Patent Publication Number: US-2023140741-A1

Title: Non-reciprocal circuit element and communication apparatus having the same

Description:
BACKGROUND OF THE ART 
     Field of the Art 
     The present disclosure relates to a non-reciprocal circuit element and a communication apparatus having the same and, more particularly, to a non-reciprocal circuit element having a structure in which a magnetic rotator is accommodated in a through hole formed in a dielectric substrate and a communication apparatus having such a non-reciprocal circuit element. 
     Description of Related Art 
     A non-reciprocal circuit element such as an isolator or a circulator, which is a kind of a magnetic device, has a configuration in which a magnetic rotator and a permanent magnet are sandwiched between upper and lower yokes. Non-reciprocal circuit elements described in JP 2002-043808A, JP 09-321504A, and JP 11-234003A have a structure in which a magnetic rotator is accommodated inside a through hole formed in a dielectric substrate. 
     However, the present inventor&#39;s studies have revealed that contact of the magnetic rotator with the inner wall of the through hole increases an insertion loss. 
     SUMMARY 
     One of the objectives of the present disclosure is to reduce insertion loss in a non-reciprocal circuit element having a structure in which a magnetic rotator is accommodated in a through hole formed in a dielectric substrate. Another object of the present disclosure is to provide a communication apparatus having such a non-reciprocal circuit element. 
     A non-reciprocal circuit element according to the present disclosure includes a dielectric substrate having a through hole, a magnetic rotator accommodated in the through hole, and a permanent magnet that applies a magnetic field to the magnetic rotator. The magnetic rotator is supported by the dielectric substrate without contacting the inner wall of the through hole. 
     A communication apparatus according to the present disclosure includes the above-described non-reciprocal circuit element. 
     As described above, according to the present disclosure, it is possible to reduce insertion loss in a non-reciprocal circuit element having a structure in which a magnetic rotator is accommodated in a through hole formed in a dielectric substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above features and advantages of the present disclosure will be more apparent from the following description of certain embodiments taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a schematic perspective view from the upper side illustrating the outer appearance of a non-reciprocal circuit element  1  according to an embodiment of the present disclosure; 
         FIG.  2    is a schematic perspective view from the lower side illustrating the outer appearance of the non-reciprocal circuit element  1 ; 
         FIG.  3    is a schematic perspective view illustrating a state where the lower yoke  40  is removed from the non-reciprocal circuit element  1 ; 
         FIG.  4    is a schematic perspective view illustrating a state where the permanent magnet  20  and upper yoke  30  are removed from the non-reciprocal circuit element  1 ; 
         FIG.  5    is a schematic perspective view of the dielectric substrate  10 ; 
         FIG.  6    is a schematic plan view for explaining the structure of the magnetic rotator M; 
         FIG.  7    is a schematic perspective view illustrating a state where the center conductor  81  is removed from the magnetic rotator M; 
         FIG.  8    is a schematic plan view for explaining the positional relation between the through hole  11   a  and magnetic rotator M; and 
         FIG.  9    is a graph for explaining the relation between a distance L between the magnetic rotator M and the inner wall of the through hole  11   a  and insertion loss; and 
         FIG.  10    is a block diagram illustrating the configuration of a communication apparatus  200  using the non-reciprocal circuit element according to the above embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Some embodiments of the present disclosure will be explained below in detail with reference to the accompanying drawings. 
       FIGS.  1  and  2    are schematic perspective views illustrating the outer appearance of a non-reciprocal circuit element  1  according to an embodiment of the present disclosure.  FIG.  1    is a view from the upper side, and  FIG.  2    is a view from the lower side. 
     The non-reciprocal circuit element  1  according to the present embodiment is a non-reciprocal circuit element of a surface mount type and includes, as illustrated in  FIGS.  1  and  2   , a dielectric substrate  10 , a permanent magnet  20 , an upper yoke  30 , and a lower yoke  40 . The dielectric substrate  10  and permanent magnet  20  are sandwiched between the upper and lower yokes  30  and  40 . The dielectric substrate  10  has, on its lower surface  12 , terminal electrodes  51  to  56  and a ground pattern  50 . The upper yoke  30  has a top plate part  31  constituting the xy plane and folding parts  32  and  33  constituting the yz plane. The lower yoke  40  has a bottom plate part  41  constituting the xy plane and folding parts  42  and  43  constituting the xz plane. The folding parts  42  and  43  of the lower yoke  40  are fitted to the top plate part  31  of the upper yoke  30  to constitute a closed magnetic path. 
       FIG.  3    is a schematic perspective view illustrating a state where the lower yoke  40  is removed from the non-reciprocal circuit element  1 .  FIG.  4    is a schematic perspective view illustrating a state where the permanent magnet  20  and upper yoke  30  are removed from the non-reciprocal circuit element  1 .  FIG.  5    is a schematic perspective view of the dielectric substrate  10 . 
