Patent Document

The disclosure of Japanese Patent Application No. 2006-062660 filed Mar. 8, 2006 including specification, drawings and claims is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The present invention relates to an antenna device and a reception system for receiving radio waves of digital radio broadcasting. 
     In recent years, a digital radio receiver which receives a satellite wave or a terrestrial wave and provides digital radio broadcasting has been developed, and has been put to practical use in the United States. The digital radio receiver is mounted in a mobile station such as a vehicle so that radio waves in a frequency band of about 2.3 GHz are received, thus making it possible to provide radio broadcasting to the vehicle, for example. That is, the digital radio receiver is a radio receiver which can provide mobile broadcasting. Since frequencies of the received radio waves are in a frequency band of about 2.3 GHz, the received wavelength (resonance wavelength) ??at that time is about 128.3 mm. Further, the terrestrial wave stems from the satellite wave being received in an earth station and then the frequency of the wave being a little shifted and the wave being re-transmitted in a form of a linearly polarized wave. 
     In general, when the digital radio receiver is mounted in the vehicle, the antenna device is attached on the roof of the vehicle. As shown in  FIG. 1 , the antenna device  10  (for example, see Japanese Patent Publication No. 2005-109687, paragraph 0016 to 0022, FIG. 1) for such the digital radio receiver includes an antenna case  13  made by coupling a top cover  11  with a bottom plate  12 , an antenna module  14  disposed in the top cover  11 , a packing member  15  disposed in a junction portion of the top cover  11  and the bottom plate  12  and ensuring a sealing-ability of the antenna case  13 , and a signal line  16  connected to the antenna module  15 . 
     The antenna module  14  has an antenna element  20  in which an antenna receiving a signal transmitted from a satellite is formed and a circuit board  21  in which a circuit for performing a signal processing such as amplification of the signal received by the antenna element  20  is formed. The antenna element  20  and the circuit board  21  are joined each other by a two-sided tape  22  or the like. 
     A coaxial cable, as a signal line  16 , for fetching signals outside from the antenna case  13  is connected to the circuit board  21 . Further, in the circuit board  21 , a shield case  24  for shielding the circuit is attached on a main surface  21   b  opposite to a main surface  21   a  on which the antenna element  20  is disposed. The signal line  16  is drawn outside through a notch portion formed in the top cover  11 . 
     The antenna device  10  is united in one body by assembling the top cover  11  and the bottom plate  12  with the antenna module  14  and the packing member  15  housed in the inner space of the top cover  11 . The packing member  15  is made of a resin material such as an EPDM rubber. 
     When the top cover  11  and the bottom plate  12  are joined, the packing member  15  is interposed therebetween in order to ensure sealing-ability of the junction portion. A gasket  15   b  rises from a base  15   a  corresponding to the notch portion  11   a  of the top cover  11 . 
     A single concave portion  12   a  is formed on the center of the bottom plate  12  and a permanent magnet  30  is disposed in the concave portion  12   a . The permanent magnet  30  is disposed in order to attach the antenna device  10  on the roof of the vehicle. Further, on the outer main surface of the bottom plate  12 , a resin sheet  31  for preventing a damage of the vehicle is attached over the substantially entire surface of the main surface. A product number or name of the antenna device  10  is printed on the resin sheet  31 . 
     In the related-art antenna device having the above-mentioned structure, an antenna device in which a tuner unit is mounted has been put to practical use. In this type of the antenna device, the size of the circuit board  21  increases since the tuner unit is mounted. Consequently, the entire size of the antenna device is larger. 
     SUMMARY 
     It is therefore an object of the invention to minimize a size of the antenna module. 
     In order to achieve the above described object, according to the invention, there is provided an antenna module comprising: 
     a multilayered substrate including:
         a first layer; and   at least one second layer laminated on one face of the first layer;       

     a first component mounted on the other face of the first layer; 
     a second component comprised of a pattern formed on at least one second layer, and electrically connected to the first component through a via hole. 
     The antenna module may be integrated in an antenna device for receiving a satellite digital radio. 
     For example, an LNA (Low Noise Amplifier), a demodulating circuit, and an operating circuit are configured with the first component mounted on the first layer of the multilayered substrate and the second component built in the multilayered substrate. The first component may include a plurality of mounted components. The first component or mounted components may include a tuner IC. Therefore, the antenna module may be integrated with a tuner. 
     The multilayered substrate may be a Low Temperature Co-fired Ceramic (LTCC) multilayered substrate. 
     The second component may include a reactance element formed on the basis of at least one of a width, a length, and a shape of the pattern. With this configuration, it is not necessary to separately mount a condenser element or a coil element independent of a pattern on a layer within a spatial area of the multilayered substrate. Therefore, it is possible to minimize the first component. Consequently, the minimization in entire size of the antenna device may be achieved. 
