Abstract:
The present invention provides a surface-mounting type antenna comprising: a base member made of an insulating material, including a first major surface, a second major surface opposite to the first major surface, and a plurality of side surfaces extending between the first and second major surfaces; a grounding electrode covering substantially the entire area of the first major surface of the base member; a strip-like radiation electrode mostly disposed on the second major surface, the radiation electrode having a first end and a second end, the first end being served as an open-ended terminal; a connecting terminal connected to the second end of the radiation electrode; a power-supply electrode disposed in the vicinity of the open-ended terminal of the radiation electrode; and a power-supply terminal connected to the power-supply electrode.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a surface-mounting type antenna, an antenna device, and a communication device including the antenna device. More particularly, the present invention relates to a surface-mounting type antenna, an antenna device, and a communication device including the antenna device which are to be used for mobile communication, etc. 
     2. Description of the Related Art 
     While the reduction in size and weight of mobile communication devices, particularly portable telephones in recent years is in progress, as for the antennas mounted on them the further reduction in size and weight, and increase in gain have been required. 
     In FIGS. 9 and 10, a conventional surface-mounting type antenna and an antenna device including the antenna device are shown respectively. The structure of the surface-mounting type antenna  30  in FIG. 9 is shown in Japanese Unexamined Patent Publication No. 10-13139. 
     In FIG. 9, the surface-mounting type antenna  10  is composed of some electrodes disposed on the surface of a base member  11  in the form of a rectangular solid made of a dielectric substance such as ceramics, resin, etc. as one insulating material. First, on the nearly whole surface of a first major surface  11   a  of the base member  11  the grounding electrode  12  is disposed. Further, on a second major surface  11   b  of the base member  11  a strip-like radiation electrode  13  is disposed along the long side of the base member  11 . At a first end of the radiation electrode  13  an open-ended terminal  13   a  is provided, and ta second end is connected to a grounding electrode through a connecting electrode  14  disposed on an side surface  11   c  of the base member  11 . Further, on the second major surface  11   b  of the base member  11  a power-supply electrode  15  located close to the open-ended terminal  13   a  of the radiation electrode  13  is disposed, and the power-supply electrode  15  is connected to a power-supply terminal  16  disposed over an side surface  11   d  to the first major surface  11   a  of the base member  11 . 
     Here, when the surface-mounting type antenna  10  is mounted on a circuit board (not illustrated) because a power-supply terminal  16  is connected to a power-supply line on the side of the circuit board by soldering, etc., it is called the terminal in order to distinguish that from other electrodes. Hereinafter, when an electrode is described as a terminal, the electrode for connection to a circuit board is meant. However, there are cases in which electrodes and terminals are integrated, and then a part of the electrodes may be used as a terminal. 
     Next, in the antenna device  1  shown in FIG. 10, the surface-mounting type antenna  10  is mounted on the circuit-board grounding electrode  3  in the vicinity of a corner portion of the circuit board  2 . The grounding electrode  12  and power-supply terminal  16  of the surface-mounting type antenna  10  are connected to the circuit-board grounding electrode  3  and power-supply line  4  disposed on the circuit board  2  by soldering, etc. respectively. 
     Here, in FIG. 11, an equivalent circuit of the antenna device  1  in FIG. 10 is shown. In FIG. 11, a capacitor CO represents capacitance produced between the power-supply electrode  15  and the grounding electrode  12  and circuit-board grounding electrode  3 , a capacitor C 1  capacitance between the power-supply electrode  15  and the open-ended terminal  13   a  of the radiation electrode  13 , a capacitor C 2  capacitance between the radiation electrode  13  and the grounding electrode  12  and circuit-board grounding electrode  3 , conductance G a radiation resistor of the surface-mounting type antenna  10 , and an inductance L 1  and resistor R 1  an inductance component and resistance component of the radiation electrode  13  respectively. Further, mark S represents a signal source. The inductance L and resistor R 1  are connected in series, and one end of such is connected to the signal source S through the capacitor C 1  and the other end is grounded. The connecting portion between the inductance L 1  and capacitor C 1  is grounded through the capacitor C 2  and through the conductance G respectively. More, the connecting portion between the capacitor C 1  and signal source S is grounded through the capacitor C 0 . And the resonance frequency of the antenna device  1  is determined mainly by the inductance L 1  and capacitor C 2 . 
