Abstract:
An apparatus for reducing hearing aid radio frequency (RF) interference including a directional multi-band and/or single band antenna for use with PWDs such as digital cellphones is disclosed. The apparatus greatly reduces or eliminates the audio noise induced in hearing aids by the PWDs and allows operation of a hearing aid during PWD operation. In operation, the apparatus may be provided on the PWD side away from the user&#39;s head. The apparatus may be integrated into the PWB during its manufacture or provided as an after market assembly for a PWD that has a port for connection of an external antenna. The apparatus provides for improved front-to-back ratio as compared to antennas currently in use on PWD&#39;s, and therefore also reduces SAR (specific absorption rate), the level of RF energy received into the head by a PWD.

Description:
RELATED APPLICATION  
       [0001]    This application claims the benefit of priority pursuant to 35 U.S.C. 119 of Provisional Patent Application Ser. No. 60/357,162, filed Feb. 13, 2002, which entire application is incorporated by reference herein. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a device for reducing rf-induced audio noise generated within a hearing aid of a user of an associated portable wireless device (PWD). Additionally, the present invention relates to a device for reducing the specific absorption rate (SAR) of the associated PWD during operation.  
           [0004]    2. Description of the Related Art  
           [0005]    In-ear hearing aid use may be limited during operation of certain types of PWDs due to rf-induced audio noise generated within the hearing aid while in operation near a transmitting PWD. The noise is induced during PWD transmission as an electromagnetic field from the PWD induces currents in the circuitry of the hearing aid. The electromagnetic field from the PWD causes components within the hearing aid to generate audio noise, the noise being particularly related to the frequencies of the digital portion of the PWD. Solutions to this problem having included: moving the PWD away from the ear/head by providing a 2-way audio link between the remote PWD and the ear. Two types of such audio links are a) a “docking station” for the PWD that has microphone/speaker, and b) a “T-coil” that couples audio from the cellphone into the hearing aid. Another solution to the problem has been a wired connection of a microphone/speaker unit from the PWD to the vicinity of the user&#39;s head. The microphone/speaker unit requires insertion of a small “speaker” into the user&#39;s ear, which may not be possible for the user of an in-ear hearing aid. Further, the wire(s) may allow RF to flow from the PWD&#39;s antenna system into the microphone/speaker unit and subsequently cause similar audio noise as if the PWD were near the head.  
           [0006]    A solution to this hearing aid noise/PWD problem that permits the hearing impaired to use a conventional PWD, particularly a digital cellphone, in the normal manner without an accessory speaker/microphone device would be desirable.  
           [0007]    Current digital cellphones are designed for operation on multiple frequency bands, for instance the 824-894 and 1850-1990 MHz bands in the US. Band selection is done without user input, and is determined by band availability in a particular geographical area. Both US frequency bands provide digital service, therefore a solution to the hearing aid noise problem caused by digital cellphones must be compatible with each frequency bands used by the cellphone.  
           [0008]    SAR (specific absorption rate) for users of PWDs is a matter of increasing concern. RF radiation to the user&#39;s head results from the free-space generally omnidirectional radiation pattern of typical current PWD antennae. When PWDs equipped with such an antenna are placed near the user&#39;s head, the antenna radiation pattern is no longer omnidirectional as radiation in a large segment of the azimuth around the user is blocked by the absorption/reflection of the head. An antenna system for PWDs that greatly reduces radiation to the body and redirects it in a useful direction is also desirable.  
           [0009]    [0009]FIG. 1 illustrates a prior art dual-band PIFA antenna  30 , which is located on the rear of a personal wireless device (“PWD”)  32 , and electrically connected to ground plane  34  at one end and capacitively coupled to ground plane  34  at another end. PWD  32  further includes a battery pack  35  positioned away from antenna  30 . In normal operation, PWD  32  is oriented in an upright manner so that end  38  is generally above end  40 . Ground plane  36  is provided by the ground traces of the printed wiring board (PWB) of PWD  32 . The portion of antenna  30  indicated by numeral  42  resonates over a higher frequency band, while the entire portion  42 ,  44  of antenna  30  resonates over a lower frequency band. PIFA antenna  30  is grounded at its upper end at location indicated as numeral  46  to ground plane  34 . PIFA antenna  30  is capacitively coupled at pad  48  in a direction away from upper end  38  of PWD. This type of antenna provides some reduction in SAR, but cannot eliminate hearing aid noise from a digital PWD.  
