Patent Publication Number: US-11664606-B2

Title: Antenna structure and array antenna module

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 110100210, filed on Jan. 5, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to an antenna structure and an array antenna module, and more particularly, to a liquid crystal antenna structure and an array antenna module. 
     Description of Related Art 
     With the ever-increasing demand for the functions and performance of wireless devices, coupled with the lack of electromagnetic spectrum, the demand for adjustable operating frequencies of antennas is gradually increasing. At present, frequency modulated antennas generally use micro-electromechanical systems, diodes, field-effect transistor switches, etc. to achieve adjustable functions. However, the above adjustable methods are all discrete adjustments, which means that they may only hop between specific frequency points. In order for the frequency change of the modulation process to be continuous, a feasible method is to use the anisotropy of the liquid crystal material to realize electrical adjustment and achieve continuous modulation capability. 
     However, in the current antenna combination using a patch antenna and a liquid crystal layer, the liquid crystal layer is required to have a certain thickness, which will increase the manufacturing cost, while the response speed of the liquid crystal is also relatively slow, and the liquid crystal has more power consumption. 
     SUMMARY 
     The disclosure provides an antenna structure, which may have a relatively thin liquid crystal layer. 
     The disclosure provides an array antenna module, which has the antenna structure. 
     The antenna structure of the disclosure includes a patch antenna, a microstrip line, two first radiation assemblies, two second radiation assemblies, a liquid crystal layer, and a ground plane. The patch antenna includes two opposite edges. The microstrip line is connected to the patch antenna. The two first radiation assemblies are respectively disposed on two sides of the patch antenna. The patch antenna, the microstrip line, and the two first radiation assemblies are located on a first plane, and each of the first radiation assemblies includes multiple separated first conductors. The two second radiation assemblies are disposed under the two first radiation assemblies and located on a second plane, and each of the second radiation assemblies includes multiple separated second conductors. A projection of the two second radiation assemblies on the first plane, the two first radiation assemblies, and the two edges of the patch antenna collectively form two loops. The liquid crystal layer is disposed between the first plane and the second plane. The ground plane is disposed under the two second radiation assemblies. 
     In an embodiment of the disclosure, an extending direction of the two edges of the patch antenna extends toward a first extending direction of the microstrip line, and the loop has a long side extending toward the first extending direction of the microstrip line. 
     In an embodiment of the disclosure, a width of the first conductor in an extending direction of a short side is less than a width of the second conductor in the extending direction. 
     In an embodiment of the disclosure, the two second radiation assemblies are connected to each other through two conducting wires. The two second radiation assemblies are divided into an inner zone and two outer zones located at two sides of the inner zone by a second extending direction of the two conducting wires, and the second conductors of the second radiation assemblies are only located in the two outer zones. 
     In an embodiment of the disclosure, the first conductors are staggered from the second conductors. 
     In an embodiment of the disclosure, the antenna structure further includes a thin film transistor and multiple first circuits connected to the thin film transistor and the first conductors. The first conductors are electrically connected to the thin film transistor through the first circuits. The thin film transistor supplies a voltage to the first conductors to adjust a dielectric constant of the liquid crystal layer. 
     In an embodiment of the disclosure, the first circuits are respectively perpendicular to the connected first conductors. 
     In an embodiment of the disclosure, the antenna structure further includes multiple second circuits connected to the ground plane and the second conductors, and the second conductors are electrically connected to the ground plane through the second circuits. 
     In an embodiment of the disclosure, the second circuits are respectively perpendicular to the connected second conductors. 
     In an embodiment of the disclosure, the antenna structure further includes a first substrate and a second substrate which are disposed up and down, and separated from each other. The patch antenna, the microstrip line, and the two first radiation assemblies are disposed on the first substrate, and the two second radiation assemblies are disposed on the second substrate. The first plane is a surface of the first substrate facing the second substrate, and the second plane is a surface of the second substrate facing the first substrate. The liquid crystal layer is located between the first substrate and the second substrate. 
