WO1998052295A1

WO1998052295A1 - Short-range wireless audio communications using induction

Info

Publication number: WO1998052295A1
Application number: PCT/US1998/007785
Authority: WO
Inventors: Vincent Palermo; Patrick J. Cobler; Neal R. Butler
Original assignee: Aura Communications, Inc.
Priority date: 1997-04-23
Filing date: 1998-04-22
Publication date: 1998-11-19

Abstract

A communications system includes portable stereo headphones having an inductive receiver and a portable audio source. The source generates a magnetic field based on a modulated audio signal. The inductive receiver includes one or more transducers and associated electronics for receiving the magnetic field and recovering the audio signal. The portable source (e.g., a portable compact disc or tape player, or a portable radio) modulates the audio signal and then generates the magnetic field using one or more transducers and associated electronics. The audio signal typically is music and/or voice recorded on a magnetic tape or on a compact disc. The headphones can be provided in various configurations including an arrangement worn over the head with speakers that cover or partially cover the ears of the user or an arrangement of the concha type in which the speaker fits into one or both of the user's ears without a strap across the head. In the strap-across-the-head configuration, the inductive receiver can be disposed in or on the strap, or in or on one of the speakers. In the concha type configuration, the inductive receiver can be encapsulated into the small device that gets inserted into the user's ear(s). Because only a relatively small amount of power is required to receive and generate magnetic induction fields, the power sources in the headphones and the portable source needed to power the inductive receiver and to generate the magnetic field, respectively, are relatively small in size and weight.

Description

SHORT-RANGE WIRELESS AUDIO COMMUNICATIONS USING INDUCTION

Cross-Reference to Related Applications

This is a continuation-in-part of: (1) U.S. patent application serial number 08/444,017, filed May 18, 1995; and (2) U.S. patent application serial number 08/696,812, filed August 13, 1996. The entirety of each of these two related U.S. patent applications is hereby incorporated hereinto by reference.

Technical Field

This invention relates to short-range wireless communications and, more particularly, to the use of inductive coupling. Background Information

Headphones can be used to listen to music or other audio information. Headphones typically are connected to an audio source (e.g., a tape or compact disc player or a radio) by a wire or cable. A wearer of such headphones has limited mobility due to the wired connection to the audio source. Summary of the Invention

The invention relates to a short-range, wireless communications system including a miniaturized portable transceiver unit and a base unit transceiver. The miniaturized portable transceiver unit sends and receives information through magnetic induction to the base unit, which may also be portable (i.e., easily carried by hand by a single person). Similarly, the base unit sends and receives information through magnetic induction to the portable transceiver. The information generally can be any type of information including voice, audio, data, music, and/or video. The use of magnetic induction fields limits interference between a plurality of systems operating in close proximity to each other, and it reduces the power requirements (e.g., the battery or batteries in the units can be smaller in size and weight) which allows smaller size units and greater convenience as compared to other types of communications systems.

