Abstract:
This invention provides a system capable of transmitting two different audio programs in one FM channel signal and generate either one of the audio programs through an FM receiver, such as an FM radio or stereo playback device using pre-recorded media. To accomplish this, one program may be transmitted through the left channel of the FM channel signal and a different program in the right channel of the FM channel signal. A switching circuit may be provided either internally or externally for an FM receiver, headset or speakers that can switch between the “left” and “right” audio programs in the FM channel signal so that a listener may select from either audio programs within one FM channel signal.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Related Applications  
           [0002]    This application is a non-provisional application based on a provisional application having a serial no. 60/303,830, filed Jul. 9, 2001, which is hereby incorporated by reference.  
           [0003]    2. Field of the Invention  
           [0004]    This invention provides a system capable of broadcasting two separate audio programs to one Frequency Modulated (FM) channel and allows a listener to choose between the two separate audio programs from one FM channel.  
           [0005]    3. General Background and State of the Art  
           [0006]    Radio transmission was first developed with Amplitude Modulated (AM) broadcasting, where audio is conveyed from a radio frequency transmitter to a receiver by causing the amplitude of the radio frequency carrier to vary in accordance with an audio waveform. The AM broadcast band ranges from 540 Kilohertz to 1.6 Megahertz. Stations are assigned so that the minimum separation between carrier frequencies of adjacent stations is 10 Kilohertz. The FCC restricts AM broadcast transmissions to 5 Kilohertz so that the transmission does not exceed the 10 Kilohertz allocation and prevent interfering with adjacent stations.  
           [0007]    Limiting AM broadcast transmission to 5 Kilohertz, however, results in relatively low fidelity audio sound. Electrical noise commonly manifests in AM broadcasts as well as rapid and irregular variations of the amplitude in the radio frequency carrier. Moreover, the relatively low 540 Kilohertz to 1.6 Megahertz frequency band for AM signals cannot effectively penetrate buildings and other barriers through which higher frequencies can pass.  
           [0008]    The problems associated with AM broadcast have been largely overcome with the arrival of frequency modulation (FM) broadcasting. In Frequency Modulation, the carrier wave deviates in frequency a small range in accordance with the audio signal. Frequency Modulated radio transmissions are much more immune to noise, primarily because FM demodulators respond to variations in frequency rather than amplitude. As a result, FM transmissions are virtually free of noise as compared with AM transmissions. The FM broadcast band ranges from 88 to 108 Megahertz, and stations are located in 200 Kilohertz intervals. The higher frequency range allows the FM signal to effectively penetrate many types of barriers that an AM signal could not. Moreover, the wider FM bandwidth is what accounts for the higher fidelity of FM transmissions as compared with AM.  
           [0009]    The 200 Kilohertz bandwidth in an FM channel is sufficient to transmit two independent high fidelity channels. For example, FM stereo system is an enhancement of the original FM monaural system, where one audio program is split into two audio signals and transmitted through two channels in one FM radio frequency carrier. The two audio signals may be considered as Left and Right audio signals that are received by a FM radio, and fed to a left and right speakers, respectively. And because the Left and Right audio signals are synchronized for one audio program, the sound from left and right speakers generate a coherent audio program that is understood by a listener. For example, the “Left” channel may contain vocal signal for a song and the “Right” channel may contain background instrumental synchronized with the vocal to generate one coherent song from both the left and right speakers.  
           [0010]    Despite the inferior audio quality of AM broadcasting, many popular audio programs are still broadcast on AM channels. These programs generate significant advertising income for radio stations. Although the prospective markets for these audio programs may be very large, the reception is limited due to the poor penetration of AM audio. Furthermore, in both AM and FM broadcast, the limited availability of radio channels precludes a station from expanding and broadcasting more content in a given day. Therefore, there still is a need for a system capable of broadcasting more audio programs to the limited FM channels.  