     The second component may include at least one of an inductor, a filter, a balun, and a capacitor. More particularly, an inductor including a pattern of a substantially concentric polygon or a substantially concentric circle is conceivable. In addition, a capacitor respectively formed on the layers and including a pattern of electrode plates facing each other is conceivable. Furthermore, a balun including a first pattern which is formed on one layer of the second layers and which is in a form of a concentric polygon or a concentric circle and a second pattern which is formed on an adjacent layer and which is a form of a concentric polygon or a concentric circle corresponding to the first pattern is conceivable. 
     According to the invention there is also provided an antenna module, comprising: 
     a multilayered substrate; and 
     a first component mounted on the multilayered substrate, wherein: 
     the multilayered substrate is an low temperature co-fired ceramic multilayered substrate. 
     According to the invention, there is also provided an antenna device which includes the above-described antenna module. 
     With this configuration, the circuit board may be minimized as much as the amount of the first components in comparison with a related-art antenna module in which all components are mounted on the first layer of the multilayered substrate. Consequently, the antenna module may be minimized, and further it is possible to minimize the antenna device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein: 
         FIG. 1  is an exploded side view showing a structure of an antenna device used in the prior art and which can be used with modification according to an embodiment of the present invention; 
         FIG. 2  is a section view showing a circuit board according to the embodiment; 
         FIG. 3  is a perspective view showing an inductor according to the embodiment; 
         FIG. 4  is a perspective view showing a capacitor according to the embodiment; 
         FIG. 5  is a section view showing the capacitor according to the embodiment; 
         FIG. 6  is a schematic perspective view showing a balun according to the embodiment; 
         FIG. 7  is a diagram showing patterns of the balun formed on each of the layers of the multilayered substrate according to the embodiment; 
         FIG. 8  is a circuit diagram showing the balun; 
         FIG. 9  is a perspective view showing a filter according to the embodiment; 
         FIG. 10  is a diagram showing patterns of the filter formed on each of the layers of the multilayered substrate according to the embodiment; 
         FIG. 11  is a diagram showing wired lines between the patterns of the filter; 
         FIG. 12  is a diagram showing reactance formed in the filter of the multilayered substrate; and 
         FIG. 13  is a circuit diagram showing the filter. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, an embodiment of an antenna device according to the invention will be discussed with reference to the accompanying drawings. 
     A circuit board  40  according to an embodiment of the invention is described with reference to  FIG. 2 . The constituent elements equivalent to those of  FIG. 1  are denoted by the same reference numerals. The circuit board  40  is corresponding to the circuit board  21  in  FIG. 1 , includes a multilayered substrate  41  and a mounted component, and an antenna module includes the circuit board  40  and an antenna element  20 . The multilayered substrate  41  includes fifteen layers L 0  to L 14 . Further, the multilayered substrate formed of fifteen layers is used in the embodiment, but the invention is not limited to the above-mentioned configurations, and a multilayered substrate formed of less or more layers than the fifteen layers may be used. 
     The mounted components are elements  46 ,  47 , and  48  disposed on a main surface  41   b , a crystal oscillator  49 , a tuner IC  50 , and built-in components, such as inductors  51 , capacitors  52 , baluns  53 , and filters  54 , disposed in inner areas  51  to  54  of the multilayered substrate  41 . The mounted components on the main surface  41   b  and built-in components are connected through via holes, as not illustrated, passing through the multilayered substrate  41 . The mounted components disposed on the main surface  41   b  are covered with a shield case  24 . 
     A line width, a shape, and a length of the pattern in the layers of the multilayered substrate are properly determined and reactance elements such as a condenser and a coil are formed, the reactance elements are connected by the patterns within the same layer, and similarly are connected to the reactance elements or the wire patterns formed in the other layers through the via holes. Accordingly, the built-in components  51  to  54  are the circuits which may function as desired. 
     As shown in  FIG. 3 , the inductor  51  is formed of the pattern formed between the layer L 0  and the layer L 1  of the multilayered substrate  41 , that is, on the layer L 1 . The pattern is a substantially concentric rectangle or a substantially rectangular spiral. The inductor  51  is connected to the pattern on the main surface  41   b  from the center end and the outer peripheral end through the via holes  200  and  202  in layer L 0  hole. 
