Patent Publication Number: US-2022238974-A1

Title: Phase shifter and antenna device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Chinese patent application No. 202120211716.1, filed on Jan. 26, 2021, the content of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to the field of wireless communication technology, and in particular to a phase shifter and an antenna device. 
     BACKGROUND 
     A phase shifter is an essential key component in communication applications and radar applications. Existing phase shifters mainly include a ferrite phase shifter, a semiconductor phase shifter, a Micro-Electro-Mechanical System (MEMS) phase shifter and the like, and the MEMS phase shifter has significant advantages in the aspects of insertion loss, power consumption, volume, cost and the like, such that the MEMS phase shifter attracts wide attention in the fields of radio communication, microwave technology and the like. 
     SUMMARY 
     Some embodiments of the present disclosure provide a phase shifter and an antenna device. 
     A first aspect of the present disclosure provides a phase shifter, which includes: 
     a substrate, a transmission line on the substrate and extending in a first direction, and a first reference electrode and a second reference electrode respectively on both sides of an extension direction of the transmission line, wherein 
     the transmission line includes a plurality of signal line segments which are arranged side by side and spaced apart from each other in the first direction, each of the plurality of signal line segments extends in the first direction, and a connection region is defined by a gap between any adjacent two of the plurality of signal line segments; 
     the phase shifter further includes at least one phase shifting unit, each phase shifting unit includes: a film bridge extending in the first direction, a connection electrode extending in a second direction, and an interlayer insulating layer on a side of the connection electrode distal to the substrate; 
     both ends of the connection electrode are connected with the first reference electrode and the second reference electrode, respectively, and an orthogonal projection of the connection electrode on the substrate is in the connection region; 
     both ends of the film bridge are respectively connected with adjacent two signal line segments that define the connection region; and 
     the connection electrode in each phase shifting unit is in a space formed by the film bridge and the substrate. 
     In an embodiment, the at least one phase shifting unit is a plurality of phase shifting units, and a distance between the film bridge and the connection electrode in each of the plurality of phase shifting units is a constant. 
     In an embodiment, the at least one phase shifting unit is a plurality of phase shifting units, and distances between film bridges and connection electrodes of at least some of the plurality of phase shifting units are different from each other. 
     In an embodiment, the distances between the film bridges and the connection electrodes in the plurality of phase shifting units are increased monotonically or decreased monotonically in the first direction. 
     In an embodiment, the at least one phase shifting unit is a plurality of phase shifting units, and overlapping areas of orthogonal projections of film bridges on the substrate and orthogonal projections of connection electrodes on the substrate in at least some of the plurality of phase shifting units are different from each other. 
     In an embodiment, the overlapping areas of the orthogonal projections of the film bridges on the substrate and the orthogonal projections of the connection electrodes on the substrate in the plurality of phase shifting units are decreased monotonically in the first direction. 
     In an embodiment, the distances between the film bridges and the connection electrodes in the plurality of phase shifting units are increased monotonically in the first direction. 
     In an embodiment, the overlapping areas of the orthogonal projections of the film bridges on the substrate and the orthogonal projections of the connection electrodes on the substrate in the plurality of phase shifting units are different from each other, dimensions in the second direction of the film bridges in the plurality of phase shifting units are equal to each other, and dimensions in the first direction of the connection electrodes in the plurality of phase shifting units are different from each other. 
     In an embodiment, the film bridge of the at least one phase shifting unit has a same dimension in the second direction, and the connection electrode of the at least one phase shifting unit has a dimension in the first direction that is increased monotonically or decreased monotonically. 
     In an embodiment, the first reference electrode, the second reference electrode, the connection electrode, and the transmission line are in a same layer and include a same material. 