           [0010]    Referring to FIG. 2, a perspective view of a prior art PWD  32  (in the form of a cellphone) used in the vicinity of a hearing aid  60  is illustrated. Cellphone  32  has a speaker on the keyboard surface near the top of the phone, which is normally aligned with the center of the user&#39;s ear  62  during use. Hearing aid  60  may be any type, including in-ear and behind-ear variations. Hearing aid  60  has an amplified audio output port  4 , which is inserted into the ear canal of the ear  62 . During operation, an electromagnetic field  64  is generated around cellphone  32  by omnidirectional antenna  66 . In operation, electromagnetic field  64  illuminates the hearing aid  60 , user&#39;s ear  62 , and the user&#39;s head. RF noise is induced in the hearing aid by the field  64 , resulting in excessive audio noise being presented to the user.  
         SUMMARY OF THE INVENTION  
         [0011]    The device of the present invention greatly reduces radiation directed toward a user&#39;s head and hearing aid during device operation. As a result, the device promotes a reduction or elimination of hearing aid noise and SAR. Other benefits include longer transmit/receive range, lower transmit power, and longer battery life.  
           [0012]    A device according to the present invention may include a PWD implemented for operation over single or multiple frequency-bands. An antenna may be incorporated within a PWD at the time of manufacture, or may be provided as an accessory or after market item to be added to existing PWD&#39;s having an external antenna port. The latter feature is particularly useful, in that existing PWD&#39;s can be retrofitted to achieve the benefits of the antenna of the present invention, including elimination of hearing aid noise and very low SAR. The antenna of the present invention is suitable for high-volume, low cost manufacturing. The antenna/PWD combination, whether an aftermarket or original equipment item, may be placed in a leather or plastic case, such that the antenna side of the PWD is facing away from the body. This provides a further advantage with respect to SAR, when the PWD is stored via a belt clip when in receive-only mode.  
           [0013]    Other objects of the present invention include:  
           [0014]    the elimination (or substantial reduction) of audio noise in hearing aids caused by close proximity to transmitting PWDs, particularly digital cellphones;  
           [0015]    the elimination (or substantial reduction) of audio noise in hearing aids caused by close proximity to transmitting PWDs, particularly PWD&#39;s operating in one or more frequency bands, enabling use of hearing aids in close proximity to such PWDs;  
           [0016]    the reduction in SAR due to operation of a single or multi-band PWD near the user&#39;s head;  
           [0017]    the provision of an antenna suitable for integration within or upon a PWD;  
           [0018]    the provision of an antenna having wide bandwidth in one or more frequency bands;  
           [0019]    the provision of an antenna having one or more active elements and one or more passive elements, each resonant on one or more frequency bands;  
           [0020]    the provision of an antenna which radiates RF energy from a PWD preferentially away from a user thereof;  
           [0021]    the provision of an antenna promoting increased PWD battery life by reducing commanded RF power;  
           [0022]    the provision of an antenna having a reduction in the amount of RF energy beingabsorbed by a user&#39;s hand during operation; and  
           [0023]    the provision of an antenna with the one or more active element(s) connected to a PWD&#39;s transmit/receive port.  
           [0024]    These and further objects of the present invention will become apparent to those skilled in the art with reference to the accompanying drawings and detailed description of preferred embodiments, wherein like numerals refer to like parts throughout. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    [0025]FIG. 1 illustrates a prior art wireless communications device having a known PIFA-type antenna assembly.  
         [0026]    [0026]FIG. 2 depicts operation of a wireless communications device, such as a cellular phone, in proximity to a hearing aid and user.  
