Abstract:
A dielectric phase shifter comprises a cavity having an elongated receiving space, a phase shifting circuit disposed inside the receiving space, and a dielectric element slidably mounted in the receiving space and parallel with the phase shifting circuit. A rail is disposed on an inner wall of the cavity for preventing contact between the movable dielectric element and the phase shifting circuit. By providing a number of rails between the phase shifting circuit and the dielectric element, direct contact between the dielectric element and a feeding network is prevented. As a result, no additional force will be imposed on the feeding network and reliability is enhanced. Moreover, wear of the feeding network and/or dielectric element during operation of the phase shifter is eliminated.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to technical field of communication components and more particularly, relates to a dielectric phase shifter. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the field of mobile communication network coverage, an electrical tilt antenna for abase station is one of important devices for realizing network coverage. In addition, a phase shifter is the most important component of the base station electrical tilt antenna. The quality of the phase shifter has direct influence on performance of the electrical tilt antenna, and has further influence on coverage quality of the network. As a result, it is manifest that the phase shifter plays a key role in the field of mobile base station antenna. 
         [0003]    For prior art phase shifters, there are two conventional means to realize phase shifting. One is achieved by changing the electrical length of a signal path inside the phase shifter, and the other one is achieved by moving dielectric material inside the phase shifter, this further changing transmission velocity of signal in the phase shifter, thereby continuous linear phase difference for the signal output from the phase shifter is being generated. As such, the phase shifting is realized. 
         [0004]    However, a prior art phase shifter realizing phase shifting by loading a dielectric element has the following problems. 
         [0005]    At first, the dielectric element directly contacts the feeding network and as a result, during long-term movement, friction will exist between the dielectric element and feeding network, thereby bringing influence on performance of circuit. 
         [0006]    At second, when the dielectric element contacts the feeding network, especially when the element is directly disposed on the feeding network, force will be imposed on the network. This not only jeopardizes structural reliability of the phase shifter, but also introduces passive inter-modulation product. 
       SUMMARY OF THE INVENTION 
       [0007]    The object of the present invention is to provide a dielectric phase shifter for overcoming the disadvantages of prior art phase shifters, and to improve electrical performance and physical features. 
         [0008]    To achieve the object, the following technical solution is provided. 
         [0009]    A dielectric phase shifter comprises a cavity having an elongated receiving space, a phase shifting circuit disposed inside the receiving space, and a dielectric element slidably mounted in the receiving space and parallel with the phase shifting circuit. A rail is disposed on an inner wall of the cavity for preventing contact between the movable dielectric element and phase shifting circuit. 
         [0010]    The rail is disposed on the inner wall of the cavity opposed to the dielectric element; the number of the rail disposed on the inner wall is one; and, a sliding groove is defined in the dielectric element at a location corresponding to the rail for realizing engagement between the rail and sliding groove. 
         [0011]    The rails are disposed on a pair of opposed inner walls of the cavity at two sides of the dielectric element; each of the inner wall is provided with the rail; and the dielectric element and phase shifting circuit are located at two sides of the rail. 
         [0012]    The phase shifting circuit includes a phase shifting conductor and a dielectric supporting member for securing the phase shifting conductor and cavity together. 
         [0013]    The dielectric supporting member is a circuit board; and the phase shifting conductor is printed on the circuit board. 
         [0014]    The phase shifting conductor is a metal plate. 
         [0015]    The receiving space extends inside the cavity. 
         [0016]    Furthermore, there may be more than one dielectric element inside the cavity. 
         [0017]    When there are two dielectric elements, each dielectric element is supported by the rail disposed on an inner wall of the cavity opposed to the dielectric element. 
         [0018]    When there are two dielectric elements, each dielectric element is supported by the rails disposed on a pair of inner walls of the cavity. 
         [0019]    Furthermore, there are two dielectric elements and two pairs of rails, which are disposed substantially parallel with each other; a holding groove is defined between the two pairs of rails for mounting the phase shifting circuit therein; and each dielectric element is supported by a pair of rails disposed on a pair of inner walls. 