     In an embodiment, the first reference electrode, the second reference electrode and the connection electrode have a one-piece structure. 
     In an embodiment, the film bridge includes a material of an aluminum-silicon alloy. 
     In an embodiment, each of the plurality of signal line segments includes a material of copper or gold. 
     In an embodiment, a distance between any adjacent two of the plurality of signal line segments is less than a distance between the first reference electrode and the second reference electrode. 
     In an embodiment, the film bridge and the interlayer insulating layer has a gap therebetween. 
     In an embodiment, the first reference electrode and the second reference electrode are spaced apart from the transmission line, respectively. 
     In an embodiment, the first reference electrode and the second reference electrode are parallel to the transmission line, respectively. 
     In an embodiment, the first direction and the second direction are perpendicular to each other. 
     In an embodiment, the interlayer insulating layer includes a material of silicon nitride or polyimide. 
     A second aspect of the present disclosure provides an antenna device, which includes the phase shifter according to any one of the foregoing embodiments of the first aspect of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram (e.g., a top view) showing a structure of a phase shifter according to an embodiment of the present disclosure; 
         FIG. 2  is a schematic diagram (e.g., a top view) showing a structure of a phase shifter according to an embodiment of the present disclosure; 
         FIG. 3  is a schematic diagram showing a structure of a phase shifting unit of the phase shifter shown in  FIG. 2 ; 
         FIG. 4  is a schematic cross-sectional view showing a structure of the phase shifter shown in  FIG. 3  taken along a line A-A; 
         FIG. 5  is a schematic cross-sectional view showing a structure of another phase shifter according to an embodiment of the present disclosure; 
         FIG. 6  is a schematic cross-sectional view showing a structure of another phase shifter according to an embodiment of the present disclosure; and 
         FIG. 7  is a schematic cross-sectional view showing a structure of another phase shifter according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     To enable one of ordinary skill in the art to better understand technical solutions of the present disclosure, the present disclosure will be further described in detail below with reference to the accompanying drawings and exemplary embodiments. 
     Unless defined otherwise, technical or scientific terms used herein should have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. The terms of “first”, “second”, and the like used herein are not intended to indicate any order, quantity, or importance, but rather are used for distinguishing one element from another. Further, the terms “a”, “an”, “the”, or the like used herein do not denote a limitation of quantity, but rather denote the presence of at least one element. The term of “comprising”, “including”, or the like, means that the element or item preceding the term contains the element or item listed after the term and its equivalent, but does not exclude the presence of other elements or items. The term “connected” or “coupled” is not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect connections. The terms “upper”, “lower”, “left”, “right”, and the like are used only to indicate relative positional relationships, and when the absolute position of an object being described is changed, the relative positional relationships may also be changed accordingly. 
     The inventors of the present inventive concept have found that, each switch (e.g., each metal film bridge) of a related MEMS phase shifter requires to be connected to a corresponding pad by one bias line, and the phase shifter is controlled by a plurality of bias voltages, resulting in a large number of bias lines and a large number of pins of a chip. In addition, a metal film bridge of the related MEMS phase shifter spans between two ground lines of a coplanar waveguide and is suspended (or hung) above a signal line of the coplanar waveguide, and in order to ensure that a transmission line has a proper characteristic impedance, a distance by which the metal film bridge spans between two ground lines is usually large, and is generally about hundreds of microns. A large length of the metal film bridge easily causes the metal film bridge to collapse, which is not beneficial to improving a yield rate of MEMS phase shifters. 