         [0027]    [0027]FIG. 3 is a perspective view of a first embodiment of a device according to the present invention.  
         [0028]    [0028]FIG. 4 is a top plan view of the device embodiment of FIG. 3.  
         [0029]    [0029]FIG. 5 is a side view of the device embodiment of FIGS. 3 and 4.  
         [0030]    [0030]FIG. 6 is a perspective partial view of another embodiment of the present invention.  
         [0031]    [0031]FIG. 7 is a perspective view of yet another embodiment of a device according to the present invention.  
         [0032]    [0032]FIG. 8 is a perspective partial view of another embodiment of the present invention.  
         [0033]    [0033]FIG. 9 is a perspective view of yet another embodiment of a device according to the present invention.  
         [0034]    [0034]FIG. 10 is a top plan view of the device embodiment of a single-band embodiment of the present invention.  
         [0035]    [0035]FIG. 11 is a side view of the device embodiment of FIG. 10.  
         [0036]    [0036]FIG. 12 is yet another embodiment of an antenna according to the present invention.  
         [0037]    [0037]FIG. 13 is yet another embodiment of an antenna according to the present invention.  
         [0038]    [0038]FIG. 14 is yet another embodiment of an antenna according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0039]    Referring to FIGS. 3 through 5, an antenna device according to one embodiment of the present invention is indicated as numeral  70 . Device  70  comprises an external assembly which may be provided as an aftermarket device to improve PWD  32  performance. Device  70  has an RF port  72  which connects into an external antenna port  74  of the PWD  32 . In alternative embodiments, device  70  may be connected via a coaxial cable or other type of transmission line.  
         [0040]    Device  70  includes a conductor element  76  and a pair of configured conductive radiating elements  78 ,  80 . Element  76  may be a planar conductive element, or may be configured to have some curvature or other shape. Element  76  preferably has an electrical length in the range of 0.3 to 0.8 wavelength for a frequency within the band of operation. Element  76  may be formed as a metal part or may be a plating or conductive layer disposed upon a support element, such as a housing, etc. Further, at least a portion of element  76  may be provided by the ground traces of the printed wiring board of a PWD within or upon which antenna  70  is located.  
         [0041]    Each of the conductors  78 ,  80  has a free end and is conductively connected to element  76  at an opposite end as indicated by numeral  82  in FIGS. 4 and 5. A feedpoint  84 , having a desired impedance, is defined along conductor  78 . A short conductor  86  is attached at feedpoint  84 . Conductor  86  is connected to the center conductor of a coaxial line  90 . An outer shield of line  90  connects to conductor element  76  at location  92 . In alternative embodiments, coax line  90  may be replaced by a microstrip or other type of transmission line.  
         [0042]    In the embodiment of FIGS.  3 - 5 , transmission line  90  connects to RF connector  72 , which is selected to match the connector used for the external antenna port  74  on WCD  32 . Although connector  72  is shown exiting the back side of element  76 , it may take any other route as required to plug into the WCD&#39;s external antenna port. Antenna device  70  may also be incorporated into a WCD at the time of manufacture, in which case transmission line  90  would directly connect to the RF input/output point of the WCD&#39;s transceiver.  
         [0043]    Elements  78 ,  80  are designed to resonant over one or more frequency bands. As an example, conductor  78 , which is a fed element, may be resonant at a higher frequency band, with inductor  100  and conductor  102  acting as a “trap” or electrical stop for said higher frequency band. The term “LC trap” as used herein is defined to mean either a inductor/capacitance trap or an inductive trap. Coil  100  and conductor  16  may be selected so as to cause the combination of elements  78 ,  100 , and  102  to resonate at a lower frequency band, thus providing a dual-band element having one feedpoint.  
