Abstract:
The mobile phone ( 1 ) has an antenna arrangement ( 5 ) for radiating different radiation patterns ( 30, 35, 40 ) according to an actual operation mode of the mobile phone ( 1 ). The different radiation patterns include two radiation patterns that avoid introducing radiation into the head of a user during an active telecommunications connection. At least two operation modes of the mobile phone ( 1 ) are assigned to a different radiation patern respectively. During an active operation mode, the assigned radition pattern is selected and activated. A change between the operation mode causes switching between the assigned radiation patterns. In a preferred embodiment the radiation pattern is omindirectional ( 30 ) during an idle mode, is directional ( 35 ) during active telecomunications connections and is approximately omindirectional with a preferential direction ( 40 ) during other active telecommunications connections in which control signal are exchanged.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a mobile phone. A mobile phone including an antenna arrangement with an antenna element, which is able to radiate in two different radiation patterns, has already been described in German Patent application DE 197 23 331. 
     PRIOR ART 
     The invention proceeds from a mobile phone in accordance is with the generic class of the independent patent claim. 
     It is already known from the not yet published German patent application DE 197 23 331, that a mobile phone comprises an antenna arrangement with an antenna element which is able to radiate in two different radiation patterns. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved mobile phone of the above-described type having a plurality of operation modes, especially a mobile phone which avoids introducing radiation into the head of a user during an active telecommunications connection. 
     According to the invention the mobile phone has plural operation modes and comprises 
     an antenna arrangement for propagating radiation in a plurality of different radiation patterns Including at least two radiation patterns that are formed to avoid introducing radiation into a head of a user of the mobile phone when the phone is next to the head during an active telecommunication connection, which antenna arrangement includes one or more antenna elements; 
     means for assigning at least two of the plural operation modes to a respective different radiation pattern; 
     means for changing operation between the operation modes; and 
     means for selecting and activating an assigned radiation pattern selected from the plurality of the different radiation patterns when the corresponding operation mode is active. 
     The mobile phone according to the invention has the advantage that at least two operation modes of the mobile phone are assigned to a different radiation pattern, respectively, so that during an active operation mode the assigned radiation pattern is selected and activated, and a change between two operation modes causes switching between the assigned radiation patterns. In this way the requirements for the radiation patterns may be adapted to the actual operation mode of the mobile phone. Thereby a compromise may be achieved between the required antenna performance and the amount of radiation In the head of the user depending on the actual operation mode. A more flexible use of the mobile phone is therefore possible. 
     The features of the dependent patent claims enable further improvement of the invention. 
     It is very advantageous if only one antenna element is provided in a preferred embodiment of the antenna arrangement to realize at least two different radiation patterns. In this way, the same number of radiation patterns may be realized with fewer antenna elements Therefore, material and costs may be saved as well as weight of the mobile phone. 
     Another advantage consists in that the antenna arrangement is switchable between an omnidirectional and a directional radiation pattern. Therefore, it is possible to profit from the advantage of an omnidirectional radiation pattern with for example good overall radiation performance as well as from the advantage of a directional radiation pattern with for example a prevention of high radiation in the head of the user according to the requirements defined by the actual or activated operation mode of the mobile phone. 
     Another advantage consists in that the first radiation pattern is assigned to an idle operation mode during which the mobile phone is not in a telecommunication connection, especially in an on-hook-state, and transmitting control signals, and that second radiation pattern is assigned to a first dedicated operation mode during which the mobile phone is in an active telecommunication connection, especially in an off-hook-state. On this way, a radiation pattern may be chosen for the idle operation mode which allows good overall antenna performance, because in the idle operation mode the mobile phone may be carried inside a jacket or lying on a table and thereby preventing directional radiation. In the dedicated operation mode a directional radiation pattern may be chosen to prevent radiation into the head of the user. Therefore, a good compromise between the performance of the antenna arrangement and the prevention of radiation into the head of the user dependent on the operation mode may be realized. 
