Patent Publication Number: US-2015078554-A1

Title: Wireless personal listening system and method

Description:
REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 13/329,397, filed Dec. 19, 2011, which claims priority from U.S. Provisional Patent Application Ser. No. 61/425,368, filed Dec. 21, 2010, the entire content of both of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to portable electronic devices and, in particular, to a wireless listening system and method that uses the standard FM band for transmission and reception. 
     BACKGROUND OF THE INVENTION 
     Portable music players such as MP3 players have become very popular. One problem is that the cords going from the music player to the earbuds or headphones can get in the way or become tangled, especially with activities such as jogging. 
     There are wireless earbuds but they are expensive and limited in functionality. Sennhieser, for example, now offers a system called the MX W1 that retails for about $500 and uses a small transmitter to send modulated audio signals to wireless in-ear receivers. While the system is digital and no doubt offers high quality sound reproduction, the transmitter is somewhat large and the receivers can only be used with that transmitter. 
     SUMMARY OF THE INVENTION 
     This invention is directed to a personal listening system which, in the preferred embodiments, uses the standard FM band for transmission and reception. This offers significant advantages, including the fact that the earbuds or other listening units can be used as an independent FM stereo receiver without the need for the local transmitter, thereby freeing up the music player for other purposes such as book reading, video watching, telephonic communications, and so forth. 
     The system includes a base unit and physically separate, entirely self-contained, battery-operated right- and left-ear listening units. The base unit includes a source of an audio signal, a user control for selecting an FM frequency, and an output for outputting a signal representative of the selected FM frequency. The base unit further includes a modulator for modulating the audio signal onto the selected FM frequency as a stereo signal with encoded right and left channels, and an FM stereo transmitter for wirelessly transmitting the modulated audio signal over the selected FM frequency. 
     Each listening unit includes an input for receiving the signal representative of the selected FM frequency, an FM stereo tuner, and apparatus for tuning the FM tuner to the selected FM frequency of the base unit. Each listening unit further includes a demodulator for demodulating the audio signal from the selected FM frequency, an amplifier for amplifying the audio signal, and a transducer for converting the audio signal into sound to be heard by a listener. In accordance with the invention, however, the right-ear unit only amplifies the right channel of the FM stereo signal, and the left ear unit only amplifies the left channel of the stereo signal. 
     The base unit may be a digital music player, book reader, video player, smart cellular telephone, or any other portable device with a stereo sound generator. The base unit may further include a display for displaying the selected FM frequency. The base unit may be a self-contained or integrated unit or a device that couples to a digital music player, smart cellular telephone or other base unit to receive the audio signal therefrom. 
     The right- and left-ear listening units may be any type of on-ear, in-ear or around-ear sound delivery devices including “earbuds,” headphones or earphones. The right- and left-ear units may physically dock onto the base unit to receive the signal representative of the selected FM frequency from the base unit, in which case the base unit may recharge the batteries in the right and left ear units while docked. The right- and left-ear units may receive the signal representative of the selected FM frequency from the base unit through a wireless or wired connection such that the wires deliver the audio signal directly to the right and left ear units while interconnected. The wires may also recharge the batteries in the listening units while connected. 
     The right- and left-ear units may receive the signal representative of the selected FM frequency from the base unit through a wireless Bluetooth connection or other short-range broadcast at a frequency other than the selected FM frequency. Alternatively, the listening units may receive the signal representative of the selected FM frequency from the base unit through a radio frequency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a preferred embodiment of the invention; 
         FIG. 1B  shows listening units removed to receive FM stereo sound from a base unit; 
         FIG. 1C  illustrates an alternative docking mechanism; 
         FIG. 1D  illustrate yet a further station programming technique according to the invention, in this case a short-range broadcast of the frequency programming signal; 
         FIG. 2  depicts a separate transmitter used in conjunction with a non-FM-transmitting music player; 
         FIG. 3  shows a different configuration wherein the transmitter unit connects to a larger audio source such as a laptop computer; and 
         FIG. 4  illustrates how the base unit has been used to program the listening units to an active FM stereo station. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention resides in a wireless listening system which, in the preferred embodiments, uses the standard FM band for transmission and reception. This offers significant advantages, including the fact that the in- or on-ear units can be used as an independent FM stereo receiver without the need for the local transmitter, thereby freeing up the music player for other purposes such as book reading, video watching, telephonic communications, and so forth. 
     As used herein, “earbuds” should be taken to include any type of on-ear, in-ear or around-ear sound delivery devices including ‘headphones,’ ‘earphones,’ and the like, so long as the right- and left-ear components can be entirely wireless as described herein. Also “music player” should be understood to include any kind of portable electronic device that uses or would benefit from stereophonic listening, including radios, telephones, video players, book readers, and so forth. Further, although the preferred embodiments use FM stereo, the invention does not preclude over broadcasts, including AM, TV audio, shortwave, or satellite reception. 
