Patent Publication Number: US-2022231407-A1

Title: Liquid crystal antenna and preparation method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Chinese Patent Application No. 202111673857.6 filed Dec. 31, 2021, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to the field of communication technologies and, in particular, to a liquid crystal antenna and a preparation method thereof. 
     BACKGROUND 
     A liquid crystal antenna is a novel arrayed antenna manufactured by combining a conventional patch antenna and a liquid crystal phase shifter. The liquid crystal phase shifter adjusts a phase of a radio frequency signal by controlling the deflection of liquid crystal molecules. The liquid crystal antennas have broad application prospects in fields of satellite receiving antennas, on-board radars, 5G base station antennas and the like. 
     However, existing liquid crystal antennas are difficult to prepare and lack of reliability. 
     SUMMARY 
     The present disclosure provides a liquid crystal antenna and a preparation method of the liquid crystal antenna to reduce preparation difficulty and improve reliability. 
     In a first aspect, embodiments of the present disclosure provide a liquid crystal antenna. 
     The liquid crystal antenna includes a liquid crystal cell. 
     The liquid crystal cell includes a first substrate, a second substrate, a microstrip line, a ground metal layer, a liquid crystal layer, and frame glue. 
     The first substrate and the second substrate are disposed opposite to each other. 
     The microstrip line is disposed on a side of the second substrate facing the first substrate. 
     The ground metal layer is disposed on a side of the first substrate facing the second substrate. 
     The liquid crystal layer is disposed between the first substrate and the second substrate. 
     The frame glue is disposed between the first substrate and the second substrate and around the liquid crystal layer. 
     The liquid crystal antenna further includes a third substrate, a fourth substrate, and a radiation electrode. 
     The third substrate is disposed on a side of the first substrate facing away from the second substrate, and the fourth substrate is disposed on a side of the second substrate facing away from the third substrate. 
     The radiation electrode is disposed on a side of the third substrate facing away from the fourth substrate. 
     The third substrate extends beyond an edge of the first substrate, the fourth substrate extends beyond edges of the second substrate on at least two sides, a connection structure is disposed between the third substrate and the fourth substrate, and the connection structure is disposed on an outer side of the frame glue. 
     In a second aspect, embodiments of the present disclosure further provide a preparation method of a liquid crystal antenna. The method includes the steps described below. 
     A liquid crystal cell is prepared. The liquid crystal cell includes frame glue, a microstrip line, a ground metal layer, a liquid crystal layer, and a first substrate and a second substrate disposed opposite to each other. The microstrip line is disposed on a side of the second substrate facing the first substrate. The ground metal layer is disposed on a side of the first substrate facing the second substrate. The liquid crystal layer is disposed between the first substrate and the second substrate. The frame glue is disposed between the first substrate and the second substrate, and the frame glue is disposed around the liquid crystal layer. 
     A third substrate and a fourth substrate are provided and a radiation electrode is prepared on a side of the third substrate. 
     The third substrate, the fourth substrate, and the liquid crystal cell are combined so that a liquid crystal antenna is formed. The third substrate is disposed on a side of the first substrate facing away from the second substrate. The fourth substrate is disposed on a side of the second substrate facing away from the third substrate. The radiation electrode is disposed on a side of the third substrate facing away from the fourth substrate. The third substrate extends beyond an edge of the first substrate. The fourth substrate extends beyond edges of the second substrate on at least two sides. A connection structure is disposed between the third substrate and the fourth substrate, and the connection structure is disposed on an outer side of the frame glue. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a structure view of a liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 2  is a sectional view of  FIG. 1  taken along an A-A′ direction; 
         FIG. 3  is a structure view of a third substrate, a fourth substrate, and a liquid crystal cell according to an embodiment of the present disclosure; 
         FIG. 4  is a sectional view of  FIG. 3  taken along a B-B′ direction; 
         FIG. 5  is a structure view of another third substrate, fourth substrate, and liquid crystal cell according to an embodiment of the present disclosure; 
         FIG. 6  is a structure view of another third substrate, fourth substrate, and liquid crystal cell according to an embodiment of the present disclosure; 
         FIG. 7  is a structure view of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 8  is a sectional view of  FIG. 7  taken along a C-C′ direction; 
         FIG. 9  is a sectional view showing part of a liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 10  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 11  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 12  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 13  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 14  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 15  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 16  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 17  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 18  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 19  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 20  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 21  is a flowchart of a preparation method of a liquid crystal antenna according to an embodiment of the present disclosure; 
         FIG. 22  is a schematic diagram showing a process of a preparation method of a liquid crystal cell according to an embodiment of the present disclosure; 
         FIG. 23  is a schematic diagram showing a process of a preparation method of a liquid crystal antenna according to an embodiment of the present disclosure; and 
         FIG. 24  is a schematic diagram showing a process of a preparation method of another liquid crystal antenna according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure is further described hereinafter in detail in conjunction with drawings and embodiments. It is to be understood that embodiments described hereinafter are intended to explain the present disclosure and not to limit the present disclosure. Additionally, it is to be noted that for ease of description, merely part, not all, of structures related to the present disclosure are illustrated in the drawings. 
       FIG. 1  is a structure view of a liquid crystal antenna according to an embodiment of the present disclosure.  FIG. 2  is a sectional view of  FIG. 1  taken along an A-A′ direction. As shown in  FIGS. 1 and 2 , a liquid crystal antenna provided by the embodiments of the present disclosure includes a liquid crystal cell  10 . The liquid crystal cell  10  includes a microstrip line  11 , a ground metal layer  12 , a liquid crystal layer  13 , frame glue  14 , and a first substrate  15  and a second substrate  16  disposed opposite to each other. The microstrip line  11  is disposed on a side of the second substrate  16  facing the first substrate  15 . The ground metal layer  12  is disposed on a side of the first substrate  15  facing the second substrate  16 . The liquid crystal layer  13  is disposed between the first substrate  15  and the second substrate  16 . The frame glue  14  is disposed between the first substrate  15  and the second substrate  16 , and the frame glue  14  is disposed around the liquid crystal layer  13 . The liquid crystal antenna further includes a third substrate  17 , a fourth substrate  18  and a radiation electrode  19 . The third substrate  17  is disposed on a side of the first substrate  15  facing away from the second substrate  16 . The fourth substrate  18  is disposed on a side of the second substrate  16  facing away from the third substrate  17 . The radiation electrode  19  is disposed on a side of the third substrate  17  facing away from the fourth substrate  18 . The third substrate  17  extends beyond an edge of the first substrate  15 . The fourth substrate  18  extends beyond edges of the second substrate  16  on at least two sides. A connection structure  20  is disposed between the third substrate  17  and the fourth substrate  18 , and the connection structure  20  is disposed on an outer side of the frame glue  14 . 
     Exemplarily, as shown in  FIGS. 1 and 2 , the liquid crystal cell  10  is filled with a liquid crystal layer  13 . The microstrip line  11  is disposed on a side of the liquid crystal layer  13  facing the second substrate  16 . The ground metal layer  12  is disposed on a side of the liquid crystal layer  13  facing the first substrate  15 . In this embodiment, driving voltage signals are applied to the microstrip line  11  and the ground metal layer  12  separately so as to form an electric field between the microstrip line  11  and the ground metal layer  12 . The electric field may drive liquid crystal molecules  131  in the liquid crystal layer  13  to deflect, thereby changing a dielectric constant of the liquid crystal layer  13 . The microstrip line  11  is further configured to transmit a radio frequency signal. The radio frequency signal is transmitted in the liquid crystal layer  13  between the microstrip line  11  and the ground metal layer  12 . Due to the change of the dielectric constant of the liquid crystal layer  13 , a phase of the radio frequency signal transmitted on the microstrip line  11  is shifted, thereby changing the phase of the radio frequency signal to implement a phase shift function of the radio frequency signal. The driving voltage signals on the microstrip line  11  and the ground metal layer  12  are controlled so that a deflection angle of a liquid crystal molecule  131  may be controlled. Thus, a phase adjusted in a phase shift process of the radio frequency signal may be controlled, and finally a beam-pointing direction of the radio frequency signal transmitted by the liquid crystal antenna is controlled. 
     It is to be noted that the liquid crystal antenna may include one or more microstrip lines  11 . For example, as shown in  FIG. 1 , the liquid crystal antenna includes four microstrip lines  11  distributed in an array. In other embodiments, those skilled in the art may set the number, shape, and layout of the microstrip lines  11  according to actual requirements, which is not limited in the embodiments of the present disclosure. 
     With continued reference to  FIGS. 1 and 2 , the frame glue  14  is disposed between the first substrate  15  and the second substrate  16 , and the frame glue  14  is disposed around the liquid crystal layer  13  to support the first substrate  15  and the second substrate  16  so as to provide an accommodation space for the liquid crystal layer  13 . 
     With continued reference to  FIGS. 1 and 2 , the liquid crystal antenna further includes the third substrate  17 , the fourth substrate  18 , and the radiation electrode  19 . The third substrate  17  is disposed on the side of the first substrate  15  facing away from the second substrate  16 . The fourth substrate  18  is disposed on the side of the second substrate  16  facing away from the third substrate  17 . The radiation electrode  19  is disposed on the side of the third substrate  17  facing away from the fourth substrate  18 . In this manner, during the preparation of the liquid crystal antenna, the radiation electrode  19  may be formed on the third substrate  17 , the ground metal layer  12  may be formed on the first substrate  15 , and then the third substrate  17  and the first substrate  15  are combined. The preparation of the radiation electrode  19  and the ground metal layer  12  can be implemented without a double-sided patterning process, resulting in a simple process, a small loss of consumable materials, a low cost, a high yield, and easy mass production. 