       FIG. 1  is a schematic diagram showing a structure of a phase shifter according to an embodiment of the present disclosure. As shown in  FIG. 1 , the phase shifter includes two ground lines  11 , a signal line  12 , and a plurality of phase shifting units, which are formed on a substrate (which is similar to a substrate  21  shown in  FIG. 2 ). The two ground lines  11  are arranged to be spaced apart from and in parallel with the signal line  12 , and the two ground lines  11  are symmetrically arranged on two sides of the signal line  12 , such that the two ground lines  11  and the signal line  12  together form a transmission line. Each phase shifting unit includes at least one metal film bridge  13 , and each metal film bridge  13  spans between the two ground lines  11  of a coplanar waveguide and is suspended above the signal line  12  thereof. Each metal film bridge  13  is connected to a corresponding pad  15  through a bias line (e.g., a wire for receiving a bias voltage)  14 . During a phase shift, a chip (e.g., a driver chip) inputs a bias signal (e.g., a bias voltage) to the pad  15 , and the bias line  14  connected to the pad  15  inputs the bias signal to the corresponding metal film bridge  13 . Accordingly, a bias voltage is formed between the metal film bridge  13 , which receives the bias signal, and the signal line  12 . Since a bridge floor portion of the metal film bridge  13  has a certain elasticity, the bridge floor portion of the metal film bridge  13  receiving the bias signal moves in a direction perpendicular to the signal line  12  under the bias voltage. That is, by inputting a direct current (DC) bias voltage to the metal film bridge  13 , a distance between the bridge floor portion of the metal film bridge  13  and the signal line  12  can be changed. Thus, a capacitance of a capacitor formed by the bridge floor portion of the metal film bridge  13  and the signal line  12  can be changed, and parameters of the transmission line can be changed, thereby realizing a phase shifting function.  FIG. 1  exemplarily shows five phase shifting units and five pads  15 , and the five phase shifting units are in one-to-one correspondence with the five pads  15 . The five phase shifting units of the phase shifter can realize phase shifting amounts of 22.5°, 22.5°, 45°, 90° and 180°, respectively, as shown in  FIG. 1 . 
     However, the inventors of the present inventive concept have found that, the number of bias lines  14  of the phase shifter shown in  FIG. 1  is large because each metal film bridge  13  in each phase shifting unit of the phase shifter shown in  FIG. 1  needs to be connected to the corresponding pad  15  through one bias line  14 . In addition, since each metal film bridge  13  spans between the two ground lines  11  of the coplanar waveguide and is suspended above the signal line  12  thereof, the distance by which each metal film bridge  13  spans between the two ground lines  11  is generally large. Therefore, during a manufacturing process of each metal film bridge  13 , the metal film bridge  13 , which is long, is easy to collapse, thereby reducing the yield rate of phase shifters. 
     To solve at least one of the above technical problems, other embodiments of the present disclosure provide a phase shifter and an antenna device. The phase shifter and the antenna device according to each of the other exemplary embodiments of the present disclosure will be described in further detail below with reference to the accompanying drawings. 
     In a first aspect,  FIG. 2  is a schematic diagram showing a structure of a phase shifter according to an embodiment of the present disclosure. As shown in  FIG. 2 , the phase shifter includes a substrate  21 , and a first reference electrode (e.g., a first ground line  22 ), a second reference electrode (e.g., a second ground line  22 ), a transmission line (e.g., a signal line  23 ), and at least one phase shifting unit M (e.g., two phase shifting units M are exemplarily shown in  FIG. 2 , but the present disclosure is not limited thereto), which are disposed on the substrate  21 . In the present embodiment, further description will be made by taking an example in which the first reference electrode and the second reference electrode are both the ground lines  22 , and the transmission line is the signal line  23 . 
     A plurality of phase shifting units in the phase shifter may have a same structure and a same function. The following description will be given by taking only one of the plurality of phase shifting units of the phase shifter as an example.  