Abstract:
Disclosed herein is a non-reciprocal circuit device includes: a first substrates including a magnetic plate having a circular surface and a dielectric ring having an annular surface, the circular surface and the annular surface being substantially coplanar; a second substrate; a center conductor provided between the first substrate and the second substrate; and a permanent magnet that applies a magnetic field to the center conductor. The center conductor includes: a main conductor portion positioned on a straight line extending from a center of the circular surface to an outer periphery of the annular surface; and a protrusion portion having a width smaller than a width of the main conductor portion, and wherein at least a part of the protruding portion is positioned on the annular surface.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a non-reciprocal circuit device and a communication apparatus using the same and, more particularly, to a non-reciprocal circuit device of a distributed constant type and a communication apparatus using the same. 
     Description of Related Art 
     A non-reciprocal circuit device such as an isolator or a circulator is incorporated in, for example, a mobile communication apparatus like a mobile phone or a communication apparatus used in a base station. The non-reciprocal circuit devices can be classified into a distribution constant type, a concentrated constant type, and the like. Among them, the non-reciprocal circuit device of the distribution constant type is suitable for use in a base station and the like where high power output signal is required. 
     A structure of the distribution constant type non-reciprocal circuit device is described in, e.g., Japanese Patent Application Laid-Open No. 1997-121104. The non-reciprocal circuit device described in Japanese Patent Application Laid-Open No. 1997-121104 has a center conductor including three conductors (main conductor portions) extending radially at an angular interval of 120° and three electrode portions (branched conductor portions) extending radially from the roots of the main conductor portions at an angular interval of 120°. This center conductor is placed on a substrate. The substrate is an integrated substrate made up of a ferrite plate in disk shape and a dielectric ring surrounding the ferrite. A leading end of each of the three main conductor portions is connected to an input/output terminal or a terminal resistor, whereby a signal is input/output or terminated. The three branched conductor portions are designed to have such a shape and a size as to obtain intended high-frequency characteristics (e.g., capacitance). 
     In the non-reciprocal circuit device described in Japanese Patent Application Laid-Open No. 1997-121104, the leading ends of the respective main conductor portions are expanded in a peripheral direction, and the expanded portions cover the dielectric ring. In this case, a large part of the dielectric ring is covered by the center conductor, so that a local stress is less likely to be applied to the dielectric ring during assembly of the non-reciprocal circuit device. 
     However, when a size of the expanded portion of each of the main conductor portions is reduced in order to obtain intended high-frequency characteristics, the dielectric ring is exposed from the center conductor over a wide range. When the non-reciprocal circuit device is assembled in such a condition, a local stress is applied to some part of the dielectric ring, which may damage the integrated substrate. 
     In order to prevent the integrated substrate from being damaged, a larger part of the dielectric ring needs to be covered by the center conductor. However, the shape and size of the center conductor are restricted in order to obtain intended high-frequency characteristics, which makes it difficult to adopt such a configuration, depending on the intended high-frequency characteristics. 
     SUMMARY 
     An object of the present invention is therefore to provide a non-reciprocal circuit device capable of preventing damage of the substrate during assembly while ensuring intended high-frequency characteristics and a communication apparatus using the non-reciprocal circuit device. 
     As a result of intensive study by the present inventors to achieve the above object, it was found that making an elongated center conductor extend on an annular surface of a dielectric ring in a protruding manner can prevent the substrate from being damaged during assembly while ensuring desired high-frequency characteristics. 
     The present invention has been made based on such technical knowledge, and a non-reciprocal circuit device according to the present invention includes: a first substrates including a magnetic plate having a circular surface and a dielectric ring having an annular surface, the circular surface and the annular surface being substantially coplanar; a second substrate; a center conductor provided between the first substrate and the second substrate; and a permanent magnet that applies a magnetic field to the center conductor. The center conductor includes: a main conductor portion positioned on a straight line extending from a center of the circular surface to an outer periphery of the annular surface; and a protrusion portion having a width smaller than a width of the main conductor portion, and wherein at least a part of the protruding portion is positioned on the annular surface. 
     A communication apparatus according to the present invention includes the above non-reciprocal circuit device. 