     With continued reference to  FIGS. 1 and 2 , exemplarily, a vertical projection of the ground metal layer  12  on the third substrate  17  at least partially overlaps a vertical projection of the radiation electrode  19  on the third substrate  17 . The ground metal layer  12  is provided with a first hollow portion  121 . A vertical projection of the radiation electrode  19  on a plane where the ground metal layer  12  is located covers the first hollow portion  121 . A vertical projection of the microstrip line  11  on the plane where the ground metal layer  12  is located at least partially overlaps the first hollow portion  121 . The radio frequency signal is transmitted between the microstrip line  11  and the ground metal layer  12 . The liquid crystal layer  13  between the microstrip line  11  and the ground metal layer  12  performs a phase shift on the radio frequency signal so as to change the phase of the radio frequency signal. The phase-shifted radio frequency signal is coupled to the radiation electrode  19  at the first hollow portion  121  of the ground metal layer  12  so as to realize that the radiation electrode  19  radiates a signal outwardly. 
     It is to be noted that radiation electrodes  19  are disposed corresponding to the microstrip lines  11 . For example, the radiation electrodes  19  are in one-to-one correspondence with the microstrip lines  11 , and the radiation electrodes  19  corresponding to different microstrip lines  11  are insulated from each other. Optionally, different driving voltage signals are applied to different microstrip lines  11 , so that liquid crystal molecules at positions corresponding to the different microstrip lines  11  are deflected differently. Thus, dielectric constants of the liquid crystal layer  13  at respective positions are different, thereby enabling adjustment of phases of radio frequency signals at positions of the different microstrip lines  11  and finally realizing that the radio frequency signals have different beam-pointing directions. 
     Further, with continued reference to  FIGS. 1 and 2 , along a direction parallel to the plane where the first substrate  15  is located, the third substrate  17  extends beyond the edge of the first substrate  15 , and the fourth substrate  18  extends beyond the edges of the second substrate  16  on the at least two sides. Thus, a fixing space is provided for the connection structure  20  on the outer side of the frame glue  14  so as to dispose the connection structure  20  between the third substrate  17  and the fourth substrate  18 . 
     As shown in  FIG. 1 , the connection structure  20  may be disposed around the frame glue  14 . On the one hand, the liquid crystal cell  10 , the third substrate  17 , and the fourth substrate  18  are adhered together from a side surface of the liquid crystal cell  10 , thereby assembling the liquid crystal cell  10 , the third substrate  17 , and the fourth substrate  18 . On the other hand, the overall encapsulation of the liquid crystal antenna can be implemented so that a microstrip line array structure in the liquid crystal cell  10  can be effectively protected, thereby resisting an influence of a bad external environment, ensuring phase shift performance of the liquid crystal antenna, and improving reliability of the liquid crystal antenna. 
     It is to be noted that along the direction parallel to the plane where the first substrate  15  is located, the fourth substrate  18  may extend beyond edges of the second substrate  16  on two sides or may extend beyond the second substrate  16  on three, four, or more sides. Those skilled in the art may set a relative positional relationship between the fourth substrate  18  and the second substrate  16  according to a shape of the liquid crystal antenna. 
       FIG. 3  is a structure view of a third substrate, a fourth substrate, and a liquid crystal cell according to an embodiment of the present disclosure.  FIG. 4  is a sectional view of  FIG. 3  taken along a B-B′ direction. As shown in  FIGS. 3 and 4 , exemplarily, the liquid crystal cell  10  is triangular and along the direction parallel to the plane where the first substrate  15  is located, the fourth substrate  18  extends beyond the edges of the second substrate  16  on two sides. 
       FIG. 5  is a structure view of another third substrate, fourth substrate, and liquid crystal cell according to an embodiment of the present disclosure. As shown in  FIG. 5 , exemplarily, the liquid crystal cell  10  is pentagonal and along the direction parallel to the plane where the first substrate  15  is located, the fourth substrate  18  extends beyond the edges of the second substrate  16  on four sides. 
       FIG. 6  is a structure view of another third substrate, fourth substrate, and liquid crystal cell according to an embodiment of the present disclosure. As shown in  FIG. 6 , exemplarily, the liquid crystal cell  10  is hexagonal and along the direction parallel to the plane where the first substrate  15  is located, the fourth substrate  18  extends beyond the edges of the second substrate  16  on five sides. 
     It is to be noted that for clearly showing relative positional relationships among the third substrate  17 , the fourth substrate  18 , and the liquid crystal cell  10 , merely part of structures of the liquid crystal antenna is shown in  FIGS. 3 to 6 . In fact, the liquid crystal antenna may further include other functional structures. The preceding drawings are not to limit this embodiment. 
     With continued reference to  FIGS. 1 and 2 , exemplarily, the liquid crystal cell  10  is quadrilateral and along the direction parallel to the plane where the first substrate  15  is located, the fourth substrate  18  extends beyond the edges of the second substrate  16  on three sides. 
     In other embodiments, exemplarily, when the liquid crystal cell  10  is pentagonal and along the direction parallel to the plane where the first substrate  15  is located, the fourth substrate  18  may also be configured to extend beyond the edges of the second substrate  16  on four sides, and so on, and the details are not repeated here. 
     In summary, according to the liquid crystal antenna provided by the embodiments of the present disclosure, the third substrate  17  and the radiation electrode  19  and the fourth substrate  18  are respectively disposed on two sides of the liquid crystal cell  10 , and the radiation electrode  19  is disposed on the side of the third substrate  17  facing away from the fourth substrate  18  so that the radiation electrode  19  is formed on the third substrate  17  and the ground metal layer  12  is formed on the first substrate  15 . Thus, the preparation of the radiation electrode  19  and the ground metal layer  12  can be implemented without a double-sided patterning process, preparation difficulty is reduced, and problems of a complicated preparation process, a great loss of consumable materials, a high cost, a low yield, and difficult mass production of the existing liquid crystal antenna are solved. In addition, the third substrate  17  is configured to extend beyond the edge of the first substrate  15  and the fourth substrate  18  is configured to extend beyond the edges of the second substrate  16  on at least two sides, thereby providing an adhesive space on the outer side of the frame glue  14  so as to dispose the connection structure  20  between the third substrate  17  and the fourth substrate  18 . In this manner, on the one hand, the liquid crystal cell  10 , the third substrate  17 , and the fourth substrate  18  are adhered together from the side surface of the liquid crystal cell  10  so as to assemble the liquid crystal cell  10 , the third substrate  17 , and the fourth substrate  18 , and on the other hand, the overall encapsulation of the liquid crystal antenna is implemented and the microstrip line array structure in the liquid crystal cell  10  is effectively protected, thereby resisting the influence of the bad external environment, ensuring the phase shift performance of the liquid crystal antenna, and improving the reliability of the liquid crystal antenna. 
     With continued reference to  FIGS. 1 to 4 , optionally, one side of the liquid crystal cell  10  is a bonding side  21 . On the bonding side  21 , the second substrate  16  extends beyond the edge of the first substrate  15 , and on sides of the liquid crystal cell  10  other than the bonding side  21 , the connection structure  20  is in contact with the third substrate  17  and the fourth substrate  18  separately. 
     As shown in  FIGS. 1 and 2 , the liquid crystal cell  10  includes the bonding side  21 , and on the bonding side  21 , the second substrate  16  extends beyond the edge of the first substrate  15 . A bonding terminal  22  may be disposed on a surface of a portion of the second substrate  16  protruding from the first substrate  15 . The bonding terminal  22  is correspondingly and electrically connected to the microstrip line  11 , and the bonding terminal  22  may be configured to connect the microstrip line  11  to an external circuit so that the microstrip line  11  receives a driving voltage signal provided by the external circuit, thereby driving the liquid crystal molecules  131  in the liquid crystal layer  13  to deflect. The bonding terminal  22  may be correspondingly connected to the microstrip line  11  through a driving voltage signal transmission line  24 , and the arrangement of the driving voltage signal transmission line  24  may be set according to the actual requirements. 
     Exemplarily, the bonding terminal  22  may be bonded to a flexible printed circuit (FPC)  23  on which the external circuit is disposed so that the microstrip line  11  receives the driving voltage signal provided by the external circuit through the FPC  23 . 
     In another embodiment, the bonding terminal  22  may also be directly connected to the external circuit so that the microstrip line  11  receives the driving voltage signal provided by the external circuit. 
     In another embodiment, the external circuit may also be disposed on another mainboard. The bonding terminal  22  is bonded to the FPC  23  and the FPC  23  is then bonded to the external circuit, thereby realizing that the microstrip line  11  receives the driving voltage signal provided by the external circuit. 
     In another optional embodiment, a chip may be disposed on the second substrate  16  for processing electrical signals. The chip is connected to the bonding terminal  22  through a circuit disposed on the second substrate  16 . The bonding terminal  22  is connected to the FPC  23  to process the electrical signals through the cooperation between the FPC  23  and the chip, and device integration is improved. 
     With continued reference to  FIGS. 1 to 4 , the fourth substrate  18  may be flush with the edge of the second substrate  16  on the bonding side  21  of the liquid crystal cell  10  along the direction parallel to the plane where the first substrate  15  is located, which is not limited thereto. The connection structure  20  is in contact with the third substrate  17  and the second substrate  16  separately. On the sides of the liquid crystal cell  10  other than the bonding side  21 , the fourth substrate  18  may be configured to extend beyond the edges of the second substrate  16  along the direction parallel to the plane where the first substrate  15  is located. Thus, on the sides of the liquid crystal cell  10  other than the bonding side  21 , the connection structure  20  may be configured to be in contact with the third substrate  17  and the fourth substrate  18  separately. On the sides of the liquid crystal cell  10  other than the bonding side  21 , the connection structure  20  is configured to be in contact with the third substrate  17  and the fourth substrate  18  separately so that areas of the connection structure  20  separately contacting with the third substrate  17  and the fourth substrate  18  can be increased. Thus, an adhesion force is greater, thereby improving encapsulation firmness of the liquid crystal antenna. 
     With continued reference to  FIGS. 2 and 4 , optionally, the connection structure  20  is in contact with sidewalls of the liquid crystal cell  10 . 
     As shown in  FIGS. 2 and 4 , the connection structure  20  is configured to be in contact with the sidewalls of the liquid crystal cell  10  so that a fixing force to the liquid crystal cell  10  may be increased and the liquid crystal cell  10  does not move relative to the third substrate  17  and the fourth substrate  18 , thereby improving stability of the liquid crystal antenna. 
