Abstract:
A video signal distribution system comprises an interface device and video signal input means for receiving TV signals on broadcast channels connected to the interface device. A plurality of video appliances and a plurality of TV sets may be connected to the interface device such that the television sets are arranged to be remote from the plurality of video appliances. A person using the system has a remote control device that may be actuated to emit signals for selecting channels for viewing and to control the video appliances. Each of the television sets includes a repeater arranged to receive the control signals from the remote control device and form corresponding electrical control signals. The interface device receives the electrical control signals corresponding to a selected TV set and directs electrical control signals to a selected one of the plurality of video appliances to provide video signals to the television sets.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation-in-part of U.S. patent application Ser. No. 08/635,727 filed Apr. 22, 1996 for Home Video Signal Distribution System, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to video signal distribution systems. In particular, this invention relates to systems for distributing video signals from video signal sources to selected locations in a home and for controlling the video signal sources from any television set in the home. Still more particularly, this invention relates to systems for distributing throughout a home broadband signals from sources such as antennas or cables and locally created video signals from sources such as VCRs, videodisc players and satellite receivers. 
     Modern consumer electronics brings a wide array of video signal choices to the consumer. Video appliances such as VCRs, satellite receivers., and videodisc players are used to augment CATV or antenna service to a home. These video appliances usually connect to television sets in one of two ways. The most common is for the consumer to route his CATV or antenna signal through the appliance and then on to the TV via coaxial cable. A transfer switch inside the appliance will select either the broadband input or the internal channel 3/4 modulator to be connected to the TV. The other common method is to use the baseband video and audio outputs of the appliance and connect to corresponding inputs on the TV. 
     There are aspects of modern life that are ignored in these schemes. Many homes have more than one video appliance. Connecting more than one video appliance to a TV is not a straightforward matter. Additionally, most homes in the United States have more than one TV. 
     For years a small marketplace of video accessories has existed to distribute either the baseband video/audio or the channel 3 RF from multiple appliances to several TVs. These video accessories typically suffer from two problems. One problem is that the selector boxes are often confusing to use. The consumer must select the video appliance from the switch box, be sure that the video appliance has its ANT/VCR switch in the proper position, and turn the TV to channel 3. The selection of appliance often will be different in the room where the appliances are located. The second problem that switch boxes do not address is the need for control of the appliances at the remote television. There is a secondary market of IR signal repeating devices that will accept IR control signals in one room of a house and transmit them via wires or radio waves to a second device positioned near the appliances. These signals are turned into IR pulses that duplicate the originals, which allows the consumer to start and stop the VCR, or to change satellite channels. 
     Devices exist that address these problems in a unified fashion. For years professional satellite installers have been installing external video modulators to these appliances. These modulators have channel assignments that are programmable by the installer. Correct use of these devices would remove switches entirely from this system, and instead would create new TV channels where there were none. In a typical house, coaxial cable from all TVs is run to a central location. The broadband CATV (antenna) signal is then split to all of the TVs in the house and amplified if needed. The broadband signal is also combined with new channels that contain the video programming from the VCR and other video appliances. Any TV in the house can watch the broadcast channels normally, or watch the VCR by tuning to the VCR channel (or videodisc player, or satellite receiver). A properly installed system preserves the quality of all signals while greatly enhancing the convenience of use. 
     Also available with this type of system are add-on accessories that allow IR control signals to be transmitted along the coax cable that provides the programming. The major disadvantage of this system is the expense. These systems are all custom and professionally installed. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system for distributing video signals in a home in a manner that includes all aspects of a professionally installed video system into a product that is installable and affordable by an average consumer. 
     Accordingly a video signal distribution system according to the invention comprises an interface device and video signal input means for receiving TV signals on broadcast channels connected to the interface device. The system further includes a video appliance connected to the interface device and a television set connected to the interface device. The TV set has means associated therewith for receiving infrared control signals and forming corresponding electrical control signals. The interface device includes means for receiving the electrical control signals and using the electrical control signals to control operation of the video appliance and the video signal input means. The interface device includes an amplifier circuit having its input terminal isolated from its output so that signals that appear at the output of the amplifier are not transmitted to its input. Therefore, the interface device eliminates the need for a switch as used in conventional systems to provide the required isolation between video signal sources. 
