Patent Publication Number: US-2010127940-A1

Title: Antenna device, radio communication equipment, surface-mounted antenna, printed circuit board, and manufacturing method of the surface-mounted antenna and the printed circuit board

Description:
TECHNICAL FIELD 
     The present invention relates to an antenna device, radio communication equipment, a surface-mounted antenna, a printed circuit board, and a manufacturing method of the surface-mounted antenna and the printed circuit board. 
     BACKGROUND OF THE INVENTION 
     In recent years, compact communication terminal devices such as cellular phones which solely cope with plural radio communication systems using a surface-mounted inverted-F antenna, such as wireless LAN, GPS, and Bluetooth®, have appeared. The frequencies of electric waves used by these radio communication systems are typically different from each other. Plural surface-mounted antennas are provided in one compact mobile terminal device, which cannot make the compact communication terminal device smaller. The study for coping with the plural radio communication systems of different frequencies by one surface-mounted antenna is being advanced. 
     One of the candidates of such surface-mounted antennas which are now being studied is a multiple-resonance antenna. This has plural radiation electrodes whose lengths and widths are different from each other on one base surface and supplies power from one power supply line to all the radiation electrodes. Its specific example is shown in FIGS. 1, 4, 6, and 8 of Japanese Patent No. 3319268. 
     SUMMARY OF THE INVENTION 
     In the multiple-resonance antenna described in Japanese Patent No. 3319268, capacitance power supply having a gap between the power supply line and the radiation electrode is adopted. The characteristic of the resonance antenna responds to the length and width of the gap very sensitively. Therefore, if the manufacturing accuracy of the gap is low, the manufacturing variation in impedance is increased. Additionally, an electric field concentrates on the gap portion, therefore the resonance antenna is susceptible to an outside influence. 
     There, it is considered to let the power supply method be direct power supply. But, the direct power supply causes another problem that the impedance matching between the resonance antennas becomes difficult. This will be described below in detail. 
     The impedance matching between the resonance antennas of the multiple-resonance antenna is preferable. In the multiple-resonance antenna adopting capacitance power supply, the impedance for each of the resonance antennas can be controlled relatively easily by controlling the length and width of the gap for capacitance power supply. Therefore, the impedance matching between the resonance antennas is relatively easy. 
     On the other hand, the gap for capacitance power supply does not exist in the multiple-resonance antenna adopting direct power supply. Therefore, the impedance control for each of the resonance antennas cannot be performed. The impedance matching between the resonance antennas becomes difficult. 
     An object of the present invention is to provide an antenna device which can realize the impedance matching between resonance antennas of a surface-mounted multiple-resonance antenna of a direct power supply type by a simple configuration, radio communication equipment, a surface-mounted antenna, a printed circuit board, and a manufacturing method of the surface-mounted antenna and the printed circuit board. 
     An antenna device according to the present invention to achieve the above object includes a substrate having a power supply line and a ground pattern, and a surface-mounted multiple-resonance antenna having a base and a conductor pattern formed on the base and provided on the substrate, wherein the conductor pattern includes plural antenna conductor patterns and a plane conductor pattern which connects each of the antenna conductor patterns and the power supply line, wherein the plane conductor pattern includes a slit which controls the connection distance between at least a portion of each of the antenna conductor patterns and the power supply line, wherein the substrate has a land pattern which connects each of the antenna conductor patterns and the ground pattern and does not have a conductor pattern in a region corresponding to the slit. 
     The impedance of the resonance antenna varies according to the length of a power supply path to the antenna conductor pattern. According to the present invention, the impedance matching between the resonance antennas of the surface-mounted multiple-resonance antenna of a direct power supply type can be realized by the simple configuration of the slit. 
     In the antenna device, each of the antenna conductor patterns may include a power supply electrode formed on the side surface of the base, the plane conductor pattern may be formed on the bottom surface of the base and connect the power supply electrode and the power supply line, and the slit may be provided between the power supply line and each of the power supply electrodes. With this, the length of the power supply path to each of the antenna conductor patterns can be controlled by adjusting the depth of the slit. 