FIG. 3  is a schematic diagram showing a structure of one phase shifting unit M in the phase shifter shown in  FIG. 2 , and  FIG. 4  is a schematic cross-sectional view showing a structure of the phase shifting unit of the phase shifter shown in  FIG. 3  taken along a line A-A. As shown in  FIGS. 3 and 4 , in the present embodiment, the two ground lines  22  and signal line  23  that are formed on the substrate  21  together form a coplanar waveguide (CPW) transmission line. For example, the signal line  23  is disposed on the substrate  21  and extends in a first direction (e.g., the horizontal direction in  FIG. 2 or 3 ), and the two ground lines  22  are respectively disposed on the substrate  21 , on both sides of an extension direction (i.e., a lengthwise direction) of the signal line  23 , and spaced apart from the signal line  23 . The signal line  23  includes a plurality of signal line segments  23   a  arranged side by side and spaced apart from each other along the first direction. Each of the plurality of signal line segments  23   a  extends along the first direction, and a connection region CR is defined by a gap between any adjacent two of the plurality of signal line segments  23   a . With continued reference to  FIGS. 2, 3, and 4 , each phase shifting unit M includes a film bridge  24  extending in the first direction, a connection electrode  25  extending in a second direction (e.g., the vertical direction in  FIG. 2 or 3 ), and an interlayer insulating layer  26  disposed on a side of the connection electrode  25  distal to the substrate  21  (in other words, disposed between the connection electrode  25  and the film bridge  24 ). Both ends of the connection electrode  25  are connected to the two ground lines  22 , respectively, and an orthogonal projection of the connection electrode  25  on the substrate  21  is located within the connection region CR. Both ends of the film bridge  24  are connected to the adjacent two signal line segments  23   a  defining the connection region CR, respectively. The connection electrode  25  in each phase shifting unit M is located in a space formed by the film bridge  24  and the substrate  21 . Since both ends of the connection electrode  25  are connected to the two ground lines  22 , respectively, a potential on the connection electrode  25  is the same as a potential on the ground lines  22 . It should be noted that the phase shifter according to an embodiment of the present disclosure may be, for example, a Micro-Electro-Mechanical System (MEMS) phase shifter. 
     In the present embodiment, a material of the film bridge  24  may include an aluminum-silicon alloy, and a material of the interlayer insulating layer  26  may include silicon nitride or polyimide. Further, a material of the signal line  23  may include copper or gold. 
     It should be noted that, the phase shifter according to the present embodiment may further include a plurality of phase shifting units, each of which is shown in  FIG. 3 , and since the plurality of the phase shifting units have a same structure, detailed description thereof is not repeated here. 
     In the present embodiment, when the phase shifter disclosed herein is to operate, only a bias signal needs to be transmitted across the signal line  23  and the ground lines  22 , to generate a bias voltage (i.e., a driving voltage for the metal film bridge  24 ) between the ground lines  22  and the signal line  23 , so as to change a height of the metal film bridge  24  in a direction perpendicular to the substrate  21 , thereby changing a capacitance between the metal film bridge  24  and the connection electrode  25 . In this way, a distribution of capacitance of the coplanar waveguide transmission line is changed to make the coplanar waveguide transmission line become a slow wave system, thereby achieving the purpose of phase delay. Compared with the transmission of the bias signal by using a plurality of bias lines as shown in  FIG. 1 , the phase shifter shown in each of  FIGS. 2 to 4  transmit the bias signal through only the signal line  23 , and thus the number of transmission paths (e.g., the bias lines  14  as shown in  FIG. 1 ) of the bias signal are greatly reduced. Further, the metal film bridge  24  spans (or bridges) between adjacent two signal line segments  23   a  spaced apart from each other, and since the connection region CR defined by the adjacent two signal line segments  23   a  has a dimension in the first direction much smaller than a distance between the two ground lines  22  (in other words, the dimension of the connection region CR in the first direction is smaller than the distance between the two ground lines  22  in the second direction, or a distance between the adjacent two signal line segments  23   a  is smaller than the distance between the two ground lines  22 ), the metal film bridge  24  spans (or bridges) between the adjacent two signal line segments  23   a  by a small distance. Therefore, during a formation process of the metal film bridge  24 , the metal film bridge  24  is not easy to collapse, thereby improving the yield rate of phase shifters. 
     In some embodiments, the phase shifter may include a plurality of phase shifting units, and distances between the metal film bridges  24  and the connection electrodes  25  in the plurality of phase shifting units are equal to each other (in other words, a distance between the metal film bridge  24  and the connection electrode  25  in each phase shifting unit is a constant). In the present embodiment, the driving voltage Vp for the metal film bridge  24  may be calculated by the following formula: 
     
