WO2015127973A1

WO2015127973A1 - Hearing instrument comprising an rf antenna

Info

Publication number: WO2015127973A1
Application number: PCT/EP2014/053816
Authority: WO
Inventors: Marc Secall; Hans-Ueli Roeck; Yves Oesch; Francois Callias; Jan Angst; Stephan Gehring
Original assignee: Sonova AG
Current assignee: Sonova Holding AG
Priority date: 2014-02-27
Filing date: 2014-02-27
Publication date: 2015-09-03
Anticipated expiration: 2016-08-27

Abstract

There is provided a hearing instrument comprising a microphone arrangement (24) for capturing audio signals; an audio signal processing unit (26) for processing the captured audio signals; a loudspeaker arrangement (36) for stimulating a user's hearing according to the processed audio signals; and an RF transceiver (28) for signal and/or data transmission within a carrier frequency range; wherein the audio signal processing unit and the RF transceiver are arranged in a BTE unit (12) to be worn behind the user's ear (14) and the loudspeaker arrangement is arranged in a RIC unit (16) to be worn at least in part in the user's ear canal; with the BTE unit and the RIC unit being detachably connected via a connector (20); wherein the RIC unit comprises a wire connection (19) comprising at least two wires (18) for supplying the processed audio signals from the audio signal processing unit to the loudspeaker arrangement; wherein the BTE unit comprises a decoupling network (32) including a low pass arrangement for electrically decoupling said wires and the audio signal processing unit within the carrier frequency range and an RF coupling unit (34) acting as a high pass for electrically coupling the transceiver to said at least one wire within the carrier frequency range; and wherein said at least one wire is designed to have an electrical length of about one quarter of the wavelength corresponding to the center frequency of the carrier frequency range in order to act as a monopole type antenna of the transceiver, with metallic parts (30) of the BTE unit being adapted to act as a ground plane for the antenna.

Description

Hearing instrument comprising an RF antenna

The information relates to a hearing instrument comprising an RF (radio frequency) transceiver and an RF antenna.

Hearing instruments may be provided with RF transceivers for enabling, for example, the use of wireless microphones with the hearing instruments, for enabling binaural communication between the hearing instruments of a binaural system, and/or for enabling audio signals and other data exchange with hearing instruments worn by other persons. Typically, such wireless links use carrier frequencies from 3 MHz to 2.4 GHz, with a trend towards standardized 2.4 GHz solutions. However, RF transmission close to the head or even from within the head (i.e. from within the ear channel) is problematic, since the head contains a large volume of water, readily absorbing 2.4 GHz radiation. Further, typically the power budget is relatively limited for ear level devices. Consequently, efficient antenna design is very important for a reliable wireless connection.

US 2010/0321269 Al relates to a BTE (behind-the-ear) hearing instrument, wherein, according to one example, an antenna wire having a length of about a half wavelength is integrated within a sound tube extending into the ear channel, with a reflector acting as a parasitic element likewise having a length of about half a wavelength being disposed within the BTE body casing at a distance of about a quarter of a wavelength from the antenna wire. According to another example, the hearing instrument comprises a RIC (receiver-in-the- channel) unit for placing the loudspeaker of the hearing instrument in the ear channel, with a grounded outer conductor shielding the signal line from the BTE part to the loudspeaker being used as an antenna having a length of about half of a wavelength, with a reflector likewise having a length of about half a wavelength being included within the BTE part. The BTE unit also comprises a matching circuit for providing for impedance matching between the grounded conductor acting as the antenna and the RF transceiver.

US 201 1/0243357 A 1 relates to a hearing instrument comprising a BTE unit comprising a power source, a microphone and a loudspeaker and an ITE unit to be worn in the ear channel and comprising a second microphone, an audio signal processing unit and an RF transceiver, with a sound tube including signal and power connection lines extending from the BTE unit to the ear channel unit. The wire connection may be used as an antenna. EP 1 587 343 Bl relates to a hearing instrument wherein an antenna is formed by a conducting layer inside or outside or in between the housing of the hearing instrument.

One of the major problems of hearing instrument antenna design resides in the fact that the hearing instrument electronics act as parasitic elements and thus have an impact on antenna perfonnance. Further, also user interaction, such as scratching at the ear may temporarily deteriorate antenna performance.

It is an object of the invention to provide for a hearing instrument including an efficient RF antenna, wherein the impact of the hearing instrument electronics and user interaction on antenna performance is low and wherein the power consumption is relatively low.

According to the invention, this object is achieved by a hearing instrument as defined in claims 1 and 14, respectively.

