Abstract:
Hearing apparatuses with transmission facilities for the wireless transmission are to be miniaturized further. A transmission facility for a hearing apparatus and in particular a hearing device with an oscillating circuit including a capacitor and a coil as well as an electrical line is provided in or to the oscillating circuit, with the electrical line having a shielding. The electrical line includes a film conductor with a signal line and shielding line, the shielding capacitance of which is connected in parallel to the capacitor of the oscillating circuit. The shielding capacitance can be used together with the capacitance of the capacitor in a targeted fashion as an oscillating circuit capacitance. In this way, the parasitic shielding capacitance is used as a wanted capacitance. As the shielding capacitance of the film conductor is only subjected to minimal fluctuations, it only requires a small tuning capacitor for tuning the oscillating circuit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of German application No. 10 2007 042 592.0 filed Sep. 7, 2007, which is incorporated by reference herein in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a transmission facility for a hearing apparatus with an oscillating circuit including a capacitor and a coil as well as an electrical line in or to the oscillating circuit, with the electrical line comprising a shielding. The present invention also relates to an electric coil with a wire winding to be shielded. In particular, the present invention relates to a hearing apparatus with a coil and/or transmission facility of this type for the wireless reception and/or emission of signals. The term “hearing apparatus” is understood here to mean in particular a hearing device but also any other device for outputting sound which can be worn on or in the ear, like for instance a headset, earphones and suchlike. 
       BACKGROUND OF THE INVENTION 
       [0003]    Hearing devices are wearable hearing apparatuses which are used to assist the hard-of-hearing. In order to accommodate numerous individual requirements, various types of hearing devices are available such as behind-the-ear (BTE) hearing devices, hearing device with an external receiver (RIC: receiver in the canal) and in-the-ear (ITE) hearing devices, for example also concha hearing devices or completely-in-the-canal (ITE, CIC) hearing devices. The hearing devices listed as examples are worn on the outer ear or in the auditory canal. Bone conduction hearing aids, implantable or vibrotactile hearing aids are also available on the market. The damaged hearing is thus stimulated either mechanically or electrically. 
         [0004]    The key components of hearing devices are principally an input converter, an amplifier and an output converter. The input converter is normally a receiving transducer e.g. a microphone and/or an electromagnetic receiver, e.g. an induction coil. The output converter is most frequently realized as an electroacoustic converter e.g. a miniature loudspeaker, or as an electromechanical converter e.g. a bone conduction hearing aid. The amplifier is usually integrated into a signal processing unit. This basic configuration is illustrated in  FIG. 1  using the example of a behind-the-ear hearing device. One or a plurality of microphones  2  for recording ambient sound are built into a hearing device housing  1  to be worn behind the ear. A signal processing unit  3  which is also integrated into the hearing device housing  1  processes and amplifies the microphone signals. The output signal for the signal processing unit  3  is transmitted to a loudspeaker or receiver  4 , which outputs an acoustic signal. Sound is transmitted through a sound tube, which is affixed in the auditory canal by means of an otoplastic, to the device wearer&#39;s eardrum. Power for the hearing device and in particular for the signal processing unit  3  is supplied by means of a battery  5  which is also integrated in the hearing device housing  1 . 
         [0005]    During the magnetic transmission of data (control data, programming data, audio data), E-field influences are unwanted since they may destructively overlay one another with the wanted signal from the magnetic field. The magnetic antennae (coil arrangements with and without ferrite core) as well as in particular their supply lines are affected by E-field injections. Conventional shields can generally not be deployed for use in miniaturized hearing devices for reasons of space and cost. 
         [0006]    It is known to effectively shield E-fields with electrically conductive casings. The best known example of this is coaxial lines. 
         [0007]    The patent application U.S. Pat. No. 6,940,466 B2 also discloses the shielding of ferrite cores with shielding films. This type of shielding of an antenna is associated with serious disadvantages particularly for hearing devices. The film surface namely has a high capacitive coupling to the windings arranged therebelow. The higher the working frequency, the lower the resistance of the alternating current resistor between the windings and the shielding film. This results in excessively high losses during emission and in a deterioration in the sensitivity during reception. If the capacitive coupling is to be kept to a minimum, the insulation must be selected to be very thick. As a result, the component becomes significantly larger and can no longer be used for miniaturized hearing devices. 