         [0020]    Alternatively, there are two dielectric elements and two pairs of parallel rails respectively disposed on two inner walls located just over and below the phase shifting circuit; a sliding groove is defined in the dielectric element at a location corresponding to the rail for realizing engagement between the rail and sliding groove of the dielectric element. 
         [0021]    The present invention has the following advantageous effects when compared to prior art: 
         [0022]    At first, as there are a number of rails provided for the dielectric phase shifter of the invention, contact between the dielectric element and feeding network is prevented. In this case, the feeding network will not be imposed with additional external force, and reliability is high. Moreover, wear of the feeding network and/or dielectric element during operation is eliminated. 
         [0023]    At second, the dielectric phase shifter of the invention has the advantages of better electrical performance, high precision of phase shifting, high linearity, and less passive inter-modulation product. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  shows a structural view of a dielectric phase shifter according to a first embodiment of the present invention; 
           [0025]      FIG. 2  shows a cross-sectional view of the dielectric phase shifter of  FIG. 1  along line A-A; 
           [0026]      FIG. 3  shows a structural view of a dielectric phase shifter of  FIG. 1  according to another embodiment of the present invention; 
           [0027]      FIG. 4  shows a structural view of a dielectric phase shifter of  FIG. 1  according to a further embodiment of the present invention; 
           [0028]      FIG. 5  shows a structural view of a dielectric phase shifter according to a second embodiment of the present invention; 
           [0029]      FIG. 6  shows a cross-sectional view of the dielectric phase shifter of  FIG. 5  along line A-A; and 
           [0030]      FIG. 7  shows a cross-sectional view of a cavity of another dielectric phase shifter according to the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    The present invention will be further described below with reference to accompanied drawings and exemplary embodiments. Here, identical numerals represent the identical components. In addition, detailed description of prior art will be omitted if it is unnecessary for illustration of the features of the present invention. 
       First Embodiment 
       [0032]    As shown in  FIGS. 1-3 , a dielectric phase shifter  1  of the present invention includes a cavity  11 , a phase shifting circuit  12 , a dielectric element  13 , and several rails  14 . 
         [0033]    As shown in  FIG. 1 , the cavity  11  is made of metal using extrusion or die-casting process. The cavity  11  has five enclosing walls  110  including four of which are disposed around the cavity  11  along a longitudinal direction, and a receiving space  111  defined by said five enclosing walls  110 . One end of the cavity  11  is not provided with any enclosing walls  110  to form an opened end in advance. In addition, the receiving space  111  runs inside the cavity  11  to facilitating installation of the phase shifting circuit  12 , dielectric element  13  and other components. Moreover, it also facilitates straight movement of the dielectric element  13  along the longitudinal direction of the cavity  11  when imposed by force. Of course, two ends of the cavity  11  along the longitudinal direction may not be provided with any enclosing walls to form opened ends in advance. In other embodiments, the cavity  11  may also be formed by a grooved body (not shown), at least one end of which is not provided with any enclosing wall to in advance define an opened end, and a cover (not shown) for covering the grooved body. 
         [0034]    The phase shifting circuit  12  includes a phase shifting conductor  121  and a dielectric supporting member  120  for securing the phase shifting conductor  121  and cavity  11  together. 
         [0035]    Here, the dielectric supporting member  120  may be a circuit board  120  on which the phase shifting conductor  121  is printed. The circuit board  120  may be a single-layered PCB. That is, the phase shifting conductor  121  may be printed on one side of the PCB  120 . Alternatively, it may also be a double-layered PCB. In this case, the phase shifting conductor  121  may be printed on both sides of the PCB  120  (See  FIG. 4 ). The phase shifting conductors  121  located on both sides of the double-layered PCB  120  may be connected with each other by a number of through holes (not shown). One side of the circuit board  120  close to an enclosing wall  110  is provided with a metal welded member  16  welded on the same enclosing wall  110 , thus securing the circuit board  120  (the phase shifting circuit  12 ) into the cavity  11 . 
