  901  may be bonded and fixed. 
     In one embodiment, when the sixth substrate  906  is disposed between the fourth substrate  901  and the second external metal layer  904 , the total thickness of the sixth substrate  906  and the fourth substrate  901  after being bonded and fixed may be equal to the thickness of the fifth substrate  902 . The increase of the insertion loss of the high-frequency signal caused by the too large total thickness of the sixth substrate  906  and the fourth substrate  901  after being bonded and fixed as a whole may be avoided. Thus, the gain of the liquid crystal antenna of this embodiment may be increased and the signal insertion loss may be reduced. 
     It can be understood that each antenna unit in this embodiment may be understood as the liquid crystal antenna  000  in the above embodiments, and the second external metal layer  904  in this embodiment may be a copper layer structure with a whole surface structure, and the sixth substrate  906  may be a printed circuit board. The second external metal layer  904  of this embodiment may also be a copper adhesive with a whole surface structure. The specific effects that can be achieved may be referred to the implementation of the second external metal layer  904  having a copper layer structure or a copper adhesive structure in the above embodiments, and this embodiment will not be repeated here. 
     It can be seen from the foregoing embodiments that the liquid crystal antenna and the fabrication method of the liquid crystal antenna provided by the present disclosure may achieve at least the following beneficial effects. 
     In the liquid crystal antenna provided by the present disclosure, the first substrate may be provided with the first conductive layer only on the side facing toward the second substrate, the second substrate may be provided with the second conductive layer only on the side facing toward the first substrate, and the radiation electrodes may also be provided in the liquid crystal cell. For example, the structures integrated in a liquid crystal cell and used to realize the antenna function may only be disposed on one side surface of a same substrate to avoid the introduction of the processes for forming conductive layers on both sides of the substrate during the fabrication process of the liquid crystal antenna. That is, the present disclosure may not need to use the process of fabricating and patterning conductive metal layers on both surfaces of a substrate, and may reduce the needs for fabricating conductive structures on one side of the substrate and then turning it over to fabricate another conductive layer on the other side of the substrate, and the processes of exposure, development, and etching. Thus, the manufacturing difficulty and manufacturing cost may be reduced, and the production efficiency, and the product yield may be improved. The side of the first substrate of the present disclosure away from the liquid crystal layer may also include an external metal layer, which may be connected to a fixed potential. The external metal layer may refer to the structure additionally formed on the side surface of the first substrate facing away from the liquid crystal layer after the first substrate and the second substrate are formed into a liquid crystal cell. Thus, the process for forming conductive metal layers on two sides of one first substrate during the process for forming the liquid crystal cell may be avoided. According, the difficulty of the production process may be reduced, and the production efficiency may be improved. The external metal layer of the present disclosure may not only be used as a reflective layer, but when the phase of the microwave signal is shifted, it may ensure that the microwave signal is only propagated in the liquid crystal cell of the liquid crystal antenna during the phase shifting process and may prevent it from diverging to the outside of the liquid crystal antenna. When the microwave signal is transmitted to the external metal layer, the microwave signal may be reflected back through the external metal layer of the entire structure. The external metal layer connected to a fixed potential may also be used to shield external signals to avoid external signals from interfering the microwave signals to ensure the accuracy of the phase shift of the microwave signal. Thus, the radiation gain of the antenna may be increased. Further, when the external metal layer of the present disclosure is disposed on the side of the first substrate away from the liquid crystal layer after the liquid cell is formed, the requirements for the bonding accuracy may be reduced, and the manufacturing difficulty and the manufacturing cost may be further reduced. 
     Although some specific embodiments of the present disclosure have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of the present disclosure. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present disclosure. The scope of the disclosure is defined by the appended claims.