     In an embodiment of the disclosure, the ground plane is disposed on a surface of the second substrate away from the first substrate. 
     In an embodiment of the disclosure, the ground plane is disposed on a third substrate, and the ground plane is attached to the surface of the second substrate away from the first substrate. 
     In an embodiment of the disclosure, the antenna structure resonates in a frequency band, and a thickness of the liquid crystal layer is less than 0.005 times a wavelength of the frequency band. 
     The array antenna module of the disclosure includes multiple antenna structures, which are arranged in an array. 
     In an embodiment of the disclosure, the antenna structures include multiple first antenna structures. The microstrip lines of the first antenna structures have a variety of lengths. A phase difference of the first antenna structures is non-zero. Phases of the first antenna structures along the second extending direction are an arithmetic series. 
     In an embodiment of the disclosure, a difference between the lengths of any two adjacent ones of the microstrip lines of the first antenna structures is λg*(P/360), where λg is an effective wavelength of a feeding signal in the antenna structure, and P is a phase difference (°) between the two adjacent microstrip lines. 
     In an embodiment of the disclosure, the phase difference of the first antenna structures is P=(360*d*sin θ)/λ, where θ is a radiation angle, while λ is a radiation wavelength, and d is a distance between any two adjacent ones of the first antenna structures. 
     In an embodiment of the disclosure, the antenna structures further include multiple second antenna structures. A phase difference of the second antenna structures is 0. The first antenna structures and the second antenna structures are successively arranged along the second extending direction or the first extending direction, and an antenna radiation direction is adjusted by operating at different timings. 
     In an embodiment of the disclosure, a third extending direction is perpendicular to the first extending direction and the second extending direction. When the first antenna structures have radiation signals (ON), and the second antenna structures do not have the radiation signals (OFF), an angle is included between the antenna radiation direction and the third extending direction, and the angle is greater than 0 and less than 90 degrees. When the first antenna structures do not have the radiation signals (OFF), and the second antenna structures have the radiation signals (ON), the antenna radiation direction is parallel to the third extending direction. 
     In an embodiment of the disclosure, lengths of the microstrip lines of the first antenna structures are greater than lengths of the microstrip lines of the second antenna structures. 
     Based on the above, in the antenna structure of the disclosure, the two first radiation assemblies are respectively disposed on the two sides of the patch antenna, and the two second radiation assemblies are disposed under the two first radiation assemblies. The projection of the two second radiation assemblies on the first plane, the two first radiation assemblies, and the two edges of the patch antenna collectively form the two loops. The liquid crystal layer is disposed between the first plane and the second plane. The ground plane is disposed under the two second radiation assemblies. In the disclosure, the first conductors and the second conductors are disposed above and below the liquid crystal layer to generate a multi-capacitance path of a signal. In the conventional technology, the antenna structure using the liquid crystal layer determines a radiation frequency offset by the thickness of the liquid crystal layer, and thus the thick liquid crystal layer is required. In the antenna structure of the disclosure, through the above multi-capacitance path, a fringe radiation field of the patch antenna may change the radiation frequency according to the capacitance change generated by the multi-capacitance path. Therefore, the thickness of the liquid crystal layer of the antenna structure in the disclosure may be greatly reduced, thereby reducing the cost and power consumption. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic top view of an antenna structure according to an embodiment of the disclosure. 
         FIG.  2    is a schematic exploded view of the antenna structure of  FIG.  1   . 
         FIG.  3    is a schematic partial cross-sectional view of the antenna structure of  FIG.  1   . 
         FIG.  4    is a schematic partial cross-sectional view of an antenna structure according to an embodiment of the disclosure. 
         FIG.  5 A  is a view of a Far-field pattern of the antenna structure of  FIG.  1    on an XZ plane. 
         FIG.  5 B  is a view of a Far-field pattern of the antenna structure of  FIG.  1    on a YZ plane. 
         FIG.  6    is a view of a relationship between a frequency and S11 of the antenna structure of  FIG.  1    under different dielectric constants of a liquid crystal layer. 