     As illustrated in  FIGS.  3  to  5   , the dielectric substrate  10  has upper and lower surfaces  11  and  12  constituting the xy plane, and a through hole  11   a  penetrates substantially the center portion of the dielectric substrate  10  in the z-direction. A magnetic rotator M is accommodated in the through hole  11   a  . An upper surface  11  of the dielectric substrate  10  is flat, while a lower surface  12  of the dielectric substrate  10  has a recessed part  12   a  extending in the y-direction, where the thickness of the dielectric substrate  10  is reduced. The bottom plate part  41  of the lower yoke  40  is accommodated in the recessed part  12   a  . This prevents the bottom plate part  41  of the lower yoke  40  from protruding from the lower surface  12  of the dielectric substrate  10 . 
     Connection patterns  61  to  63  are provided on the upper surface  11  of the dielectric substrate  10 . The connection patterns  61  to  63  are connected respectively to ports P 1  to P 3  of the magnetic rotator M. A part of each of the connection patterns  61  to  63  that overlaps the ground pattern  50  provided on the lower surface  12  serves also as a capacitance electrode of a capacitor. That is, the connection patterns  61  to  63  formed on the upper surface  11  of the dielectric substrate  10  and ground pattern  50  formed on the lower surface  12  of the dielectric substrate  10  constitute a capacitor pattern. The connection pattern  61  is connected to the terminal electrode  51  provided on the lower surface  12  of the dielectric substrate  10  through a connection pattern  71  provided on a side surface  13  of the dielectric substrate  10 . The connection pattern  62  is connected to the terminal electrode  52  provided on the lower surface  12  of the dielectric substrate  10  through a connection pattern  72  provided on a side surface  14  of the dielectric substrate  10 . The connection pattern  63  is connected to the terminal electrode  53  provided on the lower surface  12  of the dielectric substrate  10  through a connection pattern  73  provided on the side surface  13  of the dielectric substrate  10 . The side surfaces  13  and  14  constitute the yz plane. The terminal electrodes  54  to  56  are connected to a ground conductor  80  included in the magnetic rotator M through the ground pattern  50  and the bottom plate part  41  of the lower yoke  40 . 
       FIG.  6    is a schematic plan view for explaining the structure of the magnetic rotator M. 
     As illustrated in  FIG.  6   , the magnetic rotator M has center conductors  81  to  83  and a ferrite core  90 . The center conductors  81  to  83  are each covered with an insulating film (which is omitted for easy understanding of the structure).  FIG.  7    illustrates a state where the center conductor  81  is removed from the magnetic rotator M. The center conductors  81  to  83  are constituted by a plurality of metal conductors crossing one another at an angle of substantially 120°. In the example illustrated in  FIGS.  6  and  7   , the center conductor  81  is constituted by four metal conductors, and the center conductors  82  and  83  are each constituted by two metal conductors. The width of the center conductor  83  is enlarged at its center portion for characteristic adjustment, while the width of each of the center conductors  81  and  82  is constant. One ends of the center conductors  81  to  83  are connected respectively to the ports P 1  to P 3 , and the other ends thereof are connected in common to the ground conductor  80  positioned on the back surface side of the ferrite core  90 . As a result, the ferrite core  90  is sandwiched between the center conductors  81  to  83  and the ground conductor  80 . 
     With the above configuration, the center conductor  81  is connected to the terminal electrode  51  through the connection patterns  61  and  71 , the center conductor  82  is connected to the terminal electrode  52  through the connection patterns  62  and  72 , and the center conductor  83  is connected to the terminal electrode  53  through the connection patterns  63  and  73 . Further, the ground conductor  80  is connected to the terminal electrodes  54  to  56  through the bottom plate part  41  of the lower yoke  40  and the ground pattern  50 . 
       FIG.  8    is a schematic plan view for explaining the positional relation between the through hole  11   a  and magnetic rotator M. 
     As illustrated in  FIG.  8   , the magnetic rotator M is supported by the dielectric substrate  10  without contacting the inner wall of the through hole  11   a  . That is, inside the through hole  11   a  , the magnetic rotator M is supported in a floating state. The reason why such a structure is adopted is that contact of the magnetic rotator M with the inner wall of the through hole  11   a  increases insertion loss. 
       FIG.  9    is a graph for explaining the relation between a distance L between the magnetic rotator M and the inner wall of the through hole  11   a  and insertion loss. 
     As illustrated in  FIG.  9   , insertion loss decreases as the distance L between the magnetic rotator M and the inner wall of the through hole  11   a  increases. In particular, in an area where the distance L is 50 μm or less, the reduction effect of insertion loss due to an increase in the distance L is conspicuous. Considering this, the distance L may be 50 μm or more. Further, when the distance L becomes about 100 μm, the reduction effect of insertion loss due to an increase in the distance L substantially saturates. Considering this, the distance L may be 100 μm or more. Furthermore, when the distance L becomes about 150 μm, the reduction effect of insertion loss due to an increase in the distance L completely saturates. The distance L may be designed to be more than 150 μm; however, in this case, the planar size of the dielectric substrate  10  increases, or the effective area of the dielectric substrate  10  decreases, so that the distance L may be 150 μm or less. 