       
         
           
             
               Vp 
               = 
               
                 
                   
                     
                       2 
                       ⁢ 
                       k 
                     
                     
                       ε 
                       ⁢ 
                       ow 
                       ⁢ 
                       W 
                     
                   
                   ⁢ 
                   
                     
                       g 
                       2 
                     
                     ( 
                     
                       go 
                       - 
                       g 
                     
                     ) 
                   
                 
               
             
             , 
           
         
       
     
     where k is an elastic coefficient of the metal film bridge  24 , co is the vacuum dielectric constant, w is a width of the metal film bridge  24  (i.e., a dimension of the metal film bridge  24  in the second direction in  FIG. 2  or  FIG. 3 ), W is a width of the connection electrode  25  (i.e., a dimension of the connection electrode  25  in the first direction in  FIG. 2 or 3 ), w*W is a rightly opposite area (i.e., an overlapping area) between the metal film bridge  24  and the connection electrode  25 , go is an initial distance between the metal film bridge  24  and the connection electrodes  25 , and g is an actual distance (i.e., a current distance) between the metal film bridge  24  and the connection electrode  25 . It can be known from the formula of the driving voltage Vp for the metal film bridge  24  that, the driving voltage Vp for the metal film bridge  24  is related to the distance between the metal film bridge  24  and the connection electrode  25 . In the present embodiment, by setting the distances between the metal film bridges  24  and the connection electrodes  25  in the plurality of phase shifting units to be equal to each other, the metal film bridges  24  of the plurality of phase shifting units may have a same driving voltage. Therefore, during the operation of the phase shifter, the operation of the plurality of phase shifting units can be controlled at the same time by inputting a same bias signal to the signal line  23 , thereby reducing the number of the transmission paths of the bias signal. 
     In some embodiments, the phase shifter may include a plurality of phase shifting units, and the metal film bridges  24  and the connection electrodes  25  in at least some of the plurality of phase shifting units may have different distances therebetween, respectively. In the present embodiment, driving voltages for the metal film bridges  24  in the phase shifting units may be different from each other by setting the distances between the metal film bridges  24  and the connection electrodes  25  in the phase shifting units to be unequal to each other. Therefore, during the operation of the phase shifter, operating states of the respective phase shifting units may be controlled by sequentially providing the signal line  23  with bias signals (e.g., bias voltages) of different magnitudes, thereby achieving different phase shifting amounts. 
     In some embodiments, the phase shifter may include a plurality of phase shifting units. In the first direction, the distances between the metal film bridges  24  and the connection electrodes  25  in the plurality of phase shifting units are increased or decreased monotonically. In the present embodiment, an example in which the distances between the metal film bridges  24  and the connection electrodes  25  in the plurality of phase shifting units are increased monotonically is taken as an example for description.  FIG. 5  is a schematic cross-sectional diagram showing a structure of another phase shifter according to an embodiment of the present disclosure, and the present embodiment adopts a three-bit phase shifter (i.e., a phase shifter including three phase shifting units) as an example. As shown in  FIG. 5 , the phase shifter according to the present embodiment includes three phase shifting units. In the three phase shifting units of the phase shifter according to the present embodiment, the distances D1, D2 and D3 between the metal film bridges  24  and the connection electrodes  25  are increased in sequence (i.e., D1&lt;D2&lt;D3, as shown in  FIG. 5 ). Other structures of each phase shifting unit shown in  FIG. 5  are the same as those of the phase shifting unit M shown in each of  FIGS. 2, 3 and 4 . As described above, the driving voltage Vp for the metal film bridge  24  may be calculated by the following formula: 
     
       
         
           
             
               Vp 
               = 
               
                 
                   
