Abstract:
A method of manufacturing a non-reciprocal component including a casing having an input/output terminal and a ground terminal formed therein, a ferrite plate, a line conductor, and a magnet disposed in the casing, and an upper yoke and a lower yoke provided at the top face and the bottom face of the casing, respectively. In the non-reciprocal component, the casing is insert-molded with the lower yoke so that a portion of the casing penetrates through the lower yoke. A side of the component is defined partly by the lower yoke and partly by the penetrating portion of the casing. An input/output terminal and a ground terminal in the casing are defined by respective portions of a molded hoop material.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a division of U.S. patent application Ser. No. 09/608,157, filed Jun. 30, 2000 now U.S. Pat. No. 6,469,588 in the name of Toshihiro MAKINO, Hiroki DEJIMA, Takashi KAWANAMI, Takashi HASEGAWA, Masakatsu MORI AND Takahiro JODO and entitled NONRECIPROCAL DEVICE AND COMMUNICATION DEVICE USING THE SAME. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a non-reciprocal component, such as a circulator or an isolator, used in a microwave band or the like, and to a communication device using the same. 
     2. Description of the Related Art 
     The construction of a conventional lumped-constant isolator used in a microwave band or the like is shown as an exploded perspective view thereof in  FIG. 14 . 
     A casing  1  is a box resin casing, which is open at the top face thereof as observed in  FIG. 14 . Various terminals are provided in this casing  1 . In the condition shown in this figure, one input/output (I/O) terminal  2   a  and ground terminals  3  appear, and an exposed part of another I 10  terminal  2   b  appears inside the casing  1 . A lower yoke  9  is mounted on the casing  1 . Inside the casing  1 , capacitors  7   a,    7   b,  and  7   c,  a chip resistor  8 , a ferrite plate  5 , line conductors  4   a,    4   b,    4   c,  and a magnet  6  are placed in this order. An upper yoke  10  covers the top face of the casing  1 . 
     However, such a conventional isolator has a problem in that when the casing  1  and the lower yoke  9  are assembled by soldering the lower yoke  9  to terminals provided in the casing  1 , since a sufficient soldered area thereof cannot be obtained, adequate bonding strength cannot be secured. This may lead to a reduction in reliability of an electronic device. For example, an impact from dropping causes the soldered parts of the electronic device to come off. Furthermore, when the lower yoke  7  and the casing  1  are soldered, there is a risk that since the I/O terminals  2   a  and  2   b  and the ground terminals  3  do not form the same plane due to mismatching between the sizes of components on the lower yoke  9  and the sizes of components on the casing  1 , some of the terminals may be raised. As a result, when characteristics of this isolator are to be measured, there is a problem in that measurement cannot be performed because terminals of a measuring jig are not properly connected to the I/O terminals  2   a  and  2   b  or ground terminals  3 . 
     Furthermore, since various terminals provided in the casing  1  and the lower yoke  9  are always provided as discrete components, there is a problem in that reduction of cost cannot be obtained due to reduction of the number of components. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a non-reciprocal component in which the foregoing problems are solved, shock resistance and dimensional accuracy of terminal parts are enhanced, and reduction of cost is easily achieved, and a communication device using the same. 
     To this end, according to a first aspect of the present invention, there is provided a non-reciprocal component that includes a casing having an I/O terminal and a ground terminal formed therein; a ferrite plate, a transmission line conductor, and a magnet stored in the casing; and an upper yoke and a lower yoke provided at the top face and the bottom face of the casing, respectively. In the non-reciprocal component, the casing is insert-molded with the lower yoke. 
     This construction allows sufficient shock resistance to be secured. In addition, since there is no need to solder the lower yoke to the terminals provided in the casing, dimensional accuracy of the positions of the terminals is increased. 
     In this non-reciprocal component, the lower yoke, the I/O terminal, and the ground terminal may be formed by molding a hoop material. This construction enables the lower yoke and the casing to be insert-molded in succession, and the lower yoke, the I/O terminal, and the ground terminal to be formed using the same material. Accordingly, the number of parts can be reduced. 
     In the non-reciprocal component, a portion of the lower yoke may be exposed as the ground terminal from the casing. This construction allows the distance between the ground terminal and the lower yoke to be minimized, which minimizes residual inductance. 