     In the antenna device, each of the plural antenna conductor patterns may include a top surface conductor pattern formed on the top surface of the base, and the conductor pattern may include each conductor pattern provided in the position of the bottom surface of the base opposite each of the top surface conductor patterns. With this, it becomes easier to realize the impedance matching between the resonance antennas. 
     An antenna device of another aspect of the present invention includes a substrate having a power supply line and a ground pattern, and a surface-mounted multiple-resonance antenna having a base and plural antenna conductor patterns formed on the base and provided on the substrate, wherein the substrate has a land pattern which connects each of the antenna conductor patterns, the power supply line, and the ground pattern, wherein the land pattern includes a slit which controls the connection distance between at least a portion of each of the antenna conductor patterns and the power supply line, wherein the surface-mounted multiple-resonance antenna does not have a conductor pattern on the surface corresponding to the slit. With this, the impedance matching between the resonance antennas of the surface-mounted multiple-resonance antenna of a direct power supply type can be realized by the simple configuration of the slit. 
     In the antenna device, each of the antenna conductor patterns may include a power supply electrode formed on the side surface of the base, the land pattern may be formed under the base and connect each of the power supply electrodes and the power supply line, and the slit may be provided between the power supply line and the power supply electrode. With this, the length of the power supply path to each of the antenna conductor patterns can be controlled by adjusting the depth of the slit. 
     Radio communication equipment according to the present invention has at least one of the antenna devices. 
     A surface-mounted multiple-resonance antenna according to the present invention has a base and a conductor pattern formed on the base and provided on a substrate having a power supply line, wherein the conductor pattern includes plural antenna conductor patterns and a plane conductor pattern which connects each of the antenna conductor patterns and the power supply line, wherein the plane conductor pattern includes a slit which controls the connection distance between at least a portion of each of the antenna conductor patterns and the power supply line. 
     A printed circuit board according to the present invention has a power supply line and a ground pattern and on which a surface-mounted multiple-resonance antenna having plural antenna conductor patterns formed on a base is provided, and includes a land pattern which connects each of the antenna conductor patterns, the power supply line, and the ground pattern, wherein the land pattern includes a slit which controls the connection distance between at least a portion of each of the antenna conductor patterns and the power supply line. 
     A manufacturing method of a surface-mounted multiple-resonance antenna according to the present invention has a base and provided on a substrate having a power supply line, wherein a conductor pattern which has plural antenna conductor patterns and a plane conductor pattern which connects each of the antenna conductor patterns and the power supply line and includes a slit which controls the connection distance between at least a portion of each of the antenna conductor patterns and the power supply line is formed on the base. 
     A manufacturing method of a printed circuit board according to the present invention has a power supply line and a ground pattern and on which a surface-mounted multiple-resonance antenna having plural antenna conductor patterns is provided, wherein a land pattern which connects each of the antenna conductor patterns, the power supply line, and the ground pattern and includes a slit which controls the connection distance between at least a portion of each of the antenna conductor patterns and the power supply line is formed. 
     According to the present invention, the impedance matching between the resonance antennas of the surface-mounted multiple-resonance antenna of a direct power supply type can be realized by the simple configuration of the slit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view showing the configuration of an antenna device according to a first embodiment of the present invention, and  FIG. 1B  omits the description of other portions of a surface-mounted antenna so that conductors formed on the bottom surface of the surface-mounted antenna can be easily seen; 
         FIG. 2  is a developed view of the surface-mounted antenna according to the first embodiment of the present invention; 
         FIGS. 3A and 3B  are plan views showing the configuration of a substrate according to the first embodiment of the present invention, in which  FIG. 3A  is a plan view of the face side of the substrate (the surface on which the surface-mounted antenna is provided) and  FIG. 3B  is a plan view of the back side of the substrate; 