Each of the base unit and the portable transceiver units includes one or more transducers. Each of the transducers preferably is a rod antenna such as a ferrite rod within a wire coil. Either or both of the units can include multiple transducers arranged in a variety of configurations to generate multiple magnetic fields, and in such multiple-transducer embodiments a diversity circuit is used to receive and/or transmit on at least one of the transducers. For example, three orthogonally arranged transducers can be used in the base unit, the portable unit, or both. For each unit, whatever the physical arrangement of that unit's plurality of transducers with respect to each other, the multiple fields generated substantially eliminates mutual inductance nulls between the two units which typically occurs at certain positions in a generated magnetic field. In one embodiment, the multiple transducers are selectively operated based upon a strongest signal in order to limit power consumption. In general, in one aspect of the invention, portable headphones are provided having at least one inductive receiver for receiving a magnetic field based on a modulated audio signal. The inductive receiver includes one or more transducers and associated electronics for receiving the magnetic field and recovering the audio signal to provide it to a wearer of the headphones. The audio signal preferably is a stereo audio signal. A portable source (e.g., a portable compact disc player, a portable tape player, a portable radio, some combination of such devices, etc.) modulates the audio signal and then generates the magnetic field based on the modulated audio signal by using one or more transducers and associated electronics. Typically, the portable source will modulate the audio signal on a carrier and then drive at least one of the transducers with the modulated audio signal to generate the magnetic field. The information sent from the portable source to the headphones typically is music and/or voice recorded on a magnetic tape or on a compact disc (CD). The portable headphones, which preferably are stereo headphones, can be provided in a variety of configurations including an arrangement worn over the head with speakers that cover or partially cover the ears of the user or an arrangement of the concha type in which a speaker fits into one or both of the user's ears without a strap across the head. In the strap-across-the-head configuration of the headphones according to the invention, the inductive receiver can be disposed in or on the strap or in or on one of the speakers. In the concha type configuration, the inductive receiver can be encapsulated into the small device that gets inserted into the user's ear(s). Whatever the configuration, the portable headphones and source typically are each provided with a power source (e.g., a small battery) for powering the inductive receiver and the magnetic field transmitter, respectively. Because only a relatively small amount of power is required to receive and generate magnetic induction fields, the power sources in the portable headphones and the portable source needed to power the inductive receiver and to generate the magnetic field, respectively, are relatively small in size and weight.

The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims.

Brief Description of the Drawings

In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. FIG. 1 is a schematic illustration of a wireless communication system according to the invention.

FIG. 2 is an illustration of a telephone handset as a base unit in the communication system of FIG. 1.

FIG. 3 is an illustration of a headset utilized as a portable device in the communication system of FIG. 1.

FIG. 4 is a schematic illustration of a transducer and electronics of a portable device according to the invention.

FIG. 5 is a schematic illustration of a transducer and electronics of a base unit according to the invention. FIG. 6 is an illustration of another transducer configuration for the base unit.

FIG. 7 is a diagram of an audio communications system according to the invention.

FIG. 8 is a schematic of an inductive receiver used with headphones of the audio communications system of FIG. 7.

Description

Referring to FIG. 1 , a short-range magnetic communication system 1 includes a portable device 2 and a base unit 1 which connects to a long-range communication network 14. Contained within each of the base unit 1 and the portable device 2 is a short-range miniaturized magnetic induction transceiver 1 1, 12 which can simultaneously transmit and receive communications signals 13. These signals may be voice, audio, data, or video. The communications network 14 may be any network in which it would be desirable for these signals to be communicated over a terminal link without wires, such as a telephone network, personal communications (PCS) network, special mobile radio (SMR) network, computer system or network, and video conferencing systems. The base unit 1 may any part of the communications network 14 from which it would be desirable to communicate to another device without wires; for example, it may be a telephone handset, PCS handset, SMR handset, walkie-talkie, computer or computer peripheral devices, Personal digital assistant (PDA), or video game controller. The portable device 2 may be any device from which it would be desirable to communicate without wires to a communications network; for example, it may be a telephone headset or handset, portable computer or computer peripheral device, headphone, or video input device.

Referring to FIG. 2, one example of the base unit 1 is a portable telephone 10 having a plurality of number buttons 15 and a plurality of function buttons 16. A retractable antenna 17 communicates with a cellular telephone network or a cordless telephone base unit. The portable telephone 10 operates in a manner similar to that of an ordinary cellular or cordless telephone handset. Signals are sent to and received from the telephone network in an ordinary manner. The portable telephone 10 includes a transducer system 30 which communicates by magnetic induction with headset 20, which operates as the portable device 2, to provide the outputs and inputs to the portable telephone 10. The portable telephone 10 may also include a mouthpiece or earpiece (not shown) as in a regular telephone handset, allowing the user to choose between a conventional method of operation and a hands-free use afforded by the headset 20.

