Patent Publication Number: US-8111197-B2

Title: Antenna apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an antenna apparatus. 
     2. Description of Related Art 
     In recent years, an antenna apparatus of an in-vehicle GPS system which is widely spread as a positioning system, and an antenna apparatus of a home use satellite radio or an in-vehicle satellite radio or the like which is put to practical use in the United States, have been developed progressively. Such a conventional antenna apparatus has a structure shown in  FIG. 6 , for example (see Japanese Parent Application Laid-open No. 2005-109688). 
     As shown in  FIG. 6 , the conventional antenna apparatus  100  includes an antenna element  102  made of ceramic for receiving a radio wave and a circuit substrate  103  which is stuck to a back face of the antenna element  102 . An amplifying circuit (not shown) for amplifying an input from the antenna element  102  is formed on a face of the circuit substrate  103  on the opposite side of the antenna element  102 . The face on which the amplifying circuit is formed is covered by a shield cover  104  having an approximately box-shaped body. The circuit substrate  103  and the antenna element  102  adhere to one another with a double-sided tape (not shown). A power supply pin  106 , which passes through the circuit substrate  103  and the antenna element  102 , is fixed to the circuit substrate  103  and the antenna element  102 . A tip end portion of the power supply pin  106  is soldered to the amplifying circuit on the circuit substrate  103  to achieve an electrical connection. Accordingly, a radio wave signal received by the antenna element  102  is inputted to the amplifying circuit via the power supply pin  106 . 
     As with the other electronic parts, it is hoped that antenna apparatuses will be thinner. It is also hoped that the cost of parts and the assembling cost will be reduced by reducing the number of parts to achieve reduction of manufacturing cost. 
     SUMMARY OF THE INVENTION 
     It is, therefore, a main object of the present invention to provide a thin antenna apparatus with a small number of parts. 
     According to a first aspect of the present invention, there is provided an antenna apparatus, including: a multi-layer substrate having at least two substrates in a stacking manner and having a first through hole passing through at least one of the substrates; an amplifying circuit formed on one face of the multi-layer substrate; a ground pattern which is made of a metal film and which is formed between two adjacent substrates of the multi-layer substrate; an antenna pattern which is made of a metal film and which is formed on the other face of the multi-layer substrate; a first comb electrode formed around the antenna pattern on the other face of the multi-layer substrate, the first comb electrode, which has comb teeth and is made of a metallic film, being electrically connected to the antenna pattern; and a second comb electrode formed around the antenna pattern on the other face of the multi-layer substrate, the second comb electrode, which has comb teeth, being electrically connected to the ground pattern through the first through hole, wherein the comb teeth of the first comb electrode and the comb teeth of the second comb electrode are spaced from one another at predetermined intervals in a staggered mariner. 
     According to a second aspect of the present invention, there is provided an antenna apparatus, including: a multi-layer substrate having at least a top layer substrate, an intermediate layer substrate, and a bottom layer substrate in a stacking manner and having a first through hole passing through the top layer substrate, and having a second through hole passing through the intermediate layer substrate; an amplifying circuit formed on the bottom layer substrate; a ground pattern formed on one face of the intermediate layer substrate; an antenna pattern, formed on the top layer substrate; a first comb electrode which is formed on the other face of the intermediate layer substrate so that the first comb electrode and the antenna pattern stack with one another, and which has comb teeth and is made of a metallic film and is electrically connected to the antenna pattern through the first through hole; and a second comb electrode which is formed on the other face of the intermediate layer substrate so that the second comb electrode and the antenna pattern stack with one another, and which has comb teeth and is made of a metal lie film and is electrically connected to the ground pattern through the second through hole, wherein the comb teeth of the first comb electrode and the comb teeth of the second comb electrode are spaced from one another at predetermined intervals in a staggered manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, advantages and features of the present invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention, and wherein: 
         FIG. 1  is a schematic perspective view of an antenna apparatus according to preferred embodiments of the present invention; 
         FIG. 2  is a schematic top view of the antenna apparatus; 
         FIG. 3  is a cross sectional view taken from line III-III of  FIG. 2 ; 
         FIG. 4  is a cross sectional view taken from line IV-IV of  FIG. 2 ; 
         FIG. 5  is a schematic cross sectional view of an antenna apparatus according to a modification of the embodiments; and 
         FIG. 6  shows a schematic cross-sectional view of a conventional antenna apparatus. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An antenna apparatus of preferred embodiments of the present invention will be explained below with reference to the drawings. 