       SUMMARY OF THE INVENTION 
       [0008]    The object of the present invention thus consists in proposing a transmission facility for a hearing apparatus with a shielded antenna feed line, whereby the installation space is to be reduced. In particular, a shielded antenna coil with a reduced installation space requirement is also to be provided. 
         [0009]    This object is achieved in accordance with the invention by a transmission facility for a hearing apparatus with an oscillating circuit including a capacitor and a coil as well as an electrical supply line in or to the oscillating circuit, with the electrical line having a shielding and with the electrical line having a film conductor with a signal line and a shielding line, the shielding capacitance being connected in parallel to the capacitor and the shielding capacitance being used together with the capacitance of the capacitor in a targeted fashion as the oscillating circuit capacitance. 
         [0010]    Provision is also made in accordance with the invention for an electrical coil with a wire winding including a first and a second wire end, with the wire winding being formed in one layer in an axial direction, starting with the first wire end, and a wire section on the second wire end being guided as a shield directly across the wire winding opposite to the axial direction. 
         [0011]    By using the shielding capacitance, which is actually a parasitic capacitance, it is advantageously possible to reduce the capacitance of the necessary oscillating circuit capacitor and in this way to save on the installation space. Furthermore, the use of the film conductor is advantageous in that its capacitance can be very precisely determined, as a result of which the necessary tolerances can be reduced. As a result, the necessary tuning range is in turn reduced and a so-called “on-chip tuning” is possible, during which on-chip tuning capacitors are connected depending on requirements. The tuning capacitor required for the oscillating circuit of the transmission facility can then be integrated completely into a semiconductor chip. 
         [0012]    The coil of the oscillating circuit preferably has a self-shielding formed itself by its winding wire. In particular, the self-shielding is formed like in the above-described electrical coil such that a wire end is guided as a shield directly across the wire winding opposite to the axial direction of the winding. Voluminous shielding components can be avoided in this way. 
         [0013]    According to one embodiment, one of the signal lines and the shielding line can be short-circuited at one end of the electrical line of the oscillating circuit. The shielding is thus applied to the potential of the one line end and no special shielding potential needs to be guided at the electrical line. 
         [0014]    Furthermore, the film conductor can comprise a conductor layer, which can be laterally discontinued and can thus be used both for the signal line as well as for the shielding line. Alternatively or in addition, the film conductor can comprise several conductor layers for the signal line and shielding line. As a result, the desired shielding effects can be achieved in parallel to or transverse to the backing film of the film conductor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present invention is described in more detail with reference to the appended drawings, in which; 
           [0016]      FIG. 1  shows the basic design of a hearing device according to the prior art; 
           [0017]      FIG. 2  shows the supply line of a coil with a film conductor according to the present invention; 
           [0018]      FIG. 3  shows a cross-section of the supply line in  FIG. 2 ; 
           [0019]      FIG. 4  shows a first alternative of a supply line; 
           [0020]      FIG. 5  shows a second alterative of a supply line; 
           [0021]      FIG. 6  shows a third alternative of a supply line; 
           [0022]      FIG. 7  shows a longitudinal section through a multi-layer antenna coil; 
           [0023]      FIG. 8  shows a longitudinal section through a one-layer antenna coil; 
           [0024]      FIG. 9  shows a circuit diagram of an inventive transmission facility, and 
           [0025]      FIG. 10  shows a circuit diagram of an alternative transmission facility. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    The exemplary embodiments illustrated in more detail below represent preferred embodiments of the present invention. 