         FIGS.  7 A,  7 C, and  7 E  are schematic views of various array antenna modules according to various embodiments of the disclosure. 
         FIGS.  7 B,  7 D, and  7 F  are respectively schematic views of an antenna radiation direction of the array antenna modules of  FIGS.  7 A,  7 C, and  7 E . 
         FIGS.  8 A and  8 B  are schematic views of an antenna radiation direction of an array antenna module at different voltages according to another embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS 
       FIG.  1    is a schematic top view of an antenna structure according to an embodiment of the disclosure.  FIG.  2    is a schematic exploded view of the antenna structure of  FIG.  1   . It should be noted that a size ratio of components in the figures is only for schematic illustration. 
     Referring to  FIGS.  1  to  3   , an antenna structure  100  of this embodiment includes a patch antenna  110 , a microstrip line  120 , two first radiation assemblies  130 , two second radiation assemblies  140 , a liquid crystal layer  150  ( FIG.  2   ), and a ground plane  155  ( FIG.  3   ). 
     As shown in  FIG.  2   , the patch antenna  110  includes two opposite edges  112 . The microstrip line  120  is connected to the patch antenna  110 . An extending direction of the two edges  112  of the patch antenna  110  extends toward a first extending direction D 1  of the microstrip line  120 . In this embodiment, the patch antenna  110  is rectangular. The antenna structure  100  radiates a frequency band, and a length of the edge  112  of the patch antenna  110  is close to ½ wavelength of the frequency band. 
     The two first radiation assemblies  130  are symmetrically disposed on two sides of the patch antenna  110 , respectively. Each of the first radiation assemblies  130  includes multiple separated first conductors  132 . The two second radiation assemblies  140  are disposed under the two first radiation assemblies  130 , and are symmetrical to the two sides of the patch antenna  110 . Each of the second radiation assemblies  140  includes multiple separated second conductors  142 . The first conductors  132  are at least partially staggered from the second conductors  142 . 
     In this embodiment, a shape and size of the first conductor  132  and the second conductor  142  are different, and a width W 1  of the first conductor  132  in an extending direction of a short side is less than a width W 2  of the second conductor  142  in the extending direction. The two second radiation assemblies  140  are connected to each other through two conducting wires  146 . As shown in  FIG.  2   , the two second radiation assemblies  140  are divided into an inner zone Z 1  and two outer zones Z 2  located at two sides of the inner zone Z 1  by a second extending direction D 2  of the two conducting wires  146 . In this embodiment, the second conductors  142  of the two second radiation assemblies  140  are only located in the two outer zones Z 2 . 
     The patch antenna  110 , the microstrip line  120 , and the two first radiation assemblies  130  are located on a first plane P 1 . The two second radiation assemblies  140  are disposed under the two first radiation assemblies  130  and located on a second plane P 2 . Specifically, the antenna structure  100  further includes a first substrate  160  and a second substrate  162  disposed up and down and separated from each other. The first substrate  160  and the second substrate  162  may be glass plates or plastic plates. Materials of the first substrate  160  and the second substrate  162  are not limited, as long as a tangent loss in an operating frequency band of an antenna is less than 0.05. 
     The patch antenna  110 , the microstrip line  120 , and the two first radiation assemblies  130  are disposed on the first substrate  160 , and the two second radiation assemblies  140  are disposed on the second substrate  162 . The first plane P 1  is a surface of the first substrate  160  facing the second substrate  162 , and the second plane P 2  is a surface of the second substrate  162  facing the first substrate  160 . The liquid crystal layer  150  is located between the first substrate  160  and the second substrate  162 , and located between the first plane P 1  and the second plane P 2 . The liquid crystal layer  150  is used as a modulation layer of a radiation frequency. 
     As shown in  FIG.  3   , the ground plane  155  is disposed under the two second radiation assemblies  140 . Specifically, in this embodiment, the ground plane  155  is disposed on a surface of the second substrate  162  away from the first substrate  160 . During manufacturing, the ground plane  155  may be directly plated on a bottom surface of the second substrate  162 , but a manufacturing method of the ground plane  155  is not limited thereto. 