     As shown in  FIG. 4 , the capacitors  52  are formed in the eight layers of the layers L 0  to L 7  of the multilayered substrate  41 . The two via holes  80 ,  81  pass through all layers and the substantially rectangular patterns are formed in the layers L 1  to L 7  respectively. As shown in  FIG. 5 , since the patterns on the layers L 2 , L 4 , and L 6  are connected through the via hole  80  each other and the patterns on the layers L 1 , L 3 , L 5 , and L 7  are connected through the via hole  81  each other, the entirety functions as a capacitor. 
     With reference to  FIG. 6 , the baluns  53  are formed of the layers L 0  to L 12  of the multilayered substrate, and particularly, the main parts are formed in the layers L 6  to L 12 . The built-in components except for the baluns  53  may be formed in the layers L 0  to L 5 . For example, it is conceivable to form an inductor such as the inductor  51 . The baluns  53  are connected to the pattern on the main surface  41   b  through via holes  204 . 
     A structure of the balun  53  is also described with reference to  FIG. 7 . The layer L 6  is a GND layer. Spirals  96 ,  97  in a form of rectangle and patterns formed of a wire which connects the spiral  96 , the spiral  97  are formed on the layer L 9 . Patterns formed circular spiral  98 ,  99  are formed also on the layer L 10 . Wires connecting the spirals  98 ,  99  are not included in the patterns of the layer L 9  and the wires are formed in the pattern of the layer L 11 . Wire patterns are formed on the layers L 7 , L 8  so as to lead the wire patterns the spirals  96 ,  97 , and  98  and the wire pattern between the spiral  96  and the spiral  97  to terminals  100 ,  101 ,  102 , and  102 . 
     The terminal  100  is connected to the inner peripheral end of the spiral  98  through the via hole. The outer peripheral end of the spiral  98  is connected to one end of the pattern of the layer L 11  through the via hole and the other end connected to outer peripheral end of the spiral  99  through the via hole. The terminal  101  is connected to the inner peripheral end of the spiral  96  through the via hole, the terminal  102  is connected to the wire pattern between the spiral  96  and the spiral  97  through the via hole, and the terminal  103  connected to the inner peripheral end of the spiral  97  through the via hole. Since wired between the patterns as mentioned above, the spiral  96  and the spiral  98  and the spiral  97  and the spiral  99  are coupled in a high frequency respectively. Accordingly, the balun  53  functions as a circuit shown in  FIG. 8 . 
     The filter  54  is described with reference to  FIG. 9 . The multilayered substrate with the filter  54  is formed of patterns of the seven layers L 0  to L 6  and via holes  206  through which the patterns are connected. 
     The filter  54  is further described with reference to  FIG. 10 . The pattern on the layer L 0  is a GND layer. The pattern on the layer L 1  is formed of two rectangles  117 ,  118 . The pattern on the layer L 2  is formed of a rectangle  119 , a form of an inverse L  120 , and a form of L  121 . The pattern on the layer L 3  is formed of three rectangles  122  to  124 . The pattern on the layer L 4  is a wire pattern except for the filter  54 . The pattern on the layer L 5  is formed of a rectangle  125 . The pattern on the layer L 6  is a GND layer. These patterns are connected through the via holes as shown in  FIG. 11 . 
     According to above-mentioned structure, the reactance element is formed in the multilayered substrate. Reference numerals in  FIG. 12  are the same as those used in  FIG. 11 . As described with reference to  FIG. 12 , a capacitor  130  is formed between the rectangle  117  and the layer L 0  and a capacitor  131  is formed between the rectangle  118  and the layer L 0 . A capacitor  132  is formed between the rectangle  119  and the rectangle  122  and a capacitor  133  is formed between the rectangle  119  and the rectangle  124 . A capacitor  134  is formed between the form of inverse L  120  and the rectangle  122  and a capacitor  135  is formed between the inverse L  120  and the rectangle  123 . A capacitor  136  is formed between the form of L  121  and the rectangle  123  and a capacitor  137  is formed between the form of L  121  and the rectangle  124 . A capacitor  138  is formed between the rectangle  122  and the rectangle  123 . A capacitor  139  is formed between the rectangle  123  and the rectangle  124 . A capacitor  140  is formed between the rectangle  125  and the lower surface of the layer L 6 . Further, one ends of the rectangles  122 ,  123 , and  124  are connected to the rectangles  117 ,  118 , and  125  respectively and the other ends are grounded, whereby inductors  141 ,  142 , and  143  are formed. In addition, terminals  144 ,  145  are provided at ends of the short sides of the form of inverse L  120  and the form of L  121  respectively. Consequently, the formed capacitors and inductors make a filter circuit as shown in  FIG. 13 . 
     The invention is described on the basis of the embodiment but the invention is not limited to the above-mentioned configurations, and may be modified in a variety of forms by a person skilled in the art.

Technology Category: 5