WO2015127972A1

WO2015127972A1 - Hearing instrument comprising an rf antenna

Info

Publication number: WO2015127972A1
Application number: PCT/EP2014/053815
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 an ITE unit (16) to be worn at least in part in a user's ear canal (33) and including a microphone arrangement (24) for capturing audio signals, an audio signal processing unit (26) for processing the captured audio signals, and a loudspeaker arrangement (36) for stimulating a user's hearing according to the processed audio signals; a BTE unit (12) to be worn behind a user's ear (14) and including a power source (30), and an RF transceiver (28) for audio signal / data transmission within a carrier frequency range; a wire connection (19) extending between the BTE unit and the ITE unit for supplying the ITE unit with power from the power source and for enabling signal exchange between the transceiver and the ITE unit; and an antenna (29,38, 40) connected to the transceiver and forming part of the BTE unit or of the wire connection.

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 2011/0243357 Al 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 performance. 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 claim 1 and in claim 10, respectively.

The invention is beneficial in that, by providing a BTE unit with the power source and the RF transceiver and by providing an ITE unit with the microphone arrangement, the audio signal processing unit and the loudspeaker arrangement, with a wire connection extending between the BTE unit and the ITE unit for supplying the ITE unit with power from the power source and for enabling signal exchange between the BTE unit and the ITE unit, and wherein the antenna connected to the transceiver forms part of the BTE unit or of the wire connection, optimized RF transmission / reception characteristics are achieved due to the placement of the transceiver and the antenna outside the ear canal and an improved EMI behavior of the hearing instrument is achieved due to the physical separation of the RF system formed by the transceiver and the antenna and the other hearing instrument electronics, such as the audio signal processing unit. Further, since the BTE unit does not include components like the microphone arrangement, the audio signal processing unit and the loudspeaker, there is a lot of space in the BTE unit for a relatively large battery enabling longer battery lifetime or higher power consumption and, optionally, for an optimized design of the antenna; alternatively, the size of the BTE unit could be reduced compared to a classic BTE, thus making it more inconspicuous.

Rather than placing the RF transceiver in the BTE unit, it may be placed in the ITE unit. In this case, the power line connecting the component of the ITE unit with the power source contained in the BTE unit may be used as the RF antenna.

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 the invention when worn by a user, wherein the antenna forms part of the BTE unit; Fig. 2 is a block diagram of the hearing instrument of Fig. 1 ;

Fig. 3 is a block diagram of a variant of the hearing instrument of Fig. 1, wherein the antenna forms part of the wire connection between BTE unit and ITE unit;

Fig. 4 is a block diagram of a first example of a decoupling network to be used with a hearing instrument according to the invention; Fig. 5 is a block diagram of a first example of how the electrical impedance of the antenna wire of the hearing instrument of Fig. 3 may be adjusted;

Fig. 6 is a block diagram of a second example of how the electrical impedance of the antenna wire of the hearing instrument of Fig. 3 may be adjusted;

Fig. 7 is a block diagram of a third example of how the electrical impedance of the antenna wire of the hearing instrument of Fig. 3 may be adjusted;

Fig. 8 is a block diagram of a second example of a decoupling network;

Fig. 9 is a block diagram of a variant of the hearing instrument of Fig. 3;

Fig. 10 is a block diagram of a first example of how the electrical impedance of the antenna wire of the hearing instrument of Fig. 9 may be adjusted; Fig. 1 1 is a block diagram of a second example of how the electrical impedance of the antenna wire of the hearing instrument of Fig. 9 may be adjusted; and

Fig. 12 is a block diagram of a third example of how the electrical impedance of the antenna wire of the hearing instrument of Fig. 9 may be adjusted;

In Figs. 1 and 2 a first example of a hearing instrument according to the invention, when worn at the ear 14 of a user, is shown schematically. The hearing instrument comprises a BTE unit 12 to be worn behind the user's ear and an ITE (in-the-ear) unit 16 to be worn at least in part in the user's ear canal 33. The ITE unit 16 is detachably connected to the BTE unit 12 via a wire connection 19 carrying a connector 20 at its free end.

The ITE unit 16 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, and a loudspeaker 36 for generating sound directed towards the tympanic membrane 35 in the ear channel 33 according to the processed audio signals.