         FIGS. 4A ,  4 B,  4 C,  4 D,  4 E, and  4 F are explanatory views of the relation between the connection distance between each of antenna conductor patterns and a power supply line and the depth of a slit according to the first embodiment of the present invention; 
         FIGS. 5A ,  5 B, and  5 C are diagrams in which the impedance of each of the antenna conductor patterns for each of the examples shown in  FIGS. 4A ,  4 B,  4 C,  4 D,  4 E, and  4 F is measured and is shown on the Smith chart; 
         FIGS. 6A ,  6 B,  6 C,  6 D,  6 E, and  6 F are diagrams in which a return loss near the resonance frequency of each of the antenna conductor patterns of each of the examples shown in  FIGS. 4A ,  4 B,  4 C,  4 D,  4 E, and  4 F is measured and is plotted; 
         FIGS. 7A and 7B  are plan views showing the configuration of the substrate according to a second embodiment of the present invention, in which  FIG. 7A  is a plan view of the face side of the substrate (the surface on which the surface-mounted antenna is provided) and  FIG. 7B  is a plan view of the back side of the substrate; 
         FIG. 8  is a developed view of the surface-mounted antenna according to the second embodiment of the present invention; 
         FIG. 9  is a developed view of the surface-mounted antenna according to a third embodiment of the present invention; and 
         FIGS. 10A and 10B  are plan views showing the configuration of the substrate according to the third embodiment of the present invention, in which  FIG. 10A  is a plan view of the face side of the substrate (the surface on which the surface-mounted antenna is provided) and  FIG. 10B  is a plan view of the back side of the substrate. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 1A  is a perspective view showing the configuration of an antenna device  1  according to a first embodiment of the present invention. As shown in  FIG. 1A , the antenna device  1  has a surface-mounted antenna  10 , and a substrate  20  on which the surface-mounted antenna  10  is provided. The antenna device  1  is mounted on compact radio communication equipment such as a cellular phone.  FIG. 1B  omits the description of other portions of the surface-mounted antenna  10  so that conductors formed on the bottom surface of the surface-mounted antenna  10  can be easily seen.  FIG. 2  shows a developed view of the surface-mounted antenna  10 .  FIGS. 3A and 3B  show plan views showing the configuration of the substrate  20 .  FIG. 3A  is a plan view of the face side of the substrate  20  (the surface on which the surface-mounted antenna  10  is provided).  FIG. 3B  is a plan view of the back side of the substrate  20 . The configuration of the antenna device  1  will be described below in detail with reference to these drawings. 
     As shown in  FIGS. 1A ,  1 B, and  2 , the surface-mounted antenna  10  has a base  11  made of a dielectric having a substantially rectangular parallelepiped shape, antenna conductor patterns  13 A and  13 B and plane conductor patterns  14  to  16  configured by conductors on the surface of the base  11 . As shown in  FIG. 1A , the surface-mounted antenna  10  is provided near the corner portion of the substrate  20 . 
     The size of the base  11  may be appropriately set according to a target antenna characteristic. Without being limited, lateral lengths x 1  and x 2  (x 1 &gt;x 2 ) can be 14 mm and 3 mm, respectively, and a height x 3  can be 3 mm. Without being limited, as the materials of the base  11 , it is preferable to use dielectric materials such as a Ba—Nd—Ti material (specific inductive capacity of 80 to 120), an Nd—Al—Ca—Ti material (specific inductive capacity of 43 to 46), an Li—Al—Sr—Ti (specific inductive capacity of 38 to 41), a Ba—Ti material (specific inductive capacity of 34 to 36), a Ba—Mg—W material (specific inductive capacity of 20 to 22), an Mg—Ca—Ti material (specific inductive capacity of 19 to 21), sapphire (specific inductive capacity of 9 to 10), alumina ceramics (specific inductive capacity of 9 to 10), and cordierite ceramics (specific inductive capacity of 4 to 6). The base  11  is manufactured by calcining these materials using a die. 
     The dielectric materials to be specifically used may be appropriately selected according to the used frequencies of the later-described radio communication systems to use the antenna conductor patterns  13 A and  13 B. As specific inductive capacity ∈r is larger, a higher wavelength shortening effect can be obtained. Therefore, the length of the radiation conductor can be shortened. When the specific inductive capacity ∈r is too large, the antenna gain is reduced. It is preferable to determine the optimum dielectric material by observing the balance of these. By way of example, when the antenna conductor pattern  13 A is used for GPS reception and the antenna conductor pattern  13 B is used for wireless LAN communication of IEEE 802.11b, it is preferable to use the dielectric material having specific inductive capacity of about 5 to 40. As such dielectric material, the Mg—Ca—Ti dielectric ceramic can be preferably used. As the Mg—Ca—Ti dielectric ceramic, it is particularly preferable to use the Mg—Ca—Ti dielectric ceramic containing TiO 2 , MgO, CaO, MnO, and Sio 2 . 
