Patent Publication Number: US-10784552-B2

Title: High-frequency power combiner

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2017-180274 filed on Sep. 20, 2017 and Japanese Patent Application No. 2018-172719 filed on Sep. 14, 2018, the contents of which are incorporated herein by reference in their entirety. 
     FIELD 
     Embodiments described herein relate generally to a high-frequency power combiner. 
     BACKGROUND 
     A high-frequency power combiner for combining high-frequency outputs is used, for example, in a television broadcasting transmitter or the like to output high power. The high-frequency power combiner is difficult to miniaturize because an internal conductor (a high-frequency line) easily generates heat. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view schematically showing a constitution of a high-frequency power combiner of an embodiment. 
         FIG. 2  is a cross-sectional side view schematically showing the constitution of the high-frequency power combiner of the embodiment. 
         FIG. 3  is a cross-sectional view showing an output-side terminal of the high-frequency power combiner of the embodiment. 
         FIG. 4  is a cross-sectional view showing an input-side terminal of the high-frequency power combiner of the embodiment. 
         FIG. 5  is a plan view schematically showing a modified example of the high-frequency power combiner of the embodiment. 
         FIG. 6  is a cross-sectional view showing a modified example of the output-side terminal. 
         FIG. 7  is a cross-sectional view showing a modified example of the input-side terminal. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a high-frequency power combiner has an external conductor and an internal conductor. The external conductor defines an internal space. The internal conductor has an output-side line and a plurality of input-side lines that branch off from the output-side line. The internal conductor is provided in the internal space of the external conductor. The high-frequency power combiner of the embodiment has a structure that can store a liquid in contact with the internal conductor in the internal space. 
     Hereinafter, the high-frequency power combiner of the embodiment will be described with reference to the drawings. 
       FIG. 1  is a plan view schematically showing a constitution of a high-frequency power combiner  10  of an embodiment.  FIG. 2  is a cross-sectional view schematically showing the constitution of the high-frequency power combiner  10  of the embodiment.  FIG. 2  shows a cross section taken along the line I-I of  FIG. 1 . In  FIGS. 1 and 2 , an X direction is a length direction of a bottom plate  11  of the external conductor  1 . A Y direction is a direction orthogonal to the X direction in a plane along the bottom plate  11 , and a width direction of the bottom plate  11 . A Z direction is a direction orthogonal to the X and Y directions, and a thickness direction of the bottom plate  11 . In the following description, the Z direction is also referred to as a vertical direction or a height direction. A plan view refers to a view in the Z direction. In  FIG. 1 , a top plate  14  is not shown. 
     In the following explanation, it is assumed that the high-frequency power combiner  10  has a posture in which a top plate  14  is located at an upper side with respect to a bottom plate  11 , and a positional relationship between various members of the high-frequency power combiner  10  will be described. Note that, the posture of the high-frequency power combiner  10  is only provisionally set for convenience of explanation. Therefore, the posture of the high-frequency power combiner  10  in this embodiment is not limited to a posture of the high-frequency power combiner during use. 
     One side in the X direction is referred to as an A direction, and a direction of the other side in the X direction is referred to as a B direction. One side in the Y direction is referred to as a C direction, and a direction of the other side in the Y direction is referred to as a D direction. One side in the Z direction is referred to as an E direction, and a direction of the other side in the Z direction is referred to as an F direction. The E direction is an upper side. A plane defined by the X and Y directions is referred to as an XY plane. A plane defined by the X and Z directions is referred to as an XZ plane. A plane defined by the Y and Z directions is referred to as a YZ plane. 
     As shown in  FIGS. 1 and 2 , the high-frequency power combiner  10  includes an external conductor  1 , an internal conductor  2 , an output-side terminal  3 , and input-side terminals  4  and  4 . 
     The external conductor  1  includes a bottom plate  11 , lateral plates  12  and  12 , end plates  13  and  13 , and a top plate  14  (see  FIG. 2 ), and is formed in a container shape. 