     Further, in FIGS. 12 and 13, another conventional surface-mounting type antenna and antenna device including the antenna device are shown. In FIG. 13, to the same or equivalent portions as in FIG. 10, the same reference numerals are given and their explanation is omitted. The structure of the surface-mounting type antenna  20  in FIG. 12 is shown in Japanese Unexamined Patent Publication No. 10-13139. 
     In FIG. 12, the surface-mounting type antenna  30  is composed of some electrodes disposed on the surface of a base member  31  in the form of a rectangular solid made up of a dielectric substance such as ceramics, resin, etc. as one insulating material. First of all, a strip-like radiation electrode  32  is disposed along the long side of the side surface  31   c  and over the second major surface  31   b  of the base member  31 . A first end of the radiation electrode  32  is served as an open-ended terminal on the second major surface  31   b  of the base member  31 , and a second end is connected to the grounding terminal  33  disposed on the first major surface  31   a  of the base member  31 . Further, a power-supply electrode  34  is disposed on the second major surface  31   b  of the base member  31 , and the power-supply electrode  34  is connected to a power-supply terminal  35  disposed over the side surface  31   d  to the first major surface  31   a  of the base member  31 . In the same way, on the second major surface  31   b  of the base member  31 , a grounding electrode  36  is disposed in the vicinity of the open-ended terminal  32   a  of the radiation electrode  32 , and the grounding electrode  36  is connected to a grounding terminal  37  disposed over the side surface  31   d  to the first major surface  31   a  of the base member  31 . 
     Next, in an antenna device  20  shown in FIG. 13, the surface-mounting type antenna  30  is mounted in an area  2   a  having no electrode disposed in the vicinity of a corner portion of the circuit board  2 . The grounding terminals  33  and  37  and power-supply terminal  35  of the surface-mounting type antenna  30  are connected to the circuit-board grounding electrode  3  and power-supply line  4  respectively by soldering, etc. 
     Further, in an equivalent circuit of the antenna device  20 , the capacitor C 2  mainly represents a capacitance produced between the open-ended terminal  32   a  and the grounding electrode  36 , grounding terminal  37 , and circuit-board grounding electrodes of the radiation electrode  32 , and the equivalent circuit is basically the same as in FIG.  11 . Accordingly, here the explanation is omitted. 
     In order to realize the reduction in size of a communication device equipped with a surface-mounting type antenna, it is necessary to reduce the space occupied by the antenna device on the circuit board, and as a method for the reduction, the reduction in size of the surface-mounting type antenna itself is one choice to be considered. 
     In the surface-mounting type antennas shown in FIGS. 9 and 12, if the base member is simply made small, the length of the radiation electrode is reduced and as a result the inductance L 1  of the radiation electrode is also reduced. Because of this, in order to realize the same inductance L 1  on the equivalent circuit as before, it is necessary to make the radiation electrode thin or have the radiation electrode formed in a meandering way. However, in that case, there is a problem that the resistance component R 1  of the radiation electrode is increased and the antenna gain is reduced. To the contrary, it may be considered that the increase of capacitance C 2  compensates for the reduction of inductance L 1  in order to keep the same resonance frequency, but for that purpose it is necessary to increase the dielectric constant of the base member and make the space between the open-ended terminal of the radiation electrode and the grounding electrode narrow and then there is a problem that because the radiation resistance G is increased, the antenna gain is reduced and the bandwidth is narrowed. As a result, in the communication device equipped with such an antenna device there occurs a problem that the antenna gain is lowered and the bandwidth is made narrow. 
     SUMMARY OF THE INVENTION 
     Then, the present invention is to present a surface-mounting type antenna, an antenna device, and a communication device which make it possible to reduce the occupied space by the surface-mounting type antenna on the circuit board. 