     In the non-reciprocal component, alternatively, the ground terminal is protruded outside the lower yoke, and the ground terminal has a solder resist film formed at the base thereof. Because of this, when mounting is performed on a circuit substrate of an electronic device, solder is prevented from flowing into the bottom face of the lower yoke, which enables soldering to be performed only on terminal parts. 
     In the non-reciprocal component, the thickness of the lower yoke, the thickness of the I/O terminal, and the thickness of the ground terminal are 0.3 mm or less. 
     According to a second aspect of the present invention, a communication device is provided with a non-reciprocal component according to the first aspect of the present invention. For example, the communication device is constructed by providing the non-reciprocal component as a circulator in which a transmission signal and a reception signal are branched. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of an isolator according to a first embodiment; 
         FIGS. 2A to 2C  are three views of the isolator; 
         FIG. 3  is a circuit diagram of the isolator; 
         FIG. 4  is a graph showing frequency characteristics of the insertion loss of the isolator in a narrow frequency band; 
         FIG. 5  is a graph showing frequency characteristics of the insertion loss of the isolator in a wide frequency band; 
         FIGS. 6A to 6C  are three views of an isolator according to a second embodiment; 
         FIGS. 7A to 7C  are illustrations showing manufacturing processes of an isolator according to a third embodiment; 
         FIG. 8  is an illustration showing a state in which a casing is insert-molded along with a lower yoke and terminals; 
         FIGS. 9A to 9C  are three views of the isolator; 
         FIG. 10  is an illustration showing the construction of an isolator according to a fourth embodiment in a hoop material; 
         FIGS. 11A to 11C  are three views of the isolator; 
         FIGS. 12A to 12C  are three view of an isolator according to a fifth embodiment; 
         FIG. 13  is a block diagram showing the construction of a communication device according to a sixth embodiment; and 
         FIG. 14  is an exploded perspective view of a conventional isolator. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The construction of an isolator according to a first embodiment of the present invention is described with reference to  FIGS. 1 to 5 . 
       FIG. 1  is an exploded perspective view of the isolator. The isolator is constructed as follows. A resin casing  1  is insert-molded along with a lower yoke  9  made of a magnetic material, I/O terminals  2   a  and  2   b,  and ground terminals  3 . The ground terminals  3  are integrated with the lower yoke  9 , and the I/O terminals  2   a  and  2   b  are insulated from the lower yoke  9 . Inner ends of the two I/O terminals  2   a  and  2   b  are exposed at the inner bottom face of the casing  1 . Capacitors  7   a,    7   b,  and  7   c,  and a chip resistor  8  are disposed in the casing. The top faces and the bottom faces of the capacitors  7   a,    7   b,  and  7   c,  and the chip resistor  8 , as observed in the figure, serve as electrode faces. Transmission line conductors (central conductors)  4   a,    4   b,  and  4   c,  a ferrite plate  5 , and a magnet  6  are stored in the casing  1  so that the line conductors  4   a,    4   b,  and  4   c  are held between the ferrite plate  5  and the magnet  6 . Finally, an upper yoke  10  made of a magnetic material covers an opening of the casing  1 . 
       FIGS. 2A ,  2 B and  2 C show three views of the above-described isolator;  FIG. 2A  is a front view thereof;  FIG. 2B  is a bottom view thereof; and  FIG. 2C  is a right-side view thereof. Parts of the lower yoke  9  are extended as the four ground terminals  3 , and the casing  1  is insert-molded along with the ground terminals  3  and the I/O terminals  2   a  and  2   b . In this manner, by insert-molding the casing  1  along with the lower yoke  9 , there is no need to solder the lower yoke  9  to the terminals provided in the casing  1 . Accordingly, shock resistance is enhanced. In addition, the positional accuracy (planar accuracy) of the I/O terminals  2   a  and  2   b  and the ground terminals  3  is improved. Therefore, when isolator characteristics are measured, connection failure between a measuring jig and the isolator can be prevented. When the isolator is mounted on a mounting substrate, raising of the terminals can be avoided. 
