Interactive video distribution systems – Video distribution system with upstream communication – Transmission network
Reexamination Certificate
1999-10-26
2004-08-31
Srivastava, Vivek (Department: 2611)
Interactive video distribution systems
Video distribution system with upstream communication
Transmission network
C725S127000, C725S149000, C330S302000, C330S304000
Reexamination Certificate
active
06785907
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to amplifiers for use on a coaxial cable transmission system, for amplifying both the feed signals and the return signals carried on such system, and to such an amplifier having plug in equalizer and attenuator components for presetting the performance characteristics of the amplifier to a particular location on the cable system and for a predetermined frequency band.
BACKGROUND OF THE INVENTION
It is well known practice to transmit signals in two directions, along a common electrical wire transmitting system, a typical example being a telephone system. Telephone wire transmission systems are well known for transmitting voice transmissions and also for transmitting electronically generated signals from a wide variety of equipment such as security systems, facsimile machines, and a wide variety of computer information for example, coded signals concerning credit transactions, and transferring information to and from computers connected to the telephone wire system. Due to the nature of the telephone wire transmission systems, there are significant restrictions on the speed, and volume, of information which can be transmitted within a given time span. In the past this has not been a significant problem. However, with the ever increasing popularity of the so called “Internet”, the ability to transmit very large volumes of information at high speed in both directions has become critical. The telephone wire transmission system does not readily accommodate itself to the very substantial expansion of the volume of information as well as the increase in speed of transmission that is required to satisfy the growing number of customers requiring Internet services. As a result, Internet servicing companies are seeking alternative means of transmission. Other communication may require the sending of reverse signals along the cable, such signals including eg. metering box and telephone signals.
Telephone wire transmission systems are also subject to intermittent interference from a variety of sources, and are sometimes simply so overloaded that they are incapable of accepting further transmissions.
Coaxial cable transmission networks for distributing cable television services are becoming widely accepted in many cities and towns, and provide excellent services for distributing television signals to television sets of subscribers on the network. Such cable television distribution systems are based on a coaxial wire cable, having a single central conductive core, and a woven sheath of wire or other form of conductive sheath, insulated from the core. Such coaxial cable is capable of transmitting much greater volumes of information at high speed, and with very little interference. In the past such cable systems have been used for one way transmission of television signals from the head end signal source to the consumers television sets. Feed amplifiers are provided at intervals to maintain signal strength, which would otherwise become attenuated, due to the length of the cable system. Such feed amplifiers incorporate equalizers and attenuators for equalizing the signals across the frequency band of the signals.
The existence of wide spread cable television signal networks has lead to the development of their use as a means of connecting consumers to the Internet system. The coaxial cable systems, with feed signal amplifiers located along the cables at spaced intervals, and with their substantial freedom from interference, lend themselves particularly well to the rapid transmission of high volume signals such as are generated by the Internet system. Consequently consumers are increasingly looking to the coaxial cable television networks as a means of connecting their computers to the Internet, so as to avoid the difficulties of connections via the telephone wire systems.
One of the problems encountered in using coaxial cable networks for distribution of Internet signals is that Internet signals travel in two directions, both to and from the consumer. This is unlike television signals, which travel in the feed direction, from the supplier to the consumer. To carry Internet signals, the coaxial cables are required to carry signals in both directions simultaneously. The consumer will be receiving signals from an Internet service provider (ISP), and will be generating return signals, generated from his or her computer, back onto to the Internet. In theory the coaxial cable networks are ideally suited to this type of two-way transmission. In practice however, there are problems which arise from the original design of such cable systems. Since the coaxial cable networks are relatively long, the feed signals on the networks gradually become attenuated and decrease in strength as they pass along the length of the cable. In the case of television feed signals this problem is overcome, as mentioned above, by the use of feed signal amplifiers located in the coaxial cables at spaced intervals. These feed signal amplifiers ensure that all subscribers on any particular cable network will receive signals of adequate strength, so that in spite of the considerable length of any one particular cable, the feed signals will all be substantially of the same signal strength to all households on that cable network.
Such feed signal amplifiers are capable only of amplifying the feed signals fed into the coaxial cable from the head end and equalizing them across the frequency band but cannot amplify return signals, passing in the opposite direction.
When it is attempted to adapt the coaxial cable system for two-way transmission of Internet signals, the return Internet signals are unable to pass through the feed amplifiers already incorporated in the coaxial network. Return signal amplifiers have been used to amplify the return Internet signals. These return signal amplifiers are located alongside the feed amplifiers on the coaxial cable network and pass the return Internet signals around the feed amplifiers, and increase the return Internet signal strength. In this way, the return signals bypass the feed amplifiers, and at the same time their signal strength is maintained at the desired level so that it can be fed back to the Internet server. Other communication may require the sending of reverse signals along the cable, such signals including eg. metering box and telephone signals.
The problem of signal strength is aggravated by the attenuation of signal strength. Attenuation varies, and is greater in the higher range of frequencies, and is lower in the lower range of frequencies. The feed amplifiers in use on cable systems are already designed to overcome these problems, and equalise the signal strength over the entire frequency band of the feed television signals. However, the adaptation of an existing cable network to accept two-way transmission of signals such as Internet signals, requires both that the return amplifiers with suitable equalizers be installed on the already existing cable network, and further that the existing feed amplifiers shall be modified so as to equalize all signals, both television and Internet, travelling in the feed directions.
Feed amplifiers for maintaining signal strength of the feed signals should be modified so as to amplify both the Internet and television signals over the entire frequency range of the signals and to equalize these signals back up to a uniform level of signal strength, across the entire range of frequency of both Internet and television signals. However, the signal strength of the signals at any given location on an existing cable network can only be determined by actually measuring the signals at that location. This signal strength will vary from one location to another. At present, the feed amplifiers are produced as a standard item, however, several such feed amplifiers are re . . . which have performance characteristics which vary from one cable location to another.
Typically, the Internet feed signals are placed within this frequency range of from about 50 to 860 megahertz, ie the usual bandwith of television signal
Dan Viorel nil
Sandaluk Anthony J.
Brown Reuben
Cableserv Electronics, LTD
Ohlandt Greeley Ruggiero & Perle
Srivastava Vivek
LandOfFree
Amplifier and equalizer for two way cable transmission does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Amplifier and equalizer for two way cable transmission, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Amplifier and equalizer for two way cable transmission will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3362168