     To overcome the above described problems, the present invention provides a surface-mounting type antenna comprising: a base member made of an insulating material, including a first major surface, a second major surface opposite to the first major surface, and a plurality of side surfaces extending between the first and second major surfaces; a grounding electrode covering substantially the entire area of the first major surface of the base member; a strip-like radiation electrode mostly disposed on the second major surface, the radiation electrode having a first end and a second end, the first end being served as an open-ended terminal; a connecting terminal connected to the second end of the radiation electrode; a power-supply electrode disposed in the vicinity of the open-ended terminal of the radiation electrode; and a power-supply terminal connected to the power-supply electrode. 
     The present invention further provides an antenna device comprising: a circuit board on which a circuit-board grounding electrode is disposed; the above described surface-mounting type antenna mounted on the circuit board; and the connecting terminal of the surface-mounting type antenna being connected to the circuit-board grounding electrode through an inductance circuit provided on the circuit board. 
     The present invention further provides an antenna device comprising; a circuit board on which a circuit-board grounding electrode is disposed; a surface-mounting type antenna comprising: a base member made of an insulating material, including a first major surface, a second major surface opposite to the first major surface, and a plurality of side surfaces extending between the first and second major surfaces; strip-like radiation electrode disposed on the surface of the base member, the radiation electrode having a first end and a second end, the first end being served as an open-ended terminal; a connecting terminal connected to the second end of the radiation electrode; a power-supply electrode disposed on the surface of the base member; and a power-supply terminal connected to the power-supply electrode; the surface-mounting type antenna being mounted on the circuit board, the connecting terminal of the surface-mounting type antenna being connected to the circuit-board grounding electrode through an inductance circuit provided on the circuit board. 
     In the above described antenna device, the surface-mounting type antenna may be mounted in the vicinity of the corner portion of the circuit board in such a way that; a portion of the base member at which the connecting terminal is disposed directs the corner portion of the circuit board, a portion of the base member at which the open-ended terminal of the radiation electrode is disposed separates from the corner portion on the side edge of the circuit board, and the inductance circuit is disposed in the vicinity of the corner of the circuit board. 
     In the above described antenna device, the inductance circuit may comprise a linear pattern disposed on the circuit board. 
     In the above described antenna device, the inductance circuit may comprise a chip-inductor. 
     In the above described antenna device, the inductance circuit may comprises a variable inductance circuit including diodes. 
     The present invention further provides a communication device comprising the above described antenna device. 
     According to a surface-mounting type antenna and an antenna device of the present invention, the space occupied by the surface-mounting type antenna on the circuit board is able to be reduced, and at the same time the bandwidth and gain are able to be improved. 
     Further, in a communication device of the present invention, lower costs are able to be attained. 
     Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a perspective view showing a preferred embodiment of a surface-mounting type antenna of the present invention. 
     FIG. 2 is a perspective view showing a preferred embodiment of an antenna device of the present invention. 
     FIG. 3 shows an equivalent circuit of the antenna device in FIG.  2 . 
     FIG. 4 is a perspective view showing another preferred embodiment of an antenna device of the present invention. 
     FIG. 5 is a perspective view showing further another preferred embodiment of an antenna device of the present invention. 
     FIG. 6 is a perspective view showing further another preferred embodiment of an antenna device of the present invention. 
     FIG. 7 shows an equivalent circuit of the antenna device in FIG.  6 . 
     FIG. 8 is a perspective view showing a preferred embodiment of a communication device of the present invention. 
     FIG. 9 is a perspective view showing a conventional antenna device. 
     FIG. 10 is a perspective view showing a surface-mounting type antenna included in the antenna device in FIG.  9 . 
     FIG. 11 shows an equivalent circuit of the antenna device in FIG.  10 . 
     FIG. 12 is a perspective view showing another conventional antenna device. 