The BTE unit comprises a battery 30, an RF transceiver 28 and an RF antenna 29 connected to the transceiver 28. It is to be noted that, unlike in the example as illustrated in Fig. 1, the transceiver 28 may be placed close to the battery 30, in order to use the battery 30 as a ground plane for antenna 29.

The wire connection 19 comprises at least one signal line 38 for enabling audio signal/data exchange between the audio signal processing unit 26 and the transceiver 28 and a power line 40 for supplying power from the battery 30 to the electronics contained within the ITE unit 16. Alternatively, the power supply line and signal line(s) may be combined. The lines 38, 40 may share a common ground line (not shown) or may be provided with separate ground lines (not shown).

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 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. The antenna 29 may be a suitable type of loop antenna or monopole antenna which may be realized, for example, as a printed metallic structure on the housing of the BTE unit 12 or on a flexible printed circuit board (PCB) of the BTE unit 12. When realized as a monopole antenna, the antenna 29 preferably has an electrical length of about one quarter of the wavelength corresponding to the central frequency of the carrier frequency range, with metallic parts of the BTE unit 12, such as the battery 30, being adapted to act as a ground plane for the antenna. In general, the BTE unit 12 is much more appropriate for placement of the antenna 29 than the ITE unit 16, since the BTE unit 12 is worn outside the ear channel 33, thus offering a less obstructed propagation path for an RF signal, as compared to the ITE unit 16 placed in the ear channel 33, and since the BTE unit 12 tends to be larger than the ITE unit 16, thus offering more space for integration of an antenna.

An alternative embodiment is shown in Fig. 3, wherein at least one of the wires 38, 40 of the wire connection 19 is used as an RF antenna, thereby replacing the antenna 29 of Figs. 1 and 2. To this end, the audio signal/data line 38 may be connected via an RF coupling circuit 34 acting as a highpass filter to the antenna port of the RF transceiver 28 in order to electrically couple the transceiver 28 to the line 38 in the RF range, i.e. in particular at frequencies within the carrier frequency range. In addition, the audio signal/data line 38 is also connected to the data/signal port of the transceiver 28 via an RF decoupling network 132.

Alternatively, the transceiver 28 may be connected via the RF coupling circuit 34 to the power line 40 in order to use the power line 40 as an RF antenna, with the other end of the power line 40, i.e. the end connected to the components of the ITE unit 16, then being provided an RF decoupling network (not shown in Fig. 3).

In case that the signal line 38 is used as an RF antenna, the signal line 38 is connected via a RF decoupling network 32 to the audio signal processing unit 26, which acts as a low pass filter for electrically decoupling the signal line 38 from the audio signal processing unit 26 at RF frequencies, in particular at frequencies within the carrier frequency range, in order to avoid noise in the audio signal path resulting from RF antenna signals (as mentioned above, a similar RF decoupling network 132 is used to RF-wise decouple the signal line 38 from the audio signal/data port of the transceiver 28).

The at least one wire /line 38 (and/or 40) 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, acting as a short circuit at RF frequencies (not shown). 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 to the individual user. Thus, it may be necessary to compensate for the varying length of the wire connection 19 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. 5, which shows a block diagram of an example of the hearing instrument 10, according to which the wire connection 19 comprises an extension wire 41 connected to one of the wires of the signal line 38 where the RF signal is coupled to 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 19. The approach of Fig. 5 may be used in cases in which the wire connection 19 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 41 may be located, for example, at least in part within a retention element of the ITE unit (in case that such retention element is present). Similar to the example of Fig. 3, the data/signal port of the transceiver 28 is decoupled F-wise from the connector 20, i.e. from the wires 38 of the wire connection 19.

In the example of Fig. 5, the coupling unit 34 is adapted to electrically couple the transceiver 26 to both wires of a twisted pair arrangement 18 of the signal line 38 and comprises a coupling capacitor 34A, 34B for each of the wires. Thus, the RF signal is coupled to both wires 19, while the extension wire 41 is only coupled to one wire; this approach may as well be simplified to a single wire connection, potentially achieving the same antenna performance.