                     
                       2 
                       ⁢ 
                       k 
                     
                     
                       ε 
                       ⁢ 
                       ow 
                       ⁢ 
                       W 
                     
                   
                   ⁢ 
                   
                     
                       g 
                       2 
                     
                     ( 
                     
                       go 
                       - 
                       g 
                     
                     ) 
                   
                 
               
             
             , 
           
         
       
     
     where k is the elastic coefficient of the metal film bridge  24 , co is the vacuum dielectric constant, w is the width of the metal film bridge  24 , W is the width of the connection electrode  25 , w*W is the rightly opposite area (i.e., the overlapping area) between the metal film bridge  24  and the connection electrode  25 , go is the initial distance between the metal film bridge  24  and the connection electrodes  25 , and g is the actual distance between the metal film bridge  24  and the connection electrode  25 . It can be known from the formula of the driving voltage Vp for the metal film bridge  24  that, the driving voltage Vp for the metal film bridge  24  is in direct proportion to the distance between the metal film bridge  24  and the connection electrode  25 . That is, the greater the distance between the metal film bridge  24  and the connection electrode  25  is, the greater the driving voltage is. In the present embodiment, the distances between the metal film bridges  24  and the connection electrodes  25  in different phase shifting units are set to be increased sequentially, such that the driving voltages for the metal film bridges  24  can be gradually increased. Therefore, during the operation of the phase shifter, as an amplitude of a bias signal input to the signal line  23  is gradually increased, the three phase shifting units are turned off (e.g., the distances between the metal film bridges  24  and the connection electrodes  25  in the three phase shifting units take their minimum values) in sequence, thereby achieving different phase shifting amounts. In the present embodiment, the phase shifter provided by the present disclosure can obtain different phase shifting amounts only by adjusting the magnitude of an amplitude of the bias signal on the signal line. It should be noted that, a case where the distances between the metal film bridges and the connection electrodes in the phase shifting units are decreased monotonically is contrary to the above case where the distances between the metal film bridges and the connection electrodes in the phase shifting units are increased monotonically, detailed description thereof is thus omitted. 
     In some embodiments, the phase shifter may include a plurality of phase shifting units, and overlapping areas of orthogonal projections of the metal film bridges  24  on the substrate  21  and orthogonal projections of the connection electrodes  25  on the substrate  21  in at least some of the plurality of phase shifting units are different from each other. In the present embodiment, the driving voltage Vp for the metal film bridge  24  is related to the overlapping area (i.e., w*W as described above) of the orthogonal projection of the metal film bridge  24  on the substrate  21  and the orthogonal projection of the connection electrode  25  on the substrate  21 , according to the formula of the driving voltage Vp for the metal film bridge  24 . In the present embodiment, by setting the overlapping areas of the orthogonal projections of the metal film bridges  24  on the substrate  21  and the orthogonal projections of the connection electrodes  25  on the substrate  21  in the phase shifting units to be different from each other, the driving voltages (e.g., the magnitudes of the amplitudes of the driving voltages) for the metal film bridges  24  in the phase shifting units can be different from each other, for achieving different phase shifting amounts. Therefore, by adjusting the magnitude of the amplitude of the bias signal input to the signal line  23  during the operation of the phase shifter, the operation of the plurality of phase shifting units can be controlled simultaneously, thereby reducing the number of the transmission paths of the bias signal. 
     In some embodiments, the phase shifter may include a plurality of phase shifting units, and the metal film bridges  24  thereof have a same dimension in the second direction. Further, the connection electrodes  25  thereof have dimensions increased monotonically or decreased monotonically in the first direction, and thus the rightly opposite areas (i.e., the overlapping areas) of the metal film bridges  24  and the connection electrodes  25  are increased monotonically or decreased monotonically. The embodiment of  FIG. 6  is explained by taking an example in which the dimensions of the connection electrodes  25  are decreased monotonically.  FIG. 6  is a schematic cross-sectional view showing a structure of another phase shifter according to an embodiment of the present disclosure, which is illustrated by taking a three-bit phase shifter as an example. As shown in  FIG. 6 , the phase shifter according to the present embodiment includes three phase shifting units. The three phase shifting units in the present embodiment have a structure in which only the rightly opposite areas (i.e., the overlapping areas) of the metal film bridges  24  and the connection electrodes  25  are decreased sequentially, while other configurations of each phase shifting unit shown in  FIG. 6  are the same as those of the phase shifting unit M shown in each of  FIGS. 2, 3, and 4 . As described above, the driving voltage Vp for the metal film bridge  24  may be calculated by the following formula: 
     
