Abstract:
A consumer electronic device includes circuitry configured to produce a signal corresponding to a selected one of first, second and third radio frequency channel. The circuitry includes a modulator configured to modulate the video signal such that it falls within a first predetermined frequency range, corresponding to the selected channel. The respective frequency ranges for the first, second and third radio frequency channels are mutually exclusive. Multiple consumer electronic devices are coupled to a combiner which generates a combined signal including the modulated signals from all of the devices. This signal is distributed to a plurality of receivers such that each receiver can receive any of the modulated signals without interference from any of the other modulated signals. The device may also be implemented as a stand-alone device that receives baseband signals, modulates the signals and combines the modulated signals to produce the combined signal.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates generally to consumer electronic devices, and more particularly, to the integration of multiple consumer electronic devices within a radio frequency distribution network.  
         BACKGROUND OF THE INVENTION  
         [0002]    The number of consumer electronic video devices which utilize some form of video display has increased in recent years. For example, it is common to use a television or computer monitor to display a signal from a video cassette recorder (VCR) or a digital video disc (DVD) player. Further, it is also common to modulate a baseband television signal generated by the VCR to form a single channel signal (e.g. a channel  4  signal) and to send the single channel signal from a consumer electronic video device to multiple display devices throughout a home or office.  
           [0003]    Typically, a specific channel on a television receiver, and a corresponding frequency, is utilized to view a video signal from a consumer electronic video device. Conventionally, in the United States, either channel  3  or channel  4  is used to display video signals from a consumer electronic video device. Many, radio frequency distribution devices have been designed with an internal switching mechanism for switching between channels  3  and  4 . Channel  3  is used in markets where channel  4  is active, and channel  4  is used in markets where channel  3  is active to prevent interference between the locally modulated signal and the active broadcast signal.  
           [0004]    [0004]FIG. 1 provides a block circuit diagram of a conventional video distribution signal circuit (a radio frequency converter in this example) within a consumer electronic video device, such as a video cassette recorder. A radio frequency distribution signal (e.g. a baseband television signal) is applied to a terminal  100 , and then is transmitted to a modulator circuit  102 . The modulator circuit  102  converts the video signal to a signal that can be received by a television receiver (not shown). The circuit also includes two carrier generators  104  and  106 . A switch  108  is provided to choose which carrier generator transmits its respective carrier frequency to the modulator circuit  102 . For example, the carrier frequency transmitted by carrier generator  104  may correspond to channel  3 , while the carrier frequency transmitted by carrier generator  106  may correspond to channel  4 . When switch  108  connects modulator circuit  102  to carrier generator  106  (as shown in FIG. 1), carrier generator  106  transmits a respective carrier frequency (i.e. the carrier frequency for channel  4 ) to modulator circuit  102 . In contrast, when switch  108  connects modulator circuit  102  to carrier generator  104 , carrier generator  104  transmits a respective carrier frequency (i.e. the carrier frequency for channel  3 ) to modulator circuit  102 .  
           [0005]    In a typical arrangement, the carrier frequencies produced by carrier generators  104  and  106  shown in FIG. 1 overlap one another and therefore are filtered in order to meet broadcast standards. Accordingly, the circuit includes bandpass filters  112  and  114 . One of the band pass filters functions to filter the signal to an appropriate frequency range for channel  3 , while the second bandpass filter functions to filter the signal to an appropriate frequency range for channel  4 .  
           [0006]    For example, the carrier frequency transmitted by carrier generator  104  may correlate to channel  3 , and the bandpass filter  112  may also correlate to channel  3 . In such a situation, when a user switches to channel  3  (i.e. by remote control of the consumer electronic video device), switch  108  switches such that carrier generator  104  (and not carrier generator  106 ) transmits carrier frequency signals to modulator circuit  102 , and further, switches  110  and  116  (operating in tandem, preferably with switch  108 ) switch such that band pass filter  112  (and not band pass filter  114 ) filters the signal. Conversely, the carrier frequency transmitted by carrier generator  106  may correlate to channel  4 , and the bandpass filter  114  may also correlate to channel  4 . In such a situation, when a user changes the VCR to use channel  4 , switch  108  switches such that carrier generator  106  transmits carrier frequency signals to modulator circuit  102 , and further, switches  110  and  116  switches such that band pass filter  114  filters the signal. In either of the scenarios described above, a modulated signal is produced at terminal  118  for receipt by a television receiver.  
           [0007]    An improvement to the above-described circuit is disclosed in U.S. Pat. No. 4,213,152, due to Kakinuma, and illustrated in FIG. 2 of the present application. As described above with reference to FIG. 1, FIG. 2 illustrates a terminal  100  that receives a radio frequency distribution signal, which is then transmitted to a modulator circuit  102 . The circuit also includes two carrier generators  104  and  106  which are controlled by a switch  108 . As described above, the carrier frequency transmitted by carrier generator  104  may correlate to channel  3 , while the carrier frequency transmitted by carrier generator  106  may correlate to channel  4 .  