An example of the decoupling network 32 (or 132) is shown in Fig. 4, wherein a pair of ferrite beads 43 A, 42 A is provided for the first port and a pair of ferrite beads 43 B, 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. The decoupling network 32 of Fig. 4 is most suited for differential signals, e.g. connection of a speaker to an analog audio output. An example of a decoupling network for a single line, comprising only ferrite beads 43 A, 42A and a capacitor 44A is shown in Fig. 8. An alternative example of how the electrical length of the wire connection can be adapted is shown in Fig. 6, 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 46A, 46B at that end of the wire which is closer to the connector 20. In the example of Fig. 6, each of the wires of the twisted pair arrangement is provided with such series inductor 46A, 46B, respectively. . The approach illustrated in Fig. 6 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. According to a further alternative embodiment the electrical length of the antenna wires could be adapted by providing the at least one antenna wire with at least one ferrite bead for shortening the electrical length of that wire compared to a wire without the ferrite bead, with the ferrite bead acting to decouple that end of the wire which is closer to the ITE unit 16 for frequencies within the RF carrier frequency range. Such approach would be 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. An example of such embodiment is shown in Fig. 7, wherein each of the signal wires 38 of the wire connection 19 is provided with a ferrite bead 48 A, 48B located towards that end of the wire connection 19 connected to the ITE unit 16. In view of the potentially strong mutual RF coupling between the lines of the wire connection 1 (in a practical implementation the signal line(s) 38, the power line 40 and the ground line(s) will be placed closely together), all lines, independently whether they are used as an antenna (i.e. are coupled through an RF coupling unit 34 to the transceiver 28) or not, preferably are decoupled from the ITE and BTE side through appropriate decoupling networks (as indicated by 32 and 132 in the Figures for the lines used as an antenna). Coupling the RF signal to all lines may yield the most predictable results.

An alternative to the embodiment of Fig. 3 is shown in Fig. 9, according to which the transceiver 28 is located in the ITE unit 16 rather than in the BTE unit 12, so that the BTE contains the power source 30, whereas the ITE unit 16 contains the signal processing unit 26, the microphone arrangement 24, the loudspeaker arrangement 36, and the RF transceiver 28.

The power source 30 in the BTE unit 12 is connected to the ITE unit 16 via the wire connection 19 containing at least a power line 40. This power line 40 acts as the RF antenna, the RF transceiver 28 being connected to it via the RF coupling circuit 34. The end of the antenna connected to the ITE unit 16 is decoupled RF-wise via an RF decoupling network 32 from the power supply of the signal processing unit 26 and the power supply of the RF transceiver 28. The other end of the antenna connected to the BTE unit 12 is decoupled RF- wise from the battery 30 via an RF decoupling network 132.

In general, the antenna concept of the embodiment of Fig. 9, as applied to the power line 40, is very similar to that of the embodiment of Fig. 3, as applied to the signal lines 38. Thus, Figs. 10 to 12 show different examples of how the electrical impedance of the antenna wire (i.e. the power line 40) of the hearing instrument of Fig. 9 may be adjusted, with the principle of Fig. 10 corresponding to that of Fig. 5 (selection of appropriate physical length L), with the principle of Fig. 11 corresponding to that of Fig. 6 (use of a series inductor 46 to increase the electrical length), and with the principle of Fig. 12 corresponding to that of Fig. 7 (use of a ferrite bead 48 to shorten the electrical length), respectively.

In all embodiments, elements of a user interface (e.g. pushbutton, volume control) may be integrated into the BTE unit 12 (not shown). There are two options for connecting the user interface: In case of the embodiments of Figs. 1 to 7, the user interface can be connected to the RF transceiver 28. As an alternative for all embodiments, the user interface can be connected to the transceiver unit 28 or to the signal processing unit 26 through an additional line contained in the wire connection 19 (not shown).

Claims

3. A hearing instrument comprising: an ITE unit (16) to be worn at least in part in a user's ear canal (33) and including a microphone arrangement (24) for capturing audio signals, an audio signal processing unit (26) for processing the captured audio signals, and a loudspeaker arrangement (36) for stimulating a user's hearing according to the processed audio signals; a BTE unit (12) to be worn behind a user's ear (14) and including a power source (30), and an RF transceiver (28) for audio signal / data transmission within a carrier frequency range; a wire connection (19) extending between the BTE unit and the ITE unit for supplying the ITE unit with power from the power source and for enabling signal exchange between the transceiver and the ITE unit; and an antenna (29,38, 40) connected to the transceiver and forming part of the BTE unit or of the wire connection.

