BTE hearing aid having a balanced antenna

Abstract

A behind the ear hearing aid includes: a transceiver for wireless data communication interconnected with an antenna for electromagnetic field emission and electromagnetic field reception, the antenna extending on a first side of a hearing aid and a second side of the hearing aid, a first segment of the antenna extending from proximate the first side of the hearing aid to proximate the second side of the hearing aid; and a feed system configured for exciting the antenna to induce a current in at least the first segment, the current having a first local maxima proximate the first side of the hearing aid and a second local maxima proximate the second side of the hearing aid.

Claims

1. A behind the ear hearing aid comprising: a microphone for reception of sound and conversion of the received sound into a corresponding first audio signal; a signal processor for processing the first audio signal into a second audio signal compensating a hearing loss of a user of the hearing aid; a receiver that is connected to an output of the signal processor for converting the second audio signal into an output sound signal; a transceiver for wireless data communication interconnected with an antenna for electromagnetic field emission and electromagnetic field reception, the antenna extending on a first side of the hearing aid and a second side of the hearing aid, a first segment of the antenna extending from proximate the first side of the hearing aid to proximate the second side of the hearing aid; and a feed system configured for exciting the antenna to induce a current in at least the first segment, the current having a first local maxima proximate the first side of the hearing aid and a second local maxima proximate the second side of the hearing aid.

2. The hearing aid according to claim 1, wherein the antenna is a balanced antenna.

3. The hearing aid according to claim 1, wherein a part of the antenna extending proximate the first side of the hearing aid is substantially identical to a part of the antenna extending proximate the second side of the hearing aid.

4. The hearing aid according to claim 1, wherein the feed system comprises a first feed point for exciting at least the antenna proximate the first side of the hearing aid and a second feed point for exciting at least the antenna proximate the second side of the hearing aid.

5. The hearing aid according to claim 1, wherein the first segment has a direction substantially orthogonal to a surface of a head of the user when the hearing aid is worn in its operational position by the user.

6. The hearing aid according to claim 1, wherein the first segment is configured to short circuit a part of the antenna proximate the first side of the hearing aid and a part of the antenna proximate the second side of the hearing aid to provide a current bridge between the first side of the hearing aid and the second side of the hearing aid.

7. The hearing aid according to claim 1, wherein a part of the antenna extending proximate the first side of the hearing aid and/or a part of the antenna extending proximate the second side of the hearing aid has the shape of a monopole antenna structure.

8. The hearing aid according to claim 6, wherein one or each of (1) a length of the part of the antenna extending proximate the first side of the hearing aid and (2) a length of the part of the antenna extending proximate the second side of the hearing aid, as measured from the short circuit to a free end, is substantially lambda/4.

9. The hearing aid according to claim 1, wherein a part of the antenna extending proximate the first side of the hearing aid and/or a part of the antenna extending proximate the second side of the hearing aid has a circumference of lambda/2.

10. The hearing aid according to claim 1, wherein the antenna comprises an annulus shaped antenna structure having a circumference of lambda/2.

11. The hearing aid according to claim 1, wherein a part of the antenna extending proximate the first side of the hearing aid comprises a first resonant structure and/or a part of the antenna extending proximate the second side of the hearing aid comprises a second resonant structure.

12. The hearing aid according to claim 4, wherein the hearing aid has a plane of partition extending between the first side of the hearing aid and the second side of the hearing aid, and wherein at least a part of the antenna intersects the plane of partition at an intersection, and wherein a relative difference between a distance from the first feed point to the intersection and a distance from the second feed point to the intersection is less than or equal to a first threshold.

13. The hearing aid according to claim 12, wherein the plane of partition comprises a symmetry plane for the first and second antenna structures.

14. The hearing aid according to claim 12, wherein the threshold is less than 25%.

15. The hearing aid according to claim 4, wherein a distance between the first feed point and a short circuit, and a distance between the second feed point and the short circuit, respectively, are tailored to achieve a desired antenna impedance.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The drawings illustrate the design and utility of embodiments, in which similar elements are referred to by common reference numerals. These drawings are not necessarily drawn to scale. In order to better appreciate how the above-recited and other advantages and objects are obtained, a more particular description of the embodiments will be rendered, which are illustrated in the accompanying drawings. These drawings depict only typical embodiments and are not therefore to be considered limiting of its scope.