           [0008]    The respective carrier frequencies overlap one another, and are filtered in order to comply with broadcast standards. In contrast to the method described with respect to FIG. 1, the simplified configuration illustrated in FIG. 2 includes a first filter  202  that is always activated, and a second filter  204  that may be activated by a switch  208 . Whether or not the second filter  204  is activated depends upon which channel is being utilized (i.e. channel  3  or channel  4 ). Filter  202  eliminates a portion the lower sideband of the channel  3  signal while filter  204  eliminates the same portion the lower sideband of the channel  4  signal.  
           [0009]    The systems described by reference to FIG. 1 and FIG. 2 may utilize a single cable (i.e. a coaxial cable) to transmit a signal from the video distribution device (i.e. a video cassette recorder) to a television receiver. In both examples, one of a pair of channels (i.e. either channel  3  or  4 ) may be used to transmit the signal to the television receiver.  
           [0010]    Current consumer electronic video devices, such as satellite set-top boxes (IRDs) and video cassette recorders (VCRs), support either a channel  3  or a channel  4  radio frequency output to a display device (i.e. a television or a personal computer with a radio frequency input terminal). Attempts have been made to utilize a single coaxial cable to transmit radio frequency signals for two distinct channels (channel  3  and channel  4 ) simultaneously. For example, two satellite set-top boxes have been installed on a single network coaxial cable, with the first of the set-top boxes using a channel  3  output, and the second of the set-top boxes using a channel  4  output. However, such systems have had problems with distortion and interference between the channel  3  signal and the channel  4  signal. A primary reason for this distortion is that the consumer electronic video devices (i.e. IRDs) utilize a radio frequency output that violates the 6 megahertz bandwidth specifications of the National Television System Committee (NTSC). Because of this interference, costly external radio frequency modulators have been added to the distribution system in an attempt to move one of the IRD channels (either channel  3  or  4 ) to a non adjacent channel, which is usually located on the high end of the channel spectrum (e.g., in the UHF spectrum). The addition of external modulation circuitry has achieved only marginal success, and results in significant additional costs.  
           [0011]    Therefore, it would be desirable for a radio frequency distribution network system to provide for two or more channels (each channel carrying a signal from a consumer electronic video device) along a single cable, without interference between the channels, and without the necessity for additional external modulation circuitry.  
         SUMMARY OF THE INVENTION  
         [0012]    A first embodiment of the present invention provides multiple consumer electronic video devices, such as a video cassette recorder, digital video disc player, cable set-top box, satellite set-top box or a gaming unit. Each of the consumer electronic video devices includes filtering and modulation circuitry such that output signals may be provided for any of three or more radio frequency channels. Therefore, each consumer electronic video device may provide an output signal for any of the three or more channels, such as channels  3 ,  4 ,  5 , et cetera. Each of the consumer electronic video devices may include an output port for each of the channels (i.e., a channel  3  output port, a channel  4  output port, and a channel  5  output port). However, in an effort to reduce construction costs and simplify the system design, each of the consumer electronic video devices may provide a single output port for use with any of the channels (i.e., a single output port for use with a channel  3  signal, a channel  4  signal, or a channel  5  signal). Further, each consumer electronic video device includes modulation and filtering circuitry such that each signal falls below the single channel bandwidth set by the broadcast standard. Therefore, the signals from each of the consumer electronic video devices can be combined and concurrently transmitted, along a coaxial cable, for example, to any number of video display devices (e.g., television sets, personal computers, etc). In such an embodiment, because the signals are properly modulated and filtered, no additional modulation equipment is required in order to prevent interference between the channels.  
           [0013]    Although the first embodiment described above specifically refers to consumer electronic video devices (e.g., VCRs, DVD players, etc.) as the signal source, this is simply an exemplary embodiment. The signal source may be provided by any consumer electronic device, such as a consumer audio device (e.g., a compact disc player) or a consumer data device (e.g., a computer, a gaming system, etc). Further, although the first embodiment described above specifically refers to video display devices for receiving a combined output signal, this is simply an exemplary embodiment. The output signal may be received by any consumer electronic device, such as an audio receiver or a data receiving device (e.g., a computer).  
           [0014]    In a second embodiment of the present invention, multiple consumer electronic video devices are provided. Each consumer electronic video device may provide an output signal for any of the four or more channels, such as channels  3 ,  4 ,  5 ,  6 , et cetera. As with the first embodiment, each of the consumer electronic video devices may include an output port for each of the channels (e.g. for channels  3 ,  4 ,  5 , and  6 ) or each device may provide a single output port for use with any of the channels. Further, each consumer electronic video device includes modulation and filtering circuitry such that each signal falls within the single channel bandwidth set by the applicable broadcast standard. Therefore, the signals from each of the consumer electronic video devices can be combined and concurrently transmitted to any number of video display devices. In such an embodiment, because the signals are properly modulated and filtered, no additional modulation equipment is required in order to prevent interference among the four channels.  