       FIG.  4    is a schematic partial cross-sectional view of an antenna structure according to an embodiment of the disclosure. Referring to  FIG.  4   , a main difference between an antenna structure  100   a  of  FIG.  4    and  FIG.  3    is that in this embodiment, the ground plane  155  is disposed on a third substrate  164 , and the ground plane  155  and the third substrate  164  are attached to the surface (the bottom surface) of the second substrate  162  away from the first substrate  160 . In other words, the ground plane  155  may be formed on a top surface of the third substrate  164  and then attached to the bottom surface of the second substrate  162 . 
     Returning to  FIG.  2   , in this embodiment, the antenna structure  100  further includes a thin film transistor  136  and multiple first circuits  134  connected to the thin film transistor  136  and the first conductors  132 . The first circuits  134  are connected to each other, and the first conductors  132  are electrically connected to at least one thin film transistor  136  through the first circuits  134 . 
     In addition, the antenna structure  100  further includes multiple second circuits  144  connected to the ground plane  155  ( FIG.  3   ) and the second conductors  142 . The second circuits  144  are connected to each other, and the second conductors  142  are electrically connected to the ground plane  155  through the second circuits  144 . Specifically, a ground pad  156  which is electrically connected to the ground plane  155  below is disposed on the second plane P 2 . The ground pad  156  and the ground plane  155  are, for example, conducted through a structure such as a conductive via (not shown), and may also be directly connected to the external ground plane  155  by using a conductive material (such as a conductive tape). The second circuits  144  are connected to the ground pad  156  to be electrically connected to the ground plane  155  on the other surface. 
     The thin film transistor  136  supplies a voltage to the first conductors  132 , so that there is a voltage difference between the first conductors  132  and the second conductors  142  (equipotential to the ground plane  155 ). As a result, an electric field is formed to control an aligning direction of liquid crystal molecules in the liquid crystal layer  150 , so as to adjust a dielectric constant of the liquid crystal layer  150 . 
     It should be noted that the position, number, and size of the thin film transistor  136  are not limited by the drawing. In addition, the first conductor  132  and the second conductor  142  may be metal or non-metal conductors, and may also be transparent electrodes. The types of the first conductor  132  and the second conductor  142  are not limited thereto. 
     It should be noted that in this embodiment, the first circuits  134  are respectively perpendicular to the connected first conductors  132 , and the second circuits  144  are respectively perpendicular to the connected second conductors  142 . Such a design may enable a current direction (along an edge of the first conductor  132 ) on a surface of the first conductor  132  to be perpendicular to an extending direction of the connected first circuit  134 , and a current direction (along an edge of the second conductor  142 ) on a surface of the second conductor  142  to be perpendicular to an extending direction of the connected second circuit  144 , which may reduce an interference of a bias signal (a low frequency to 60 Hz) and a high frequency signal of an antenna (&gt;1 GHz). 
     Referring to  FIG.  1   , in this embodiment, a projection of the two second radiation assemblies  140  on the first plane P 1 , the two first radiation assemblies  130 , and the two edges  112  of the patch antenna  110  collectively form two loops. In this embodiment, a shape of the loop is a rectangle, and a long side of the loop extends toward the first extending direction D 1  of the microstrip line  120 . In an embodiment, the loop may also be a non-closed loop, and the shape of the loop is not limited by the drawing. 
     In the antenna structure  100  of this embodiment, the two first radiation assemblies  130  and the two second radiation assemblies  140  are disposed above and below the liquid crystal layer  150 . A projection of the second conductors  142  of the two second radiation assemblies  140  on the first plane P 1 , the first conductors  132  of the two first radiation assemblies  130 , and the two edges  112  of the patch antenna  110  collectively form two loops. Such a design may enable the first conductors  132  and the second conductors  142  to be alternately arranged up and down to generate a multi-capacitance path of a radiation signal, so that the signal resonates between the first conductors  132  and the second conductors  142  alternately arranged up and down. 