     With continued reference to  FIGS. 2 and 4 , optionally, the sidewalls of the liquid crystal cell  10  include a sidewall of the first substrate  15 , a sidewall of the second substrate  16 , and a sidewall of the frame glue  14  facing away from the liquid crystal layer  13 . The connection structure  20  is in contact with at least the sidewall of the first substrate  15  and the sidewall of the second substrate  16 . 
     The connection structure  20  is configured to be in contact with the sidewall of the first substrate  15  so that a fixing force to the first substrate  15  can be increased and the first substrate  15  does not move relative to the third substrate  17 , thereby improving the stability of the liquid crystal antenna. 
     It is to be noted that the connection structure  20  may be in contact with merely part of the sidewalls of the first substrate  15 . The connection structure  20  may also be in contact with each sidewall of the first substrate  15 . It is to be understood that the larger the contact area between the connection structure  20  and the sidewalls of the first substrate  15  is, the greater the fixing force to the first substrate  15  is and more strongly the first substrate  15  is fixed between the third substrate  17  and the fourth substrate  18 . 
     Similarly, the connection structure  20  is configured to be in contact with sidewalls of the second substrate  16  so that a fixing force to the second substrate  16  can be increased and the second substrate  16  does not move relative to the fourth substrate  18 , thereby improving the stability of the liquid crystal antenna. 
     It is to be noted that the connection structure  20  may be in contact with merely part of sidewalls of the second substrate  16 . The connection structure  20  may also be in contact with each sidewall of the second substrate  16 . It is to be understood that the larger the contact area between the connection structure  20  and the sidewalls of the second substrate  16  is, the greater the fixing force for the second substrate  16  is and more strongly the second substrate  16  is fixed between the third substrate  17  and the fourth substrate  18 . 
     Exemplarily, as shown in  FIGS. 2 and 4 , the connection structure  20  is in contact with each sidewall of the first substrate  15 , and the connection structure  20  is in contact with the sidewalls of the second substrate  16  on the sides of the liquid crystal cell  10  other than the bonding side  21 , which is not limited thereto. 
     It is to be noted that when the liquid crystal antenna is prepared, the third substrate  17  and the fourth substrate  18  are respectively placed at corresponding positions of the liquid crystal cell  10 , and then the connection structure  20  is formed on the sidewalls of the liquid crystal cell  10  so that the connection structure  20  is in contact with the sidewalls of the first substrate  15  and the second substrate  16 . For example, the sidewalls of the liquid crystal cell  10  are directly coated with adhesive layers to manufacture the connection structure  20 . In this case, the sidewalls of the liquid crystal cell  10  may have a positioning function. Multiple coatings are directly applied along the sidewalls of the liquid crystal cell  10  to form the connection structure  20 , which is less difficult to manufacture and does not reduce an overall yield. 
     Further, the connection structure  20  may also be in contact with the sidewall of the frame glue  14  facing away from the liquid crystal layer  13  so that the fixing force to the liquid crystal cell  10  may be further increased. Thus, the liquid crystal cell  10  does not shake between the third substrate  17  and the fourth substrate  18 , thereby improving the stability of the liquid crystal antenna. 
     It is to be noted that the connection structure  20  may be in contact with merely part of the sidewalls of the frame glue  14  facing away from the liquid crystal layer  13 . The connection structure  20  may be in contact with each sidewall of the frame glue  14  facing away from the liquid crystal layer  13 . It is to be understood that the larger the contact area between the connection structure  20  and the sidewall of the frame glue  14  facing away from the liquid crystal layer  13  is, the greater the fixing force to the liquid crystal cell  10  is and more strongly the liquid crystal cell  10  is fixed between the third substrate  17  and the fourth substrate  18 . 
     It is to be understood that if the connection structure  20  is manufactured by directly coating the sidewalls of the liquid crystal cell  10  with adhesive layers, whether the connection structure  20  is in contact with the sidewall of the frame glue  14  facing away from the liquid crystal layer  13  depends on relative positional relationships between the frame glue  14  and the first substrate  15  and the second substrate  16 . When the frame glue  14  is closer to the edges of the first substrate  15  and the second substrate  16 , it is easier for the connection structure  20  to be in contact with the sidewall of the frame glue  14  facing away from the liquid crystal layer  13 . 
     With continued reference to  FIGS. 1 to 4 , optionally, the connection structure  20  includes an encapsulant. 
     Exemplarily, as shown in  FIGS. 1 to 4 , the connection structure  20  may be made of the encapsulant. The encapsulant is coated to fix the third substrate  17 , the fourth substrate  18 , and the liquid crystal cell  10  so that the third substrate  17 , the fourth substrate  18 , and the liquid crystal cell  10  are adhered together with a high adhesion degree. In addition, the connection structure  20  may be manufactured by a mature process such as coating, which is less difficult to manufacture and does not reduce the overall yield. 
     A range of the encapsulant may be configured according to the actual requirements. For example, as shown in  FIGS. 1 to 4 , the encapsulant surrounds the frame glue  14  in a circle, thereby ensuring adhesion firmness and a sealing degree of the encapsulation, which is not limited thereto. 
     In addition, the encapsulant may be made of a resin material or other adhesive materials, which is not limited in the embodiments of the present disclosure. 
     With continued reference to  FIGS. 1 to 4 , optionally, a vertical projection of the encapsulant on a plane where the fourth substrate  18  is located is within the fourth substrate  18 . 
     As shown in  FIGS. 1 to 4 , the vertical projection of the encapsulant on the plane where the fourth substrate  18  is located is configured to be within the fourth substrate  18  so that the encapsulant does not extend beyond an edge of the fourth substrate  18  along a direction parallel to the first substrate  15 , thereby preventing the encapsulant from being exposed and affecting beauty of the liquid crystal antenna. In addition, materials may be saved and a manufacturing cost of the liquid crystal antenna may be reduced. In addition, it helps to reduce an influence of the encapsulant on a dimension of the liquid crystal antenna and facilitates the miniaturization design of the liquid crystal antenna. 
     In addition, when the liquid crystal antenna is manufactured, a large-substrate manufacturing process may be adopted, in which multiple liquid crystal antenna structures are formed on one large substrate and then separated from each other by cutting. In this case, if the encapsulant extends beyond the edge of the fourth substrate  18 , the cutting may be affected by the encapsulant, resulting in affecting a cutting effect. Therefore, in this embodiment, the encapsulant is configured not to extend beyond the edge of the fourth substrate  18  so as to facilitate the cutting. 
     It is to be noted that in the large-substrate manufacturing process, a large third substrate  17  and a large fourth substrate  18  are respectively placed at corresponding positions of the liquid crystal cell  10 , and then the encapsulant is coated onto the side surface of the liquid crystal cell  10 . In this case, the bonding side  21  of the liquid crystal cell  10  may remain uncoated with the encapsulant. After the liquid crystal antennas are separated from each other by cutting, bonding is performed on the bonding side  21  of the liquid crystal cell  10 . After the bonding process is completed, glue is dispensed to the bonding side  21  of the liquid crystal cell  10  so as to implement the encapsulation of the bonding side  21  of the liquid crystal cell  10 . In this manner, it is conducive to increasing efficiency of the preparation method and improving the overall yield. 
     Exemplarily,  FIG. 7  is a structure view of another liquid crystal antenna according to an embodiment of the present disclosure.  FIG. 8  is a sectional view of  FIG. 7  taken along a C-C′ direction. As shown in  FIGS. 7 and 8 , the encapsulant may be configured to be flush with the edge of the fourth substrate  18  along the direction parallel to the first substrate  15  so that areas of the encapsulant separately contacting with the third substrate  17  and the fourth substrate  18  can be maximized without affecting the dimension of the liquid crystal antenna. Thus, the adhesion firmness is improved, thereby improving reliability of an overall liquid crystal antenna. 
       FIG. 9  is a sectional view showing part of a liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIG. 9 , optionally, the liquid crystal antenna provided by the embodiments of the present disclosure further includes a feed structure  46  coupled to the microstrip line  11 . The feed structure  46  is disposed on a side of the fourth substrate  18  facing away from the third substrate  17 . A vertical projection of the feed structure  46  on the fourth substrate  18  covers a vertical projection of the microstrip line  11  on the fourth substrate  18  so as to transmit the radio frequency signal to the microstrip line  11 , thereby playing a role of starting vibration.  FIG. 10  is a sectional view showing part of a liquid crystal antenna according to an embodiment of the present disclosure.  FIG. 11  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure.  FIG. 12  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIGS. 10 to 12 , optionally, the third substrate  17  includes a first groove  25  and the first substrate  15  is accommodated in the first groove  25 ; and/or the fourth substrate  18  includes a second groove  26  and the second substrate  16  is accommodated in the second groove  26 . 
     Exemplarily, as shown in  FIG. 10 , the first groove  25  is disposed on the third substrate  17 , and the first substrate  15  is accommodated in the first groove  25 . The first groove  25  can function as an engaging position so that a position of the liquid crystal cell  10  can be more accurate. In addition, the first substrate  15  can be prevented from moving relative to the third substrate  17  along the direction parallel to the first substrate  15 , thereby helping improve firmness of a connection between the third substrate  17  and the first substrate  15  and thus improving the reliability of the overall liquid crystal antenna. 
     For example, as shown in  FIG. 11 , the second groove  26  is disposed on the fourth substrate  18 , and the second substrate  16  is accommodated in the second groove  26 . The second groove  26  can function as the engaging position so that the position of the liquid crystal cell  10  can be more accurate. In addition, the second substrate  16  can also be prevented from moving relative to the fourth substrate  18  along the direction parallel to the first substrate  15 , thereby helping improve firmness of a connection between the fourth substrate  18  and the second substrate  16  and thus improving the reliability of the overall liquid crystal antenna. 
     Further, as shown in  FIG. 12 , it is also feasible that the third substrate  17  is configured to include the first groove  25  and the first substrate  15  is accommodated in the first groove  25 ; and the fourth substrate  18  is configured to include the second groove  26  and the second substrate  16  is accommodated in the second groove  26 , so as to further improve the accuracy of the position of the liquid crystal cell  10  and the encapsulation firmness among the third substrate  17 , the fourth substrate  18 , and the liquid crystal cell  10 , thereby further improving the reliability of the overall liquid crystal antenna. 