       FIG. 1  is a schematic perspective view of the antenna apparatus.  FIG. 2  is a top view of the antenna apparatus. As shown in  FIG. 1  and  FIG. 2 , the antenna apparatus  1  includes a multi-layer substrate  2  and an amplifying circuit  3  which is provided on a lower face (one face) of the multi-layer substrate  2 . 
     Two substrates  21  and  22 , which are made of glass-epoxy material, are stacked to form the multi-layer substrate  2 . A ground pattern  23  made of a metal film is formed between the substrates  21  and  22  (see  FIG. 3  and  FIG. 4 ). An antenna pattern.  24  made of a metal film is formed on an upper face (the other face) of the multi-layer substrate  2 , namely, on a surface of the substrate  21 . The antenna pattern.  24  constitutes a receiving face for receiving a radio wave. The external shape of the antenna pattern  24  is a quadrangle when viewed from the top. An opening portion  25  as a long hole is formed in a central, portion of the antenna pattern  24  to expose a face of the substrate  21 . The external shape of the antenna pattern  24  or the opening portion  25  depends on the frequency of the radio wave to be received by the antenna apparatus  1 . A through hole (a second through hole)  26  is formed in the vicinity of the opening portion  25  in the antenna pattern  24 . 
       FIG. 3  is a cross sectional view taken from line III-III of  FIG. 2  and shows a schematic structure of the through hole  26 . As shown in  FIG. 3 , the through hole  26  penetrates the substrates  21  and  22 . An inner circumference face of the through hole  26  is covered by a metallic film  27 . The metallic film  27  is connected to the amplifying circuit  3  and the antenna pattern  24 . Accordingly, the antenna pattern  24  and the amplifying circuit  3  are electrically connected via the through hole  26 . The ground pattern  23  has no contact with the metallic film  27  of the through hole  26 . 
     A plurality of first comb electrodes  31  made of a metallic film are formed around the antenna pattern  24  on the upper face of the multi-layer substrate  2 , and are electrically connected to the antenna pattern  24 . Each of the first, comb electrodes  31  includes a base line portion  32  which is led to the antenna pattern  24  and comb teeth  33  which are led from an end of the case line portion  32 . 
     A plurality of second comb electrodes  41  are formed around the antenna pattern  24  on the upper face of the multi-layer substrate  2  as counterparts of the first comb electrodes  31 . Each of the second comb electrodes  41  includes a base line portion  42  which is led to a through hole (a first through hole)  28  formed in the multi-layer substrate  2  and comb teeth  43  which are led from an end of the base line portion  42 . The comb teeth  43  of the second comb electrode  41  are spaced from the comb teeth  33  of the first comb electrode  31  at predetermined intervals in a staggered manner. 
       FIG. 4  is a cross sectional view taken from line IV-IV of  FIG. 2  and shows a schematic structure of the through hole  28 . As shown in  FIG. 4 , the through hole  28  passes through the substrate  21 . An inner circumference face of the through hole  28  is covered by a metallic film  29 . The metallic film  29  is connected to the ground pattern  23  and the base line portion  42  of the second comb electrode  41 . Accordingly, the second comb electrode  41  is electrically connected to the ground pattern  23  via the through hole  28 . 
     Next, the operation of the antenna apparatus  1  will be explained. 
     When the radio wave is received by the antenna pattern  24 , the radio wave signal is transmitted to the amplifying circuit  3  via the metallic film  27  of the through hole  26 . The radio wave signal is amplified by the amplifying circuit  3  and the amplified signal is outputted to an external device. As described above, the comb teeth  33  of the first comb electrode  31  and the comb teeth  43  of the second comb electrode  41  are spaced from one another at predetermined intervals in a staggered manner. With this structure, at the time of receiving the radio wave, the first comb electrode  31  and the second comb electrode  41  function as capacitors to achieve a radiation pattern having capacitance. 
     According to this embodiment, because the antenna pattern  24  made of a metallic film is formed on the multi-layer substrate  2 , the entire multi-layer substrate  2  can function as an antenna element. Because the antenna element formed of the multi-layer substrate  2  is thinner than a conventional antenna element which is made of ceramic, it is possible to achieve a thin antenna apparatus  1  as a whole. 