         [0036]    In theory, when the two sides of the PCB  120  are equipped with the phase shifting conductors  121  between which no interference is present, for the phase shifter  1 , it may be deemed that the receiving space  11 , dielectric element  13 , and phase shifting circuit  12  are divided by the PCB  120  into two independent parts, thus defining two independent sub-phase shifters each is able to perform phase shifting to signals passed there through. 
         [0037]    In other embodiments, the phase shifting conductor may be a metal conductor of for example metal bar or metal sheet. The metal conductor constitutes the phase shifting conductor following principles of phase shifting circuit, and the phase shifting conductor is secured in the receiving space of the cavity by the dielectric supporting member, as illustrated in a second embodiment. 
         [0038]    It is known that any dielectric material will cause phase shifting to fluctuation occurred in itself. The cavity  11  of the phase shifter  1  of the present invention accommodates the dielectric element  13  capable of moving straight along the longitudinal direction of the cavity  11 . Equivalent dielectric constant of the cavity  11  may be varied by moving the dielectric element  13 , hence changing transmission speed of signals inside the phase shifter  1 , and thereby continuous linear phase difference for the signal output from the phase shifter  1  being generated. As such, the phase shifting is realized. 
         [0039]    The dielectric element  13  of the present invention is preferably elongated and may be made of kinds of materials. Moreover, dielectric constant of the element  13  ε r &gt;1.0. In addition to higher dielectric constant, the material of the dielectric element  13  is further required to have low loss angle tangent characteristics. Furthermore, to obtain higher equivalent dielectric constant for the phase shifter  1 , the receiving space should be filled by the dielectric element  13  to extend as much as possible. 
         [0040]    In case that the dielectric element  13  is in direct contact with the phase shifting circuit  12 , for example when the element  13  is directly positioned on the phase shifting circuit  12 , external force will be imposed on the phase shifting circuit  12 . In addition, wear will be caused to the circuit  12  and/or element  13  during movement of the element  13 . 
         [0041]    Referring to  FIGS. 2-3 , to avoid above problems, at least one rail  14  is disposed inside the cavity  11  of the dielectric phase shifter  1  of the present invention to generate a gap between the dielectric element  13  and phase shifting circuit  12 , thereby preventing direct contact between the dielectric element  13  and phase shifting circuit  12 . 
         [0042]    The rail  14  is of an elongated shape, disposed on an inner wall of an enclosing wall  110  along the longitudinal direction of the cavity  11 , and extends along the same direction of the cavity  11 . The rail  14  may either be integrally formed with the enclosing wall  110  of the cavity  11  or be formed on the inner wall of the enclosing wall  110  of the cavity  11  after formation of the cavity  11 . 
         [0043]    When there is only one dielectric element  13 , the rail  14  is disposed on an inner wall of an enclosing wall  110  opposite to the dielectric element  13 . As used herein, the enclosing wall  110  opposite to the dielectric element  13  means the one which faces a wider end surface of the dielectric element  13 . In other words, this enclosing wall  110  is the one located just over or below the element  13 . A sliding groove  139  is defined in the dielectric element  13  at a location corresponding to the rail  14 . The rail  14  locates inside the sliding groove  139  of the dielectric element  13  such that the rail  14  is mounted inside the element  13 . By this manner, the dielectric element  13  moves straight on the rail  14 . In addition, during movement of the dielectric element  13 , it will not contact the phase shifting circuit  12  and accordingly, reliability of the phase shifter  1  is improved. The rail  14  may have a cross section of circle, triangle, rectangular, trapezoid or other polygon, as can be configured upon requirement by person of the art. 