     With continued reference to  FIGS. 2, 4, and 8 to 12 , optionally, the third substrate  17  and the first substrate  15  are connected to each other through a first adhesive layer  27 ; and/or the second substrate  16  and the fourth substrate  18  are connected to each other through a first adhesive layer  27 . 
     Exemplarily, as shown in  FIGS. 2, 4, and 8 to 12 , first adhesive layers  27  are disposed between the third substrate  17  and the first substrate  15  and between the second substrate  16  and the fourth substrate  18  so that the third substrate  17  is adhered to the first substrate  15  and the second substrate  16  is adhered to the fourth substrate  18  by laminating whole surfaces. Thus, the firmness of the connection between the third substrate  17  and the first substrate  15  and the firmness of the connection between the second substrate  16  and the fourth substrate  18  can be improved. 
     It is to be noted that  FIGS. 2, 4, 8 to 12  merely illustrate an example in which the first adhesive layers  27  are disposed between the third substrate  17  and the first substrate  15  and between the second substrate  16  and the fourth substrate  18 , which is not limited thereto. In other embodiments, the first adhesive layer  27  may be disposed merely between the third substrate  17  and the first substrate  15 , or the first adhesive layer  27  may be disposed merely between the second substrate  16  and the fourth substrate  18 . Those skilled in the art may dispose the first adhesive layer  27  according to the actual requirements. 
     In addition, the first adhesive layer  27  may be an optical adhesive or another adhesive material, which is not limited in the embodiments of the present disclosure. 
     With continued reference to  FIGS. 2, 4, and 8 to 12 , optionally, the thickness of the first adhesive layer is D1, where 0.5 mm≤D1≤1 mm. 
     As shown in  FIGS. 2, 4, and 8 to 12 , since the connection structure  20  on the side surface of the liquid crystal cell  10  plays a role of bonding and encapsulate the liquid crystal cell  10 , the third substrate  17 , and the fourth substrate  18 , a relatively thin first adhesive layer  27  can ensure the firmness of the connection among the liquid crystal cell  10 , the third substrate  17 , and the fourth substrate  18 . 
     In this embodiment, the thickness D1 of the first adhesive layer  27  is configured to satisfy 0.5 mm≤D1≤1 mm so that an influence of the first adhesive layer  27  on the radio frequency signal can be reduced while the encapsulation firmness of the liquid crystal antenna is ensured, thereby reducing an additional loss of the radio frequency signal and helping improve the performance of the liquid crystal antenna. 
       FIG. 13  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIG. 13 , optionally, a surface of a side of the third substrate  17  facing the first substrate  15  is in contact with a surface of a side of the first substrate  15  facing the third substrate  17 ; and/or a surface of a side of the second substrate  16  facing the fourth substrate  18  is in contact with a surface of a side of the fourth substrate  18  facing the second substrate  16 . 
     Exemplarily, as shown in  FIG. 13 , since the connection structure  20  on the side surface of the liquid crystal cell  10  plays a role of bonding and encapsulating the liquid crystal cell  10 , the third substrate  17 , and the fourth substrate  18 , the first adhesive layer  27  may be canceled so that the third substrate  17  and the first substrate  15  are in direct contact with each other and the second substrate  16  and the fourth substrate  18  are in surface contact with each other, thereby avoiding the influence of the first adhesive layer  27  on the radio frequency signal, further reducing the additional loss of the radio frequency signal, and helping improve the performance of the liquid crystal antenna. 
     It is to be noted that  FIG. 13  merely illustrates an example in which the third substrate  17  and the first substrate  15  are in direct contact with each other and the second substrate  16  and the fourth substrate  18  are in direct contact with each other, which is not limited thereto. In other embodiments, merely the third substrate  17  and the first substrate  15  may be in direct contact with each other, or merely the second substrate  16  and the fourth substrate  18  may be in direct contact with each other, which can be set by those skilled in the art according to the actual requirements. 
     With continued reference to  FIGS. 1 and 7 , optionally, the second substrate  16  includes a bonding connection region  28  disposed on the bonding side  21  of the liquid crystal cell  10 . The bonding connection region  28  is electrically connected to the microstrip  11 , and the bonding connection region  28  is connected to the external circuit. 
     Exemplarily, as shown in  FIGS. 1 and 7 , the second substrate  16  is provided with the bonding connection region  28  in which the bonding terminal  22  is disposed. The bonding terminal  22  may be correspondingly connected to the microstrip line  11  through the driving voltage signal transmission line  24 . The FPC  23  is bonded to the bonding terminal  22  in the bonding connection region  28  so that the bonding terminal  22  is connected to the external circuit through the FPC  23 . Thus, the microstrip line  11  receives the driving voltage signal provided by the external circuit to drive the liquid crystal molecules  131  in the liquid crystal layer  13  to deflect. 
     A position and a range where the bonding connection region  28  is disposed may be set according to the actual requirements. Exemplarily, as shown in  FIGS. 1 and 7 , the bonding connection region  28  may be disposed at the portion of the second substrate  16  protruding from the first substrate  15 . Thus, when the bonding connection region  28  is bonded to the FPC  23 , the FPC  23  is not limited by a space of the first substrate  15 , thereby facilitating the bonding between the bonding connection region  28  and the FPC  23 . 
       FIG. 14  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIG. 14 , optionally, the connection structure  20  includes a first encapsulation sidewall  29  disposed on the third substrate  17  and a second adhesive layer  30  disposed on a side of the first encapsulation sidewall  29  facing the fourth substrate  18 . The first encapsulation sidewall  29  is disposed around the frame glue  14 , and the bonding connection region  28  is disposed on a side of the first encapsulation sidewall  29  facing away from the frame glue  14 . The first encapsulation sidewall  29  is connected to the second substrate  16  and the fourth substrate  18  separately through the second adhesive layer  30 . 
     Exemplarily, as shown in  FIG. 14 , the connection structure  20  includes the first encapsulation sidewall  29  disposed around the frame glue  14  and the second adhesive layer  30 . The first encapsulation sidewall  29  adheres to the second substrate  16  and the fourth substrate  18  separately through the second adhesive layer  30  so as to fix the third substrate  17 , the fourth substrate  18 , and the liquid crystal cell  10  together, thereby implementing the overall encapsulation of the liquid crystal antenna. 
     Further, as shown in  FIG. 14 , the bonding connection region  28  is disposed on the side of the first encapsulation sidewall  29  facing away from the frame glue  14  so that the bonding between the bonding connection region  28  and the FPC  23  is not affected by the first encapsulation sidewall  29 . 
     It is to be noted that on the bonding side  21  of the liquid crystal cell  10 , since the bonding connection region  28  is disposed on the side of the first encapsulation sidewall  29  facing away from the frame glue  14 , the first encapsulation sidewall  29  adheres to the second substrate  16  through the second adhesive layer  30 . On the sides of the liquid crystal cell  10  other than the bonding side  21 , the first encapsulation sidewall  29  adheres to the fourth substrate  18  through the second adhesive layer  30  so that a fixed connection between the third substrate  17  and the fourth substrate  18  is implemented. 
     With continued reference to  FIG. 14 , optionally, the first encapsulation sidewall  29  and the third substrate  17  may be an integrated structure so that no glue is needed for the first encapsulation sidewall  29  to adhere to the third substrate  17  so as to connect the first encapsulation sidewall  29  to the third substrate  17  more firmly, which is not limited thereto. 
       FIG. 15  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIG. 15 , optionally, the connection structure  20  further includes a second encapsulation sidewall  31  disposed on the fourth substrate  18  and a third adhesive layer  32  disposed on a side of the second encapsulation sidewall  31  facing the third substrate  17 . The second encapsulation sidewall  31  is disposed on another side of the liquid crystal cell  10  other than the bonding side  21 , and the second encapsulation sidewall  31  is disposed on the side of the frame glue  14  facing away from the liquid crystal layer  13 . The second encapsulation sidewall  31  is connected to the third substrate  17  through the third adhesive layer  32 . 
     Exemplarily, as shown in  FIG. 15 , the connection structure  20  further includes the second encapsulation sidewall  31  and the third adhesive layer  32 . The second encapsulation sidewall  31  is disposed on the sides of the liquid crystal cell  10  other than the bonding side  21 . The second encapsulation sidewall  31  adheres to the third substrate  17  through the third adhesive layer  32 , thereby further improving firmness of a connection between the third substrate  17  and the fourth substrate  18 . In addition, the second encapsulation sidewall  31  is added so that encapsulation tightness can be further improved, thereby further reducing an influence of a harsh external environment on the performance of the liquid crystal antenna. 
     With continued reference to  FIG. 15 , optionally, the second encapsulation sidewall  31  and the fourth substrate  18  may be an integrated structure so that no glue is needed for the second encapsulation sidewall  31  to adhere to the fourth substrate  18  so as to connect the second encapsulation sidewall  31  to the fourth substrate  18  more firmly, which is not limited thereto. 
     It is to be noted that in the case where the first encapsulation sidewall  29  and the third substrate  17  are the integrated structure and the second encapsulation sidewall  31  and the fourth substrate  18  are the integrated structure, the third substrate  17  and the fourth substrate  18  may be combined in a manner of sealing and nesting each other. Thus, sealing performance is improved and no first adhesive layers  27  need be disposed between the third substrate  17  and the first substrate  15  and between the second substrate  16  and the fourth substrate  18 , thereby avoiding the influence of the first adhesive layer  27  on the radio frequency signal, reducing the additional loss of the radio frequency signal, and improving the performance of the liquid crystal antenna. In addition, the encapsulation structure is an overall structure viewed from the outside, the structure is more reliable, and an overall space occupied is smaller (full encapsulation). 
       FIG. 16  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIGS. 15 and 16 , optionally, the second encapsulation sidewall  31  is disposed on a side of the first encapsulation sidewall  29  facing the frame glue  14 . Alternatively, the second encapsulation sidewall  31  is disposed on the side of the first encapsulation sidewall  29  facing away from the frame glue  14 . 