     Further, the first comb electrodes  31 , which are electrically connected to the antenna pattern  24 , and the second comb electrodes  41  are arranged around the antenna pattern  24 . With this structure, the first comb electrode  31  and the second comb electrode  41  function as capacitors to achieve a radiation pattern having capacitance. Consequently, it is possible to provide the antenna apparatus  1  whose radiation pattern is the same as that of the conventional antenna element and whose surface area is small. 
     In the conventional antenna apparatus, an antenna element and a circuit substrate are provided as separate bodies, and both are fixed with a double-sided tape. In this embodiment, because the multi-layer substrate  2  itself is an antenna element, the double-sided tape is not needed any more. 
     With this, it is possible to provide the thin antenna apparatus  1  with a small number of parts. 
     Further, the antenna pattern  24  and the amplifying circuit  3  are electrically connected via the through hole  26  in the multi-layer substrate  2 . This structure makes it possible to achieve the electrical connection between the antenna pattern  24  and the amplifying circuit  3  without a power supply pin which was one of the necessary parts of the conventional antenna apparatus. Therefore, an antenna apparatus with a small number of parts can be accomplished. 
     The present invention is not limited to the above-described embodiment. Various modifications can be made without departing from the scope of the invention. 
     The same reference number will be used below to refer to the same parts of the above-described embodiment without adding explanation. 
     In the above-described embodiment, four combinations of the first comb electrode  31  and the second comb electrode  41  are disposed for each side of the antenna pattern  24 . It will be apparent to those skilled in the art that more than four combinations of the first comb electrode  31  and the second comb electrode  41  can be employed. It should be noted that four combinations of the first comb electrode  31  and the second comb electrode  41  are preferable because frequency can easily be adjusted. 
     The multi-layer substrate  2  is formed of glass-epoxy substrates in the above-described embodiment. Other material whose permittivity is smaller than that of ceramic may be employed as a material of the multi-layer substrate  2 . 
     Further, the multi-layer substrate  2  includes two substrates  21  and  22  in the above-described embodiment. Three or more substrates may constitute the multi-layer substrate. In this case, the first comb electrode and the second comb electrode can be formed at an interlayer which is different from an interlayer for the ground pattern. Specifically, an antenna apparatus  1 A shown in  FIG. 5  includes a multi-layer substrate  5  having three substrates  51 ,  52  and  53  which are made of glass-epoxy. 
     In antenna pattern  24   a  is formed on a face of the substrate  51  as a top layer. An amplifying circuit  3   a  is disposed on a face of the substrate  53  as a bottom layer. A first comb elect rode  31   a  and a second comb electrode  41   a  are disposed between the substrate  51  and the intermediate substrate  52 . A ground pattern  23   a  is disposed between the intermediate substrate  52  and the substrate  53 . 
     The multi-layer substrate  5  includes a through hole  26   a  which penetrates the substrates  51 ,  52  and  53 , a through hole  28   a  which penetrates the substrate  51 , and a through hole  28   b  which penetrates the substrate  52 . 
     An inner circumference face of the through hole  26   a  is covered by a metallic film  27   a . The metallic film  27   a  is connected to the amplifying circuit  3   a  and the antenna pattern  24   a . Accordingly, the antenna pattern  24   a  and the amplifying circuit  3   a  are electrically connected via the through hole  26   a . Here, also in this case, the ground pattern  23   a  has no contact with the metallic film  27   a  of the through hole  26   a.    
     An inner circumference face of the through hole  28   a  is covered by a metallic film  29   a . The metallic film  29   a  is connected to the first comb electrode  31   a  and the antenna pattern  24   a . Accordingly, the first, comb electrode  31   a  and the antenna pattern  24   a  are electrically connected via the through hole  28   a.    
     An inner circumference face of the through hole  28   b  is covered by a metallic film  29   b . The metallic film  29   b  is connected to the ground pattern  23   a  and the second comb electrode  41   a . Accordingly, the second comb electrode  41   a  and the ground pattern  23   a  are electrically connected via the through hole  28   b.    