         INVENTION SUMMARY  
         [0011]    This invention provides a system capable of broadcasting at least two distinct audio programs to one FM channel so that a listener may choose between the two distinct audio programs within one FM channel. The system utilizes the left and right channels of stereo FM radio to broadcast two separate audio programs, one on the “Left” channel, and a separate program on the “Right” channel. The FM receiver then receives the Left and Right audio signals and outputs the audio signals to left and right speakers that convert the audio signals to sound. For example, an FM radio channel may broadcast a sports game on the “Left” channel, while broadcasting a talk show commenting on the game on the “Right” channel. The FM radio channel may also broadcast a sports talk show in one channel and music that is distinct from the sports talk show on the other channel. The audio programs on the “Left” and “Right” channels may be related in content, however, portions may be different and not intended to be played simultaneously. The “type” of shows that may be broadcast on the Left and Right channels may vary, such as sports games, talk shows, musical, or any other types of audio programs. The system may also rebroadcast audio programs at a later time so that the morning audio program may be rebroadcast in the evening so that listeners that miss the morning program may hear it in the evening. For example, the “Left” channel of a stereo FM channel may re-broadcast an AM radio program that begins at 7:00 a.m. The “Right” channel of the stereo FM signal may broadcast the same audio program at 7:00 p.m.  
           [0012]    The system may also allow a listener to switch the left channel broadcast to be heard on both the left and right speaker of the receiver. Alternatively, the right channel broadcast may be switched to be heard on both the left and right speakers. With certain FM radios with a balance control, the intensity of volume from the left and right speakers may be varied.  
           [0013]    The description above and many other features and attendant advantages of the present invention will become apparent from a consideration of the following detailed description when considered in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0014]    A detailed description with regard to the embodiments in accordance with the present invention will be made with reference to the accompanying drawings.  
         [0015]    [0015]FIG. 1 illustrates a system diagram capable transmitting two separate audio programs that are FM radio modulated.  
         [0016]    [0016]FIG. 2 illustrates two distinct audio programs for broadcast on the left and right channels of an FM stereo broadcast.  
         [0017]    [0017]FIG. 3 illustrates a system diagram that combines two distinct audio programs and modulated on an FM carrier;  
         [0018]    [0018]FIG. 4 a  illustrates a switch in a first position coupling two input terminals to two output terminals.  
         [0019]    [0019]FIG. 4 b  illustrates the switch of FIG. 4 a  in a second position coupling the two input terminals to the two output terminals in a different configuration.  
         [0020]    [0020]FIG. 4 c  illustrates the switch of FIG. 4 a  in a third position coupling the two input terminals to the two output terminals in a different configuration.  
         [0021]    [0021]FIG. 4 d  illustrates the switch of FIG. 4 a  in a fourth position coupling the two input terminals to the two output terminals in a different configuration.  
         [0022]    [0022]FIG. 5 illustrates a switch that sends the output of a left pre-amplifier into the input of a left and a right power amplifier.  
         [0023]    [0023]FIG. 6 illustrates a switch that sends the output of a right pre-amplifier into the input of a left and a right power amplifier.  
         [0024]    [0024]FIG. 7 illustrates a switch that sends the output of a left and a right pre-amplifier into the input of a left and a right power amplifier, respectively. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]    [0025]FIG. 1 illustrates a system where two distinct audio programs are modulated for broadcasting in FM signals to a predetermined FM channel. The distinct signals may include a left audio program  4  and a right audio program  10  that are modulated by an FM radio modulator  14 . The left  4  and right  10  audio programs may be fed into the left  6  and right  8  inputs of the FM radio modulator  14 . A predetermined radio station carrier frequency  2  may also be fed into the FM radio modulator  14 , and the left and right audio programs may be modulated onto the carrier frequency  2 . The modulated left and right signals  4  and  10  may be broadcasted through a transmitter  12  to FM receivers within a certain area. A listener may tune into the predetermined channel and have an option to listen to either the left audio program  4  through the left speaker or the right audio program  10  through the right speaker. By utilizing separate programs on the left and right channels, a single FM carrier can effectively double its radio broadcast time, revenue, and public services respectively, without increasing FM bandwidth.  
         [0026]    [0026]FIG. 2 illustrates two radio programs broadcasting through the left and right channels of an FM stereo transmission. Both the left  20  and right  30  audio programs may include time slots  21  and  31  that define “chunks” of broadcast time in a given day. Sub-programs  25  and  35  may then fill the time slots  21  and  31 , to create the radio program. A first radio sub-program  26  may occupy a time slot  22 , and a second different radio sub-program  34  may occupy the same time slot  32  on the other audio program. The left and right audio programs  20  and  30  may be converted into audio signals  4 ′ and  10 ′ and prepared for FM stereo broadcast.  