           [0015]    Although the second embodiment described above specifically refers to consumer electronic video devices (e.g., VCR) as the signal source, and video display devices for receiving a combined output signal, this is simply an exemplary embodiment. The signal source may be provided by any consumer electronic device, such as a consumer audio device (e.g., a compact disc player) or a consumer data device (e.g., a computer, a gaming system, etc.) and the output signal may be received by any consumer electronic device, such as a audio receiver or a data receiving device (e.g., a computer).  
           [0016]    In a third embodiment of the present invention, multiple consumer electronic video devices (source devices) are provided, as in the previous embodiment. Again, each of the consumer electronic video devices includes filtering and modulation circuitry such that output signals may be provided for any of three or more radio frequency channels. As described above, the signals from each of the consumer electronic video devices can be combined and concurrently transmitted to any number of video display devices. However, in this embodiment the combined output signal may be applied to an input port of one of the consumer electronic video devices (source devices). For example, a signal from a digital video disc player may be combined with the signals from several other consumer electronic video devices (including a video cassette recorder), each with a distinct frequency having a bandwidth of less than the bandwidth of a single channel signal. The combined signal may be sent to numerous video display devices, but may also be sent to the video cassette recorder, one of the source devices. For example, the video cassette recorder may record the data from the digital video disc player. As with the previously described embodiments, because the signals are properly modulated and filtered, no additional modulation equipment is required in order to prevent interference among the four or more channels.  
           [0017]    As with the first and second embodiments, although the third embodiment described above specifically refers to consumer electronic video devices as signal sources, and video display devices for receiving a combined output signal, this is simply an exemplary embodiment. Any consumer electronic device may be used to supply the signal source or to receive an output signal.  
           [0018]    In a fourth embodiment, a device is provided for receiving baseband signals from conventional consumer electronic video devices. These conventional devices may include circuitry for providing a baseband video output signal. The device provided in the fourth embodiment receives baseband signals from the multiple conventional consumer electronic video devices, and then modulates each of the signals so that each signal is contained within its own frequency band with a bandwidth of less than the bandwidth of a single channel signal under the applicable broadcast standard. The modulated signals are then combined and distributed along a single cable (i.e., a coaxial cable) to any number of video display devices.  
           [0019]    Although the fourth embodiment specifically refers to a device for receiving baseband signals from electronic video devices, any type of consumer electronic device may be used to supply signals.  
           [0020]    In a fifth embodiment, notch filters are provided in series with each of the consumer electronic video device transmission circuits. The notch filters are used to filter interference from adjacent radio frequency channels. The filtered signals are then combined in a combiner and transmitted to any number of video display devices similarly to previously described embodiments. The notch filters may be packaged in the individual consumer electronic video devices or in the signal combiner.  
           [0021]    Although the fifth embodiment specifically refers to a notch filters in series with consumer electronic video devices, any consumer electronic device transmission circuit could be provided in series with a notch filter.  
           [0022]    In a sixth embodiment, at least two consumer electronic devices provide source signals (e.g., video signals) that are in adjacent frequency ranges (e.g., channel  3  and channel  4  NTSC television signals). A radio frequency distribution device receives the source signals, and each of the source signals is filtered by a respective notch filter. The filtered signals are then combined in a combiner (preferably included in the radio frequency distribution device). 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    The invention is best understood from the following detailed description when read in connection with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following figures:  
         [0024]    [0024]FIG. 1 is a block circuit diagram illustrating a prior art radio frequency signal distribution system;  
         [0025]    [0025]FIG. 2 is a block circuit diagram illustrating another prior art radio frequency signal distribution system; and  
         [0026]    [0026]FIG. 3 is a block circuit diagram illustrating a radio frequency signal distribution system in accordance with an exemplary embodiment of the present invention.  
         [0027]    [0027]FIG. 4 is a block circuit diagram illustrating a radio frequency signal distribution system in accordance with another exemplary embodiment of the present invention.  
         [0028]    [0028]FIG. 5 is a block circuit diagram illustrating a radio frequency signal distribution system in accordance with yet another exemplary embodiment of the present invention.  
         [0029]    [0029]FIG. 6 is a block circuit diagram illustrating a radio frequency signal distribution device in accordance with an exemplary embodiment of the present invention.  
         [0030]    [0030]FIG. 7 is a block circuit diagram illustrating a radio frequency signal distribution system in accordance with yet another exemplary embodiment of the present invention.  
         [0031]    [0031]FIG. 8 is a block circuit diagram illustrating a radio frequency signal distribution system in accordance with yet another exemplary embodiment of the present invention.  
         [0032]    [0032]FIG. 9 is a graph of frequency versus amplitude which is useful for describing the operation of the embodiments of the invention shown in FIGS. 3 through 8.  