     Therefore, a fringe radiation field of the patch antenna  110  located in the center may change the radiation frequency due to a capacitance change generated by alternately stacking the first conductors  132  and the second conductors  142 . In other words, the antenna structure  100  of this embodiment is an antenna structure that generates radiation by using a resonance of high-frequency LC. 
     In the conventional technology, an antenna structure using a liquid crystal layer determines a radiation frequency offset by a thickness of the liquid crystal layer, and thus the thick liquid crystal layer is required. In this embodiment, the antenna structure  100  enhances an influence of the modulation of liquid crystal on a resonance of a radiator by using the multi-capacitance path, and achieves an adjustable capacitance by using an external voltage to change the dielectric constant of the liquid crystal layer  150 . Therefore, the antenna structure  100  of this embodiment does not need to change the radiation frequency by applying a high voltage to the thick liquid crystal layer, so that a thickness of the liquid crystal layer  150  may be greatly reduced, thereby reducing the cost and power consumption. 
     For example, the antenna structure  100  resonates in the frequency band, and a thickness T ( FIG.  2   ) of the liquid crystal layer  150  is less than 0.005 times the wavelength of the frequency band. Specifically, the thickness T ( FIG.  2   ) of the liquid crystal layer  150  required in this embodiment at 34 GHz is about 5 μm (0.0006λ 0 ). The thickness T of the liquid crystal layer  150  in this embodiment may be reduced by 14 times compared with the conventional technology. A driving voltage may be reduced from 90V to 9V, and the radiation frequency may be modulated by 8%. The antenna structure  100  may be made by general display manufacturing process. 
       FIG.  5 A  is a view of a Far-field pattern of the antenna structure of  FIG.  1    on an XZ plane.  FIG.  5 B  is a view of a Far-field pattern of the antenna structure of  FIG.  1    on a YZ plane. It should be noted that in  FIGS.  5 A and  5 B , a solid line refers to a radiation pattern of co-polarization, and a dashed line refers to a radiation pattern of cross-polarization. Referring to  FIG.  5 A  and  FIG.  5 B , the antenna structure  100  of  FIG.  1    has a good performance in the radiation pattern of co-polarization on the XZ plane and on the YZ plane, and the radiation pattern of cross-polarization is quite small, so that two curves has a high contrast in intensity. 
       FIG.  6    is a view of a relationship between a frequency and S11 of the antenna structure of  FIG.  1    under different dielectric constants of a liquid crystal layer. Referring to  FIG.  6   , in this embodiment, when an operating frequency is set to 21.3 GHz, a dielectric constant ε of the liquid crystal layer  150  is 2.4 in a state where the antenna structure  100  is not supplied with the voltage. When the X coordinate is 21.3 GHz, I1 is taken as an example for S11 (a reflection coefficient) corresponding to the Y coordinate. That I1 is close to −24 dB means that most of the fed radiant energy is radiated, so that only a small amount of energy is reflected, which has a good radiation performance. Therefore, the antenna structure  100  excites a radiation signal (ON) of 21.3 GHz. In a state where the voltage (9V) is supplied to the antenna structure  100 , the dielectric constant ε of the liquid crystal layer  150  is 3.3. When the X coordinate is 21.3 GHz, I1′ of S11 (the reflection coefficient) corresponding to the Y coordinate is close to −1 dB to −2 dB, which means that most of the fed radiant energy is reflected back to a feeding end, and the radiation performance is pretty poor. Therefore, the antenna structure  100  may be said to have no radiation signal (OFF) of 21.3 GHz at this time. 