         [0027]    Alternatively, a sub-program  33  may occupy a time slot  37  on the audio program  20 , and the same program  33  may occupy a different time slot  39  on the other radio program. This allows a program to be broadcast at different times in the day. For example, a program may be broadcast at 7:00 a.m., and then re-broadcast at 7:00 p.m. This way, the same program may be re-broadcast at a later time to fit into the schedules of other listeners. Further, additional commercials may be added without losing content and increase revenue by broadcasting on a single FM carrier.  
         [0028]    The same program  28  and  28 ′ may be played at the same time slots  24  and  24 ′ on the left and right channels, for example, to inform the listener that the current radio station is a two-channel stereo broadcast where different programs are being played on the left and right stereo channels. Still further, the program  28  and  28 ′ may be played simultaneously on both the left and right channels of an FM stereo transmission.  
         [0029]    [0029]FIG. 3 illustrates a system diagram for modulating and transmitting the left and right audio program signals  4  and  10  to one FM channel. A listener with a conventional monaural FM receiver may hear the monaural audio that includes the left plus the right channel audio. A listener with a stereo receiver may receive the left-channel audio on the left channel speaker(s), and the right channel audio on the right channel speaker(s). The left  4  and right  10  channel audios may be combined  40  to produce a monaural signal (m L (t)+m R (t)), and the difference audio  42  (m L (t)−m R (t)) may be used to modulate  46  a Double Side Band Suppressed Carrier (DSB-SC) signal to form sidebands. The frequency  44  used to DSB-SC modulate the difference signal may be halved  48  to form a pilot tone that may be added  50  to the sum signal and the sidebands to form the composite base band signal m b (t). The pilot tone may provide a reference signal for coherent sub-carrier demodulation in the receiver. The composite frequency modulated signal  52  may be then modulated  56  with the FM channel carrier f c , generated by the frequency channel generator  54 , and transmitted  58  to FM receivers within a certain area.  
         [0030]    The FM stereo transmission may be received by many types of FM receivers known in the art. A stereo FM receiver having a balance control may allow a listener to switch between the left and right audio channels. The balance control in an FM stereo receiver may also allow a user to isolate either a left program or right program by setting the balance to the left or to the right, respectively.  
         [0031]    FIGS.  4 - 7  illustrate receiver switching circuits that may be incorporated into any type of FM stereo receiver such as, but not limited to, a Walkman™, FM receiver component units, car audio receivers, any type of audio device that plays back pre-recorded medium in stereo format; or separate programming for the left and right channel, tape recorders, tape players, CD-Burners, CD-Players, memory chip players such as MP3 and multi-channel digital satellite transmitters and receivers, or any other type of receivers known in the art and developed in the future.  
         [0032]    [0032]FIGS. 4 a  through  4   b  show a switching circuit  82  that include two input terminals  60  and  62 , and two output terminals  78  and  80 . The input terminals  60  and  62  may be communicatively coupled to the output of the “left” and “right” channel pre-amplifiers of an FM stereo receiver. Alternatively, the input terminals  60  and  62  to the switching circuit may be communicatively coupled to a jack that may be inserted into the headphone receptacle of a stereo FM receiver. Additionally, the switching circuit  82  may be directly integrated into headsets of existing FM portable, home base stereo FM receiving system, and Television Stereo transmissions and receivers including High Definition Television Broadcasting transmitters and receivers. The input terminals  60  and  62  may be also directly integrated into the FM stereo receiver and directly coupled to a left and right channel pre-amplifier. The output terminals  78  and  80  may be communicatively coupled to a left and right input of a power amplifier or directly connected to left and right speakers.  
         [0033]    The switching circuit  82  may include a master control  76  to control two internal switches  72  and  74 . The master control may have four settings. FIG. 4 a  shows the master switch  76  in a first setting where the switch  72  may be communicatively coupled to the lead  64  so that the input terminal  60  is coupled to the output terminal  78 . In addition, the switch  74  may be communicatively couple to the lead  70  so that the input terminal  62  is coupled to the output terminal  80 . Accordingly, two separate signals at the input terminals  60  and  62  may be sent to two separate output terminals  78  and  80 , respectively. The first setting of the master switch  76  may allow two independent channels of sound to be played through the “left” and “right” channels of an FM stereo receiver, respectively. The output terminals  78  and  80  may be connected to a left and right channel input of a stereo amplifier and/or left and right speakers.  