     According to the present invention, the protruding portion having the small width is positioned on the annular surface, thereby preventing the dielectric ring from being exposed from the center conductor over a wide range. This makes it less likely for a local stress to be applied to a specific portion of the dielectric ring when the first and second substrates are overlapped with each other sandwiching the center conductor, thereby preventing the substrate from being damaged during assembly. In addition, the protruding portion has an elongated shape, so that an area of the dielectric ring that is covered by the center conductor can be sufficiently reduced. As a result, it is possible to properly obtain intended high-frequency characteristics while preventing damage of the substrate. 
     In the present invention, it is preferable that the center conductor further includes a branched conductor portion integrally formed with the main conductor portion, at least a part of the branched conductor portion being positioned on the circular surface, and that the protruding portion protrudes in a radial direction from a radial edge of the branched conductor portion. With this configuration, it is possible to prevent damage of the substrate by the protruding portion while ensuring the intended high-frequency characteristics by the branched conductor portion. 
     In this case, it is preferable that the radial edge of the branched conductor portion has first and second end portions in a peripheral direction of the first substrate, and that the protruding portion includes first and second portions that protrude in the radial direction from the first and second end portions of the branched conductor portion, respectively. With this configuration, the protruding portions can be disposed in a distributed manner, thereby making it possible to effectively prevent concentration of a local stress. 
     In this case, it is more preferable that the protruding portion further includes a third portion connecting leading ends of the first and second portions. With this configuration, a larger part of the dielectric ring is covered by the protruding portion, thereby making it possible to effectively prevent concentration of a local stress. 
     In the present invention, it is preferable that the main conductor portion includes first, second, and third main conductor portions extending radially from the center of the circular surface at an angular interval of about 120°, that the branched conductor portion includes first, second, and third branched conductor portions extending radially from the center of the circular surface at an angular interval of about 120° so that the first, second, and third branched conductor portions form an angle of about 60° with the first, second, and third main conductor portions, respectively, and that the first and second portions of the protruding portion protrude in the radial direction from the respective first and second end portions of each of the first, second, and third branched conductor portions. With this configuration, there can be provided a non-reciprocal circuit device having three input/output terminals. 
     In the present invention, it is preferable that the radial edge of the branched conductor portion is positioned on the circular surface, thereby the protruding portion extends across a boundary between the circular surface and the annular surface. With this configuration, even if a displacement occurs in a mounting position of the center conductor, it is possible to minimize influence on the high-frequency characteristics. 
     In the present invention, it is also preferable that the protruding portion is branched from the main conductor portion and extends in the peripheral direction on the annular surface. Also with this configuration, it is possible to prevent damage of the substrate by the protruding portion while ensuring the intended high-frequency characteristics by the branched conductor portion. 
     In the present invention, it is preferable that the second substrate has substantially the same configuration as that of the first substrate. With this configuration, there can be provided a non-reciprocal circuit device having more satisfactory high-frequency characteristics. 
     As described above, according to the present invention, there can be provided a non-reciprocal circuit device capable of preventing damage of the substrate during assembly while ensuring intended high-frequency characteristics and a communication apparatus using the non-reciprocal circuit device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above features and advantages of the present invention will be more apparent from the following description of certain preferred embodiments taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view illustrating a configuration of a non-reciprocal circuit device according to a preferred embodiment of the present invention; 
         FIG. 2  is a plan view for explaining a shape of the center conductor and a positional relationship between the center conductor and the first substrate in a first embodiment; 
         FIG. 3  is a plan view for explaining a shape of the center conductor and a positional relationship between the center conductor and the first substrate in a comparative example; 
         FIG. 4  is a plan view for explaining a shape of the center conductor and a positional relationship between the center conductor and the first substrate in a second embodiment; and 
         FIG. 5  is a block diagram illustrating a configuration of a communication apparatus using the non-reciprocal circuit device according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is an exploded perspective view illustrating a configuration of a non-reciprocal circuit device according to a preferred embodiment of the present invention. 
     The non-reciprocal circuit device illustrated in  FIG. 1  is a distributed constant type isolator and is incorporated in a mobile communication apparatus like a mobile phone or a communication apparatus used in a base station. Although not especially limited, the non-reciprocal circuit device according to the present embodiment is suitable for use in a high-output communication apparatus used in a base station. However, the non-reciprocal circuit device of the present embodiment is not necessarily used as the isolator, but may be used as a circulator and the like. 