     Exemplarily, as shown in  FIG. 15 , the second encapsulation sidewall  31  may be disposed on the side of the first encapsulation sidewall  29  facing away from the frame glue  14  so that the third substrate  17  and the fourth substrate  18  may be combined in the manner of sealing and nesting each other. 
     In other embodiments, as shown in  FIG. 16 , the second encapsulation sidewall  31  may also be disposed on the side of the first encapsulation sidewall  29  facing the frame glue  14 . Thus, the third substrate  17  and the fourth substrate  18  may be combined in the manner of sealing and nesting each other, and the engaging position may also be formed by the first encapsulation sidewall  29  and the second encapsulation sidewall  31  with the liquid crystal cell  10  so that the position of the liquid crystal cell  10  is more accurate and a nesting structure is more fixed. 
       FIG. 17  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIG. 17 , optionally, a first protrusion structure  33  is disposed on a side of the second substrate  16  facing the fourth substrate  18 , and a third groove  34  corresponding to the first protrusion structure  33  is disposed on the side of the fourth substrate  18  facing the second substrate  16 . A fourth adhesive layer  35  is disposed on a side of the first protrusion structure  33  facing away from the first substrate  15 , and the first protrusion structure  33  is connected to a surface of a side of the third groove  34  facing the second substrate  16  through the fourth adhesive layer  35 . 
     Exemplarily, as shown in  FIG. 17 , the first protrusion structure  33  and the corresponding third groove  34  are disposed on the second substrate  16  and the fourth substrate  18  respectively. The first protrusion structure  33  is accommodated in the third groove  34 . The first protrusion structure  33  and the third groove  34  can function as engaging positions so that the position of the liquid crystal cell  10  is more accurate. In addition, the relative movement between the second substrate  16  and the fourth substrate  18  can also be avoided, thereby helping improve the firmness of the connection between the second substrate  16  and the fourth substrate  18 . 
     Further, as shown in  FIG. 17 , the fourth adhesive layer  35  is further disposed between the first protrusion structure  33  and the third groove  34  so that the first protrusion structure  33  adheres to the third groove  34  through the fourth adhesive layer  35 , thereby further improving the firmness of the connection between the second substrate  16  and the fourth substrate  18 . 
     With continued reference to  FIG. 17 , optionally, a first gap  36  exists between a vertical projection of the third groove  34  on the second substrate  16  and a vertical projection of the microstrip line  11  on the second substrate  16 , where the first gap  36  has a distance D2 and D2≥200 μm. 
     As shown in  FIG. 17 , the first gap  36  is configured to exist between the vertical projection of the third groove  34  on the second substrate  16  and the vertical projection of the microstrip line  11  on the second substrate  16 , where the first gap  36  has the distance D2 and D2≥200 μm. Thus, a distance between the third groove  34  and the microstrip line  11  is relatively long in the direction parallel to the plane where the first substrate  15  is located so as to reduce an influence of the third groove  34  on the radio frequency signal transmitted on the microstrip line  11 , thereby helping improve the phase shift performance of the liquid crystal antenna. 
       FIG. 18  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIG. 18 , optionally, a second protrusion structure  37  is disposed on the side of the first substrate  15  facing the third substrate  17 , and a fourth groove  38  corresponding to the second protrusion structure  37  is disposed on the side of the third substrate  17  facing the first substrate  15 . A fifth adhesive layer  39  is disposed on a side of the second protrusion structure  37  facing away from the second substrate  16 , and the second protrusion structure  37  is connected to a surface of a side of the fourth groove  38  facing the first substrate  15  through a fifth adhesive layer  39 . 
     Exemplarily, as shown in  FIG. 18 , the second protrusion structure  37  and the corresponding fourth groove  38  are disposed on the first substrate  15  and the third substrate  17  respectively. The second protrusion structure  37  is accommodated in the fourth groove  38 . The second protrusion structure  37  and the fourth groove  38  can function as the engaging positions so that the position of the liquid crystal cell  10  is more accurate. In addition, the relative movement between the first substrate  15  and the third substrate  17  can be avoided, thereby helping improve firmness of the connection between the first substrate  15  and the third substrate  17 . 
     Further, as shown in  FIG. 18 , the fifth adhesive layer  39  is further disposed between the second protrusion structure  37  and the fourth groove  38  so that the second protrusion structure  37  adheres to the third groove  38  through the fifth adhesive layer  39 , thereby further improving the firmness of the connection between the first substrate  15  and the third substrate  17 . 
     With continued reference to  FIG. 18 , optionally, a second gap  40  exists between a vertical projection of the fourth groove  38  on the first substrate  15  and a vertical projection of the microstrip line  11  on the first substrate  15 , where the second gap  40  has a distance D3 and D3≥200 μm. 
     As shown in  FIG. 18 , the second gap  40  is configured to exist between the vertical projection of the fourth groove  38  on the first substrate  15  and the vertical projection of the microstrip line  11  on the first substrate  15 , where the second gap  40  has the distance D3 and D3≥200 μm. Thus, a distance between the fourth groove  38  and the microstrip line  11  is relatively long in the direction parallel to the plane where the first substrate  15  is located so as to reduce an influence of the fourth groove  38  on the radio frequency signal transmitted on the microstrip line  11 , thereby helping improve the phase shift performance of the liquid crystal antenna. 
     It is to be noted that  FIG. 17  merely illustrates an example in which the first protrusion structure  33  and the corresponding third groove  34  are disposed on the second substrate  16  and the fourth substrate  18  respectively, and the first protrusion structure  33  is accommodated in the third groove  34 ; and  FIG. 18  merely illustrates an example in which the second protrusion structure  37  and the corresponding fourth groove  38  are disposed on the first substrate  15  and the third substrate  17  respectively, and the second protrusion structure  37  is accommodated in the fourth groove  38 , which are not limited thereto. In other embodiments, the first protrusion structure  33  and the corresponding third groove  34  may be disposed on the second substrate  16  and the fourth substrate  18  respectively, and at the same time, the second protrusion structure  37  and the corresponding fourth groove  38  may be disposed on the first substrate  15  and the third substrate  17  respectively so that the position of the liquid crystal cell  10  is more accurate and the encapsulation firmness is further improved. Those skilled in the art may perform setting according to the actual requirements. 
       FIG. 19  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIG. 19 , optionally, the connection structure  20  includes a third encapsulation sidewall  41  disposed on the fourth substrate  18  and around the liquid crystal cell  10 ; and the third substrate  17  at least partially overlaps the third encapsulation sidewall  41  along a thickness direction of the third substrate  17 . 
     Exemplarily, as shown in  FIG. 19 , the connection structure  20  includes the third encapsulation sidewall  41  disposed around the liquid crystal cell  10  so that the whole liquid crystal cell  10  is encapsulated in a closed space formed by the third substrate  17 , the fourth substrate  18  and the third encapsulation sidewall  41 . In this case, the third encapsulation sidewall  41  is disposed on a side of the bonding connection region  28  facing away from the frame glue  14 . Thus, the overall encapsulation of the liquid crystal antenna is implemented, and in addition, the sealing degree of the encapsulation can be further improved, thereby further reducing the influence of the harsh external environment on the performance of the liquid crystal antenna. 
     With continued reference to  FIG. 19 , optionally, the third encapsulation sidewall  41  and the fourth substrate  18  are the integrated structure so that the third substrate  17  and the fourth substrate  18  can be combined directly. Thus, the sealing performance is improved and no first adhesive layers  27  need be disposed between the third substrate  17  and the first substrate  15  and between the second substrate  16  and the fourth substrate  18 , thereby avoiding the influence of the first adhesive layer  27  on the radio frequency signal, reducing the additional loss of the radio frequency signal, and improving the performance of the liquid crystal antenna. In addition, the encapsulation structure is the overall structure viewed from the outside, the structure is more reliable, and the overall space occupied is smaller (the full encapsulation). 
     With continued reference to  FIG. 19 , optionally, the connection structure  20  further includes a third adhesive layer  42  disposed on a side of the third encapsulation sidewall  41  facing the third substrate  17 . The third encapsulation sidewall  41  is connected to the third substrate  17  through the third adhesive layer  42 . 
     Exemplarily, as shown in  FIG. 19 , the connection structure  20  includes the third encapsulation sidewall  41  and the third adhesive layer  42 . The third encapsulation sidewall  41  adheres to the third substrate  17  through the third adhesive layer  42 , thereby fixing the third substrate  17 , the fourth substrate  18 , and the liquid crystal cell  10  together and implementing the overall encapsulation of the liquid crystal antenna. 
       FIG. 20  is a sectional view showing part of another liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIG. 20 , optionally, the third encapsulation sidewall  41  includes an engaging portion  411  disposed around the third substrate  17 . 
     Exemplarily, as shown in  FIG. 20 , the engaging portion  411  is disposed around the third substrate  17  so as to function as the engaging position so that the third substrate  17  is engaged by the engaging portion  411 . Thus, the third substrate  17  does not move relative to the fourth substrate  18  in the direction parallel to the plane where the first substrate  15  is located, thereby helping improve the firmness of a connection between the third substrate  17  and the fourth substrate  18  and improving the reliability of the overall liquid crystal antenna. 
     Optionally, as shown in  FIG. 20 , a surface of a side of the engaging portion  411  facing away from the first substrate  15  and a surface of a side of the third substrate  17  facing away from the first substrate  15  are disposed in the same plane. That is, the engaging portion  411  has an upper surface which is flush with an upper surface of the third substrate  17 , thereby making an appearance of the liquid crystal antenna more beautiful while functioning as the engaging position. 
     With continued reference to  FIGS. 19 and 20 , optionally, the bonding terminal  22  is disposed on a side of the third encapsulation sidewall  41  facing away from the liquid crystal cell  10 . A conductive structure  43  is disposed in the third encapsulation sidewall  41 . The bonding terminal  22  is electrically connected to the bonding connection region  28  through the conductive structure  43 . 