     FIG. 13 is a perspective view showing a surface-mounting type antenna included in the antenna device in FIG.  12 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1, one embodiment of a surface-mounting type antenna of the present invention is shown. In FIG. 1, the surface-mounting type antenna  40  is composed of some electrodes disposed on the surface of a base member  41  in the form of a rectangular solid made up of a dielectric substance such as ceramics, resin, etc. as one insulating material. First of all, on the substantially whole surface of a first major surface  41   a  of the base member  41  a grounding electrode  42  is disposed. Further, on a second major surface  41  b of the base member  41  a strip-like radiation electrode  43  is disposed along the long side of the base member  41 . At a first end of the radiation electrode  43  an open-ended terminal  43   a  is disposed, and a second end is connected to a connecting terminal  44  disposed over an side surface  41   c  of the base member  41  to the first major surface  41   a . More, the connecting terminal  44  and the grounding electrode  42  are insulated from each other. Further, on the second major surface  41  b of the base member  41  a power-supply electrode  45  located in the vicinity of the open-ended terminal  43   a  of the radiation electrode  43  is disposed, and the power-supply electrode  45  is connected to a power-supply terminal  46  disposed over the side surface  41   d  to the first major surface  41   a  of the base member  41 . 
     Next, in FIG. 2, an antenna device of the present invention is shown. In FIG. 2, to the same or equivalent portions as in FIGS. 1 and 10 the same reference numerals are given and their explanation is omitted. 
     In the antenna device  50  shown in FIG. 2, the surface-mounting type antenna  40  is mostly mounted on the circuit-board grounding electrode  3  in the vicinity of a corner portion of the circuit board  2 . The surface-mounting type antenna  40  is arranged so as to direct the portion having the connecting terminal  44  formed, of the base member  41  toward the comer portion of the circuit board  2  and to direct the portion having an open-ended terminal  43   a , of the radiation electrode  43  in the direction of being separated from the corner portion on the side edge of the circuit board  2 . The grounding electrode  42  and power-supply terminal  46  of the surface-mounting type antenna  40  are connected to the circuit-board grounding electrode  3  and power-supply line  4  disposed on the circuit board  2  respectively. And the connecting terminal  44  of the surface-mounting type antenna  40  is connected by soldering, etc. to an external connecting electrode  51  formed in an area  2   a  having no circuit-board grounding electrode disposed on the circuit board  2 , and the external connecting electrode  51  is connected to the circuit-board grounding electrode  3  through a linear pattern  52  as an inductance circuit. 
     Here, in FIG. 3, an equivalent circuit of the antenna device  50  in FIG. 2 is shown. In FIG. 3, to the same or equivalent portions as in FIG. 11 the same reference numerals are given and their explanation is omitted. 
     In FIG. 3, the inductance L 2  and resistance R 2  represent an inductance component and resistance component of the linear pattern  52  disposed on the circuit board  2 . Further, one end of a resistor R 1  is not directly grounded, and is grounded through the inductance L 2  and resistance R 2  in succession. And the resonance frequency of the antenna device  50  is determined mainly by the inductance L 1  and L 2 , and capacitance C 2 . 
     In this way, in the antenna device  50  of the present invention, because the second end of the radiation electrode  43  of the surface-mounting type antenna  40  is grounded through the connecting terminal  44  and linear pattern  52 , the real inductance component of the antenna as a whole is increased and the resonance frequency is reduced. In the converse way, this means that if the frequency as a target is the same, the inductance L 1  of the radiation electrode  43  is able to be reduced as much as the increase of inductance L 2  by the linear pattern  52 . And the fact that the inductance L 1  of the radiation electrode  43  is able to be reduced leads to the possibility of a shorter radiation electrode  43 , that is, a smaller-sized surface-mounting type antenna  40  by making the base member  41  shorter. 
     In this way, in the antenna device  50  of the present invention, by shortening the length of the surface-mounting type antenna  40  to be mounted, a linear pattern  52  is able to be formed in the area occupied by the shortened portion on the circuit board  2 . As the linear pattern  52  has little height in comparison with the surface-mounting type antenna  40 , the occupied volume by an antenna device including the surface-mounting type antenna  40  and linear pattern  52  is able to be made smaller than in the case of the conventional surface-mounting type antenna  10  mounted on the circuit board  2 . 
     Further, because the portion in which the linear pattern  52  is formed corresponds to a corner portion on the circuit board  2 , no parts are mounted at the corner portion. Because of this, the thickness of the circuit board  2  including the mounted parts is made thin at the comer portion. Then, there is a merit of the increased freedom of designing in such a way that a cover of the circuit board  2  is able to be made matched to the circuit board  2  by rounding a part of the cover corresponding to the corner portion of the circuit board  2 . 
