Abstract:
A high-frequency apparatus includes a shielding plate that electrically shields any of a plurality of terminals protruding from a frame. An exposed portion of the terminal disposed between the frame and a motherboard is shielded by the shielding plate. Therefore, especially, a terminal that is likely to be adversely affected by an external wave can be electrically shielded by the shielding plate, the entry of an interfering wave into the terminal can be prevented, and high performance can be achieved.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a high-frequency apparatus that is suitably used in, for example, a digital broadcasting receiving tuner for a CATV.  
         [0003]     2. Description of the Related Art  
         [0004]      FIGS. 7 and 8  are a side view and a bottom view, respectively, showing the configuration of a high-frequency apparatus disclosed in Japanese Patent No. 2908967. In the high-frequency apparatus, a frame  51  is formed of a metal plate and is shaped like an open square. Two covers  52  are attached to the frame  51  so as to respectively cover two opposing open faces of the frame  51 .  
         [0005]     Although not shown, a circuit board having electronic components is placed in the frame  51 . A plurality of terminals  53  are arranged in line on the circuit board. The terminals  53  protrude downward from a bottom wall  51   a  of the frame  51 . Two legs  51   b  also protrude from the frame  51  in the same direction as that of the terminals  53 .  
         [0006]     As shown in  FIG. 7 , the high-frequency apparatus having this configuration is mounted on the motherboard  54  by fitting the legs  51   b  and the terminals  53  in a hole (not shown) of a motherboard  54 , and soldering the legs  51   b  and the terminals  53  to a conductive pattern (not shown) of the motherboard  54  while there is a space between the motherboard  54  and the bottom wall  51   a  through which the terminals  53  extend.  
         [0007]     However, when the above-described high-frequency apparatus is mounted on the motherboard  54 , the terminals  53  are exposed from the space between the motherboard  54  and the bottom wall  51   a , and an interfering wave enters the terminals  53  through the open space. In particular, an interfering wave enters an antenna terminal serving as one of the terminals  53 , and this reduces the performance of the apparatus.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention has been made in view of these circumstances of the related art, and an object of the invention is to provide a high-frequency apparatus having high performance and capable of preventing the entry of an interfering wave into terminals.  
         [0009]     In order to achieve the above object, a high-frequency apparatus according to an aspect of the present invention includes a frame formed of a metal plate; a circuit board mounted in the frame and having an electronic component to form a desired electric circuit; a plurality of terminals attached to the circuit board and protruding from the frame; and a shielding plate disposed outside the frame, the shielding plate electrically shielding at least one of the terminals and being electrically connected to the frame. The frame is mounted on a motherboard so that an exposed portion of the terminal disposed between the frame and the motherboard is shielded by the shielding plate.  
         [0010]     In this case, the shielding plate for electrically shielding any of the terminals protruding from the frame shields the exposed portion of the terminal disposed between the frame and the motherboard. Therefore, it is possible to electrically shield a terminal which is adversely affected by an external wave, to prevent the entry of an interfering wave into the terminal, and to thereby achieve high performance.  
         [0011]     Preferably, the at least one of the terminals is an antenna terminal. In particular, a digital broadcasting receiving tuner has a band of 800 MHz, which is equivalent to that of a mobile telephone. Therefore, it is possible to prevent the entry of an interfering wave from the mobile telephone to the antenna terminal, and to enhance the performance of the apparatus.  
         [0012]     Preferably, the at least one of the terminals includes an antenna terminal and a ground terminal adjacent to the antenna terminal, and the ground terminal is soldered to the shielding plate. In this case, the antenna terminal is surrounded by the shielding plate that is grounded by being connected to the ground terminal. This reliably prevents the entry of an interfering wave, and ensures high performance.  