     The term “substantially rectangular parallelepiped shape” is intended to include, not only a complete rectangular parallelepiped, but also a partially incomplete rectangular parallelepiped. In this embodiment, as shown in  FIGS. 1A and 2 , a groove which penetrates through the center of each of the surfaces at an equal width and a depth h from the lower side of a side surface  11 A through a top surface  11 C to the lower side of a side surface  11 F is cut in the base  11 . Thus, a convex surface  12 A having a constant width w 1  along the boundary between the top surface  110  and a side surface  11 D and a convex surface  12 B having a constant width w 2  along the boundary between the top surface  11 C and a side surface  11 B are formed. The base  11  does not have the complete rectangular parallelepiped shape. Such groove and convex portions are provided for preferably electrically separating the antenna conductor patterns  13 A and  13 B. 
     The antenna conductor pattern  13 A is a conductor pattern formed on the convex surface  12 A. The formed region of the antenna conductor pattern  13 A passes from the lower side of the side surface  11 A (of two side surfaces vertical to a longitudinal direction, the side surface near the corner portion of the substrate  20 ) of the base  11  through the top surface  11 C to the position at a distance L 1  from the upper side of the side surface  11 F (the side surface opposite the side surface  11 A), and has a continuous belt-shaped configuration having the constant width w 1 . The portion of the conductor pattern configuring the antenna conductor pattern  13 A provided on the side surface  11 A is a power supply electrode  13 A- 1  and the portion other than that is a radiation electrode  13 A- 2 . One end  13 Aa (the end on the power supply electrode  13 A- 1  side) of the antenna conductor pattern  13 A is connected to the plane conductor pattern  16  at the lower end of the side surface  11 A. The other end  13 Ab (the portion at the distance L 1  from the upper side of the side surface  11 F) of the antenna conductor pattern  13 A is not connected to other conductor patterns. 
     The antenna conductor pattern  13 B has a conductor pattern formed on the convex surface  12 B and a conductor pattern formed on the side surface  11 B. The former passes from the lower side of the side surface  11 A of the base  11  through the top surface  11 C to the position at the distance L 1  from the upper side of the side surface  11 F, and has a continuous belt-shaped configuration having the constant width w 2  in parallel with the antenna conductor pattern  13 A. The latter has a configuration extended from the conductor pattern of the side surface  11 F onto the side surface  11 B along a length L 2 . The portion of the conductor pattern configuring the antenna conductor pattern  13 B provided on the side surface  11 A is a power supply electrode  13 B- 1  and the portion other than that is a radiation electrode  13 B- 2 . One end  13 Ba (the end on the power supply electrode  13 B- 1  side) of the antenna conductor pattern  13 B is connected to the plane conductor pattern  16  at the lower end of the side surface  11 A. The other end  13 Bb (the portion at the distance L 2  from the boundary between the side surfaces  11 B and  11 F) of the antenna conductor pattern  13 B is not connected to other conductor patterns. 
     The plane conductor patterns  14  and  16  are conductor patterns having a substantially rectangular shape formed throughout the entire width of a bottom surface  11 E at the end on the side surface  11 F side and the end on the side surface  11 A side in a longitudinal direction of the bottom surface  11 E, respectively. The length in a longitudinal direction of the base  11  of the plane conductor pattern  16  is L 3 . The plane conductor pattern  14  is extended to the side surfaces  11 F and  11 B and is not connected to the antenna conductor patterns  13 A and  13 B. As described above, the plane conductor pattern  16  is connected to the power supply electrodes  13 A- 1  and  13 B- 2  provided on the side surface  11 A. 
     As shown in  FIGS. 1B and 2 , the plane conductor pattern  16  has a slit  16   a  having a width w and a depth d cut from the side surface  11 D side. This point will be described in detail later. 
     The plane conductor pattern  15  is a rectangular conductor pattern formed throughout the entire width of the bottom surface  11 E between the plane conductor patterns  14  and  16 . The plane conductor pattern  15  is extended to near the boundary between the side surface  11 B and the bottom surface  11 E. The plane conductor pattern  15  is not contacted with other conductor patterns on the surface of the base  11 . 