The portable device 2 as a headset 20 is shown more fully in FIG. 3. It includes a body portion 23 which houses a transducer 40 and processing circuitry. A speaker 22 is connected to the circuitry within the body 23. An earpiece 21 next to the speaker 22 fits in the user's ear to hold the unit in place and to allow the user to hear sounds from the speaker. A microphone boom 24 extends from the body 23 several inches in order to place a microphone 25, located at the end of the boom 24, close to the user's mouth. Alternatively the transducer 40 may be housed in the boom 24. A rechargeable battery 51 is also housed in the body 23 of the headset 20 to provide power to the headset. Other features may be optionally included in the headset 20, such as switcher or buttons for manually activating different modes. For example, a capacitive switch or push-button could be used to cause the headset 20 to transmit a control signal to the portable phone 10 to activate muting of the microphone. The portable phone 10 may include a receptacle 19 for receiving and holding the headset 20. Depositing the headset in the receptacle can provide a variety of functions, in addition to maintaining the headset 20 and portable phone 10 together. A switch can be disposed in the receptacle to terminate the telecommunication when the headset 20 is inserted or initiate the telecommunication when it is removed. The receptacle may also include connections to recharge the battery 51 in the headset 20.

The base unit 1 and portable device 2 communicate through amplitude modulation of inductive fields, although other modulation methods such as frequency or phase modulation could be employed. During use, the distance between the portable device 2 and the base unit 1 typically is short. Since the distance is short, only an inductive field is necessary, and little or no radiation occurs. This limits the operating power, which allows a smaller size and weight for the rechargeable battery 51 and, thus, the portable device 2. Furthermore, it limits interference between systems operating in close proximity. Therefore, interference rejection circuitry may be limited or not necessary in the portable device 2. Referring to FIG. 4, for the transducer system in the portable device 2, the transducer 40 preferably includes a ferrite rod transducer having a ferrite rod 41 within a wire coil 42. The wires from the transducer 40 are connected to a transceiver 27 having transmitter electronics 28 and receiver electronics 29. The transceiver 27 connects to the portable device electronics 26, the nature of which is dependent upon the function of the portable device 2. In the example of the portable device as a headset 20, the portable device electronics would connect to a speaker 22 and a microphone 25. Transmission and reception can occur at different frequencies, which permits full duplex operation. Alternatively, separate transmitting and receiving transducers can be used.

Referring to FIG. 5, for the base unit 1 configuration, the transducer system 30 includes three orthogonally disposed ferrite rod transducers, each including a ferrite rod 31, 32, 33 and a respective coil 34, 35, 36. The use of the orthogonally disposed transducers overcomes the occurrence of mutual inductance nulls in the resulting inductive fields. The three transducers are connected to multiplexer electronics 60 for selecting one or more of the transducers for transmission and reception. Circuitry may be used to select the transducer or transducers having the strongest signal for transmission and reception to reduce the total power consumption of the device. The transmitter electronics 61 and receiver electronics 62 provide for processing of the communications signals from the base unit electronics 70 and the portable device 2. As discussed above, for a portable telephone 10, the conventional telephone speaker 71 and mouthpiece 72 may be eliminated so that the portable telephone 10 solely uses the headset 20 through the transducer system for communicating to the user. Switching circuitry (not shown) would be included to select between the speaker 71 and microphone 72, and the headset 20. The switching circuitry could be included in the receptacle 19 so that the speaker 71 and microphone 72 are disconnected when the headset 20 is removed.

Referring to FIG. 6, in another embodiment of the transducer system 30 for the base unit 1, one of the ferrite rod transducers is replaced with a loop coil transducer 37. A loop coil transducer can replace any or all of the ferrite rod transducers. The loop coil transducer 37 is disposed in the plane of the remaining ferrite rod transducers. This creates a transducer system having a decreased depth. As shown in FIG. 2, the three orthogonal transducers can be placed in a corner along the sides of the portable telephone 10. Alternatively, the loop coil transducer 37 could be placed along the back of the portable phone 10, so that it could made thinner. Additionally, the transmission system can be used for charging the battery 51 of the portable device 2. The base unit 1 includes a battery charger signal generator 52 connected to the transmitter 61. This generator 52 produces a recharging signal which is sent through one of the ferrite rod transducers in the base unit 1 to the ferrite rod transducer 40 of the portable device 2. Since, in the telephone embodiment of FIG. 2, the headset 20 and transducer 40 have a known orientation when in the receptacle 19, only one transducer in the portable telephone 10 needs to be energized to transmit inductively the recharging signal. As shown in FIG. 3, the wires from the transducer 40 in the portable device 2 are connected to a battery charger 50 which is used to charge the battery 51.