     Conversely, if the operating frequency is defined as 19.6 GHz, the dielectric constant ε of the liquid crystal layer  150  is 3.3 in the state where the voltage (9V) is supplied to the antenna structure  100 . When the X coordinate is 19.6 GHz, I2 is taken as an example for S11 (the reflection coefficient) corresponding to the Y coordinate, which is close to −21 dB and means that most of the fed radiant energy is radiated, so that only a small amount of energy is reflected, which has a good radiation performance. Therefore, the antenna structure  100  may excite a radiation signal (ON) of 19.6 GHz. In the state where the antenna structure  100  is not supplied with the voltage, the dielectric constant ε of the liquid crystal layer  150  is 2.4. When the X coordinate is 19.6 GHz, I2′ of S11 (the reflection coefficient) corresponding to the Y coordinate is less than −1 dB, which means that most of the fed radiant energy is reflected back to the feeding end, and the radiation performance is pretty poor. Therefore, the antenna structure  100  may be said to have no radiation signal (OFF) of 19.6 GHz at this time. 
     In other words, the antenna structure  100  of this embodiment may change the dielectric constant ε of the liquid crystal layer  150  between 2.4 and 3.3 through no voltage or the voltage of 9V, thereby achieving an effect of changing the radiation frequency between 21.3 GHz and 19.6 GHz. 
     According to a capacitance formula, C=ε*A/D, where C is a capacitance, and ε is a dielectric constant. A is an area of a conductor, and D is a distance between the first plane P 1  and the second plane P 2 . When the dielectric constant ε changes, the capacitance changes accordingly. Furthermore, according to a frequency formula, f=1/(2π√(L*C)), where L is an inductance, and C is the capacitance. When the capacitance changes, the frequency also changes accordingly. Therefore, the antenna structure  100  of this embodiment changes the dielectric constant ε of the liquid crystal layer  150  by the multi-capacitance path, thereby achieving an effect of frequency modulation. 
     Compared with the conventional technology that requires the thick liquid crystal layer to achieve similar frequency modulation, the antenna structure  100  of this embodiment may have the thin liquid crystal layer  150 , and the frequency modulation may be achieved by applying a lower voltage. In addition, at 21.3 GHz, the antenna structure  100  of this embodiment may obtain a switching ratio of about 9% (a radiation efficiency of the radiation signal (OFF)/a radiation efficiency of the radiation signal (ON)), and the radiation frequency of about 8% may be modulated (a difference between 21.3 GHz and 19.6 GHz/21.3 GHz), which may be applied to array antennas, and may effectively achieve an effect of beamforming. 
       FIGS.  7 A,  7 C, and  7 E  are schematic views of various array antenna modules according to various embodiments of the disclosure.  FIGS.  7 B,  7 D, and  7 F  are respectively schematic views of an antenna radiation direction of the array antenna modules of  FIGS.  7 A,  7 C, and  7 E . Note that squares indicating phases shown in  FIGS.  7 A,  7 C, and  7 E  are only used to facilitate understanding, and do not denote actual components. In addition, where not shown in the figure, the microstrip lines of the antenna structures are connected together. The radiation signals enter the microstrip lines together, and after entering the microstrip lines of the same or different lengths, the same or different phases are generated. In addition,  FIGS.  7 B,  7 D, and  7 F  only show a pattern of the uppermost layer of the antenna structure. 
     Referring to  FIGS.  7 A and  7 B , in this embodiment, an array antenna module  10  includes multiple antenna structures  100  of  FIG.  1   , which are arranged in an array along the second extending direction D 2 . In this embodiment, an array of 1×4 is taken as an example, but the form of the array is not limited thereto. A third extending direction D 3  is perpendicular to the first extending direction D 1  and the second extending direction D 2 . The third extending direction D 3  is, for example, a normal direction of a substrate carrying the antenna structure  100 . In this embodiment, phases of the four antenna structures  100  are all 0, that is, a phase difference is 0, so that a radiation direction of the summed antennas is perpendicular to the first extending direction D 1  and the second extending direction D 2 , and parallel to the third extending direction D 3 . 