     Another advantage consists in that the third radiation pattern is assigned to a second dedicated operation mode during which the mobile phone is transmitting control signals in an active telecommunication connection, especially in an off-hook-state. On this way, a good overall performance of the antenna arrangement may be chosen in fractions of times when the mobile phone has to transmit control signals to the corresponding base station in an active telecommunication connection state. Thereby, it may be ensured that the control signals reach the corresponding base station without allowing the radiation into the head of the user during the times of the telecommunication connection where no control signals has to be transmitted. This would also represent a good compromise between telecommunication requirements to keep up a telecommunication connection using the transmission of control signals and the reduction of health risk by minimizing the radiation into the head of the user. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Examples of the invention are shown in the figures and explained in greater detail in the description below. 
     FIG. 1 shows a block diagram of a first example of a mobile phone according to the invention, 
     FIG. 2 shows a block diagram of a second example of a mobile phone according to the invention, 
     FIG. 3 shows a combined radiation pattern, and 
     FIG. 4 shows an algorithm for a baseband part in the mobile phone to select a radiation pattern. 
    
    
     DESCRIPTION 
     In FIG. 1 designates  1  a mobile phone comprising a baseband part  20  and a radio frequency part  25 . The baseband part  20  is connected to the radio frequency part  25 . The radio frequency part  25  is connectable via a first switch  45  to a first antenna element  10  providing a first radiation pattern  30  which is an omnidirectional radiation pattern. The radio frequency part  25  is connectable to a second antenna element  15  via a second switch  50 , the second antenna element  15  providing a second radiation pattern  35  which is a directional radiation pattern. The radio frequency part  25 , the first switch  45  and the second switch  50  are arranged in a first radio frequency module  70 . The first switch  45  is controlled via a first control line  80  by the baseband part  20 . The second switch  50  is controlled via a second control line  85  by the baseband part  20 . The first antenna element  10  and the second antenna element  15  constitute an antenna arrangement  5 . 
     According to FIG. 1, the first switch  45  is closed and the second switch  50  is open. Therefore, only the first antenna element  10  is connected to the radio frequency part  25 . 
     Therefore, the omnidirectional radiation pattern  30  is selected for the transmission of signals from the mobile phone  1 . The omnidirectional radiation pattern  30  is assigned to an idle operation mode during which the mobile phone  1  is not in a telecommunication connection as for example an active call. Thereby, the mobile phone  1  normally is in an on-hook-state but may also be in an off-hook-state. In the idle operation mode, the mobile phone  1  receives and/or transmits control signals to a corresponding base station. As in the idle operation mode, the mobile phone  1  normally is carried inside a jacket or lying on a table for example, the antenna arrangement  5  is sufficiently distanced from the head of the user. Therefore, radiation into the head of the user is essentially prevented in the idle operation mode. To ensure the transmission of the control signals to the corresponding base station the omnidirectional radiation pattern  30  is assigned to the idle operation mode taking account of disadvantageous radiation situations as described above for example for the mobile phone  1  carried inside a jacket. 
     The directional radiation pattern  35  may be assigned to a first dedicated operation mode during which the mobile phone  1  is in an active telecommunication connection as for example an active call, whereby the mobile phone  1  normally is in an off-hook-state. In the case of a speech telecommunication connection, the first dedicated operation mode may also be called a conversation mode. In conversation mode, the user normally keeps the mobile phone  1  on an ear. Therefore, radiation into the head of the user should be prevented and the directional radiation pattern  35  is selected and assigned to the first dedicated operation mode. Thereby, the radiation should be directed away from the head of the user to minimize the power wasted in his head. 
     According to FIG. 1 with the first switch  45  closed and the second switch  50  open, the mobile phone  1  is in the idle operation mode. If the user wants to make a call or receives a call, the operation mode of the mobile phone  1  is changed from the idle operation mode to the first dedicated operation mode. Thereby, the baseband part  20  controls via the first control line  80  the first switch  45  in such a way, that the first switch  45  will be opened. The baseband part  20  via the second control line  85  controls the second switch  50  in such a way, that the second switch  50  will be closed. 