     Further, according to an antenna device  50  of the present invention, the bandwidth as an antenna is able to be widened, and the gain is also able to be increased. 
     According to the experiment conducted by the inventors of the application concerned, in the case of the conventional antenna device, if the dimension of a surface-mounting type antenna is 15 mm×3 mm×1.8 mm, the occupied space becomes 81 cubic millimeters. On the other hand, in the case of the antenna device of the present invention, if the dimension of a surface-mounting type antenna is 12 mm×3 mm×1.8 mm, the occupied space was able to be made 64.8 cubic millimeters. As a result, according to an antenna device of the present invention, the occupied space of the antenna device as a whole was able to be reduced to about 80%. 
     Further, in the conventional antenna device, the bandwidth of the antenna was 24.0 MHz, and the maximum antenna gain was −2.7 dBd and the average gain −4.6 dBd. However, in the antenna device of the present invention, the bandwidth of the antenna was expanded to 24.1 MHz, and the maximum antenna gain became −2.1 dBd and the average gain −3.8 dBd, which means an extensive improvement. 
     Further, according to the antenna device  50  of the present invention, because the inductance L 2  of the linear pattern  52  formed on the circuit board  2  is able to be designed independently of the surface-mounting type antenna  40 , after the surface-mounting type antenna  40  has been designed so as to give the best capacitance C 2  and conductance G, it is possible to independently determine the inductance L 2  for deciding the resonance frequency by designing the length and shape of the linear pattern  52 . Thus, it is possible to extend the freedom of designing antenna devices. 
     Further, the antenna device  50  of the present invention is disposed in the vicinity of a corner portion of the circuit board so as to direct the portion having a connecting terminal formed, of the base member toward a corner portion of the circuit board and to direct the portion having an open-ended terminal of the radiation electrode formed in the direction of being separated from a comer portion on the side edge, of the circuit board. By arranging the surface-mounting type antenna  40  on the circuit board  2  in this way, the gain is able to be further increased. 
     According to the experiment by the inventors of the application concerned, when the direction of the surface-mounting type antenna is reversed, the maximum antenna gain becomes −9.6 dBd and this is greatly deteriorated in comparison with the former gain of −2.1 dBd. Thus, by the surface-mounting type antenna arranged so as to direct the portion having a connecting terminal formed, of the base member toward a corner portion of the circuit board and to direct the portion having an open-ended terminal of the radiation electrode formed in the direction of being separated from a corner portion on the side edge, of the circuit board, the improvement of the antenna gain was able to be confirmed. 
     In FIG. 4, another embodiment of an antenna device of the present invention is shown. In FIG. 4, to the same or equivalent portions as in FIGS. 2,  12 , and  13  the same reference numerals are given and their explanation is omitted. 
     In the antenna device  60  shown in FIG. 4, the grounding terminal  33  of the surface-mounting type antenna  30  is not directly connected to the circuit-board grounding electrode  3  of the circuit board  2 , but connected by soldering, etc. to an external connecting electrode  51  formed in the area  2   a  not having the circuit-board grounding electrode  3  formed on the circuit board  2 , and the external connecting electrode  51  is connected to the circuit-board grounding electrode  3  through the linear pattern  52  as an inductance circuit. That is, the grounding terminal  33  of the surface-mounting type antenna  30  is used with the same purpose as the connecting terminal  44  of the surface-mounting type antenna  40  in the antenna device  50 . Therefore, hereinafter, the grounding terminal  33  is called the connecting terminal  33 . 
     More, the equivalent circuit of the antenna device  60  is basically the same as in FIG. 3, and the explanation is omitted here. 
     In the antenna device  60  constructed in this way, in proportion to the inductance L 2  by the linear pattern  52  increased, the length of the base member  31  is able to be reduced to shorten the length of the radiation electrode  32  as in the antenna device  50 . Accordingly, it is possible to make the surface-mounting type antenna  30  smaller-sized and to reduce the occupied space of the surface-mounting type antenna. Further, it is possible to increase the bandwidth of the antenna and the antenna gain. 
