Abstract:
The present invention aims to provide a diversity wireless device that can be downsized without reduction in diversity gains. Provision of at least one ungrounded antenna among a plurality of antennas in the device makes a lower correlation between the antennas, thus giving a high diversity gain.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a diversity wireless device used for wireless communications, and more particularly to a diversity wireless device suitable for use in a wireless terminal unit for a wireless local area network (LAN), such as a wireless PC card.  
         BACKGROUND OF THE INVENTION  
         [0002]    The antenna diversity used for wireless communications and the like is an effective means of eliminating influence of fading from received signals.  
           [0003]    Generally, “fading” is a phenomenon in which variation of medium on a radio wave propagation path or the movement of mobile communication equipment through areas with different field intensities changes the strength of received signals rapidly. In addition, “diversity” means ensuring highly-reliable communications by preparing a plurality of antennas and synthesizing or switching two or more signals received at a reception side in a suitable manner when fading deteriorates the receiving condition.  
           [0004]    General methods of providing diversity used for wireless communications and the like are as follows. That is, signals are separately received by two or more receiving systems that have a low degree of correlation therebetween and the received signals are synthesized or automatically switched before or after demodulation and then used. Typical examples of such methods include space diversity and polarization diversity.  
           [0005]    The space diversity utilizes the fact that the variations caused by the fading at points separated from each other in the vicinity of a receiving point are independent of each other. Generally, two or more antennas are arranged so as to be spatially separated from each other and receive signals separately. Then, the signals are used after being synthesized or switched. The polarization diversity is a method of separately receiving signals using polarized wave receiving antennas that are arranged 90° different from each other. Either method can provide the greater diversity gain when the antennas have the lower degree of correlation therebetween.  
           [0006]    [0006]FIG. 15 shows a structure of a conventional diversity wireless device (for example, disclosed in Japanese Patent Application Non-Examined Publication No. H07-131229).  
           [0007]    In FIG. 15, substrate  3910  has antennas  3930  and  3940  mounted thereon. Formed on substrate  3910  is ground plane  3920 . Antenna  3930  has feed terminal  3931  and ground terminal  3932  that also serves to support the antenna. Similarly, antenna  3940  has feed terminal  3941  and ground terminal  3942  that also serves to support the antenna. In addition, mounted on substrate  3910  is radio frequency (RF) circuit  3950 . RF circuit  3950  performs such operations as switching transmission/reception antennas, feeding power into the antennas, and processing received signals. The ground of RF circuit  3950  connects to ground plane  3920 . In this structure, antennas  3930  and  3940  are so-called inverted F-type antennas, in which ground plane  3920  also affects the antenna characteristics.  
           [0008]    In recent years, there has been a strong request for downsizing of wireless devices. The downsizing have necessitated the smaller space assigned to antennas. Therefore, only insufficient space can be provided between antennas. This makes a higher degree of correlation between the antennas connected to a common ground, thus resulting in reduction in the diversity gains.  
           [0009]    In addition, in recent years, with the progress of networking in offices and at home, a plurality of personal computers (hereinafter referred to as PC) is connected via Internet or other networks and LANs are built. On the other hand, networking using wireless devices has been drawing attention because it does not have the problems of troublesome rewiring at a layout change and difficulty in new wiring. Especially, because the Institute of Electrical and Electronics Engineers (IEEE) standardized a transmission speed of 11 Mbps equivalent to that attained with wire devices, the introduction of wireless LANs has been promoted at a cheaper price than ever. An adapter for a wireless LAN is available as a wireless PC card, in which the space its wireless part can occupy is limited. Therefore, the wireless part including its antenna part is structured to have its own features.  
           [0010]    Known conventional wireless PC cards include the invention disclosed in Japanese Patent Publication No. 3004533 and the utility model disclosed in Japanese Utility Model Publication No. 3041690, both of which are built with inverted F-type antennas.  
           [0011]    [0011]FIG. 14A is a perspective view illustrating an appearance of a wireless PC card as a conventional portable wireless terminal unit. FIG. 14B is a perspective view illustrating the antenna arrangement part of the PC card. FIG. 14C is a cross-sectional view of the card including its enclosure taken on line  14 C- 14 C of FIG. 14B.  