         [0044]    Element  80 , which is not directly connected to feedline  90 , may have its length adjusted to resonate over the same or nearly the same frequency bands as  78 . Inductor  104  and conductor  106  may be selected to act as a “trap” or stop for the said higher frequency band, and the combination of elements  80 ,  104 , and  106  may be selected to resonate at a lower frequency band, which may be the same or nearly the same as that of elements  78 ,  100 , and  102 . Again, a greater bandwidth in a lower frequency band is attained with two adjacent elements ( 78 ,  100 ,  102 ) and ( 00 ,  104 ,  106 ) than with a single element. The higher frequency band may be 1850-1990 MHz, and the lower frequency band may be 824-894 MHz. A range and preferred values of dimensions for these frequency bands are as follows;  
                                                             Dimension   Range   Preferred Dimension                                W1   0.25-1.525   in.   0.75   in.       W2   1-6   in.   1.6   in.       H1   0.3-2   in.   0.75   in.       H2   0.001-0.5   in.   0.02   in.       L1   1.5-4   in.   2.75   in.       L2   0.5-4   in.   1   in.       L3   4-8   in.   5.25   in.                  
 
         [0045]    Conductors  78 ,  80  may have any cross section, including round and rectangular. One preferred cross section is 0.05 in. diameter round wire.  
         [0046]    Conductor  76  length, L 3 , is greater than the length of elements  78  and  80 . Conductor  76  may be defined by a plurality of conductive trace elements on a dielectric board, such as a printed wiring board. Through additional experimentation by those skilled in the relevant arts, the traces may assume a variety of configurations.  
         [0047]    Element  78  and  80  are oriented upon conductor  76  so that the free ends of the elements  78 ,  80  are above the connection ends  82  during device operation. In other words, during device operation, elements  78 ,  80  are upwardly directed. In a typical operation of PWD  32 , elements  78 ,  80  would be more or less perpendicular to the floor or ground surface upon which the operator is positioned. For an embodiment of antenna  70  which is integrated within a PWD  32 , elements  78 ,  80  are secured at first ends to conductor  76  and have free ends extending in a direction toward the top of PWD  32 .  
         [0048]    [0048]FIG. 6 shows another embodiment of the element  78  and trap inductor  100 . Inductor  100  is a wire element having windings which may be uniformly spaced or which may be non-uniformly spaced. In this particular embodiment, inductor windings  100  are more closely spaced proximate to element  78  than proximate to the conductor element  76 , i.e., the “pitch” of the wire winding varies across its length. The resonant frequency of the combination  78  and  100  may be adjusted by varying height “h”.  
         [0049]    [0049]FIG. 7 illustrates features of another embodiment of an antenna device  70  according to the present invention. Radiating elements  110 ,  112  are coupled at a position relative far away from the top  38  of the PWD  32 , and the open ends  114  of elements  110 ,  112  are in a direction toward the top of the PWD  32 , e.g. during normal operation open ends  114  of elements  110 ,  112  are upwardly directed (e.g., away from a floor surface).  
         [0050]    The ground plane required for the antenna system  70  may be provided separately from that within the PWD  32 , by conductive segments  120 ,  122  and  124 . Segments  120 ,  122  may be capacitively coupled within the overlap region “O”. Segments  124 ,  120  are electronically connected, and segment  124  may slide in and out relative to  120  to reduce size, when the PWD  32  is not in use. Segment  124  may be manually retracted as during PWD  32  operation. In alternative embodiments, segment  124  may be automatically extended during operation, such as via a small solenoid, motor and gearing, etc.  
         [0051]    Referring to FIG. 8, an alternative embodiment of a driven element  136  of the antenna  70  of the present invention is shown. In this embodiment, PWB (printed wiring board) technology is utilized to facilitate close dimensional tolerances for the antenna. A dielectric printed wiring board  134 , which may have a dielectric constant in the range 2-30, is used to support the element conductors  131 ,  132 ,  135 . The feed point is indicated as numeral  84 . Connection point to coax line  90  is indicated as numeral  133 . Meander line inductor  132  corresponds to inductor  100  from FIGS.  3 - 5 . Although meander line inductor  132  is shown as a meander line on one surface of the PWB  134 , one skilled in the art would recognize that it could also be implemented as traces occupying both sides of PWB  134 , with plated-through holes (“vias”) connected the line segments. Although the driven elements  131 ,  132 ,  135  alone are depicted in FIG. 8, the same construction may be used to fabricate the non-driven element as well.  