     As illustrated in  FIG. 1 , the non-reciprocal circuit device of the present embodiment includes a magnetic rotor assembly  10 , a case part  20  housing the magnetic rotor assembly  10 , and a lid part  30  for closing the case part  20 . 
     The magnetic rotor assembly  10  has a configuration in which a first permanent magnet  12 , a shield plate  13 , a first substrate  14 , a center conductor  15 , a second substrate  16 , a first non-magnetic sheet  17 , a second permanent magnet  18 , and a second non-magnetic sheet  19  which are stacked in the mentioned order and integrated with one another by a not illustrated conductive bonding agent. 
     Each of the first and second permanent magnets  12  has a disk shaped body having a plate surface diameter of several tens of mm and each have a role of applying a magnetic field to a magnetic rotor constituted by the first substrate  14 , the center conductor  15 , and the second substrate  16 . The second permanent magnet  18  is sandwiched between the first and second non-magnetic sheets  17  and  19 . 
     The shield plate  13  is a disk shaped conductor plate punched from a copper plate or an iron plate having a plate surface diameter of several tens of mm and a thickness of about 0.1 mm to 0.2 mm and is used for strengthening and stabilizing a ground electrode. 
     The first substrate  14  is constituted by a disk-shaped magnetic plate  14 A and a dielectric ring  14 B fitted around the disk-shaped magnetic plate  14 A. As a material for the disk-shaped magnetic plate  14 A, a soft magnetic member such as yttrium/iron/garnet (YIG) is preferably used. As a material for the dielectric ring  14 B, a ceramic having a desired dielectric constant is preferably used. A circular surface SA which is a main surface of the disk-shaped magnetic plate  14 A and an annular surface SB which is a main surface of the dielectric ring  14 B constitute the same plane. Thus, the disk-shaped magnetic plate  14 A and the dielectric ring  14 B have substantially the same thickness (e.g., about 1.0 mm). A diameter of the first substrate  14  is several tens of mm. 
     Like the above first substrate  14 , the second substrate  16  is constituted by a disk-shaped magnetic plate  16 A and a dielectric ring  16 B fitted around the disk-shaped magnetic plate  16 A. 
     The center conductor  15  is a conductor plate obtained by processing a copper plate having a thickness of about 0.1 mm to 1.0 mm and includes first to third main conductor portions  41  to  43  and first to third branched conductor portions  51  to  53 . The first to third main conductor portions  41  to  43  are conductor portions connected respectively to their corresponding terminals and extend radially from a center of the center conductor  15  at an angular interval of 120°. In the present embodiment, a leading end of the first main conductor portion  41  is connected to a terminal resistor  29 , a leading end of the second main conductor portion  42  is connected to a pin terminal P 2 , and a leading end of the third main conductor portion  43  is connected to a pin terminal P 3 . Each of the pin terminals P 2  and P 3  is used as an input/output terminal of the isolator. When the non-reciprocal circuit device according to the present embodiment is used as a circulator, the first main conductor portion  41  is connected not to the terminal resistor  29 , but to another pin terminal. 
     The first to third branched conductor portions  51  to  53  are integrally formed with the main conductor portions  41  to  43  and extend radially from a center of the circular surface SA at an angular interval of 120°. Among the six conductor portions  41  to  43  and  51  to  53 , two conductor portions disposed adjacent to each other in a peripheral direction form an angle of 60°. A shape of the center conductor  15  and a positional relationship between the center conductor  15  and first substrate  14  will be described later. 
     The magnetic rotor assembly  10  is housed in the case part  20 . The case part  20  is formed into a substantially cylindrical body or a substantially container-like body and has, therein, a housing portion  20 A which is a space for housing the magnetic rotor assembly  10 . An internal shape of the case part  20  is substantially cylindrical as a whole. The case part  20  is preferably formed of a magnetic metal material such as iron to thereby function as a yoke for the magnetic rotor assembly  10  housed in the housing portion  20 A. 
     The housing portion  20 A of the case part  20  is defined by three side walls  21  to  23  and a bottom portion  24  constituting a bottom surface portion. The side walls  21  to  23  stand on the same circumference from a periphery of the bottom portion  24  at a predetermined interval from one another and each have, at one of both standing end surfaces, a concave portion (concave portions  21 A to  23 A) cut along the peripheral direction. 
     Opening portions  25  to  27  are formed at portions at which adjacent end edges of the side walls  21  to  23  face each other. The leading ends of the first to third main conductor portions  41  to  43  are led outside from the opening portions  25  to  27 . 