(2) FIG. 1 is a phantom head model of a user together with an ordinary rectangular three dimensional coordinate system with an x, y and z axis for defining the geometrical anatomy of the head of the user,

(3) FIG. 2 shows a block-diagram of a typical hearing aid,

(4) FIG. 3 shows a behind the ear hearing aid having an antenna according to one embodiment,

(5) FIG. 4 shows a behind the ear hearing aid having an antenna according to another embodiment,

(6) FIG. 5 shows a behind the ear hearing aid having an antenna according to a further embodiment,

(7) FIG. 6 shows a behind the ear hearing aid having an antenna according to a still further embodiment,

(8) FIG. 7 shows a behind the ear hearing aid having an antenna according to a another embodiment,

(9) FIGS. 8a-8e show schematically the feed and the short circuit for different embodiments,

(10) FIGS. 9a-b show schematically the length of the current path on an antenna,

(11) FIGS. 10a-d show schematically the current distribution along an antenna,

(12) FIGS. 11a-d show schematically a partition plane for different antenna structures,

DETAILED DESCRIPTION

(13) Various exemplary embodiments are described hereinafter with reference to the figures. It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the embodiments. They are not intended as an exhaustive description of the claimed invention or as a limitation on the scope of the claimed invention. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated, or not so explicitly described.

(14) The radiation pattern of an antenna is typically illustrated by polar plots of radiated power in horizontal and vertical planes in the far field of the antenna. The plotted variable may be the field strength, the power per unit solid angle, or directive gain. The peak radiation occurs in the direction of maximum gain.

(15) FIG. 1 is a phantom head model of a user seen from the front together with the ordinary rectangular three dimensional coordinate system.

(16) When designing antennas for wireless communication proximate the human body, the human head can be approximated by a rounded enclosure with sensory organs, such as the nose, ears, mouth and eyes attached thereto. Such a rounded enclosure 3 is illustrated in FIG. 1. In FIG. 1, the phantom head model is shown from the front together with an ordinary rectangular three dimensional coordinate system with an x, y and z axis for defining orientations with relation to the head and for defining the geometrical anatomy of the head of the user;

(17) Every point of the surface of the head has a normal and tangential vector. The normal vector is orthogonal to the surface of the head while the tangential vector is parallel to the surface of the head. An element extending along the surface of the head is said to be parallel to the surface of the head, likewise a plane extending along the surface of the is said to be parallel to the surface of the head, while an object or a plane extending from a point on the surface of the head and radially outward from the head into the surrounding space is said to be orthogonal to the head.

(18) As an example, the point with reference numeral 2 in FIG. 1 furthest to the left on the surface of the head in FIG. 1 has tangential vectors parallel to the yz-plane of the coordinate system, and a normal vector parallel to the x-axis. Thus, the y-axis and z-axis are parallel to the surface of the head at the point 2 and the x-axis is orthogonal to the surface of the head at the point 2.

(19) The user modeled with the phantom head of FIG. 1 is standing erect on the ground (not shown in the figure), and the ground plane is parallel to xy-plane. The torso axis from top to toe of the user is thus parallel to the z-axis, whereas the nose of the user is pointing out of the paper along the y-axis.

(20) The axis going through the right ear canal and the left ear canal is parallel to the x-axis in the figure. This ear to ear axis (ear axis) is thus orthogonal to the surface of the head at the points where it leaves the surface of the head. The ear to ear axis as well as the surface of the head will in the following be used as reference when describing specific configurations of the elements in one or more embodiments.

(21) Since the auricle of the ear is primarily located in the plane parallel to the surface of the head on most test persons, it is often described that the ear to ear axis also functions as the normal to the ear. Even though there will be variations from person to person as to how the plane of the auricle is oriented.