         [0033]    [0033]FIG. 10 is a block circuit diagram illustrating a radio frequency signal distribution system in accordance with yet another exemplary embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]    Although several of the exemplary embodiments of the invention are described in terms of a 6 MHz channel used to transmit signals corresponding to the standard adopted by the National Television Standards Committee (NTSC), it is applicable to other broadcast standards such as PAL, SECAM, QAM, Trellis coded VSB, and HDTV (e.g., the decoded HDTV baseband component could be modulated onto a radio frequency signal).  
         [0035]    [0035]FIG. 3 illustrates a first exemplary embodiment of the present invention. A first consumer electronic device  302 , such as a video cassette recorder, digital video disc player, cable set-top box, satellite set-top box, S-video source (e.g., components Y, C R , C B  may be separated/modulated for use as source signals), gaming unit, audio device (e.g., a compact disc player), a personal video recorder, or a data or voice source device is provided.  
         [0036]    Device  302  includes a modulator  304  for varying a carrier signal in accordance with the modulating signal. Device  302  also includes a first channel output port  305 , a second channel output port  307 , and a third channel output port  309 . Ports  305 ,  307 , and  309  are each for use with a distinct channel. For example, in a video device network system, port  305  provides an output for a channel  3  signal, port  307  provides an output for channel  4  signal, and port  309  provides an output port for a channel  5  signal. Although the embodiment illustrated in FIG. 3 includes an output port ( 305 ,  307 ,  309 ) for each radio frequency channel (e.g., channel  3 , channel  4 , channel  5 ), a single output port may be used for all of the channels.  
         [0037]    Another consumer electronic device  312  is also provided in FIG. 3. Device  312  includes a modulator  314  for varying a carrier signal in accordance with the modulating signal. Device  312  also includes a first channel output port  315 , a second channel output port  317 , and a third channel output port  319 . For example, device  312  may be an audio electronic device (e.g., a compact disc player) and each output port could provide an output audio signal in one of numerous frequency ranges. As with device  302 , device  312  may have a single output port that may be used as an output for signals from any audio channel, as opposed to individual output ports  315 ,  317 , and  319  as illustrated in FIG. 3.  
         [0038]    A third consumer electronic video device  322  is also provided in FIG. 3. Device  322  includes a modulator  324  for varying a carrier signal in accordance with the modulating signal. Device  322  also includes a first channel output port  325 , a second channel output port  327 , and a third channel output port  329 . For example, device  322  may be an data source electronic device (e.g., a personal computer) and each output port could provide an output data signal in one of numerous frequency ranges. As with devices  302  and  312 , device  322  may have a single output port that may be used as an output for signals from data channel, as opposed to individual output ports  325 ,  327 , and  329  as illustrated in FIG. 3.  
         [0039]    Therefore, in an exemplary embodiment, device  302  transmits an output channel  3  video signal through port  305 , device  312  transmits an output audio signal through port  317 , and device  322  transmits an output data signal through port  329 . The signals from ports  305 ,  317 , and  329  are combined in combiner  310 . Combiner  310  may simply be a conventional television signal splitter device having its output terminals configured as input terminals and its input terminal configured as an output terminal. Alternatively, any other conventional signal combination device such as a directional coupler may be used. Combiner  310  may include appropriate filtering circuitry (e.g., VSB filters) and amplification circuitry as is necessary. The combined signal is then transmitted along cable  320 , which may be a coaxial cable. Cable  320  distributes the combined signal to consumer electronic devices  308 ,  318 , and  328 . For example, display device  308  may be tuned to receive the channel  3  signal from device  302 . Device  318  may be tuned to receive the audio signal output from device  312 . If appropriate demodulation circuitry is not included in device  318 , a demodulator  330  may optionally be used to demodulate the modulated audio signal from device  312 . Demodulator  330  may be used, for example, when an audio signal from a CD player modulates an RF signal and the device  318  is an amplifier. Device  328  may be tuned to receive the data signal from device  322 . Because adequate modulation and filtering circuitry are provided in each of the consumer electronic devices  302 ,  312 , and  322 , or in combiner  310 , interference between the channel  3  signal, the audio signal, and the data signal is substantially eliminated.  
         [0040]    [0040]FIG. 4 illustrates a second exemplary embodiment of the present invention. In this embodiment, each consumer electronic device is a video device, however, each device could be any type of consumer electronic device, such as a audio device or a data device. A first consumer electronic video device  402 , such as a video cassette recorder, digital video disc player, cable set-top box, satellite set-top box or a gaming unit, is provided. Device  402  includes a modulator  411  for varying a carrier signal in accordance with the modulating signal. Device  402  also includes a first channel output port  412 , a second channel output port  414 , a third channel output port  416 , and a fourth channel output port  418 . Ports  412 ,  414 ,  416  and  418  are each for use with a distinct channel. For example, port  412  provides an output for channel  3 , port  414  provides an output for channel  4 , port  416  provides an output for channel  5 , and port  418  provides an output for channel  6 . Although the embodiment illustrated in FIG. 4 includes an output port ( 412 ,  414 ,  416  and  418 ) for each radio frequency channel (channel  3 , channel  4 , channel  5  and channel  6 , respectively), a single output port may be used for all of the channels.  