     Each of the conductor patterns can be formed by sintering under a predetermined temperature condition after applying a paste material for electrode to the base  11  by screen printing or transfer. As the paste material for electrode, silver, silver-palladium, silver-platinum, and copper can be used. The conductor pattern can also be formed by plating or sputtering. 
     The slit  16   a  may be manufactured by providing a shape corresponding to the slit  16   a  in a plate film used for screen printing or may be manufactured by cutting away the portion corresponding to the slit  16   a  after the plane conductor pattern  16  not having the slit is formed. 
     As shown in  FIGS. 1A ,  1 B,  3 A, and  3 B, the substrate  20  has, on its face side, a ground clearance region  21  not provided with a ground pattern, a ground pattern  22  provided around the ground clearance region  21 , land patterns  23  to  26  provided in the ground clearance region  21 , a power supply line  27  connected to the land pattern  25 , and a throughhole conductor  28  which guides the power supply line  27  to the back side of the substrate  20 , and has, on its back side, a ground pattern  30 . A region X indicated by the dashed line of the ground clearance region  21  is the provided region of the surface-mounted antenna  10 . Although not shown, other various electronic components for configuring radio communication equipment are mounted on the substrate  20 . 
     The ground clearance region  21  is provided along the corner portion of the substrate  20 . Two directions around the ground clearance region  21  are surrounded by the ground pattern  22 . Other two directions form an open space in which the substrate  20  does not exist. 
     The ground pattern  30  on the back side also exists immediately below the region X. Therefore, the surface-mounted antenna  10  is of the so-called on-ground type. 
     The land patterns  23  and  24  are provided in the positions corresponding to the plane conductor patterns  14  and  15  of the surface-mounted antenna  10 , respectively, and are solder connected to these conductors. The land pattern  23  is contacted with the ground pattern  22  at an end  23   a . A chip reactor  29   a  for frequency adjustment configured by an inductor, a capacitor, or a short circuit is mounted between the land pattern  24  and the ground pattern  22 . The chip reactor  29   a  is inserted in series between a lead portion  24   a  of the land pattern  24  and the ground pattern  22 . The mounted position of the chip reactor  29   a  is preferably the position outside the ground clearance region  21  and as closely as possible to the ground clearance region  21 . 
     The land patterns  25  and  26  are provided in the positions corresponding to the plane conductor pattern  16  of the surface-mounted antenna  10  and are solder connected to these conductors. The gap between the land patterns  25  and  26  is set to the constant width w. The position of the gap corresponds to the position of the slit  16   a . In other words, the substrate  20  does not have a conductor pattern in a region corresponding to the slit  16   a . The land pattern  26  is contacted with the ground pattern  22  at an end  26   a.    
     The power supply line  27  is connected to the land pattern  25 . A chip reactor  29   b  for impedance adjustment configured by an inductor, a capacitor, or a short circuit is mounted between the power supply line  27  and the ground pattern  22 . The mounted position of the chip reactor  29   b  is preferably the position outside the ground clearance region  21  and as closely as possible to the ground clearance region  21 . The power supply line  27  is introduced into the back side by the through hole conductor  28  and is connected to a signal line (not shown) on the back side. 
     Each of the ground patterns and each of the land patterns can be formed by preparing a substrate to which copper foil is stuck on the entire surface and dissolving the copper foil in the unnecessary portion by etching. 
     The surface-mounted antenna  10  and the substrate have the above configurations. Therefore, the antenna conductor patterns  13 A and  13 B function as an inverted-F antenna, respectively. That is, in the antenna conductor pattern  13 A, the land pattern  26  functions as the short stub of the inverted-F antenna, and the end  13 Ab functions as the open end of the inverted-F antenna. In the antenna conductor pattern  138 , the land pattern  26  functions as the short stub of the inverted-F antenna and the end  13 Bb functions as the open end of the inverted-F antenna. 
     The resonance frequencies of the antenna conductor patterns  13 A and  13 B are determined mainly by the length and width of the conductors formed on the surface of the base  11  and the specific inductive capacity of the base  11 . In the antenna device  1 , fine adjustment of the resonance frequencies is enabled by appropriately adjusting the reactance of the chip reactor  29   a.    