         [0044]    With reference to  FIG. 2 , when there are two rails  14 , they may construct a pair of rails of the same shape. The pair of rails  14  are placed on respective inner walls of the enclosing walls  110 , located at two lateral sides of the element  13 , of the cavity  11 . Furthermore, the pair of rails  14  are at the substantially same height on the two enclosing walls  110 . The two rails  14  may not have strictly same height at the enclosing walls  110  of the cavity  11 , due to not strictly rectangular shape of the cavity  11  or manufacture tolerance. However, it should be noted that function of the rails  14  of the present invention may still be achieved through they are not at the same height in a strict manner. Further, it should also be noted that the enclosing walls  110  at two lateral sides of the dielectric element  13  mean that they are substantially parallel with the thickness direction of the element  13 . These enclosing walls are different from those opposite to the element  13  as mentioned above. 
         [0045]    For the receiving space to be filled with the dielectric element  13  as much as possible, the phase shifting circuit  12  is preferably mounted between the pair of rails  14 . As such, the dielectric elements  13  (such as an upper dielectric element  130  and a lower dielectric element  131 ) maybe disposed over and below the dielectric circuit  12  respectively to obtain the equivalent dielectric constant as great as possible for the phase shifter  1  of the present invention. 
         [0046]    To adapt installation of the phase shifting circuit  12 , the thickness of each rail  14  should be larger than that of the phase shifting circuit  12  to avoid contact between the dielectric elements  13  supported on the same rail  14  and phase shifting circuit  12 . 
         [0047]    The two rails  14  may also be disposed on inner walls of the enclosing walls  110  respectively located just over and below the phase shifting circuit  12 . In this situation, the rails  14  may be arranged according to arranging manner of one rail  14  as described above. That is, the dielectric element  13  and rail  14  are assembled together by inserting the rail  14  into the sliding groove  139  of the element  13 . 
         [0048]    When there are two rails  14  inside the cavity  11 , and they locate over and below the phase shifting circuit  12  respectively, the two rails  14  may be different from each other. Arrangement of the rails  14  inside the cavity  11  and shape of the rails  14  may be determined according to those of a single rail  14  as discussed above. Description of the same will be omitted herefrom. 
         [0049]    Referring to  FIG. 3 , more rails  14  may be disposed in the cavity  11 . For example, two pairs of rails  14  may be presented in the cavity  11 . The two pairs of rails  14  are disposed on a pair of lateral enclosing walls  110  at two sides of the element  13  in a substantially parallel manner. Moreover, a pair of holding grooves  111  is defined between the two pairs of rails  14  and extends along the longitudinal direction of the cavity  11  for holding the phase shifting circuit  12  therein. The phase shifting circuit  12  is carried on a base plate such as a PCB. The holding groove  111  is intended for holding the base plate of the circuit  12  (the dielectric supporting member  120 ). As a result, two pairs of rails are provided over and below the phase shifting circuit  12  respectively, (for example the upper rails  141  and lower rails  142 ). 
         [0050]    Correspondingly, the dielectric element  13  includes an upper dielectric element  130  disposed on the upper rails  141  and a lower dielectric element  131  disposed on the lower rails  142 . Owing to arrangement of the two pairs of rails  14 , movement of the dielectric element  13  is restricted, thus avoiding contacting between the dielectric element  13  and phase shifting circuit  12  during movement of the dielectric element  13 , and improving inter-modulation and reliability. 
         [0051]    Please also refer to  FIG. 1 . To maintain synchronous movement of the upper dielectric element  130  and lower dielectric element  131 , the dielectric element  13  further includes a dielectric element connection member  132 . Furthermore, to drive the dielectric element  13  by an external device such as a motor (not shown), the phase shifter  1  of the invention may further include an external force actuation element  15  connected to the dielectric element  13  and disposed at an opened end of the cavity  11 . 
         [0052]    Person of the art should understand that the construction of the phase shifting circuit, dielectric element, and rails in this embodiment may be applied to other embodiments. Accordingly, in following embodiments, a certain structure perhaps will not be described and it should not be understood that the phase shifter of the present invention lacks of this certain structure. This can be configured upon requirement by person of the art for realizing objects of the invention. 
       Second Embodiment 
       [0053]    Refer to  FIGS. 5-7 . The dielectric phase shifter of the present invention is a combinative phase shifter  2  made by several such as two sub-phase shifters  201  and  202 , which share a cavity  21 . 