     As shown in  FIG. 1 , the bottom plate  11  has a rectangular shape, for example an oblong shape, in a plan view. The lateral plates  12  and  12  are vertically arranged on lateral edges  11   a  and  11   a  of the bottom plate  11 . The lateral plates  12  and  12  are formed along the XZ plane. The end plates  13  and  13  are vertically arranged on end edges  11   b  and  11   b  of the bottom plate  11 . The end plates  13  and  13  are formed along the YZ plane. 
     As shown in  FIG. 2 , the top plate  14  is provided on upper ends of the lateral plates  12  and the end plates  13 . The top plate  14  is formed along the XY plane. A space surrounded by the bottom plate  11 , the lateral plates  12  and  12 , the end plates  13  and  13 , and the top plate  14  is referred to as an internal space  15 . The external conductor  1  defines the internal space  15 . 
     Lower ends of the lateral plates  12  and lower ends of the end plates  13  are liquid-tightly connected to a periphery of the bottom plate  11 . 
     Upper ends of the lateral plates  12  and upper ends of the end plates  13  are liquid-tightly connected to a periphery of the top plate  14 . Ends of the lateral plates  12  and lateral edges of the end plates  13  are joined liquid-tightly. For this reason, the external conductor  1  can store a liquid (a heat carrier)  5  in the internal space  15 . 
     Among the bottom plate  11 , the lateral plates  12  and  12 , the end plates  13  and  13 , and the top plate  14 , the two or more neighboring plates may be integrally formed. For example, the bottom plate  11 , the lateral plates  12  and  12 , and the end plates  13  and  13  may be integrally formed. As will be described below, the external conductor  1  can store the liquid  5  in contact with the internal conductor  2 . 
     The external conductor  1  may have a sealed structure. When the external conductor  1  has sealed structure, leakage and evaporation of the liquid  5  can be prevented. In addition, a pressure in the external conductor  1  can be constantly maintained. 
     The bottom plate  11  and the top plate  14  are formed of a conductive material in part or in whole. Examples of the conductive material are preferably metals such as aluminum (or an aluminum alloy), copper (or a copper alloy), and so on. The bottom plate  11  and the top plate  14  are grounded via a connecting line (not shown in the figure), and thus the external conductor  1  is a ground conductor. 
     An insertion hole  13   a  through which an end conductor  25  is inserted is formed in one end plate  13  ( 13 A) of the pair of end plates  13  and  13 . An inner diameter of the insertion hole  13   a  is larger than an external size of the end conductor  25 . A pair of insertion holes  13   b  and  13   b  through which end conductors  28  and  28  are inserted are formed in the other end plate  13  ( 13 B). Inner diameters of the insertion holes  13   b  are larger than external sizes of the end conductors  28 . 
       FIG. 3  is a cross-sectional view showing the output-side terminal  3 . As shown in  FIG. 3 , the output-side terminal  3  is formed in a substantially tubular shape (e.g., a cylindrical shape), and is provided on an outer surface of the end plate  13  ( 13 A). The output-side terminal  3  is provided at a position matched with the insertion hole  13   a . The end conductor  25  is inserted through the output-side terminal  3 . An annular interposing member  17  ( 17 A) is provided inside the output-side terminal  3  and the insertion hole  13   a . The output-side terminal  3  is in contact with the outer surface of the end plate  13  ( 13 A) and is thereby electrically connected to the end plate  13  ( 13 A). 
     An annular packing  18  ( 18 A 1 ) (closing member) is provided between the inner peripheral face of the insertion hole  13   a  and the outer peripheral face of the interposing member  17  ( 17 A). An annular packing  18  ( 18 A 2 ) (closing member) is provided between the inner peripheral face of the interposing member  17  ( 17 A) and the outer peripheral face of the end conductor  25 . The interposing member  17  ( 17 A) and the packings  18  ( 18 A 1 ,  18 A 2 ) liquid-tightly close the insertion hole  13   a . Accordingly, it is possible to prevent the liquid  5  in the external conductor  1  from leaking out of the insertion hole  13   a.    