           [0012]    As shown in FIGS. 14A and 14C, the wireless PC card has extended part  3620  covered with frame  3590 , top sheet metal cover  3600 , and bottom sheet metal cover  3610 . This extended part  3620  includes a plurality of antenna elements therein. In other words, as shown in FIG. 14B, extended part  3620  has conductor section  3510  serving as a first antenna element, conductor section  3520  serving as a second antenna element and ground plane  3580  on circuit board  3570 . Conductor section  3510  has feed terminal  3530  and ground terminal  3540  bending at and protruding from the edges of the conductor section. With its terminal  3540  grounded to ground plane  3580  on substrate  3570 , the conductor section serves as an inverted F-type antenna. Similarly, conductor section  3520  has feed terminal  3550  and ground terminal  3560  bending at and protruding from the edges of the conductor section. With its terminal  3560  grounded to ground plane  3580 , the conductor section serves as an inverted F-type antenna.  
           [0013]    Two antenna elements are used for the following reasons: antenna element  3510  and antenna element  3520  provide diversity; and one with better characteristics is selected from these antenna elements by switching them using a switch (not shown) when the variations in intensity of received waves are caused by such influences as fading.  
           [0014]    In general, the size of the extended part of a wireless PC card used as a wireless LAN card is determined by the standard of PC cards—54 mm in width, 40 mm in length and 10.5 mm in height. Characterized in that they have high performance and can be downsized, the inverted F-type antennas are often used for a wireless PC card.  
           [0015]    Now, the characteristics of the inverted F-type antennas are the better at the greater distance between substrate  3570  and conductor sections  3510  and  3520  (the distance shown at “h” in FIG. 14C). Therefore, it is important to make the distance “h” longer. However, when the distance “h” is determined to the limit of its standard, extended part  3620  is too large as shown in FIG. 14A, thus imposing some limitations on the design of its shape.  
         SUMMARY OF THE INVENTION  
         [0016]    The present invention addresses the above-mentioned problem and aims to provide a diversity wireless device and a wireless terminal unit that can be downsized without reduction in their diversity gains.  
           [0017]    A diversity wireless device in accordance with the present invention is structured as a diversity wireless device providing diversity using a plurality of antennas. The device has antennas that are grounded (grounded antennas) and antennas that are not grounded (ungrounded antennas).  
           [0018]    Another diversity wireless device in accordance with the present invention is structured as a diversity wireless device providing diversity using a plurality of ungrounded antennas. The device is structured so that a ground is provided in the vicinity of at least one of the ungrounded antennas and the ungrounded antenna is coupled to the ground via high-frequency waves.  
           [0019]    Still another diversity wireless device in accordance with the present invention is structured as a diversity wireless device providing diversity using a plurality of antennas. The device is structured so that it has at least one ungrounded antenna and a ground partly surrounding the ungrounded antenna and that the ungrounded antenna and the ground are coupled to each other via high-frequency waves.  
           [0020]    These structures allow downsizing of the devices without reducing their diversity gains.  
           [0021]    A wireless terminal unit in accordance with the present invention is structured as a wireless terminal unit having an antenna element. The terminal unit is structured so that the antenna element includes:  
           [0022]    (a) a substrate;  
           [0023]    (b) a first conductor section substantially parallel to the substrate; and  
           [0024]    (c) a second conductor section successively formed from the first conductor section and angularly arranged relative to said substrate.  
           [0025]    This structure allows a change in the height of the antenna element part, thus offering an advantage of reducing limitations on the design of the antenna part. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1 shows a structure of a diversity wireless device in accordance with a first exemplary embodiment of the present invention.  
         [0027]    [0027]FIG. 2 shows a structure of a diversity wireless device in accordance with a second exemplary embodiment of the present invention.  
         [0028]    [0028]FIG. 3 shows a structure of a diversity wireless device in accordance with a third exemplary embodiment of the present invention.  
         [0029]    [0029]FIG. 4 shows a structure of a diversity wireless device in accordance with a fourth exemplary embodiment of the present invention.  
         [0030]    [0030]FIG. 5 shows a structure of a diversity wireless device in accordance with a fifth exemplary embodiment of the present invention.  
         [0031]    [0031]FIG. 6 shows a structure of a diversity wireless device in accordance with a sixth exemplary embodiment of the present invention.  