The invention is beneficial in that, by using connection wires between a BTE unit and an RIC unit or a wire in a sound tube extending from a BTE unit into the ear channel as an antenna having an electrical length of about one quarter of the wavelength corresponding to the center frequency of the carrier frequency range in order to act as a monopole type antenna of the RF transceiver, with metallic parts of the BTE unit being adapted to act as a ground plane for the antenna, a simple and robust antenna design with high performance and efficiency can be realized, thereby providing for a reliably wireless connection with low power consumption.

Preferred embodiments of the invention are defined in the dependent claims.

Hereinafter, examples of the invention will be illustrated by reference to the attached drawings, wherein:

Fig. 1 is a lateral view of a schematic example of a hearing instrument according to a first aspect of the present invention;

Fig. 2 is a block diagram of a first embodiment of a hearing instrument according to the invention;

Fig. 3 is a block diagram of an example of a decoupling network to be used with a hearing instrument according to the invention;

Fig. 4 is a block diagram of a second embodiment of a hearing instrument according to the invention; Fig. 5 is a block diagram of a third embodiment of a hearing instrument according to the invention;

Fig. 6 is a block diagram of a fourth embodiment of a hearing instrument according to the information comprising an ear channel microphone; Fig. 7 is a longitudinal sectional view of parts of an example of hearing instrument according to a second aspect of the invention;

Fig. 8 is a view like Fig. 7, wherein an alternative embodiment is shown; and

Fig. 9 is a schematic perspective view of the connector area of the sound tube of another alternative embodiment of a hearing instrument. In Fig. 1 an example of a healing instrument according to a first aspect of the invention worn at the ear of a user is shown schematically. The hearing instrument 10 comprises a BTE unit 12 to be worn behind the user's ear 14 and a RIC unit 16 to be worn at least in part in the user's ear channel; the RIC unit 16 is detachably connected to the BTE unit 12 via a wire connection 19 carrying a connector 20 at its free end. The RIC unit also comprises a flexible retention element 22 for engagement with the user's concha in order to keep the RIC unit 1 in place.

The BTE unit 12 comprises a microphone arrangement 24 for capturing audio signals from ambient sound, an audio signal processing unit 26 for processing and amplifying the captured audio signals, an RF transceiver 28, a battery 30, a decoupling network 32 and an RF coupling circuit 34.

The RIC unit 16 comprises a loudspeaker 36 (see Figs. 2, and 4 to 6) which is connected via the wire connection 19 and the decoupling network 32 to the audio signal processing unit 26, so that the audio signal processing unit 26 is able to supply processed audio signals to the loudspeaker 36. The wire connection 19 comprises at least two wires 18 (see Figs. 2 and 4 to 6) for such audio signal supply, with the wires 18 preferably forming a twisted pair arrangement.

The RF transceiver 28 may be used for wireless data and/or audio signal exchange with external devices, such as another hearing instrument worn at the other ear of the user for establishing a binaural system, a wireless microphone, an audio streaming device, such as an audio signal transmitter of a TV set or of a HiFi system, a mobile phone, a remote control, etc. Typically, the RF transceiver 28 will use a carrier frequency range from 2.400 to 2,484 GHz in the ISM band. According to one example, the wireless link may be implemented as a link using a GFS modulated signal, such as a Bluetooth link.

At least one wire of the wire connection 19 is used as a monopole type antenna by the RF transceiver 28, via the RF coupling circuit 34 acting as a high pass filter for electrically coupling the transceiver 28 to that at least one wire within the carrier frequency range. The decoupling network 32 acts as a low pass filter for electrically decoupling the wires 18 of the wire connection 19 from the audio signal processing unit 26 within the carrier frequency range in order to avoid noise in the audio signal path resulting from RF antenna signals. The at least one wire 18 used as the antenna is designed to have an electrical length of about one quarter of the wavelength corresponding to the center frequency of the carrier frequency range, with metallic parts of the BTE unit 12 being adapted to act as a ground plane for the antenna in order to implement a monopole type antenna. Typically, the battery 30 and metallic parts of the electronics included within the BTE unit 12 would act together, at frequencies in the RF range, as a ground plane for the antenna and, to this end, may be connected via coupling capacitors (as indicated schematically at 39 in Fig. 1, wherein the coupling capacitor 39 connects the battery 30 to the transceiver 28). Typically, the ear geometry of different persons is different, so that the wire connection 19 in practice would be provided at different lengths in order to customize the hearing instrument 10, to some extent, with regard the individual user. Thus, it may be necessary to compensate for the varying length of the wire connection 18 when using at least one of the wires as a monopole type antenna.