       FIG. 4  is a cross-sectional view showing the input-side terminal  4 . As shown in  FIG. 4 , the input-side terminal  4  is formed in a substantially tubular shape (e.g., a cylindrical shape), and are provided on an outer surface of the end plate  13  ( 13 B). The input-side terminals  4  are provided at positions matched with the insertion holes  13   b . The end conductors  28  are inserted through the input-side terminals  4 . An annular interposing member  17  ( 17 B) is provided inside the insertion hole  13   b . The input-side terminals  4  in contact with the outer surface of the end plate  13  ( 13 B) and is thereby electrically connected to the end plate  13  ( 13 B). 
     The interposing member  17  ( 17 A and  17 B) is an insulator formed of a resin (e.g., Teflon (registered trademark), a polyolefin resin, or the like), a rubber, or the like. The packing  18  is formed of a soft resin (a polyolefin resin or the like), a rubber, or the like, and can be elastically deformed. 
     An annular packing  18  ( 18 B 1 ) (closing member) is provided between the inner peripheral face of the insertion hole  13   b  and the outer peripheral face of the interposing member  17  ( 17 B). An annular packing  18  ( 18 B 2 ) (closing member) is provided between the inner peripheral face of the interposing member  17  ( 17 B) and the outer peripheral face of the end conductor  28 . The interposing member  17  ( 17 B) and the packings  18  ( 18 B 1 ,  18 B 2 ) liquid-tightly close the insertion hole  13   b . Accordingly, it is possible to prevent the liquid  5  in the external conductor  1  from leaking out of the insertion hole  13   b.    
     The end plates  13  are formed of a metal such as aluminum (or an aluminum alloy), copper (or a copper alloy), or the like. 
     As shown in  FIGS. 1 and 2 , the internal conductor  2  includes an output-side line  21  and a pair of input-side lines  22  and  22 . 
     The output-side line  21  includes a first line  23  and a second line  24 . The first line  23  extends in the X direction. The first line  23  has an electric length that corresponds to, for example, a quarter of an operating wavelength. The second line  24  extends in the B direction from an end of the first line  23  which is directed in the B direction. A width (a size in the Y direction) of the second line  24  is smaller than that of the first line  23 . The first line  23  and the second line  24  are formed in a plate shape following the XY plane. 
     The end conductor  25  is connected to an end of the second line  24  which is directed in the B direction. The end conductor  25  extends in the B direction from the end of the second line  24  which is directed in the B direction, and is inserted through the insertion hole  13   a  of the end plate  13  ( 13 A). 
     As shown in  FIG. 1 , input-side lines  22  and  22  are branch lines that are formed by branching off from an end  21   a  of the output-side line  21  which is directed in the A direction as a branching point into two pieces. 
     One input-side line  22  ( 22 A) of the input-side lines  22  and  22  includes a first line  26  ( 26 A) and a second line  27  ( 27 A). The first line  26  ( 26 A) extends in the C direction starting from the end  21   a  of the output-side line  21 . The second line  27  ( 27 A) extends in the A direction from an end of the first line  26  ( 26 A) which is directed in the C direction. The first line  26  ( 26 A) and the second line  27  ( 27 A) are formed in a plate shape following the XY plane. 
     The end conductor  28  ( 28 A) is connected to an end of the second line  27  ( 27 A) which is directed in the A direction. The end conductor  28  ( 28 A) extends in the A direction from the end of the second line  27  ( 27 A) which is directed in the A direction, and is inserted through the insertion hole  13   b  of the end plate  13  ( 13 B). 