     Exemplarily, as shown in  FIGS. 19 and 20 , since the third encapsulation sidewall  41  is disposed on the side of the bonding connection region  28  facing away from the frame glue  14 , the bonding connection region  28  cannot be directly bonded to the FPC  23 . In this embodiment, the bonding terminal  22  is disposed on a surface of the side of the third encapsulation sidewall  41  facing away from the liquid crystal cell  10 , and the conductive structure  43  is disposed in the third encapsulation sidewall  41 . Thus, the bonding terminal  22  is electrically connected to the bonding connection region  28  through the conductive structure  43  so that the liquid crystal cell  10  receives a driving voltage signal provided by an external circuit  44 . 
     Specifically, as shown in  FIGS. 19 and 20 , the bonding terminal  22  is disposed on the bonding side  21  of the liquid crystal cell  10  and on the surface of the side of the third encapsulation sidewall  41  facing away from the liquid crystal cell  10 . The bonding terminal  22  is configured to be bonded to the FPC  23 , and the FPC  23  may be connected to the external circuit  44 , thereby implementing a connection between the bonding terminal  22  and the external circuit  44 . 
     Further, the microstrip line  11  is correspondingly connected to the driving voltage signal transmission line  24  which may be configured to extend to the bonding connection region  28 . The conductive structure  43  disposed in the third encapsulation sidewall  41  is welded to the driving voltage signal transmission line  24  extending to the bonding connection region  28  so as to implement a connection between the conductive structure  43  and the microstrip line  11 . In addition, the conductive structure  43  is connected to the bonding terminal  22  so that the microstrip line  11  receives the driving voltage signal provided by the external circuit  44 . Thus, the liquid crystal molecules  131  in the liquid crystal layer  13  are driven to deflect, the phase adjusted in the phase shift process of the radio frequency signal is controlled, and finally the beam-pointing direction of the radio frequency signal transmitted by the liquid crystal antenna is controlled. 
     It is to be noted that the external circuit  44  may be a driver integrated circuit (IC) or another IC. As shown in  FIGS. 19 and 20 , the external circuit  44  may be disposed on the surface of the side of the third encapsulation sidewall  41  facing away from the liquid crystal cell  10  or may be disposed at another position. Those skilled in the art may dispose the external circuit  44  according to the actual requirements, which is not limited in the embodiments of the present disclosure. 
     Optionally, the conductive structure  43  in the third encapsulation sidewall  41  may be implemented through a process of a rigid-flex board (like an FPC), which is not limited thereto. Those skilled in the art may perform setting according to the actual requirements. 
     In this embodiment, the bonding connection region  28  is disposed in the third encapsulation sidewall  41  and the microstrip line  11  is connected to the external circuit  44  through the conductive structure  43  in the third encapsulation sidewall  41  so that an overall encapsulation structure may be strengthened and the operation and use of the liquid crystal antenna are more reliable in a special environment. 
     With continued reference to  FIGS. 14 to 20 , optionally, the third substrate  17 , the fourth substrate  18 , and the connection structure  20  form a closed space  45  in which a vacuum environment exists. 
     As shown in  FIGS. 14 to 20 , the encapsulation and combination are performed by sealing and nesting the third substrate  17  and the fourth substrate  18  to each other so that the sealing performance of the liquid crystal antenna can be ensured. In this case, the third substrate  17 , the fourth substrate  18 , and the connection structure  20  form the closed space  45 . The closed space  45  is configured to be the vacuum environment and the liquid crystal cell  10  works in the vacuum environment so that the radio frequency signal is coupled in the vacuum environment with a smaller loss, thereby improving the performance of the liquid crystal antenna. 
     With continued reference to  FIGS. 8 to 13 , optionally, the connection structure  20  includes the encapsulant which covers the bonding connection region  28 . 
     The encapsulant is configured to cover the bonding connection region  28  so as to seal and protect the bonding connection region  28 , thereby improving the reliability of a connection between the bonding connection region  28  and the external circuit and further improving the reliability of the overall liquid crystal antenna. 
     Optionally, the third substrate  17  includes a glass substrate or a printed circuit board (PCB) substrate, and the fourth substrate  18  includes a glass substrate or a PCB substrate. 
     The third substrate  17  and/or the fourth substrate  18  may be the glass substrate. Relatively high manufacturing accuracy may be obtained through the glass substrate. In addition, the glass substrate has relatively high transparency so that the liquid crystal antenna can have a more beautiful appearance. 
     Optionally, the third substrate  17  and/or the fourth substrate  18  may also be the PCB substrate which is conducive to the arrangement of a circuit. The PCB substrate may include a high-frequency substrate which is a special circuit board having a relatively high electromagnetic frequency more than 1 GHz. The high-frequency substrate with the small loss is used so that a loss caused by the PCB substrate to the radio frequency signal can be effectively reduced, thereby improving using performance of an antenna. 
     It is to be noted that the third substrate  17  and/or the fourth substrate  18  are not limited to the preceding materials. In other embodiments, those skilled in the art can set the materials of the third substrate  17  and/or the fourth substrate  18  according to the actual requirements. For example, high-frequency substrates are used such as an FR-4 epoxy glass cloth laminate, a polytetrafluoroethylene plate, and a hot-pressed ceramic plate, or other flexible substrates are used, which is not limited in the embodiments of the present disclosure. 
     Optionally, the first substrate  15  includes the glass substrate, the second substrate  16  includes the glass substrate, the third substrate  17  includes the PCB substrate, and the fourth substrate  18  includes the PCB substrate. 
     The first substrate  15  and the second substrate  16  are glass substrates. Since the glass substrate has good light transmittance, when the first substrate  15  and the second substrate  16  are aligned to form a cell, the accurate alignment of the first substrate  15  and the second substrate  16  is facilitated, thereby ensuring phase shift performance of the liquid crystal cell  10 . 
     Further, the third substrate  17  and the fourth substrate  18  are PCB substrates. The PCB substrate has a lower dielectric constant and a smaller dielectric loss than the glass substrate. Therefore, the third substrate  17  and the fourth substrate  18  are the PCB substrates, which is conducive to improving the performance of the liquid crystal antenna applied in an ultra-high band. 
     It is to be noted that in the case there the third substrate  17  and the fourth substrate  18  are the PCB substrates, it is difficult to cut the PCB substrates. Therefore, the liquid crystal antenna can be prepared with small-size substrates so as to reduce times of cutting the PCB substrates. 
     With continued reference to  FIGS. 10 to 20 , optionally, the liquid crystal antenna provided by the embodiments of the present disclosure further includes the feed structure  46  coupled to the microstrip line  11 . The feed structure  46  is disposed on the side of the fourth substrate  18  facing away from the third substrate  17 . The vertical projection of the feed structure  46  on the fourth substrate  18  covers the vertical projection of the microstrip line  11  on the fourth substrate  18 . 
     Exemplarily, as shown in  FIGS. 10 to 20 , the feed structure  46  is disposed on the side of the fourth substrate  18  facing away from the third substrate  17  and the feed structure  46  is coupled to the microstrip line  11 . The feed structure  46  is configured to transmit the radio frequency signal to the microstrip line  11  and has the function of starting vibration. Along a thickness direction of the first substrate  15 , the feed structure  46  covers the microstrip line  11  so that the radio frequency signal transmitted on the feed structure  46  can be coupled to the microstrip line  11 . The deflection of the liquid crystal molecules  131  in the liquid crystal layer  13  is controlled so as to change the dielectric constant of the liquid crystal layer  13 . Thus, the phase shift of the radio frequency signal on the microstrip line  11  is implemented. 
     In this embodiment, the feed structure  46  is disposed on the side of the fourth substrate  18  facing away from the third substrate  17  so that during the preparation of the liquid crystal antenna, the microstrip line  11  may be formed on the second substrate  16 , the feed structure  46  may be formed on the fourth substrate  18 , and then the second substrate  16  and the fourth substrate  18  are combined. The preparation of the microstrip line  11  and the feed structure  46  can be implemented without the double-sided patterning process, resulting in the simple process, the small loss of consumable materials, the low cost, the high yield, and the easy mass production. 
     With continued reference to  FIGS. 1, 2, 7, and 8 , optionally, the feed structure  46  and the radiation electrode  19  are disposed in the same layer. 
     Exemplarily, as shown in  FIGS. 1, 2, 7, and 8 , the feed structure  46  and the radiation electrode  19  are disposed in the same layer, the feed structure  46  is coupled to the microstrip line  11 , and the feed structure  46  is configured to transmit the radio frequency signal to each microstrip line  11 . The feed structure  46  may be distributed in an arborescent shape and include multiple branches, and one branch provides the radio frequency signal for one microstrip line  11 . 
     As shown in  FIGS. 1, 2, 7 and 8 , the ground metal layer  12  includes a second hollow portion  122 . A vertical projection of the feed structure  46  on the first substrate  15  covers a vertical projection of the second hollow portion  122  on the first substrate  15 . The radio frequency signal transmitted by the feed structure  46  is coupled to the microstrip line  11  at the second hollow portion  122  of the ground metal layer  12 . The deflection of the liquid crystal molecules  131  in the liquid crystal layer  13  is controlled so as to change the dielectric constant of the liquid crystal layer  13 . Thus, the phase shift of the radio frequency signal on the microstrip line  11  is implemented. 
     With continued reference to  FIGS. 2 and 8 , optionally, the liquid crystal antenna provided by the embodiments of the present disclosure further includes a radio frequency signal interface  47  and a pad  48 . One end of the radio frequency signal interface  47  is connected to the feed structure  46  and fixed through the pad  48 . The other end of the radio frequency signal interface  47  is configured to be connected to the external circuit such as a coaxial cable connector so as to feed in the radio frequency signal. 
     In other embodiments, the feed structure  46  and the microstrip line  11  may also be disposed in the same layer and the feed structure  46  is coupled to the microstrip line  11 , which may be set by those skilled in the art according to the actual requirements and is not limited in the embodiments of the present disclosure. 
     With continued reference to  FIGS. 2, 4, and 8 to 20 , optionally, along the direction parallel to the first substrate  15 , a shortest distance between an edge of a vertical projection of the first substrate  15  on the third substrate  17  and an edge of the third substrate  17  is D4, and a shortest distance between an edge of a vertical projection of the first substrate  15  on the fourth substrate  18  and an edge of the fourth substrate  18  is D5, where D4≥0.2 mm and D5≥0.2 mm. 