A first example of how such compensation may be achieved is shown in Fig. 2, which shows a block diagram of an example of the hearing instrument 10, wherein with regard to the BTE unit 12 only the interface to the RIC unit 16 is shown. According to the example of Fig. 2, the wire connection 19 comprises an extension wire 38 connected to one of the wires 18 of the wire connection 19 in order to act as an element for changing the electrical length of one of the wires compared to the electrical length resulting from or corresponding to the geometric length of the wire connection 18. The approach of Fig. 2 may be used in cases in which the wire connection 18 is too short for providing for an antenna wire having an electrical length of about one quarter of the carrier frequency wavelength. The extension wire 38 may be located, for example, at least in part within the retention element 22 shown in Fig. 1. In the example of Fig. 2, the coupling unit 34 is adapted to electrically couple the transceiver 28 to both wires of the twisted pair arrangement 18 of the wire connection 19 and comprises a capacitor 34A, 34B for each of the wires.

An example of the decoupling network 32 is shown in Fig. 3, wherein a pair of ferrite beads 40A, 42A is provided for the first port and a pair of ferrite beads 40B, 42B is provided for the second port, with each pair being connected in series. In addition, two capacitors 44A, 44B are provided in a series connection for connecting the two channels at a point between the first ferrite bead 40A, 40B and second ferrite bead 42A, 42B of each port / channel, with the connection between the two capacitors 44A, 44B being connected to ground. An alternative example of how the electrical length of the wire connection can be adapted is shown in Fig. 4, wherein the impedance, i.e. the electrical length, of the wire connection 19 is adapted by providing the at least one antenna wire of the wire connection 19 with at least one series inductor 4 A, 46B at that end of the wire which is closer to the connector 20. In the example of Fig. 4, each of the wires of the twisted pair arrangement is provided with such series inductor 46 A, 46B, respectively. The approach illustrated in Fig. 4 is particularly suitable in case that the wire connection 19 is "too short", i.e. has a length of less than one quarter of the wavelength corresponding to the center frequency of the carrier frequency range.

Although in theory such concept may be extended to using a more complex impedance matching network than just a series inductor (any combination of capacitors and inductors may allow to achieve a more accurate impedance matching of the wires), a practical implementation will be limited by the fact that only reduced space is available to accommodate such impedance matching network within the RIC unit and that the numbers of pins of the connector 20 will be limited, so that typically the ground connection required for a more complex impedance matching network would not be available.

A further alternative embodiment of how the electrical length of the antenna wires could be adapted is shown in Fig. 5, wherein the at least one antenna wire comprises at least one ferrite bead 48 A, 48B for shortening the electrical length of that wire compared to a wire without the ferrite bead, with the ferrite bead 48 A, 48B acting to decouple that end of the wire which is closer to the loudspeaker arrangement 36 for frequencies within the RF carrier frequency range. The approach illustrated in Fig. 5 is particularly suitable in case that the wire connection 19 is "too long", i.e. has a length of more than one quarter of the wavelength corresponding to the center frequency of the carrier frequency range.

In the example of Fig. 5, each of the wires of the twisted pair arrangement is provided with such ferrite bead 48 a, 48b, respectively. According to another alternative embodiment, which is less preferred than the above- described embodiments, the at least one antenna wire may be provided in a meander-type shape, or in a spiral or helical shape, in order to increase the electrical length of the wire compared to a wire having a straight shape; thus, a relatively short type of the wire connection 19 would have a more pronounced meander-type (or spiral or helical) shape than a relatively long one. However, this solution has the drawback that a meander-type (or spiral or helical) wire shape would result in a relatively large size of the RIC unit 16, in particular of the wire connection 19.

In Fig. 6 an alternative design of the hearing instrument 10 is shown, wherein the RIC unit 16 is provided with a microphone 124 which may replace the microphone 24 or which may be provided in addition to the microphone 24 of the BTE unit 12, and which is connected to the BTE unit, namely to the audio signal processing unit 26, by an additional wire pair 118 of the wire connection 19. The BTE unit 12 comprises a second decoupling network 132 acting as a low pass filter for electrically decoupling the wire pair 118 of the microphone 124 from the audio signal processing unit 26 at frequencies within the RF carrier frequency range. In Fig. 7 an alternative embodiment of an RF antenna to be used with the invention is shown schematically, wherein the hearing instrument 210 comprises a BTE unit 212 and a sound tube 250 which is coupled to the BTE unit 212 via a mechanical interface 220 and which extends into the user's ear channel. The BTE unit 212 comprises, as in the previously described embodiments, a microphone 224, an audio signal processing unit 226, an RF transceiver 228 and a battery 230. In addition, the BTE unit 212 comprises a loudspeaker 236 for generating sound from the processed audio signals, which sound is directed via the sound tube 250 into the ear channel. The sound tube 250 preferably is designed as a slim tube.