     The other input-side line  22  ( 22 B) of the input-side lines  22  and  22  includes a first line  26  ( 26 B) and a second line  27  ( 27 B). The first line  26  ( 26 B) extends in the D direction starting from the end  21   a  of the output-side line  21 . The second line  27  ( 27 B) extends in the A direction from an end of the first line  26  ( 26 B) which is directed in the D direction. The first line  26  ( 26 B) and the second line  27  ( 27 B) are formed in a plate shape following the XY plane. 
     The end conductor  28  ( 28 B) is connected to an end of the second line  27  ( 27 B) which is directed in the A direction. The end conductor  28  ( 28 B) extends in the A direction from the end of the second line  27  ( 27 B) which is directed in the A direction, and is inserted through the insertion hole  13   b  of the end plate  13  ( 13 B). 
     The internal conductor  2  is formed of a conductive material. Examples of the conductive material are preferably metals such as copper (or a copper alloy), aluminum (or an aluminum alloy), and so on. The output-side line  21  and the input-side lines  22  and  22  are integrally formed. 
     The high-frequency power combiner  10  is a combiner in which the transmission lines (the output-side line  21 , the input-side lines  22  and  22 , and so on) are formed of a stripline. 
     The high-frequency power combiner  10  may be, for example, an impedance conversion type combiner in which output impedance and input impedance are matched (subjected to impedance matching) by the internal conductor  2 . 
     As shown in  FIG. 2 , the internal conductor  2  is disposed in the internal space  15 . The internal conductor  2  is located at a height position at which it is separated from the bottom plate  11  and the top plate  14 . That is, the internal conductor  2  is located at a position at which it is higher than the bottom plate  11  and is lower than the top plate  14 . 
     The liquid  5  is stored in the internal space  15  of the external conductor  1 . 
     As the liquid  5 , a heat carrier having an insulation property at an operating temperature (e.g., 25° C.) is preferred. For example, a fluorine inactive liquid, a hydrocarbon insulating oil, a silicone oil, or the like is used as the liquid  5 . Fluorinert FC-770 (registered trademark) or the like available from 3M can be used as the fluorine inactive liquid. Main components of the hydrocarbon insulating oil are, for example alkylbenzene, polybutene, alkylnaphthalene, and so on. 
     Dielectric strength (2.54 mm gap) of the liquid  5  is, for example, 38 kV to 46 kV at 25° C. A boiling point of the liquid  5  is, for example, 50° C. or higher and 180° C. or lower. Permittivity at a frequency of 1 kHz is 1.76 to 1.90 at 25° C. 
     The liquid  5  is stored in the internal space  15  to be able to be in contact with the internal conductor  2 . In  FIG. 1  or the like, the entire internal space  15  is filled with the liquid  5 . However, when the liquid  5  has an amount smaller than a volume of the internal space  15 , a surface of the liquid  5  is located lower than an uppermost portion of the internal space  15 . 
     The liquid  5  may be in contact with only a part of the internal conductor  2 , but the entire internal conductor  2  is preferably immersed in the liquid  5 . When the entire internal conductor  2  is immersed in the liquid  5 , cooling efficiency of the internal conductor  2  can be improved. 
     When the internal conductor  2  generates heat due to energization, the liquid  5  is reduced in specific gravity due to a rise in temperature, and thus the liquid  5  is subjected to natural convection (thermal convection) in the internal space  15 . Due to the convection of the liquid  5 , the internal conductor  2  is efficiently cooled. 
     When the liquid  5  has an amount smaller than a maximum volume formed by the internal space  15 , a space is secured between the surface of the liquid  5  and a part (e.g., the lateral plates  12 ) of the external conductor  1 . For this reason, so-called ebullient cooling that boils the liquid  5  to increase a cooling effect based on latent heat becomes possible. 
     In the high-frequency power combiner  10 , the internal conductor  2  can be efficiently cooled by the liquid  5  stored in the internal space  15 . For this reason, the internal conductor  2  can be made smaller (e.g., thinner or narrower) without causing an excessive rise in temperature. Accordingly, the high-frequency power combiner  10  can be miniaturized. For example, a thickness (a size in the Z direction) of the high-frequency power combiner  10  can be reduced. 
