Patent Application
20090214064
This invention relates to hearing aids and, in particular, to a hearing aid powered, at least in part, by radio frequency (RF) energy.
Deriving power from RF signals is more than one hundred years old. The crystal based receivers in the early days of radio were the first in a long line of devices powered by RF energy; e.g. see U.S. Pat. No. 918,618 (Way) and U.S. Pat. No. 1,748,435 (Adams et al.). Although still in use today among hobbyists, the crystal radio was replaced long ago by battery powered and line powered radios. The desire to use RF energy as a power source remained.
The invention of the transistor dramatically reduced the power needed by electronic devices and renewed interest in RF signals as a source of power. For example, U.S. Pat. No. 2,607,004 (Harris) discloses an RF powered walkie-talkie using diodes. U.S. Pat. No. 2,682,638 (Enabnit) discloses a signal powered bridge amplifier using active devices. U.S. Pat. No. 2,777,057 (Pankove) discloses several RF powered circuits with active devices. U.S. Pat. No. 2,851,592 (Webster, Jr.) discloses a carrier wave powered transceiver. U.S. Pat. No. 2,918,573 (Hollmann) discloses a “self-powered” detector-amplifier circuit. U.S. Pat. No. 2,997,535 (Brady et al.) discloses a remote control that receives RF power from a transmitter in a television and transmits a modulated or encoded signal for controlling the television. U.S. Pat. No. 3,118,145 (Nee) discloses a carrier powered paging system. U.S. Pat. No. 4,314,306 (Darrow) discloses a signal powered receiver for operating a relay. In all these patents, a transmitted signal is converted to electrical energy that is stored in a capacitor. Some of the circuits disclosed are broadband and some, like the crystal sets of old, are tuned to a narrow band of frequencies.
More recently, it has been proposed, if not actually accomplished, to transmit large amounts of power, e.g. from solar panels in synchronous orbit around the earth. A less grand proposal suggests transmitting power from a nearby transmitter; e.g. U.S. Patent Application Publication 2005/0104453 (Vanderelli et al.).
A hearing aid requires very little power, on the order of milliwatts. A problem is that a hearing aid requires a continuous supply of power. Batteries supply the power and new technology has increased battery life greatly, yet it is annoying to have to replace batteries. Hearing changes with time. It is unlikely that a single battery can last the same period of time, now or in the foreseeable future. Rechargeable batteries are a partial solution but require removal of the hearing aid and placement in a charger. Unless the user has two sets of hearing aids, the charging can be inconvenient.
Another problem caused by the need to replace batteries is the need to open the hearing aid. Moisture, wax, dirt, oils and so on, can work their way into a hearing aid, causing problems. Hearing aids can be made relatively impervious to ambient conditions. A hearing aid that is relatively impervious is also likely to be relatively difficult to open.
Another problem is that a hearing aid is physically small. Other factors being equal, signal strength is proportional to the size of the antenna and there is not a lot of room inside a hearing aid. U.S. Pat. No. 7,260,234 (Kasztelan et al.) proposes, for a battery powered hearing aid, winding an antenna around the outside of a hearing aid. The antenna is for communication.
In view of the foregoing, it is therefore an object of the invention to provide a hearing aid powered, at least in part, by radio frequency waves.
Another object of the invention is to provide a hearing aid that is rechargeable from radio frequency waves.
A further object of the invention is to provide a hearing aid that can be sealed.
The foregoing objects are achieved by this invention in which a hearing aid includes an antenna and is powered by one or more signals received by the antenna. At least some of the power for operating the hearing aid is derived from a received signal. Power not used for operation is used for charging a battery, if any, in the hearing aid. The signal can be modulated for one-way communication or there is two-way communication if the hearing aid includes a transmitter coupled to the same antenna or a second antenna.
A more complete understanding of the invention can be obtained by considering the following detailed description in conjunction with the accompanying drawings, in which:
The term “RF” is not intended to imply any particular frequency or band of frequencies but is intended to imply induced voltage or current; i.e. photovoltaic conversion such as disclosed in U.S. Pat. No. 5,210,804 (Schmid) is excluded. Also, there are government regulations covering the allocation of frequencies for various uses and the amount of power that can be emitted. Unless the context indicates otherwise, the mention of a particular frequency is not intended as a limitation on the invention but as a recognition of the regulations, which may vary from country to country.
A “speaker” converts electrical current into sound. In the hearing aid art, one often encounters the term “receiver” for such a device, which reads strangely to the uninitiated and is confusing in the context of this invention. “Electroacoustic transducer” is clumsy and pedantic. Thus, “speaker” is the term used for describing this invention. A “receiver” is a device that is coupled to an antenna for receiving electrical signals from the antenna.
In
In accordance with one aspect of the invention, hearing aid 10 includes antenna 21 located in cable 14 and coupled to a receiver on circuit board 17, which detects an RF signal on antenna 21 and stores energy from the RF signal on capacitor 22.
For good reception, an antenna should be at least one quarter wavelength long. At 3 GHz, the wavelength is 10 cm or approximately 2 inches. Thus, the embodiments of either
As with any radio signal, amplitude decreases with the square of the distance from the source. “Range” means the distance over which sufficient signal exists for powering a hearing aid, which is less than the distance over which a signal can be detected.
Plural antennas can be used to assure that at least one antenna is in an optimal position as transmitter 30 is carried. Position sensing circuitry, such as used in cameras for detecting “portrait” or “landscape” orientation, can be used n transmitter 30 for selecting the optimum antenna. Alternatively, or in addition, transmitter 30 can question the hearing aid (modulate the transmitted signal) and change antennas until it receives a response from the hearing aid, thereby indicating a preferred orientation.
As a portable unit, transmitter 30 is used as a remote control in accordance with another aspect of the invention. Transmitter 30 includes a few dedicated buttons or includes selection buttons, such as button 35, and display screen 37 for displaying suitable graphics or a menu. Thus configured, transmitter 30 provides a modulated signal that supplies power, data, and control for a hearing aid constructed in accordance with the invention. By way of example only, data includes an identification code and control includes volume up, volume down, and filter selection for various ambient conditions, e.g. library, restaurant, or theater. As a portable unit, transmitter 30 includes rechargeable batteries and preferably includes a power line input for table top operation.
Irrespective of the kind of hearing aid and the location of the antenna, the received signal is rectified and the energy is stored on a capacitor as voltage, as illustrated in
Integrated circuits can be made to consume very little power and operate on a supply voltage as low 1.2 volts. The antenna is coupled to a tuned circuit in the receiver. The tuned circuit reduces noise and improves efficiency at the carrier frequency; e.g. 1 GHz and above. As described above, the carrier signal can be modulated for one way or for two way communication between transmitter 30 and the hearing aid.
In accordance with one aspect of the invention, the RF energy supplements battery power. In accordance with another aspect of the invention, RF energy charges the battery when not being consumed during use. In accordance with yet another aspect of the invention, capacitor 22 (
The invention thus provides a hearing aid powered, at least in part, by radio frequency waves. The invention also provides a hearing aid that is rechargeable from radio frequency waves. Batteries can typically be charged many times. Thus, the invention also provides a hearing aid that can be sealed for greater reliability.
Having thus described the invention, it will be apparent to those of skill in the art that various modifications can be made within the scope of the invention. For example, the antenna can be wire or metal foil. In