         [0041]    Three additional consumer electronic video devices,  404 ,  406 , and  408 , are also provided in the distribution system illustrated in FIG. 4. Device  404  includes a modulator  421  and four output ports  422 ,  424 ,  426 , and  428 , each for use with a respective channel. For example, port  422  provides an output for channel  3 , port  424  provides an output for channel  4 , port  426  provides an output for channel  5 , and port  428  provides an output for channel  6 . Device  406  includes a modulator  431 , and four output ports  432 ,  434 ,  436 , and  438 , each for use with a respective channel. For example, port  432  provides an output for channel  3 , port  434  provides an output for channel  4 , port  436  provides an output for channel  5 , and port  438  provides an output for channel  6 . Likewise, device  408  includes a modulator  441 , and four output ports  442 ,  444 ,  446 , and  448 , each for use with a respective channel. For example, port  442  provides an output for channel  3 , port  444  provides an output for channel  4 , port  446  provides an output for channel  5 , and port  448  provides an output for channel  6 . As with device  402 , devices  404 ,  406 , and  408  may each include a single output port that may be used to provide output signals from any of the four channels, as opposed to an individual output port being provided for each channel as shown in FIG. 4.  
         [0042]    As shown in FIG. 4, port  412  is used for transmission of a channel  3  signal, port  424  is used for transmission of a channel  4  signal, port  436  is used for transmission of a channel  5  signal, and port  448  is used for transmission of a channel  6  signal. The signals from ports  412 ,  424 ,  436 , and  448  are combined in combiner  410 , and the combined signal is then transmitted along cable  420 , which may be a coaxial cable. Combiner  410  may be a converted four-way television signal splitter having its input port configured as an output port and its output ports configured as input ports. Cable  420  distributes the combined signal to video display devices  450 ,  452 ,  454  and  456 . For example, display device  450  may be tuned to receive the channel  3  signal, display device  452  may be tuned to receive the channel  4  signal, display device  454  may be tuned to receive the channel  5  signal, and display device  456  may be tuned to receive the channel  6  signal. Because adequate modulation and filtering circuitry are provided in each of the consumer electronic video devices  402 ,  404 ,  406 , and  408 , interference between the channel  3 ,  4 ,  5 , and  6  signals is substantially eliminated.  
         [0043]    [0043]FIG. 5 illustrates a third embodiment of the present invention. In this embodiment, each consumer electronic device is a video device, however, each device could be any type of consumer electronic device, such as a audio device or a data device. In FIG. 5, four consumer electronic video devices,  502 ,  504 ,  506 , and  508  are provided. Device  502  includes a modulator  511  and four output ports  512 ,  514 ,  516 , and  518 , each for use with a respective channel as described above. Device  504  includes a modulator  521  and four output ports  522 ,  524 ,  526 , and  528 , each for use with a respective channel. Device  506  includes a modulator  531  and four output ports  532 ,  534 ,  536 , and  538 , each for use with a respective channel. Likewise, device  508  includes a modulator  541  and four output ports  542 ,  544 ,  546 , and  548 , each for use with a respective channel.  
         [0044]    As with the embodiment described by reference to FIG. 4, devices  502 ,  504 ,  506  and  508  each may include a single output port which may be used to transmit a signal for any of the four channels, as opposed to an output port for each channel.  
         [0045]    As shown in FIG. 5, port  512  is used for transmission of a channel  3  signal, port  524  is used for transmission of a channel  4  signal, port  536  is used for transmission of a channel  5  signal, and port  548  is used for transmission of a channel  6  signal. The signals from ports  512 ,  524 ,  536 , and  548  are combined in combiner  510 , and then the combined signal is then transmitted along cable  520 , which may be a coaxial cable. Cable  520  distributes the combined signal to video display devices  550 ,  552 ,  554  and  556 . Display device  550  may be tuned to receive the channel  3  signal, display device  552  may be tuned to receive the channel  4  signal, display device  554  may be tuned to receive the channel  5  signal, and display device  556  may be tuned to receive the channel  6  signal. Because adequate modulation and filtering circuitry are provided in each consumer electronic video device, interference between the channel  3 ,  4 ,  5 , and  6  signals is substantially eliminated.  
         [0046]    Although the embodiment described above includes a single display device for each channel, this is simply an illustration. Therefore, numerous display devices, for example  550 ,  552 , and  554  could all be tuned to receive the channel  3  signal, while display device  556  could be tuned to receive a different signal, for example, the channel  5  signal.  