     A dielectric is used as the insulating liquid  5 , and thereby electric lengths of the output-side line  21  and the input-side lines  22  and  22  become short compared to a case in which the liquid  5  is not used. For this reason, a size of the internal conductor  2  in the X direction can be reduced. Therefore, a length (a size in the X direction) of the high-frequency power combiner  10  can be reduced. Thus, the high-frequency power combiner  10  can be further miniaturized. 
     Because an external conductor in a general-purpose high-frequency power combiner can be used as the external conductor  1  in the high-frequency power combiner  10 , a manufacturing cost can be reduced. 
     The high-frequency power combiner  10  in which the internal space  15  of the external conductor  1  is filled with the heat carrier  5  is configured to include the external conductor  1 , the internal conductor  2 , the output-side terminal  3 , the input-side terminals  4  and  4 , and the heat carrier  5 . 
       FIG. 5  is a plan view schematically showing a constitution of a high-frequency power combiner  10 A of another embodiment. In  FIG. 5 , the top plate  14  is not shown. 
     As shown in  FIG. 5 , in the high-frequency power combiner  10 A, one lateral plate  12 A of a pair of lateral plates  12  and  12  is provided with an inflow passage  31  of a liquid  5 . The inflow passage  31  is formed, for example, in a tubular shape. The inflow passage  31  can introduce the liquid  5  from a supply source (not shown in the figure) into an internal space  15  of an external conductor  1  through an inflow hole  12   a  of the lateral plate  12 A. 
     The other lateral plate  12 B of the lateral plates  12  and  12  is provided with an outflow passage  32  of the liquid  5 . 
     The outflow passage  32  is formed, for example, in a tubular shape. The outflow passage  32  can lead the liquid  5  of the internal space  15  of the external conductor  1  to the outside of the external conductor  1  through an outflow hole  12   b  of the lateral plate  12 B. 
     In the high-frequency power combiner  10 A, efficiency of the liquid  5  cooling the internal conductor  2  can be increased by causing the liquid  5  supplied from the outside to circulate in the internal space  15  of the external conductor  1 . 
     The heat carrier  5  led out by the outflow passage  32  may be cooled by a heat exchanger (not shown in the figure), and be reused through the inflow passage  31 . 
     The high-frequency power combiners of the embodiments may adopt a structure of a 3 dB coupler type, a Wilkinson type, a rat race type, or the like. 
     The number of input-side lines that branch off from one output-side line in an internal conductor is not limited to two, and may be an arbitrary number of three or more. 
     Each of the high-frequency power combiners  10  and  10 A of the embodiments is configured such that the external conductor  1  can store the liquid  5 , but the configuration of the high-frequency power combiner is not limited thereto. For example, each of the high-frequency power combiners of the embodiments need not have a structure in which the external conductor can store the liquid as long as it includes a component in which the liquid in contact with the internal conductor can be stored in the internal space (e.g., a container-shaped intermediate structure provided in the external conductor), in addition to the external conductor. 
       FIG. 6  is a cross-sectional view showing an output-side terminal  103  serving as a modified example of the output-side terminal  3 . As shown in  FIG. 6 , the output-side terminal  103  is formed in a substantially tubular shape (e.g., a cylindrical shape), and is provided on an outer surface of the end plate  13  ( 13 A). The output-side terminal  103  is provided at a position matched with the insertion hole  13   a . The end conductor  25  is inserted through the output-side terminal  103 . The output-side terminal  103  is mounted on the outer surface of the end plate  13  ( 13 A) via an annular interposing member  117 . The output-side terminal  103  is electrically connected to the end plate  13  ( 13 A) at a connection point which is not shown in the figure. 
