Agc system for communications system

Claim 2

In a communications system having a plurality of signal generating locations each for providing signals to one of a plurality of transmission mediums each having at least one amplifier therealong, the signals on each of said plurality of transmission mediums being combined in a single transmission medium having at least one amplifier therealong, an automatic gain control system comprising: first signal generating means coupled to a first one of said plurality of transmission mediums for providing a first pilot signal having a frequency fo; first gain control means connected to the amplifier of said first one of said plurality of transmission mediums for controlling the gain thereof in response to the amplitude of said first pilot signal; second signal generating means coupled to a second one of said plurality of transmission mediums for providing a second pilot signal having a frequency f1 greater than fo by an amount Delta f; second gain control means connected to the amplifier of said second one of said plurality of transmission mediums for controlling the gain thereof in response to the amplitude of said second pilot signal; and third gain control means connected to the amplifier of said single transmission medium for controlling the gain thereof in response to the amplitude of at least one of said first and second pilot signals, said third gain control means having a frequency response less than Delta f whereby beat frequencies between said first and second pilot signals do not deleteriously affect the operation of said third gain control means.

Claim 3

An automatic gain control system as defined in claim 1 wherein said communications system is a community antenna television system, each of said transmission mediums includes coaxial cable conductors connected between amplifier stations having the capability of amplifying signals carried in either direction on said coaxial cable conductors, and said automatic gain control system operates to control the gain of amplifiers for amplifying signals carried in the return direction.

Claim 4

An automatic gain control system as defined in claim 1 wherein a plurality of signal generating means, including said first and second signal generating means, are coupled to respective ones of said plurality of transmission mediums each for generating a pilot signal having a frequency different from any other pilot signal at least by an amount Delta i f.

Claim 5

An automatic gain control system as defined in claim 3 wherein the frequencies of each of said pilot signals is at least the frequency given by the formula fn 1 2fn-fo+ Delta f wherein fn is the frequency of the pilot signal next lower in frequency.

Claim 6

In a community antenna television system for distributing television signals in a first band of frequencies from a central location via a coaxial cable distribution system and having a plurality of remote signal generating locations each for generating signals in a second band of frequencies for transmission along at least a part of said distribution system wherein signals in said second band of frequencies on a plurality of branches of said distribution system are combined in a single branch, an automatic gain control system for controlling the gains of amplifiers for amplifying the signals in said second band of frequencies comprising: a plurality of signal generating means each coupled to a respective one of the branches for generating a pilot signal of a frequency within said second band of frequencies, the frequency of each of said pilot signals being separated from the frequency of each of the other pilot sigNals by a frequency difference of at least Delta f; and a plurality of amplifiers each having automatic gain control means responsive to at least one of said pilot signals for controlling the gain of the amplifier, said amplifiers being connected in respective ones of said branches carrying signals in said second band of frequencies and the gain control means associated with each amplifier in a branch carrying signals combined from a plurality of branches having a frequency response less than Delta f whereby beat frequencies between said pilot signals do not deleteriously affect the operation of the gain control means associated with amplifiers in branches carrying signals combined from a plurality of branches.

Claim 7

In a community antenna television system for distributing television signals in a first band of frequencies from a central location via a coaxial cable distribution system and having a plurality of remote signal generating locations each for generating signals in a second band of frequencies for transmission along at least a part of said distribution system wherein signals in said second band of frequencies on a plurality of branches of said distribution system are combined in a single branch, an automatic gain control system for controlling the gains of amplifiers for amplifying the signals in said second band of frequencies comprising: a plurality of signal generating means each coupled to a respective one of the branches for generating a pilot signal of a frequency within said second band of frequencies, the frequency of each of said pilot signals being separated from the frequency of each of the other pilot sigNals by a frequency difference of at least Delta f; and a plurality of amplifiers each having automatic gain control means responsive to at least one of said pilot signals for controlling the gain of the amplifier, said amplifiers being connected in respective ones of said branches carrying signals in said second band of frequencies and the gain control means associated with each amplifier in a branch carrying signals combined from a plurality of branches having a frequency response less than Delta f whereby beat frequencies between said pilot signals do not deleteriously affect the operation of the gain control means associated with amplifiers in branches carrying signals combined from a plurality of branches.

Claim 8

An automatic gain control system as defined in claim 5 wherein the frequencies of each of said pilot signals is at least the frequency given by the formula fn 1 2fn-fo+ Delta f wherein fn is the frequency of the pilot signal next lower in frequency and fo is the frequency of the lowest frequency pilot signal.