         [0027]      FIG. 2  symbolically shows part of an antenna coil  10  wound in one layer. The first winding end  11  represents the signal line input sig. The second winding end  12 , which is simultaneously used for shielding purposes (cf.  FIG. 8 ) is placed on a shielding and/or reference potential. The two winding ends  1   1  and  12  are connected to a film conductor  13 . The first winding end  11  is concretely connected to a signal line  14  of the film conductor  13  and the second winding end  12  is connected to a shielding line  15 . The instance is thus shown here in which the antenna with a terminal is connected to a reference potential (ground or supply voltage) and a shielding layer and/or the shielding line  15  of the film conductor  13  is used for this terminal. 
         [0028]      FIG. 3  shows a section III/III through the film conductor  14  in  FIG. 2 . Accordingly, a conductor layer is located on a backing film  16 , said conductor layer being laterally discontinued twice. As a result, three lines result: in the center the signal line  14  and left and right thereof the shielding line  15 , which are connected to one another at the end of the film conductor  13 . 
         [0029]      FIG. 4  shows an alternative film conductor  13 . It has a signal line  14  running in the longitudinal direction on the one flat side, like the film conductor in  FIG. 3 . A metal coating is likewise located on the other flat side of the backing film  16  (in  FIG. 4  the underside), which is used as a shielding line  17 . The backing film  16  is located here between the signal line  14  and the shielding line  17 . 
         [0030]    A further exemplary embodiment of a film conductor with a shielding is reproduced in  FIG. 5 . This design represents a combination of the conductor superstructures of  FIGS. 3 and 4 . The signal line  14  and the shielding line  15  are arranged on the topside of the backing film  16 , as in the example in  FIG. 3 , whereas the additional shielding line  17  is arranged on the lower side. 
         [0031]      FIG. 6  represents one development of the film conductor  13  in  FIG. 5 . In addition to the structure in  FIG. 5 , an additional backing film  16 ′ is arranged over the signal line  14  and the shielding lines  15  and a further additional shielding line  17 ′ is also arranged again thereover. While  FIG. 3  thus shows a two-layer design (backing and conductor layer) of the film conductor  13 ,  FIGS. 4 and 5  show a three-layered design and  FIG. 6  shows a five-layered design of the film conductor  13 . A multi-layered film conductor  13  of this type with an integrated shielding layer can thus realize a space-saving supply line for an inductor antenna. 
         [0032]    The shielding of the supply line is of critical importance to the design of critical hearing devices with magnetic data transmission. The selection of the supply line length and the type of positioning of the supply line must as a result be being determined in a considerably less strict fashion. This is particularly meaningful for in-the-ear hearing devices with individually manufactured housing shells. In the hearing devices, parallel oscillating circuits are mostly used advantageously, which due to the excessive voltage in the vicinity of the resonance has a large reception sensitivity and a high frequency selectivity. The shielding achieves an increased signal-to-noise ratio and a suppression of interference signals, which do not lie directly in the vicinity of the working frequency. 
         [0033]    The type of supply line shielding particularly effects the antennae, which form part of a parallel oscillating circuit. The construction-specific and mostly not insignificant supply line capacitance may form part of the oscillating circuit capacitance. When using film conductors (cf.  FIGS. 3 and 6 ), the capacitance distribution is very defined and the dielectric losses are very minimal. The capacitance of the shielding can thus be used as a complete part of the effective capacitance. As a result of the clear definability of the shielding capacitance, parallel oscillating circuits can be advantageously developed. This is very difficult with twisted lines, which are usually used in hearing devices, since their capacitance distribution and shielding effect fluctuate significantly. Consequently, a relatively high tuning range in respect of the capacitances is necessary with the known hearing devices. This is generally not possible on a chip (on-chip tuning). Since the inventive use of a film conductor with a defined shielding capacitance introduces fewer capacitance fluctuations, no natural capacitors have to be provided for the tuning of the oscillating circuit, but instead the small capacitors on a chip can be used in a known manner for the tuning. 