     An annular packing  118  ( 118 A) (closing member) is provided inside the output-side terminal  103 . The packing  118  is formed of a soft resin (a polyolefin resin or the like), a rubber, or the like, and can be elastically deformed. The packing  118  has an insertion hole  118   a  through which an end conductor  25  is inserted. An outer peripheral face of the packing  118  is in contact with an inner peripheral face of the output-side terminal  103  without a gap. An inner peripheral face of the packing  118  is in contact with an outer peripheral face of the end conductor  25  without a gap. The insertion hole  13   a  is liquid-tightly closed by the packing  118 , the output-side terminal  103 , and the interposing member  117 , and thus the liquid  5  in the external conductor  1  can be prevented from leaking out of the insertion hole  13   a.    
       FIG. 7  is a cross-sectional view showing an input-side terminal  104  serving as a modified example of the input-side terminal  4 . As shown in  FIG. 7 , the input-side terminal  104  is formed in a substantially tubular shape (e.g., a cylindrical shape), and is provided on an outer surface of the end plate  13  ( 13 B). The input-side terminal  104  is provided at a position matched with the insertion hole  13   b . The end conductor  28  is inserted through the input-side terminal  104 . The input-side terminal  104  is mounted on the outer surface of the end plate  13  ( 13 B) via an annular interposing member  117 . The input-side terminal  104  is electrically connected to the end plate  13  ( 13 B) at a connection point which is not shown in the figure. 
     An annular packing  118  ( 118 B) (closing member) is provided inside the input-side terminal  104 . The packing  118  has an insertion hole  118   b  through which an end conductor  28  is inserted. An outer peripheral face of the packing  118  is in contact with an inner peripheral face of the input-side terminal  104  without a gap. An inner peripheral face of the packing  118  is in contact with an outer peripheral face of the end conductor  28  without a gap. The insertion hole  13   b  is liquid-tightly closed by the packing  118 , the input-side terminal  104 , and the interposing member  117 , and thus the liquid  5  in the external conductor  1  can be prevented from leaking out of the insertion hole  13   b.    
     The interposing member  117  is formed of a resin (e.g., Teflon (registered trademark), a polyolefin resin, or the like), a rubber, or the like. The output-side terminal  103  and the input-side terminals  104  come into contact with the outer surfaces of the end plates  13  via the interposing members  117  without a gap, and thus the leakage of the liquid  5  can be prevented. 
     The packings  118  may be provided in the insertion holes  13   a  and  13   b  of the end plates  13  while in contact with the inner circumferential surfaces of the insertion holes  13   a  and  13   b . In this case, the insertion holes  13   a  and  13   b  are also closed, and the liquid  5  in the external conductor  1  can be prevented from leaking outside. 
     In the above explanation of the embodiment, although it is assumed that the high-frequency power combiner  10  has a posture in which a top plate  14  is located at an upper side with respect to a bottom plate  11 , the posture of the high-frequency power combiner  10  is not particularly limited. For example, the high-frequency power combiner  10  may be used in a posture in which one of the lateral plates  12  is located at an upper side with respect to the other of the lateral plates  12 . 
     According to the embodiments described above, since the liquid  5  coming into contact with the internal conductor  2  can be stored, the internal conductor  2  can be efficiently cooled by the liquid  5  filling the internal space  15 . For this reason, the internal conductor  2  can be made smaller (e.g., thinner or narrower) without causing an excessive rise in temperature. Accordingly, the high-frequency power combiner  10  can be miniaturized. For example, the thickness (the size in the Z direction) of the high-frequency power combiner  10  can be reduced. 
     The insulating liquid  5  is used as the dielectric, and thereby the electric lengths of the output-side line  21  and the input-side lines  22  and  22  become short, compared to the case in which the liquid  5  is not used. For this reason, the size of the internal conductor  2  in the X direction can be reduced. Therefore, the length (the size in the X direction) of the high-frequency power combiner  10  can be reduced. Thus, the high-frequency power combiner  10  can be further miniaturized. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.