     As shown in  FIGS. 2, 4, and 8 to 20 , in the direction parallel to the plane where the first substrate  15  is located, the third substrate  17  is configured to extend beyond the first substrate  15  by at least 0.2 mm, and the fourth substrate  18  is configured to extend beyond the first substrate  15  by at least 0.2 mm so that a space of at least 0.2 mm is provided on the side surface of the liquid crystal cell  10  to dispose the connection structure  20 . Thus, the contact area between the connection structure  20  and the third substrate  17  and the contact area between the connection structure  20  and the fourth substrate  18  are ensured, thereby ensuring the encapsulation firmness of the liquid crystal antenna. 
     It is to be noted that those skilled in the art may set materials of structures such as the microstrip line  11 , the ground metal layer  12 , the radiation electrode  19 , and the feed structure  46  according to the actual requirements. For example, the preceding structures may be made of copper (Cu) which is the most commonly used metal material in the antenna field and has excellent conductivity and a low cost. The use of the copper material can effectively reduce an energy loss due to a high resistance, thereby improving using performance of the liquid crystal antenna, which is not limited thereto. In other embodiments, metal materials such as silver and gold may also be used, which is not limited in the embodiments of the present disclosure. 
     With continued reference to  FIGS. 2 and 8 to 20 , optionally, the liquid crystal antenna provided by the embodiments of the present disclosure further includes a support  49  disposed between the first substrate  15  and the second substrate  16 . The support  49  is disposed between the first substrate  15  and the second substrate  16  so that the first substrate  15  and the second substrate  16  can be supported. Thus, during the alignment of the cell, uniformity of the thickness of the cell at each position is maintained using uniformity of the dimension of the support  49 . 
     With continued reference to  FIGS. 2 and 8 to 20 , optionally, the support  49  includes a photo spacer (PS). In other embodiments, the support  49  may also be a ball spacer (BS). Those skilled in the art may set the shape, number, position, and preparation process of the support  49  according to the actual requirements, which is not limited in the embodiments of the present disclosure. 
     With continued reference to  FIGS. 2 and 8 to 20 , optionally, the liquid crystal antenna provided by the embodiments of the present disclosure further includes an alignment layer  50  disposed on a side of the microstrip line  11  facing the liquid crystal layer  13 . The alignment layer  50  is also disposed on a side of the ground metal layer  12  facing the liquid crystal layer  13 . 
     As shown in  FIGS. 2 and 8 to 20 , the alignment layer  50  is disposed on the side of the microstrip line  11  facing the liquid crystal layer  13  and on the side of the ground metal layer  12  facing the liquid crystal layer  13  so that the alignment layer  131  provides a pretilt angle to each liquid crystal molecule  131  in the liquid crystal layer  13  for aligning the liquid crystal layer  13 . Thus, under the action of an applied electric field, the liquid crystal molecule  131  can be rapidly deflected in response to the electric field, thereby improving a response speed of the liquid crystal antenna. 
     Based on the same inventive concept, the embodiments of the present disclosure further provide a preparation method of a liquid crystal antenna for preparing any liquid crystal antenna provided by the preceding embodiments. The same or corresponding structure and the explanation of terms as those in the preceding embodiments will not be repeated here.  FIG. 21  is a flowchart of a preparation method of a liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIG. 21 , the method includes the steps described below. 
     In S 110 , a liquid crystal cell is prepared. The liquid crystal cell includes frame glue, a microstrip line, a ground metal layer, a liquid crystal layer, and a first substrate and a second substrate disposed opposite to each other. The microstrip line is disposed on a side of the second substrate facing the first substrate. The ground metal layer is disposed on a side of the first substrate facing the second substrate. The liquid crystal layer is disposed between the first substrate and the second substrate. The frame glue is disposed between the first substrate and the second substrate, and the frame glue is disposed around the liquid crystal layer. 
       FIG. 22  is a schematic diagram showing a process of a preparation method of a liquid crystal cell according to an embodiment of the present disclosure. As shown in  FIG. 22 , exemplarily, a ground metal layer  12  is prepared on a side of a first substrate  15 , a microstrip line  11  is prepared on a side of a second substrate  16 , and then a cell forming operation is performed on the first substrate  15  and the second substrate  16  so that a liquid crystal cell  10  is formed. A liquid crystal layer  13  is filled into the liquid crystal cell  10 . Frame glue  14  is disposed between the first substrate  15  and the second substrate  16 , and the frame glue  14  is disposed around the liquid crystal layer  13  to support the first substrate  15  and the second substrate  16  and provide an accommodation space for the liquid crystal layer  13 . 
     With continued reference to  FIG. 22 , optionally, after the liquid crystal cell  10  is formed, the first substrate  15  and the second substrate  16  may be further thinned to reduce an overall structure dimension, further meet needs for manufacturing a high-frequency antenna, and reduce a cross-sectional dimension of the liquid crystal antenna. 
     With continued reference to  FIG. 22 , optionally, when the liquid crystal cell  10  is formed, a support  49  may also be disposed between the first substrate  15  and the second substrate  16  so that the first substrate  15  and the second substrate  16  can be supported. Thus, during the alignment of the cell, uniformity of the thickness of the cell at each position is maintained using uniformity of the dimension of the support  49 . 
     In S 120 , a third substrate and a fourth substrate are provided and a radiation electrode is prepared on a side of the third substrate. 
     The radiation electrode is prepared on the side of the third substrate. Thus, the preparation of the radiation electrode can be implemented without a double-sided patterning process, resulting in a simple process, a small loss of consumable materials, a low cost, a high yield, and easy mass production. 
     In S 130 , the third substrate, the fourth substrate, and the liquid crystal cell are combined to form a liquid crystal antenna. The third substrate is disposed on a side of the first substrate facing away from the second substrate. The fourth substrate is disposed on a side of the second substrate facing away from the third substrate. The radiation electrode is disposed on a side of the third substrate facing away from the fourth substrate. The third substrate extends beyond an edge of the first substrate. The fourth substrate extends beyond edges of the second substrate on at least two sides. A connection structure is disposed between the third substrate and the fourth substrate. The connection structure is disposed on an outer side of the frame glue. 
     The third substrate, the fourth substrate, and the liquid crystal cell are combined to form the liquid crystal antenna. Along a direction parallel to the plane where the first substrate is located, the third substrate extends beyond the edge of the first substrate, and the fourth substrate extends beyond the edges of the second substrate on the at least two sides. Thus, a fixing space is provided on the outer side of the frame glue for the connection structure so that the connection structure fixes the third substrate, the fourth substrate, and the liquid crystal cell on a side surface of the liquid crystal cell. 
     Further, the connection structure is disposed around the frame glue. On the one hand, the liquid crystal cell, the third substrate, and the fourth substrate are adhered together from the side surface of the liquid crystal cell, thereby assembling the liquid crystal cell, the third substrate, and the fourth substrate. On the other hand, the overall encapsulation of the liquid crystal antenna can be implemented so that a microstrip line array structure in the liquid crystal cell can be effectively protected, thereby resisting an influence of a bad external environment, ensuring phase shift performance of the liquid crystal antenna, and improving reliability of the liquid crystal antenna. 
     It is to be noted that when the third substrate, the fourth substrate, and the liquid crystal cell are combined, the third substrate and the fourth substrate are respectively placed at corresponding positions of the liquid crystal cell, and then the connection structure is formed on sidewalls of the liquid crystal cell so that the connection structure is in contact with the sidewalls of the first substrate and the second substrate. Thus, a fixing force to the first substrate and the second substrate is increased and the liquid crystal cell does not move relative to the third substrate and the fourth substrate, thereby improving stability of the liquid crystal antenna. 
     For example, the sidewalls of the liquid crystal cell are directly coated with adhesive layers to manufacture the connection structure. In this case, the sidewalls of the liquid crystal cell may have a positioning function. Multiple coatings are directly performed along the sidewalls of the liquid crystal cell to form the connection structure, which is less difficult to manufacture and does not reduce an overall yield. 
     Further, the connection structure may also be in contact with the sidewall of the frame glue facing away from the liquid crystal layer so that the fixing force for the liquid crystal cell can be further increased. Thus, the liquid crystal cell does not shake between the third substrate and the fourth substrate, thereby improving the stability of the liquid crystal antenna. 
     It is to be understood that if the connection structure is manufactured by directly coating the sidewalls of the liquid crystal cell with adhesive layers, whether the connection structure is in contact with the sidewall of the frame glue facing away from the liquid crystal layer depends on a relative positional relationship between the frame glue and the first substrate and a relative positional relationship between the frame glue and the second substrate. When the frame glue is closer to the edges of the first substrate and the second substrate, it is easier for a connection structure  20  to be in contact with the sidewall of the frame glue facing away from the liquid crystal layer. 
     According to the preparation method of the liquid crystal antenna provided by the embodiments of the present disclosure, the liquid crystal cell, the third substrate, and the fourth substrate are respectively manufactured and combined to manufacture the liquid crystal antenna, and in addition, the connection structure is added around the liquid crystal cell, thereby implementing the overall encapsulation and reducing manufacturing difficulty of the liquid crystal antenna. The preparation method of the liquid crystal antenna may be compatible with the existing manufacturing process to the maximum extent. The manufacturing process is simple and mature, an overall manufacturing cost is reduced, and an encapsulation structure formed can also effectively protect the internal liquid crystal cell and reduce an influence of the harsh external environment on working performance of the liquid crystal antenna. 
     Optionally, one side of the liquid crystal cell is a bonding side, and the second substrate extends beyond the edge of the first substrate on the bonding side; and the second substrate includes a bonding connection region disposed on the bonding side of the liquid crystal cell, the bonding connection region is electrically connected to the microstrip line, and the bonding connection region is connected to an external circuit. 
     Before the third substrate, the fourth substrate, and liquid crystal cell are combined, the method further includes the step described below. 
     A first encapsulation sidewall is formed on a side of the third substrate facing away from the radiation electrode. 
     The step in which the third substrate, the fourth substrate, and the liquid crystal cell are combined to form the liquid crystal antenna includes the step described below. 