         [0052]    Referring to FIG. 9, another embodiment of the antenna  70  of the present invention is shown in perspective view. The various conductive elements consisting of leg elements  200  and  204  (which are generally perpendicular relative to conductive element  206 ), elements  208  and  210  (which are generally parallel to conductive element  206 ), feed conductor  220 , and crossbar conductor  222  all of which may be formed as a single stamped metal part. The bottom ends of legs  200 ,  202  are inserted into slots  224  in element  206 , and may be soldered or otherwise captured mechanically.  
         [0053]    Element leg  204  and element  210  may preferably be wider than corresponding leg element  200  and element  208 . Inductors  230 ,  232  may have extensions  240  leading to an additional turn or turns  242 ,  244 . This construction of the inductor  230 ,  232  eliminates a separate conductor plate  102 ,  106  at the end of the coils,  100 ,  104  as shown in FIG. 4. Elements  28  and/or  210  may be supported by dielectric post  250  and a dielectric clamp (not shown) at location  252 , respectively.  
         [0054]    Referring to FIGS. 10 and 11, yet another embodiment of a device according to the present invention is illustrated. Antenna  70  in this embodiment is a single band antenna assembly. In comparison to the dual-band embodiment of FIGS.  3 - 5 , this embodiment of antenna  70  does not require the trap tuning elements, e.g.,elements  100 ,  102 ,  104 , and  106  of FIGS. 4 and 5.  
         [0055]    [0055]FIG. 12 shows a single band embodiment of the antenna  300  of the present invention. Antenna  300  is located near the top  38  of PWD  32 . The radiating element has three segments  302 ,  304 ,  306 . A microstrip feed section  310  is shown connected to the rf input/output port of the PWD at  312 . A ground plane  320 , separate from the internal ground plane of PWD  32 , is used. Segment  306  is electrically connected to  320  at location  330 . Ground plane  320  may extend beyond the top of PWD  32 , and it may be a sliding type as shown in FIG. 7. Ground plane  320  may be provided, at least in part, by the ground traces of the printed wiring board of PWD  32 , particularly in an application where antenna  300  is integrated within the PWD  32 .  
         [0056]    Antenna  300  may function as a single band antenna suitable for operation over the range of 1710-1990 MHz, for example. In one embodiment the dimensions: for ground plane  320  are 1.41 in. by 2.72 in; for segment  306  are 0.57 in. (width) by 0.5 in. (height); and for segment  302  are 0.57 in (width) by 1.46 in. (length). Thickness of all conductors may be in the range of 0.001-0.10 inch, with 0.020 being a preferred thickness. The length of ground plane  320  extending beyond end  38  may be in the range of 0 to 1 inch, with 0.7 in being a preferred dimension. In an embodiment of antenna  300  being incorporated within a PWD  32 , ground plane  320  may not extend outside of the PWD  32  housing.  
         [0057]    Referring to FIG. 13, another antenna embodiment  70  with a configured ground plane conductor  76  is shown. The length L 1  of conductor  76  of FIG. 5 is replaced by the combination of L 1 ′, L 1 ″ and L 1 ′″. Generally, this combination of segments will have a length equal to or somewhat longer than L 1  of FIG. 5, depending on the ratio of L 1 ″ to L 1 ′″. The function of this feature is to reduce the overall length of conductor  76  from FIG. 5.  
         [0058]    Referring to FIG. 14, yet another antenna embodiment  70  with a differently configured ground plane conductor  76  is shown. Here conductor  341  and inductor  342  are closely spaced from element  76  and electrically connected to element  76  at location  343 . Again, the purpose of this embodiment is to reduce the length of  76 .  
         [0059]    The above described embodiments of the invention are merely descriptive of its principles and are not to be considered limiting. Further modifications of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention.