Abstract:
A terminal apparatus adapted to receive a wireless signal by antenna diversity, wherein provisions are made to reduce the number of receive circuits while also reducing the time required for antenna selection. The a terminal apparatus is adapted to receive a wireless signal by antenna diversity, and includes: a mode-of-use detection unit for detecting the mode of use of the terminal apparatus as set up by a user; a storage unit for storing priority information that predefines an antenna to be selected for use by prioritizing the plurality of antennas according to the mode of use that can be detected by the mode-of-use detection unit; and a comparator for outputting selection control information specifying at least one antenna from among the plurality of antennas by comparing the mode of use detected by the mode-of-use detection unit with the priority information stored in the storage unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2008-167390, filed on Jun. 26, 2008, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments disclosed herein are directed to a terminal apparatus equipped with a plurality of antennas and adapted to receive a wireless signal by antenna diversity, and a diversity antenna control method for the same. 
       BACKGROUND 
       [0003]    Conventionally, personal computers (PCs), i.e., notebook PCs or laptop PCs have been used by placing them on desks. It has therefore been possible to obtain satisfactory antenna performance by mounting an antenna  102  above a liquid crystal display (LCD)  104  as illustrated in  FIG. 1A . 
         [0004]    In recent years, tablet PCs, such as the one illustrated in  FIG. 1B , have been introduced into the market. The tablet PC is held by hand when in use. In this case, when the user&#39;s hand is placed in contact with the mounting portion of the antenna  102 , the antenna performance drops. Further, when the user tilts the PC when in use, the antenna performance drops. 
         [0005]    Similar problems also occur with notebook PCs as size reductions are made. On the other hand, a convertible PC having a 180-degree rotatable LCD and transformable from a notebook to a tablet PC and vice versa has been introduced into the market. Antenna performance degradation also becomes a problem with the convertible PC. 
         [0006]    One possible approach to addressing the problem of antenna performance degradation is to mount a plurality of antennas  102  as diversity antennas, as illustrated in  FIGS. 2A and 2B , and to receive data from one of the antennas that provides the best performance. By providing, for example, as many receive circuits as there are antennas and by detecting the received signal strength from each antenna and selecting the appropriate receive circuit, good communication quality can be maintained (refer, for example, to patent documents 1 and 2 listed below). However, the cost increases because this configuration requires the provision of as many receive circuits as there are antennas. 
         [0007]    Another possible approach, which eliminates the need to provide as many receive circuits as the number of antennas, is to sequentially select the antennas for connection to the receive circuit and detect the received signal strength from each antenna (refer, for example, to patent documents 3 to 5 listed below). However, in this configuration, it takes time to select the receiving antenna because switching has to be made from one antenna to another in sequence. 
         [0008]    Patent document 1: Japanese Unexamined Patent Publication No. 2006-245801 
         [0009]    Patent document 2: Japanese Unexamined Patent Publication No. 2007-235305 
         [0010]    Patent document 3: Japanese Unexamined Patent Publication No. 2005-142866 
         [0011]    Patent document 4: Japanese Unexamined Patent Publication No. 2005-130175 
         [0012]    Patent document 5: Japanese Unexamined Patent Publication No. H11-150490 
       SUMMARY 
       [0013]    According to one aspect of the art disclosed herein, a terminal apparatus which is adapted to receive a wireless signal by antenna diversity includes: a mode-of-use detection unit which detects the mode of use of the terminal apparatus as set up by a user; a storage unit for storing priority information that predefines an antenna to be selected for use by prioritizing a plurality of antennas according to the mode of use that can be detected by the mode-of-use detection unit; a control unit which outputs selection control information specifying at least one antenna from among the plurality of antennas by comparing the mode of use detected by the mode-of-use detection unit with the priority information stored in the storage unit; and a selector which connects the antenna specified by the selection control information to a receive circuit provided at a subsequent stage. 
         [0014]    According to another aspect of the art disclosed herein, there are provided a diversity antenna control methods to be implemented in the above terminal apparatus, and a recording medium having a program recorded thereon for causing a computer as the terminal apparatus to implement the method. 
         [0015]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0016]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1A  is a diagram illustrating a notebook (laptop) personal computer (PC), and  FIG. 1B  is a diagram illustrating a tablet PC. 
           [0018]      FIG. 2A  is a diagram illustrating a notebook PC equipped with diversity antennas, and  FIG. 2B  is a diagram illustrating a tablet PC equipped with diversity antennas. 
           [0019]      FIGS. 3A and 3B  are diagrams explaining the basic functional mode of a terminal apparatus according to the present disclosure:  FIG. 3A  illustrates an external view of a notebook PC according to the present disclosure, and  FIG. 3B  illustrates an external view of a tablet PC according to the present disclosure. 
           [0020]      FIG. 4  is a diagram illustrating the configuration of a wireless receiver according to the basic functional mode. 
           [0021]      FIGS. 5A to 5D  are diagrams explaining a first embodiment of the terminal apparatus according to the present disclosure:  FIG. 5A  illustrates an external view,  FIG. 5B  illustrates the arrangement of antennas and sensors,  FIG. 5C  illustrates a tilt sensor, and  FIG. 5D  illustrates the apparatus in a tilted position. 
           [0022]      FIG. 6  is a diagram illustrating the configuration of a wireless receiver according to the first embodiment. 
           [0023]      FIG. 7  is a diagram illustrating the contents of a data table according to the first embodiment. 
           [0024]      FIG. 8  is a flowchart of a wireless connection process according to the first embodiment. 
           [0025]      FIG. 9  is a diagram illustrating the configuration of a radio receiver in a second embodiment of the terminal apparatus according to the present disclosure. 
           [0026]      FIG. 10  is a diagram illustrating the contents of a data table according to the second embodiment. 
           [0027]      FIG. 11  is a flowchart of a wireless connection process according to the second embodiment. 
           [0028]      FIGS. 12A and 12B  are diagrams explaining a third embodiment of the terminal apparatus according to the present disclosure:  FIG. 12A  illustrates an external view of the apparatus when used as a notebook PC, and  FIG. 12B  illustrates an external view of the apparatus when used as a tablet PC. 
           [0029]      FIG. 13  is a diagram illustrating the configuration of a wireless receiver according to the third embodiment. 
           [0030]      FIG. 14  is a diagram illustrating the contents of a data table according to the third embodiment. 
           [0031]      FIG. 15  is a flowchart of a wireless connection process according to the third embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0032]    The preferred embodiments of the present invention will be explained with reference to the accompanying drawings. 
         [0033]      FIGS. 3A and 3B  are diagrams for explaining the basic functional mode of a terminal apparatus according to the present disclosure:  FIG. 3A  illustrates an external view of a notebook PC according to the present disclosure, and  FIG. 3B  illustrates an external view of a tablet PC according to the present disclosure. The notebook PC illustrated in  FIG. 3A  is equipped with a plurality of antennas  302 , and receives a wireless signal by antenna diversity. 
         [0034]    The notebook PC includes contact sensors  304 , one for each antenna  302 , for sensing contact near the mounting portions of the respective antennas. The notebook PC further includes a tilt sensor for sensing tilting of the PC relative to the horizontal plane. Likewise, the tablet PC illustrated in  FIG. 3B  includes a plurality of antennas  302  and a plurality of contact sensors  304 .  FIGS. 3A and 3B  are also diagrams illustrating a single convertible PC having a 180-degree rotatable LCD and transformable from a notebook to a tablet PC and vice versa. 
         [0035]      FIG. 4  is a diagram illustrating the configuration of a wireless receiver according to the basic functional mode illustrated in  FIGS. 3A and 3B . The wireless receiver comprises a plurality of antennas  302 , an antenna selector  402 , a communication module  410 , a mode-of-use detection unit  420 , a storage unit  430 , and a comparator  440 . The antenna selector  402  selects one antenna  302  based on an antenna select signal from the comparator  440  for connection to the communication module  410 . The communication module  410  includes a receive circuit  412  for receiving a signal from the selected antenna  302 , a demodulator  414  for demodulating the received wave from the receive circuit, and a controller  416  for receiving the received data and RSSI (Received Signal Strength Indicator) from the demodulator. 