     The lid part  30 , in which a lid plate portion  30 A constituting a main part thereof has a disk shape as a whole, is used as a lid for closing the housing portion  20 A when being combined with the case part  20 . That is, a shape of the lid part  30  is determined depending on an internal shape of the case part  20  in terms of its intended use. In the present embodiment, the case part  20  has a substantially cylindrical shape and, accordingly, the lid part  30  is formed into a disk shape. The lid part  30  is preferably formed of a magnetic metal material such as iron to thereby function as a yoke for the magnetic rotor assembly  10  together with the case part  20 . 
     The lid plate portion  30 A of the lid part  30  has a diameter and a contour shape that can be fitted to an opened end surface of the case part  20 . In other words, the lid plate portion  30 A has a shape having a diameter slightly smaller than an internal diameter of the opened end surface of the case part  20 . With this configuration, when the lid plate portion  30 A is fitted to the opened end surface of the case part  20 , a height of the non-reciprocal circuit device can be reduced by a thickness of the lid plate portion  30 A. Preferably, an upper surface of the lid plate portion  30 A and an upper end surface constitute substantially the same plane. 
     The lid plate portion  30 A has a circular outer shape and has convex portions  31  to  33  at its circular outer peripheral surface. The convex portions  31  to  33  are fitted into the concave portions  21 A to  23 A of the case part  20 , respectively. Thus, the convex portions  31  to  33  have a width (thickness) corresponding to that of the concave portions  21 A to  23 A and are formed at intervals corresponding to intervals at which the concave portions  21 A to  23 A are formed. The convex portions  31  to  33  each have a simple shape obtained by making the outer peripheral surface of the l id plate portion  30 A radially protrude. 
     Leading ends of the convex portions  31  to  33  are inserted into the concave portions  21 A to  23 A, respectively, and then, the lid part  30  or the case part  20  is rotated relatively. As a result, the case part  20  and the lid part  30  can be fitted to each other in a convex and concave way. 
     The bottom portion  24  constituting the case part  20  has a protruding portion  28  radially protruding through the opening portion  25 . The protruding portion  28  is provided with the terminal resistor  29  for absorbing reflective waves. With this configuration, the non-reciprocal circuit device according to the present embodiment can be used as an isolator. 
       FIG. 2  is a plan view for explaining a shape of the center conductor  15  and a positional relationship between the center conductor  15  and the first substrate  14  in a first embodiment. 
     As illustrated in  FIG. 2 , the center conductor  15  has the first to third main conductor portions  41  to  43  and the first to third branched conductor portions  51  to  53 , all of which are positioned on the circular surface SA of the magnetic plate  14 A or annular surface SB of the dielectric ring  14 B. 
     The first main conductor portion  41  has a linear portion  41 A linearly extending from a center of the circular surface SA to an outer periphery of the annular surface SB, and has two protruding portions  61  and  62  branched from the linear portion  41 A and extending in the peripheral direction. The second main conductor portion  42  has a linear portion  42 A linearly extending from the center of the circular surface SA to the outer periphery of the annular surface SB, and has two protruding portions  63  and  64  branched from the linear portion  42 A and extending in the peripheral direction. The third main conductor portion  43  has a linear portion  43 A linearly extending from the center of the circular surface SA to the outer periphery of the annular surface SB, and has two protruding portions  65  and  66  branched from the linear portion  43 A and extending in the peripheral direction. 
     The linear portions  41 A to  43 A each extend radially over the circular surface SA and the annular surface SB, while the protruding portions  61  to  66  each extend in the peripheral direction on the annular surface SB. A width (width in the radial direction) of each of the protruding portions  61  to  66  is smaller than a width (width in the peripheral direction) of each of the linear portions  41 A to  43 A. 
     As described above, the protruding portions  61  to  66  branched from the main conductor portions  41  to  43  each extend in an elongated shape in the peripheral direction on the annular surface SB of the dielectric ring  14 B and can thus cover the dielectric ring  14 B over a wider range while reducing an area of the dielectric ring  14 B that is covered by the center conductor  15 . 
     The first branched conductor portion  51  is positioned between the linear portions  41 A and  42 A and radially extends from the center of the circular surface SA. The second branched conductor portion  52  is positioned between the linear portions  42 A and  43 A and radially extends from the center of the circular surface SA. The third branched conductor portion  53  is positioned between the linear portions  43 A and  41 A and radially extends from the center of the circular surface SA. 