(22) The in the ear canal type of hearing aid will have an elongated housing shaped to fit in the ear canal. The longitudinal axis of this type of hearing aid is then parallel to the ear axis, whereas the face plate of the in the ear type of hearing aid will typically be in a plane orthogonal to the ear axis. The behind the ear type of hearing aid will typically also have an elongated housing most often shaped as a banana to rest on top of the auricle of the ear. The housing of this type of hearing aid will thus have a longitudinal axis parallel to the surface of the head of the user.

(23) A block-diagram of a typical (prior-art) hearing instrument is shown in FIG. 2. The hearing aid 20 comprises a microphone 21 for receiving incoming sound and converting it into an audio signal, i.e. a first audio signal. The first audio signal is provided to a signal processor 22 for processing the first audio signal into a second audio signal compensating a hearing loss of a user of the hearing aid. A receiver 23 is connected to an output of the signal processor 22 for converting the second audio signal into an output sound signal, e.g. a signal modified to compensate for a users hearing impairment, and provides the output sound to a speaker 24. Thus, the hearing instrument signal processor 22 may comprise elements such as amplifiers, compressors and noise reduction systems etc. The hearing instrument or hearing aid may further have a feedback loop 25 for optimizing the output signal. The hearing aid may furthermore have a transceiver 26 for wireless data communication interconnected with an antenna 27 for emission and reception of an electromagnetic field. The transceiver 26 may connect to the hearing instrument processor 22 and an antenna, for communicating with external devices, or with another hearing aid, located at another ear, in a binaural hearing aid system.

(24) However, also other embodiments of the antenna and the antenna configurations may be contemplated.

(25) The specific wavelength, and thus the frequency of the emitted electromagnetic field, is of importance when considering communication involving an obstacle. The obstacle is a head with a hearing aid comprising an antenna located closed to the surface of the head. If the wavelength is too long such as a frequency of 1 GHz and down to lower frequencies greater parts of the head will be located in the near field region. This results in a different diffraction making it more difficult for the electromagnetic field to travel around the head. If on the other hand the wavelength is too short, the head will appear as being too large an obstacle which also makes it difficult for electromagnetic waves to travel around the head. An optimum between long and short wavelengths is therefore preferred. In general the ear to ear communication is to be done in the band for industry, science and medical with a desired frequency centred around 2.4 GHz.

(26) It is envisaged that even though only a behind-the-ear hearing aid have been shown in the figures, the described antenna structure may be equally applied in all other types of hearing aids, including in-the-ear hearing aids, as long as the conducting segment, or first segment, is configured to guide the current in a direction parallel to an ear-to-ear axis of a user, when the user is wearing the hearing aid in the operational position and furthermore, equally applied to other body wearable devices, as long as the first segment is configured to guide the current in a direction orthogonal to a surface of the body, when the user is wearing the hearing aid in the operational position.

(27) In general, various sections of the antenna can be formed with many different geometries, they can be wires or patches, bend or straight, long or short as long as they obey the above relative configuration with respect to each other such that at least one conducting segment will carry a current being primarily parallel to the ear axis (orthogonal to the surface of the head 1 of the user at a point 2 in proximity to the ear) such that the field will be radiated in the desired direction and with the desired polarization such that no attenuation is experienced by the surface wave travelling around the head.

(28) The specific wavelength, and thus the frequency of the emitted electromagnetic field, is of importance when considering communication involving an obstacle. The obstacle is a head with a hearing aid comprising an antenna located closed to the surface of the head. If the wavelength is too long such as a frequency of 1 GHz and down to lower frequencies greater parts of the head will be located in the near field region. This results in a different diffraction making it more difficult for the electromagnetic field to travel around the head. If on the opposite side the wavelength is too short the head will appear as being too large an obstacle which also makes it difficult for electromagnetic waves to travel around the head. An optimum between long and short wavelengths is therefore preferred. In general the ear to ear communication is to be done in the band for industry, science and medical with a desired frequency centred around 2.4 GHz.