         [0032]    [0032]FIG. 7 is a cross-sectional view of the antenna part of the same device in FIG. 6.  
         [0033]    [0033]FIG. 8 shows a structure of a diversity wireless device in accordance with a seventh exemplary embodiment of the present invention.  
         [0034]    [0034]FIG. 9 is a cross-sectional view of the antenna part of the same device in FIG. 8.  
         [0035]    [0035]FIG. 10 is a sketch drawing of the diversity wireless device in accordance with the first embodiment of the present invention.  
         [0036]    [0036]FIG. 11A is a perspective view illustrating an appearance of a wireless PC card as a wireless terminal unit in accordance with an eighth exemplary embodiment of the present invention.  
         [0037]    [0037]FIG. 11B is a perspective view illustrating the antenna arrangement part on the same PC card in FIG. 11A.  
         [0038]    [0038]FIG. 11C is a cross-sectional view of the device including its enclosure taken on line  11 C- 11 C of FIG. 11B.  
         [0039]    [0039]FIG. 12 is a perspective view of an antenna arrangement part on a wireless PC card in accordance with a ninth exemplary embodiment of the present invention.  
         [0040]    [0040]FIG. 13 is a perspective view of an antenna arrangement part on a wireless PC card in accordance with a tenth exemplary embodiment the present invention.  
         [0041]    [0041]FIG. 14A is a perspective view illustrating an appearance of a wireless PC card as a conventional wireless terminal unit.  
         [0042]    [0042]FIG. 14B is a perspective view illustrating the antenna arrangement part on the same PC card in FIG. 14A.  
         [0043]    [0043]FIG. 14C is a cross-sectional view of the same card including its enclosure taken on line  14 C- 14 C of FIG. 14B.  
         [0044]    [0044]FIG. 15 shows a structure of a conventional diversity wireless device. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0045]    Exemplary embodiments of the present invention are hereinafter demonstrated with reference to the accompanying drawings.  
         [0046]    (First Embodiment)  
         [0047]    [0047]FIG. 1 shows a structure of a diversity wireless device in accordance with the first embodiment of the present invention and FIG. 10 is a sketch drawing of the same device.  
         [0048]    As shown in FIG. 10, diversity wireless device  81  is of a PC card type and has connector part  82  for insertion into a PC card slot (not shown) and connection thereto. The device  81  is connected to such networking equipment as a gateway unit that has a PC card slot, a portable PC, or the like, and used for wireless data transmission/reception.  
         [0049]    Next, the internal structure of device  81  is described with reference to FIG. 1.  
         [0050]    In FIG. 1, substrate  11  has an antenna  13  that is grounded (grounded antenna) and an antenna  14  that is not grounded (ungrounded antenna) mounted thereon. Formed on substrate  11  is ground plane  12 . Grounded antenna  13  has feed terminal  131  and ground terminal  132 . This ground terminal  132  supports antenna  13 , and moreover, electrically connects it to ground plane  12 . Ungrounded antenna  14  has feed terminal  141  and support terminal  142  for supporting antenna  14 . This support terminal  142  is not grounded. Substrate  11  also has RF circuit  15  mounted thereon. The ground of RF circuit  15  connects to ground plane  12 . RF circuit  15  switches transmission/reception antennas, feeds power into the antennas, and processes received signals.  
         [0051]    In this structure, antenna  13  is a so-called inverted F-type antenna, in which ground plane  12  also affects the antenna characteristics. On the other hand, antenna  14  is completely isolated from antenna  13  and ground plane  12 . Therefore, antennas  13  and  14  have a low degree of correlation therebetween and providing diversity using these antennas gives a high diversity gain.  
         [0052]    (Second Embodiment)  
         [0053]    [0053]FIG. 2 shows a structure of a diversity wireless device in accordance with the second embodiment of the present invention.  
         [0054]    In FIG. 2, substrate  21  has grounded antenna  23  and ungrounded antenna  24  mounted thereon. Formed on substrate  21  is ground plane  22 . Antenna  23  has feed terminal  231  and ground terminal  232 . This ground terminal  232  supports antenna  23 , and moreover, electrically connects it to ground plane  22 . Antenna  24  has feed terminal  241 . Substrate  21  also has RF circuit  25  mounted thereon. The ground of RF circuit  25  connects to ground plane  22 . RF circuit  25  switches transmission/reception antennas, feeds power into the antennas, and processes received signals.  