     The video signal distribution system according to the invention may further comprise a plurality of TV sets connected to the interface device, and means associated with each of the plurality of TV sets for receiving infrared control signals and forming corresponding electrical control signals. 
     The video signal distribution system according to the invention may further comprise a plurality of video appliances and a plurality of television sets connected to the interface device with the TV sets being remote from the plurality of video appliances. The interface device includes means for receiving the electrical control signals corresponding to a selected TV set and directing electrical control signals to a selected one of the plurality of video appliances to provide video signals to the television sets. 
     An appreciation of the objectives of the present invention and a more complete understanding of its structure and method of operation may be had by studying the following description of the preferred embodiment and by referring to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a video signal distribution system according to the invention; 
     FIG. 2 is a block diagram of an infrared control system that may be used with the video signal distribution system of FIG. 1; 
     FIG. 3 is a block diagram of a video interface device that may be included in FIG. 1; and 
     FIG. 4 is a schematic diagram of circuitry that may be included in the video interface device of FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the present invention comprises an integrated system  10  for distribution of video signals and control of the video appliances in a single device. An interface device  20  routes video and control signals within the system  10 . The interface device  20  may be placed near a video cassette recorder (VCR)  22  and a satellite receiver  24 . The video signal distribution portion of the interface device  20  includes an RF input for connection to a CATV source  26  or an antenna (not shown), and outputs for a local TV set  28  that includes an IR target  30 . The interface device may also be connected to a plurality of remote TV sets  31 - 33  that are typically in other rooms remote from the local TV set  28 , the VCR  22  and the interface device  20 . The number of remote TV sets is merely an example of a typical installation and in no way limits the scope of the invention. 
     Referring to FIGS. 1 and 2, the video signal distribution system includes two sets of video/audio inputs for the video appliances. As shown in FIG. 2, the front of the VCR  22  includes an IR repeater/emitter  23 , and the front of the satellite receiver  24  includes an IR repeater/emitter  25 . Both the VCR  22  and the satellite receiver  24  are connected to the interface device  20  via cables. Connecting all TVs in the house via coaxial cables allows the user to tune to anything on the CATV (or ant) feed, or tune either the VCR or satellite receiver (DSS) channels. 
     The VCR and satellite receiver channels are programmable to allow the user to avoid existing broadcast channels. An IR target  36  is placed adjacent the remote TV set  33 . A standard remote control device  34  is used to direct IR signals to the target  36 . The remote TV set  31  may be tuned to the channel assigned to the VCR  22  for viewing. The IR signals are then transmitted to the VCR  22  to START, STOP, PAUSE, etc. the VCR  22 . 
     By aiming the remote control device  34  at the IR target  36 , the user can control video appliances that are in another room. The only connection between the remote TV set  33  and the interface device  20  is the coaxial cable  39 . 
     FIG. 3 shows components that may be included in the interface device  20  of FIGS. 1 and 2. Referring to FIG. 3, a video interface device  20  includes a modulator module  62  that has a pair of external inputs  64  and  66  for audio signals and an input  68  for video signals. The inputs  64 ,  66  and  68  are suitable for connection to an external device such as a video cassette recorder, video disc player, satellite receiver, CCTV camera, etc. The modulator module  62  includes one or more video modulators that are NTSC compatible. The modulators preferably have 4.5 MHz double sidebands. The modulators preferably are frequency agile such that an installer may select a carrier frequency within either the frequency band of 400 to 600 MHz or 600 to 800 MHz. 