Although the communication system has been illustrated in connection with a concha type headset 20 and a cellular or cordless telephone handset 10 as a base unit 1, it is readily adaptable for other types of headsets and uses. The headset can be of the over-the-head type, over-the-ear type, or binaural type. The system can be used as a wireless connection to a conventional desktop telephone. Such a system would operate in the manner discussed above with the cordless handset. Since several such units may be used in close proximity, interference may become more of a problem. Therefore, the system can be designed to operate on various frequencies and can select frequencies for the transmission and reception which are unlikely to have significant interference. Similarly, the system can be used with a computer, either stationary or portable, for voice data entry, sound transmission, and telephone functions. The system can also be used with other types of communication systems including personal digital assistants (PDAs), cordless phones, PCS and SMR cellular phones, two way (e.g., video games), two-way half duplex (e.g., walkie-talkies and CBs), or two-way full duplex (e.g., phones). When the base unit is stationary and the user is likely to be at certain locations relative to the base unit, fewer transducers may be used in the base unit without encountering mutual inductance nulls. Alternative transducer systems may also be used for generating the inductive fields. Specifically, rather than a single transducer for transmission and reception on different frequencies, separate transducers may be used.

Other embodiments of a communications system according to the invention also are possible. For example, referring to FIG. 7, the principals of the invention can be applied to an audio communications system 100 that includes a portable audio source 102 and portable, wireless headphones 106. The portable audio source 102 generates and transmits a magnetic field 104 based on an audio signal, and the portable headphones 106 receive the magnetic field 104 and recover the audio signal to provide it to a listener (i.e., a wearer of the headphones 106). The magnetic field 104 is a local field, and the distance between the source 102 and the headphones 106 typically must be about 3 meters or less for the headphones 106 to receive the field 104 and recover the audio signal. Unlike traditional headphones, the headphones 106 of the invention include an inductive receiver 112 for receiving the magnetic field 104 and recovering the audio signal on which the. field 104 is based. While the headphones 106 can be provided in a variety of configurations, they generally will include two speakers 108, 110 (for providing stereo sound) and some mechanism for disposing the speakers near or in a user's ears. For example, in one embodiment, the headphones 106 are worn over the user's head and the speakers, which are connected by a strap 114, cover or partially cover the ears, as shown in FIG. 7. In this strap-across-the-head configuration of the headphones 106, the inductive receiver 1 12 can be disposed in or on the strap 1 14 or in or on one of the speakers 108, 1 10. In another embodiment, a concha type arrangement is used in which a speaker fits into one or both of the user's ears without a strap across the head. This concha configuration can be realized as a device like that shown in FIG. 3 but without the microphone 25 or the boom 24. This concha device would include the body portion 23 which includes the transducer 40, processing circuitry (described below with reference to FIG. 8), the speaker 22, and the earpiece 21. In a concha type configuration, the inductive receiver 112 thus would be encapsulated into the small device that gets inserted into the user's ears. In this configuration of the headphones 106, one such small device would be provided for the user's left ear and another small device would be provided for the user's right ear, and each such device typically will include a separate inductive receiver encapsulated therein. Further details of the inductive receiver 112 are disclosed below with reference to FIG. 8.