       FIG. 3  is a circuit diagram of the above-described isolator. The circuit of the I/O terminals  2   a  and  2   b  is constructed as follows. The line conductors  4   a ,  4   b , and  4   c  cross one another so as to establish a mesh connection. One end of each of the line conductors is grounded, while the other end thereof and the ground have matching capacitors  7   a ,  7   b , and  7   c  inserted therebetween. The chip resistor  8  is connected as a termination resistor between the non-grounded terminal of the line conductor  4   c  and the ground. Because of this construction, non-reciprocal property can be obtained between the I/O terminals  2   a  and  2   b . For example, a signal passes from the I/O terminal  2   a  to the I/O terminal  2   b  with low reflection, whereas a signal that is input to the I/O terminal  2   b  is hardly output from the I/O terminal  2   a  due to attenuation in the resistor  8 . 
       FIGS. 4 and 5  show frequency characteristics of the insertion loss of the isolator. In both figures, the solid lines represent characteristics of the isolator according to this embodiment of the present invention, and, for comparison, the dashed-lines represent those of an isolator having a conventional construction. In this first embodiment, since the ground terminals  3  are provided as integrally formed portions of the lower yoke  9 , the lengths of the ground terminals are minimized, and residual inductance is maintained small, which improves the ground circuit. Consequently, as shown in  FIG. 4 , low loss is realized and the bandwidth of a characteristic band in which the isolator can be operative is expanded. In addition, since unnecessary radiation decreases, a large amount of attenuation can be obtained in a high frequency region, as shown in  FIG. 5 . 
     Furthermore, since the ground terminals  3  are provided as integral parts of the lower yoke  9 , heat that is generated at the chip resistor  8  functioning as a terminator flows into a ground plane of the mounting substrate via the lower yoke  9  functioning as a ground plate and the ground terminals. Accordingly, heat radiation is improved and electrical power resistant of the isolator is enhanced. Since the operating temperature of the isolator is maintained low due to the radiation, the reliability thereof is increased. 
     The construction of an isolator according to a second embodiment is described with reference to  FIGS. 6A to 6C . 
       FIGS. 6A ,  6 B, and  6 C show three views of the isolator;  FIG. 6A  is a front view thereof;  FIG. 6B  is a bottom view thereof; and  FIG. 6C  is a right-side view thereof. In this embodiment as well, the ground terminals  3  are formed one after another so as to be protruded outside the lower yoke  9 . Solder resist films  11  are formed by printing or the like at the corresponding bases of these ground terminals apart from the actual operative regions thereof. The solder resist films  11  are formed at proximal ends of the ground terminals  3  exposed on an outer bottom surface of the isolator. Otherwise, the construction of the isolator is identical to that shown in the first embodiment. Therefore, since the solder resist films  11  are located on the bases of the ground terminals  3  extending from the lower yoke  9 , when this isolator is mounted on a mounting substrate of an electronic device, solder does not flow into the inner bottom surface of the lower yoke  9  from the ground terminals  3 . Accordingly, the I/O terminals  2   a  and  2   b  and the ground terminals  3  can be firmly soldered to the mounting substrate. 
     The construction of an isolator according to a third embodiment is described with reference to  FIGS. 7A to 9C . 
       FIGS. 7A to 7C  are illustrations of a process for forming the lower yoke  9  and each of the terminals thereof. In these figures, a hoop material  12  made of a magnetic material obtained by forming a plated film on an iron plate, such as Ag, Ni, Au, or Cu, having a thickness of 0.3 mm or less. Sprocket holes  15  are formed so that the hoop material  12  is fed along the longitudinal direction of the hoop material  12 . 
     As shown in  FIG. 7A , by applying die-cutting to a hoop material  12 , a part  9 ′ to later become the lower yoke  9  is molded while maintaining connection with the frame part of the hoop material  12  via connecting parts  14 . At the same time, cut-and-raised pieces  13   a  to  13   f  are formed. 
     As shown in  FIG. 7B , the lower yoke  9  is formed by folding the part  9 ′ at the two-dot chain lines shown in  FIG. 7A . However, up to this point, the lower yoke  9  still maintains connection with the hoop material  12  via the connecting parts  14 . 
     As shown in  FIG. 7C , by folding the cut-and-raised pieces  13   a  to  13   f  by approximately 180 degrees, the ends thereof are disposed so as to flank the lower yoke  9 . These ends are to be used later as the I/O terminals  2   a  and  2   b , and the ground terminals  3 . 