         [0054]    Two vertically juxtaposed receiving spaces are defined in the cavity  21 . Said receiving spaces are for mounting a phase shifting circuit  22 , a dielectric element  23 , and other components therein. These spaces also allow straight movement of the dielectric element  23  along a longitudinal direction of the cavity  21 . When the same phase shifting circuits  22  are installed into the two receiving spaces respectively, the combined phase shifter  2  works at a same frequency, and it is suitable for a single frequency dual-polarized antenna. When different phase shifting circuits  22  are installed into the two receiving spaces respectively, the combined phase shifter  2  may work at different frequency, and it is suitable for a multiple-frequency antenna. 
         [0055]    Similar to the first embodiment, in the second embodiment, each of the sub-phase shifters  201  and  202  is constructed of multiple enclosing walls  210  and a receiving space defined by said multiple enclosing walls  210 . Inside the receiving space, the phase shifting circuit  22  is disposed. The dielectric element  23  is disposed between the phase shifting circuit  22  and enclosing walls  210 . 
         [0056]    The phase shifting circuit  22  includes a phase shifting conductor  220  made of a metal conductor  220  according to principle of phase shifting circuit, and a dielectric supporting member  221  for securing the metal conductor  220  into the cavity  21 . The metal conductor  220  is bent to define a substantially U-shaped configuration, and includes two straight arms  2201  and a base portion  2202  by which the two arms  2201  are joined together. An end portion of each straight arm  2201  far away from the base portion  2202  is for connecting a transmission cable (not labeled) as shown in  FIG. 5 . 
         [0057]    Please see  FIG. 6 . To avoid direct contact between the phase shifting circuit  22  and dielectric element  23 , a rail  24  is disposed between the phase shifting circuit  22  and dielectric element  23 , thereby preventing direct contact between the element  23  and circuit  22 . 
         [0058]    A pair of rails  24  is contained in the receiving space of each of the sub sub-phase shifters  201  and  202 . The pairs of rails  24  are at the substantially same height on corresponding inner walls of the enclosing walls  210 . The height of the rails  24  is larger than the thickness of the phase shifting circuit  22 . The phase shifting circuit  22  is disposed between the pair of rails. In addition, the dielectric elements  23  for example an upper dielectric element  230  and a lower dielectric element  231  are located just over and below the circuit  22 . 
         [0059]    To facilitate straight movement of the dielectric element  23  along the longitudinal direction of the cavity, the phase shifter  2  may further include an external force actuation element  25 . Moreover, to maintain synchronous movement of the upper dielectric element  230  and lower dielectric element  231 , the dielectric element  23  further includes a dielectric element connection member  232 . 
         [0060]    Please refer to  FIG. 7  showing a cross section of another phase shifter of the second embodiment. This phase shifter  2  is constructed of four sub-phase shifters  201 ,  202 ,  203 , and  204 , which are juxtaposed vertically and laterally. 
         [0061]    Each sub-phase shifter (for example  204 ) has a pair of rails  24  contained therein, and the pair of rails  24  is at the substantially same height on the corresponding inner walls of two opposed enclosing walls  210 . 
         [0062]    In addition, regarding arrangement manner of the dielectric element  23  and rails  24  inside each sub-phase shifter, including number, shape, structure, and location of the dielectric element and rails, reference may be made to the first embodiment and accordingly, here they will not be repeated again. 
         [0063]    In a summary, by providing a number of rails inside the cavity of the phase shifter, and causing movement of the dielectric element along the rails relative to the cavity and phase shifting circuit, phase shifting is achieved for signal inside the phase shifter. The electrical and physical characteristics of the phase shifter are significantly enhanced due to prevention of direct contact between the dielectric element and phase shifting circuit. 
         [0064]    Though various embodiments of the present invention have been illustrated above, a person of the art will understand that, variations and improvements made upon the illustrative embodiments fall within the scope of the present invention, and the scope of the present invention is only limited by the accompanying claims and their equivalents.