         [0047]    Further, the combined signal transmitted from combiner  510  does not necessarily need to be transmitted to a video display device. For example, it may be desirable for a given consumer electronic video device to receive the signal from another consumer electronic video device. This may occur, for example, when it is desired to send the output signal from a digital video disc player (a first consumer electronic video device) to a video cassette recorder (a second consumer electronic video device) so that the video cassette recorder may record the output signal. As shown in FIG. 5, combiner  510  transmits an output signal which is split among video display device  550 , video display device  552 , video display device  554 , video display device  556 , and consumer electronic video device  508  (entering through input port  558 ). For example, if output port  512 , of consumer electronic video device  502 , is utilized as a channel  3  output channel, input port  558  of consumer electronic video device  508  could be utilized as a channel  3  input signal. As such, the radio frequency signal distribution system illustrated by reference to FIG. 5 is “bidirectional” in that the signals transmitted to the combiner  510  by the source devices may be transmitted to a video display device, or to a source device.  
         [0048]    Further, one consumer electronic device (e.g., a video display device) may be used to control another consumer electronic device (e.g., a video playback device). Therefore, in the exemplary embodiment shown in FIG. 5, one of the video display devices, such as device  556 , could be used to control device  508  by transmitting a control signal to port  558 . As such, this is another “bidirectional” aspect of the embodiment illustrated in FIG. 5. Further still, device  556  could be used to provide both a video supply signal and a control signal to device  508  via port  558 .  
         [0049]    In some circumstances it may be desirable to distribute radio frequency signals for two or more channels using conventional consumer electronic video devices, along a single cable. This is especially true because of the expense that would be incurred in the replacement of numerous consumer electronic video devices. Therefore, an additional embodiment of the present invention provides a device for receiving output signals from multiple conventional consumer electronic video devices.  
         [0050]    [0050]FIG. 6 illustrates a radio frequency distribution device  600  for receiving multiple signals from conventional consumer electronic devices. In this embodiment, the device  600  receives signals from video devices, however, the device  600  could receive signals from any type of consumer electronic device, such as a audio device or a data device. The signals received by device  600  are the baseband signals. Device  600  includes  4  input ports  602 ,  604 ,  606 , and  608 . This is only an exemplary embodiment, and as such, device  600  could include more or less than four input ports. Each input port may include a respective terminal point  601 ,  603 ,  605 , or  607 . Each input signal is transmitted from its input port to a respective modulator. For example, input port  602  is coupled to a modulator  612 , input port  604  is coupled to a modulator  614 , input port  606  is coupled to a modulator  616 , and input port  608  is coupled to a modulator  618 . Each modulator varies a respectively different carrier signal in accordance with a respective modulating signal received via the corresponding input port. Further, each of the signals is appropriately filtered such that its respective frequency range has a bandwidth of, for example, less than 6 megahertz.  
         [0051]    [0051]FIG. 9 illustrates an exemplary frequency spectrum of modulated and filtered signals (with a bandwidth of less than 6 megahertz) transmitted from multiple consumer electronic video devices, similar to the embodiment illustrated in FIGS. 3, 4,  5  and  6 . The coordinate axes shown in FIG. 9 includes frequency (measured in megahertz) along the x-axis, and amplitude along the y-axis. Four broadcast signals  910 ,  920 ,  930 , and  940  are provided along the x-axis. Each of the signals has a nominal 6 megahertz bandwidth. Signal  910  represents a channel  3  signal, which has a nominal frequency range of 60-66 megahertz. Picture carrier  912  is shown at approximately 61.25 megahertz. Likewise, signals  920 ,  930 , and  940 , represent channels  4 ,  5 , and  6  respectively. As can be seen, channel  4  has a nominal frequency range of 66-72 megahertz, channel  5  has a nominal frequency range of 76-82 megahertz, and channel  6  has a nominal frequency range of 82-88 megahertz. Picture carriers  922 ,  932 , and  942  are shown at their respective frequencies of approximately 67.25 megahertz, 77.25 megahertz, and 83.25 megahertz.  
         [0052]    [0052]FIG. 9 also shows a guard band  902  between the channel  3  signal  910  and the channel  4  signal  920 . Likewise, a guard band  904  is provided between the channel  5  signal  930  and the channel  6  signal  940 . The frequency spectrum (including guard bands) illustrated in FIG. 9 applies to various embodiments of the present invention that concurrently provide a channel  3 , channel  4 , channel  5 , and channel  6  signal.  
         [0053]    The modulators used in the exemplary systems shown in FIGS. 3, 4,  5  and  6 , described above as well as the system shown in FIG. 7, described above, generate signals that conform to the frequency spectra shown in FIG. 9. Thus, each of the generated channel signals is separated from adjacent channel signals by a guard band to prevent interference among the signals.  