     Since the thickness of the hoop material  12  is 0.3 mm or less, it is easy to fold the lower yoke  9  and to cut and raise the cut-and-raised pieces  13   a  to  13   f.    
       FIG. 8  illustrates a process that follows the processes shown in  FIGS. 7A to 7C . The casing  1  is insert-molded along with the lower yoke  9  and the cut-and-raised pieces  13   a  to  13   f . At this time, ends of the cut-and-raised pieces  13   c  and  13   f  are exposed as inner terminals of the I/O terminals  2   a  and  2   b  at the inner bottom face of the casing  1 . Ends of the other cut-and-raised pieces  13   a ,  13   b ,  13   d , and  13   e  are exposed as inner terminals of the ground terminals  3  at the inner bottom face of the casing  1 . 
     From the condition shown in  FIG. 8 , the cut-and-raised pieces  13   a  to  13   f  are cut off along the two-dot chain lines. Parts of the cut-and-raised pieces protruded from the sides of the casing  1  are folded, whereby the I/O terminals  2   a  and  2   b  and the ground terminals  3  are formed. 
       FIGS. 9A ,  9 B, and  9 C show three views of the isolator;  FIG. 9A  is a front view thereof;  FIG. 9B  is a bottom view thereof; and  FIG. 9C  is a right-side view thereof. The I/O terminals  2   a  and  2   b , and the ground terminals  3  are formed with the same materials as those of the lower yoke  9 . In addition, they are insert-molded with the casing  1 . Accordingly, shock resistance is enhanced, and the positional accuracy of the I/O terminals  2   a  and  2   b , and the ground terminals  3  are also enhanced. 
     The construction of an isolator according to a fourth embodiment of the present invention is described with reference to  FIGS. 10 to 11C . 
       FIG. 10  shows the construction of the hoop material  12  before insert-mold formation of the casing  1 . The lower yoke  9  made of the magnetic material establishes connection via the connecting parts  14  with frame parts of the hoop material  12  made of the magnetic material. The cut-and-raised pieces  13   c  and  13   f  are cut and raised from the hoop material  12  and are folded by approximately 180 degrees. 
     From the state shown in  FIG. 10 , a resin to be the casing  1  is insert-molded. Then, the connecting parts  14  and the cut-and-raised pieces  13   c  and  13   f  are cut off along the two-dot chain lines, and parts of the cut-and-raised pieces protruding from the sides of the casing  1  are folded, whereby the I/O terminals  2   a  and  2   b  and the ground terminals  3  are formed. 
       FIGS. 11A ,  11 B, and  11 C show three views of the isolator constructed by the above-described processes;  FIG. 11A  is a front view thereof;  FIG. 11B  is a bottom view thereof; and  FIG. 11C  is a right-side view thereof. Connecting parts between the lower yoke  9  and the hoop material  12  can be simply used as ground terminals  3 . 
       FIGS. 12A ,  12 B, and  12 C show three views showing the construction of an isolator according to a fifth embodiment of the present invention. In  FIGS. 12A to 12C , a solder resist films  11  are formed at the bases of the ground terminals  3 . Otherwise, the construction of the isolator is identical to that of the isolator shown in  FIG. 11 . By forming the solder resist films  11  at the bases of the ground terminals  3 , when this isolator is mounted on the mounting substrate of the electronic device, solder does not flow into the (inner) bottom face of the lower yoke  9  from the ground terminals  3 . Accordingly, the I/O terminals  2   a  and  2   b , and the ground terminals  3  are firmly soldered to the mounting substrate. 
       FIG. 13  shows a block diagram of the construction of a communication device. In each of the foregoing embodiments, an example in which the two-port isolator is constructed by incorporating the three-port circulator and the terminating resistor therein is shown. When an end of the line conductor  4   c , which is connected to the chip resistor  8  shown in  FIGS. 1 and 3 , is an I/O terminal, the three-port circulator can be constructed. Port # 1  of the circulator constructed in the above-described manner is connected to an output unit of a transmission circuit, port # 2  thereof is connected to an antenna, and port # 3  thereof is connected to an input unit of a reception circuit. Thus, the communication device is constructed, in which the circulator is used as a branching circuit for transmission and reception.