     According to the antenna apparatus  1 A, because the first comb electrode  31   a  and the second comb electrode  41   a  are formed at the interlayer which is different from the interlayer for the ground pattern  23   a , the first comb electrode  31   a  and the second comb electrode  41   a  can be arranged below the antenna pattern  24   a . With this structure, a surface area of the antenna apparatus  1 A can be smaller than that of an antenna apparatus in which the first comb electrode and the second comb electrode are formed around the antenna pattern  24   a.    
     According to a first aspect of the preferred embodiments of the present invention, there is provided an antenna apparatus, including: a multi-layer substrate having at least two substrates in a stacking mariner and having a first through hole passing through at least one of the substrates; an amplifying circuit formed on one face of the multi-layer substrate; a ground pattern which is made of a metal film and which is formed between two adjacent substrates of the multi-layer substrate; an antenna pattern which is made of a metal film and which is formed on the other face of the multi-layer substrate; a first comb electrode formed around the antenna pattern on the other face of the multi-layer substrate, the first comb electrode, which has comb teeth and is made of a metallic film, being electrically connected to the antenna pattern; and a second comb electrode formed around the antenna pattern on the other face of the multi-layer substrate, the second comb electrode, which has comb teeth, being electrically connected to the ground pattern through the first through hole, wherein the comb teeth of the first comb electrode and the comb teeth of the second comb electrode are spaced from one another at predetermined intervals in a staggered manner. 
     Preferably, the multi-layer substrate further has a second through hole through which the antenna pattern is electrically connected to the amplifying circuit. 
     Preferably, the multi-layer substrate is formed of glass-epoxy substrates. 
     According to a second aspect of the preferred embodiments of the present invention, there is provided an antenna apparatus, including: a multi-layer substrate having at least a top layer substrate, an intermediate layer substrate, and a bottom layer substrate in a stacking manner and having a first through hole passing through the top layer substrate, and having a second through hole passing through the intermediate layer substrate; an amplifying circuit formed, on the bottom layer substrate; a ground pattern formed on one face of the intermediate layer substrate; an antenna pattern formed on the top layer substrate; a first comb electrode which is formed on the other face of the intermediate layer substrate so that the first comb electrode and the antenna pattern stack with one another, and which has comb teeth and is made of a metallic film and is electrically connected to the antenna, pattern through the first through hole; and a second comb electrode which is formed on the other face of the intermediate layer substrate so that the second comb electrode and the antenna pattern stack with one another, and which has comb teeth and is made of a metallic film and is electrically connected to the ground pattern through the second through hole, wherein the comb teeth of the first comb electrode and the comb teeth of the second comb electrode are spaced from one another at predetermined intervals in a staggered manner. 
     Because the multi-layer substrate having at least two glass-epoxy substrates has a dielectric constant er of 4 to 5, the multi-layer substrate can function as an antenna element as a whole if the antenna pattern made of a metal film is formed on the multi-layer substrate. Because the antenna element formed of the multi-layer substrate is thinner than a conventional antenna element which is made of ceramic, it is possible to achieve a thin antenna apparatus as a whole. 
     However, the dielectric constant of the multi-layer substrate is drastically smaller than that of the conventional ceramic antenna element. Therefore, a surface area of the multi-layer substrate must be large in order to obtain the same radiation pattern as that of the conventional antenna element. 
     To avoid this drawback, in the preferred embodiment of the present invention, tine comb teeth of the first comb electrode and the comb teeth of the second comb electrode are spaced from one another at predetermined intervals in a staggered manner around the antenna pattern. With this structure, the first comb electrode and the second comb electrode function as capacitors to achieve a radiation pattern having capacitance. Consequently, it is possible to provide an antenna apparatus whose radiation pattern is the same as that of the conventional antenna element and whose surface area is small. 
     In the conventional antenna apparatus, an antenna element and a circuit substrate are provided as separate bodies, and both are fixed with a double-sided tape. In the preferred embodiment of the present invention, because the multi-layer substrate itself is an antenna element, the double-sided tape is not needed, any more. 
     With this, it is possible to provide a thin antenna apparatus with a small number of parts. 
     The entire disclosure of Japanese Patent Application No. 2008-322030 filed on Dec. 18, 2008 including description, claims, drawings, and abstract are incorporated herein by reference in its entirety. 
     Although various exemplary embodiments have been shown and described, the invention is not limited to the embodiments shown. Therefore, the scope of the invention is intended to be limited solely by the scope of the claims that follow.