Still referring to FIG. 7, the portable source 102 typically includes some type of player 116 (e.g., a Walkman™, a Discman™, a transistor radio, or some other type of device that plays recorded or received audio information such as music and/or voice) and additional equipment 120 according to the invention. The additional equipment 120 can be provided as an add-on/plug-in module or as an integral part of the player 116, and this additional equipment 120 is an inductive transmitter that includes a magnetic field modulator 118 and a transducer system 119. The modulator 118 preferably is a stereo modulator for receiving an audio signal (preferably stereo) from the player 116 and modulating the stereo audio signal on a carrier. In one embodiment, the carrier is at a frequency of 4MHz. The modulation performed by the modulator 118 can be amplitude modulation (AM), frequency modulation (FM), phase modulation (PM), or generally any other type of modulation scheme. The modulator 118 drives the transducer system 119 with the modulated audio signal. The transducer system 119 preferably includes one, two, or three rod antennas such as those shown and described above with reference to FIGS. 4-6. Also, rod antennas are preferred because they are directional and can be made positionable by ' a user in order to direct the antenna in the orientation that provides the best results.

Referring to FIG. 8, the inductive receiver 112 of the headphones 106, whatever the configuration of the headphones 106, includes a transducer system 122 for receiving the magnetic field 104 generated by the inductive transmitter 120 of the portable source 102 and electronics for demodulating the modulated audio signal on which the magnetic field 104 is based. The electronics of the inductive receiver 1 12 include an antenna diversity circuit 124 and a demodulator 126 for receiving the signals from the transducer system 122, processing those signals to recover the original stereo audio signal, and providing the left and right channels of the recovered stereo audio signal to the left and right speakers 108, 1 10 of the portable headphones 106 in accordance with the invention. In the disclosed embodiment, the transducer system 122 includes three orthogonally arranged rod antennas (such as that shown and described above with reference to FIG. 5), and the diversity circuit 124 in the inductive receiver 112 of the wireless stereo headphones 106 receives the x, y, and z components of the magnetic field 104 from the orthogonally-disposed set of coils 122 and then phases and sums those three components together. In another embodiment, the transducer system can be as just described, but the diversity circuit 124 selects one of the components (i.e., one of the orthogonally-disposed coils 122) from which to receive the magnetic field 104 instead of receiving all three of the components. This selection could be done by the diversity circuit 124 based on the strength of the field 104 received by each of the rod antennas in the transducer system 122. In still other embodiments, the transducer system 122 is not three transducers but instead a single transducer or two transducers. Regardless of the number of transducers in the system 122 and physical arrangement of those transducers with respect to each other, the signal from the transducer system 122 is passed to and processed by some type of receiving circuit like the diversity circuit 124 or the other electronics described hereinabove, and then the processed signal is then passed to the demodulator 126 which demodulates the signal to recover the original stereo audio signal that was modulated and transmitted by the portable source 102. Also, a rod antenna generally is the preferred type of transducer because it is directional and can be made positionable by a user in order to direct the antenna in the orientation that provides the best reception.

The portable headphones 106 and the portable source 102 typically are each provided with a power source (e.g., a small battery pack) for powering the inductive receiver 112 and the magnetic field transmitter 120, respectively. Because only a relatively small amount of power is required to receive and generate magnetic induction fields, the power sources in the portable headphones 106 and the portable source 102 needed to power the inductive receiver 112 and the inductive transmitter 120, respectively, are relatively small in size and weight. For example, the inductive transmitter 120 and the inductive receiver(s) 112 each can include a rechargeable battery pack of one or more NiCad rechargeable batteries, and these power packs could each have a maximum size of about 0 2"(height) by 0 4"(diameter). As for the size of the inductive receiver 1 12, it is miniature The inductive receiver 1 12 is described above as being of a size capable of being encapsulated into a small concha type earphone device such as the body 23 of FIG. 3 As an example, the inductive receiver 112 can be fabricated on a chip of 7mm x 7mm The inductive transmitter 120 including the transducer system 1 19 can be incorporated into a small package about 0.5" by 1.0" by 0 5", and the size of the entire portable source 102 will depend on the dimensions of the player 1 16