     A width (width in the peripheral direction) of each of the branched conductor portions  51  to  53  is larger than a width of each of the linear portions  41 A to  43 A. A large part of each of the branched conductor portions  51  to  53  is positioned on the circular surface SA of the magnetic plate  14 A, but a part thereof is positioned on the annular surface SB of the dielectric ring  14 B. 
     Specifically, edges  51 A to  53 A of the branched conductor portions  51  to  53  in the radial direction are disposed at positions slightly offset to the circular surface SA side from a boundary between the circular surface SA and the annular surface SB. The edge  51 A has a first end portion  51 A 1  and a second end portion  51 A 2  in the peripheral direction, from which two protruding portions  71  and  72  radially protrude, respectively. The edge  52 A has a first end portion  52 A 1  and a second end portion  52 A 2  in the peripheral direction, from which two protruding portions  73  and  74  radially protrude, respectively. The edge  53 A has a first end portion  53 A 1  and a second end portion  53 A 2  in the peripheral direction, from which two protruding portions  75  and  76  radially protrude, respectively. 
     The protruding portions  71  to  76  each extend across the boundary between the circular surface SA and the annular surface SB and each mostly positioned on the annular surface SB of the dielectric ring  14 B. A width (width in the peripheral direction) of each of the protruding portions  71  to  76  is smaller than the width (width in the peripheral direction) of each of the linear portions  41 A to  43 A. 
     As described above, the protruding portions  71  to  76  protruding from the branched conductor portions  51  to  53  each extend in an elongated shape in the radial direction on the annular surface SB of the dielectric ring  14 B and can thus cover the dielectric ring  14 B over a wider range while reducing the area of the dielectric ring  14 B that is covered by the center conductor  15 . 
     As described above, in the present embodiment, the elongated protruding portions  61  to  66  extending in the peripheral direction and the elongated protruding portions  71  to  76  extending in the radial direction are disposed on the annular surface SB of the dielectric ring  14 B. This makes it possible to cover the dielectric ring  14 B over a wide range by the center conductor  15  while reducing the area of the dielectric ring  14 B that is covered by the center conductor  15 . 
     Thus, a stress to be applied to the dielectric ring  14 B (and dielectric ring  16 B) when the first and second substrates  14  and  16  are overlapped with each other through the center conductor  15  is dispersed, making it less likely for a local stress to be applied to a specific portion, which can prevent the substrate from being damaged during assembly. In addition, the protruding portions  61  to  66  and  71  to  76  each have an elongated shape, so that the area of the dielectric ring  14 B (and dielectric ring  16 B) that is covered by the center conductor  15  can be sufficiently reduced. As a result, it is possible to reduce influence that the protruding portions  61  to  66  and  71  to  76  have on the high-frequency characteristics, thereby allowing intended high-frequency characteristics to be obtained properly. 
     Further, in the present embodiment, the elongated protruding portions  71  to  76  extends across the boundary between the circular surface SA and the annular surface SB, so that even if a displacement occurs when the center conductor  15  is overlapped on the first substrate  14 , a change in an area of the magnetic plate  14 A (and magnetic plate  16 A) that is covered by the center conductor  15  and a change in the area of the dielectric ring  14 B (and dielectric ring  16 B) that is covered by the center conductor  15  are small. Thus, it is possible to suppress a change in the high-frequency characteristics due to the displacement. 
       FIG. 3  is a plan view for explaining a shape of the center conductor  15  and a positional relationship between the center conductor  15  and the first substrate  14  in a comparative example. 
     In the comparative example illustrated in  FIG. 3 , the width of each of the protruding portions  61  to  66  is larger than that in the first embodiment, and the edges  51 A to  53 A of the branched conductor portions  51  to  53  extend up to the annular surface SB of the dielectric ring  14 B. Further, in the comparative example, the protruding portions  71  to  76  are not provided. Although there are such differences in shape, the area of the magnetic plate  14 A that is covered by the center conductor  15  and the area of the dielectric ring  14 B that is covered by the center conductor  15  are almost the same as those of the first embodiment illustrated in  FIG. 2 . Thus, the high-frequency characteristics to be obtained are not changed significantly. 