     The antenna conductor pattern  13 A relatively located inside the substrate  20  is preferably used for the radio communication system of a relatively high frequency. The antenna conductor pattern  13 B relatively located outside the substrate  20  is preferably used for the radio communication system of a relatively low frequency. By way of example, when they cope with GPS reception using a frequency in a 1.5 GHz bandwidth and IEEE 802.11b communication using a frequency in a 2.5 GHz bandwidth, it is preferable that the resonance frequency of the antenna conductor pattern  13 A be adjusted to the 2.5 GHz bandwidth and that the resonance frequency of the antenna conductor pattern  13 B be adjusted to the 1.5 GHz bandwidth. 
     The slit  16   a  provided in the plane conductor pattern  16  will be described. 
     By the above configurations, an electric current input from the power supply line  27  enters the plane conductor pattern  16  through the land pattern  25 , and reaches each of the power supply electrodes  13 A- 1  and  13 B- 1  beyond the slit  16   a . The slit  16   a  is provided between the power supply line  27  and each of the power supply electrodes  13 A- 1  and  13 A- 2 . By the depth d of the slit  16   a , the connection distance between the antenna conductor patterns  13 A and  13 B and the power supply line can be controlled. This will be specifically described below. 
       FIGS. 4A ,  4 B,  4 C,  4 D,  4 E, and  4 F are explanatory views of the relation between the connection distance between the antenna conductor patterns  13 A or  13 B and the power supply line  27  and the depth d of the slit  16   a . In  FIGS. 4A and 4B , d=d 2 , in  FIGS. 4C and 4D , d=d 1  (0&lt;d 1 &lt;d 2 ), and in  FIGS. 4E and 4F , d=0. The position of the end  26   a  is fixed. 
     As shown in  FIGS. 4B ,  4 D, and  4 F, as the depth d is larger, a path (power supply path) D A  of an electric current from the power supply line  27  to the power supply electrode  13 A is longer. This is because the electric current goes around the slit  16   a.    
     As shown in  FIGS. 4A ,  4 C, and  4 E, as the depth d is larger, a path D B  of an electric current from the power supply line  27  to the power supply electrode  13 B is also longer. The power supply electrode  13 B is substantially opposite the power supply line  27  across the depth direction of the slit  16   a , so the amount in change is smaller than that of the path D A . 
     Thus, when the position of the end  26   a  is fixed, the difference between the paths D B  and D A  can be controlled by changing the depth. This means that the difference in impedance between the antenna conductor patterns  13 A and  13 B can be controlled. When the depth d is adjusted to a suitable value in the manufacturing stage, the impedance matching between the resonance antennas can be simply realized. 
     The effect of the present invention will be described below by giving specific measured results. In the examples shown below, x 1 =14 mm, x 2 =3 mm, x 3 =3 mm, w 1 =1 mm, w 2 =1 mm, L 1 =2 mm, L 2 =10 mm, L 3 =2.5 mm, d 1 =1.5 mm, and d 2 =2.5 mm. The resonance frequency of the antenna conductor pattern  13 A is adjusted to the 2.5 GHz bandwidth. The resonance frequency of the antenna conductor pattern  13 B is adjusted to the 1.5 GHz bandwidth. 
       FIGS. 5A ,  5 B, and  5 C are diagrams in which the impedance of each of the antenna conductor patterns  13 A and  13 B for each of the examples of the depth d shown in  FIGS. 4A ,  4 B,  4 C,  4 D,  4 E, and  4 F is measured and is shown on the Smith chart.  FIGS. 5A ,  5 B, and  5 C correspond to d=d Z , d 1 , and 0, respectively. In the Smith chart, the center indicates a reference characteristic impedance (e.g., 50Ω), the right end indicates impedance infinity (open), and the left end indicates impedance 0 (short circuit). A positive reactance is taken clockwise of the upper half portion. A negative reactance is taken counterclockwise of the lower half portion. 