         [0055]    In this second embodiment, an antenna with a meander pattern formed on a separate substrate is used as ungrounded antenna  24  instead of ungrounded antenna  14  of the first embodiment in FIG. 1.  
         [0056]    Using an antenna of a different structure in this manner can make a low degree of correlation between antennas  23  and  24 , thus giving a diversity effect utilizing the advantage of each antenna. The pattern of meander antenna may be formed directly on substrate  21 .  
         [0057]    When diversity is provided using two antennas  23  and  24 , the device of this second embodiment can attain a high diversity gain similar to that attained with the device of the first embodiment.  
         [0058]    (Third Embodiment)  
         [0059]    [0059]FIG. 3 shows a structure of a diversity wireless device in accordance with the third embodiment of the present invention.  
         [0060]    In FIG. 3, substrate  31  has grounded antenna  33  and ungrounded antenna  34  mounted thereon. Formed on substrate  31  is ground plane  32 . Antenna  33  has feed terminal  331  and ground terminal  332 . This ground terminal  332  supports antenna  33 , and moreover, electrically connects it to ground plane  32 . Antenna  34  has feed terminal  341  and support terminal  342  for supporting antenna  34 . This terminal  342  is not grounded. Substrate  31  also has RF circuit  35  mounted thereon. The ground of RF circuit  35  connects to ground plane  32 . RF circuit  35  switches transmission/reception antennas, feeds power into the antennas, and processes received signals.  
         [0061]    In the above structure, setting the angle between antennas  33  and  34  to a predetermined value, e.g. 90°, can make a low degree of correlation therebetween and can also give a polarization diversity effect. This provides a diversity wireless device having a great diversity gain.  
         [0062]    (Fourth Embodiment)  
         [0063]    [0063]FIG. 4 shows a structure of a diversity wireless device in accordance with the fourth embodiment of the present invention.  
         [0064]    In FIG. 4, substrate  41  has grounded antenna  43  and an ungrounded antenna  44  mounted thereon. Formed on substrate  41  is ground plane  42 . Antenna  43  has feed terminal  431  and ground terminal  432 . This ground terminal  432  supports antenna  43 , and moreover, electrically connects it to ground plane  42 . Antenna  44  has feed terminal  441  and support terminal  442  for supporting antenna  44 . This terminal  442  is not grounded. Substrate  41  also has RF circuit  45  mounted thereon. The ground of RF circuit  45  connects to ground plane  42 . RF circuit  45  switches transmission/reception antennas, feeds power into the antennas, and processes received signals.  
         [0065]    In the fourth embodiment, ground plane  42  is disposed in close proximity to supporting terminal  442  so as to couple antenna  44  to the ground via high-frequency waves.  
         [0066]    As shown in the above-mentioned structure, ground plane  42  is disposed in close proximity to antenna  44  and the antenna is coupled to the ground via high-frequency waves. This allows antenna  44  to have wider directivity and maintains a low degree of correlation between the both antennas, thus providing a diversity wireless device with a greater diversity gain.  
         [0067]    In the fourth embodiment, the coupling via high-frequency waves is performed between ground plane  42  formed on the front layer of substrate  41  as shown in FIG. 4 and the both antennas. Such coupling, however, can also be performed between ground plane  42  formed on the inner layer or back layer of substrate  41  and the both antennas.  
         [0068]    (Fifth Embodiment)  
         [0069]    [0069]FIG. 5 shows a structure of a diversity wireless device in accordance with the fifth embodiment of the present invention.  
         [0070]    In FIG. 5, substrate  51  has two ungrounded antennas  53  and  54  mounted thereon. Formed on substrate  51  is ground plane  52 . Antenna  53  has feed terminal  531  and support terminal  532  for supporting antenna  53 . This terminal  532  is not grounded. Antenna  54  has feed terminal  541  and support terminal  542  for supporting antenna  54 . This terminal  542  is not grounded. Substrate  51  also has RF circuit  55  mounted thereon. The ground of RF circuit  55  connects to ground plane  52 . RF circuit  55  switches transmission/reception antennas, feeds power into the antennas, and processes received signals.  