     The first encapsulation sidewall is connected to the second substrate and the fourth substrate separately through a second adhesive layer so that the liquid crystal antenna is formed. The first encapsulation sidewall is disposed around the frame glue, and the bonding connection region is disposed on a side of the first encapsulation sidewall facing away from the frame glue. 
     Exemplarily,  FIG. 23  is a schematic diagram showing a process of a preparation method of a liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIG. 23 , exemplarily, the ground metal layer  12  may be prepared on the side of the first substrate  15 , the microstrip line  11  may be prepared on the side of the second substrate  16 , and then the cell forming operation is performed on the first substrate  15  and the second substrate  16  so that the liquid crystal cell  10  is formed. The liquid crystal layer  13  is filled into the liquid crystal cell  10 . The frame glue  14  is disposed between the first substrate  15  and the second substrate  16 , and the frame glue  14  is disposed around the liquid crystal layer  13  to support the first substrate  15  and the second substrate  16  and provide the accommodation space for the liquid crystal layer  13 . 
     With continued reference to  FIG. 23 , optionally, after the liquid crystal cell  10  is formed, the first substrate  15  and the second substrate  16  may be further thinned to reduce the overall structure dimension, further meet the needs for manufacturing the high-frequency antenna, and reduce the cross-sectional dimension of the liquid crystal antenna. 
     With continued reference to  FIG. 23 , optionally, when the liquid crystal cell  10  is formed, the support  49  may also be disposed between the first substrate  15  and the second substrate  16  so that the first substrate  15  and the second substrate  16  can be supported. Thus, during the alignment of the cell, the uniformity of the thickness of the cell at each position is maintained using the uniformity of the dimension of the support  49 . 
     With continued reference to  FIG. 23 , the radiation electrode  19  may be prepared on a side of a third substrate  17 , and then a groove is made on a side of the third substrate  17  facing away from the radiation electrode  19  so that a first encapsulation sidewall  29  is formed. 
     With continued reference to  FIG. 23 , a feed structure  46  may be prepared on a side of a fourth substrate  18 , and then the third substrate  17 , the fourth substrate  18 , and the liquid crystal cell  10  are combined. Specifically, the first encapsulation sidewall  29  may be connected to the second substrate  16  and the fourth substrate  18  separately through a second adhesive layer  30  so that the liquid crystal antenna is formed. One side of the liquid crystal cell  10  is a bonding side  21 , and the second substrate  16  extends beyond an edge of the first substrate  15  on the bonding side  21 ; and the second substrate  16  includes a bonding connection region  28  disposed on the bonding side  21  of the liquid crystal cell  10 , the bonding connection region  28  is electrically connected to the microstrip line  11 , and the bonding connection region  28  is connected to the external circuit. The first encapsulation sidewall  29  is disposed around the frame glue  14  and the bonding connection region  28  is disposed on a side of the first encapsulation sidewall  29  facing away from the frame glue  14 . 
     With continued reference to  FIG. 23 , optionally, when the first substrate  15  and the second substrate  16  are thinned, a first protrusion structure  33  may be formed at the same time on a side of the second substrate  16  facing away from the microstrip line  11 . Of course, in other embodiments, a second protrusion structure may also be disposed on a side of the first substrate  15  facing away from the ground metal layer  12 , which is not limited in the embodiments of the present disclosure. 
     Further, after the feed structure  46  is prepared on the side of the fourth substrate  18 , a groove may also be made on a side of the fourth substrate  18  facing away from the feed structure  46  so as to form a third groove  34  corresponding to the first protrusion structure  33 . 
     With continued reference to  FIG. 23 , when the third substrate  17 , the fourth substrate  18 , and the liquid crystal cell  10  are combined, the first protrusion structure  33  adheres to the third groove  34  through a fourth adhesive layer  35  so as to improve firmness of a connection between the second substrate  16  and the fourth substrate  18 . 
     Optionally, before the third substrate, the fourth substrate, and the liquid crystal cell are combined, the method further includes the step described below. 
     A second encapsulation sidewall is formed on a side of the fourth substrate. 
     The step in which the third substrate, the fourth substrate, and the liquid crystal cell are combined to form the liquid crystal antenna includes the step described below. 
     The second encapsulation sidewall is connected to the third substrate through a third adhesive layer so that the liquid crystal antenna is formed. The second encapsulation sidewall is disposed on another side of the liquid crystal cell other than the bonding side, and the second encapsulation sidewall is disposed on a side of the frame glue facing away from the liquid crystal layer. 
     With continued reference to  FIG. 23 , the feed structure  46  may be prepared on the side of the fourth substrate  18 , and then the groove is made on the side of the fourth substrate  18  facing away from the feed structure  46  so that a second encapsulation sidewall  31  is formed. 
     Then the third substrate  17 , the fourth substrate  18 , and the liquid crystal cell  10  are combined. Specifically, the second encapsulation sidewall  31  is connected to the third substrate  17  through a third adhesive layer  32  so that the liquid crystal antenna is formed. The second encapsulation sidewall  31  is disposed on another side of the liquid crystal cell  10  other than the bonding side  21 , and the second encapsulation sidewall  31  is disposed on a side of the frame glue  14  facing away from the liquid crystal layer  13 . 
     The groove is made on the side of the third substrate  17  facing away from the radiation electrode  19  so that the first encapsulation sidewall  29  is formed. The groove is made on the side of the fourth substrate  18  facing away from the feed structure  46  so that the second encapsulation sidewall  31  is formed. Thus, the encapsulation and combination are performed by sealing and nesting the third substrate  17  and the fourth substrate  18  to each other so that sealing performance of the liquid crystal antenna is ensured. 
     Optionally, one side of the liquid crystal cell is the bonding side, and the second substrate extends beyond the edge of the first substrate on the bonding side; and the second substrate includes the bonding connection region disposed on the bonding side of the liquid crystal cell, the bonding connection region is electrically connected to the microstrip line, and the bonding connection region is connected to the external circuit. Before the third substrate, the fourth substrate, and the liquid crystal cell are combined, the method further includes the step described below. 
     A third encapsulation sidewall is formed on the side of the fourth substrate. 
     The step in which the third substrate, the fourth substrate, and the liquid crystal cell are combined to form the liquid crystal antenna includes the step described below. 
     The third encapsulation sidewall is connected to the third substrate so that the liquid crystal antenna is formed. The third encapsulation sidewall is disposed around the liquid crystal cell, and the third substrate at least partially overlaps the third encapsulation sidewall along a thickness direction of the third substrate. 
     Exemplarily,  FIG. 24  is a schematic diagram showing a process of a preparation method of another liquid crystal antenna according to an embodiment of the present disclosure. As shown in  FIG. 24 , the ground metal layer  12  may be prepared on the side of the first substrate  15 , the microstrip line  11  may be prepared on the side of the second substrate  16 , and then the cell forming operation is performed on the first substrate  15  and the second substrate  16  so that the liquid crystal cell  10  is formed. The liquid crystal layer  13  is filled into the liquid crystal cell  10 . The frame glue  14  is disposed between the first substrate  15  and the second substrate  16 , and the frame glue  14  is disposed around the liquid crystal layer  13  to support the first substrate  15  and the second substrate  16  and provide the accommodation space for the liquid crystal layer  13 . 
     With continued reference to  FIG. 24 , optionally, after the liquid crystal cell  10  is formed, the first substrate  15  and the second substrate  16  may be further thinned to reduce the overall structure dimension, further meet the needs for manufacturing the high-frequency antenna, and reduce the cross-sectional dimension of the liquid crystal antenna. 
     With continued reference to  FIG. 24 , optionally, when the liquid crystal cell  10  is formed, the support  49  may be disposed between the first substrate  15  and the second substrate  16  so that the first substrate  15  and the second substrate  16  can be supported. Thus, during the alignment of the cell, the uniformity of the thickness of the cell at each position is maintained using the uniformity of the dimension of the support  49 . 
     With continued reference to  FIG. 24 , the radiation electrode  19  may be prepared on the side of the third substrate  17 , the feed structure  46  may be prepared on the side of the fourth substrate  18 , and then the groove is made on the side of the fourth substrate  18  facing away from the feed structure  46  so that a third encapsulation sidewall  41  is formed. 
     Then the third substrate  17 , the fourth substrate  18 , and the liquid crystal cell  10  are combined. Specifically, the third encapsulation sidewall  31  is connected to the third substrate  17  so that the liquid crystal antenna is formed. The third encapsulation sidewall  41  is disposed around the liquid crystal cell  10 , and the third substrate  17  at least partially overlaps the third encapsulation sidewall  41  along a thickness direction of the third substrate  17 . One side of the liquid crystal cell  10  is the bonding side  21 , and the second substrate  16  extends beyond the edge of the first substrate  15  on the bonding side  21 ; and the second substrate  16  includes the bonding connection region  28  disposed on the bonding side  21  of the liquid crystal cell  10 , the bonding connection region  28  is electrically connected to the microstrip line  11 , and the bonding connection region  28  is connected to the external circuit. The bonding connection region  28  is disposed on a side of the third encapsulation sidewall  41  facing the frame glue  14 . 
     With continued reference to  FIG. 24 , optionally, when the fourth substrate  18  is prepared, a conductive structure  43  may be formed in the fourth substrate  18  through a process of a rigid-flex board (like an FPC). When the third substrate  17 , the fourth substrate  18 , and the liquid crystal cell  10  are combined, the conductive structure  43  is connected to the bonding connection region  28  by welding so as to implement the introduction of a driving voltage signal. 
     It is to be noted that the preceding are merely preferred embodiments of the present disclosure and the technical principles used therein. It is to be understood by those skilled in the art that the present disclosure is not limited to the embodiments described herein. For those skilled in the art, various apparent modifications, adaptations, combinations, and substitutions can be made without departing from the scope of the present disclosure. Therefore, while the present disclosure has been described in detail through the preceding embodiments, the present disclosure is not limited to the preceding embodiments and may include more equivalent embodiments without departing from the inventive concept of the present disclosure. The scope of the present disclosure is determined by the scope of the appended claims.