(29) In FIG. 3, a hearing aid 30 is shown schematically, the hearing aid 30 is a hearing aid of the type to be worn behind the ear, typically referred to as a behind the ear hearing aid, or a BTE hearing aid. The hearing aid 30 comprises a battery 31, a signal processor 32, a sound tube 33 connecting to the inner ear, a radio or transceiver 34, transmission lines 35, 36 for feeding the antenna 37. The hearing aid has a first side 38 and a second side 39. In one or more embodiments, the antenna proximate the first side of the hearing aid, i.e. a first part, 40 extends along or proximate the first side 38 of the hearing aid, and the antenna proximate the second side of the hearing aid, i.e. a second part, 41 extend along or proximate a second side 39 of the hearing aid 30. The first part of the antenna 40 may in one or more embodiments be a first resonant structure provided proximate the first side 38 of the hearing aid, and the second part of the antenna 41 may in one or more embodiments a second resonant structure provided proximate a second side 39 of the hearing aid. A first segment 42 short circuits the first part 40 and the second part 41 to provide a current bridge between the first side of the hearing aid and the second side of the hearing aid. The first part 40 is fed via transmission line 35 to feed point 43 and is thus an actively fed part 40. The second part 41 is fed via transmission line 36 to feed point 44 and thus forms a second actively fed part 41.

(30) In FIG. 4, a hearing aid 30 is shown schematically, wherein the width 45 of the first part 40 of the antenna 37 and the second part 41 of the antenna 37 is increased to increase the bandwidth of the antenna 37.

(31) In FIG. 5, a hearing aid 30 is shown schematically, wherein the antenna 37 is folded around the hearing aid 30, and thus the antenna extends along the first side 38 and the second side 39.

(32) FIG. 6 shows a further embodiment, wherein the hearing aid 30 has an antenna 37 having a first part 61 and a second part 62. The first part 61 and/or second part 62 are closed antennas having a width 63 allowing for an opening 64 to be formed within the antenna 37. The opening may allow for configuring the antenna so as not to extend over battery 31 and other larger electrical components. The first part 61 and/or the second part 62 may have any width and/or any shape configured according to hearing aid restrictions and/or antenna optimization. For the first part 61 and/or the second part 62 to be resonant structures, the circumference of the first and/or second parts 61, 62 is approximate lambda/2, where lambda is the resonance wavelength for the antenna 37. The first segment 65 short circuits the first part 61 and the second part 62 thereby creating a current bridge along the first segment 65. It is seen that the current bridge forms an elongated structure, and is positioned so that the elongated structure has a direction substantially orthogonal to the surface of the head, that is substantially parallel to an ear-to-ear axis of a user when the hearing aid is positioned in its operational position behind the ear of a user.

(33) FIG. 7 shows a further shape of the antenna 37, wherein the first part 38 and the second part 39 has a meander form of the antenna.

(34) It is envisaged that even though the first segment in FIGS. 3-7 is shown as being orthogonal to the surface of the head, also other configurations may be applied, so that the first segments form a non-perpendicular angle with the surface of the head, such as an angle of between 90 and 45, such as between 90 and 80. Hereby, the current will show at least a current component in the direction being orthogonal to the surface of the head. Furthermore, even though the first part 38, 61 and the second part 39, 62 are shown to be identical in FIGS. 3-7, it is envisaged that the shapes of the first part 38, 61 and the second parts 39, 62 may differ.

(35) In FIGS. 8a-e, schematic antennas 80 are shown, illustrating the feed points 83, 84 and the length of the first and second parts 38, 39, 61, 62 and the distances between the feed points 83, 84 and the short circuit.