         [0071]    In the fifth embodiment, ground plane  52  is disposed in close proximity to terminals  532  and  542  so as to couple the both antennas to the ground via high-frequency waves.  
         [0072]    As shown in the above-mentioned structure, ground plane  52  is disposed in close proximity to antennas  53  and  54  and the both antennas are coupled to the ground via high-frequency waves. This allows the both antennas to have wider directivity while maintaining a low degree of correlation between the both antennas, thus giving an effect of excellent space diversity.  
         [0073]    Moreover, when the angle between the both antennas is set to 90° so that one essentially receives signals in a horizontally polarized wave surface and the other essentially receives signals in a vertically polarized wave surface, an effect of polarization diversity can also be obtained.  
         [0074]    In the fifth embodiment, the coupling via high-frequency waves is performed between ground plane  52  formed on the front layer of substrate  51  as shown FIG. 5 and the both antennas. Such coupling, however, can also be performed between ground plane  52  formed on the inner layer or back layer of substrate  51  and the both antennas.  
         [0075]    (Sixth Embodiment)  
         [0076]    [0076]FIG. 6 shows a structure of a diversity wireless device in accordance with the sixth embodiment of the present invention and FIG. 7 is a cross-sectional view of the antenna part of the same device.  
         [0077]    In FIG. 6, substrate  61  has two ungrounded antennas  63  and  64  mounted thereon. Formed on substrate  61  is ground plane  621  and island-like conductors  634  and  644  surrounded by this ground plane  621 . Antenna  63  has feed terminal  631  and support terminal  632  for supporting antenna  63 . This terminal  632  is connected to conductor  634  but ungrounded. Similarly, antenna  64  has feed terminal  641  and support terminal  642  for supporting antenna  64 . This terminal  642  is connected to conductor  644  but ungrounded. Substrate  61  also has RF circuit  65  mounted thereon. The ground of RF circuit  65  connects to ground plane  621 . RF circuit  65  switches transmission/reception antennas, feeds power into the antennas, and processes received signals.  
         [0078]    In the sixth embodiment, as shown in FIG. 7, substrate  61  is composed of a multi-layer substrate. Formed on the first layer of substrate  61  is ground plane  621 . Formed on the second layer of substrate  61  is ground plane  622 . Now, support terminal  632  made of a conductive member connects conductors  633  and  634 . Similarly, support terminal  642  made of a conductive member connects conductors  643  and  644 . The ground of RF circuit  65  is connected to ground planes  621  and  622  directly or via thorough holes, and the like.  
         [0079]    In accordance with the sixth embodiment, conductors  634  and  644 , a part of the each antenna, are coupled to ground planes  621  and  622  via high-frequency waves. This allows the both antennas to have wider directivity while maintaining a lower correlation between the both antennas, thus giving an effect of excellent space diversity.  
         [0080]    Moreover, when the angle between the both antennas is set to 90° so that one essentially receives signals in a horizontally polarized wave surface and the other essentially receives signals in a vertically polarized wave surface, an effect of polarization diversity can also be obtained.  
         [0081]    In the sixth embodiment, conductors  633  and  643  are arranged in parallel to substrate  61 . However, the present invention is not necessarily limited to this arrangement. Furthermore, conductors  634  and  644  are not necessarily formed on substrate  61  and may be formed on the antenna side. Although both antennas  63  and  64  are ungrounded in this embodiment, the device may be structured to have one grounded antenna.  
         [0082]    (Seventh Embodiment)  
         [0083]    [0083]FIG. 8 shows a structure of a diversity wireless device in accordance with the seventh embodiment of the present invention and FIG. 9 is a cross-sectional view of the antenna part of the same device.  
         [0084]    In FIG. 8, substrate  71  has two ungrounded antennas  73  and  74  mounted thereon. In the seventh embodiment, as shown in FIG. 9, substrate  71  is composed of a multi-layer substrate. Formed on the first layer of substrate  71  is ground plane  721 . Formed on the second layer of substrate  71  is ground plane  722  and island-like conductors  734  and  744 , each surrounded by this ground plane  722 . Formed on the third layer of substrate  71  is ground plane  723 .  