     Then in the first dedicated operation mode, the second antenna element  15  is connected to the radio frequency part  25 , whereby the first antenna element  10  is disconnected from the radio frequency part  25 . Thereby, the directional radiation pattern  35  is realized for the first dedicated operation mode. On this way, the antenna arrangement  5  is switched from the omnidirectional radiation pattern  30  to the directional radiation pattern  35 . If the telecommunication connection is finished, the operation mode of the mobile phone  1  changes from the first dedicated operation mode to the idle operation mode and the baseband part  20  controls the first switch  45  via the first control line  80  to be closed and the second switch  50  via the second control line  85  to be opened. Therefore, the first antenna element  10  will be reconnected to the radio frequency part  25  and the second antenna element  15  will be disconnected from the radio frequency part  25 . In this case, the antenna arrangement  5  is switched from the directional radiation pattern  35  to the omnidirectional radiation pattern  30 . 
     It is also possible to provide a third operation mode, for example a second dedicated operation mode during which the mobile phone is transmitting control signals in an active telecommunication connection as for example an active call, whereby the mobile phone  1  normally is in the off-hook-state. The transmission of the control signals from the mobile phone  1  to the corresponding base station in an active telecommunication connection is used to inform the corresponding base station about the signal quality. Thereby, the control signals are transmitted in fractions of times during the active telecommunication connection. A third radiation pattern may be assigned to the second dedicated operation mode. Thereby, the third radiation pattern may correspond to the first radiation pattern  30  and therefore to the omnidirectional radiation pattern of the first antenna element  10 . Therefore, it may be ensured, that the control signals, transmitted from the mobile phone  1  in an active telecommunication connection, reach the corresponding base station. On this way, in an active telecommunication connection of the mobile phone  1  the first dedicated operation mode changes to the second dedicated operation mode for fraction of times. The baseband part  20  thereby controls via the first control line  80  the first switch  45  and via the second control line  85  the second switch  50  to connect the first antenna element  10  to the radio frequency part  25  and to disconnect the second antenna element  15  from the radio frequency part  25  during the fractions of time when the second dedicated operation mode is active and to connect the second antenna element  15  to the radio frequency part  25  and to disconnect the first antenna element  10  from the radio frequency part  25  when the first dedicated operation mode is active. On this way, the omnidirectional radiation pattern  30  is selected in an active telecommunication connection only during the fractions of time for the transmission of the control signals, whereby the radiation into the head of the user is minimized in an active telecommunication connection. 
     To improve the signal quality for the transmission of the control signals in the idle operation mode or in the second dedicated operation mode, both antenna elements  10 ,  15  may be connected via the switches  45 ,  50  to the radio frequency part  25  during the idle operation mode and the second dedicated operation mode. Supposing that the two antenna elements  10 ,  15  are located close to each other, the connection of both antenna elements  10 ,  15  to the radio frequency part  25  via closed switches  45 ,  50  will result in a third radiation pattern  40  which is as superposition of the omnidirectional radiation pattern  30  and the directional radiation pattern  35 . The third radiation pattern in this case will be an omnidirectional radiation pattern with one privileged direction as shown in FIG.  3 . It is also possible, to assign the third radiation pattern  40  to the idle operation mode and the first radiation pattern  30  to the second dedicated operation mode. Therefore, the radiation into the head of the user caused by the second dedicated operation mode is kept at a minimum. 
     According to the example of FIG. 1, each antenna element  10 ,  15  provides exactly one radiation pattern  30 ,  35 . According to FIG. 2, a second example of a mobile phone  1  according to the invention is described whereby a third antenna element  95  is provided to realize the first and the second radiation pattern  30 ,  35 . In FIG. 2 the baseband part  20  is also connected to the radio frequency part  25 . The third antenna element  95  constitutes the antenna arrangement  5 . The third antenna element  95  is connectable via a third switch  55  either to a first antenna network  60  or to a second antenna network  65 . The first antenna network  60  and the second antenna network  65  are connected to the radio frequency part  25 . The radio frequency part  25 , the first antenna network  60 , the second antenna network  65  and the third switch  55  constitute a second radio frequency module  75 . The third switch  55  is controlled via a third control line  90  by the baseband part  20 . Depending on the connection of the third antenna element  95  to the first antenna network  60  or the second antenna network  65 , two different radiation patterns may be realized by the antenna arrangement  5 . If the third antenna element  95  is connected via the third switch  55  to the first antenna network  60 , the first radiation pattern  30  is realized as an omnidirectional radiation pattern. If the third antenna element  95  is connected via the third switch  55  to the second antenna network  65 , the second radiation pattern  35  is realized as a directional radiation pattern. Therefore, the same functionality as described according to FIG. 1 may be achieved with the mobile phone  1  according to FIG. 2 except the combination or superposition of the first radiation pattern  30  and the second radiation pattern  35 . In the idle operation mode and in the second dedicated operation mode the baseband part  20  controls the third switch  55  via the third control line  90  to connect the third antenna element  95  to the first antenna network  60  and therefore ensuring the first radiation pattern  30  of the antenna arrangement  5 . In the first dedicated operation mode, the baseband part  20  controls the third switch  55  via the third control line  90  to connect the third antenna element  95  to the second antenna network  65 , therefore ensuring the realization of the second radiation pattern  35  by the antenna arrangement  5 . 
