Abstract:
An apparatus and method for shielding an operator from electromagnetic fields emitted from an antenna in a portable communication device. A plurality of active shields are placed between the operator&#39;s earpiece and the antenna to dampen the effects of the electromagentic fields. The active shields are coupled to adjustment circuits which may include variable gain amplifiers and phase couplers to offset the antenna signal.

Description:
FIELD OF THE INVENTION 
     The present invention relates to shield devices and more particularly pertains to a shield device which may be used to protect a user from electromagnetic fields emitted by an antenna. 
     DESCRIPTION OF THE PRIOR ART 
     In recent years, as the number of wireless devices has grown, so has the concern about harm to the user from electromagnetic radiation. Although the level of electromagnetic radiation emitted by such devices is relatively low, the antenna which emits the radiation is close to the head, and there is also concern that the radiation can have a cumulative effect. 
     In the past, there have been some attempts to protect the users of wireless devices from such radiation, however, none of those approaches has been entirely satisfactory. 
     SUMMARY OF THE INVENTION 
     The present invention includes a method and apparatus for protecting an operator from electromagnetic fields emitted by an antenna. 
     The present invention further includes an apparatus having an antenna creating an electromagnetic field, and an active shield substantially canceling the effects of the electromagnetic field in a predetermined region. 
     The present invention further includes a communication apparatus having an antenna creating an electromagnetic field, and a plurality of active shields for canceling the effects of the electromagnetic field in a predetermined region. 
     The present invention further includes a communication apparatus having an antenna creating an electromagnetic field, and a means for canceling the effects of the electromagnetic field in a predetermined region. 
     The present invention further includes a method comprising generating an electromagnetic field from an antenna, and canceling the effects of the electromagnetic field in a predetermined region using an active shield. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view of a communication device such as a portable telephone with active shields; 
         FIG. 2  is a block diagram illustrating the elements of the first embodiment; and 
         FIG. 3  is a block diagram illustrating the elements of the second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a side view of the portable or personal communication apparatus  10  with only a few portions of such apparatus identified. (It should be noted that although the terms personal communication apparatus, wireless communication device, wireless device, wireless telephone are used, these terms are interchangeable and mean any portable device that emits electromagnetic fields, particularly those that are frequently place near a user&#39;s head and/or person.) An antenna  12  is shown extending upwardly from the apparatus  10 . Active shields or radiators  14   a – 14   c  are shown arranged between the antenna  12  and/or the RF circuitry of the device (not shown) and the operator&#39;s ear piece  10   a . Active shields  14   a – 14   c  are radiating devices that substantially cancel or reduce the electromagnetic field(s) from the device  10  and/or the antenna  12  in a predetermined area. In this case the predetermined area is the operator&#39;s head which is substantially located near the radiators  14   a – 14   c . The number of active shields may range anywhere from one to five or greater depending on the requirements of the communication apparatus  10 . The active shields  14   a – 14   c  create a near field which is opposite to that produced by the antenna  12  and the device  10 . 
       FIG. 2  illustrates a block diagram of a first embodiment. Antenna  12  is connected to the RF circuitry section of the device (not shown in  FIG. 2 ) which contains a controller (e.g., microprocessor) through line  16 . The controller may be the main controller of the communication device  10  or an extra controller. Located between antenna  12  and the RF circuitry section of the device is a coupler  20 . Coupler  20  diverts a small portion of the signal (approximately 10%) traveling from the circuit board to the antenna. In one embodiment, coupler  20  is connected to active shields (or radiators)  14   a – 14   c . Located between coupler  20  and active shields  14   a – 14   c  are adjustment circuits  22   a – 22   c . Adjustment circuits  22   a – 22   c  each include variable phase shifters  24   a – 24   c  and variable gain amplifiers  26   a – 26   c . Variable phase shifters  24   a – 24   c  substantially adjust the phase of the signal. As a result, the electromagnetic field strength produced by the antenna which may be absorbed by a user is reduced in effect by the active shields  14   a – 14   c  in the region around the earpiece  10   a.    
       FIG. 3  illustrates a block diagram of a second embodiment. Antenna  12  is connected through line  16  to circuit board  42  and controller  40  (e.g., a microprocessor). Coupler  20  is connected to active shields  36   a  and  36   b . Between coupler  20  and active shields  36   a – 36   b  are located adjustment circuits  30   a  and  30   b . Adjustment circuits  30   a  and  30   b  include variable phase shifters  32   a – 32   b  and variable gain amplifiers  34   a – 34   b . The second embodiment further includes sensors  38   a  and  38   b  which are located near active shields  36   a  and  36   b , respectively. The sensors measure the electromagnetic field strength in the environment of the shields  36   a – 36   b  and send feedback signals along lines  46   a  and  46   b  to the controller  40 . (The controller  40  may be the main processor for the communication device  10  or it may be a dedicated processor for controlling the active shields  36   a – 36   b ). Controller  40  is coupled to the variable phase shifters  32   a – 32   b  through lines  44   a  and  48   a . Controller  40  is coupled to the variable gain amplifiers  34   a  and  34   b  through lines  44   b  and  48   b . Controller  40  adjusts the variable phase shifters and variable gain amplifiers in response to the readings from the sensors  38   a  and  38   b . Although the second embodiment discloses each active shield with a sensor, in an alternative embodiment there may be one feedback circuit monitoring and controlling a plurality of active shields. 
     It is understood that the present invention has been described hereinabove by way of example and by preferred embodiments and not as a limitation on the invention. It is to be realized that various changes, alterations, rearrangements and modifications can be made by those skilled in the art to which it relates without departing from the spirit and the scope of the present invention.