     The distance L may be constant over the entire periphery of the magnetic rotator M or may vary depending on the position. The reduction effect of insertion loss depends on the minimum distance between the magnetic rotator M and the inner wall of the through hole  11   a  , so that when there is a variation in the distance L, the distance L may be defined by the minimum distance thereof. 
     As described above, a part of each of the connection patterns  61  to  63  provided on the upper surface  11  overlaps the ground pattern  50  provided on the lower surface  12  in the z-direction. A capacitance component obtained by the overlap between the connection patterns  61  to  63  and the ground pattern  50  is utilized as a matching capacitance. This eliminates the need to mount a chip type matching capacitor on the dielectric substrate  10 , thus making it possible to reduce the number of components. The matching capacitance can be adjusted by the shape or area of each of the connection patterns  61  to  63 . Further, the dielectric substrate  10  and lower yoke  40  are separated members, so that it is not necessary to use a composite part which is required to be produced by an insert molding method. 
     In addition, in the present embodiment, the through hole  11   a  is formed in the dielectric substrate  10 , and the magnetic rotator M is accommodated in the through hole  11   a  , thus making it possible to reduce the height of the non-reciprocal circuit element  1 . 
       FIG.  10    is a block diagram illustrating the configuration of a communication apparatus  200  using the non-reciprocal circuit element according to the above embodiment. 
     A communication apparatus  200  illustrated in  FIG.  10    is provided in, for example, a base station of a mobile communication system. The communication apparatus  200  includes a receiving circuit part  200 R and a transmitting circuit part  200 T which are connected to an antenna ANT adapted for data transmission and reception. The receiving circuit part  200 R includes a reception amplification circuit  201  and a receiving circuit  202  for processing a received signal. The transmitting circuit part  200 T includes a transmitting circuit  203  for generating an audio signal and a video signal and a power amplification circuit  204 . 
     In the thus configured communication apparatus  200 , non-reciprocal circuit elements  211  and  212  are inserted respectively into a path between the antenna ANT and the receiving circuit part  200 R and a path between the transmitting circuit part  200 T and the antenna ANT. The non-reciprocal circuit elements  211  and  212  may each be the non-reciprocal circuit element  1  according to the above embodiment. In the example illustrated in  FIG.  10   , the non-reciprocal circuit element  211  functions as a circulator, and the non-reciprocal circuit element  212  functions as an isolator having a terminal resistor R 0 . 
     While the one embodiment of the present disclosure has been described, the present disclosure is not limited to the above embodiment, and various modifications may be made within the scope of the present disclosure, and all such modifications are included in the present disclosure. 
     The technology according to the present disclosure includes the following configuration examples but not limited thereto. 
     A non-reciprocal circuit element according to the present disclosure includes a dielectric substrate having a through hole, a magnetic rotator accommodated in the through hole, and a permanent magnet that applies a magnetic field to the magnetic rotator. The magnetic rotator is supported by the dielectric substrate without contacting the inner wall of the through hole. 
     A communication apparatus according to the present disclosure includes the above-described non-reciprocal circuit element. 
     According to the present disclosure, the magnetic rotator does not contact the inner wall of the through hole, thus making it possible to reduce insertion loss. 
     In the present disclosure, the minimum distance between the magnetic rotator and the inner wall of the through hole may be 50 μm or more. This makes it possible to sufficiently reduce an insertion loss. Further, the minimum distance between the magnetic rotator and the inner wall of the through hole may be 100 μm or more. This allows the reduction effect of insertion loss to be exerted to the maximum extent. Further, the minimum distance between the magnetic rotator and the inner wall of the through hole may be 150 μm or less. This makes it possible to reduce insertion loss while sufficiently ensuring the effective area of the dielectric substrate. 
     The non-reciprocal circuit element according to the present disclosure may further include a connection pattern formed on the upper surface of the dielectric substrate and connected to the magnetic rotator, a terminal electrode formed on the lower surface of the dielectric substrate and connected to the connection pattern, and a ground pattern formed on the lower surface of the dielectric substrate, and a matching capacitance may be constituted by overlap between the connection pattern and the ground pattern, so that the lower surface of the dielectric substrate can be used as a mounting surface. This eliminates the need to use a composite part which is required to be produced by an insert molding method. Further, a capacitor pattern is provided in the dielectric substrate itself, eliminating the need to use a chip type matching capacitor, which makes it possible to reduce the number of components. 
     The non-reciprocal circuit element according to the present disclosure may further include upper and lower yokes sandwiching the dielectric substrate, magnetic rotator, and permanent magnet, and the lower surface of the dielectric substrate may have a recessed part accommodating a part of the lower yoke. This prevents interference between the lower yoke and a mounting substrate upon surface mounting. 
     As described above, according to the present disclosure, it is possible to reduce insertion loss in a non-reciprocal circuit element having a structure in which a magnetic rotator is accommodated in a through hole formed in a dielectric substrate.