         [0034]    [0034]FIG. 4 b  illustrates a second setting where the switches  72  and  74  are communicatively coupled so that the input terminal  60  are coupled to the output terminals  78  and  80 . In this example, one signal at the input terminal  60  may be sent to two separate output terminals  78  and  80 . The configuration in FIG. 4 b  may allow one independent channel of sound to be played through the “left” and “right” channels of an FM stereo receiver. The output terminals  78  and  80 ′ may be connected to a left and right channel input of a stereo amplifier and/or left and right speakers. FIG. 4 c  illustrates a third setting of the control  76  similar to the second setting illustrated in FIG. 4 b,  with the exception that the input from channel  62  is sent to the output terminals  78  and  80 . FIG. 4 d  illustrates a fourth setting where the master switch  76  couples the input terminal signal  60  to the output terminal  80  and input terminal signal  62  to the output terminal  78 , thereby reversing the outputs. The fourth setting may be used for acoustical reasons or enhance the sound for hearing impaired.  
         [0035]    [0035]FIG. 5 illustrates an alternative receiver switching circuit that includes four switches  100 ,  102 ,  104 , and  106 , each occupying an “upper” or “lower” position. The switches  100  and  102  may be bridged  107  to toggle simultaneously, and switches  104  and  106  may be bridged  109  to toggle simultaneously as well. This way, the user may have two control buttons or slide switches to choose from. When switch  100  is in its upper position, the switch  102  is in its upper position as well, and both switches  104  and  106  are in their lower position. These switching positions communicatively couple the input terminal  120  with the output terminals  124  and  126 . In this configuration, one signal at the input terminal  120  may be sent to two separate output terminals  124  and  126 . The configuration in FIG. 5 may allow one independent channel of sound to be played through the “left” and “right” channels of an FM stereo receiver. The output terminals  124  and  126  may be coupled to a left and right channel input of a stereo amplifier and/or left and right speakers. The input terminals  120  and  122  may be communicatively coupled to the output of a “left” and “right” pre-amplifier in an FM stereo receiver.  
         [0036]    [0036]FIG. 6 illustrates the receiver switching circuit in FIG. 5 with the exception that switches  104  and  106  are in their upper positions and the input from channel  122  as opposed to  120  is sent to the output terminals  124  and  126 .  
         [0037]    [0037]FIG. 7 illustrates the switching circuit in FIGS. 5 and 6 where switches  104  and  106  may be in their “upper” or “lower” position and switches  100  and  102  may be in their “lower” position. In this configuration, the input terminal  120  is communicatively coupled with the output terminal  124 , and the input terminal  122  is communicatively coupled to the output terminal  126  so that the two separate signals at the input terminals  120  and  122  may be sent to two separate output terminals  124  and  126 , respectively. The configuration in FIG. 7 may allow two independent channels of sound to be played through the “left” and “right” channels of an FM stereo receiver, respectively. The output terminals  124  and  126  may be coupled to a left and right channel input of a stereo amplifier and/or left and right speakers. The input terminals  120  and  122  may be communicatively coupled to the output of a “left” and “right” preamplifier in an FM stereo receiver.  
         [0038]    The input terminals  120  and  122  to the switching circuits in FIGS.  5 - 7  may be communicatively coupled to a jack that can then be inserted into the headphone receptacle of a stereo FM receiver or playback audio device. Alternatively, the input terminals may be directly integrated into the FM stereo receiver and directly coupled to a “left” and “right” channel pre-amplifier.  
         [0039]    This invention may apply to all types of switching circuits known to one ordinarily skilled in the art, such as, but not limited to, digital switches, analog switches, software switches, integrated circuit switches, with varying designs and configurations, which may include light and Liquid Crystal Diode word/numeric displays of selection options.  
         [0040]    In closing, it is noted that specific illustrative embodiments of the invention have been disclosed hereinabove. However, it is to be understood that the invention is not limited to these specific embodiments. With respect to the claims, it is the applicant&#39;s intention that the claims not be interpreted in accordance with the sixth paragraph of 35 U.S.C. §112 unless the term “means” is used followed by a functional statement.