         [0013]     Preferably, the shielding plate is formed of a resilient metal plate, and includes a flat portion and an elastic wall projecting from the flat portion toward the motherboard. Exposed portions of the antenna terminal and the ground terminal extend through the flat portion, and are surrounded by the elastic wall. The ground terminal is soldered to the flat portion. The elastic wall is in elastic contact with the motherboard when the frame is mounted on the motherboard. In this case, the exposed portions can be reliably shielded between the shielding plate and the motherboard, the entry of an interfering wave can be reliably prevented, and high performance can be achieved. In addition, since the ground terminal is soldered to the flat portion of the shielding plate, soldering to the shielding plate can be performed easily, and allows the shielding plate to be attached easily.  
         [0014]     Preferably, the shielding plate is formed of a resilient metal plate, and includes flat portion and an elastic wall projecting from the flat portion toward the frame. Exposed portions of the antenna terminal and the ground terminal are surrounded by the flat portion and the elastic wall. The ground terminal is soldered to the flat portion. The flat portion is in elastic contact with the motherboard when the frame is mounted on the motherboard. In this case, the exposed portions can be reliably shielded between the shielding plate and the frame, the entry of an interfering wave can be reliably prevented, and high performance can be achieved. In addition, since the ground terminal is soldered to the flat portion of the shielding plate, soldering to the shielding plate can be performed easily, and allows the shielding plate to be attached easily.  
         [0015]     Preferably, the shielding plate is in contact with a ground pattern provided on the motherboard. This makes grounding of the shielding plate more reliable.  
         [0016]     Preferably, the frame includes a bottom wall, a hole provided in the bottom wall so that the terminals extend therethrough, and a pair of legs protruding downward from the bottom wall so as to be attached to the motherboard. The shielding plate includes a projection projecting from the flat portion toward the legs, and an elastic tongue bent from the flat portion toward the bottom wall. The elastic tongue of the shielding plate is in elastic contact with the bottom wall near the hole while the projection is retained by the legs. In this case, the shielding plate can be properly positioned and held relative to the frame, and can be attached stably.  
         [0017]     According to the present invention, the shielding plate is provided to electrically shield any of a plurality of terminals protruding outside the frame, and the exposed portion of the terminal between the frame and the motherboard is shielded by the shielding plate. Therefore, especially, the exposed portion of a terminal that is likely to be adversely affected by an external wave can be electrically shielded by the shielding plate, the entry of an interfering wave into the terminal can be prevented, and high performance can be achieved. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is an exploded perspective view showing the principal part of a high-frequency apparatus according to a first embodiment of the present invention;  
         [0019]      FIG. 2  is a side view of the principal part of the first embodiment;  
         [0020]      FIG. 3  is a sectional side view of the principal part;  
         [0021]      FIG. 4  is a sectional front view of the principal part;  
         [0022]      FIG. 5  is an exploded perspective view showing the principal part of a high-frequency apparatus according to a second embodiment of the present invention;  
         [0023]      FIG. 6  is a sectional side view of the principal part of the second embodiment;  
         [0024]      FIG. 7  is a side view of a known high-frequency apparatus; and  
         [0025]      FIG. 8  is a bottom view of the known high-frequency apparatus. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     Embodiments of the present invention will be described below with reference to the attached drawings.  
         [0027]     FIGS.  1  to  4  show the configuration of a high-frequency apparatus according to a first embodiment of the present invention. The high-frequency apparatus includes a frame  1  formed of a metal plate. The frame  1  is shaped like an open square having opposing openings, and is constituted by a bottom wall  1   b  having a plurality of holes  1   a,  a pair of side walls  1   c  bent upward from two opposing sides of the bottom wall  1   b,  a pair of legs  1   d  projecting downward from the side walls  1   c  below the bottom wall  1   b,  and a top wall (not shown) provided between the side walls  1   c.    
         [0028]     The high-frequency apparatus also includes two covers  2  each formed of a metal plate. Each cover  2  includes a flat covering portion  2   a , and a resilient clamping portion  2   b  bent on the periphery of the covering portion  2   a  so as to clamp the frame  1 . The two covers  2  are attached to the frame  1  to form a housing and to electrically shield the interior of the frame  1 . In this state, the opposing openings of the frame  1  are closed by the covering portions  2   a , and the bottom wall  1   b,  the side walls  1   c,  and the top wall of the frame  1  are clamped by the clamping portions  2   b.    