         [0034]    A film shielding, as is known from the prior art (U.S. Pat. No. 6,940,466 B2), is not used in the present case for the antenna as a result of the above-mentioned disadvantages. Instead, the antenna coil is structured in a self-shielded fashion, as is shown in  FIG. 7 and 8 .  FIG. 7  shows a multi-layered wound coil  10 ′ with the winding ends  11  and  12  on one side of the coil  10 ′. An inner winding layer  18  is wound around a cylindrical ferrite core  20  in a first axial direction  19 . An outer winding layer  21  is by contrast wound around the windings arranged below in a second axial direction  22  which is opposite to the first axial direction  19 . With this multi-layered wound coil  10 ′, the wire end  12  of the outer winding layer  21  is connected to the reference potential ref. As a result, the outer lying windings only have a minimal potential difference compared with the reference ref and are accordingly insensitive compared with the acting E-fields. Multi-layered wound coils are however only suited to low working frequencies below approximately 2 MHz, due to the low natural resonance.  FIG. 8  shows by contrast a figurative longitudinal section through a one-layer wound antenna coil  10 . The wire winding with its two winding ends  11  and  12  is wound over the ferrite core  20  in the first axial direction  19 . One part of the winding wire in front of the second end  12  is used as a feedback wire  23 . To be able to better identify this,  FIG. 8  illustrates a cross-sectional view, which is nevertheless shown with a solid line. This feedback wire is guided and wound over the winding layer in the opposite second axial direction  22  and is then connected to the reference potential ref. The feedback level  23  thus lies on reference potential and renders the winding layer positioned therebelow insensitive to the acting E-fields. Such coils are also very well suited to high frequency working frequencies up to approximately 20 MHz. 
         [0035]      FIG. 9  shows a circuit diagram of an inventive transmission facility. An oscillating circuit consisting of an antenna coil  10  and/or L res  is supplied using a main resonance capacitor C res  by a chip  24 , which lies on its part on ground GND and is powered by a supply voltage V+. For the oscillating circuit power, the chip  24  makes the signal potentials Sig+ and Sig− available. The potential Sig+is guided directly to the coil  10  via the signal line  14  of the film conductor  13 . The other potential Sig− is applied to the coil  10  via the signal line  14  of a film conductor  13 . This circuit plan of the coil  10  represents an equivalent circuit diagram for the coils of  FIGS. 7 and 8 . 
         [0036]    The shielding lines  15  of the film conductor  14  are placed in this example on a special reference potential V ref , which is likewise provided by the chip  24 . This reference potential V ref  is independent of the signal potentials Sig+ and Sig−, which produces a symmetrical circuit of the inductive antenna. 
         [0037]    The shield of the film conductor  13  leads to an additional capacitor C guard . This, due to the nature of the film conductor, very defined shielding capacitance C guard  is parallel to the capacitance C res , so that the oscillating circuit capacitance is formed roughly from the total of the capacities C res  plus C guard . The total oscillating circuit capacitance is however to be tuned precisely, as a result of which tuning capacitors are to be provided in parallel to the main capacitor C res  on the chip  24 , which are symbolized in the circuit diagram by means of the changeable capacitance C chip . As the manufacturing tolerances of the film conductor are particularly low in respect of the shielding, a low tuning range only is required in respect of the oscillating circuit capacitance. This can be realized by the capacitors and/or the changeable capacitance C chip  on the chip  24   
         [0038]      FIG. 10  shows a further embodiment of the inventive transmission facility. While a symmetrical wiring of the inductive antenna  10 , namely with the signal potentials Sig+ and Sig−, is possible with the circuit in  FIG. 9 , the circuit in  FIG. 10  realises a non-symmetrical wiring of the inductive antenna  10 . The one terminal of the coil  10  is positioned here across the signal line  14  on reference potential V ref . The other terminal of the coil  10  is positioned on signal potential Sig, which is provided like the reference V ref  of a chip  24 ′. The parallel resonance circuit C res , L res  thus lies on the two potentials V ref  and Sig. The shielding line  15  with the signal line  14  is short-circuited at one end of the film conductor  13 . The antenna still only has two terminals, instead of three, despite the shielding (cf.  FIGS. 7 and 8 ). This is particularly important for the miniaturization since only two of the relatively large surface terminal pads have then to be retained. To prevent current loops, provision is also advantageously made for the shielding layer and/or the shielding line  15  to only be connected to one side of the film conductor  13  with the reference potential terminal V ref .