     FIG. 4 shows an algorithm for the control of the radiation patterns and the operation modes in the baseband part  20  of the mobile phone  1 . The algorithm may be realized in the baseband part  20  by a program running on a processor of the baseband part  20 . The program starts when the baseband part  20  detects the change of the actual operation mode. This happens for example by user interaction via a keyboard not shown in FIG.  1  and FIG. 2 of the mobile phone  1 , whereby the keyboard is connected to the baseband part  20 . The user could for example dial a telephone number on the keyboard to initiate an active call and therefore an active telecommunication connection. The change between the first dedicated operation mode and the second dedicated operation mode may be initiated by the baseband part  20  itself according to system requirements which are known or programmed in the baseband part  20  of the mobile phone  1 . If a new operation mode has to be installed for the mobile phone  1 , the baseband part  20  has to determine this new operation mode. Therefore, at step  100  of the algorithm shown in FIG. 4, the baseband part  20  determines if the new operation mode is the idle operation mode for example after finishing an active telecommunication connection. If this is the case, the algorithm branches to step  105 , otherwise it branches to step  110 . At step  105  the baseband part  20  determines the radiation pattern required for the idle operation mode and controls the first switch  45  and the second switch  50  according to FIG. 1 or the third switch  55  according to FIG. 2 to realize the radiation pattern assigned to the idle operation mode at the antenna arrangement  5  as described above according to FIG.  1  and FIG.  2 . Afterwards the program is left. At step  110 , the baseband part  20  determines if the first dedicated operation mode is the new operation mode selected for example by a dialed telephone number on the keyboard of the mobile phone  1 . If this is the case, the program branches to step  115 , otherwise it branches to step  120 . At step  115  the baseband part  20  controls the first switch  45  and the second switch  50  according to FIG. 1 or the third switch  55  according to FIG. 2 to realize the radiation pattern assigned to the first dedicated operation mode at the antenna arrangement  5 . Afterwards, the program is left. At step  120 , the baseband part  20  determines if the second dedicated operation mode is selected. If this is the case, the program branches to step  125 , otherwise the program is left. At step  125 , the baseband part  20  controls the first switch  45  and the second switch  50  according to FIG. 1 or the third switch  55  according to FIG. 2 to realize the radiation pattern assigned to the second dedicated operation mode at the antenna arrangement  5 . Afterwards the program is left. 
     The assignment of radiation patterns to operation modes is described above only as an example and may be adapted according to the requirements of the telecommunications system in which the mobile phone  1  is used and according to appropriate health aspects. Every assignment of radiation patterns to operation modes is possible. 
     It is also possible to provide more than two antennas with different radiation patterns and to combine radiation patterns of more than two antennas for example by superposition. There could be a look-up table in the processor of the baseband part  20  in which each operation mode is assigned to a radiation pattern which has to be realized by the antenna arrangement  5 . 
     It would also be possible to provide antenna elements or at least one antenna element to realize exactly one radiation pattern and at least one antenna element to realize at least two different radiation patterns in one and the same antenna arrangement  5  connectable to the radio frequency part  25 . It may also be possible to provide at least one antenna element to realize more than two different radiation patterns. 
     The mobile phone  1  may be any terminal operating in any wireless system.