         [0085]    Antenna  73  has feed terminal  731  and support terminal  732  for supporting antenna  73 . This terminal  732  is connected to conductor  734  but ungrounded. Similarly, antenna  74  has feed terminal  741  and support terminal  742  for supporting antenna  74 . This terminal  742  is connected to conductor  744  but ungrounded. Substrate  71  also has RF circuit  75  mounted thereon. The ground of RF circuit  75  connects to ground plane  721 . RF circuit  75  switches transmission/reception antennas, feeds power into the antennas, and processes received signals.  
         [0086]    In the seventh embodiment, antenna  73  is composed of feed terminal  731 , support terminal  732  made of a conductive member, conductor  733  formed in parallel to substrate  71 , and conductor  734  formed on the second layer of substrate  71 . Support terminal  732  connects conductors  733  and  734 . Similarly, antenna  74  is composed of feed terminal  741 , support terminal  742  made of a conductive member, conductor  743  formed in parallel to substrate  71 , and conductor  744  formed on the second layer of substrate  71 . Support terminal  742  connects conductors  743  and  744 . Thus, each of conductors  734  and  744  is surrounded by ground plane  721  on its top face, by ground plane  722  on its side faces and by ground plane  723  on its bottom face. In other words, the conductors are surrounded by ground planes three-dimensionally. The ground of RF circuit  75  is connected to each of ground planes  721 ,  722  and  723  directly or via thorough holes, and the like.  
         [0087]    In accordance with the seventh embodiment shown above, conductors  734  and  744 , a part of the antennas, are coupled to each of ground planes  721 ,  722  and  723  via high-frequency waves. This allows the both antennas to have wider directivity while maintaining a low degree of correlation between the both antennas, thus giving an effect of excellent space diversity.  
         [0088]    Moreover, when the angle between the both antennas is set to 90° so that one essentially receives signals in a horizontally polarized wave surface and the other essentially receives signals in a vertically polarized wave surface, an effect of polarization diversity can also be obtained.  
         [0089]    In the seventh embodiment, conductors  733  and  743  are arranged in parallel to substrate  71 . However, the present invention is not necessarily limited to this arrangement.  
         [0090]    In addition, it is possible to form conductors  734  and  744  on the lowermost layer of the substrate, place a ground plane on the next layer and couple conductors  734  and  744  to the ground plane via high-frequency waves. Although both antennas  73  and  74  are ungrounded in this embodiment, the device may be structured to have one grounded antenna.  
         [0091]    (Eighth Embodiment)  
         [0092]    [0092]FIG. 11A is a perspective view illustrating an appearance of a wireless PC card as a wireless terminal unit in accordance with the eighth embodiment of the present invention. FIG. 11B is a perspective view illustrating an antenna arrangement part of the PC card. FIG. 11C is a cross-sectional view of the card including its enclosure taken on line  11 C- 11 C of FIG. 11B.  
         [0093]    As shown in FIGS. 11B and 11C, the PC card of the eighth embodiment has circuit board  1007  having first antenna element  1001 , second antenna element  1002 , and ground plane  1008 .  
         [0094]    Antenna element  1001  has first conductor section  1011  made of such materials as a sheet metal, and second conductor section  1012  made of such materials as a sheet metal bent at an obtuse angle from conductor section  1011  and successively formed therefrom. Bent at and protruding from the edges of conductor section  1011  are feed terminal  1003  and ground terminal  1004  for the antenna element. Similarly, antenna element  1002  has first conductor section  1021  made of such materials as a sheet metal, and second conductor section  1022  made of such materials as a sheet metal bent at an obtuse angle from conductor section  1021  and successively formed therefrom. Bent at and protruding from the edges of conductor section  1021  are feed terminal  1005  and ground terminal  1006 . Conductor section  1012  is inclined toward its end face away from feed terminal  1003  of conductor section  1011 (see FIG. 11C). The inclination is such that the space between conductor section  1012  and substrate  1007  gradually reduces toward the above-mentioned end face. Similarly, conductor section  1022  is inclined toward its end face away from feed terminal  1005  of conductor section  1021 . Antenna elements  1001  and  1002  are grounded to ground plane  1008  on substrate  1007  via terminals  1004  and  1006 , respectively, and act as inverted F-type antennas.  
         [0095]    The structure of the PC card is further detailed below.  