         [0036]    The mode-of-use detection unit  420  includes a contact detection unit  422  constructed from the plurality of contact sensors  304  illustrated in  FIGS. 3A and 3B , a tilt detection unit  424  constructed from the tilt sensor  306  illustrated in  FIGS. 3A and 3B , and an LCD rotation detection unit  426 . When the LCD is 180-degree rotatable in swiveling fashion so that the terminal apparatus can be used not only as a notebook PC but also as a tablet PC, the LCD rotation detection unit  426  detects the swiveling rotation of the LCD and outputs LCD rotation information that indicates in which mode, a notebook mode or a tablet mode, the terminal apparatus is currently used. 
         [0037]    The storage unit  430  stores a data table (priority information)  432  which predefines the antenna to be selected for use by prioritizing the antennas according to the mode of use that can be detected by the mode-of-use detection unit  420 . The comparator  440  as a control unit compares the contact information, tilt information, LCD rotation information, etc. from the mode-of-use detection unit  420  with the table information from the data table  432 , determines the antenna that best suits the current mode of use of the apparatus as set up by the user, and supplies the antenna select signal as selection control information to the antenna selector  402 . The comparator  440  includes a memory into which a program is loaded, and a processor which executes the program loaded into the memory. Specific embodiments will be described in detail below. 
         [0038]      FIGS. 5A to 5D  are diagrams for explaining a first embodiment of the terminal apparatus according to the present disclosure:  FIG. 5A  illustrates an external view,  FIG. 5B  illustrates the arrangement of antennas and sensors,  FIG. 5C  illustrates the tilt sensor, and  FIG. 5D  illustrates the apparatus in a tilted position. The portable terminal apparatus illustrated here is a notebook PC, as illustrated in  FIG. 5A . As illustrated in  FIG. 5B , the antennas A 1  to A 4  are mounted near the four corners of the operation panel  502  on which a keyboard, etc., are arranged. There are also mounted the contact sensors S 1  to S 4 , one for each of the antennas A 1  to A 4 , for sensing contact with the mounting portions of the respective antennas. 
         [0039]    Further, the tilt sensor  504  is mounted near the center of the operation panel  502 , as illustrated in  FIG. 5B . The tilt sensor  504  is, for example, a piezoresistive three-axis acceleration sensor that can detect gravitational acceleration. This sensor detects gravitational acceleration components, ax and ay, respectively acting in the x-axis and y-axis directions parallel to the operation panel  502  and at right angles to each other. Since the positive values of ax, for example, indicate that the PC is tilted as illustrated in  FIG. 5D , relative height information for the respective antenna A 1  to A 4  can be obtained. 
         [0040]      FIG. 6  is a diagram illustrating the configuration of a wireless receiver according to the first embodiment depicted in  FIG. 5 . The antennas A 1  to A 4  are each an integrated antenna designed for both UMTS (Universal Mobile Telecommunication System) and WLAN (Wireless LAN). Examples of integrated antennas include those that support some of the communication systems selected from among UMTS, WLAN, WiMAX (Worldwide Interoperability for Microwave Access), BT (British Telecommunications), UWB (Ultra Wide Band), etc. 
         [0041]    The wireless receiver includes a UMTS module  620  and a WLAN module  630  as communication modules. An antenna selector  610  selects one antenna based on a UMTS antenna select signal from a comparator  660  for connection to the UMTS module  620 , and selects another antenna based on a WLAN antenna select signal from the comparator  660  for connection to the WLAN module  630 . 
         [0042]    The comparator  660  compares the contact information from the contact sensors S 1  to S 4 , tilt information from the tilt sensor  504 , and preferential interface (IF) information from a user setting unit  640  with the table information from a data table  650 , determines the antennas that best suit the current mode of use of the apparatus as set up by the user, and supplies the UMTS antenna select signal and WLAN antenna select signal to the antenna selector  610 . In this embodiment, the user can make a setting, through the user setting unit  640 , as to which IFs, UMTS or WLAN, is to be set as the preferential IF. 
         [0043]      FIG. 7  is a diagram illustrating the contents of the data table  650  of  FIG. 6 . In the data table  650 , the priorities of the antennas A 1  to A 4  are determined based on the contact information from the contact sensors S 1  to S 4  and the tilt information from the tilt sensor  504 . Then, based on the user-set preferential IF information, either the highest priority antenna or the second highest priority antenna is set as the UMTS antenna and the other as the WLAN antenna. 