     Referring to  FIGS.  7 C and  7 D , in this embodiment, the antenna structures  100  of an array antenna module  10   a  include multiple first antenna structures  30 ,  32 ,  34 , and  36 . Microstrip lines  120   a,    120   b,    120   c,  and  120   d  of the first antenna structures  30 ,  32 ,  34 , and  36  have a variety of lengths L 2 , L 3 , L 4 , and L 5 . The lengths L 2 , L 3 , L 4 , and L 5  of the microstrip lines  120  are all greater than a length L 1  of the microstrip line  120  when the phase is 0, so that phases of the first antenna structures  30 ,  32 ,  34 , and  36  are non-zero, and a phase difference is non-zero. 
     In this embodiment, a phase change is adjusted by adjusting the lengths of the microstrip lines  120   a,    120   b,    120   c,  and  120   d.  A difference between the lengths of any two adjacent ones of the microstrip lines  120   a,    120   b,    120   c,  and  120   d  of the first antenna structures  30 ,  32 ,  34 , and  36  is λg*(P/360), where λg is an effective wavelength of a feeding signal in the antenna structure  100 . That is, the feeding signal is a wavelength when transmitted in media such as the patch antenna  110 , the first conductor  132 , the second conductor  142 , the first substrate  160 , the second substrate  162 , and the liquid crystal layer  150  in  FIG.  2   . P is a phase difference (°) between the two adjacent microstrip lines  120 . 
     In addition, along the second extending direction D 2 , phases A 1 , A 2 , A 3 , and A 4  of the first antenna structures  30 ,  32 ,  34 , and  36  are an arithmetic series. For example, the phases A 1 , A 2 , A 3 , and A 4  may be 20, 40, 60, and 80, but are not limited thereto. 
     As shown in  FIG.  7 D , the phase differences cause positions of radiation equiphase wavefronts (denoted by length) of the first antenna structures  30 ,  32 ,  34 , and  36  in the third extending direction D 3  to be different. The antenna radiation direction is affected by a normal direction of the radiation equiphase wavefronts, and is orthogonal to a line of multiple arrows in the figure (the dashed line in the figure). In addition, an angle θ 1  in included between the antenna radiation direction and the third extending direction D 3 , and the angle θ 1  is greater than 0 and less than 90 degrees. As the phase difference of the antenna structure  100  is different, the angle of the antenna radiation direction is also different. Specifically, the phase difference of the antenna structure  100  is P=(360*d*sin θ)/λ, where θ is a radiation angle, while λ is a radiation wavelength, and d is a distance between any two adjacent ones of the first antenna structures  30 ,  32 ,  34 , and  36 , for example, a distance between two centers of the two adjacent patch antennas  110  ( FIG.  1   ). A designer may obtain the desired radiation angle by controlling the above variables. 
     Referring to  FIGS.  7 E and  7 F , in an array antenna module  10   b  of this embodiment, phases B 1 , B 2 , B 3 , and B 4  of the first antenna structures  30 ,  34 ,  38 , and  39  along the second extending direction D 2  are the arithmetic series. For example, the phases B 1 , B 2 , B 3 , and B 4  may be 20, 60, 100, and 140, but are not limited thereto. A phase difference of the first antenna structures  30 ,  34 ,  38 , and  39  in  FIG.  7 E  is greater than a phase difference of the first antenna structures  30 ,  32 ,  34 , and  36  in  FIG.  7 C . Therefore, an angle θ 2  between the antenna radiation direction and the third extending direction D 3  in  FIG.  7 F  is greater than the angle θ 1  in  FIG.  7 D . 
     In light of the above, the designer may achieve an effect of adjusting the antenna radiation direction by configuring the antenna structure  100  with different phases. 
       FIGS.  8 A and  8 B  are schematic views of an antenna radiation direction of an array antenna module at different voltages according to another embodiment of the disclosure. Note that squares indicating phases shown in  FIGS.  8 A and  8 B  are only used to facilitate understanding, and do not denote the actual components. Where not shown in the figure, the microstrip lines of the antenna structures are connected together. The radiation signals enter the microstrip lines together, and after entering the microstrip lines of the same or different lengths, the same or different phases are generated. 