         [0054]    Referring again to FIG. 6, the output signals from modulators  612 ,  614 ,  616 , and  618  are combined in combiner  620 . Combiner  620  then transmits an output signal to output port  622 . Output port  622  may include a terminal  621 , as shown in FIG. 6. The output signal from output port  622  can be transmitted to any number of video display devices, or alternatively, to an input port of a consumer electronic video device, as explained above with reference to FIG. 5. For example, a video display device may be tuned to receive a signal at the frequency for a given channel, such as channel  3 ,  4 ,  5 , or  6 .  
         [0055]    [0055]FIG. 7 illustrates an embodiment of the present invention that is very similar to the embodiment described by reference to FIG. 4. In this embodiment, each consumer electronic device is a video device, however, each device could be any type of consumer electronic device, such as a audio device or a data device. Four consumer electronic video devices  702 ,  704 ,  706 , and  708  are provided in FIG. 7. Each device includes a respective modulator ( 711 ,  721 ,  731  and  741 ). Further, each of the consumer electronic video devices transmits a signal to a combiner  710 , and output signals from the combiner  710  are transmitted to one of the video display devices  750 ,  752 ,  754  and  756 . As in the previous embodiments, each of the video display devices may be tuned to receive a frequency of any of the appropriate radio frequency channels (i.e.,  3 ,  4 ,  5  or  6 ). However, in contrast to the embodiment described by reference to FIG. 4, each of the consumer electronic video devices ( 702 ,  704 ,  706  and  708 ) in FIG. 7 includes a single respective output port. For example, device  702  includes a single output port  712  which may be used to transmit a signal with a radio frequency corresponding to any of a number of channels, for example, channels  3 ,  4 ,  5 , and  6 . Devices  704 ,  706 , and  708  each include a respective output port  722 ,  732 , and  742 .  
         [0056]    [0056]FIG. 8 illustrates an additional exemplary embodiment of the present invention. In this embodiment, each consumer electronic device is a video device, however, each device could be any type of consumer electronic device, such as a audio device or a data device. FIG. 8 provides four consumer electronic video devices  802 ,  804 ,  806 , and  808 , each with a respective modulator  811 ,  821 ,  831 , and  841 . As with the embodiment described by reference to FIG. 7, each of the devices  802 ,  804 ,  806 , and  808  shown in FIG. 8 include a single respective output port  812 ,  822 ,  832 , and  842 . Each of the output signals transmitted by a device and through its respective output port is transmitted through one or more notch filters before entering combiner  810 .  
         [0057]    For example, an output signal transmitted by consumer electronic video device  802  passes through output port  812 , and then reaches notch filter  862  and notch filter  864 . In a given circumstance it may be desired to transmit a channel  3  radio frequency signal from consumer electronic video device  802 . In order to ensure that there is an adequate band to protect the signal from interference of adjacent channels, it may be desirable to include a notch filter for at least the higher frequencies of channel  2  and a notch filter for at least the lower frequencies of channel  4  (the two channels adjacent to channel  3 ). Therefore, notch filter  862  may filter interference corresponding to a channel  2  signal, while notch filter  864  may filter interference corresponding to a channel  4  signal. Therefore a channel  3  signal with negligible interference is provided to combiner  310  by device  802  through the use of notch filters  862  and  864 .  
         [0058]    In the embodiment illustrated in FIG. 8, consumer electronic video devices  804 ,  806 , and  808  also include respective notch filters to provide signals substantially free from adjacent channel interference to combiner  810 . For example, it may be desired to transmit a channel  4  radio frequency signal from consumer electronic video device  804 . In order to ensure that there is an adequate band to protect from interference of adjacent channels, it may be desirable to include a notch filter for at least the higher frequencies of channel  3  and a notch filter for at least the lower frequencies of channel  5  (the two channels adjacent to channel  4 ). Therefore, notch filter  863  may filter interference corresponding to a channel  3  signal, while notch filter  865  may filter interference corresponding to a channel  5  signal. Therefore a channel  4  signal with negligible interference is provided to combiner  810  by device  804  through the use of notch filters  863  and  865 .  
         [0059]    Further, it may be desired to transmit a channel  5  radio frequency signal from consumer electronic video device  806 . In order to ensure that there is an adequate band to protect from interference of adjacent channels, it may be desirable to include a notch filter for at least the higher frequencies of channel  4  and a notch filter for at least the lower frequencies of channel  6  (the two channels adjacent to channel  5 ). Therefore, notch filter  866  may filter interference corresponding to a channel  4  signal, while notch filter  868  may filter interference corresponding to a channel  6  signal. Therefore a channel  5  signal with negligible interference is provided to combiner  310  by device  806  through the use of notch filters  866  and  868 . Similarly, it may be desired to transmit a channel  6  radio frequency signal from consumer electronic video device  808 . In order to ensure that there is an adequate band to protect from interference of adjacent channels, it may be desirable to include a notch filter for at least the higher frequencies of channel  5  (the channel adjacent channel  6 ). It is not required to include a notch filter for channel  7  because the frequency spectrum shifts substantially between channel  6  and channel  7 , such that a notch filter would not be required. Notch filter  867  may filter interference corresponding to a channel  5  signal. Therefore a channel  6  signal with negligible interference is provided to combiner  310  by device  808  through the use of notch filter  867 .  