         [0096]    Conductor section  1011  of antenna element  1001  and conductor section  1021  of antenna element  1002  are maintained in parallel to the face of substrate  1007  and are also widely spaced therefrom by feed terminals  1003  and  1005 , respectively. In addition, conductor sections  1012  and  1022  are angularly arranged relative to substrate  1007 . Then, the entire part including both antenna elements  1001  and  1002  is covered with frame  1009 , an armor, to form extended part  1120 . Provided over substrate  1007  on both sides are top sheet metal cover  1100  and bottom sheet metal cover  1110 , respectively.  
         [0097]    By providing both antenna elements  1001  and  1002  in the above-mentioned manner, extended part  1120  of the card can be designed to a shape with a ramp along the both antenna elements instead of a simple box type. This allows the shape of extended part  1120  to be made substantially smaller.  
         [0098]    Now, comparison of the gain characteristics of the antenna elements is made between this embodiment and conventional examples. The shape of antenna element  1002  shown in FIG. 11B is described below. The space between conductor section  1021  of antenna element  1002  and substrate  1007  is set to 5.5 mm. A portion 5 mm spaced from the tip of conductor section  1022  is inclined at an angle of 20° relative to substrate  1007 . For the conventional example shown in FIG. 14B, the space between antenna element  3520  and substrate  3570  is set to 3 mm and 5.5 mm. Then, antenna gains were measured in the case of this embodiment and in the above-mentioned two cases of the conventional example. The measurement was performed in a shield room. A standard hone antenna transmitted continuous waves at a frequency of 2.4 GHz, and antenna elements to be measured received the waves. While the antenna elements were rotated 360°, their gain characteristics were measured with a spectrum analyzer. The average of the measurements was obtained as the results shown in Table 1.  
                                             TABLE 1                                   Space between               antenna element   Antenna           and substrate   gain           [mm]   [dBi]                                        This embodiment   5.5   −3.92           Conventional example (1)   3.0   −7.83           Conventional example (2)   5.5   −3.41                      
 
         [0099]    In comparison of the two conventional examples, increase in the space “h” between the antenna element and the substrate has improved the gain characteristics of the antenna element by approx. 4.4 dB. However, for the PC card in accordance with the conventional example (2), a large extended part cannot be helped.  
         [0100]    On the other hand, in comparison with the conventional example (1), the performance of the PC card of this embodiment is better by approx. 3.9 dB. Furthermore, although the PC card of this embodiment is slightly inferior to that of the conventional example (2) in point of gains, the extended part of this embodiment can be shaped smaller by providing a ramp conforming to the shape of the antenna elements.  
         [0101]    As described above, the structure of this eighth embodiment is effective in ensuring the performance of the antenna elements and shaping the extended part substantially smaller.  
         [0102]    In this eighth embodiment, the invention is described using two inverted F-type antennas as an example. However, the shapes and types of the antenna elements are not limited to the above and other types of antenna elements can be used in combination. In addition, the wireless terminal unit is not limited to a wireless PC card.  
         [0103]    (Ninth Embodiment)  
         [0104]    [0104]FIG. 12 is a perspective view illustrating the antenna arrangement part of a wireless PC card in accordance with the ninth embodiment of the present invention.  
         [0105]    As shown in FIGS.  12 , the PC card of the ninth embodiment has circuit board  1270  having first antenna element  1210 , second antenna element  1220 , and ground plane  1280 .  
         [0106]    Antenna element  1210  has first conductor section  1211  made of such materials as a sheet metal, and second conductor section  1212  made of such materials as a sheet metal bent at an obtuse angle from the first conductor section and successively formed therefrom. Bent at and protruding from the edges of conductor section  1211  are feed terminal  1230  and ground terminal  1240  for the antenna element. Similarly, antenna element  1220  has first conductor section  1221  made of such materials as a sheet metal, and second conductor section  1222  made of such materials as a sheet metal bent at an obtuse angle from the first conductor section and successively formed therefrom. Bent at and protruding from the edges of conductor section  1221  are feed terminal  1250  and ground terminal  1260 . Antenna elements  1210  and  1220  are grounded to ground plane  1280  on substrate  1270  via terminals  1240  and  1260 , respectively, and act as inverted F-type antennas.  