     When the frequency is increased from 0 Hz, the impedance of each of the antenna conductor patterns  13 A and  13 B is traced as shown in the Smith chart of  FIGS. 5A ,  5 B, and  5 C. As is apparent from  FIGS. 5A ,  5 B, and  5 C, the impedance characteristic of the antenna conductor pattern  13 B is hardly changed according to the depth d. However, the impedance characteristic of the antenna conductor pattern  13 A is largely changed according to the depth d. This shows that the impedance of the antenna conductor pattern  13 A is particularly controlled by the control of the depth d of the slit  16   a.    
     Of the three examples of the depth d shown in  FIGS. 5A ,  5 B, and  5 C, the example of d=d 1  shown in  FIG. 5B  shows that the difference in curvature of a curve showing the change in impedance between the antenna conductor patterns  13 A and  13 B is minimum. It means the impedance matching between the antenna conductor patterns  13 A and  13 B can be taken best when d=d 1 . Therefore, it is most preferable that the depth c of the slit  16   a  be d 1 , not 0 or d 2 . 
       FIGS. 6A ,  6 B,  6 C,  6 D,  6 E, and  6 F are diagrams in which a return loss near the resonance frequency of each of the antenna conductor patterns  13 A and  13 B of each of the examples of the depth d shown in  FIGS. 4A ,  4 B,  4 C,  4 D,  4 E, and  4 F is measured and is plotted.  FIGS. 6A ,  6 C, and  6 E show a return loss near the resonance frequency in the 1.5 GHz bandwidth of the antenna conductor pattern  13 B.  FIGS. 6B ,  6 D, and  6 F show a return loss near the resonance frequency in the 2.5 GHz bandwidth of the antenna conductor pattern  13 A.  FIGS. 6A and 6B  correspond to d=d 2 ,  FIGS. 6C and 6D  correspond to d=d 1 , and  FIGS. 6E and 6F  correspond to d=0. 
     As is apparent from  FIGS. 6A ,  6 B,  6 C,  6 D,  6 E, and  6 F, the return losses are changed according to the depth d of the slit  16   a  in both the 1.5 GHz bandwidth and the 2.5 GHz bandwidth. The magnitude of the change in the 2.5 GHz bandwidth is larger. That is, the difference in impedance between the antenna conductor patterns  13 A and  13 B is controlled by the control of the depth d of the slit  16   a.    
     Of the three examples of the depth d shown in  FIGS. 6A ,  6 B,  6 C,  6 D,  6 E, and  6 F, the examples of d=d 1  shown in  FIGS. 6C and 6D  show that the difference in the return loss is minimum. It means the impedance matching between the antenna conductor patterns  13 A and  13 B can be taken best when d=d 1 . As a result, it is most preferable that the depth d of the slit  16   a  be d 1 , not 0 or d 2 . 
     The specific value of the depth d is changed due to various factors of the material, shape, and size of the base  11 , the conductor patterns, and the substrate  20 , and other elements provided on the substrate  20  and is preferably determined by an experiment for each type of a product. 
     As described above, according to the antenna device  1  of this embodiment, the length of the power supply path to each of the antenna conductor patterns can be controlled by adjusting the depth d of the slit  16   a . Therefore, the impedance matching between the resonance antennas can be realized by the simple configuration of the slit  16   a.    
     Second Embodiment 
     The antenna device  1  according to this embodiment is the same as the first embodiment except for the position providing the slit. In the first embodiment, the slit is provided in the conductor pattern formed on the surface of the surface-mounted antenna  10 . In this embodiment, the slit is provided in the land pattern formed on the surface of the substrate  20 . Focusing on this difference, this embodiment will be described below in detail. 
       FIGS. 7A and 7B  are plan views showing the configuration of the substrate  20  according to this embodiment.  FIG. 8  is a developed view of the surface-mounted antenna  10  according to this embodiment. 
     As shown in  FIG. 7A , the substrate  20  according to this embodiment has a land pattern  31  in place of the land patterns  25  and  26  shown in  FIG. 3 . The land pattern  31  has a shape in which the gap portion between the land patterns  25  and  26  is filled with the conductor pattern and has a slit  31   a  having the width w and the depth d cut from the power supply line  27  side in the portion corresponding to the gap. 
     The slit  31   a  may be manufactured by providing a shape corresponding to the slit  31   a  in a mask used for etching copper foil stuck onto the substrate or may be manufactured by cutting away the portion corresponding to the slit  31   a  after the land pattern  31  not having the slit is formed. 