(36) In FIG. 8a, an antenna 80 is shown. The antenna has a first part 85 and a second part 86 and a transceiver 82 located between the first side and the second side. First transmission line 87 feeds the first part 85 in a feed point 83 and second transmission line 88 feeds the second part 86 in a feed point 84. The first segment 89 extends from the first part 85 to the second part 86 and short circuits the first and second parts 85, 86. In that the antenna is balanced, the current in the short circuit will be maximized. The distance along the first part 85 between the first feed point 83 and the short circuit 89 is tailored to the desired impedance for the antenna, and the length l of the first part 85 is measured from the short circuit 89 to the free end of the antenna 90 and is lambda/4 in order for the first part to form a resonant antenna structure. Likewise the distance along the second part 86 between the second feed point 84 and the short circuit 89 is tailored to the desired impedance for the antenna, and the length l of the second part 86 is measured from the short circuit 89 to the free end of the antenna 91 and is lambda/4 in order for the second part to form a first resonant structure. The first resonant structure 85 is actively fed in the feed point 83 and second resonant structure 86 is actively fed in the feed point 84.

(37) FIG. 8b shows another embodiment, in which the first and second parts 85, 86 extends a length of lambda/4 on both sides of the short circuit.

(38) FIG. 8c shows a further embodiment, in which the antenna 80 extends around the sides of the hearing aid. The length of the sides is larger than lambda/4.

(39) FIG. 8d shows a further embodiment in which the short circuit 89 is provided on another side of the transceiver 82. Thus, the length of the first part 85 is measured from the short circuit 89 to the free end 90, and is lambda/4 to form a first resonant structure. Likewise, the length of the second part 86 is measured from the short circuit 89 to the free end 90, and is lambda/4 to form a second resonant structure. The antenna 80 may extend beyond the feed points 83, 84, however, the length of this extension is typically minimized.

(40) FIG. 8e shows an embodiment having a closed antenna structure 80 having a first part 95 and a second part 96. The length of the first and second closed part is lambda/2 to obtain a resonant structure. The widths of the first part 95 and the second part 96 may be tailored according to a desired antenna impedance.

(41) FIGS. 9a-b show how the length of the antenna may be measured along the current path in the first and second parts. In FIG. 9a, the first part is a wide antenna structure, and the length along a top part is lambda/8 and the length along a side part is lambda/8, thus having a total length along the current path of lambda/4.

(42) FIG. 9b shows an example of thinner first and second parts, wherein the length of the first part along the current path is lambda/4.

(43) FIGS. 10a-d shows the current along an antenna 40, 80. The current is seen to be zero at the free ends 90 of the antenna. It is furthermore seen that the maximum current is found along the first segment or the conducting segment 42, 89. As seen in FIG. 10a, showing a wide BTE hearing aid, that is a relatively long current bridge or first segment, the current exhibits two local maxima at each side of the short circuit with a slight decrease towards the middle. If the BTE hearing aid is a narrow hearing aid, the current may as shown in FIG. 10c, be substantially constantly high across the short circuit or the first segment. Thus, as is seen from FIGS. 10b and 10d, the current is maximized in a direction being substantially orthogonal to the side of the head.

(44) The first segment, or the conducting segment may have a have a length being between at least one sixteenth wavelength and a full wavelength of the electromagnetic field.

(45) FIGS. 11a-d show different embodiments of a partition plane 110 partitioning the antenna 80. The antenna 80 is seen to intersect the partition plane 110 at an intersection 111, thus, the antenna may intersect at least at a point 111, or along an axis of the antenna extending through the plane 110. The distances d1, d2 from the feed points 83, 84, to the intersection 111, respectively may be measured along the current path as shown in FIGS. 11a and 11c, or the distances d1 and d2 may be measured along the shortest distance from the feed points 83, 84, to the intersection 111.

(46) The partition plane 110 may be a symmetry plane 110 for the antenna so that the first part 85 of the antenna is symmetric with the second part 86 of the antenna with respect to the symmetry plane 110. The partition plane 110 may extend exactly mid through the hearing aid, or the partition plane may extend anywhere between a first side of the hearing aid and a second side of the hearing aid. In one or more embodiments, the partition plane extends through the receiver.

(47) Although particular embodiments have been shown and described, it will be understood that they are not intended to limit the claimed inventions, and it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the claimed inventions. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The claimed inventions are intended to cover alternatives, modifications, and equivalents.