The sound tube 250 is provided with a wire 252 which is electrically connected, via the interface 220, to the RF transceiver 228 and which is designed to have an electrical length of about one quarter of the wavelength corresponding to the carrier frequency in order to act as a monopole type antenna of the transceiver 228, with metallic parts of the BTE unit 212 being adapted to act as a ground plane for the antenna.

The sound tube 250 usually will be provided in different lengths for enabling adjustment of the hearing instrument to the individual ear anatomy. However, since the antenna wire 252 does not form part of the function provided by the sound tube 250, namely to conduct sound from the loudspeaker 236 to the ear channel, the antenna wire 252 may have the same default length for all different lengths of the sound tube 250, so that, provided that the length of the tube 250 is approximately equal to or longer than one quarter of the wavelength corresponding to the center frequency of the carrier frequency range, usual no further adaptation of the electrical length of the antenna wire 252 will be necessary - in contrary to the previously described embodiments wherein the electrical connection from the BTE unit to the ear piece is used as an antenna.

However, in case that a sound tube 250 having a length smaller than lambda/4 is to be used, in which case also the length of the antenna wire 252 would be smaller than lambda 4, a series feed inductor could be coupled to the antenna wire 252 in order to increase its electrical length to lambda/4. Similar to the embodiment Fig. 4, such feed inductor may be an integral part of a matching / HF coupling network 234.

In the example of Fig. 7, the interface 220 comprises a thread connection 254, 256 which is metallic, wherein the antenna wire 252 is electrically connected to the portion 254 of the thread interface 220 forming part of the sound tube 250, and wherein the RF transceiver 228 is electrically connected to the portion 256 of the thread interface 220 forming part of the BTE unit 212. The RF transceiver 228 is connected to the thread connection 254, 256 via the matching network 234. The mechanical connection between the two portions 254 and 256 of the thread interface 220 provides for the electrical connection between the antenna wire 252 and the RF transceiver 228 when the sound tube 250 is connected to the BTE unit 212.

A variation of the embodiment of Fig. 7 is shown in Fig. 8 (with lower part of Fig. 8 showing a view in the direction A of the upper part), wherein the thread connection is not completely made of metal (or coated with metal) as in Fig. 7 but rather already comprises at least one metallic contact area formed by metallic parts of the thread connection 320. In the example of Figs. 7 and 8, the thread portion 356 of the BTE unit 212 is provided with two contact areas 358. The thread connection counter-part of the sound tube 250 may be made completely of metal (or coated with metal) or may comprise corresponding metallic contact areas.

A further variation of the interface is shown in Fig. 9, wherein a metallic contact area 460 is provided at a surface 462 of the BTE unit 212 oriented in an axial direction of the sound tube 250 at a location close to the thread connection portion 456 of the BTE unit 212. The mating front surface of the sound tube 250 is provided with a corresponding contact area (not shown in Fig. 9) to which the antenna wire 252 is electrically connected to and which touches the contact area 460 of the BTE unit 212 when the sound tube 250 is connected to the BTE unit 212.

According to a further variant, the interface between the sound tube 250 and the BTE unit 212 may comprise a metallic plug-in connector for achieving the electrical connection between the antenna wire 252 and the RF transceiver 228.

Claims

A hearing instrument comprising: a microphone arrangement (24) for capturing audio signals; an audio signal processing unit (26) for processing the captured audio signals; a loudspeaker arrangement (36) for stimulating a user's hearing according to the processed audio signals; and an RF transceiver (28) for signal and/or data transmission within a carrier frequency range; wherein the audio signal processing unit and the RF transceiver are arranged in a BTE unit (12) to be worn behind the user's ear (14) and the loudspeaker arrangement is arranged in a RIC unit (16) to be worn at least in part in the user's ear canal; with the BTE unit and the RIC unit being detachably connected via a connector (20); wherein the RIC unit comprises a wire connection (19) comprising at least two wires

(18) for supplying the processed audio signals from the audio signal processing unit to the loudspeaker arrangement; wherein the BTE unit comprises a decoupling network (32) including a low pass arrangement for electrically decoupling said wires and the audio signal processing unit within the carrier frequency range and an RF coupling unit (34) acting as a high pass for electrically coupling the transceiver to said at least one wire within the carrier frequency range; wherein said at least one wire is designed to have an electrical length of about one quarter of the wavelength corresponding to the center frequency of the carrier frequency range in order to act as a monopole type antenna of the transceiver, with metallic parts (30) of the BTE unit being adapted to act as a ground plane for the antenna.