     The modulator module  62  produces an output signal that is input to a passive signal combiner  70 . The passive signal combiner  70  also receives an input from an RF amplifier  72  that receives signals at an input jack  74  from a video signal source such as CATV (not shown) or a VHF/UHF antenna F-connector (not shown). The RF amplifier  72  compensates for splitter/connector losses and provides isolation for the CATV/antenna input  74 . The passive signal combiner  70  combines the signals input thereto and provides a combined output on a single conductive path  75 . 
     The combined signals from the various video signal sources that are input to the modulator module  62  and the RF amplifier  72  are then input to a passive signal splitter  76 . The passive signal splitter  76  provides the combined signals to a pair of output jacks  78  and  80  that are suitable for connection to a TV set (not shown) or to a VCR (not shown). The passive signal splitter  76  also provides the combined signals to a pair of F-connectors  82  and  84 . The combined signals at the outputs  78 ,  80 ,  82  and  84  appear at a maximum of 15.5 dB/mV. 
     Referring to the schematic diagram of FIG. 4, the RF amplifier  72  includes a capacitor  92  connected between the input jack  74  and a junction  93 . The capacitor  92  preferably has a capacitance of about 470 pF. A first resistor  94  is connected between the junction  93  and a transistor  96 . The resistor  94  preferably has a resistance of about 39 Ω. The transistor  96  and associated circuitry forms a common emitter stage  77 . Accordingly, the emitter of the transistor  96  is connected to ground through a resistor  98  that has a resistance of about 10 Ω. 
     A second resistor  100  has a first terminal connected to the junction  93 . An inductor  102  is connected to the other terminal of the resistor  100 . The RF amplifier  72  preferably is formed on a printed circuit board (not shown), and the inductor  102  preferably is formed as a printed inductor such that an inductance of about 22 nH appears in the conductive path between the resistor  100  and a junction  103 . Forming an inductor directly on a printed circuit board is an inexpensive technique for providing a small inductance. A capacitor  104  having a capacitance of about 470 pF is connected between the junction  103  and ground. A conductor  105  connects the junction  103  to a junction  107 , which is connected to ground through a resistor  106  so that the resistor  106  and the capacitor  104  are connected in parallel. The resistor  106  preferably has a resistance of about 270 Ω. 
     A resistor  108  is connected between the junction  107  and a junction  109 . The resistor  108  preferably has a resistance of about 240 Ω. A resistor  110  is connected between the junction  109  and a junction  111 , which is connected to a 5 volt DC supply. The resistor  110  preferably has a resistance of about 470 Ω. The junction  111  is also connected to ground through a capacitor  112 . The capacitor  112  preferably has a capacitance of about 0.1 μF. A 5 volt DC source is connected to the capacitor  112  and to a capacitor  134  that is also grounded. The capacitor  134  preferably has a capacitance of about 0.1 μF. 
     A second transistor  114  is arranged as a common base stage  107 . The base of the transistor  114  is connected to the junction  109  so that the base is connected to the resistor  108 . The base of the transistor  114  is also connected to ground through a by-pass capacitor  116  that has a capacitance of about 470 pF. The emitter of the transistor  114  is connected directly to the collector of the transistor  96 . The collector of the transistor  114  is connected to a junction  117  to which a pair of resistors  118  and  122  are connected. The resistors  118  and  122  preferably have resistances of about 27 and 51 Ω respectively. 
     The resistor  118  is connected between the junction  117  and a junction  119 . An inductor  120  preferably having an inductance of about 560 nH is connected between the junctions  119  and  111 , which is connected to the +5V DC supply and to the resistor  110 . The inductor  120  is thus connected between the resistors  110  and  118 . A resistor  124  has one terminal connected to the junction  119  and the other terminal connected to a first terminal of an inductor  126 . The resistor  124  preferably has a resistance of about 75 Ω. The inductor  126  is preferably a printed inductor having an inductance of about 15 nH. The other terminal of the inductor  126  is connected to the +5V DC supply so that electrical current flows from the supply source through the inductor  126  and then through the resistor  124 . The resistors  118  and  124  combine with the resistor  98  to give a nominal gain of about 15 dB with the circuit loading shown. 