     Further, because the inductance L 2  of the linear pattern  52  formed on the circuit board  2  is able to be designed independently of the surface-mounting type antenna  30 , after the side of the surface-mounting type antenna  30  has been designed to have the most appropriate capacitance C 2  and conductance G, the inductance L 2  for deciding the resonance frequency is able to be independently designed by changing the length and shape of the linear pattern  52 , and accordingly the freedom for mounting the surface-mounting type antenna is able to be increased. Furthermore, it is possible to increase the antenna gain more by the surface-mounting type antenna  30  arranged so as to direct the portion having the connecting terminal  33  formed, of the base member  31  toward a corner portion of the circuit board and to direct the portion having an open-ended terminal  32   a  formed, of the radiation electrode  32  in the direction of being separated from a corner portion on the side edge of the circuit board  2 . 
     In FIG. 5, further another preferred embodiment of an antenna device of the present invention is shown. In FIG. 5, to the same or equivalent portions as in FIG. 4 the same reference numerals are given and their explanation is omitted. 
     In the antenna device  70  shown in FIG. 5, the external connecting electrode  51  disposed in an area  2   a  having no circuit-board grounding electrode disposed on the circuit board  2  is connected to the circuit-board grounding electrode  3  through an inductance circuit  73  made up of a relatively short connecting wiring  71  having less inductance and a chip-inductor  72 . That is, instead of the linear pattern  52  in the antenna device  60 , the inductance circuit  73  composed of a connecting wiring  71  and a chip-inductor  72  is given. 
     Even if the inductance circuit is composed of a connecting wiring  71  and a chip-inductor  72  in this way, the antenna device  70  is quite the same as the antenna device  60  from the viewpoint of equivalent circuit and shows the same working-effect as the surface-mounting type antenna  60 , except that the occupied space by the antenna is slightly increased in accordance with the height of the chip-inductor. 
     In FIG. 6, further another preferred embodiment of an antenna device of the present invention is shown. In FIG. 6, to the same or equivalent portions as in FIG. 4 the same reference numerals are given and their explanation is omitted. 
     In the antenna device  80  shown in FIG. 6, one end of the linear pattern  52  is connected to an external connecting electrode  51 , and the other end of the linear pattern  52  is connected to a switching electrode  88  through the variable inductance circuit  86  composed of a diode  81 , a chip-inductor  82 , a chip-capacitor  83 , a chip-resistro 84 , and a chip-capacitor  85 . 
     Here, in the variable inductance circuit  86 , the other end of the linear pattern  52  is connected to the circuit-board grounding electrode  3  through a diode  81 . Further, the other end of the linear pattern  52  is connected to the switching electrode  88  through a chip-inductor  82  and a chip-resistor  84 . And both ends of the chip-resistor  84  are connected to the circuit-board grounding electrode  3  through a chip-capacitor  83  and a chip-capacitor  85  respectively. 
     Here, in FIG. 7, an equivalent circuit of the antenna device  80  is shown. In FIG. 7, to the same or equivalent portions as in FIG. 3 the same reference numerals are given and their explanation is omitted. 
     In FIG. 7, a diode D represents the diode  81 , inductance L 3  the inductance component of the chip-inductor  82 , capacitance C 3  the capacitance component of the chip-capacitor  83 , resistance R 3  the resistance component of the chip-resistor  84 , and capacitance C 4  the capacitance component of the chip-capacitor  85  respectively. One end of resistance R 2  is grounded through the diode D, and connected to the switching electrode  88  through the inductance L 3  and resistance R 3 . And both ends of resistance R 3  are grounded through capacitance C 3  and capacitance C 4  respectively. 
     Here, the resistance R 3  limits the direct current flowing through the diode D. Further, the capacitance C 3  functions so as to lower the impedance at the resonance frequency of the antenna device  80  and to ground the connecting portion between the inductance L 3  and resistance R 3  at high frequencies. Further, the capacitance C 4  functions as a bypass capacitor. And the resonance frequency of the antenna device  80  is determined mainly by the inductance L 1 , L 2 , and L 3 , and capacitance C 2 . 