The hearing instrument of claim 1, wherein the wires (18) form a twisted pair arrangement.

The hearing instrument of claim 2, wherein the RF coupling unit (34) is adapted to electrically couple the transceiver to both wires (18) of the twisted pair arrangement within the carrier frequency range.

The hearing instrument of one of the preceding claims, wherein the wire connection

(19) comprises at least one element (38; 46A, 46B; 48A, 48B) for changing the electrical length of said at least one wire (18) compared to the electrical length resulting from the wire connection (18, 19) without said at least one element.

5. The hearing instrument of claim 4, wherein said at least one element is formed by an extension wire (38) connected to said at least one wire (18).

6. The hearing instniment of claim 5, wherein the extension wire (38) is- at least in part located within a retention element (22) of the RIC unit (16) provided for retaining the RIC unit at least in part within the ear canal.

7. The hearing instrument of claim 4, wherein the at least one wire (18) comprises at least one ferrite bead (48A, 48B) for shortening the electrical length of the at least one wire compared to a wire without the ferrite bead(s), the ferrite bead(s) acting to decouple that end of the wire which is closer to the loudspeaker arrangement (36) within the carrier frequency range.

8. The hearing instrument of claim 4, wherein the at least one wire (18) is provided with at least one series inductor (46 A, 46B) at that end of the wire which is closer to the connector (20) in order to adjust the impedance of the at least one wire within the carrier frequency range.

9. The hearing instrument of one of the preceding claims, wherein the at least one wire (18) has a spiral or helical shape in order to increase the electrical length compared to a wire having a straight shape.

10. The hearing instrument of one of the preceding claims, wherein the microphone arrangement or an additional microphone (124) forms part of the RIC unit (16), and wherein the microphone arrangement or additional microphone is electrically connected to the audio signal processing unit (26) by wires (118) of the wire connection (19), wherein the BTE unit comprises a microphone decoupling network (132) including a low pass arrangement for electrically decoupling the wires connecting the microphone arrangement or additional microphone connected to the audio signal processing unit within the carrier frequency range.

11. The hearing instrument of one of the preceding claims, wherein a battery (30) located within the BTE unit (12) and other metallic parts located within the BTE unit are connected via coupling capacitors (39) in order to act as a ground plane for the antenna (18).

12. The hearing instrument of one of the preceding claims, wherein the decoupling network (32) comprise at least two ferrite beads (40A, 40B, 42 A, 42B) and at least one capacitor (44A, 44B).

13. The hearing instrument of one of the preceding claims, wherein the RF coupling unit (34) comprises at least one capacitor (34A, 34B).

14. A hearing instrument comprising: a BTE unit (212) to be worn behind a user's ear (14) and including a microphone arrangement (224) for capturing audio signals, an audio signal processing unit (226) for processing the captured audio signals, a loudspeaker arrangement (236) for stimulating a user's hearing according to the processed audio signals, and an RF transceiver (228) for signal and/or data transmission within a carrier frequency range; and a sound tube (250) coupled to the BTE unit via a mechanical interface (220) for extending from the BTE unit into the user's ear canal, wherein the sound tube comprises a wire (252) which is electrically connected via the interface to the RF transceiver, wherein the wire is designed to have an electrical length of about one quarter of the wavelength corresponding to the center frequency of the carrier frequency range in order to act as a monopole type antenna of the transceiver, with metallic parts (30) of the BTE unit being adapted to act as a ground plane for the antenna.

15. The hearing instrument of claim 14, wherein the interface (220) comprises a thread connection (254, 256, 356, 456).

16. The hearing instrument of claim 15, wherein the thread connection (254, 256) is metallic.

17. The hearing instrument of claim 15, wherein the thread connection (356) comprises at least one metallic contact area (358) formed by metallic parts of the thread connection.

18. The hearing instrument of claim 15, wherein the interface (220) comprises a metallic contact area (460) provided at a surface (462) oriented in an axial direction of the sound tube (250).

19. The hearing instrument of claim 15, wherein the interface comprises a metallic plug-in connector.

20. The hearing instrument of one of claims 14 to 19, wherein the wire (252) is connected with a series feed inductor (234) in order to increase the electrical length of the wire.

21. The hearing instrument of one of the preceding claims, wherein the carrier frequency range is from 2.400 to 2.484 GHz.