         [0029]     A circuit board  3  has a wiring pattern  4 . Various electronic components  5  are mounted on the wiring pattern  4  to form a desired electric circuit. A plurality of terminals  6  arranged in line are attached to the circuit board  1  such as to be connected to the wiring pattern  4  and to protrude from one side (bottom face) of the circuit board  1 . Among the terminals  6 , an antenna terminal  6   a  and a ground terminal  6   b  are adjacent to each other.  
         [0030]     The circuit board  3  having this structure is mounted in the frame  1  by an appropriate means. The terminals  6  attached to the circuit board  3  protrude outside through the holes  1   a  of the bottom wall  1   b.  The antenna terminal  6   a  and the ground terminal  6   b  protrude through the same one opening  1   a.    
         [0031]     A shielding plate  7  formed of a resilient metal plate includes a rectangular flat portion  7   a , a pair of first elastic walls  7   b  bent and inclined downward from opposing long sides of the flat portion  7   a , a projection  7   c  projecting from the center of one short side of the flat portion  7   a , an elastic tongue  7   d  inclined upward and projecting from the center of the other short side of the flat portion  7   a , a pair of second elastic walls  7   e  bent and inclined downward from the other short side of the flat portion  7   a , and large and small holes  7   f  and  7   g  provided in the flat portion  7   a.    
         [0032]     When the shielding plate  7  is mounted in position, the flat portion  7   a  faces the bottom wall  1   b,  an exposed portion of the antenna terminal  6   a  protrudes downward from the frame  1  through the large hole  7   f  without contact with the flat portion  7   a , an exposed portion of the ground terminal  6   b  protrudes downward from the frame  1  through the small hole  7   g , the projection  7   c  is retained between the legs  1   d,  and the elastic tongue  7   d  is in elastic contact with the bottom wall  1   b  near the hole  1   a.    
         [0033]     In this case, as shown in FIGS.  2  to  4 , the first elastic walls  7   b  are in elastic contact with the roots of the clamping portions  2   b  of the covers  2 , the projection  7   c  is in elastic contact with the roots of the legs  1   d,  and portions of the antenna terminal  6   a  and the ground terminal  6   b  other than the exposed leading ends are surrounded by the shielding plate  7 . The ground terminal  6   b  is joined to the flat portion  7   a  of the shielding plate  7  by solder  8 . In this way, the high-frequency apparatus of the first embodiment is constructed.  
         [0034]     The high-frequency apparatus having this configuration is applied, for example, to a digital broadcasting receiving tuner for a CATV. As shown in FIGS.  2  to  4 , the terminals  6  are fitted in holes (not shown) provided in a motherboard  9 , and are soldered to a wiring pattern (not shown) provided on the motherboard  9 .  
         [0035]     In this case, the shielding plate  7  surrounds the antenna terminal  6   a  and the ground terminal  6   b , and the first and second elastic walls  7   b  and  7   e  are in elastic contact with the motherboard  9 , so that there is no space between the shielding plate  7  and the motherboard  9 . The ground terminal  6   b  and the shielding plate  7  are grounded by being connected to a ground pattern  10  provided on the motherboard  9 .  
         [0036]      FIGS. 5 and 6  show a high-frequency apparatus according to a second embodiment of the present invention. In the second embodiment, first and second elastic walls  7   b  and  7   e  of a shielding plate  7  are bent toward a bottom wall  1   b  of a frame  1 , and are in elastic contact with the frame  1 . Exposed portions of an antenna terminal  6   a  and a ground terminal  6   b  disposed between the bottom wall  1   b  and a flat portion  7   a  of the shielding plate  7  are surrounded by the flat portion  7   a  and the first and second elastic walls  7   b  and  7   e . The flat portion  7   a  is pressed by a motherboard  9 .  
         [0037]     Other structures are similar to those in the first embodiment. Like components are denoted by like reference numerals, and descriptions thereof are omitted.  
         [0038]     It should be noted that the shielding plate  7  can have various structures other than the structures in the above-described embodiments.