Abstract:
A wireless digital audio system includes a portable audio source with a digital audio transmitter operatively coupled thereto and an audio receiver operatively coupled to a headphone set. The audio receiver is configured for digital wireless communication with the audio transmitter. The digital audio receiver utilizes fuzzy logic to optimize digital signal processing. Each of the digital audio transmitter and receiver is configured for code division multiple access (CDMA) communication. The wireless digital audio system allows private audio enjoyment without interference from other users of independent wireless digital transmitters and receivers sharing the same space.

Description:
[0001]    This continuation application claims the benefit of U.S. patent application Ser. No. 10/648,012 filed Aug. 26, 2003, which claimed benefit from U.S. patent application Ser. No. 10/027,391, filed Dec. 21, 2001, for “Wireless Digital Audio System,” published under US 2003/0118196 A1 on Jun. 26, 2003, now abandoned, both of which are incorporated herein in their entirety by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to audio player devices and more particularly to systems that include headphone listening devices. The new audio system uses an existing headphone jack (i.e., this is the standard analog headphone jack that connects to wired headphones) of a music audio player (i.e., portable CD player, portable cassette player, portable A.M./F.M. radio, laptop/desktop computer, portable MP3 player, and the like) to connect a battery powered transmitter for wireless transmission of a signal to a set of battery powered receiving headphones. 
         [0003]    Use of audio headphones with audio player devices such as portable CD players, portable cassette players, portable A.M./F.M. radios, laptop/desktop computers, portable MP3 players and the like have been in use for many years. These systems incorporate an audio source having an analog headphone jack to which headphones may be connected by wire. 
         [0004]    There are also known wireless headphones that may receive A.M. and F.M. radio transmissions. However, they do not allow use of a simple plug in (i.e., plug in to the existing analog audio headphone jack) battery powered transmitter for connection to any music audio player device jack, such as the above mentioned music audio player devices, for coded wireless transmission and reception by headphones of audio music for private listening without interference where multiple users occupying the same space are operating wireless transmission devices. Existing audio systems make use of electrical wire connections between the audio source and the headphones to accomplish private listening to multiple users. 
         [0005]    There is a need for a battery powered simple connection system for existing music audio player devices (i.e., the previously mentioned music devices), to allow coded digital wireless transmission (using a battery powered transmitter) to a headphone receiver (using a battery powered receiver headphones) that accomplishes private listening to multiple users occupying the same space without the use of wires. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is generally directed to a wireless digital audio system for coded digital transmission of an audio signal from any audio player with an analog headphone jack to a receiver headphone located away from the audio player. Fuzzy logic technology may be utilized by the system to enhance bit detection. A battery-powered digital transmitter may include a headphone plug in communication with any suitable music audio source. For reception, a battery-powered headphone receiver may use embedded fuzzy logic to enhance user code bit detection. Fuzzy logic detection may be used to enhance user code bit detection during decoding of the transmitted audio signal. The wireless digital audio music system provides private listening without interference from other users or wireless devices and without the use of conventional cable connections. 
         [0007]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Some aspects of the present invention are generally shown by way of reference to the accompanying drawings in which: 
           [0009]      FIG. 1  schematically illustrates a wireless digital audio system in accordance with the present invention; 
           [0010]      FIG. 2  is a block diagram of an audio transmitter portion of the wireless digital audio system of FIG.  1 .; 
           [0011]      FIG. 3  is a block diagram of an audio receiver portion of the wireless digital audio system of  FIG. 1 ; and 
           [0012]      FIG. 4  is an exemplary graph showing the utilization of an embedded fuzzy logic coding algorithm according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The following detailed description is the best currently contemplated modes for carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention. 
         [0014]    Referring to  FIGS. 1 through 3 , a wireless digital audio music system  10  may include a battery powered transmitter  20  connected to a portable music audio player or music audio source  80 . The battery powered wireless digital audio music transmitter  20  utilizes an analog to digital converter or ADC  32  and may be connected to the music audio source  80  analog headphone jack  82  using a headphone plug  22 . The battery powered transmitter  20  may have a transmitting antenna  24  that may be omni-directional for transmitting a spread spectrum modulated signal to a receiving antenna  52  of a battery powered headphone receiver  50 . The battery powered receiver  50  may have headphone speakers  75  in headphones  55  for listening to the spread spectrum demodulated and decoded communication signal. In the headphone receiver  50 , fuzzy logic detection may be used to optimize reception of the received user code. The transmitter  20  may digitize the audio signal using ADC  32 . The digitized signal may be processed downstream by an encoder  36 . After digital conversion, the digital signal may be processed by a digital low pass filter. To reduce the effects of channel noise, the battery powered transmitter  20  may use a channel encoder  38 . A modulator  42  modulates the digital signal to be transmitted. For further noise immunity, a spread spectrum DPSK (differential phase shift key) transmitter or module  48 , is utilized. The battery powered transmitter  20  may contain a code generator  44  that may be used to create a unique user code. The unique user code generated is specifically associated with one wireless digital audio system user, and it is the only code recognized by the battery powered headphone receiver  50  operated by a particular user. The radio frequency (RF) spectrum utilized (as taken from the Industrial, Scientific and Medical (ISM) band) may be approximately 2.4 GHz. The power radiated by the transmitter adheres to the ISM standard. 