         [0107]    In addition, conductor sections  1211  and  1221  are maintained in parallel to the face of substrate  1270  and also widely spaced therefrom by terminals  1230  and  1250 , respectively. Conductor sections  1212  and  1222  are angularly arranged relative to substrate  1270 , respectively.  
         [0108]    The feature of the ninth embodiment is the laterally symmetrical arrangement of antenna elements  1210  and  1220  with respect to the longitudinal axis of the PC card.  
         [0109]    The above arrangement of the ninth embodiment makes the gain characteristics of the two antenna elements equal and their directivity substantially laterally symmetrical, thus allowing efficient diversity reception.  
         [0110]    In the ninth embodiment, providing a slight size difference between the right and left antenna elements allows correction of the displacement of matching points in the operating frequencies of the antenna elements caused by such influences as the layout of peripheral devices. The correction method can be selected among various ones. For example, conductor section  1212  can be made longer than conductor section  1222 .  
         [0111]    In this ninth embodiment, the invention is described using two inverted F-type antennas as an example. However, the shapes and types of the antenna elements are not limited to the above. In addition, the wireless terminal unit is not limited to a wireless PC card.  
         [0112]    (Tenth Embodiment)  
         [0113]    [0113]FIG. 13 is a perspective view illustrating the antenna arrangement part of a wireless PC card in accordance with the tenth embodiment of the present invention.  
         [0114]    As shown in FIGS.  13 , the PC card of the tenth embodiment has first antenna element  1310 , second antenna element  1320 , and circuit board  1370  having ground plane  1380 .  
         [0115]    Antenna element  1310  has first conductor section  1311  made of such materials as a sheet metal, and second conductor section  1312  made of such materials as a sheet metal bent at an obtuse angle from the first conductor section and successively formed therefrom. Bent at and protruding from the edges of conductor section  1311  are feed terminal  1330  and support terminal  1340 . Similarly, antenna element  1320  has first conductor section  1321  made of such materials as a sheet metal, and second conductor section  1322  made of such materials as a sheet metal bent at an obtuse angle from the first conductor section and successively formed therefrom. Bent at and protruding from the edges of conductor section  1321  are feed terminal  1350  and support terminal  1360 . Support terminals  1340  and  1360  are both ungrounded.  
         [0116]    In substrate  1370 , third conductor sections  1391  and  1392  are formed on the top face of ground plane  1380  electrically insulated therefrom. Ungrounded antenna elements  1310  and  1320  are coupled to conductor sections  1391  and  1392 , respectively, via high-frequency waves. Conductor sections  1391  and  1392 , in turn, are structured as a part of conductor sections of antenna elements  1310  and  1320 , respectively.  
         [0117]    Conductor sections  1311  and  1321  are maintained in parallel to the face of substrate  1370  and also widely spaced therefrom by terminals  1330  and  1350 , respectively. In addition, conductor sections  1312  and  1322  are angularly arranged relative to substrate  1370 , respectively. Substrate  1370  is also provided with connector  1400  having a switch, and external antenna  1410  can be connected to the connector, if required.  
         [0118]    The feature of the tenth embodiment is that the both antenna elements  1310  and  1320  are ungrounded. This arrangement maintains a lower correlation between the both antennas. Furthermore, placing ground plane  1380  in close proximity to the both antenna elements and coupling the ground plane to the elements via high-frequency waves allows respective antennas to have wider directivity, thus giving an excellent diversity effect.  
         [0119]    In the tenth embodiment, the ground plane to be coupled to the both antenna elements via high-frequency waves is formed on the front face of substrate  1370 . The ground plane, however, can be formed on the inner layer or the back face of a multi-layer substrate.  
         [0120]    The card of the tenth embodiment has connector  1400 . When external antenna  1410  is connected to connector  1400 , internal second antenna element  1320  is switched to the external antenna  1410  to provide diversity using external antenna  1410  and first antenna element  1310 .  
         [0121]    Desirably, connector  1400  is placed between two antenna elements depending on the layout of circuit elements; however, that position is not specifically designated.  
         [0122]    In this tenth embodiment, the invention is described using two inverted F-type antennas as an example. However, the shapes and types of the antenna elements are not limited to the above. In addition, the wireless terminal unit is not limited to a wireless PC card.