         [0044]    The contact information indicates the presence or absence of contact with each antenna. The tilt information indicates whether the value of the x-axis component, ax, of the gravitational acceleration is positive or negative, whether the value of the y-axis component, ay, of the gravitational acceleration is positive or negative, and whether or not |ax| is larger than or equal to a given value d. The criterion |ax|≧d is used to determine in which direction, the x-axis direction or the y-axis direction, the apparatus is substantially tilted. Since the sum of the squares of the three-axis acceleration components is equal to the square of the gravitational acceleration (constant value), and the value of |ay| is limited by the value of |ax|, account need not be taken of |ay|. 
         [0045]    When determining the priorities of the antennas A 1  to A 4 , first the antennas A 1  to A 4  are divided into two groups based on whether contact is detected or not, in such a manner that any antenna where contact is detected belongs to the lower priority group while, on the other hand, any antenna where contact is not detected belongs to the higher priority group. Then, the priorities are finally determined based on the tilt information so that an antenna located at a higher position is given a higher priority. Lastly, the antennas to be used are determined based on the user-set preferential IF information, as earlier described. 
         [0046]    For example, suppose that, in the condition illustrated in  FIGS. 5A and 5B , contact is detected by the contact sensors S 2  and S 3  and the apparatus is tilted in such a manner that the height decreases in the x-axis and y-axis directions, the degree of tilting being greater in the x-axis direction, and suppose that UMTS is set as the preferential IF; in this case, antenna priority is given in the order of A 1 , A 4 , A 2 , and A 3 , so that the antenna A 1  is selected as the UMTS antenna and the antenna A 4  as the WLAN antenna. 
         [0047]      FIG. 8  is a flowchart of a wireless connection process according to the first embodiment. When a wireless connection is started, the comparator  660  starts to receive the contact information from the contact sensors S 1  to S 4  (step  802 ). Next, the comparator  660  starts to receive the tilt sensor from the tilt sensor  504  (step  804 ). Next, the comparator  660  starts to receive the preferential IF information from the user setting unit  640  (step  806 ). 
         [0048]    Then, the comparator  660  compares the information received in the above steps with the table information supplied from the data table  650  (step  808 ). Based on the results of the comparisons, the comparator  660  determines the antennas to be used, and outputs the UMTS antenna select signal and WLAN antenna select signal (step  810 ). In response to the select signals, the antenna selector  610  selects the respective antennas (step  812 ). Next, the comparator  660  determines whether the wireless connection is to be terminated (step  814 ); if the wireless connection is to be continued, the process returns to step  808 . 
         [0049]      FIG. 9  is a diagram illustrating the configuration of a radio receiver in a second embodiment of the terminal apparatus according to the present disclosure. The second embodiment also is a notebook PC and is equipped with antennas A 1  to A 4 , contact sensors S 1  and S 4 , and tilt sensor  504 , as in the first embodiment illustrated in  FIGS. 5A and 5B . However, the antennas A 1  to A 4  in the second embodiment are single-purpose antennas, i.e., WLAN antennas. The wireless receiver of the second embodiment includes a WLAN module  930  as a communication module, which includes a main receive circuit and a sub receive circuit. 
         [0050]    Based on the main antenna select signal and sub antenna select signal from a comparator  960 , an antenna selector  910  selects the corresponding antennas for connection to the main receive circuit and the sub receive circuit, respectively, in the WLAN module  930 . The comparator  960  compares the contact information from the contact sensors S 1  to S 4  and the tilt information from the tilt sensor  504  with the table information from a data table  950 , determines the antennas that best suit the current mode of use of the apparatus as set up by the user, and supplies the main antenna select signal and sub antenna select signal to the antenna selector  910 . 
         [0051]      FIG. 10  is a diagram illustrating the contents of the data table  950  of  FIG. 9 . In the data table  950 , as in the data table of the first embodiment ( FIG. 7 ), the priorities of the antennas A 1  to A 4  are determined based on the contact information from the contact sensors S 1  to S 4  and the tilt information from the tilt sensor  504 . The highest priority antenna is then specified as the main antenna and the second highest priority antenna as the sub antenna. 