       
         
           
             
               Vp 
               = 
               
                 
                   
                     
                       2 
                       ⁢ 
                       k 
                     
                     
                       ε 
                       ⁢ 
                       ow 
                       ⁢ 
                       W 
                     
                   
                   ⁢ 
                   
                     
                       g 
                       2 
                     
                     ( 
                     
                       go 
                       - 
                       g 
                     
                     ) 
                   
                 
               
             
             , 
           
         
       
     
     where k is the elastic coefficient of the metal film bridge  24 , co is the vacuum dielectric constant, w is the width of the metal film bridge  24 , W is the width of the connection electrode  25 , w*W is the rightly opposite area (i.e., the overlapping area) between the metal film bridge  24  and the connection electrode  25 , go is the initial distance between the metal film bridge  24  and the connection electrodes  25 , and g is the actual distance between the metal film bridge  24  and the connection electrode  25 . It can be known from the formula of the driving voltage Vp for the metal film bridge  24  that, the driving voltage Vp for the metal film bridge  24  is in reverse proportion to the rightly opposite area w*W between the metal film bridge  24  and the connection electrode  25 . That is, the smaller the rightly opposite area w*W between the metal film bridge  24  and the connection electrode  25  is, the larger the required driving voltage is. In the present embodiment, the rightly opposite areas between the metal film bridges  24  and the connection electrodes  25  in different phase shifting units are set to be decreased sequentially, such that the driving voltages for the metal film bridges  24  can be increased sequentially. Therefore, during the operation of the phase shifter, as the bias signal input to the signal line is increased sequentially, the three phase shifting units are turned off in sequence, thereby achieving different phase shifting amounts. In the present embodiment, the phase shifter according to the present disclosure can achieve different phase shifting amounts by only adjusting the magnitude of the amplitude of the bias signal on the signal line. It should be noted that, a case where the dimensions of the connection electrodes  25  are increased monotonically is contrary to the above case where the dimensions of the connection electrodes  25  are decreased monotonically, and thus detailed description thereof is omitted herein. 
     Further,  FIG. 7  is a schematic cross-sectional view showing a structure of still another phase shifter according to an embodiment of the present disclosure, and the present embodiment is described by taking an example of a three-bit phase shifter. As shown in  FIG. 7 , the phase shifter according to the present embodiment includes three phase shifting units. The metal film bridges  24  in the three phase shifting units in the present embodiment have a same dimension in the second direction, while the connection electrodes  25  therein have dimensions in the first direction that are decreased sequentially. Further, the distances between the metal film bridges  24  and the connection electrodes  25  in the phase shifting units are increased in sequence, while other structures of each phase shifting unit shown in  FIG. 7  are the same as those of the phase shifting unit M shown in each of  FIGS. 2, 3 and 4 . It can be known from formula 
     
       
         
           
             Vp 
             = 
             
               
                 
                   
                     2 
                     ⁢ 
                     k 
                   
                   
                     ε 
                     ⁢ 
                     ow 
                     ⁢ 
                     W 
                   
                 
                 ⁢ 
                 
                   
                     g 
                     2 
                   
                   ( 
                   
                     go 
                     - 
                     g 
                   
                   ) 
                 
               
             
           
         