       FIG. 1A  illustrates a preferred embodiment of the invention generally at  100 . The system includes a source of an audio signal such as music player  102 . In the embodiment of  FIGS. 1A-1D , the unit  102  includes an FM stereo transmitter that sends the same signal  120  to right earbud  112  and left earbud  114 . The unit  102  may also include a display  110  and a user control  104 . Earbud  112  may include an in-ear tip  122 , and earbud  114  may include ear tip  124 . Both earbuds  112 ,  114  include FM receivers, demodulators and audio amplifiers, but in the case of a stereo transmission, the right earbud only delivers right-channel audio to the right ear and the left earbud only delivers left-channel audio to the left ear. 
       FIG. 1A  shows the listening units  112 ,  114  docked to the audio player  102  through electrical connections not shown. Using the controls  104 , the user has selected an unused FM frequency, in this case, 92.7 MHz. Through the docking connections, the units  112 ,  114  are now programmed to receive audio modulated over this selected FM frequency, which is also shown on the display. When the units  112 ,  114  are removed, as shown in  FIG. 1B , the user can listen to the audio transmitted by the base unit  102  over the selected FM frequency. Again, the right unit  112  only delivers right-channel audio to the right ear and the left unit  114  only delivers left-channel audio to the left ear. 
     Each earbud may have nearly identical circuitry, preferably using a single-chip FM stereo circuit such as the TEA5990 FM-RDS chip set from NXP Semiconductors (The Netherlands), which offers reception over a wide tuning range (70 to 108 MHz, including the 70-MHz China band) with Stereo Noise Cancelling (SNC) as well as built-in Auto Search and Store for up to 32 channels with dynamic adjacent channel suppression. The chip also supports the I2C-bus and the SPI-bus (3- or 4-wire format), while a digitally controlled algorithm facilitates seamless coexistence with GSM, Bluetooth, Wi-Fi and WiMAX. Although the TEA5990 chip outputs both right and left audio channels, each listening unit according to the invention would require only one audio amplifier, such the unit for the right ear only amplifies the right channel and the using for the left ear only amplifies the left channel. 
       FIG. 1C  illustrates an alternative docking mechanism. In this case wiring  130  connects the base unit to the listening devices though connectors  132 ,  134 ,  136 . This configuration offers the advantage that the cable  130  can be used for a conventional, hard-wired interconnect, facilitating stereo listening without the need for wireless transmission. This may be advantageous in areas where it is difficult or impossible to find a clear, unused FM channel. It is assumed that the listening units are programmed over the wiring  130  when plugged in or perhaps when optional “program frequency” buttons  140 ,  142  are depressed on the listening units. Regardless, the frequency programming signal is preferably a digitally encoded signal that is delivered to the listening units when initially plugged in or at a time or on a frequency which does not interfere with listening. 
     In the preferred embodiments each listening unit also includes its own rechargeable battery to power operation. In the embodiments wherein the listening units are physically docked ( FIGS. 1A ,  1 C), the batteries may be recharged while the listening units are docked. 
       FIG. 1D  illustrate yet a further station programming technique according to the invention, in this case a short-range broadcast  148  of the frequency programming signal. Such a signal may be a low-frequency magnetic signal, Bluetooth, or any other short-range transmission. Once the frequency is set on the base unit, optional “program” buttons  150 ,  152  may be depressed on the listening units. Regardless of the frequency programming method, once the listening units  112 ,  114  can receive a stereo signal from the base unit, a user can enjoy wireless audio over the selected frequency. 
     In some embodiments, the definition of “music player” includes a separate transmitter  202  used in conjunction with a non-FM-transmitting music player  200  shown in  FIG. 2 . In this case, user controls  204  would be used for frequency programming. Otherwise, operation would be the same as that described with a base unit having a built-in RF transmitter.  FIG. 3  shows a different configuration wherein the transmitter unit  302  connects to a larger audio source such as a laptop  300 . Such an embodiment is convenient for in-flight movie watching, for example 
     As an alternative to user selection of an unused frequency, the base unit  102  (or  202 ) may automatically select a “best” unused frequency. For example, the base unit may store a list of unused frequencies as a function of geographical location, with the unit using GPS, WiFi, or cell phone infrastructure to determine location and choose a frequency. The base unit may also test frequencies to find a clear unused channel and use that frequency for programming. This approach offers the advantage of continuing to search for “better” unused frequencies in a background mode and automatically switch to a different frequency if noise is encountered on the currently selected frequency. 
     An advantage of the invention is that the user can also program the listening units to receive a desired, active station, in which case the base unit would not to transmit on the selected FM station. This allows a user to listen to an over-air broadcast, including an FM stereo station, without having to carry the base unit. As shown in  FIG. 4 , the base unit has been used to program the listening units to “100.3,” an active FM stereo station. Once programmed, the listening units receive the FM station off-air and not through the base unit, which might jam the signal. When choosing an active signal, the base unit may be instructed not to transmit using the user controls.