Patent Application
20090274328
This application claims priority of German application No. 10 2008 022 126.0 DE filed May 5, 2009, which is incorporated by reference herein in its entirety.
The present invention relates to an apparatus and method for reducing interference effects in the case of a wireless data transmission in hearing device applications.
In the case of the inductive wireless transmission of data from a hearing device, a relay station, a programming device or a remote controller to a hearing device equipped with a suitable receiving facility, it is difficult for both the maximum transmission power and also the receiving sensitivity to be restricted. Due to the relatively small capacity, voltage and peak current load of the available hearing device batteries, the maximum transmission power of hearing devices is restricted.
On the other hand, legal restrictions exist in respect of the maximum transmission power of radio systems. A correspondingly restricted transmission range thus results. With present-day conventional inductive systems, the reduction in the field strength is highly crucial in the near field normally used, as a function of the distance.
Due to the low level of the useful signal at the receiver which results therefrom, already very low power sources of interference can massively influence the transmission quality. Essential components both of the transmission system as well as of the receiving hearing device nevertheless generate constructionally-specific electromagnetic emissions, which act as sources of interference in receiving systems. Such sources of interference are for instance the inductances of clocked voltage controllers, semiconductor components or supply and output lines of practically all clocked electronic circuits. The so-called receiver of the hearing devices is also an additional source of interference.
According to the prior art, shielding the source of interference with suitable materials, e.g. with a μ-metal or another suitable electrically conductive material is one measure. A so-called μ-metal contains metal alloys with a high permeability μ. These shield low frequency magnetic fields (so-called ferromagnetic shielding). The details of this can be found for instance in Zimmermann, J. E., SQUID Instruments and Shielding for low-level magnetic measurements. J. Appl. Phys.; 48:702-710, 1977.
A further known measure is, where possible, adequate distance between the transmitting and/or receiving coil in respect of the source of interference.
The publication DE 10 2006 049 471 A1 discloses a method for estimating an interference field for an antenna coil. Antennae and hearing device receivers can thus be positioned such that the interference is minimized by the hearing device receiver.
The object underlying the present invention is to prevent the illustrated difficulties in as effective and cost-effective a way as possible.
According to the invention, this object is achieved by an apparatus and a method as claimed in one of the independent claims. Advantageous developments of the invention result from the subclaims.
The invention claims an apparatus for reducing an interference input coupling caused by asymmetrically embodied field lines of at least one hearing device component into a receiving antenna of a wireless data transmission facility of a hearing device.
All components of a hearing device which are current-carrying or occupied with electrical charge transmit electromagnetic interference fields. The starting point of such interference signals are electrical supply lines (wires, stranded wires, conductors) or passive and active components. Significant interference signal sources in hearing devices are for instance clocked voltage controllers, analog and digital semiconductor components, supply and output lines of clocked circuits as well as the hearing device receiver. The field pattern of the radiated electrical and magnetic interference fields of a component depends on the form of the corresponding electrically conductive and/or magnetic parts as well as on electrically conductive and/or magnetic components in their vicinity.
The presence of electrically conductive and/or magnetic components in the hearing device results in a field distortion of the interference field. On the one hand, local zero points of the electrical and/or magnetic interference field distort or are lost. On the other hand, the distortion of the field lines results in an asymmetry of the input coupling into the receiving antenna. In both cases the interference input coupling into the receiving antenna increases. The outgoing electromagnetic interference signal is received at the site of the receiving antenna or a receiving coil of a wireless signal transmission system, which uses the inductive range or the typical HF range. The interference influence of the magnetic field on the receiving antenna depends on the amplitude and the direction of the magnetic field in respect of the alignment of the antenna. It is often not possible to sufficiently reduce the amplitude of the interference field at the site of the antenna using suitable shielding measures. If the magnetic field is preferably arranged at right angles to the receiving antenna, the interference field influence is minimized. The interference input coupling of the magnetic field into the receiving antenna can however also be reduced by using geometric arrangements, in which a symmetrical input coupling of the field lines takes place and the interference currents induced into the coil are thus largely erased. To this end, symmetry and/or radiation characteristics of the hearing device components can thus be used.
The apparatus according to the invention includes at least one first means arranged in the hearing device, by means of which the asymmetry of the field lines is reduced and the field distortion is corrected. In addition or alternatively, the receiving antenna can also be geometrically adjusted to the outer interference field of the hearing device components such that the interference currents induced by field input coupling are compensated in the antenna. As a result, the interference input coupling into the receiving antenna is reduced.
In accordance with the invention, the first means for reducing the asymmetry of the field lines has metallic properties.
A compensation plate is preferably used as a first means, which corrects the field distortion such that the input coupling is symmetrical again and the interference influence reduces.
In a further advantageous embodiment of the invention, already existing suitable metallic and/or magnetic hearing device components (e.g. microphone, shielding plates) can be used for the purpose of miniaturization as a first means instead of a compensation plate in order to compensate for the asymmetry of the field. As a result, an additional component can be avoided and the minimal space available in the hearing device can be optimally used for other hearing device components and/or the structural shape of the devices can be reduced.
In a further preferred embodiment, the receiving antenna has a coil bobbin, the winding of which has a variable tightness. As a result, the resulting induced interference currents are compensated in the antenna in the case of asymmetrical interference field input coupling.
In a further advantageous embodiment, the coil bobbin is asymmetrical, e.g. is embodied in conical form. This embodiment is then selected if the outer field has a field gradient in the coil direction.
The invention also claims a method for reducing an interference input coupling caused by asymmetrically embodied field lines into at least one hearing device component in a receiving antenna of a wireless data transmission facility of a hearing device. Here the asymmetrical field lines are corrected and/or compensated. In addition or also alternatively, a compensation of an induced interference current resulting due to the asymmetrical interference field input coupling takes place.
Further details and advantages of the invention are apparent from the descriptions that follow in respect of several exemplary embodiments with reference to schematic drawings, in which;
a: shows a schematic view of an idealized symmetrical input coupling into an antenna,
b: shows a schematic view of an asymmetrical field distortion by means of metalizing a conductor board,
c: shows a schematic view of a compensation of a field asymmetry by means of a metal sheet according to an exemplary embodiment of the invention,
a: shows a schematic view of a variation of the winding tightness of a coil bobbin in accordance with an exemplary embodiment of the invention,
b: shows a schematic view of an asymmetrical winding of a coil bobbin in accordance with an exemplary embodiment of the invention,
c: shows a schematic view of an asymmetrical coil bobbin in accordance with an exemplary embodiment of the invention and
d: shows a schematic view of a combination of a variation of the winding tightness of a coil bobbin and an asymmetrical coil bobbin in accordance with an exemplary embodiment of the invention.
a shows the ideal state of an interference field of a receiver. The interference influence in an antenna is minimal as a result of a symmetrical input coupling, since induced interference currents are compensated.
In
c shows the use of a compensation plate, by means of which a field distortion is corrected, so that the input coupling is symmetrical again and the interference influence reduces.
The receiving antenna can be embodied geometrically such that with asymmetrical interference field input coupling the resulting induced interference currents in the antenna are compensated.
Further exemplary embodiments are shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 022 126.0 | May 2008 | DE | national |