     As shown in  FIG. 8 , the surface-mounted antenna  10  according to this embodiment has a plane conductor pattern  17  in place of the plane conductor pattern  16 . The plane conductor pattern  17  is a substantially rectangular conductor pattern formed throughout the entire width of the bottom surface  11 E at the end on the side surface  11 A side in a longitudinal direction of the bottom surface  11 E, and has a shape in which only the portion on the side surface  11 A side from the slit  16   a  is cut out from the plane conductor pattern  16  shown in  FIG. 2 . The surface-mounted antenna  10  does not have the conductor pattern in the position corresponding to the slit  31   a.    
     By the above configuration, an electric current input from the power supply line  27  passes through the land pattern  31  beyond the slit  31   a  to the plane conductor pattern  17 . The slit  31   a  is provided between the power supply line  27  and each of the power supply electrodes  13 A- 1  and  13 A- 2 , as in the slit  16   a  according to the first embodiment. As in the first embodiment, the connection distance between the antenna conductor patterns  13 A and  13 B and the power supply line  27  is controlled according to the depth d of the slit  31   a.    
     As described above, according to the antenna device  1  of this embodiment, the length of the power supply path to each of the antenna conductor patterns can be controlled by adjusting the depth d of the slit  31   a . Therefore, the impedance matching between the resonance antennas can be realized by the simple configuration of the slit  31   a.    
     Also, since the slit is provided in the substrate  20  side, as compared with the case in which the slit is provided in the surface-mounted antenna  10 , the slit can be formed at high accuracy. 
     Third Embodiment 
     This embodiment is the same as the first embodiment except for the specific configuration of the plane conductor pattern  15 . Focusing on this difference, this embodiment will be described below in detail. 
       FIG. 9  is a developed view of the surface-mounted antenna  10  according to this embodiment.  FIGS. 10A and 10B  are plan views showing the configuration of the substrate  20  according to this embodiment. 
     As shown in  FIG. 9 , the surface-mounted antenna  10  according to this embodiment has plane conductor patterns  15 A and  15 B in the portion having the plane conductor pattern  15  in the first embodiment (the bottom surface  11 E of the base  11 ). The plane conductor pattern  15 A has the same width as that of the antenna conductor pattern  13 A, and is provided in the position opposite the portion provided on the top surface  11 C of the antenna conductor pattern  13 A (top surface conductor pattern). The plane conductor pattern  15 B has the same width as that of the antenna conductor pattern  13 B, and is provided in the position opposite the portion provided on the top surface  11 C of the antenna conductor pattern  13 B (top surface conductor pattern). 
     As shown in  FIG. 10A , the substrate  20  has land patterns  24 A and  24 B in place of the land pattern  24 . Of these, the land pattern  24 A is provided in the position corresponding to the plane conductor pattern  15 A of the surface-mounted antenna  10  and is solder connected to the plane conductor pattern  15 A. The land pattern  248  is provided in the position corresponding to the plane conductor pattern  15 B of the surface-mounted antenna  10  and is solder connected to the plane conductor pattern  15 B. 
     A chip reactor  29   a  for frequency adjustment is mounted between the land pattern  24 A and the ground pattern  22 . The chip reactor  29   a  is inserted in series between a lead portion  24 Aa of the land pattern  24 A and the ground pattern  22 . Similarly, a chip reactor  29   c  for frequency adjustment is mounted between the land pattern  24 B and the ground pattern  22 . The chip reactor  29   c  is inserted in series between a lead portion  24 Ba of the land pattern  24 B and the ground pattern  22 . 
     By the above configuration, the characteristic of the antenna conductor pattern  13 A and the characteristic of the antenna conductor pattern  13 B can be easily controlled independently. Therefore, the impedance matching between the resonance antennas can be realized more easily. 
     By way of example, in  FIG. 10A , the land patterns  24 A and  24 B are connected to the ground pattern  22  via the chip reactors for adjusting different frequencies (the chip reactors  29   a  and  29   c ). The frequency can be adjusted for each of the antenna conductor patterns. 
     The preferred embodiments of the present invention have been described above. The present invention is not limited to such embodiments at all. Needless to say, the present invention can be embodied in various forms in the scope without departing from its purport.