     In the antenna device  80  thus constructed, when no voltage or any negative voltage is applied to the switching electrode  88 , the diode D is turned into nonconductive state. Because of this, the resonance frequency of the antenna device  80  is determined mainly by the inductance L 1 , L 2 , and L 3 , and the capacitance C 2 . On the other hand, when a positive voltage over a certain level is applied to the switching electrode  88 , the diode D is biased in the forward direction and turned into a conductive state, that is, the state of the connecting portion between the resistance R 2  and inductance L 3  being grounded. Because of this, the resonance frequency of the antenna device  80  comes to be determined mainly by the inductance L 1  and L 2  and the capacitance C 2 , and becomes higher than at the time when the diode D is in nonconductive state. Because of this fact, it is understood that the resonance frequency of the antenna device  80  is able to be changed by the voltage applied to the switching electrode  88 . 
     Therefore, in the antenna device  80  of the present invention, in addition to the working-effect of each of the above-described antenna devices the resonance frequency is able to be easily changed. 
     More, the variable inductance circuit is not limited to this construction. When the value of inductance is able to be changed by allowing a diode to function as a high-frequency switch, any construction is acceptable. 
     Further, in each of the above-described preferred embodiments, the radiation electrode of the surface-mounting type antenna was formed in a linear shape or in the shape of letter L, but others in the shape of letter U, in a meandering shape, etc. are acceptable. Further, it was stated that the base member of the surface-mounting type antenna is made up of a dielectric substance such as ceramics, resin, etc., but a magnetic substance is also able to be used. 
     In FIG. 8, one preferred embodiment of a communication device including an antenna device of the present invention is shown. In FIG. 8, the communication device  90  is composed of a circuit board  92  given in an enclosure  91 , and a circuit-board grounding electrode  93 , a power-supply line  94 , and a linear pattern  95  are disposed on the circuit board  92 . In a corner portion of the circuit board  92 , there is an area in which the circuit-board grounding electrode  93  is not formed and in this area a surface-mounting type antenna  30  is mounted. The antenna device is composed of the surface-mounting type antenna  30  the grounding terminal (not illustrated) of which is connected to the circuit-board grounding electrode  93  through the linear pattern  95  on the circuit board  92  and of the power-supply terminal (not illustrated) which is connected to the power-supply line  94  on the circuit board  92 . Furthermore, the power-supply line  94  is connected to a transmission circuit  97  and reception circuit  98  formed on the circuit board  92  through a switching circuit  96  formed on the same circuit board  92 . 
     In this way, by using an antenna device of the present invention, the freedom of mounting each of the parts in the communication device  90  is increased, and the bandwidth and antenna gain of the communication device  90  is able to be increased. 
     More, in the preferred embodiment of FIG. 8, the communication device  90  is composed of an antenna device  60 , but the use of antenna devices  50 ,  70 ,  80  also gives the same working-effect. 
     According to a surface-mounting type antenna and an antenna device of the present invention, by grounding the other end of the radiation electrode composed of a surface-mounting type antenna having one end as an open-ended terminal through an inductance circuit made up of a linear pattern, a chip-inductor, etc. provided on a circuit board, the surface-mounting type antenna is made small-sized and the occupied space by the antenna is able to be reduced. Further, it is possible to widen the bandwidth and improve the antenna gain. Further, because the radiation resistance is able to be designed on the side of the surface-mounting type antenna and the resonance frequency on the side of the circuit board independently, the freedom of designing the antenna device is able to be increased. Further, by arrangement in the vicinity of the corner portion of the circuit board so as to direct the portion having a connecting terminal formed, of the base member toward a corner portion of the circuit board and to direct the portion having an open-ended terminal, of the radiation electrode in the direction of being separated from the comer portion on the side edge of the circuit board, the antenna gain is able to be further increased. Further, by construction of an inductance circuit using a variable inductance circuit having diodes, the resonance frequency of the antenna is able to be changed. 
     Further, according to a communication device of the present invention, by using the above-mentioned antenna device, the freedom of mounting each of the parts inside the communication device is increased, and the bandwidth and antenna gain are able to be increased. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the forgoing and other changes in form and details may be made therein without departing from the spirit of the invention.