     Referring to  FIG.  8 A , in this embodiment, an array antenna module  10   c  includes multiple first antenna structures  30 ,  32 ,  34 , and  36 , and multiple second antenna structures  20 . Phases of the first antenna structures  30 ,  32 ,  34 , and  36  are non-zero (for example, 20, 40, 60, and 80), and have a phase difference. Phases of the second antenna structures  20  is 0 without a phase difference. Lengths of the microstrip lines  120  of the first antenna structures  30 ,  32 ,  34 , and  36  are greater than lengths of the microstrip lines  120  of the second antenna structures  20 . 
     The first antenna structures  30 ,  32 ,  34 , and  36 , and the second antenna structures  20  are successively arranged along the second extending direction D 2 , and the antenna radiation direction may be adjusted by operating at different timings. In an embodiment, the first antenna structures  30 ,  32 ,  34 , and  36 , and the second antenna structures  20  may also be successively arranged along the first extending direction D 1 . 
     Specifically, as shown in  FIG.  8 A , when the first antenna structures  30 ,  32 ,  34 , and  36  do not have the radiation signals (OFF) and the second antenna structures  20  have the radiation signals (ON), an antenna radiation direction of the antenna structure  20  is perpendicular to the first extending direction D 1  and the second extending direction D 2  as shown in  FIG.  7 B , and extends along the third extending direction D 3 . Specifically, in this embodiment, when the operating frequency is set to 21.3 GHz, the thin film transistors  136  ( FIG.  1   ) of the first antenna structures  30 ,  32 ,  34 , and  36  are supplied with the voltage, and when the thin film transistors  136  of the second antenna structures  20  are not supplied with the voltage, the antenna radiation direction that is perpendicular to the first extending direction D 1  and the second extending direction D 2 , and extends along the third extending direction D 3  may be obtained. 
     As shown in  FIG.  8 B , when the first antenna structures  30 ,  32 ,  34 , and  36  have the radiation signals (ON), and the second antenna structures  20  do not have the radiation signals (OFF), the angle θ 1  is included between the antenna radiation direction of the first antenna structures  30 ,  32 ,  34 , and  36 , and the third extending direction D 3  as shown in  FIG.  7 D . The angle θ 1  is greater than 0 and less than 90 degrees. Specifically, in this embodiment, when the operating frequency is set to 21.3 GHz, the thin film transistors  136  of the first antenna structures  30 ,  32 ,  34 , and  36  are not supplied with the voltage, and when thin film transistors  136  of the second antenna structures  20  are supplied with the voltage, the antenna radiation direction having the angle θ 1  included between the third extending direction D 3  may be obtained. 
     Of course, the angle of the antenna radiation direction varies according to the phase and antenna configuration. The designer may adjust the configuration of the antenna structure  100  and the switch settings of the antenna structure  100  according to requirements to control the phase difference (with/without phase difference), and then change the angle of the antenna radiation direction to achieve an effect of antenna radiation beam switching. 
     Based on the above, in the antenna structure of the disclosure, the two first radiation assemblies are respectively disposed on the two sides of the patch antenna, and the two second radiation assemblies are disposed under the two first radiation assemblies. The projection of the two second radiation assemblies on the first plane, the two first radiation assemblies, and the two edges of the patch antenna collectively form the two loops. The liquid crystal layer is disposed between the first plane and the second plane. The ground plane is disposed under the two second radiation assemblies. In the disclosure, the first conductors and the second conductors are disposed above and below the liquid crystal layer to generate the multi-capacitance path of the signal. In the conventional technology, the antenna structure using the liquid crystal layer determines the radiation frequency offset by the thickness of the liquid crystal layer, and thus the thick liquid crystal layer is required. In the antenna structure of the disclosure, through the above multi-capacitance path, the fringe radiation field of the patch antenna may change the radiation frequency according to the capacitance change generated by the multi-capacitance path. Therefore, the thickness of the liquid crystal layer of the antenna structure in the disclosure may be greatly reduced, thereby reducing the cost and power consumption.