       
     
     of the driving voltage Vp for the metal film bridge  24  that, the driving voltage Vp for the metal film bridge  24  is in reverse proportion to the rightly opposite area (i.e., the overlapping area) w*W between the metal film bridge  24  and the connection electrode  25 , and is in direct proportion to the actual distance g between the metal film bridge  24  and the connection electrode  25 . That is, the smaller the rightly opposite area w*W between the metal film bridge  24  and the connection electrode  25  is and the larger the distance between the metal film bridge  24  and the connection electrode  25  is, the greater the required driving voltage is. In the present embodiment, the rightly opposite areas between the metal film bridges  24  and the connection electrodes  25  in different phase shifting units are set to be decreased sequentially and the distances between the metal film bridges  24  and the connection electrodes  25  in different phase shifting units are set to be increased sequentially, such that the driving voltages for the metal film bridges  24  can be increased gradually. Therefore, during the operation of the phase shifter, as the amplitude of the bias signal input to the signal line is increased gradually, the three phase shifting units are turned off sequentially, thereby achieving different phase shifting amounts. In the present embodiment, different phase shifting amounts can be obtained only by adjusting the magnitude of the amplitude of the bias signal on the signal line. 
     In some embodiments, the first reference electrode, the second reference electrode, the connection electrode, and the transmission line may be disposed in a same layer and are made of a same material (e.g., copper, aluminum, silver, or gold). In the present embodiment, during a manufacturing process of the phase shifter, the first reference electrode, the second reference electrode, the connection electrode and the transmission line can be simultaneously formed through one patterning process, thereby reducing steps of the process and the production cost. 
     In some embodiments, the first reference electrode, the second reference electrode, and the connection electrode have a one-piece structure. In the present embodiment, in the manufacturing process of the phase shifter, the first reference electrode, the second reference electrode and the connection electrode are formed through one patterning process, thereby further reducing steps for connecting the connection electrode with the reference electrodes and the production cost. 
     In a second aspect, embodiments of the present disclosure provide an antenna device, which includes the phase shifter as described in any one of the embodiments of  FIGS. 2 to 7 . 
     In a third aspect, embodiments of the present disclosure provide a method for manufacturing the phase shifter. Referring to  FIGS. 1 to 7 , the method may include the following steps. 
     The substrate is prepared. For example, the substrate may be a glass substrate, a ceramic substrate, a quartz substrate, or the like. 
     The transmission line is disposed on the substrate such that the transmission line extends in the first direction, and the first reference electrode and the second reference electrode are disposed on both sides of the extension direction (i.e., the lengthwise direction) of the transmission line. 
     The transmission line is formed to include the plurality of signal line segments arranged side by side and spaced apart from each other in the first direction, each of the plurality of signal line segments extends in the first direction, and a connection region is defined by a gap between any adjacent two of the plurality of signal line segments. 
     At least one phase shifting unit is further formed in the phase shifter, and each phase shifting unit includes: the film bridge extending in the first direction, the connection electrode extending in the second direction, and the interlayer insulating layer disposed on the side of the connection electrode distal to the substrate. 
     Both ends of the connection electrode are connected with the first reference electrode and the second reference electrode, respectively, and the orthogonal projection of the connection electrode on the substrate is located within the connection region. 
     Both ends of the film bridge are respectively connected with the adjacent two signal line segments that define the connection region. 
     The connection electrode in each phase shifting unit is positioned in a space formed by the film bridge and the substrate. 
     Further, the method may further include steps for forming other components as shown in any one of  FIGS. 1 to 7 . 
     The foregoing embodiments of the present disclosure may be combined with each other in a case of no explicit conflict. 
     It should be understood that the above embodiments are merely exemplary embodiments adopted to explain the principles of the present disclosure, and the present disclosure is not limited thereto. It will be apparent to one of ordinary skill in the art that various changes and modifications may be made therein without departing from the spirit and scope of the present disclosure, and such changes and modifications also fall within the scope of the present disclosure.