     However, in the comparative example of  FIG. 3 , the width of each of the protruding portions  61  to  66  is large and, accordingly, a length thereof in the peripheral direction becomes necessarily small. Further, the branched conductor portions  51  to  53  do not have the protruding portions  71  to  76 . As a result, the annular surface SB of the dielectric ring  14 B is exposed from the center conductor  15  over a wide range, so that a local stress is applied to a specific portion of the dielectric ring  14 B when the first substrate  14 A and the second substrate  16 A are overlapped with each other through the center conductor  15 , which may damage the substrates  14 A and  16 A. In particular, when a strong stress is applied near the edges  51 A to  53 A of the branched conductor portions  51  to  53 , a part of the dielectric ring  14 B near an inner periphery thereof which is easy to be damaged is pressed strongly, with the result that substrates  14 A and  16 A damage may easily occur. 
     On the other hand, such problems can be solved by the above-described first embodiment, and thus it is possible to effectively prevent the substrate from being damaged during assembly. 
     Further, in the comparative example of  FIG. 3 , a body part of each of the branched conductor portions  51  to  53  having a large width extends across the boundary between the circular surface SA and the annular surface SB, so that when a displacement occurs when the center conductor  15  is overlapped on the first substrate  14 , the area of the magnetic plate  14 A that is covered by the center conductor  15  and the area of the dielectric ring  14 B that is covered by the center conductor  15  significantly change. 
     On the other hand, such a problem can be solved by the above-described first embodiment, and thus it is possible to suppress the change in the high-frequency characteristics due to the displacement. 
       FIG. 4  is a plan view for explaining a shape of the center conductor  15  and a positional relationship between the center conductor  15  and the first substrate  14  in a second embodiment. 
     The center conductor  15  according to the second embodiment differs from the center conductor  15  illustrated in  FIG. 2  in that protruding portions  77  to  79  are added. Other points are the same as those of the center conductor  15  illustrated in  FIG. 2 , so the same reference numerals are given to the same parts, and the repeated description will be omitted. 
     The protruding portion  77  constitutes apart of the first branched conductor portion  51  and extends on the annular surface SB in the peripheral direction so as to connect the protruding portions  71  and  72 . The protruding portion  78  constitutes a part of the second branched conductor portion  52  and extends on the annular surface SB in the peripheral direction so as to connect the protruding portions  73  and  74 . The protruding portion  79  constitutes a part of the third branched conductor portion  53  and extends on the annular surface SB in the peripheral direction so as to connect the protruding portions  75  and  76 . 
     A width of each of the protruding portions  77  to  79  in the radial direction is substantially the same as the width of each of the protruding portions  71  to  76  in the peripheral direction and is, accordingly, smaller than the width of each of the linear portions  41 A to  43 A in the peripheral direction. 
     Such a configuration is suitable for use in a case where a larger capacitance than that in the first embodiment illustrated in  FIG. 2  is required. According to the second embodiment, a larger capacitance than that in the first embodiment can be obtained, and the dielectric ring  14 B can be covered by the center conductor  15  over a wider range and with higher density than in the first embodiment, thereby making it possible to prevent more effectively damage of the substrate during assembly. 
       FIG. 5  is a block diagram illustrating a configuration of a communication apparatus  80  using the non-reciprocal circuit device according to the present embodiment. 
     The communication apparatus  80  illustrated in  FIG. 5  is provided in a base station for, e.g., a mobile communication system. The communication apparatus  80  includes a receiver circuit section  80 R and a transmission circuit section  80 T, which are connected to a transmission/reception antenna ANT. The receiver circuit section  80 R includes a receiver amplifier circuit  81  and a receiver circuit  82  that processes a received signal. The transmission circuit section  80 T includes a transmission circuit  83  that generates an audio signal, a video signal, or the like and a power amplifier circuit  84 . 
     In the thus configured communication apparatus  80 , non-reciprocal circuit devices  91  and  92  of the present embodiment are connected respectively to a path from the antenna ANT to the receiver circuit section  80 R and a path from the transmission circuit section  80 T to the antenna ANT. The non-reciprocal circuit device  91  functions as a circulator, and non-reciprocal circuit device  92  functions as an isolator having a terminal resistor R 0 . 
     It is apparent that the present invention is not limited to the above embodiments, but may be modified and changed without departing from the scope and spirit of the invention.