2. The hearing instrument of claim 1, wherein the antenna (29) is integrated within the BTE unit (12).

3. The hearing instrument of claim 2, wherein the antenna (29) is a printed metallic structure on a housing of the BTE unit (12).

4. The hearing instrument of claim 2, wherein the antenna (29) is a printed metallic structure on a flexible PCB of the BTE unit.

5. The hearing instrument of one of claims 2 to 4, wherein the antenna (29) has 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 (28), with metallic parts (30) of the BTE unit (12) being adapted to act as a ground plane for the antenna.

6. The hearing instrument of one of claims 2 to 4, wherein the antenna (29) is a loop antenna.

7. The hearing instrument of claim 1 , wherein the antenna is formed by at least one wire (38, 40) of the wire connection (19) and is connected to an antenna port of the transceiver (28) via an RF coupling unit (34).

8. The hearing instrument of claim 7, wherein the ITE unit (16) comprises a decoupling network (32) including a low pass arrangement for electrically decoupling the at least one wire (38, 40) of the wire connection (19) and the audio signal processing unit (26) within the carrier frequency range, and wherein the BTE unit (12) comprises an RF coupling unit (34) acting as a high pass arrangement for electrically coupling the antenna port of the transceiver (28) to said at least one wire within the carrier frequency range.

9. The hearing instrument of claim 8, wherein the BTE unit (12) comprises a decoupling network (132) including a low pass arrangement for electrically decoupling the wires (38, 40) of the wire connection (19) and the signal port of the transceiver (28) within the carrier frequency range.

10. A hearing instrument comprising: an ITE unit (16) to be worn at least in part in a user's ear canal (33) and including 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 audio signal / data transmission within a carrier frequency range; a BTE unit (12) to be worn behind a user's ear (14) and including a power source (30); a wire connection (19) extending between the BTE unit and the ITE unit for supplying the ITE unit with power from the power source; and an antenna formed by at least one wire (40) of the wire connection (19) and being connected to an antenna port of the transceiver (28) via an RF coupling unit (34).

1 1. The hearing instrument of one of claims 7 to 10, wherein said at least one wire (38, 40) 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 monopoie type antenna of the transceiver (28), with metallic parts (30) of the BTE unit (12) and/or the ITE unit (1 ) being adapted to act as a ground plane for the antenna.

12. The hearing instrument of claim 10, wherein the ITE unit (16) comprises a decoupling network (32) including a low pass arrangement for electrically decoupling the at least one wire (40) of the wire connection (19) and the power supply of the signal processing unit (26) and the power supply of the transceiver (28) within the carrier frequency range, and wherein the BTE unit (12) comprises a decoupling network (132) including a low pass arrangement for electrically decoupling the at least one wire (40) of the wire connection (19) and the power source (30) within the carrier frequency range.

13. The hearing instrument of one of claims 7 to 12, wherein the RF coupling unit (34) comprises at least one capacitor (34A, 34B).]

14. The hearing instrument of claim 11, wherein, wherein the wire connection (19) comprises at least one element (41 , 46A, 46B, 48 A, 48B) for changing the electrical length of said at least one wire (38, 40) compared to the electrical length resulting from the wire connection without said at least one element.

15. The hearing instrument of claim 14, wherein said at least one element is formed by an extension wire (41) connected to said at least one wire (38).

16. The hearing instrument of claim 15, wherein the extension wire (41) is at least in part located within a retention element of the ITE unit (16) provided for retaining the ITE unit at least in part within the ear canal.

17. The hearing instrument of claim 14, wherein the at least one wire (38, 40) is provided with at least one series inductor (46A, 46B) at that end of the wire which is closer to the transceiver (28) in order to adjust the impedance of the at least one wire within the carrier frequency range.

18. The hearing instrument of claim 14, wherein said at least one element is formed by a ferrite bead (48A, 48B) for shortening the electrical length of the at least one wire (38, 40).]

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