         [0060]    While two notch filters ( 863 ,  865 ) are included in FIG. 8 to provide a channel  5  signal with negligible interference from adjacent channels, both filters may not be required. For example, the channel  5  frequency range is approximately 76-82 megahertz, while the channel  4  frequency range is 66-72 megahertz. Consequently, there is no overlap between the channel  4  and the channels  5  frequency range. Therefore, depending on the output signals provided by the respective modulators, only a notch filter corresponding to the lower frequencies of channel  6  may be used to provide a clean channel  5  signal.  
         [0061]    Therefore, although two notch filters may be illustrated in a particular circuit in FIG. 8, two notch filters may not always be required in a given scenario.  
         [0062]    The notch filters shown in FIG. 8 ( 862 ,  863 ,  864 ,  865 ,  866 ,  867  and  868 ) are shown independent of their respective consumer electronic video devices and independent of combiner  810 , however, this is simply an exemplary embodiment. In this embodiment, each of the notch filters may be a variable notch filter such that the filter could be tuned to a desired frequency. For example, if it is desired to transmit a channel  3  signal using consumer electronic video device  802 , then notch filter  862  may be used to filter out channel  2  interference. However, if it is desired to transmit a channel  6  signal using consumer electronic video device  802 , then notch filter  862  may be used to filter out channel  5  interference. As such, each of the notch filters should be variable in that it could be tuned to filter out a desired frequency. Alternatively, each consumer electronic video device may include multiple, switchable, fixed filters.  
         [0063]    In an embodiment where the notch filters are included in the consumer electronic video device (not shown), it may be desirable to include a variable notch filter, for the reason described above. However, if a given consumer electronic video device includes an output port for each prospective channel, then a pair of notch filters may be included for each channel within the device, and these filters would not need to be variable.  
         [0064]    The embodiment shown in FIG. 8 may also be used to integrate legacy consumer electronic video devices, that do not limit the bandwidth of the modulated signal, into a distribution system according to the subject invention.  
         [0065]    In another embodiment, the notch filters could be included in the combiner (not shown). For example, a combiner could include an input port for each prospective radio frequency channel. As such, the combiner could include an input port for each of channel  3 ,  4 ,  5 , and  6 . Each of the input ports could then include the appropriate fixed notch filters for filtering adjacent channel interference. Therefore, if a combiner included a channel  3  input port, the input port could include a channel  2  and a channel  4  notch filter. Accordingly, in this embodiment, the notch filters included within the combiner would not be required to be variable in their design.  
         [0066]    Referring again to FIG. 8, combiner  810  then transmits the signals from each of the devices  802 ,  804 ,  806 , and  808  concurrently on cable  820 , which may be a coaxial cable. The combined signal is transmitted to numerous video display devices, such as devices  850 ,  852   854 , and  856 . The receivers in each of the video display devices may be tuned to receive a given radio frequency signal, for example, video display device  850  may be tuned to receive a channel  3  signal, while video display device  852  may be tuned to receive a channel  4  signal.  
         [0067]    [0067]FIG. 10 illustrates consumer electronic devices  1002  and  1012 . Each device could be any type of consumer electronic device, such as a video device, audio device or a data device, however, in this embodiment, device  1002  and  1012  are video devices (e.g., VCR, DVD player). Device  1002  includes a modulator  1004 , while device  1012  includes a modulator  1014 . Device  1002  includes two output ports,  1005  and  1007 . Each output port corresponds to a specific channel output, for example, port  1005  corresponds to an NTSC telesvision channel  3  output, and port  1007  corresponds to a channel  4  output. Device  1012  includes a output port  1015  corresponding to a channel  3  output, and output port  1017  corresponding to a channel  4  output.  
         [0068]    Device  1002  transmits a channel  4  signal via output port  1007  to radio frequency distribution device  1020 , and device  1012  transmits a channel  3  signal via output port  1015  to radio frequency distribution device  1020 . Radio frequency distribution device  1020  includes notch filters  1022  and  1024 . Notch filter  1022  filters channel  3  interference from the channel  4  signal. Notch filter  1024  filters channel  4  interference from the channel  3  signal. Combiner  1030 , included in radio frequency distribution device  1020 , receives the filtered channel  4  signal from notch filter  1022 , and the filtered channel  3  signal from notch filter  1024 . Combiner  1030  then transmits a combined signal  1032  (for example, on a coaxial cable) including the channel  3  and channel  4  signals, now mutually exclusive of one another.  
         [0069]    Although illustrated and described above with reference to certain specific embodiments, the present invention is nevertheless not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.