         [0015]    Particularly, the received spread spectrum signal may be communicated to a 2.4 GHz direct conversion receiver or module  56 . Referring to  FIGS. 1 through 4 , the spread spectrum modulated signal from transmit antenna  24  may be received by receiving antenna  52  and then processed by spread spectrum direct conversion receiver or module  56  with a receiver code generator  60  that contains the same transmitted unique code, in the battery powered receiver  50  headphones. The transmitted signal from antenna  24  may be received by receiving antenna  52  and communicated to a wideband bandpass filter (BPF). The battery powered receiver  50  may utilize embedded fuzzy logic  61  (as graphically depicted in  FIGS. 1 ,  4 ) to optimize the bit detection of the received user code. The down converted output signal of direct conversion receiver or module  56  may be summed by receiver summing element  58  with a receiver code generator  60  signal. The receiver code generator  60  may contain the same unique wireless transmission of a signal code word that was transmitted by audio transmitter  20  specific to a particular user. Other code words from wireless digital audio systems  10  may appear as noise to audio receiver  50 . This may also be true for other device transmitted wireless signals operating in the wireless digital audio spectrum of digital audio system  10 . This code division multiple access (CDMA) may be used to provide each user independent audible enjoyment. The resulting summed digital signal from receiving summary element  58  and direct conversion receiver or module  56  may be processed by a 64-Ary demodulator  62  to demodulate the signal elements modulated in the audio transmitter  20 . A block de-interleaver  64  may then decode the bits of the digital signal encoded in the block interleaver  40 . Following such, a Viterbi decoder  66  may be used to decode the bits encoded by the channel encoder  38  in audio transmitter  20 . A source decoder  68  may further decode the coding applied by encoder  36 . 
         [0016]    Each receiver headphone  50  user may be able to listen (privately) to high fidelity audio music, using any of the audio devices listed previously, without the use of wires, and without interference from any other receiver headphone  50  user, even when operated within a shared space. The fuzzy logic detection technique  61  used in the receiver  50  could provide greater user separation through optimizing code division in the headphone receiver. 
         [0017]    The battery powered transmitter  20  sends the audio music information to the battery powered receiver  50  in digital packet format. These packets may flow to create a digital bit stream rate less than or equal to 1.0 Mbps. 
         [0018]    The user code bits in each packet may be received and detected by a fuzzy logic detection sub-system  61  (as an option) embedded in the headphone receiver  50  to optimize audio receiver performance. For each consecutive packet received, the fuzzy logic detection sub-system  61  may compute a conditional density with respect to the context and fuzziness of the user code vector, i.e., the received code bits in each packet. Fuzziness may describe the ambiguity of the high (1)/low (0 or −1) event in the received user code within the packet. The fuzzy logic detection sub-system  61  may measure the degree to which a high/low bit occurs in the user code vector, which produces a low probability of bit error in the presence of noise. The fuzzy logic detection sub-system  61  may use a set of if-then rules to map the user code bit inputs to validation outputs. These rules may be developed as if-then statements. 
         [0019]    Fuzzy logic detection sub-system  61  in battery-powered headphone receiver  50  utilizes the if-then fuzzy set to map the received user code bits into two values: a low (0 or −1) and a high (1). Thus, as the user code bits are received, the “if” rules map the signal bit energy to the fuzzy set low value to some degree and to the fuzzy set high value to some degree.  FIG. 4  graphically shows that x-value −1 equals the maximum low bit energy representation and x-value 1 equals the maximum high bit energy representation. Due to additive noise, the user code bit energy may have some membership to a low and high as represented in  FIG. 4 . The if-part fuzzy set may determine if each bit in the user code, for every received packet, has a greater membership to a high bit representation or a low bit representation. The more a user code bit energy fits into the high or low representation, the closer its subsethood, i.e., a measure of the membership degree to which a set may be a subset of another set, may be to one. 
         [0020]    The if-then rule parts that make up the fuzzy logic detection sub-system  61  must be followed by a defuzzifying operation. This operation reduces the aforementioned fuzzy set to a bit energy representation (i.e., −1 or 1) that is received by the transmitted packet. Fuzzy logic detection sub-system  61  may be used in battery-powered headphone receiver  50  to enhance overall system performance. 
         [0021]    The next step may process the digital signal to return the signal to analog or base band format for use in powering speaker(s)  75 . A digital-to-analog converter  70  (DAC) may be used to transform the digital signal to an analog audio signal. An analog low pass filter  72  may be used to filter the analog audio music signal to pass a signal in the approximate 20 Hz to 20 kHz frequency range and filter other frequencies. The analog audio music signal may then be processed by a power amplifier  74  that may be optimized for powering headphone speakers  75  to provide a high quality, low distortion audio music for audible enjoyment by a user wearing headphones  55 . A person skilled in the art would appreciate that some of the embodiments described hereinabove are merely illustrative of the general principles of the present invention. Other modifications or variations may be employed that are within the scope of the invention. Thus, by way of example, but not of limitation, alternative configurations may be utilized in accordance with the teachings herein. Accordingly, the drawings and description are illustrative and not meant to be a limitation thereof. 
         [0022]    Moreover, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Thus, it is intended that the invention cover all embodiments and variations thereof as long as such embodiments and variations come within the scope of the appended claims and their equivalents.