As an example of how a possible embodiment of the audio communications system 100 shown and described above with reference to FIGS. 7 and 8 might be used as a product by a user, consider the following description. A user can wear the portable source 102 on his or her belt or pants. The user is provided with headphones 106 of the concha type and thus inserts a left audio channel concha type receiving earphone device in the left ear and a right audio channel concha type receiving earphone device in the right ear. The user might be able to adjust one or more positionable rod antennas on the portable source 102 to point generally toward the headphones 106. For example, a left channel transmitting rod antenna could be user-oriented to point to his or her left ear and a right channel transmitting rod antenna could be pointed to the right ear, or a single transmitting rod antenna could be pointed generally in the direction of the user's head. The user might then adjust any positionable receiving rod antennas on the earphone devices to point in the direction of the portable source disposed on the user's belt or pants. There is no wire or cable connecting or coupling the portable source to the headphones 106, or the two concha type earphone devices to each other. This is a completely wireless system in accordance with the invention. It also is a short-range audio communications system in that the use of magnetic induction fields makes transmissions from the source 102 to the headphones 106 ineffective when the source 102 and the headphones 106 are further than about 3 meters from each other. Variations, modifications, and other implementations of what is described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the invention is to be defined not by the preceding illustrative description but instead by the spirit and scope of the following claims.

What is claimed is:

Claims

Claims 1. System for short-range wireless communications, comprising: a first portable unit including an inductive transmitter for modulating an audio signal and for generating a magnetic field based on the modulated audio signal; and a second portable unit including an inductive receiver for receiving the magnetic field generated by the inductive transmitter of the first portable unit and for demodulating the modulated audio signal on which the magnetic field is based.

2. The system of claim 1 wherein: the inductive transmitter of the first portable unit includes at least one transmitting transducer; and the inductive receiver of the second portable unit includes at least one receiving transducer.

3. The system of claim 2 wherein: the at least one transmitting transducer comprises a transmitting rod antenna; and the at least one receiving transducer comprises a receiving rod antenna.

4. The system of claim 3 wherein the inductive receiver of the second portable unit includes: an antenna diversity circuit coupled to the at least one receiving rod antenna; and a demodulator circuit coupled to the antenna diversity circuit.

5. Apparatus for short-range wireless reception, comprising: headphones, adapted to be portable and worn by a user, for providing audio to the user when disposed near a source of a magnetic field based on an audio signal; and an inductive receiver coupled to the headphones and comprising a transducer for receiving the magnetic field and providing a receive signal related to the magnetic field, and electronics, coupled to the transducer, for receiving the receive signal from the transducer, recovering the audio signal, and providing the audio signal to the headphones.

6. The apparatus of claim 5 wherein the inductive receiver further comprises a plurality of the transducers, and the electronics selects one of the transducers to provide the receive signal.

7. The apparatus of claim 5 wherein the inductive receiver further comprises a plurality of the transducers, and the electronics receives the receive signal from at least one of the transducers.

8. The apparatus of claim 5 wherein the inductive receiver further comprises a plurality of the transducers, and the electronics receives the receive signals from at least two of the transducers, recovers the audio signal therefrom, and provides the audio signal to the headphones.

9. The apparatus of claim 5 wherein the electronics recovers a left channel of the audio signal and a right channel of the audio signal and provides the left and right channels to the headphones.

10. Apparatus for short-range wireless communications, comprising: a portable source for generating a magnetic field based on an audio signal; and portable headphones adapted to be worn by a user and comprising an inductive receiver having a transducer for receiving the magnetic field and outputting a receive signal related to the magnetic field, and electronics for receiving the receive signal from the transducer, recovering the audio signal, and providing the audio signal to the headphones.

11. Short-range wireless portable headphones, comprising: an inductive receiver including a transducer for receiving a magnetic field based on an audio signal and for outputting a receive signal related to the magnetic field, and electronics for receiving the receive signal, recovering the audio signal, and outputting the recovered audio signal.

12. A method for short-range wireless reception, comprising: providing portable headphones including an inductive receiver; receiving, with the inductive receiver, a magnetic field based on an audio signal; processing the received magnetic field with the inductive receiver to recover the audio signal; and outputting the recovered audio signal to the portable headphones.

13. The method of claim 12 wherein the receiving step comprises receiving, with the inductive receiver, the magnetic field which is based on a stereo audio signal.