         [0052]      FIG. 11  is a flowchart of a wireless connection process according to the second embodiment. This wireless connection process differs from the wireless connection process of the first embodiment ( FIG. 8 ) only in that step  806  is deleted. 
         [0053]      FIGS. 12A and 12B  are diagrams for explaining a third embodiment of the terminal apparatus according to the present disclosure:  FIG. 12B  illustrates an external view of the apparatus when used as a notebook PC, and  FIG. 12B  illustrates an external view of the apparatus when used as a tablet PC. The portable terminal apparatus illustrated here is a convertible PC that can be used not only as a notebook PC as illustrated in  FIG. 12A , but also as a tablet PC as illustrated in  FIG. 12B . 
         [0054]    This convertible PC is equipped with antennas A 1  and A 2  on the LCD side and antennas A 3  and A 4  on the operation panel side. Because of antenna directivity and antenna mounting structure, the antenna A 1  has better characteristics than the antenna A 2  and, between the antennas A 3  and A 4 , the antenna A 3  has the better characteristics. 
         [0055]      FIG. 13  is a diagram illustrating the configuration of a wireless receiver according to the third embodiment depicted in  FIG. 12 . The antenna selector  910  and WLAN module  930  in  FIG. 12  are the same as those used in the second embodiment ( FIG. 9 ). A comparator  1360  compares the LCD rotation information from a lid sensor  1320  with the table information from a data table  1350 , determines the antennas that best suit the current mode of use of the apparatus as set up by the user, and supplies the main antenna select signal and sub antenna select signal to the antenna selector  910 . 
         [0056]    The lid sensor  1320  functions as the LCD rotation detection unit  426  illustrated in  FIG. 4 . In other words, when the LCD is 180-degree rotatable so that the terminal apparatus can be used not only as a notebook PC but also as a tablet PC, the lid sensor  1320  detects the rotation of the LCD magnetically and outputs the LCD rotation information that indicates in which mode, a notebook PC mode or a tablet PC mode, the terminal apparatus is currently used. 
         [0057]      FIG. 14  is a diagram illustrating the contents of the data table  1350  of  FIG. 13 . In the data table  1350 , the priorities of the antennas A 1  to A 4  are determined based on the LCD rotation information. That is, when the apparatus is set up for use as a notebook PC as illustrated in  FIG. 12A , since the antennas A 1  and A 2  mounted on the LCD side have better reception characteristics than the antennas A 3  and A 4  mounted on the operation panel side, the antennas A 1  and A 2  are selected for use. Between the antennas A 1  and A 2 , the antenna A 1  is then selected as the main antenna for the reason described earlier. On the other hand, when the apparatus is set up for use as a tablet PC as illustrated in  FIG. 12B , since the antennas A 3  and A 4  mounted on the operation panel side have better reception characteristics than the antennas A 1  and A 2  mounted on the LCD side, the antennas A 3  and A 4  are selected for use. Between the antennas A 3  and A 4 , the antenna A 3  is then selected as the main antenna for the reason described earlier. 
         [0058]      FIG. 15  is a flowchart of a wireless connection process according to the third embodiment. This wireless connection process differs from the wireless connection process of the first embodiment ( FIG. 8 ) only in that steps  802 ,  804 , and  806  are replaced by step  1502 . In step  1502 , the comparator  1360  starts to receive the LCD rotation information from the lid sensor  1320 . The subsequent steps are the same as those in the first embodiment. 
         [0059]    Two or three of the first, second, and third embodiments described above may be combined for use. 
         [0060]    According to the terminal apparatus and the diversity antenna control method disclosed herein, the antenna to be selected for use is uniquely determined based on the mode of use of the terminal apparatus as set up by the user, without having to detect the reception strength, and the antenna performance (reception sensitivity) is improved. Accordingly, a reduction in the number of receive circuits and a reduction in antenna selection time can be accomplished simultaneously. In particular, there is achieved an improvement in the wireless communication function of terminal apparatus that are expected to become increasingly popular in the future, such as tablet PCs and other portable terminal apparatus that are supposed to be used by being held by hand or in tilted position. 
         [0061]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a illustrating of superiority and inferiority of the invention. Although the embodiments of the present invention has been described in detail, it should be understood that the various changes, substitutions, and alternations could be made hereto without departing from the spirit and scope of the invention.