     A third transistor  128  is connected in the circuit in a common collector stage  127 . The base of the transistor  128  is connected to the resistor  122  and its collector connected to the +5V DC supply. The three transistors  96 ,  114  and  128  may be identical 85633 transistors, which are commercially available. The emitter of the transistor  128  is connected to a junction  129 . A resistor  132  having a resistance of about 100 Ω is connected between the emitter of the transistor  128  and ground. A resistor  130  having a resistance of about 33 Ω has a first terminal connected to the junction  129 . The output signal of the RF amplifier  72  is taken across the other terminal of the resistor  130  and ground. 
     The RF amplifier  72  is formed to allow the CATV/ANT output signals and signals output from other video signal sources (video disc player, VCR satellite receiver, CCTV camera, etc.) to be connected to the combiner  70  without a switch being included in the circuit. Prior art techniques for connecting such devices to a TV set include a switch so that no signal from the satellite receiver, for example, is input to the CATFV cables. The RF amplifier  72  has a large reverse loss of about 65 dB, which effectively isolates the CATV/ANT input from other video signal sources. The RF amplifier  72  preferably has a forward gain of about 15 dB. The transistor  96  provides forward gain while the transistor  114  provides isolation (reverse loss) to prevent RF signals from propagating from the output to the input of the RF amplifier  72 . The transistor  128  is connected as a buffer. 
     The interface circuit included in the present invention has significant advantages. Because it includes only the three transistors  96 ,  114  and  128 , the interface circuit is inexpensive, particularly when the performance specifications are considered. The 15 dB forward gain plus the 65 dB reverse loss result in a figure of merit of eighty, which is unusually high for a three transistor circuit. The performance specifications are achieved by the series combination of the common emitter stage  77 , followed by the common base stage  107 , followed by the common collector stage  127 . A typical prior art amplifier having a figure of merit of eighty would include twice the number of transistor stages. The transistor  96  and  114  are in series with respect to DC and operate at 40 mA, which has to be taken from the power supply only once to operate the two transistors  96  and  114 . 
     The common emitter stage provides a uniform impedance of 75  to the input terminal  74 . This impedance is achieved by the matching network of the resistor  100  and inductor  102  connected in parallel with the resistor  94  and the emitter diffusion capacitance of the transistor  96 . The transconductance of the common emitter stage  77  is set at 100 milliMho by selecting the resistor  98  to have a value of about 10 Ω. 
     An out of phase signal is coupled back to the input by the collector-base feedback capacitance and multiplied by the gain of the common emitter stage  77 . By minimizing effects of this parasitic Miller capacitance, the circuit maximizes the gain-bandwidth product. This is done by reducing the voltage gain of the common emitter stage  77  via a low load impedance. The input impedance of the common base stage  107  is the load on the transistor  96  and is about one ohm. The inductor  126  is connected to the collector of the transistor  114 . The inductor  126  increases the impedance of the collector load on the transistor  114  at high frequencies to compensate for parasitic capacitance. The inductor  126  preferably has a value that makes the frequency response of the circuit flat to several hundred MHz. The resistors  118  and  124  provide a combined resistance of about 100 Ω at the collector of the transistor  114 . The signal output from the transistor  114  is at the node  117  and is an amplified replica of the input without the Miller effect. 
     The common emitter configuration of the transistor  96  together with the transistor  114  provides most of the forward gain in the circuit  72 . The common base configuration of the transistor  114  provides most of the reverse loss in the circuit without reducing the forward gain. The common collector configuration of the transistor  128  provides impedance matching to match the circuit  72  to the load, which typically is about 50 Ω. 
     The structures and methods disclosed herein illustrate the principles of the present invention. The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects as exemplary and illustrative rather than restrictive. Therefore, the appended claims rather than the foregoing description define the scope of the invention. All modifications to the embodiments described herein that come within the meaning and range of equivalence of the claims are embraced within the scope of the invention.